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1.
  • Boström, Kurt, et al. (författare)
  • Origin of iron-manganese-rich suspended matter in the Landsort Deep, NW Baltic Sea
  • 1988
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 24:1, s. 93-98
  • Tidskriftsartikel (refereegranskat)abstract
    • Water sampling was undertaken in 1982 in the Landsort Deep, NW Baltic Sea, at eight depth levels. In the 0-150 m interval oxidizing conditions prevailed, with suspended phases being particularly rich in Fe (with a maximum at 150 m), Mn and Ba (with maxima at 100 m). The anoxic zone below 150 m showed high concentrations of dissolved Fe and particularly dissolved Mn which were much higher than in the Black Sea, for instance. This is probably due to the migratory behavior of the redoxcline in the Landsort Deep. The metal-rich suspended matter probably arises when dissolved Fe and Mn from the anoxic zone precipitate as hydroxyoxides at the redoxcline; lateral transport of such suspended matter may explain the large-scale selective loss of Mn and Ba from the Baltic basin.
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2.
  • Boström, Kurt, et al. (författare)
  • Selective removal of trace elements from the Baltic by suspended matter
  • 1981
  • Ingår i: Marine Chemistry. - 0304-4203 .- 1872-7581. ; 10:4, s. 335-354
  • Tidskriftsartikel (refereegranskat)abstract
    • Suspended matter was collected at 30 stations in the Baltic and Kattegatt, at the thermocline and at the bottom, and analysed for Na, Ca, Mg, Si, Ti, Al, Fe, Mn, Ba, Sr, Ni and V. The composition of the suspended matter varies considerably, but can be described as a mixture of: (1) 12-25% terrigenous detritus with much Si, Al, Ti and Fe; (2) 75-88% biological matter with much Ni, V and Ba; and (3) some Mn-oxyhydroxide.The annual efflux of water from the Baltic is about 460 km3, with a suspended load in the Baltic straits of 1.2-3.6 mg ash material l-1 These values imply that much Si, Ti, Al, Fe, Sr, Ni and V and particularly much Ba and Mn are lost from the Baltic in the suspended load.The average suspended matter is richer in Mn(5×), Ba(2.5×), Sr(4×) and V(1.8×) than permanently depositing Baltic sediments. These constituents are relatively enriched in pelagic deposits, i.e. it is likely that much Mn, Ba and V in deep-sea sediments derive from the continents via suspended transport. This conclusion is supported by the similarity between suspended matter and average Atlantic pelagic sediment.
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3.
  • Gustafsson, Örjan, et al. (författare)
  • Colloid dynamics and transport of major elements through a boreal river - brackish bay mixing zone
  • 2000
  • Ingår i: Marine Chemistry. - 0304-4203 .- 1872-7581. ; 71:1-2, s. 1-21
  • Tidskriftsartikel (refereegranskat)abstract
    • A range of biogeochemical methodologies were applied to investigate how aggregation processes affected the phase distribution and mixing of Fe, Si, and organic carbon between the Kalix River and the Bothnic Bay, northernmost Baltic Sea (salinity≤3; the low-salinity zone (LSZ) was stretching over 60 km in the spring). During the dynamic springflood conditions studied, small 238U-234Th disequilibria, low sediment trap fluxes, laboratory mixing experiments, as well as results from an independent two-box, two-dimensional mixing model combine to suggest that no significant removal of Fe, Si, or organic C was occurring in the highly-resolved LSZ. While no conclusions may be drawn based solely on property-salinity plots over narrow salinity ranges, apparently linear graphs for Fe and Si over 3 separate years also suggest minimal removal in this regime. At the same time, size distributions both of elements -from cross-flow ultrafiltration - and of bulk suspended solids - from light scattering (photon correlation spectroscopy [PCS]) - indicated that significant aggregation was taking place.The aggregation-without-significant-settling scenario in this low-salinity mixing regime, with a geochemistry similar to that of neighboring Russian Arctic rivers, is hypothesized to result from a comparatively high organic-to-detrital matter characteristic of the aggregates. While first principles would indeed suggest that decreasing electrostatic repulsion during mixing lead to aggregation, a low specific density of mineral-poor amorphous organic aggregates may lead to transport of these authigenic particles further away from the river mouth. The role of detrital "sinkers" on vertical removal of suspended organic matter is discussed in the wider context of scavenging mechanisms in the ocean.
