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1.	Li, Qiang, et al. (author) Microbial Necromass, Lignin, and Glycoproteins for Determining and Optimizing Blue Carbon Formation 2024 In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 58, s. 468-479 Journal article (peer-reviewed)abstract Coastal wetlands contribute to the mitigation of climate change through the sequestration of “blue carbon”. Microbial necromass, lignin, and glycoproteins (i.e., glomalin-related soil proteins (GRSP)), as important components of soil organic carbon (SOC), are sensitive to environmental change. However, their contributions to blue carbon formation and the underlying factors remain largely unresolved. To address this paucity of knowledge, we investigated their contributions to blue carbon formation along a salinity gradient in coastal marshes. Our results revealed decreasing contributions of microbial necromass and lignin to blue carbon as the salinity increased, while GRSP showed an opposite trend. Using random forest models, we showed that their contributions to SOC were dependent on microbial biomass and resource stoichiometry. In N-limited saline soils, contributions of microbial necromass to SOC decreased due to increased N-acquisition enzyme activity. Decreases in lignin contributions were linked to reduced mineral protection offered by short-range-ordered Fe (FeSRO). Partial least-squares path modeling (PLS-PM) further indicated that GRSP could increase microbial necromass and lignin formation by enhancing mineral protection. Our findings have implications for improving the accumulation of refractory and mineral-bound organic matter in coastal wetlands, considering the current scenario of heightened nutrient discharge and sea-level rise.
2.	Liu, Linan, et al. (author) Silicon Effects on Biomass Carbon and Phytolith-Occluded Carbon in Grasslands Under High-Salinity Conditions 2020 In: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 11, s. 1-13 Journal article (peer-reviewed)abstract Changes in climate and land use are causing grasslands to suffer increasingly fromabiotic stresses, including soil salinization. Silicon (Si) amendment has been frequentlyproposed to improve plant resistance to multiple biotic and abiotic stresses and increaseecosystem productivity while controlling the biogeochemical carbon (C) cycle. However,the effects of Si on plant C distribution and accumulation in salt-suffering grasslandsare still unclear. In this study, we investigated how salt ions affected major elementalcomposition in plants and whether Si enhanced biomass C accumulation in grasslandspecies in situ. In samples from the margins of salt lakes, our results showed that thediffering distance away from the shore resulted in distinctive phytocoenosis, includinghalophytes and moderately salt-tolerant grasses, which are closely related to changingsoil properties. Different salinity (NaC/KC, ranging from 0.02 to 11.8) in plants causednegative effects on plant C content that decreased from 53.9 to 29.2% with theincrease in salinity. Plant Si storage [0.02–2.29 g Si m?2 dry weight (dw)] and plantSi content (0.53 to 2.58%) were positively correlated with bioavailable Si in soils(ranging from 94.4 to 192 mg kg?1). Although C contents in plants and phytoliths werenegatively correlated with plant Si content, biomass C accumulation (1.90–83.5 g Cm?2 dw) increased due to the increase of Si storage in plants. Plant phytolith-occludedcarbon (PhytOC) increased from 0.07 to 0.28h of dry mass with the increase of Sicontent in moderately salt-tolerant grasses. This study demonstrates the potential ofSi in mediating plant salinity and C assimilation, providing a reference for potentialmanipulation of long-term C sequestration via PhytOC production and biomass Caccumulation in Si-accumulator dominated grasslands.
3.	Berger, Tobias, et al. (author) Fluorine geochemistry of Quaternary deposits in a nemo-boreal catchment with elevated dissolved fluoride in surface waters and groundwater Other publication (other academic/artistic)
4.	Berger, Tobias, et al. (author) Fluorine geochemistry of quaternary deposits in a nemo-boreal catchment with elevated dissolved fluoride in surface waters and groundwater 2016 In: Journal of Geochemical Exploration. - : Elsevier BV. - 0375-6742 .- 1879-1689. ; 170, s. 148-156 Journal article (peer-reviewed)abstract This study focuses on fluorine (F) concentrations and solid-phase speciation in Quaternary deposits, including till, sorted sediments (gravel, sand, clay/silt) and organic-rich soil types, in an area in southeast Sweden underlain by 1.8 Ga granites and quartz monzodiorites with moderate F concentrations (0.11-0.13 wt%) and an outcrop (5 km in diameter) of 1.45 Ga granite (the Gotemar granite) with high to very high F concentrations (0.38-0.54 wt%). Eighteen <1 to 5 m thick profiles were sampled both upon and in the vicinity of the Gotemar granite. The F concentrations in the Quaternary deposits were considerably lower than in the underlying fresh bedrock, with the overall highest concentrations in glacial clay having values up to 660 ppm. A contributing factor to the low F concentrations in the till, as compared to the fresh rock, is release and leaching of fluoride (F-) during alteration of biotite and amphiboles to secondary minerals. Sequential chemical extractions showed that the F in the Quaternary deposits exists mainly in the residual fraction, and also to a substantial extent in phases extractable with hydroxylamine hydrochloride in the till and in phases extractable with Na pyrophosphate in the organic-rich soil types. These features indicate that after release via alteration of primary minerals, F- has to a significant extent been scavenged by Fe/Al (and perhaps Mn) oxyhydroxides in the till and by labile organic matter in the organic soil types. The high F- concentrations previously reported for stream waters and regolith groundwaters in the area are due to weathering and leaching of the Quaternary deposits and discharge of fluoride-rich waters from underlying bedrock fractures. (C) 2016 Elsevier B.V. All rights reserved.
5.	Christel, Stephan, et al. (author) Comparison of Boreal Acid Sulfate Soil Microbial Communities in Oxidative and Reductive Environments 2019 In: Research in Microbiology. - : Elsevier. - 0923-2508 .- 1769-7123. ; 170:6-7, s. 288-295 Journal article (peer-reviewed)abstract Due to land uplift after the last ice age, previously stable Baltic Sea sulfidic sediments are becoming dry land. When these sediments are drained, the sulfide minerals are exposed to air and can release large amounts of metals and acid into the environment. This can cause severe ecological damage such as fish kills in rivers feeding the northern Baltic Sea. In this study, five sites were investigated for the occurrence of acid sulfate soils and their geochemistry and microbiology was identified. The pH and soil chemistry identified three of the areas as having classical acid sulfate soil characteristics and culture independent identification of 16S rRNA genes identified populations related to acidophilic bacteria capable of catalyzing sulfidic mineral dissolution, including species likely adapted to low temperature. These results were compared to an acid sulfate soil area that had been flooded for ten years and showed that the previously oxidized sulfidic materials had an increased pH compared to the unremediated oxidizied layers. In addition, the microbiology of the flooded soil had changed such that alkalinity producing ferric and sulfate reducing reactions had likely occurred. This suggested that flooding of acid sulfate soils mitigates their environmental impact.
6.	Ghahfarokhi, Sina, et al. (author) Contamination of Kristianstad biosphere reservoir by metal bound sediments 2019 Conference paper (peer-reviewed)
7.	Ghahfarokhi, Sina, et al. (author) Contamination of Kristianstad biosphere reservoir by metal bound sediments 2019 Conference paper (other academic/artistic)
8.	Ghahfarokhi, Sina, et al. (author) Wetlands under influence of acid sulfate soils : case study: Southern Sweden, Kristianstad, Norra Lingenäset 2018 Conference paper (peer-reviewed)abstract In recent years, wetlands have drawn scientific attention due to their environmental and economic importance. Preliminary studies show that wetlands in southern Sweden in the vicinity of Kristianstad may be contaminated by iron and aluminium (and possible other metals). Iron precipitates has led to the loss of flora and fauna within the protected natural wetland “Norra Lingenäset” over the last decade. The source of iron is the focus of our investigations, and it is possibly associated with drained acid sulphate soils (ASS) in the north of the wetland. The drained water (varying pH 3-8) from the nearby crop land is pumped to the Norra Lingenäset wetland. Therefore, the interrelation and correlation among the ASS (source of iron contamination) and the wetland are of interest. Our primary results shows 5-70 mg/L of iron in drained water from the ASS and 50-150 mg/g of iron in the accumulated sediments in the draining ditch. Hence, the conditions and state of the cropped ASS regarding iron species and concentrations will be studied. The results from this stage will enable us to design an iron pool for the Kristianstad case study. Understanding metal transportation, speciation and depositions will aid Kristianstad crop lands and wetland managers to provide efficient and effective management plans.
9.	Ghahfarokhi, Sina, et al. (author) Wetlands under influence of acid sulfate soils : case study: Southern Sweden, Kristianstad, Norra Lingenäset 2018 Conference paper (other academic/artistic)abstract In recent years, wetlands have drawn scientific attention due to their environmental and economic importance. Preliminary studies show that wetlands in southern Sweden in the vicinity of Kristianstad may be contaminated by iron and aluminium (and possible other metals). Iron precipitates has led to the loss of flora and fauna within the protected natural wetland “Norra Lingenäset” over the last decade. The source of iron is the focus of our investigations, and it is possibly associated with drained acid sulphate soils (ASS) in the north of the wetland. The drained water (varying pH 3-8) from the nearby crop land is pumped to the Norra Lingenäset wetland. Therefore, the interrelation and correlation among the ASS (source of iron contamination) and the wetland are of interest. Our primary results shows 5-70 mg/L of iron in drained water from the ASS and 50-150 mg/g of iron in the accumulated sediments in the draining ditch. Hence, the conditions and state of the cropped ASS regarding iron species and concentrations will be studied. The results from this stage will enable us to design an iron pool for the Kristianstad case study. Understanding metal transportation, speciation and depositions will aid Kristianstad crop lands and wetland managers to provide efficient and effective management plans.
10.	Han, Guilin, et al. (author) Carbon-nitrogen isotope coupling of soil organic matter in a karst region under land use change, Southwest China 2020 In: Agriculture, Ecosystems & Environment. - : Elsevier. - 0167-8809 .- 1873-2305. ; 301, s. 1-11 Journal article (peer-reviewed)abstract The soil stable carbon (C) and nitrogen (N) isotopes are widely used to indicate C3/C4 vegetation history, N sources and transformation processes, respectively. However, land use change, particularly converting forest into farm land, alters soil organic matter (SOM) sources and processes in soils, resulting in a hard understanding of soil C and N fate. In the present study, soil organic carbon (SOC) and soil organic nitrogen (SON) contents, and their stable isotope compositions (δ13C and δ15N) were determined in the five soil profiles under land use change (i.e., conversion of native forest land into shrub land, grass land, maize field, and paddy land) in Lobo county, Guizhou province, Southwest China. A coupling of 13C and 15N isotope in SOM under land use change was verified whether it could provide more accurate indications of sources and transformation processes.The SOC and SON contents of native forest land at the 0∼20 cm depth were significantly larger than these under other transformed lands. The SOC and SON contents decreased exponentially with increasing soil depth under all land use types, and showed opposite trends with soil pH. The C/N ratios of SOM in the soils under undisturbed native forest decreased from 10 to 7 with increasing soil depth, while an irregular fluctuation along soil profile was shown in other transformed lands. Similarly to the most study in the soils under C3 forest, the δ13C and δ15N values of SOM in the soils under native forest at the 0∼50 cm depth increased with increasing soil depth, with the range of −27.7‰∼−25.7‰ and 6.5‰∼10.0‰, respectively. While decreasing trends of them in the soils below 50 cm depth were attributed to the mixing of 13C and 15N-depleted organic matters from bedrocks. However, the δ13C and δ15N values of SOM along the soil profiles under other transformed lands were intensively irregularly fluctuated between −29.1‰ and −19.0‰, 1.2‰ and 7.9‰, respectively. The single δ13C and δ15N signals in the soil profiles of transformed lands indeed revealed the alterations of historical C3/C4 composition and N transformation processes after land use change, but these indications were not specific. The result of the coupling of 13C and 15N isotope under native forest land reveals a positive relationship between them, which associated with full plant-absorption against 15N-depleted inorganic nitrogen derived from SOM mineralization. This study suggests that the coupling of CN isotope fractionation more likely occurs in the C3 forest ecosystem with high N utilization efficiency. However, the replacement of native forest by farm land or grass land will reduce soil N utilization efficiency.
