| 1. |
- Bauer, Susanne, et al.
(författare)
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Distribution of dissolved and suspended particulate molybdenum, vanadium, and tungsten in the Baltic Sea
- 2017
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Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 196, s. 135-147
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Tidskriftsartikel (refereegranskat)abstract
- In natural waters, dissolved oxyanions often dominate over the particle-bound element fraction. Still, the scavenging of oxyanions by suspended particles might contribute significantly to their dynamic cycling and distribution. To investigate how oxyanions are affected by manganese (Mn) redox cycling, detailed depth profiles across the pelagic redox zone at the Landsort Deep, Baltic Sea, were collected for molybdenum (Mo), vanadium (V), and tungsten (W), for both dissolved (<0.22 µm) and suspended particulate (>0.22 µm) fractions.All three oxyanions show a non-conservative behavior in the stratified Landsort Deep. Strong linear correlations with Mn in the particulate fraction in the redox zone of the Landsort Deep suggest that Mn redox cycling influences their distribution. In the dissolved fraction, Mo, V, and W exhibited rather different behavior. Molybdenum was depleted below the redox zone, while V was depleted only within the redox zone. Tungsten concentrations increased within the redox zone, being three times higher in the sulfidic zone than in the surface water. Unlike Mo, W shows no tendency for adsorption or co-precipitation under the prevailing weak sulfidic conditions in the deep water of the Landsort Deep and is, therefore, not exported to the underlying sediment.The Landsort Deep data were compared with data from the northern Baltic Sea (Bothnian Bay, Kalix River and Råne River estuaries), where particulate iron (Fe) occurs in high abundance. The particulate fractions of Mo, V, and W decreased during mixing in these estuaries. Vanadium showed the most drastic reduction, with a decrease in dissolved and particulate fractions, indicating that different processes influence the distribution of these oxyanions.
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| 2. |
- Cai, Minggang, et al.
(författare)
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Concentrations, distribution and sources of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls in coastal sediments from Xiamen, China
- 2016
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 185, s. 74-81
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Tidskriftsartikel (refereegranskat)abstract
- Xiamen and its surroundings are representative areas suffering from intense anthropogenic turbulence and contamination in southeast coast of China during rapid industrialization and urbanization period, thus relevant organic pollutants research is necessary to assess the coastal environmental quality and generate management strategy. Contamination status of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin like polychlorinated biphenyls (DL-PCBs) was investigated for 7 surface sediment samples collected in these areas in January 2007. The given data were used to evaluate the contamination and their potential risks of the pollutants. Concentrations of PCDD/Fs were in the range of 60 to 4089 pg g(-1) (dry weight) with an average of 1706 pg g(-1) and DL-PCBs in the range of 3 to 76 pg g(-1) with an average of 28 pg g(-1). Octa-chlorinated dibenzo-p-dioxin (OCDD) and PCBs 105 and 118 were the main congeners of the PCDD/F and DL-PCB, respectively. The toxicity equivalent concentrations (TEQs) were in the range of 0.15 to 5.2 pg g(-1) (average: 3.0 pg g(-1)) for PCDD/Fs, while in the range of
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| 3. |
- Gallego-Urrea, Julian A., 1977, et al.
(författare)
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Determination of pH in estuarine and brackish waters: Pitzer parameters for Tris buffers and dissociation constants for m-cresol purple at 298.15K
- 2017
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 195, s. 84-89
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Elsevier B.V. Measurements of pH in seawater are important to determine the natural and anthropogenic trends in the oceans. Spectrophotometry or glass electrode potentiometry measurements of pH require calibration with help of buffers. One common buffer solution is the Tris/Tris·H + couple, which should be well characterised both experimentally and theoretically for optimum accuracy. Chemical speciation modelling in the complex seawater medium is best addressed with an ion interaction approach, with Pitzer equations being the most widely used. The published Pitzer coefficients for Tris and Tris·H + in artificial seawater are based on isopiestic measurements, which necessarily give strong weight to the third virial coefficient C for the key interaction between Tris·H + and chloride. However, in low salinity waters it is the second virial coefficient B that is of greater importance. We have used Harned cell measurements of Tris solutions at ionic strengths up to 1molkg -1 to reassess the relevant Pitzer parameters, and have found improved agreement with experimental measurements in artificial seawater. We suggest that additional measurements should be undertaken to address the remaining differences between model calculations and experimental data in artificial seawater. We have used the revised Pitzer parameters to reassess the acid-base constant of the indicator m-cresol purple in low salinity waters.