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4.
  • Ingri, Johan, et al. (författare)
  • Chemistry of suspended particles in the southern Baltic Sea
  • 1991
  • Ingår i: Marine Chemistry. - 0304-4203 .- 1872-7581. ; 32:1, s. 73-87
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissolved and suspended concentrations of Al, Ba, Fe, Mn, and Si and suspended P and Ti have been studied in the Baltic proper, the Belt Sea-Kattegat and the Åland Sea. Approximately 20% of total Al, Fe and Mn, 75% of total Si and 99% of total Ba passed a 0.45-μm filter in subsurface water from the Baltic proper. The suspended phase can be divided into three major components, a detrital, a Mn rich and an organic phase. Suspended Al, Ti and most Fe were present in detrital particles. Approximately 50% of suspended Si was detrital while the amount of P in the detrital component was negligible. Suspended P showed a positive correlation to the non-detrital Fe concentration. Non-detrital Mn was strongly enriched in the suspended phase. In some samples 50% of the ashed suspended load was Mn. The Mn-rich particles originate from seasonally anoxic waters within the Baltic proper. During an anoxic episode in the Landsort Deep high dissolved concentrations of Mn were built up in the oxygen-free zone. A concentration of 700 μg l-1 was measured in the bottom water. Dissolved Mn concentrations dropped to values below 1 μg l-1, when the whole water column was oxygenated. Mn-rich particles, 40-80 μg l-1 suspended Mn, were found in the former reduced zone. Large temporal variations in the dissolved and suspended Mn concentrations were observed in the oxidized water column during the studied period. Both Ba and P were scavenged by the Mn-rich phase.
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5.
  • Widerlund, Anders (författare)
  • Early diagenetic remobilization of copper in near-shore marine sediments : a quantitative pore-water model
  • 1996
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 54:1-2, s. 41-53
  • Tidskriftsartikel (refereegranskat)abstract
    • Solid-phase and pore-water Cu have been determined for two cores in the low-salinity (2-3‰) Kalix River estuary, Sweden. The pore-water Cu concentration in the oxidized surface layer of the sediment (32-42 nmol l-1) exceeded the Cu concentration in the overlying bottom water (10-11 nmol l-1) by a factor of 3-4. Assuming that organic matter degradation follows first-order kinetics, a multi-G model with two organic matter fractions of different reactivity was used to describe the early diagenetic decomposition of organic matter. An estimated Cu/C mole ratio of 5.10-5 was obtained from sediment trap data. By combining this ratio with a steady-state pore-water Cu model, the early diagenetic remobilization of Cu was linked to the decomposition of organic matter. The rate constant for the reaction that releases Cu could be set equal to the decay constant of the highly reactive organic matter fraction (2.0 yr-1). This highly reactive fraction was decomposing under aerobic conditions close to the sediment-water interface. Early diagenetic remobilization of Cu in these sediments thus appears to be entirely controlled by aerobic decomposition of organic matter. An estimate of the diffusive benthic efflux of Cu (2.9 nmol cm-2 yr-1) suggests that ˜ 3% of the amount of Cu being deposited is released back into the water column.The pore-water model supports the idea that the Redfield model for the biological control of nitrogen and phosphorus can be extended to certain bioreactive trace elements.
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6.