11.	Hao, Qian, et al. (author) Holocene carbon accumulation in lakes of the current east Asian monsoonal margin: Implications under a changing climate 2020 In: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 737, s. 1-13 Journal article (peer-reviewed)abstract Carbon (C) present in lake sediments is an important global sink for CO2; however, an in-depth understanding of the impact of climate variability and the associated changes in vegetation on sediment C dynamics is still lacking. A total of 13 lakes were studied to quantify the influence of climate and vegetation on the reconstructed Holocene C accumulation rate (CAR) in lake sediments of the modern East Asian monsoonal margin. The corresponding paleoclimate information was assessed, including the temperature (30–90°N in the Northern Hemisphere) and precipitation (indicated by the δ18O of the Sanbao, Dongge, and Hulu caves). The Holocene vegetation conditions were inferred by pollen records, including arboreal pollen/non-arboreal pollen and pollen percentages. The results showed that the peak CAR occurred during the mid-Holocene, coinciding with the strongest period of the East Asian summer monsoon and expansion of forests. Lakes in the temperate steppe (TS) regions had a mean CAR of 13.41 ± 0.88 g C m−2 yr−1, which was significantly greater than the CARs of temperate desert (TD) and highland meadow/steppe (HMS; 6.76 ± 0.29 and 7.39 ± 0.73 g C m−2 yr−1, respectively). The major influencing factor for the TS sub-region was vegetation dynamics, especially the proportion of arboreal vegetation, while temperature and vegetation coverage were more important for the HMS. These findings indicate that C accumulation in lake sediments is linked with climate and vegetation changes over long timescales; however, there was notable spatial heterogeneity in the CARs, such as opposing temporal changes and different major influencing factors among the three sub-regions during the mid-Holocene. Aridification and forest loss would decrease C storage. However, prediction of C accumulation remains difficult because of the spatial heterogeneity in CARs and the interaction between the CAR and various factors under future climate change conditions.
12.	Hao, Qian, et al. (author) Organic blue carbon sequestration in vegetated coastal wetlands: Processes and influencing factors 2024 In: Earth-Science Reviews. - 0012-8252 .- 1872-6828. ; 255, s. 104853-104853 Journal article (peer-reviewed)abstract Coastal wetlands play a vital role in carbon (C) sequestration, named ‘blue carbon’. The review aims to disentangle the processes and influencing factors, including elevated atmospheric CO2, global climate warming, sea level rise and anthropogenic activities. Firstly, we provided an overview of C processes, including input, output, and deposition, in coastal wetlands. We then summarized the impacts of different factors on C processes by modifying soil physicochemical properties, plant growth, vegetation type, and microbial community composition. Vegetation composition was a major contributor to C inputs, and C outputs was mainly controlled by microbial decomposition. Increased atmospheric CO2 concentration and associated climate warming often enhanced vegetation growth, while climate warming also promoted soil C decomposition. As a result, C storage could increase under mild warming conditions in the short-term, but decrease in the long-term as the severity of warming intensifies. Elevated salinity, caused by sea level rise, can be harmful to plant growth and inhibit organic C decomposition because of the reduced biomass and the weakened metabolic capacity of microorganisms. Most of human activities, such as reclamation, can lead to less C input and more C output, resulting in decreased C storage in coastal wetlands. Additionally, we also illustrate various coastal wetland restoration methods aimed at enhancing C sequestration, including legal frameworks, scientific theories, vegetation management, hydrological restoration, and other relevant constructions. Vegetation management could benefit plant growth and enhance C input effectively, and hydrological restoration can maintain the harmonious development of coastal wetland ecosystems. Other constructions, including breakwater, spillway, and dredged material, could protect coastal wetlands, especially facing sea level rise. This review offers valuable theoretical support and scientific references for the sustainable development and management of coastal wetlands in a changing climate.
13.	Hao, Qian, et al. (author) Silicon Affects Plant Stoichiometry and Accumulation of C, N, and P in Grasslands 2020 In: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 11, s. 1-10 Journal article (peer-reviewed)abstract Silicon (Si) plays an important role in improving soil nutrient availability and plant carbon (C) accumulation and may therefore impact the biogeochemical cycles of C, nitrogen (N), and phosphorus (P) in terrestrial ecosystems profoundly. However, research on this process in grassland ecosystems is scarce, despite the fact that these ecosystems are one of the most significant accumulators of biogenic Si (BSi). In this study, we collected the aboveground parts of four widespread grasses and soil profile samples in northern China and assessed the correlations between Si concentrations and stoichiometry and accumulation of C, N, and P in grasses at the landscape scale. Our results showed that Si concentrations in plants were significantly negatively correlated (p< 0.01) with associated C concentrations. There was no significant correlation between Si and N concentrations. It is worth noting that since the Si concentration increased, the P concentration increased from less than 0.10% to more than 0.20% and therefore C:P and N:P ratios decreased concomitantly. Besides, the soil noncrystalline Si played more important role in C, N, and P accumulation than other environmental factors (e.g., MAT, MAP, and altitude). These findings indicate that Si may facilitate grasses in adjusting the utilization of nutrients (C, N, and P) and may particularly alleviate P deficiency in grasslands. We conclude that Si positively alters the concentrations and accumulation of C, N, and P likely resulting in the variation of ecological stoichiometry in both vegetation and litter decomposition in soils. This study further suggests that the physiological function of Si is an important but overlooked factor in influencing biogeochemical cycles of C and P in grassland ecosystems.
14.	Hao, Qian, et al. (author) Soil silicon fractions along karst hillslopes of southwestern China 2022 In: Journal of Soils and Sediments. - : Springer Nature. - 1439-0108 .- 1614-7480. ; 22, s. 1121-1134 Journal article (peer-reviewed)abstract Purpose The karst region in southwestern China is undergoing soil erosion and rocky desertification. The different silicon (Si) fractions along the hillslopes in this mountainous region could benefit plant growth and alleviate the ecological deterioration. However, extensive distribution of carbonate rocks may lead to limited plant available Si. The mountainous terrain in karst region also leads to more Si output, which seriously affects the biogeochemical cycle of Si in this area. Yet, the soil Si fractions in the karst region have not been fully evaluated. Methods Soil profiles and their corresponding plants were sampled from two typical karst mountains in Guizhou, China. The different fractions of non-crystalline Si in soil, accounting for the most important pool for Si availability to plants, were analyzed by the improved sequential chemical extraction and Si concentrations in plants grown in this region were also measured. Results The concentration and storage of non-crystalline Si were higher at lower slopes (storage was 2.44, 2.73, and 3.25 kg center dot m(-2) for upper, middle, and lower slopes, respectively) than other slope positions. Grasses dominated at lower slopes and contained significantly higher Si (mean +/- SD: 14.42 +/- 6.63 mg center dot g(-1)) than trees and shrubs (1.94 +/- 1.78 and 1.29 +/- 1.00 mg center dot g(-1), respectively), which were primarily distributed on upper slopes. However, Si concentrations of the same plant species in different slope positions had no significant correlation with soil acid Na acetate-Si, the Si regarded as directly available for plants. Conclusions This study suggests that plant species and soil properties have a significant impact on the soil Si distribution of hillslopes in karst region. Soil erosion may decrease non-crystalline Si concentrations in soils and impair Si uptake in grasses, which need to be considered in ecosystem management in this region.
15.	Hao, Qian, et al. (author) Vegetation Determines Lake Sediment Carbon Accumulation during Holocene in the Forest-Steppe Ecotone in Northern China 2021 In: Forests. - : MDPI. - 1999-4907. ; 12:6 Journal article (peer-reviewed)abstract To understand the past carbon accumulation of forest-steppe ecotone and to identify the main drivers of the long-term carbon dynamics, we selected Huangqihai Lake and analyzed the sediment records. We measured the organic carbon content (TOC; %) of sedimentary samples and quantified the carbon accumulation rate (CAR; g C m(-2) yr(-1)). Furthermore, the climate, soil erosion, and vegetation development of the past 6800 years were reconstructed using physicochemical parameters and pollen records. Human activities were also obtained from a 2200-year history record. Our results showed that the CAR was high during 5800 similar to 4100 cal yr BP (40 similar to 60 g C m(-2) yr(-1)), which is mainly attributed to the high sediment accumulation rate (SAR) during this period. Pearson's correlation, redundancy analysis and hierarchical variation partitioning analyses suggested that the CAR was influenced by the SAR and TOC, while vegetation dynamics (broadleaved tree percentage and vegetation coverage) and local soil erosion were the main drivers of the TOC and SAR. Especially when the vegetation was dominated by broadleaved forests, the CAR was significantly high due to the high gross primary productivity and carbon density of forest compared with steppe. Our study highlights the direct influence of local vegetation and soil erosion on the CAR, whereas climate might influence indirectly by changing local vegetation and soil conditions. Moreover, our results showed that human activities had positive influences on the carbon accumulation dynamics in this region since 2200 cal yr BP by influencing the SAR.
16.	Ketzer, João Marcelo, et al. (author) Discovery of a major seafloor methane release site in Europe : The Landsort deep, Baltic Sea. 2024 In: EGU General Assembly 2024. - : European Geosciences Union (EGU). Conference paper (peer-reviewed)abstract A recently acquired multidisciplinary dataset comprising acoustic surveys (high-resolution sub- bottom profiles, multi-beam bathymetry, and broad band mid-water echo sounder), geochemistry (gas chemical and isotopic composition, porewater chemistry), and sedimentology (core lithology and X-ray CT) in the area of the Landsort deep (450 m of depth), south of Stockholm Archipelago, revealed the existence of an extensive (20 km2) region of the seafloor where massive gas release is occurring in the form of multiple bubble streams. This new discovery represents a major seafloor methane release site in Europe and is comparable in area to other large sites worldwide such as the ones in Svalbard and in the South Atlantic Ocean associated with gas hydrate provinces. The gas is formed mostly by methane of microbial origin. Surprisingly, bubbles rise 100’s of meters above the seafloor and reach surface waters above the halocline/oxycline at around 80 m of depth. Some bubbles appear to reach the sea-air interface and their potential methane contribution to the atmosphere is under investigation. Another surprising observation is the absence of major seafloor features like pockmarks in the gas release area. The reasons for the seafloor methane release in the Landsort deep are still not entirely clear, but our preliminary acoustic and sedimentological data suggest that bottom currents may have acted to facilitate the accumulation of organic-rich sediments in a thick drift deposit during the Holocene and the modern warm period (latest 100 years). Our data further suggest that the high sedimentation rate in the drift deposit continuously supplies fresh organic matter that is quickly buried below a thin sulphate reduction zone, fueling vigorous methanogenesis and abundant methane formation. Similar methane release sites might be discovered in other known large drift deposits in the Baltic Sea.
