| 1. |
- Balzer, Laura, et al.
(författare)
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Role of formation and decay of seston organic matter in the fate of methylmercury within the water column of a eutrophic lake
- 2023
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Ingår i: Biogeosciences. - 1726-4170 .- 1726-4189. ; 20:7, s. 1459-1472
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Tidskriftsartikel (refereegranskat)abstract
- Anoxic microniches in sinking particles in lakes have been identified as important water phase production zones of monomethylmercury (MeHg). However, the production and decay of MeHg during organic matter (OM) decomposition in the water column and its relation to the total Hg concentration in seston are poorly understood. We investigated total Hg and MeHg in relation to chemical changes in sinking seston and hydrochemical settings in a small and shallow (12 m deep) eutrophic lake during phytoplankton blooms from April to November 2019. The results show that MeHg proportions reach up to 22 % in seston in oxygen super saturation at the water surface and highest values (up to 26 %) at the oxic–suboxic redox boundary. MeHg concentrations were highest in May and November when algal biomass production was low and seston were dominated by zooplankton. Biodilution of MeHg concentrations could not be observed in the months of the highest algal biomass production; instead, MeHg and THg concentrations in seston were comparatively high. During suboxic OM decomposition and with decreasing redox potential (Mn and nitrate reduction), the concentration and proportion of MeHg in seston strongly decreased (<0.5 %), whereas total Hg concentrations show a 3.8- to 26-fold increase with water depth. Here, it remains unclear to which extent biodilution on the one hand and OM decomposition on the other alter the MeHg and THg concentration in seston. Changes in OM quality were most intense within or slightly below the redox transition zone (RTZ). The concentrations of MeHg and THg in seston from the RTZ were comparable to those found in the sediment trap material which integrated the changes in seston composition during the entire sampling period, suggesting that changes in the MeHg and THg content in the hypolimnion below the RTZ are comparatively small. Our study suggests that, in shallow eutrophic lakes, the water phase formation and decomposition of MeHg is intense and controlled by the decomposition of algal biomass and is, assumedly, largely disconnected from Hg methylation in sediments, similar to what has been observed in deep oligotrophic lakes.
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| 2. |
- Biester, Harald, et al.
(författare)
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Mercury in mires
- 2006
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Ingår i: Peatlands. - : Elsevier. - 9780080468051 - 9780444528834 ; , s. 465-478
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Bokkapitel (refereegranskat)abstract
- This chapter illustrates that a better understanding of the behavior of mercury in the environment is needed for a number of reasons. For example, increased biomagnification of mercury in aquatic food chains, especially in fish, and enhanced accumulation in remote areas such as the Arctic have been observed in the last few decades. Mercury toxicity in aquatic ecosystems is of particular concern, with the role of methylmercury (MeHg) being critical. This compound can be concentrated by more than a million times in the aquatic food chain. Biogeochemical studies and monitoring programs that include direct measurements of wet deposition or indirect measurements based on biomonitoring of forest mosses, have established that anthropogenic activities have affected the global cycling of mercury. Although a precise link has yet to be made between the increased content of mercury in biota and the increased accumulation rates observed in natural environmental archives, such as peat, lake sediments, and glacial ice, there is broad consensus that these archives provide a means to reconstruct atmospheric deposition trends at local, regional, and global scales.
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| 3. |
- Biester, Harald, et al.
(författare)
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Modeling the Past Atmospheric Deposition of Mercury Using Natural Archives
- 2007
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 41:14, s. 4851-4860
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Tidskriftsartikel (refereegranskat)abstract
- Historical records of mercury (Hg) accumulation in lake sediments and peat bogs are often used to estimate human impacts on the biogeochemical cycling of mercury. On the basis of studies of lake sediments, modern atmospheric mercury deposition rates are estimated to have increased by a factor of 3-5 compared to background values: i.e., from about 3-3.5 g Hg m-2 yr-1 to 10-20 g Hg m-2 yr-1. However, recent studies of the historical mercury record in peat bogs suggest significantly higher increases (9-400 fold, median 40×), i.e., from about 0.6-1.7 g Hg m-2 yr -1 to 8-184 g Hg m-2 yr -1. We compared published data of background and modern mercury accumulation rates derived from globally distributed lake sediments and peat bogs and discuss reasons for the differences observed in absolute values and in the relative increase in the industrial age. Direct measurements of modern wet mercury deposition rates in remote areas are presently about 1-4 g m-2 yr -1, but were possibly as high as 20 g Hg m-2 yr -1 during the 1980s. These values are closer to the estimates of past deposition determined from lake sediments, which suggests that modern mercury accumulation rates derived from peat bogs tend to over-estimate deposition. We suggest that smearing of 210Pb in the uppermost peat sections contributes to an underestimation of peat ages, which is the most important reason for the overestimation of mercury accumulation rates in many bogs. The lower background mercury accumulation rates in peat as compared to lake sediments we believe is the result of nonquantitative retention and loss of mercury during peat diagenesis. As many processes controlling time-resolved mercury accumulation in mires are still poorly understood, lake sediments appear to be the more reliable archive for estimating historical mercury accumulation rates.