  • Abbas, Zareen, 1962, et al. (författare)
  • Monte Carlo simulation of the dissociation constants of CO2 in 0 to 1 molal sodium chloride between 0 and 25 °C
  • 2013
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 150:1, s. 1-10
  • Tidskriftsartikel (refereegranskat)abstract
    • Stoichiometric dissociation constants of the carbon dioxide system in NaCl solution between 0 and 1 mol and 0 to 25 °C were estimated by Monte Carlo (MC) simulations, and compared with Pitzer calculations and experimental measurements. The MC simulations used experimentally determined dielectric constants of water at different temperatures, and optimal agreement with the experimental data and Pitzer calculations was achieved by adjusting the ionic radii. This simple procedure resulted in effective ionic radii which were further used to simulate the activity coefficients of salt mixtures. The first and second stoichiometric dissociation constants of carbonic acid in NaCl solution (pK1⁎ and pK2⁎) were estimated from the MC-derived activity coefficients of mixed salts in NaCl. The MC results are in good agreement with the experimental data as well as with the Pitzer calculations. This study shows that Monte Carlo simulations in the temperature and ionic strength range relevant to seawater can provide pK values of the same quality as Pitzer calculations, and constitutes the first step in developing a temperature-dependent MC model for seawater. While MC calculations require greater computing resources, the number of parameters derived by fitting to thermodynamic data is substantially smaller than for Pitzer calculations.
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7.
  • Andersson, Maria, et al. (författare)
  • Air-sea exchange of volatile mercury in the North Atlantic Ocean
  • 2011
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 125:1-4, s. 1-7
  • Tidskriftsartikel (refereegranskat)abstract
    • Part of the Beringia 2005 expedition covered the North Atlantic Ocean. During this passage, dissolved gaseous mercury (DGHg) in seawater and atmospheric concentrations of total gaseous mercury (TGHg), carbon monoxide (CO), and ozone (O-3) were measured continuously at high resolution. In addition, meteorological parameters such as wind speed and water temperature were measured continuously by the ship's meteorological instrumentation. The DGHg concentration was measured using a continuous equilibrium system where the elemental mercury in the sea water was equilibrated with a stream of gas. The DGHg concentration was calculated using DGHg=Hg-eq/k(H), where Hg-eq is the concentration of elemental mercury in the equilibrated air and k(H), is the dimensionless Henry's law constant. The degree of saturation was determined directly from the measurements S = Hg-eq/TGHg. The water sampled had an average DGHg concentration of 58 +/- 10 fM and the average TGHg concentration was determined to 1.7 +/- 0.1 ng m(-3). The water sampled was under- and super-saturated with respect to elemental mercury covering a large range of saturation of 70 to 230% resulting in an average degree of saturation of 150 +/- 30%. Therefore, both evasion and deposition of elemental mercury were observed in the sampled water. In the light of the average flux, 2.1 +/- 1.8 pmol m(-2) h(-1), it is concluded that mostly evasion occured during the sampling period. (C) 2011 Elsevier B.V. All rights reserved.
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8.
  • Andersson, Maria, 1980, et al. (författare)
  • Enhanced concentrations of dissolved gaseous mercury in the surface waters of the Arctic Ocean
  • 2008
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 110:3-4, s. 190-194
  • Tidskriftsartikel (refereegranskat)abstract
    • During an almost three months long expedition in the Arctic Ocean, the Beringia 2005, dissolved gaseous mercury (DGM) was measured continuously in the surface water. The DGM concentration was measured using an equilibrium system, i.e. the DGM in the water phase equilibrated with a stream of gas and the gas was thereafter analysed with respect to its mercury content. The DGM concentrations were calculated using the following equation, DGM = Hg eq / k H' where Hg eq is the equilibrated concentration of elemental mercury in the gas phase and k H' is the dimensionless Henry's law constant at desired temperature and salinity. During the expedition several features were observed. For example, enhanced DGM concentration was measured underneath the ice which may indicate that the sea ice acted as a barrier for evasion of mercury from the Arctic Ocean to the atmosphere. Furthermore, elevated DGM concentrations were observed in water that might have originated from river discharge. The gas-exchange of mercury between the ocean and the atmosphere was calculated in the open water and both deposition and evasion were observed. The measurements showed significantly enhanced DGM concentrations, compared to more southern latitudes. © 2008 Elsevier B.V. All rights reserved.