17.	Li, Zichuan, et al. (author) Impacts of silicon on biogeochemical cycles of carbon and nutrients in croplands 2018 In: Journal of Integrative Agriculture. - : Elsevier. - 2095-3119. ; 17:10, s. 2182-2195 Research review (peer-reviewed)abstract Crop harvesting and residue removal from croplands often result in imbalanced biogeochemical cycles of carbon and nutrients in croplands, putting forward an austere challenge to sustainable agricultural production. As a beneficial element, silicon(Si) has multiple eco-physiological functions, which could help crops to acclimatize their unfavorable habitats. Although many studies have reported that the application of Si can alleviate multiple abiotic and biotic stresses and increase biomass accumulation, the effects of Si on carbon immobilization and nutrients uptake into plants in croplands have not yet been explored. This review focused on Si-associated regulation of plant carbon accumulation, lignin biosynthesis, and nutrients uptake, which are important for biogeochemical cycles of carbon and nutrients in croplands. The tradeoff analysis the supply of bioavailable Si can enhance plant net photosynthetic rate and biomass carbon production (especially root biomass input to soil organic carbon pool), but reduce shoot lignin biosynthesis. Besides, the application of Si could improve uptake of most nutrients under deficient conditions, but restricts excess uptake when they are supplied in surplus amounts. Nevertheless, Si application to crops may enhance the uptake of nitrogen and iron when they are supplied in deficient to luxurious amounts, while potassium uptake enhanced by Si application is often involved in alleviating salt stress and inhibiting excess sodium uptake in plants. More importantly, the amount of Si accumulated in plant positively correlates with nutrients release during the decay of crop biomass, but negatively correlates with straw decomposability due to the reduced lignin synthesis. The Si-mediated plant growth and litter decomposition collectively suggest that Si cycling in croplands plays important roles in biogeochemical cycles of carbon and nutrients. Hence, scientific Si management in croplands will be helpful for maintaining sustainable development of agriculture.
18.	Nyman, Alexandra, et al. (author) A nationwide acid sulfate soil study : A rapid and cost-efficient approach for characterizing large-scale features 2023 In: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 869 Journal article (peer-reviewed)abstract Acid sulfate soils are sulfide-rich soils that pose a notable environmental risk as their strong acidity and low pH mobilizes metals from soil minerals leading to both acidification and metal contamination of the surrounding environment. In this study a rapid and cost-efficient approach was developed to resolve the main distribution patterns and geochemical features of acid sulfate soils throughout coastal plains stretching for some 2000 km in eastern, southern, and western Sweden. Of the investigated 126 field sites, 47 % had acid sulfate soils including 33 % active, 12 % potential, and 2 % pseudo acid sulfate soils. There were large regional variations in the extent of acid sulfate soils, with overall much higher proportions of these soils along the eastern coastal plains facing the Baltic Sea than the western coastal plains facing the Kattegatt/Skagerrak (Atlantic Ocean). The sulfur concentrations of the soil's parent material, consisting of reduced near-pH neutral sediments, were correlated inversely both with the minimum pH of the soils in situ (rS = −0.65) and the pH after incubation (oxidation) of the reduced sediments (rS = −0.77). This indicated the importance of sulfide levels in terms of both present and potential future acidification. Hence, the higher proportion of acid sulfate soils in the east was largely the result of higher sulfur concentrations in this part of the country. The study showed that the approach was successful in identifying large-scale spatial patterns and geochemical characteristics of importance for environmental assessments related to these environmentally unfriendly soils.
19.	Nyman, Alexandra, et al. (author) Multi-element features of active acid sulfate soils across the Swedish coastal plains 2023 In: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 152 Journal article (peer-reviewed)abstract Acid sulfate soils are sulfide-rich soils with notable associated environmental risks. The low pH of these soils mobilizes metals from the soil minerals, which will lead to both acidification and metal contamination of the surrounding environment. This paper presents the results of a geochemical study of 66 profiles of acid sulfate soils collected from a total of 22 sites (three profiles for each site) on the Swedish coastal plains, which stretch for some 2000 km along the Baltic Sea and Kattegat. The reduced zone at the bottom of the profiles was characterized by pH frequently >6.0, the transition zone (above the reduced zone) by a steep pH gradient from near-neutral to weakly acidic, and the oxidized zone located above the transition zone by highly acidic conditions with a pH minimum <4.0. Each zone in each profile was sampled for geochemical analyses. The aqua regia extractable S concentrations ranged widely in the reduced zone (0.06–7.5%) and were strongly depleted in the oxidized zone (median decrease 69%) from extensive sulfide oxidation and associated severe acidification and sulfate leaching. In addition to S, there were significant losses from the oxidized zone of eight alkali and alkaline earth metals (Ba, Be, Ca, K, Li, Mg, Na, and Sr), four first row transition metals (Co, Mn, Ni, and Zn), three second row transition metals (Cd, Y, and Zr), the rare earth elements (Ce, La, and Yb), and Al, Th, and B. These elements would therefore be expected to be enriched in nearby surface waters, which was supported by hydrogeochemistry data from elsewhere in the boreal zone. Nineteen other chemical elements were not significantly lost from the oxidized zone relative to the reduced zone (Fe, Ti, W, Se, Sc, V, Cu, Cr, P, In, Te, Ag, Sb, Bi, Sn, Mo, U, As, and Pb) and therefore, would not be expected to occur in elevated concentrations in acid sulfate soil affected surface waters, as was supported by literature data from elsewhere in the boreal zone. A hypothesis of more extensive oxidation, acidification, and leaching of the soils in south Sweden (hemiboreal zone) than north Sweden (boreal zone) due to a warmer climate in the former region was rejected based upon pH and multi-element patterns from 9 field sites from the north and 12 field sites from the south. Consequently, the losses were likely primarily controlled by local factors, such as time since drainage and soil development. However, the oxidized zone was significantly thicker in the north (median: 75 cm) than south (median: 40 cm). This suggested that although the proportional losses (i.e., difference in elemental concentrations between the oxidized and reduced zones) were overall not different between the two regions, the total amount of elements lost from the soils will have been larger in the north. Of the elements with no significant losses, several were extracted with 1 M HCl to a larger extent in the oxidized than the reduced zone (Fe, As, Cr, Cu, Mo, Sc, Ti, U, and V). This indicated retention in the acidic environment following release from weathered and/or oxidized soil minerals. These elements, of which several are particularly toxic (As, Cr, and U), may thus be mobilized and leached if the soils geochemical conditions change either naturally or via human activities.
20.	Nystrand, Miriam I., et al. (author) Distribution and speciation of metals, phosphorus, sulfate and organic material in brackish estuary water affected by acid sulfate soils 2016 In: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 66, s. 264-274 Journal article (peer-reviewed)abstract Dissolved (<1 kDa) and colloidal (1 kDa-0.45 mu m) size fractions of sulfate, organic carbon (OC), phosphate and 17 metals/metalloids were investigated in the acidic Vora River and its estuary in Western Finland. In addition, geochemical modelling was used to predict the formation of free ions and complexes in these waters. The sampling was carried out during high-water flow in autumn and in spring when the abundantly occurring acid sulfate (AS) soils in the catchment area are extensively flushed. Based on the high concentrations of sulfate, acidity and several metals, it is clear that the Vora River and its estuary is strongly affected by AS soils. The high dissolved form of metals limits also the existence of fish and other organisms in this estuary, and certainly also in other similar shallow brackish estuaries elsewhere in the Gulf of Bothnia. However, generally already <20% saline sea water reduces the concentration for OC and several elements (Al, Cu, Cr, Fe, Pb, PO4 and U) by half and c. 20-30% saline sea water is needed to halve concentrations of Cd, Co, Mn, Ni and Zn. Consequently, these elements as well as organic matters were rapidly precipitated in the estuary, even after mixing with fairly small amounts of the alkaline brackish sea water. Aluminium, Cu, Fe and U most likely precipitate together with organic matter closest to the river mouth. Manganese is relatively persistent in solution and, thus, precipitates further down the estuary as Mn oxides, which concomitantly capture Ba, Cd, Co, Cu, Ni and Zn. In the inner estuary, the high contents of Al is as important than Fe in removing PO4 and, thus, also reducing the risk of algae blooms in near coastal areas influenced by AS soils in the Gulf of Bothnia. Moreover, the dispersion of metals far out in the estuary is dependent on hydrological conditions, i.e. with high flows the plume of metal-rich water will spread further out in the estuary. Furthermore, the extensive drainage of the catchment and subsequent artificial enlargement of the river channel during recent decades has not only enabled oxidation of sulfidic sediments, but strongly increased flow peaks that reach further out in the estuary. (C) 2016 Elsevier Ltd. All rights reserved.
21.	Peng, Bo, et al. (author) Geochemistry of major and trace elements and Pb-Sr isotopes of a weathering profile developed on the Lower Cambrian black shales in central Hunan, China 2014 In: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 51, s. 191-203 Journal article (peer-reviewed)abstract This paper reports a geochemical study on the major and trace elements and Pb-Sr isotopes of a weathering profile developed in the Lower Cambrian black shales in central Hunan (China). Six weathering horizons were identified and sampled vertically throughout the profile. The chemical composition of the profile consists of variable concentrations of the major elements Fe2O3, FeO, MnO, MgO, CaO, Na2O, and P2O5 and of less variable concentrations of SiO2, TiO2, Al2O3, and K2O. The chemical change caused by weathering is estimated by mass-balance calculations, and the results show that the element mobility is characterised by substantial loss of SiO2, FeO, CaO, K2O, Na2O, LOI, Cr, V, Ba, Cs, Rb, Sr, U, and Th, and moderate loss of Al2O3, MgO, Fe2O3, Ni, Cu, Pb, Tl, Sn, Sc, Ge and REE (Y). The high field strength elements TiO2, Sn, Sc, U, Ga, Ge, Zr, Hf, Nb, and Ta were immobile during weathering. The chemical changes and the Pb-Sr isotopic data suggest that four types of chemical reactions occurred: the oxidation of sulphide minerals (e.g., pyrite) and organic carbon (OS), the dissolution of less resistant clinochlore-Ia, calcite, and P-bearing minerals (DL), the dissolution of detrital albite and microcline (DA), and the transformation of clay (TC) minerals (e.g., muscovite and illite-smectite). These chemical reactions then led to two stages of geochemical processes, an early stage of chemical differentiation and a later stage of chemical homogenisation. The chemical differentiation dominated by the OS, DL, and DA reactions, led to the leaching of mobile elements (e.g., MgO, Na2O, K2O, P2O5, Sr, and REE) and the redistribution of some less mobile elements (e.g., SiO2 and Al2O3). In contrast, the chemical homogenisation, which was caused by TC reactions, led to the leaching of both mobile and less mobile elements from the system and ultimately transformed the weathered black shales into soil. Soils derived from black shales in South China might result from the above two geochemical processes. (C) 2014 Elsevier Ltd. All rights reserved.