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| 4. |
- Bindler, Richard, et al.
(författare)
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Copper-ore mining in Sweden since the pre-Roman Iron Age : lake-sediment evidence of human activities at the Garpenberg ore field since 375 BCE
- 2017
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Ingår i: Journal of Archaeological Science. - : Elsevier BV. - 2352-409X .- 2352-4103. ; 12, s. 99-108
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Tidskriftsartikel (refereegranskat)abstract
- Historical documents, archaeological evidence and lake-sediment records indicate thus far that significant mining of iron and copper ores in the Berglsagen mining region in central Sweden did not begin until the late 12th century -first with iron in Norberg - and thereafter spreading rapidly throughout the region during the 13th century when also copper was included (e.g. Falun). Prior to this, iron was produced domestically from secondary sources such as bog iron, while geochemical analyses of bronze artefacts indicate copper was imported. The parish of Garpenberg was at the intersection between historical iron-and copper-mining districts, and consequently we expected our sediment record from the lake Gruvsjon ('mine lake') to follow the established 13th century development. However, a 2-3-fold enrichment in copper and lead occurred already during 375-175 BCE (pre-Roman Iron Age), together with small increases in zinc, magnesium and charcoal particles, and changes in pollen. Together these indicate a clear pattern of human disturbance connected with the ore body bordering the lake. A second distinct phase occurred 115-275 CE, but with an 8-9-fold increase in copper and lead along with other indicators. From 400 CE a permanent increase in copper and lead occurred, which then accelerated from the 13th century as seen elsewhere in the region. Our results push back the evidence for early ore mining in Sweden from the Middle Ages to the pre-Roman Iron Age.
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| 5. |
- Jingying, Xu, 1984-, et al.
(författare)
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Influence of particle size distribution, organic carbon, pH and chlorides on washing of mercury contaminated soil
- 2014
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 109, s. 99-105
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Tidskriftsartikel (refereegranskat)abstract
- Feasibility of soil washing to remediate Hg contaminated soil was studied. Dry sieving was performed to evaluate Hg distribution in soil particle size fractions. The influence of dissolved organic matter and chlo- rides on Hg dissolution was assessed by batch leaching tests. Mercury mobilization in the pH range of 3– 11 was studied by pH-static titration. Results showed infeasibility of physical separation via dry sieving, as the least contaminated fraction exceeded the Swedish generic guideline value for Hg in soils. Soluble Hg did not correlate with dissolved organic carbon in the water leachate. The highest Hg dissolution was achieved at pH 5 and 11, reaching up to 0.3% of the total Hg. The pH adjustment was therefore not suf- ficient for the Hg removal to acceptable levels. Chlorides did not facilitate Hg mobilization under acidic pH either. Mercury was firmly bound in the studied soil thus soil washing might be insufficient method to treat the studied soil.
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| 6. |
- Karlsson, Jon, et al.
(författare)
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Tracing a bog-iron bloomery furnace in an adjacent lake-sediment record in Ängersjö, central Sweden, using pollen and geochemical signals
- 2016
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Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 25:6, s. 569-581
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies of bloomery sites in Sweden indicate the amount of iron produced with this early low-technology smelter was greater than previously thought, which implies greater economic importance. Little is known about the history of bloomery technology, not least the timeframe over which individual bloomeries were operated, as well as their impact on the landscape because of resource consumption and pollution. In this study we performed pollen and geochemical analyses of the lake-sediment record from Rortjarnen, which is 120 m from the remains of a documented bloomery [one radiocarbon date: ad 1300-1435 (1 sigma)], in A"ngersjo, Halsingland. A surface-soil transect shows a limited geochemical signal only within 20 m of the bloomery, and the sediment pollen record provides little direct evidence of an active bloomery and is consistent with other studied sites in the area linked to forest grazing or cultivation. Instead, we find major changes in sediment geochemistry during ad 800-1200, centered on a unique peak in Pb at ad 1030-1060. These changes include, e.g., Si (biogenic) and P, together with changes in pollen (e.g., Betula, Picea, Cyperaceae), which together indicate disturbance in the forest and especially the adjoining fen. We attribute these changes to a period of bloomery-related activities predating the radiocarbon date of the charcoal from the bloomery, and suggest that date represents a late phase for the site.