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9.
  • Andersson, Maria, 1980, et al. (författare)
  • Seasonal and daily variation of mercury evasion at coastal and off shore sites from the Mediterranean Sea
  • 2007
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 104:3-4, s. 214-226
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hg-extr / H', Hg-extr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March-April 2004 and October-November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hg-extr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600-1150%) was observed during the summer. The spring showed the lowest variation (260-360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500-1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P. S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air-sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(l):373-387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m(-2) h(-1). The summer value was estimated to 22.3 pmol m(-2) h(-1) and the spring to 7.6 pmol m(-2) h(-1). Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons. (C) 2006 Elsevier B.V. All rights reserved.
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10.
  • Bauer, Susanne, et al. (författare)
  • Distribution of dissolved and suspended particulate molybdenum, vanadium, and tungsten in the Baltic Sea
  • 2017
  • Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 196, s. 135-147
  • 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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11.
  • Bey, Ergün, et al. (författare)
  • Ocean acidification reduces iodide production by the marine diatom Chaetoceros sp. (CCMP 1690)
  • 2023
  • Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 257
  • Tidskriftsartikel (refereegranskat)abstract
    • Phytoplankton in marine surface waters play a key role in the global iodine cycle. The biologically-mediated iodide production under future scenarios is limited. Here we compare growth, iodate to iodide conversion rate and membrane permeability in the diatom Chaetoceros sp. (CCMP 1690) grown under seawater carbonate chemistry conditions projected for 2100 (1000 ppm) and pre-industrial (280 ppm) conditions. We found no effect of CO2 on growth rates, but a significantly higher cell yield under high CO2, suggesting sustained growth from relief from carbon limitation. Cell normalised iodate uptake (16.73 +/- 0.92 amol IO3- cell-1) and iodide production (8.61 +/- 0.15 amol I-cell-1) was lower in cultures grown at high pCO2 than those exposed to preindustrial conditions (21.29 +/- 2.37 amol IO3- cell-1, 11.91 +/- 1.49 amol I-cell-1, respectively). Correlating these measurements with membrane permeability, we were able to ascertain that iodide conversion rates were not linked to cell permeability and that the processes of mediated iodate loss and diatom-iodide formation are decoupled. These findings are the first to implicate OA in driving a potential shift in diatom-mediated iodate reduction. If our results are indicative of diatom-mediated iodine cycling in 2100, future surface ocean conditions could experience reduced rates of iodide production by Chaetoceros spp., potentially lowering iodide concentrations in ocean regions dominated by this group. These changes have the potential to impact ozone cycling and new particle formation in the atmosphere.
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12.
  • Bigg, E Keith, et al. (författare)
  • Particulates of the surface microlayer of open water in the central Arctic Ocean in summer
  • 2004
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 91, s. 131-141
  • Tidskriftsartikel (refereegranskat)abstract
    • The particulate content of samples of the surface microlayer water collected from the open water between ice floes at latitudes 88° to 89°N in August 2001 was examined by transmission electron microscopy. Concentrations varied from 2×107 ml−1 to more than 1014 ml−1 although bacterial counts made in the same samples varied by only about 50%. Size distributions of the particles were also very variable with modal diameter sizes of 10 nm in some samples and 50 nm in others, the 50-nm particles appearing to be clusters of the 10 nm ones. A mucus-like material held the particles together in rafts, strings or in balls. The largest particles were compact electron-opaque aggregates of smaller particles. The particles appeared to have very similar characteristics to the “microcolloids” observed in bulk seawater in lower latitude oceans. X-ray analyses of the elements with atomic numbers >16 showed all signals to be weak, suggesting a mainly organic composition. The elements that were most commonly greater than background levels were all those associated with marine biological activity. Rapid aggregation of polymers to form colloids has been noted and is likely to be an important cause of the observed variability of particulate concentrations in the surface microlayer. The possibility of an equally rapid dispersal under the influence of ultraviolet light is raised.
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13.