22.	Qin, Zhilian, et al. (author) Vertical distributions of organic carbon fractions under paddy and forest soils derived from black shales : Implications for potential of long-term carbon storage 2021 In: Catena (Cremlingen. Print). - : Elsevier. - 0341-8162 .- 1872-6887. ; 198, s. 1-8 Journal article (peer-reviewed)abstract Black shales are characterized by a high content of organic carbon (C). Few studies have focused on the influence of land use on soil organic C (SOC) fractions from soils derived from black shale (black shale soils). The objective of this study was to elucidate the influence of land use on SOC fractions in black shale soils combining chemical determination and stable C isotope analysis techniques. Herein, we determined labile organic C (LOC), semilabile organic C (Semi-LOC), and recalcitrant organic C (ROC) fractions in various depths of soils in paddy fields (0-70 cm) and forests (0-120 cm) from black shale distribution region in Hunan province, China, and then investigated delta C-13 values of these soils. Results showed that the contents of LOC, Semi-LOC, and ROC in paddy soils (1.63-7.35 g kg(-1), 0.35-1.21 g kg(-1), and 3.75-14.8 g kg(-1), respectively) and forest soils (0.73-4.94 g kg(-1), 0.12-0.89 g kg(-1), and 1.44-8.96 g kg(-1), respectively) are significantly decreased with increasing depth. The contribution made by LOC to SOC in paddy soils was significantly lower than that in forest soils, while the contribution made by ROC to SOC was significantly higher in paddy soils than that in forest soils. In these two land uses, the delta C-13 values were higher in SOC compared to the ROC fraction, while the delta C-13 values were close in the ROC fraction below 20 cm soil depth. Our study indicated that i) new C is mainly limited to the surface soil layer (0-10 cm) in forests, while it can be leached along the soil profiles in paddy fields; ii) the estimated ROC pool is similar to 900 Pg within the 0-100 cm soil layer in terrestrial ecosystems, which should better represent the ability of soil C sequestration.
23.	Sandhi, Arifin, et al. (author) Arsenic in the water and agricultural crop production system : Bangladesh perspectives 2022 In: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 29, s. 51354-51366 Research review (peer-reviewed)abstract The presence of high levels of carcinogenic metalloid arsenic (As) in the groundwater system of Bangladesh has been considered as one of the major environmental disasters in this region. Many parts of Bangladesh have extensively reported the presence of high levels of arsenic in the groundwater due to both geological and anthropogenic activities. In this paper, we reviewed the available literature and scientific information regarding arsenic pollution in Bangladesh, including arsenic chemistry and occurrences. Along with using As-rich groundwater as a drinking-water source, the agricultural activities and especially irrigation have greatly depended on the groundwater resources in this region due to high water demands for ensuring food security. A number of investigations in Bangladesh have shown that high arsenic content in both soil and groundwater may result in high levels of arsenic accumulation in different plants, including cereals and vegetables. This review provides information regarding arsenic accumulation in major rice varieties, soil-groundwater-rice arsenic interaction, and past arsenic policies and plans, as well as previously implemented arsenic mitigation options for both drinking and irrigation water systems in Bangladesh. In conclusion, this review highlights the importance and necessity for more in-depth studies as well as more effective arsenic mitigation action plans to reduce arsenic incorporation in the food chain of Bangladesh.
24.	Shahabi-Ghahfarokhi, Sina, et al. (author) Extensive dispersion of metals from hemiboreal acid sulfate soil into adjacent drain and wetland 2024 In: Applied Geochemistry. - : Elsevier Ltd.. - 0883-2927 .- 1872-9134. ; 136 Journal article (peer-reviewed)abstract Extensive red/brown precipitates of unknown origin and composition have caused ecological degradation of a wetland nature reserve (the Water Kingdom Biosphere Reserve) in the hemiboreal zone in south Sweden. Chemical analyses of samples containing the precipitates showed strong dominates of Fe and elevated levels of rare earth elements (REEs), Be, and U. In addition, synchrotron-based analyses indicated that the Fe in these precipitates was bound largely in akageneite and/or schwertmannite. Under nearby farmlands, acid sulfate soils, developing on sulfide-bearing sediments and notorious for abundant export of metals, were identified and found to be widespread, deep (down to the sampling depth of 180 cm or deeper), and very acidic (minimum pH range for soil profiles: 2.8–3.5). In-between the farmland and wetland was a central drain that can act as both a transporter and sink of elements leached from the acid sulfate soils. In the drain had accumulated sediments that had strongly elevated concentrations of Al (15%), ∑REE (2725 mg/kg), Be (15 mg/kg), and U (37 mg/kg). Based on these data and features, a conceptual model for the areas was proposed. The acid sulfate soil releases several major and trace elements, including Fe2+, which are transported in acidic waters via drainpipes to the central drain where pH increases, causing extensive precipitation of Al, REEs, Be, and U as well as Fe2+ oxidation and formation of Fe oxyhydroxides and oxyhydroxysulfates. A substantial part of the Fe2+ in the drain water, however, remains in solution, so when this water is ultimately pumped to the wetland, large amounts of Fe2+ together with significant amounts of Al, REEs, Be, and U and transported to the wetland where Fe2+ is finally oxidized, precipitated and retained. Yet several other metals, leached abundantly from the acid sulfate soils (Mn, Zn, Ni, Co, and Cd), were not found in elevated levels in any of the recipients and therefore most likely have been transported beyond our sampling sites and has thus reached further outin the ecologically sensitive wetland.
25.	Shahabi-Ghahfarokhi, Sina, et al. (author) Removal and potential recovery of dissolved metals from acid sulfate soil drainage by spent coffee-grounds and dissolved organic carbon 2022 In: Environmental Advances. - : Elsevier. - 2666-7657. ; 8 Journal article (peer-reviewed)abstract This study explores the reuse of spent coffee-grounds (SCGs) and the use of dissolved humic acid (DHA) to remediate acid sulfate (AS) soil drainage using adsorption and precipitation experiments, with changing pH,weight/volume, and concentrations (mg/L of dissolved organic carbon). In addition, this study aims to extend the usability of the SCGs, after being reacted with AS soil drainage, by identifying the potential recovery of incinerated SCGs from the ash of the SCGs produced incineration. As compared to DHA, the SCGs had greater efficiency in removing metals, such as Al (98%), Ca (96%), Co (94%), Fe (88%), Mn (100%), Ni (93%), and Zn (96%). However, the removal of Fe was significantly reduced when higher weight/volume of SCGs were introduced. In addition, SCGs could not bind sulfur, while DHA had removed up to 25% of S from the solution.This suggests the simultaneous use of SCGs and DHA could restrict the formation of problematic Fe(III) secondary compounds (e.g., schwertmannite/akaganeite) which are problematic in some AS soil settings. The results show that Co (69%), Ni (58%), Mn (60%), Fe (59%), Zn (55%), and Al (34%) had the highest recovery percentage by sequential chemical extraction, respectively. The recovery of metals, as well as the removal of dissolved metals from the drainage water, illustrates the effectiveness of the proposed approach for SCGs reuse.
26.	Shahabi-Ghahfarokhi, Sina, et al. (author) The response of metal mobilization and redistribution to reoxygenation in Baltic Sea anoxic sediments 2022 In: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 837 Journal article (peer-reviewed)abstract To bring life back to anoxic coastal and sea basins, reoxygenation of anoxic/hypoxic zones has been proposed. This research focuses on the metals released during the oxidization of sediments from two locations in the anoxic Eastern Gotland Basin under a laboratory-scale study. Triplicate experimental cores and reference cores were collected from the North and South Eastern Gotland Basins. The oxygenation of the water column took place over a 96-hour experiment in a dark and 5 °C environment. In 12 and 24 hour intervals, the surface waters were exchanged and, over time, analyzed for pH, electroconductivity (EC), total organic carbon (TOC), soluble metal concentrations, and the top samples (0–10 cm) were analyzed with 3-step (E1: water-soluble, E2: exchangeable, and E3: organic-bound) sequential chemical extraction (SCE). Results show stable pH and decreasing EC in the column waters. The EC indicates that metals are released in the initial phases (12 h) of reoxygenation for both sites. Arsenic, Ba, Co, Mn, Rb, U, K, Sr, and Mo are released into the water column during the 96 hour experiment, and based on the calculations for the entire East Gotland Basin, would mean 8, 50, 0.55, 734, 53, 27, 347,178, 3468, and 156 μg L−1 are released, respectively. Elements Mn, Mo, U, and As are released in higher concentrations during the experiment than previously measured in the Eastern Gotland Basin, which provides vital information for future proposed remediation and natural geochemical processes with their known environmental impacts. The SCE results show that redox-sensitive metals (Mn, U, and Mo) are released in the highest concentrations into the solution. The relationship between the highest released metals (beside redox-sensitive) into solution over the oxygenation and their initial abundant phase is noticed, where the smallest released concentrations belong to K < Rb < Sr in E2, and As
27.	Shilei, Yang, et al. (author) A review of carbon isotopes of phytoliths : implications for phytolith-occluded carbon sources 2020 In: Journal of Soils and Sediments. - : Springer. - 1439-0108 .- 1614-7480. ; 20:4, s. 1811-1823 Journal article (peer-reviewed)abstract Purpose Phytolith-occluded carbon (PhytOC) is mainly derived from the products of photosynthesis, which can be preserved in soils and sediments for hundreds-to-thousands of years due to the resilient nature of the amorphous phytolith silica. Therefore, stable and radioactive carbon (C) isotopes of phytoliths can be effectively utilized in paleoecological and archeological research. However, there still exists debate about the applicability of C isotopes of phytoliths, as a “two-pool” hypothesis to characterize PhytOC sources has been proposed, whereby a component of the PhytOC is derived from soil organic matter (SOM) absorbed through plant roots. Therefore, it is necessary to review this topic to better understand the source of PhytOC. Materials and method We introduce the stable and radioactive C isotopic compositions of PhytOC, present the impacts of different extraction methods on the study of PhytOC, and discuss the implications of these factors for determining the sources of PhytOC. Results and discussion Based on this review, we suggest that organic matter synthesized by photosynthesis is the main source of PhytOC. However, it is important to make clear whether and how SOM-derived C present in phytoliths influence the controversial “too-old” skew and isotopic fractionation. Conclusions Though the two-pool hypothesis has been proved by many researches, the carbon isotopes of phytoliths still have potential in paleoecology and archeology, because the main source is photosynthesis and many previous studies put forward the availability of these parameters. This review also shows that phytolith C isotopes may vary with different organic C compounds within phytoliths, which needs further study at the molecular scale. Different phytolith extraction methods can influence 14C dating results.
28.	Sjöberg, Susanne, et al. (author) Microbe-Mediated Mn Oxidation - A Proposed Model of Mineral Formation 2021 In: Minerals. - : MDPI. - 2075-163X. ; 11:10 Journal article (peer-reviewed)abstract Manganese oxides occur in a wide range of environmental settings either as coatings on rocks, sediment, and soil particles, or as discrete grains. Although the production of biologically mediated Mn oxides is well established, relatively little is known about microbial-specific strategies for utilizing Mn in the environment and how these affect the morphology, structure, and chemistry of associated mineralizations. Defining such strategies and characterizing the associated mineral properties would contribute to a better understanding of their impact on the local environment and possibly facilitate evaluation of biogenicity in recent and past Mn accumulations. Here, we supplement field data from a Mn rock wall deposit in the Ytterby mine, Sweden, with data retrieved from culturing Mn oxidizers isolated from this site. Microscopic and spectroscopic techniques are used to characterize field site products and Mn precipitates generated by four isolated bacteria (Hydrogenophaga sp., Pedobacter sp., Rhizobium sp., and Nevskia sp.) and one fungal-bacterial co-culture (Cladosporium sp.-Hydrogenophaga sp. Rhizobium sp.-Nevskia sp.). Two of the isolates (Pedobacter sp. and Nevskia sp.) are previously unknown Mn oxidizers. At the field site, the onset of Mn oxide mineralization typically occurs in areas associated with globular wad-like particles and microbial traces. The particles serve as building blocks in the majority of the microstructures, either forming the base for further growth into laminated dendrites-botryoids or added as components to an existing structure. The most common nanoscale structures are networks of Mn oxide sheets structurally related to birnessite. The sheets are typically constructed of very few layers and elongated along the octahedral chains. In places, the sheets bend and curl under to give a scroll-like appearance. Culturing experiments show that growth conditions (biofilm or planktonic) affect the ability to oxidize Mn and that taxonomic affiliation influences crystallite size, structure, and average oxidation state as well as the onset location of Mn precipitation.