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| 4. |
- Gdaniec, Sandra, et al.
(författare)
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Thorium and Protactinium isotopes as tracers of marine particle fluxes and deep water circulation in the Mediterranean Sea
- 2018
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Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 199, s. 12-23
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Tidskriftsartikel (refereegranskat)abstract
- 231Pa, 230Th and 232Th were analyzed in unfiltered sea water samples (n = 66) and suspended particles (n = 19) collected in the Mediterranean Sea during the MedSeA-GA04-S cruise along the GEOTRACES section GA04S and used to investigate mechanisms controlling the distribution and fractionation of Pa and Th in an ocean margin environment. 231Pa and230Th are particle reactive radionuclides and are often used astracers of processes such as boundary scavenging, particle transport and ocean circulation. The depth profiles of total 231Pa and 230Th concentrations in the Mediterranean Sea displayed non-linear shapes. Higher total 232Th concentrations were observed at the straits and in deepwaters pointing at lithogenic sources. Fractionation factors FTh/Pa ranged from 1.4 to 9. Application of a box-model illustrated that 94 % of the 231Pa and almost all of the 230Th (99.9 %) produced in the Mediterranean Sea is removed to the sediment by scavenging. The negligible export of 230Th to the Atlantic Ocean, leads to a reevaluation of the mean settling speed of the filtered particles, which is now estimated to 500-1000 m/y. The low FTh/Pa fractionation factors are attributed to the efficient scavenging and lack of transport of 231Pa to the Atlantic Ocean.
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| 5. |
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| 6. |
- Illuminati, S., et al.
(författare)
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In-situ trace metal (Cd, Pb, Cu) speciation along the Po River plume (Northern Adriatic Sea) using submersible systems
- 2019
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 212, s. 47-63
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Tidskriftsartikel (refereegranskat)abstract
- Information on the distribution and speciation of trace metals is of critical importance for our ability to interpret the links between the bioavailability and uptake of an element, and its biogeochemical cycle in coastal environments. Within the framework of the European Project "In-situ automated Monitoring of Trace metal speciation in Estuaries and Coastal zones in relation with the biogeochemical processes (IMTEC)", the chemical speciation of Cd, Pb and Cu was carried out along the Po River plume in the period 27 October - 2 November 2002. During the cruise, five Voltammetric In-situ Profiling systems and one Multi Physical Chemical Profiler, as well as conventional voltammetric instruments, were successfully applied in order to evaluate the distribution of Cd, Pb and Cu between different fractions (free ion, dynamic, colloidal, dissolved and particulate fractions) and to assess the evolution of these fractions during estuarine mixing and in the water column. Dynamic concentrations were 0.05-0.2 nmol L-1 Cd, 0.02-0.2 nmol L-1 Pb, and 0.15-4.0 nmol L-1 Cu. Cd was mainly present as dynamic fraction (40-100% of the dissolved Cd). High proportions of Pb (similar to 70%) and Cu (similar to 80%) were present as colloids probably of biogenic origin. Principal components analysis reveals a strong influence of the Po River discharge on the spatial and vertical distributions of metal species. Almost all the metal fractions globally decreased following the salinity gradient. Metal concentrations are far below (at least one order of magnitude lower) the Environmental Quality Standard established by the Italian law. However, the Cu dynamic fraction showed concentrations likely to be toxic to sensitive phytoplankton community and to have negative effects on larva development of coastal macroinvertebrate species (toxicity data extracted from literature).
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| 7. |
- Karlsson, Emma S., et al.