  • Braungardt, C. B., et al. (författare)
  • Analysis of dissolved metal fractions in coastal waters: An inter-comparison of five voltammetric in situ profiling (VIP) systems
  • 2009
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 114:1-2, s. 47-55
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents the results of an inter-comparison exercise undertaken to test the reliability and performance of a voltammetric in situ profiling system (VIP system) and carried out by partners based in Italy, Sweden, Switzerland and the UK. The VIP system was designed to allow in situ simultaneous monitoring of the dynamic fractions (i.e. the maximum potentially bioavailable fractions) of Cu(II). Pb(II) and Cd(II) in natural waters at a frequency of 2-3 analyses h(-1). The four participating groups used the VIP systems under laboratory conditions to determine dissolved concenterations of Cu, Pb and Cd in river, estuarine and coastal water reference materials (SLRS-3/4, SLEW-2/3 and CASS3/4, respectively). The accuracy of the VIP method was comparable to that of established methodologies, including inductively coupled plasma mass spectrometry and voltammetric methods using mercury-electrodes. The VIP systems were also applied to determine the dynamic fractions of the target analytes in freshly collected samples ex situ, as well as in situ in contrasting European marine waters. There was good agreement between the concentrations of the dynamic metal fractions determined in laboratory analyses, and observed during the Simultaneous deployment of up to five VIP instruments for periods of several hours in coastal waters. The simultaneous in situ deployment of two VIP instruments in an estuary showed a consistent analytical performance over several days of continuous operation. The results of this inter-comparison exercise show that the VIP system is a reliable submersible probe for accurate, sensitive and high resolution in situ monitoring of dissolved metal fractions in the picomolar (Cd, Pb) and nanomolar (Cu) concentration ranges. (C) 2009 Elsevier B.V. All rights reserved.
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14.
  • Bridgestock, Luke, et al. (författare)
  • Assessing the utility of barium isotopes to trace Eurasian riverine freshwater inputs to the Arctic Ocean
  • 2021
  • Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 236, s. 104029-104029
  • Tidskriftsartikel (refereegranskat)abstract
    • Tracing riverine freshwater transport pathways within the Arctic Ocean is key to understanding changes in Arctic Ocean freshwater inventories. Dissolved Ba concentrations have been used in this capacity but are compromised by non-conservative processes. To assess the potential for Ba isotopes to provide insights into the impact of such processes on Arctic Ocean dissolved Ba inventories, Ba concentration and isotope data for surface seawater samples from the Siberian Shelf and Bering Sea/Strait are presented. These samples capture the mixing of riverine freshwater discharged by the rivers Yenisey, Lena and Ob, with Atlantic and Pacific derived seawater, which are traced by relationships between salinity, Ba concentration and δ138/134Ba. The δ138/134Ba of net river inputs, following modification by estuarine processes, are constrained to be 0.31 ± 0.04‰, 0.20 ± 0.06‰ and 0.23 ± 0.04‰, for the rivers Yenisey, Lena and Ob respectively. These values are used to estimate an average δ138/134Ba for Eurasian river freshwater input to the Arctic Ocean of 0.23 ± 0.04‰. The Ba concentration and δ138/134Ba of Lena River freshwater transported across the Laptev Sea are modified by non-conservative processes. These non-conservative processes do not result in distinctive modification of dissolved Ba concentration-δ138/134Ba mixing relationships between Eurasian riverine freshwater and Arctic seawater, which unfortunately limits the potential of Ba isotopes to improve tracing riverine freshwater sources in the central Arctic Ocean basins using dissolved Ba inventories. More generally the results of this study help advance understanding of Ba isotope cycling in the environment and their development as an emerging tracer of marine processes.
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15.