29.	Song, Zhaoliang, et al. (author) High potential of stable carbon sequestration in phytoliths of China's grasslands 2022 In: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 28:8, s. 2736-2750 Journal article (peer-reviewed)abstract Phytolith carbon (C) sequestration plays a key role in mitigating global climate change at a centennial to millennial time scale. However, previous estimates of phytolith-occluded carbon (PhytOC) storage and potential in China's grasslands have large uncertainties mainly due to multiple data sources. This contributes to the uncertainty in predicting long-term C sequestration in terrestrial ecosystems using Earth System Models. In this study, we carried out an intensive field investigation (79 sites, 237 soil profiles [0-100 cm], and 61 vegetation assessments) to quantify PhytOC storage in China's grasslands and to better explore the biogeographical patterns and influencing factors. Generally, PhytOC production flux and soil PhytOC density in both the Tibetan Plateau and the Inner Mongolian Plateau had a decreasing trend from the Northeast to the Southwest. The aboveground PhytOC production rate in China's grassland was 0.48 x 10(6) t CO2 a(-1), and the soil PhytOC storage was 383 x 10(6) t CO2. About 45% of soil PhytOC was stored in the deep soil layers (50-100 cm), highlighting the importance of deep soil layers for C stock assessments. Importantly, the Tibetan Plateau had the greatest contribution (more than 70%) to the PhytOC storage in China's grasslands. The results of multiple regression analysis indicated that altitude and soil texture significantly influenced the spatial distribution of soil PhytOC, explaining 78.1% of the total variation. Soil phytolith turnover time in China's grasslands was mainly controlled by climatic conditions, with the turnover time on the Tibetan Plateau being significantly longer than that on the Inner Mongolian Plateau. Our results offer more accurate estimates of the potential for phytolith C sequestration from ecological restoration projects in degraded grassland ecosystems. These estimates are essential to parameterizing and validating global C models.
30.	Wu, Lele, et al. (author) Organic matter composition and stability in estuarine wetlands depending on soil salinity 2024 In: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 945 Journal article (peer-reviewed)abstract Coastal wetlands are key players in mitigating global climate change by sequestering soil organic matter. Soil organic matter consists of less stable particulate organic matter (POM) and more stable mineral-associated organic matter (MAOM). The distribution and drivers of MAOM and POM in coastal wetlands have received little attention, despite the processes and mechanisms differ from that in the upland soils. We explored the distribution of POM and MAOM, their contributions to SOM, and the controlling factors along a salinity gradient in an estuarine wetland. In the estuarine wetland, POM C and N were influenced by soil depth and vegetation type, whereas MAOM C and N were influenced only by vegetation type. In the estuarine wetland, SOM was predominantly in the form of MAOM (> 70 %) and increased with salinity (70 %–76 %), leading to long-term C sequestration. Both POM and MAOM increased with SOM, and the increase rate of POM was higher than that of MAOM. Aboveground plant biomass decreased with increasing salinity, resulted in a decrease in POM C (46 %–81 %) and N (52 %–82 %) pools. As the mineral amount and activity, and microbial biomass decreased, the MAOM C (2.5 %–64 %) and N pool (8.6 %–59 %) decreased with salinity. When evaluating POM, the most influential factors were microbial biomass carbon (MBC) and dissolved organic carbon (DOC). Key parameters, including MBC, DOC, soil salinity, soil water content, aboveground plant biomass, mineral content and activity, and bulk density, were identified as influencing factors for both MAOM abundance. Soil water content not only directly controlled MAOM, but together with salinity also indirectly regulated POM and MAOM by controlling microbial biomass and aboveground plant biomass. Our findings have important implications for improving the accumulation and increased stability of soil organic matter in coastal wetlands, considering the global sea level rise and increased frequency of inundation.
31.	Wu, Yuntao, et al. (author) Climatic controls on stable carbon and nitrogen isotope compositions of temperate grasslands in northern China 2023 In: Plant and Soil. - : Springer. - 0032-079X .- 1573-5036. ; 491, s. 133-144 Journal article (peer-reviewed)abstract Aims The natural abundances of stable carbon (C) and nitrogen (N) isotopes (delta C-13 and delta N-15) are extensively used to indicate the C and N biogeochemical cycles at large spatial scales. However, the spatial patterns of delta C-13 and delta N-15 in plant-soil systems of grasslands in northern China and their main driving factors across regional climatic gradient are still not well understood. Methods We measured plant and soil delta C-13 and delta N-15 compositions as well as their associated environmental factors across 2000 km climatic gradient (-0.2 to 9 degrees C; 152 to 502 mm) in grasslands of northern China. Results The soil delta C-13 and delta N-15 values in surface were lower than those in bottom for temperate typical steppe but had no significant differences for temperate meadow steppe and temperate desert steppe. Soil delta C-13 values declined with increasing soil organic carbon (SOC) but increased as mean annual temperature (MAT). These changes were attributed to the microbial decomposition rate. The delta N-15 values in soil and plant were negatively correlated with MAT and mean annual precipitation (MAP), which were mainly related to the low soil organic matter mineralization rate and the shift of dominant species from C-4 to C-3. Conclusions Our results indicate the spatial patterns and different influencing factors on delta C-13 and delta N-15 values along the climatic gradient in grasslands of northern China. The findings will provide scientific references for future research on the C and N biogeochemical cycles of temperate grasslands.
32.	Wu, Yuntao, et al. (author) Silicon promotes biomass accumulation in Phragmites australis under waterlogged conditions in coastal wetland 2024 In: Plant and Soil. - : Springer Nature. - 0032-079X .- 1573-5036. Journal article (peer-reviewed)abstract Aims Previous studies have shown that silicon (Si) can affect plant growth and yield by regulating the availability of other nutrients. However, the mechanisms by which Si affects plant biomass accumulation in coastal wetlands are not well explored. Methods We conducted a sampling campaign across the whole growing season of Phragmites australis under waterlogging and drought conditions in coastal wetland, and quantified the effects of Si availability on biomass accumulation. Results Compared with drought condition, the waterlogged condition improved the utilization efficiency of nitrogen (N) and phosphorus (P) of P. australis regulated by higher Si contents. Meanwhile, the increased Si contents promoted the utilization of N and P in leaf, suggesting that the increase in Si contents optimizes the photosynthetic process. Lignin contents in P. australis decreased with the increasing Si contents, which confirmed that Si can replace structural carbon components. In addition, principal component analysis (PCA) showed aboveground biomass accumulation of P. australis was synchronized with Si accumulation, indicating that Si was a beneficial element to promote biomass accumulation. Conclusions Our study implies that increasing Si availability is conducive to biomass accumulation of P. australis in waterlogged wetlands, which will provide important scientific references for the management of coastal wetland ecosystem and the increase of global 'blue carbon' sequestration.
33.	Xia, Shaopan, et al. (author) Distribution, sources, and decomposition of soil organic matter along a salinity gradient in estuarine wetlands characterized by C:N ratio, δ13C-δ15N, and lignin biomarker 2021 In: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 27:2, s. 417-434 Journal article (peer-reviewed)abstract Despite increasing recognition of the critical role of coastal wetlands in mitigating climate change, sea‐level rise, and salinity increase, soil organic carbon (SOC) sequestration mechanisms in estuarine wetlands remain poorly understood. Here, we present new results on the source, decomposition, and storage of SOC in estuarine wetlands with four vegetation types, including single Phragmites australis (P, habitat I), a mixture of P. australis and Suaeda salsa (P + S, habitat II), single S. salsa (S, habitat III), and tidal flat (TF, habitat IV) across a salinity gradient. Values of δ13C increased with depth in aerobic soil layers (0–40 cm) but slightly decreased in anaerobic soil layers (40–100 cm). The δ15N was significantly enriched in soil organic matter at all depths than in the living plant tissues, indicating a preferential decomposition of 14N‐enriched organic components. Thus, the kinetic isotope fractionation during microbial degradation and the preferential substrate utilization are the dominant mechanisms in regulating isotopic compositions in aerobic and anaerobic conditions, respectively. Stable isotopic (δ13C and δ15N), elemental (C and N), and lignin composition (inherited (Ad/Al)s and C/V) were not completely consistent in reflecting the differences in SOC decomposition or accumulation among four vegetation types, possibly due to differences in litter inputs, root distributions, substrate quality, water‐table level, salinity, and microbial community composition/activity. Organic C contents and storage decreased from upstream to downstream, likely due to primarily changes in autochthonous sources (e.g., decreased onsite plant biomass input) and allochthonous materials (e.g., decreased fluvially transported upland river inputs, and increased tidally induced marine algae and phytoplankton). Our results revealed that multiple indicators are essential to unravel the degree of SOC decomposition and accumulation, and a combination of C:N ratios, δ13C, δ15N, and lignin biomarker provides a robust approach to decipher the decomposition and source of sedimentary organic matter along the river‐estuary‐ocean continuum.
34.	Xia, Shaopan, et al. (author) Silicon accumulation controls carbon cycle in wetlands through modifying nutrients stoichiometry and lignin synthesis of Phragmites australis 2020 In: Environmental and Experimental Botany. - : Elsevier. - 0098-8472 .- 1873-7307. ; 175, s. 1-11 Journal article (peer-reviewed)abstract Silicon (Si) is one of the most abundant elements in the Earth’s crust but its role in governing the biogeochemicalcycling of other elements remains poor understood. There is a paucity of information on the role of Si in wetlandplants, and how this may alter wetland C production and storage. Therefore, this study investigated Si distribution,nutrient stoichiometry and lignin abundance in Phragmites australis from a wetland system in China tobetter understand the biogeochemical cycling and C storage. Our data show that Si content (ranging between0.202% to 6.614%) of Phragmites australis is negatively correlated with C concentration (38.150%–47.220%).Furthermore, Si content was negatively antagonistically related to the concentration of lignin-derived phenols inthe stem (66.763–120.670 mg g-1 C) and sheath (65.400–114.118 mg g-1 C), but only a weak relationship wasobserved in the leaf tissue (36.439–55.905 mg g-1 C), which is relevant to the photosynthesis or stabilizationfunction of the plant tissues. These results support the notion that biogenic Si (BSi) can substitute lignin as astructural component, due to their similar eco-physiological functions, reduces costs associated with ligninbiosynthesis. The accumulation of BSi increased total biomass C storage and nutrient accumulation due togreater productivity of Phragmites australis. On the other hand, BSi regulated litter composition and quality (e.g.,nutrient stoichiometry and lignin) that provide a possibility for the factors affecting litter decomposition. Thuscompeting processes (i.e., biomass quantity vs quality) can be influenced by Si cycling in wetlands.