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| 7. |
- Moreno-Brush, Monica, et al.
(författare)
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Is mercury from small-scale gold mining prevalent in the southeastern Peruvian Amazon?
- 2016
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 218, s. 150-159
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Tidskriftsartikel (refereegranskat)abstract
- There is an ongoing debate on the fate of mercury (Hg) in areas affected by artisanal and small-scale gold mining (ASGM). Over the last 30 years, ASGM has released 69 tons of Hg into the southeastern Peruvian Amazon. To investigate the role of suspended matter and hydrological factors on the fate of ASGM-Hg, we analysed riverbank sediments and suspended matter along the partially ASGM-affected Malinowski-Tambopata river system and examined Hg accumulation in fish. In addition, local impacts of atmospheric Hg emissions on aquatic systems were assessed by analysing a sediment core from an oxbow lake. Hg concentrations in riverbank sediments are lower (20-53 ng g(-1)) than in suspended matter (similar to 400-4000 ng g(-1)) due to differences in particle size. Elevated Hg concentrations in suspended matter from ASGM-affected river sections (similar to 1400 vs. similar to 30-120 ng L-1 in unaffected sections) are mainly driven by the increased amount of suspended matter rather than increased Hg concentrations in the suspended matter. The oxbow lake sediment record shows low Hg concentrations (64-86 ng g(-1)) without evidence of any ASGM-related increase in atmospheric Hg input. Hg flux variations are mostly an effect of variations in sediment accumulation rates. Moreover, only 5% of the analysed fish (only piscivores) exceed WHO recommendations for human consumption (500 ng g(-1)). Our findings show that ASGM-affected river sections in the Malinowsld-Tambopata system do not exhibit increased Hg accumulation, indicating that the released Hg is either retained at the spill site or transported to areas farther away from the ASGM areas. We suspect that the fate of ASGM-Hg in such tropical rivers is mainly linked to transport associated with the suspended matter, especially during high water situations. We assume that our findings are typical for ASGM-affected areas in tropical regions and could explain why aquatic systems in such ASGM regions often show comparatively modest enrichment in Hg levels.
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| 8. |
- Myrstener, Erik, et al.
(författare)
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Environmental footprint of small-scale, historical mining and metallurgy in the Swedish boreal forest landscape : The Moshyttan blast furnace as microcosm
- 2019
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Ingår i: The Holocene. - : Sage Publications. - 0959-6836 .- 1477-0911. ; 29:4, s. 578-591
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Tidskriftsartikel (refereegranskat)abstract
- The history of mining and smelting and the associated pollution have been documented using lake sediments for decades, but the broader ecological implications are not well studied. We analyzed sediment profiles covering the past similar to 10,000 years from three lakes associated with an iron blast furnace in central Sweden, as an example of the many small-scale furnaces with historical roots in the medieval period. With a focus on long-term lake-water quality, we analyzed multiple proxies including geochemistry, pollen and charcoal, diatom composition and inferred pH, biogenic silica (bSi), visible near-infrared spectroscopy (VNIRS)-inferred lake-water total organic carbon (LW-TOC), and VNIRS-inferred sediment chlorophyll (sed-Chl). All three lakes had stable conditions during the middle Holocene (similar to 5000 BCE to 1110 CE) typical of oligo-dystrophic lakes: pH 5.4-5.6, LW-TOC 15-18 mg L-1. The most important diatom taxa include, for example, Aulacoseira scalaris, Brachysira neoexilis, and Frustulia saxonica. From similar to 1150 CE, decreases in LW-TOC, bSi, and sed-Chl in all three lakes coincide with a suite of proxies indicating disturbance associated with local, small-scale agriculture, and the more widespread use of the landscape in the past (e.g. forest grazing, charcoal production). Most important was a decline in LW-TOC by 30-50% in the three lakes prior to the 20th century. In addition, the one lake (Fickeln) downstream of the smelter and main areas of cultivation experienced a shift in diatom composition (mainly increasing Asterionella formosa) and a 0.6 pH increase coinciding with increasing cereal pollen and signs of blast furnace activity. The pH did not change in the other two lakes in response to disturbance; however, these lakes show a slight increase (0.3-0.5 pH units) because of modern liming. LW-TOC has returned to background levels in the downstream lake and remains lower in the other two.