  • Cabral dos Santos, Alex, 1990, et al. (författare)
  • Fresh and saline submarine groundwater discharge as sources of carbon and nutrients to the Japan Sea
  • 2023
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 249
  • Tidskriftsartikel (refereegranskat)abstract
    • Submarine groundwater discharge (SGD) is an important pathway for carbon and nutrients to the coastal ocean, sometimes exceeding river inputs. SGD fluxes can have implications for long-term carbon storage, ocean acidification and nutrient dynamics. Here, we used radium (223Ra and 226Ra) isotopes to quantify SGD-derived fluxes of dissolved inorganic (DIC) and organic (DOC) carbon, nitrate (NO3−), nitrite (NO2−), ammonium (NH4+) and phosphate (PO43−) in a spring-fed coastal bay in the Japan Sea. The average coastal water residence times using 223Ra/226Ra ratios was 32.5 ± 17.9 days. Fresh and saline SGD were estimated using a radium mixing model with short- and long-lived isotopes. The volume of fresh SGD entering the bay (4.6 ± 4.6 cm day−1) was more than twice that of the volume of saline SGD (1.9 ± 2.1 cm day−1). Fresh SGD (mmol m2 day−1) was the main source of DOC (2.7 ± 2.6), DIC (13.9 ± 13.7), PO43− (0.3 ± 0.3) and NO3− (6.6 ± 6.5) to the coastal ocean, whereas saline SGD was the main source of NH4+ (0.2 ± 0.2). Total SGD-derived carbon and nutrient fluxes were 4 – 7 and 2–16 times greater than local river inputs. Positive correlations between chlorophyll-a, 226Ra and δ13C-DIC indicate that SGD significantly (p < 0.05) enhances primary productivity nearshore. Overall, fresh SGD of nitrogen and carbon to seawater drove chlorophyll-a, decreased DIC/Alkalinity ratios, and modified the carbonate biogeochemistry of the coastal ocean.
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16.
  • Cai, Minggang, et al. (författare)
  • Concentrations, distribution and sources of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls in coastal sediments from Xiamen, China
  • 2016
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 185, s. 74-81
  • 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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17.
  • Clegg, Simon L., et al. (författare)
  • Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties. II. Tris buffers in artificial seawater at 25 °C, and an assessment of the seawater ‘Total’ pH scale
  • 2022
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 244
  • Tidskriftsartikel (refereegranskat)abstract
    • The substance Tris (or THAM, 2-amino-2-hydroxymethyl-1,3-propanediol, CAS 77–86-1), and its protonated form TrisH+, is used in the preparation of pH buffer solutions for applications in seawater chemistry. The development of an acid-base chemical speciation model of buffer solutions containing Tris, TrisH+, and the major ions of seawater is desirable so that: (i) the effects of changes in the composition of the medium on pH can be calculated; (ii) pH on the free (a measure of [H+]) and total (a measure of ([H+] + [HSO4−])) scales can be interconverted; (iii) approximations inherent in the definition of the total pH scale can be quantified; (iv) electrode pairs such as H+/Cl− and H+/Na+ can more easily be calibrated for the measurement of pH. As a first step towards these goals we have extended the Pitzer-based speciation model of Waters and Millero (Mar. Chem. 149, 8–22, 2013) for artificial seawater to include Tris and TrisH+, at 25 °C. Estimates of the variances and covariances of the additional interaction parameters were obtained by Monte Carlo simulation. This enables the total uncertainty of any model-calculated quantity (e.g., pH, speciation) to be estimated, as well as the individual contributions of all interaction parameters and equilibrium constants. This is important for model development, because it allows the key interactions to be identified. The model was tested against measured EMFs of cells containing Tris buffer in artificial seawater at 25 °C, and the mean deviation was found to be 0.13 ± 0.070 mV for salinities 20 to 40. Total variances for calculated electromotive forces of the buffer solutions are dominated by contributions from just a few interaction parameters, making it likely that the model can readily be improved. The model was used to quantify the difference between various definitions of total pH and –log10([H+] + [HSO4−]) in Tris buffer solutions at 25 °C, for the first time (item (iii) above). The results suggest that the total pH scale can readily be extended to low salinities using the established approach for substituting TrisH+ for Na+ in the buffer solutions, especially if the speciation model is used to quantify the effect on pH of the substitution. The relationships between electromotive force (EMF), and pH on the total scale, with buffer molality in artificial seawater at constant salinity are shown to be linear above about 0.01 to 0.02 mol kg−1 buffer molality. The pH of Tris buffers containing ratios of TrisH+ to Tris that vary from unity can be calculated very simply. Technical aspects of the total pH scale, such as the extrapolation of pH to zero buffer (at constant salinity), are clarified. Recommendations are made for further work to extend the model to the temperature range 0–45 °C, and improve accuracy, so that requirements (i) to (iv) above can be fully met.