35.	Xia, Shaopan, et al. (author) Storage, patterns and influencing factors for soil organic carbon in coastal wetlands of China 2022 In: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 28:20, s. 6065-6085 Journal article (peer-reviewed)abstract Soil organic carbon (SOC) in coastal wetlands, also known as "blue C," is an essential component of the global C cycles. To gain a detailed insight into blue C storage and controlling factors, we studied 142 sites across ca. 5000 km of coastal wetlands, covering temperate, subtropical, and tropical climates in China. The wetlands represented six vegetation types (Phragmites australis, mixed of P. australis and Suaeda, single Suaeda, Spartina alterniflora, mangrove [Kandelia obovata and Avicennia marina], tidal flat) and three vegetation types invaded by S. alterniflora (P. australis, K. obovata, A. marina). Our results revealed large spatial heterogeneity in SOC density of the top 1-m ranging 40-200 Mg C ha(-1), with higher values in mid-latitude regions (25-30 degrees N) compared with those in both low- (20 degrees N) and high-latitude (38-40 degrees N) regions. Vegetation type influenced SOC density, with P. australis and S. alterniflora having the largest SOC density, followed by mangrove, mixed P. australis and Suaeda, single Suaeda and tidal flat. SOC density increased by 6.25 Mg ha(-1) following S. alterniflora invasion into P. australis community but decreased by 28.56 and 8.17 Mg ha(-1) following invasion into K. obovata and A. marina communities. Based on field measurements and published literature, we calculated a total inventory of 57 x 10(6) Mg C in the top 1-m soil across China's coastal wetlands. Edaphic variables controlled SOC content, with soil chemical properties explaining the largest variance in SOC content. Climate did not control SOC content but had a strong interactive effect with edaphic variables. Plant biomass and quality traits were a minor contributor in regulating SOC content, highlighting the importance of quantity and quality of OC inputs and the balance between production and degradation within the coastal wetlands. These findings provide new insights into blue C stabilization mechanisms and sequestration capacity in coastal wetlands.
36.	Xie, S., et al. (author) A re-assessment of metal pollution in the Dexing mining area in Jiangxi province, China : current status, hydro-geochemical controls, and effectiveness of remediation practices 2022 In: International Journal of Environmental Science and Technology. - : Springer Nature. - 1735-1472 .- 1735-2630. ; 19, s. 10707-10722 Journal article (peer-reviewed)abstract This study re-assess the environmental impacts of the Dexing copper mine (the largest open-pit copper mine in Asia) on the Lean river and its two tributaries (the Dawu river and Jishui river) in the Jiangxi province, China, with particular focus on metal pollution as well as the effectiveness and side-effects of remediation activities. Results show that the Dawu river and its mixing zone with the Lean river were still heavily influenced by acid mine drainage (AMD) and loaded with elevated levels of metals, in particular Mn, Ni, and Al whose concentrations were frequently above the health-based guideline values. Manganese and Ni in the AMD-impacted waters were predicted to occur as free ions or sulfate and carbonate complexes, and thus highly-toxic to living organisms. Although Al in the AMD-impacted waters was predicted to exist largely as colloidal hydroxides with low bioavailability, abundant formation of such nano-sized particles could impair the respiratory and circulatory systems of aquatic macro-invertebrates. The integration and comparison of the results from the current and previous studies show that the concentrations of several metals (Cu, Zn, and Cd) in the Dawu river decreased significantly after 2011-2012, during which several remediation practices were implemented (e.g., AMD neutralization, excavation of contaminated sediments in impounded rivers, and rehabilitation of mine tailings and open-pit slopes). This provides evidence that these remediation practices have effectively limited the dispersion of metals from the mining area. However, AMD neutralization greatly enhanced the release of sulfate, making the mining area an even more important sulfate source.
37.	Xu, Jingzhe, et al. (author) Geochemistry of soils derived from black shales in the Ganziping mine area, western Hunan, China 2013 In: Environmental Earth Sciences. - : Springer Science and Business Media LLC. - 1866-6280 .- 1866-6299. ; 70:1, s. 175-190 Journal article (peer-reviewed)abstract The geochemistry of major and trace elements (including heavy metals and rare earth elements) of the fresh and weathered black shales, and the soils derived from black shales in the Ganziping mine area in western Hunan province (China) were studied using the following techniques: X-ray fluorescence (XRF), inductively coupled plasma mass spectrometer (ICP-MS) and X-ray diffraction (XRD). The results show that the black-shale soils are significantly enriched with Al2O3 and Fe2O3, and depleted of mobile elements CaO, Na2O and K2O. The soils are also highly enriched with heavy metals U, V, Ni, Ba, Cu, Zn and Pb, that may cause potential heavy-metal contamination of the soils. Composition of the soils is homogeneous compared to the weathered black shales, for which the concentrations of major elements except CaO and Na2O, and trace elements except heavy metals (U, V, Ni, Ba, Cu, Zn and Pb) as well as the mobile Sr, show lower variations than in the weathered black shales. Ratios of Zr/Hf, Ta/Nb, Y/Ho, Nd/Sm, and Ti/(Ti + Zr), of the soils are also less variable, with values constantly similar to that of the fresh and weathered black shales correspondingly. Thus, components of the soils are believed to be contributed from the parent black shales through weathering and pedogenesis. It is concluded that the soils were formed by at least two stages of geochemical processes: the early stage of chemical differentiation and the later stage of chemical homogenization. The chemical differentiation that was taken during black-shale weathering might have caused the depletion of CaO and Na2O, and the enrichment of Al2O3 and Fe2O3; while the chemical homogenization that was taken during pedogenesis led to the depletion of SiO2 and K2O, and to the further enrichment of Al2O3 and Fe2O3. The heavy-metal enrichment (contamination) of the soils was then genetically related to the enrichment of Al2O3 and Fe2O3 in the soils.
38.	Yang, Shilei, et al. (author) Impact of grassland degradation on the distribution and bioavailability of soil silicon: Implications for the Si cycle in grasslands 2019 In: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 657, s. 811-818 Journal article (peer-reviewed)abstract Grassland ecosystems play an important role in the global terrestrial silicon (Si) cycle, and Si is a beneficial elementand structural constituent for the growth of grasses. In previous decades, grasslands have been degradedto different degrees because of the drying climate and intense human disturbance. However, the impact of grasslanddegradation on the distribution and bioavailability of soil Si is largely unknown. Here, we investigated vegetationand soil conditions of 30 sites to characterize different degrees of degradation for grasslands in the agropastoralecotone of northern China. We then explored the impact of grassland degradation on the distributionand bioavailability of soil Si, including total Si and four forms of noncrystalline Si in three horizons (0–10,10–20 and 20–40 cm) of different soil profiles. The concentrations of noncrystalline Si in soil profiles significantlydecreased with increasing degrees of degradation, being 7.35 ± 0.88 mg g−1, 5.36 ± 0.39 mg g−1, 3.81 ±0.37 mg g−1 and 3.60±0.26 mg g−1 in non-degraded, lightly degraded, moderately degraded and seriously degradedgrasslands, respectively. Moreover, the storage of noncrystalline Si decreased from higher than 40 t ha−1to lower than 23 t ha−1. The corresponding bioavailability of soil Si also generally decreased with grassland degradation.These processes may not only affect the Si pools and fluxes in soils but also influence the Si uptake in plants. We suggest that grassland degradation can significantly affect the global grassland Si cycle. Grasslandmanagement methods such as fertilizing and avoiding overgrazing can potentially double the content and storageof noncrystalline Si in soils, thereby enhancing the soil Si bioavailability by N17%.
39.	Yang, Xiaomin, et al. (author) Phytolith-rich straw application and groundwater table management over 36 years affect the soil-plant silicon cycle of a paddy field 2020 In: Plant and Soil. - : Springer. - 0032-079X .- 1573-5036. ; 454, s. 343-358 Journal article (peer-reviewed)abstract Background and aims Silicon (Si) deficiency is a major constraint on rice production. The objective of this study was to evaluate the long-term influence of phytolith-rich straw return and groundwater table management on labile Si fractions in paddy soil and subsequent plant Si uptake. Methods A field experiment was conducted over 36 years in subtropical China with different application doses of phytolith-rich straw and a groundwater table of either 20 or 80 cm. An optimized sequential chemical extraction procedure allowed us to determine labile Si fractions, represented by CaCl2-Si, Acetic-Si, H2O2-Si, Oxalate-Si, and Na2CO3-Si. Additional analyses included the determination of amorphous silica particles in soil, phytoliths in supplied straw, Si in planted rice straw, and the dissolution rate of phytoliths extracted from supplied straw. Results Long-term application of phytolith-rich straw significantly increased the H2O2-Si and Na2CO3-Si contents. The CaCl2-Si (5.21-7.91 mg kg(- 1)), H2O2-Si (50.0-72.4 mg kg(- 1)) and Na2CO3-Si (3.33-4.60 g kg(- 1)) contents were positively correlated with soil organic carbon. The Si content (13.6-28.9 g kg(-& x200d;1)) in planted rice straw significantly (p < 0.05) increased with the application dose of phytolith-rich straw under both groundwater tables. This effect was significantly (p < 0.05) greater under 80 cm groundwater table than under 20 cm groundwater table for matching straw amendments. Conclusions This study indicates that long-term application of phytolith-rich straw and groundwater management significantly increase soil Si bioavailability by promoting accumulation of organic matter and phytoliths, and enhancing the soil-plant Si cycle.
40.	Yang, Xiaomin, et al. (author) Quantification of different silicon fractions in broadleaf and conifer forests of northern China and consequent implications for biogeochemical Si cycling 2020 In: Geoderma. - : Elsevier. - 0016-7061 .- 1872-6259. ; 361, s. 1-10 Journal article (peer-reviewed)abstract The terrestrial biogeochemical silicon (Si) cycle significantly contributes to maintaining the functions and sustainability of terrestrial ecosystems. Over the short term, the biogeochemical Si cycle can be strongly influenced by dissolved Si, organic bound Si, Si adsorbed to pedogenic oxides/hydroxides, and biogenic and pedogenic amorphous Si. However, quantitative studies about these relatively soluble Si fractions are rare. In this study, we quantified different Si fractions in the 0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm and 40–50 cm soil layers of broadleaf forests (Betula forest and Quercus forest) and conifer forests (Larix forest and Pinus forest) in northern China using a sequential chemical extraction scheme optimized for these Si fractions. The results showed that the total Si (Sit) in the soil layers consisted of 97.7–98.5% crystalline Si (Sicry) and 1.5–2.3% non-crystalline Si (Sinoncry) fractions. Within the Sinoncry fraction, the proportions of dissolved Si (Sidis), organic matter bound Si (Siorg), pedogenic oxides/hydroxides chemisorbed Si (Sisorb), and amorphous Si (Siamor) were 3.4–6.7%, 5.5–8.9%, 6.3–8.5%, and 77.7–84.8%, respectively. Although the Sidis fraction was the least abundant component, it is at the center of the interconversion processes among the different Sinoncry fractions. The Siamor fraction was the largest component of Sinoncry and was composed of 37.7–71.9% biogenic amorphous Si (Sibio-amor) and 28.1–62.3% pedogenic amorphous Si (Siped-amor). Our study indicated that i) Siped-amor fraction is more easily influenced by soil pH comparing to Sibio-amor fraction; ii) the Sibio-amor fraction contributes more to the biogeochemical Si cycle in broadleaf forests, whereas the Siped-amorfraction contributes more in conifer forests; and iii) soil pH, soil organic matter, and plant community differences can influence the vertical distribution of the different Sinoncry fractions and thus affect the multiple transformation processes among these Si fractions in studied forests.