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| 9. |
- Myrstener, Erik, et al.
(författare)
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Was Moshyttan the earliest iron blast furnace in Sweden? : The sediment record as an archeological toolbox
- 2016
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Ingår i: Journal of Archaeological Science. - : Elsevier. - 2352-409X .- 2352-4103. ; 5, s. 35-44
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Tidskriftsartikel (refereegranskat)abstract
- Recently, archeological study of the establishment and spread of iron blast furnace technology in Sweden has suggested a phase of rapid expansion from AD 1150 to 1350, mainly in the historically important "Bergslagen" region in central Sweden. But the geographical extent and earliest development remains debated. One archeological investigation of Moshyttan, in the less studied western part of Bergslagen, suggested that it may have been established before 1150. To independently study the timing of blast furnace establishment at Moshyttan, and also the vegetation history of the area, we performed a multiproxy analysis of the sediment record from Fickeln, a small lake immediately downstream of the smelter site. We present radiocarbon dating (macrofossils and bulk sediment), pollen, charcoal particles and geochemistry. To establish a reliable age depth model, ages of the bulk samples were corrected for old carbon and the model was validated by comparison to chronological markers (immigration of Picea abies and airborne lead-pollution) in other lakes with varved or otherwise robust chronologies. Based on markedly increasing lead concentrations, decreases in the Pb-206/Pb-207 ratio towards values resembling Bergslagen ores, increasing charcoal particle counts and increases in iron and zinc concentrations, the establishment of the blast furnace is estimated to AD 1250-1300 with an age-depth model probability of 91%. This places the establishment of the blast furnace at Moshyttan within the known period of early expansion of iron blast furnaces in Sweden, rather than earlier as suggested by the earliest dates from the archeological study. The first signs of a human presence in the area can be seen in pollen associated with forest grazing from ca. 170 BC, and the first signs of cultivation appear ca. AD 1020, preceding the blast furnace by 200 years.
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| 10. |
- Schellekens, Judith, et al.
(författare)
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Preferential degradation of polyphenols from Sphagnum-4-Isopropenylphenol as a proxy for past hydrological conditions in Sphagnum-dominated peat
- 2015
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533. ; 150, s. 74-89
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Tidskriftsartikel (refereegranskat)abstract
- The net accumulation of remains of Sphagnum spp. is fundamental to the development of many peatlands. The effect of polyphenols from Sphagnum on decomposition processes is frequently cited but has barely been studied. The central area of the Rodmossamyran peatland (Sweden) is an open lawn that consists mostly of Sphagnum spp. with a very low contribution from vascular plants. In order to determine the effects of decay on sphagnum phenols, 53 samples of a 2.7 m deep core from this lawn were analysed with pyrolysis gas chromatography-mass spectrometry (pyrolysis-GC-MS) and compared with more traditional decomposition proxies such as C/N ratio, UV light transmission of alkaline peat extracts, and bulk density. Factor analysis of 72 quantified pyrolysis products suggested that the variation in 4-isopropenylphenol was largely determined by aerobic decomposition instead of Sphagnum abundance. In order to evaluate the effects of aerobic decay in Sphagnum peat, down-core records from different climatic regions were compared using molecular markers for plant biopolymers and C/N ratio. These included markers for lignin from vascular plants ((di) methoxyphenols), polyphenols from Sphagnum spp. (4-isopropenylphenol), and cellulose (levoglucosan). Our results indicate that polyphenols from Sphagnum are preferentially degraded over polysaccharides; consequently the variability of the marker for sphagnum acid, 4-isopropenylphenol, was found indicative of decomposition instead of reflecting the abundance of Sphagnum remains. The fact that 4-isopropenylphenol is aerobically degraded in combination with its specificity for Sphagnum spp. makes it a consistent indicator of past hydrological conditions in Sphagnum-dominated peat. In contrast, the variability of C/N records in Sphagnum-dominated peat was influenced by both vegetation shifts and decomposition, and the dominant effect differed between the studied peatlands. Our results provide direction for modelling studies that try to predict possible feedback mechanisms between peatlands and future climate change, and indicate that the focus in Sphagnum decay studies should be on carbohydrates rather than on phenolic compounds.
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