(författare)
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Contrasting regimes for organic matter degradation in the East Siberian Sea and the Laptev Sea assessed through microbial incubations and molecular markers
- 2015
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 170, s. 11-22
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Tidskriftsartikel (refereegranskat)abstract
- Compositional studies of organic matter on the East Siberian Arctic Shelf (ESAS) suggest that different terrestrial carbon pools have different propensities for transport and/or degradation. The current study combined laboratory-based microbial degradation experiments with earlier published degradation-diagnostic composition of several classes of terrestrial biomarkers on the same sediments to investigate differences and driving forces of terrestrial organic matter (TerrOM) degradation in two biogeochemically-contrasting regimes of the ESAS. The incubation-based anaerobic degradation rates were consistently higher (by average factor of 6) in the East Siberian Sea Kolyma Paleoriver Channel (ESS-KPC) (15 mu mol CO2 g OC-1 day(-1)) compared to the Laptev Sea Buor-Khaya Bay (LS-BKB) (2.4 mu mol CO2 g OC-1 day(-1)). The reported molecular markers show similarities between the terrestrial carbon pools in the two systems, but impose contrasting degradation regimes in combination with the incubation results. For the LS-BKB, there was a strong relationship between the degradation rates and the three lignin phenol-based degradation proxies (r(2) = 0.93-0.96, p < 0.01, linear regression) and two wax lipid-based degradation proxies (r(2) = 0.71 and 0.66, p < 0.05, linear regression). In contrast, for the ESS-KPC system, there was no relationship between incubation-based degradation rates and molecular marker-based degradation status of TerrOM. A principal component analysis indicated that short-chain fatty acids and dicarboxylic acids from CuO oxidation are mainly of terrestrial origin in the LS-BKB, but mainly of marine origin in the ESS-KPC. Hence, the microbial degradation in the western (LS-BKB) system appears to be fueled by TerrOM whereas the eastern (ESS-KPC) system degradation appears to be driven by MarOM. By combining molecular fingerprinting of TerrOM degradation state with laboratory-based degradation studies on the same ESAS sediments, a picture evolves of two distinctly different modes of TerrOM degradation in different parts of the ESAS system.
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| 8. |
- Krall, Lindsay, et al.
(författare)
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Submarine groundwater discharge at Forsmark, Gulf of Bothnia, providedby Ra isotopes
- 2017
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Ingår i: Marine Chemistry. - Amsterdam : Elsevier. - 0304-4203 .- 1872-7581. ; 196, s. 162-172
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Tidskriftsartikel (refereegranskat)abstract
- Submarine groundwater discharge (SGD) to the Gulf of Bothnia, Baltic Sea, has been believed to be insignificant from hydrological models, yet geochemical investigations of SGD in this basin are limited. In this study, 223Ra, 224Ra, 226Ra, and 228Ra have been complemented by stable δ18O and d2H isotopes to characterize and quantify SGD rates from the coast of Forsmark, Sweden to Öregrundsgrepen Strait (Gulf of Bothnia). In shallow bays, SGD has been traced using relations between Ra, d2H and d18O isotopes and salinity. Zonal SGD from deformation zones, expressed as hydraulically conductive fractures, overlain by the Börstilåsen esker, a strip of conductive gravel sediment, have been traced through offshore 224Raxs and 226Ra trends. On the basis of a 224Raxs mass balance, the SGD flow rate ranges from (5.5 ± 3.0) · 103 m3 d-1 to (950 ± 520) · 103 m3 d-1. These rates are up to two orders of magnitude higher than those determined from local hydrological models, which consider only the fresh component of SGD. From the divergence between the hydrological and 224Raxs models, it is inferred that the site is influenced by a component of recirculated seawater.
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| 9. |
- Kumar Ranjan, Rajesh, et al.