41.	Yang, Xiaoming, et al. (author) Spatial distribution of plant-available silicon and its controlling factors in paddy fields of China 2021 In: Geoderma. - : Elsevier. - 0016-7061 .- 1872-6259. ; 401 Journal article (peer-reviewed)abstract Silicon (Si) is beneficial for rice health and production by alleviating various biotic and abiotic stresses. However, the continual export of grain off-farm may result in Si deficiency for rice plants. The current levels of plant available Si (PASi) in rice paddies in China remain unclear, as do the factors that control PASi content in these soils. We conducted a nationwide sampling campaign across the paddy fields of China between 2016 and 2019, and used calcium chloride extractable Si (Si-CaCl2) and buffered acetate extractable Si (Si-NaAc, pH = 4) to quantify PASi. We show that Si-CaCl2 pool was mainly influenced by mean annual temperature (MAT), soil salinity, soil organic carbon (SOC), mean annual precipitation (MAP), and soil pH, suggesting both pedological and biological control mechanisms. However, the Si-NaAc pool was influenced most by soil pH, MAT and MAP, implying pedological control. Compared to data from the 1990s, the Si-NaAc content decreased by 14.1% on a national scale with an annual decline rate of 0.54%. Based on our investigation, at least 65% of China’s paddy fields are deficient in PASi, which is an increase in area of ~15% over the last 20 years. The principal regions where PASi deficiency was recorded are mainly located in southern China, with the levels of Si deficiency lowering as the paddy fields are located further north. The continual off-site removal of PASi from rice grain and straw will need to be addressed through the use of Si-fertilizers, including organic amendments, to maintain a productive and sustainable rice industry in China.
42.	Yu, Changxun, 1983-, et al. (author) A Combined X-ray Absorption and Mössbauer Spectroscopy Study on Fe Valence and Secondary Mineralogy in Granitoid Fracture Networks : Implications for Geological Disposal of Spent Nuclear Fuels 2020 In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:5, s. 2832-2842 Journal article (peer-reviewed)abstract Underground repository in crystalline bedrock is a widely accepted solution for long-term disposal of spent nuclear fuels. During future deglaciations, meltwater will intrude via bedrock fractures to the depths of future repositories where O2 left in the meltwater could corrode metal canisters and enhance the migration of redox-sensitive radionuclides. Since glacial meltwater is poor in reduced phases, the quantity and (bio)accessibility of minerogenic Fe(II) in bedrock fractures determine to what extent O2 in future meltwater can be consumed. Here, we determined Fe valence and mineralogy in secondary mineral assemblages sampled throughout the upper kilometer of fractured crystalline bedrock at two sites on the Baltic Shield, using X-ray absorption and Mössbauer spectroscopic techniques that were found to deliver matching results. The data point to extensive O2-consuming capacity of the bedrock fractures, because Fe(II)-rich phyllosilicates were abundant and secondary pyrite was dispersed deep into the bedrock with no overall increase in Fe(II) concentrations and Fe(II)/Fe(III) proportions with depth. The results imply that repeated Pleistocene deglaciations did not cause a measurable decrease in the Fe(II) pool. In surficial fractures, largely opened during glacial unloading, ferrihydrite and illite have formed abundantly via oxidative transformation of Fe(II)-rich phyllosilicates and recently exposed primary biotite/hornblende.
43.	Yu, Changxun, 1983-, et al. (author) A cryogenic XPS study of Ce fixation on nanosized manganite and vernadite: Interfacial reactions and effects of fulvic acid complexation 2018 In: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 483, s. 304-311 Journal article (peer-reviewed)abstract This study investigated interfacial reactions between aqueous Ce(III) and two synthetic nanosized Mn (hydr-) oxides (manganite: gamma-MnOOH, and vernadite: delta-MnO2) in the absence and presence of Nordic Lake fulvic acid (NLFA) at circumneutral pH by batch experiments and cryogenic X-ray photoelectron spectroscopy (XPS). The surfaces of manganite and vernadite were negatively charged (XPS-derived loadings of (Na+ K)/Cl > 1) and loaded with 0.42-4.33 Ce ions nm(-2). Manganite stabilized Ce-oxidation states almost identical to those for vernadite (approximately 75% Ce(IV) and 25% Ce(III)), providing the first experimental evidence that also a Mn (III) phase (manganite) can act as an important scavenger for Ce(IV) and thus, contribute to the decoupling of Ce from its neighboring rare earth elements and the development of Ce anomaly. In contrast, when exposed to Ce (III)-NLFA complexes, the oxidation of Ce by these two Mn (hydr-) oxides was strongly suppressed, suggesting that the formation of Ce(III) complexes with fulvic acid can stabilize Ce(III) even in the presence of oxidative Mn-oxide surfaces. The experiments also showed that Ce(III) complexed with excess NLFA was nearly completely removed, pointing to a strong preferential sorption of Ce(III)-complexed NLFA over free NLFA. This finding suggests that the Ce(III)-NLFA complexes were most likely sorbed by their cation side, i.e. Ce(III) bridging between oxide groups on the Mn (hydr-) oxides and negatively-charged functional groups in NLFA. Hence, Ce(III) was in direct contact with the oxidative manganite and vernadite but despite that not oxidized. An implication is that in organic-rich environments there may be an absence of Ce(IV) and Ce anomaly despite otherwise favorable conditions for Ce(III) oxidation.
44.	Yu, Changxun, et al. (author) Arsenic removal from contaminated brackish sea water by sorption onto Al hydroxides and Fe phases mobilized by land-use 2016 In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 542, s. 923-934 Journal article (peer-reviewed)abstract This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (<1 kDa) increase steadily from the creek mouth to the outer estuary, suggesting that inflowing seawater, rather than AS soil, is the major As source in the estuary. In sediments at the outer estuary, As was accumulated and diagenetically cycled in the surficial layers, as throughout much of the Bothnian Bay. In contrast, in sediments in the inner estuary, As concentrations and accumulation rates showed systematical peaks at greater depths. These peaks were overall consistent with the temporal trend of past As discharges from the Ronnskar smelter and the accompanied As concentrations in past sea-water of the Bothnian Bay, pointing to a connection between the historical smelter activities and the sediment-bound As in the inner estuary. However, the concentrations and accumulation rates of As peaked at depths where the smelter activities had already declined, but a large increase in the deposition of Al hydroxides and Fe phases occurred in response to intensified land-use in the mid 1960's and early 1970's. This correspondence suggests that, apart from the inflowing As-contaminated seawater, capture by Al hydroxides, Fe hydroxides and Fe-organic complexes is another important factor for As deposition in the inner estuary. After accumulating in the sediment, the solid-phase As was partly remobilized, as reflected by increased pore-water As concentrations, a process favored by As(V) reduction and high concentrations of dissolved organic matter. (C) 2015 Elsevier B.V. All rights reserved.
45.	Yu, Changxun, 1983-, et al. (author) Biogeochemical cycling of iron (hydr-)oxides and its impact on organic carbon turnover in coastal wetlands : A global synthesis and perspective 2021 In: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 218 Research review (peer-reviewed)abstract Coastal wetlands host large and dynamic reservoirs of organic carbon (C) and are also biogeochemical hotspots for a wide range of Fe (hydr-)oxides with different chemical reactivities, properties, and functions. The cycling of these iron (hydr-)oxides is closely coupled to that of organic C, which in turn strongly influences the magnitude and dynamics of organic C turnover in these ecosystems. This review synthesizes and summarizes current knowledge of distribution, turnover, and controls of Fe (hydr-)oxides, as well as their ecological roles and impacts on organic C turnover in coastal wetland ecosystems globally. Regional hydro-geochemical processes and anthropogenic activities in the uplands as well as soil texture exert a first-order control on the abundance and distribution of Fe (hydr-)oxides in coastal wetland soils, while the activities of plant roots and macro-organisms act as important biological drivers for the formation, transformation, and turnover of Fe (hydr-)oxides as well as associated organic C in both rhizosphere/burrows and bulk soils. The reported rates of dissimilatory Fe reduction (DFeR) are correlated with incubation temperature and the sizes of reactive Fe(III) phases. However, the contributions of DFeR to total anaerobic carbon oxidation were found to be correlated only with the size of reactive Fe(III) pools, meaning that all the identified processes contributing to the accumulation and formation of Fe hydroxides could increase the importance of the DFeR-dominated respiratory pathway and suppress sulfate reduction and methanogenesis. Additionally, Fe plaques dominated by amorphous Fe hydroxides are formed and cycled in close interaction with the activities of wetland plant roots, and likely provide several important ecological functions and contribute to maintaining high levels of plant productivity in coastal wetlands under different environmental stresses. The features and findings presented in this review not only contribute to an improved understanding of the biogeochemical cycle and ecological roles of Fe (hydr-)oxides in coastal wetlands, but also provide a basis for future studies on some highlighted key research areas. Such future studies will further increase our ability to understand and predict how the size, stability, and turnover of Fe (hydr-)oxides and organic C in coastal wetlands will respond to and affect global climate change.
46.	Yu, Changxun, et al. (author) Cerium sequestration and accumulation in fractured crystalline bedrock : The role of Mn-Fe (hydr-)oxides and clay minerals 2017 In: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533. ; 199, s. 370-389 Journal article (peer-reviewed)abstract This study focuses on the mechanisms of Ce sequestration and accumulation in the fracture network of the upper kilometer of the granitoid bedrock of the Baltic Shield in southeast Sweden (Laxemar area, Sweden). The material includes 81 specimens of bulk secondary mineral precipitates ("fracture coatings") collected on fracture walls identified in 17 drill cores, and 66 groundwater samples collected from 21 deep boreholes with equipment designed for retrieval of representative groundwater at controlled depths. The concentrations of Ce in the fracture coatings, although varying considerably (10-90th percentiles: 67-438 mg kg(-1)), were frequently higher than those of the wall rock (10-90th percentiles: 70-118 mg kg(-1)). Linear combination fitting analysis of Ce L-III-edge X-ray absorption near-edge structure (XANES) spectra, obtained for 19 fracture coatings with relatively high Ce concentrations (>= 145 mg kg(-1)) and a wide range of Ce-anomaly values, revealed that Ce(IV) occurs frequently in the upper 10 m of the fracture network (Ce(IV)/Ce-total = 0.06-1.00 in 8 out of 11 specimens) and is mainly associated with Mn oxides (modeled as Ce oxidatively scavenged by birnessite). These features are in line with the strong oxidative and sorptive capacities of Mn oxide as demonstrated by previous studies, and abundant todorokite and birnessite-like Mn oxides identified in 3 out of 4 specimens analyzed by Mn K-edge X-ray absorption spectroscopy (XAS) in the upper parts of the fracture network (down to 5 m). For a specimen with very high Ce concentration (1430 mg kg(-1)) and NASC-normalized Ce anomaly (3.63), the analysis of Ce XANES and Mn XAS data revealed (i) a predominance of Ce oxide in addition to Ce scavenged by Mn oxide; and (ii) a large fraction of poorly-crystalline hexagonal birnessite and aqueous Mn2+, suggesting a recent or on-going oxidation of Mn2+ in this fracture. In addition, the Ce oxide precipitates on this fracture observed by in situ SEM-EDS contained considerable amounts of Mn. These spectroscopic and microscopic features led us to suggest that the remarkable accumulation of Ce(IV) in this fracture is a result of repeated formation and dissolution of Mn oxides, that is, formation of Mn oxide followed by oxidative scavenging of Ce as Ce oxide nanoparticles, which largely remained during the subsequent reductive dissolution of the Mn oxides. In addition, the XANES data indicate that goethite has the capability to oxidize Ce at near-neutral pH under our experimental conditions (goethite reacted with 0.001M Ce for 48 h in a glove box with O-2 < 1 ppm). This previously unrecognized Ce oxidation pathway also seems to contribute to a minor extent to the oxidative scavenging of Ce in the fracture network. Trivalent Ce in the fracture coatings, in particular below 2.5 m, is mainly sorbed as inner-sphere complexes on clay minerals. Taking into account the facts that Ce in the present groundwater is scarce and modeled to be largely complexed with humic substance, it is argued that the inner-sphere complexes were mainly formed from past (Paleozoic) hydrothermal fluids. (C) 2016 Elsevier Ltd. All rights reserved.