(författare)
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Sediment biomarker profiles trace organic matter input in the Pichavaram mangrove complex, southeastern India
- 2015
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Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 171, s. 44-57
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Tidskriftsartikel (refereegranskat)abstract
- The nature and distribution of lipid biomarkers (n-alkanes, n-alkanols, sterols and triterpenols) were investigated in five dated sediment cores from the Pichavaram mangrove-estuarine complex in order to: 1) identify the organic matter (OM) sources and its preservation and 2) trace recent changes associated with coastal processes and anthropogenic activities. The mangrove sediment extracts have higher biomarker concentration (22.6 +/- 13.3 mu g/g dry weight) than the estuarine extracts (6.42 +/- 4.92 mu g/g dry weight). Triterpenols are dominant biomarkers in both estuarine and mangrove sediments, and constitute greater than50% of the total lipid extracts. The presence of n-alkanols (n-C-26,C-28,C-30) and abundance of phytosterols (stigmasterol and beta-sitosterol) and triterpenols (taraxerol, beta-amyrin, germanicol, and lupeol) indicate that mangrove vegetation is the primary source of sedimentary OM. The high abundance and unimodal distribution of the long-chain n-alkanes (mainly n-C-25,C-27,C-29), and high values of Terrestrial Aquatic Ratio (TAR 2.4 to 41) and Carbon Preference Index (CPI greater than 8) indicate dominance (and better preservation) of higher plant derived immature OM in mangrove sediments. In contrast the weak dominance of high molecular weight n-alkanes, low CPI (0.75 to 0.90) and TAR (1.9 to 5.7) values, and the presence of high C-27 and C-28 sterols indicate that phytoplankton/algal derived OM is more pronounced in estuarine sediments. Diagenetic changes in sedimentary OM indicate that some of the lipid fractions are reactive, and as a result, they degrade more rapidly than bulk OM. These compounds follow first order decay kinetics, and concur with the downcore diagenetic changes in coastal areas. Resistance to degradation among the different lipid classes show the trend: n-alkane greater than sterol greater than triterpenol greater than n-alkanol. Finally, the study indicates that less freshwater discharge from the Coleroon River is causing a gradual change in mangrove vegetation. There is less input of OM derived from mangrove vegetation into recent sediments. Biomarker trends also indicate that less salt tolerant Rhizophora spp. are gradually replaced by more salt tolerant vegetation consisting of Sueda spp. and Aviccenia spp.
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| 10. |
- Nerentorp, Michelle, 1986, et al.
(författare)
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Mercury flux over West Antarctic Seas during winter, spring and summer
- 2017
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 193, s. 44-54
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Tidskriftsartikel (refereegranskat)abstract
- For the first time elemental mercury in air and surface seawater was measured continuously in the remote seas of western Antarctica. A major contributor to atmospheric emissions of the toxic and globally dispersed pollutant mercury is the re-evasion from water surfaces, due to a supersaturation of dissolved gaseous mercury (DGM) in surface water. In this study the degree of saturation and mercury flux at the air-sea surface interface have been estimated from continuous measurements of gaseous elemental mercury (GEM) or total gaseous mercury (TGM) in air, DGM in surface water and meteorological parameters. The measurements were performed during winter and spring (2013) in the Weddell Sea and during summer (2010/2011) in the Bellingshausen, Amundsen and Ross Seas, and show spatial and seasonal variations. The average DGM concentration in surface water in open sea was highest during spring (12 +/- 7pg L-1) and lowest during summer (7 +/- 6.8 pg L-1), resulting in a net evasion of mercury during spring (1.1 +/- 1.6 ng m(-2)h(-1)) and a net deposition during summer (-0.2 +/- 1.3 ng m(-2)h(-1)). In open sea, higher average concentrations of GEM (or TGM) and DGM were found close to the Drake Passage compared to in the Bellingshausen and Weddell Seas. Emission sources from the South American continent, identified with back trajectories, were suggested to explain the observed variations. The yearly mercury evasion from open sea surfaces in the Southern Ocean was estimated to 30 ( -450-1700) tons, using the average (and min and max) flux rates obtained in this study. Higher DGM was measured under sea ice (19-62 pg L-1 compared to in open sea due to a capsuling effect, resulting in a theoretical prevented evasion of 520 (0-3400) tons per year. Diminishing sea ice and higher water temperatures in polar regions could result in increased mercury evasion to the atmosphere. However, the contribution of the Southern Ocean to the global modeled annual emissions of mercury from sea surfaces would probably only be a few percent.
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