47.	Yu, Changxun, 1983-, et al. (author) Cerium Sequestration in Fractures in the Upper Kilometer of Granitoids, SE, Sweden 2013 In: Mineralogical magazine. - : Cambridge University Press. - 0026-461X .- 1471-8022. ; 77:5, s. 2568-2568 Journal article (peer-reviewed)abstract This study seeks to define geochemical processes governing the accumulation and sequestration of Ce in granitoidic fractures down to >700 m depth, revealing past intrusions of oxygenated waters. The fracture coatings (secondary mineral precipitates in open fractures) gathered from the study area (Laxemar, SE Sweden) are characterized by high levels of Ce (Fig. 1b) compared to host rock cocentration (average: 86 ppm, n=65) and show a striking feature of distinct positive Ce anomalies (CeWN=1.21-3.95, n=8) in the uppermost 20 m of the bedrock (Fig. 1a). Cerium and Mn X-ray absorption spectroscopy (XAS) of selected fracture coatings, together with existing data (e.g. fracture mineralogy and groundwater chemistry), indicate that: (1) Ce(IV) occurs down to c.a. 70 m depth and is exclusively associated with Mn oxides which occur as todorokite and triclinic birnessite as suggested by Mn EXAFS spectra; (2) Since Mn is largely speciated as Mn2+ in the present bedrock groundwaters, the Ce(IV)-bearing Mn oxides most probably resulted from oxidative weathering of wall rock and fracture coating minerals when oxygenated waters intruded into the bedrock (down to several hundred meters depth) during deglacation events (>13000 BP); (3) Unlike other samples, clear XAS features of a poorly-crystalline hexagonalbirnessite-like phase and larger proportion of aqueous Mn2+ were observed in the sample with strikingly positive Ce anomaly (CeWN = 3.95) (Fig. 1b) at the depth of 0.87 m, suggesting an ongoing dynamic accumulatinon of Ce(IV), i.e. dissolution and reprecipiation of Mn oxides while Ce(IV)- enriched residue largely remained.
48.	Yu, Changxun, et al. (author) Effect of weathering on abundance and release of potentially toxic elements in soils developed on Lower Cambrian black shales, P. R. China 2012 In: Environmental Geochemistry and Health. - : Springer. - 0269-4042 .- 1573-2983. ; 34:3, s. 375-390 Journal article (peer-reviewed)abstract This paper examines the geochemical features of 8 soil profiles developed on metalliferous black shales distributed in the central parts of the South China black shale horizon. The concentrations of 21 trace elements and 8 major elements were determined using ICP-MS and XRF, respectively, and weathering intensity (W) was calculated according to a new technique recently proposed in the literature. The data showed that the black shale soils inherited a heterogeneous geochemical character from their parent materials. A partial least square regression model and EFbedrock (enrichment factor normalized to underlying bedrock) indicated that W was not a major control in the redistribution of trace metals. Barium, Sn, Cu, V, and U tended to be leached in the upper soil horizons and trapped by Al and Fe oxides, whereas Sb, Cd, and Mo with negative EF values across the whole profiles may have been leached out during the first stage of pedogenesis (mainly weathering of black shale). Compared with the Chinese average soils, the soils were strongly enriched in the potentially toxic metals Mo, Cd, Sb, Sn, U, V, Cu, and Ba, among which the 5 first listed were enriched to the highest degrees. Elevated concentrations of these toxic metals can have a long-term negative effect on human health, in particular, the soils in mining areas dominated by strongly acidic conditions. As a whole, the black shale soils have much in common with acid sulfate soils. Therefore, black shale soils together with acid sulfate soils deserve more attention in the context of metal exposure and human health.
49.	Yu, Changxun, 1983-, et al. (author) Geochemical controls on dispersion of U and Th in Quaternary deposits, stream water, and aquatic plants in an area with a granite pluton 2019 In: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 663, s. 16-28 Journal article (peer-reviewed)abstract The weathering of U and/or Th rich granite plutons, which occurs worldwide, may serve as a potentially important, but as yet poorly defined source for U and Th in (sub-)surface environments. Here, we assessed the impact of an outcrop of such granite (5 km in diameter) and its erosional products on the distribution of U and Th in four nemo-boreal catchments. The results showed that (i) the pluton was enriched in both U and Th; and (ii) secondary U and Th phases were accumulated by peat/gyttja and in other Quaternary deposits with high contents of organic matter. Movement of the ice sheet during the latest glaciation led to dispersal of U- and Th-rich materials eroded from the pluton, resulting in a progressive increase in dissolved U and Th concentrations, as well as U concentrations in aquatic plants with increasing proximity to the pluton. The accumulation of U in the aquatic plants growing upon the pluton (100–365 mg kg−1, dry ash weight) shows that this rock represents a long-term risk for adjacent ecosystems. Dissolved pools of U and Th were correlated with those of dissolved organic matter (DOM) and were predicted to largely occur as organic complexes. This demonstrates the importance of DOM in the transport of U and Th in the catchments. Large fractions of Ca2UO2(CO3)30(aq) were modeled to occur in the stream with highest pH and alkalinity and thus, explain the strongly elevated U concentrations and fluxes in this particular stream. In future climate scenarios, boreal catchments will experience intensified runoff and warmer temperature that favor the production of hydrologically accessible DOM and alkalinity. Therefore, the results obtained from this study have implications for predicting the distribution and transport of Th and U in boreal catchments, especially those associated with U and/or Th rich granite plutons.
50.	Yu, Changxun, et al. (author) Iron behavior in a northern estuary: Large pools of non-sulfidized Fe(II) associated with organic matter 2015 In: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 413, s. 73-85 Journal article (peer-reviewed)abstract The estuaries of the Northern Baltic Sea (Gulf of Bothnia) receive an abundance of diagenetically reactive catchment-derived Fe, which is to a large degree complexed with organicmatter or present as Fe (hydr-) oxides. However, our understanding of sedimentary Fe diagenesis in these estuaries is limited. To address this limitation, the present study examines Fe geochemistry in a 3.5-m-thick estuarine benthic mud layer and three samples of suspended particulate matter of a catchment on the eastern Gulf of Bothnia. The age-depth model of the mud, constructed on the basis of sedimentary features as well as Cs-137 and aquatic plant C-14 determinations, revealed a high average rate of sedimentation (5 cm . yr(-1)) for the upper mud unit (0-182.5 cm, corresponding to 1973-2011), in response to intensive land-use (ditching) in the catchment since the 1960s and 1970s. The intensive land-use has resulted in a strong increase in the Fe accumulation rates, but has not caused a recognizable impact on the diagenetic processes of Fe including features such as degree of sulfidization and solid-phase partitioning. Iron X-ray absorption spectroscopy (XAS) indicated that in the suspended particulate matter, large proportions (47-58%) of Fe occur as Fe(III)-organic complexes and 2-line ferrihydrite. In the mud, the former is completely reduced, and reactive Fe (defined via extraction with 1 MHCl) was high throughout (52-68%, median = 61%) and strongly dominated by Fe(II). This reactive Fe(II) pool was sulfidized to only a limited extent (degree of reactive sulfidization = 11-26%, median = 17%). This phenomenon is attributed to the brackish-water conditions (i.e. low in sulfate) and the abundant input of reactive Fe(III) from the catchment, leading to a surplus of dissolved Fe2+ over dissolved sulfide in the sediment. The low availability of dissolved sulfide, in combination with the high average sedimentation rate, limits the formation of intermediate reduced sulfur compounds at the water-sediment interface, thereby retarding the conversion of FeS into pyrite (ratios of pyrite-S to AVS = 0.17-1.73, median = 0.37; degree of pyritization = 1-17%, median = 3%). Iron XAS, in combination with wavelet transform analysis, of representative sediment segments from the upper and lower mud units suggests that the non-sulfidized Fe(II) pool is dominantly complexed by organic matter, with the remaining Fe(II) occurring as mackinawite. This has implications for the understanding of early Fe diagenesis in settings with a high input of organic matter and relatively low supply of sulfate. (C) 2015 Elsevier B.V. All rights reserved.

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Author/Editor: Yu, Changxun, 1983- (50); Song, Zhaoliang (31); Åström, Mats E., 196 ... (21); Wang, Hailong (17); Yu, Changxun (16); Peltola, Pasi (12); show more...; Hao, Qian (10); Van Zwieten, Lukas (10); Xia, Shaopan (10); Åström, Mats E. (9); Yang, Xiaomin (8); Liu, Hongyan (7); Zhang, Xiaodong (7); Wang, Yidong (7); Hogmalm, Johan, 1979 (6); Djerf, Henric (6); Guo, Laodong (5); Dopson, Mark, 1970- (5); Åström, Mats (5); Drake, Henrik (5); Drake, Henrik, 1979- (5); Liu, Cong-Qiang (5); Xie, Shurong (5); Li, Qiang (4); Peng, Bo (4); Ghahfarokhi, Sina (4); Yang, Shilei (4); Ran, Xiangbin (4); Chen, Chunmei (4); Wang, Weiqi (4); Shahabi-Ghahfarokhi, ... (4); Wu, Yuntao (4); Boily, Jean-Francois (3); Sohlenius, Gustav (3); Virtasalo, J. J. (3); Berger, Tobias (3); Ketzer, João Marcelo (3); Johnson, Anders (3); Högfors-Rönnholm, Ev ... (3); Österholm, Peter (3); Hartley, Iain P. (3); Ketzer, Marcelo (3); Han, Guilin (3); Fang, Yunying (3); Virtasalo, Joonas J. (3); Nyman, Alexandra (3); Song, Alin (3); Osterholm, P (3); Nystrand, Miriam I. (3); Ojala, A. E. K. (3); show less...

University: Linnaeus University (61); University of Gothenburg (6); Kristianstad University College (6); Umeå University (5); Stockholm University (3); Lund University (2); show more...; Örebro University (1); Swedish Environmental Protection Agency (1); Swedish University of Agricultural Sciences (1); show less...

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