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18.
  • Clegg, S. L., et al. (författare)
  • Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties. III. Seawater from the freezing point to 45 & DEG;C, including acid-base equilibria
  • 2023
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 250
  • Tidskriftsartikel (refereegranskat)abstract
    • A quantitative understanding of pH, acid-base equilibria, and chemical speciation in natural waters including seawater is needed in applications ranging from global change to environmental and water quality management. In a previous study (Humphreys et al., 2022) we implemented a model of solutions containing the ions of artificial seawater, based upon the use of the Pitzer equations for the calculation of activity coefficients and including, for the first time, the propagation of uncertainties. This was extended (Clegg et al., 2022) to include the Tris buffer solutions that are used to calibrate the seawater total pH scale. Here we apply the same methods to develop a model of solutions containing the ions of standard reference seawater, based upon studies by Millero and co-workers. We compare the predictions of the model to literature data for: the dissociation of dissolved CO2 and bicarbonate ion; boric acid dissociation; saturation with respect to calcite, the ion product of water, and osmotic coefficients of seawater. Estimates of the uncertainty contributions of all thermodynamic equilibrium constants and Pitzer parameters to the variance of the calculated quantity are used to determine which elements of the model need improvement, with the aim of agreeing with properties noted above to within their experimental uncertainty. Further studies are recommended. Comparisons made with several datasets for carbonate system dissociation in seawater suggest which are the most reliable, and identify low salinity waters (S < 10) as a region for which dissociation constants of bicarbonate are not yet accurately known. At present, the model is likely to be most useful for the direct calculation of equilibria in natural waters of arbitrary composition, or for adjusting dissociation constants known for seawater media to values for natural waters in which the relative compositions of the major ions are different.
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19.
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20.
  • Davis, K. L., et al. (författare)
  • Calcification and organic productivity at the world's southernmost coral reef
  • 2020
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 227
  • Tidskriftsartikel (refereegranskat)abstract
    • Estimates of coral reef calcification and organic productivity provide valuable insight to community functionality and the response of an ecosystem to stress events. High-latitude coral reefs are expected to experience rapid changes in calcification rates and become refugia for tropical species following climate change and increasing bleaching events. Here, we estimate ecosystem-scale calcification and organic productivity at the world's southernmost coral reef using seawater carbon chemistry observations (Lord Howe Island, Australia). We reduce uncertainties in metabolic calculations by producing a detailed bathymetric model and deploying two current meters to refine residence time and volume estimates. Bathymetry-modelled transect depths ranged from 74% shallower to 20% deeper than depths averaged from reef crest/flat current meters, indicating that higher-resolution depth observations help to reduce uncertainties in reef metabolic calculations. Rates of ecosystem calcification were 56.6 +/- 14.8 mmol m(-2) d(-1) in the winter and 125.3 +/- 39.4 mmol m(-2) d(-1) in the summer. These rates are lower than most other high-latitude reefs according to our compilation of high-latitude coral ecosystem metabolism estimates. Coral cover ranged from 14.7 +/- 2.3% in winter to 19.8 +/- 2.1% in the summer. A concurrent bleaching event and cyclone occurred during summer sampling (February - March 2019), resulting in 47% of corals bleached at the study site and 2% mortality due to cyclonal damage. Therefore, it is likely that the summertime G(net) rates underestimate baseline calcification. Our results enable future assessments of long-term change, but do not resolve the impact of bleaching at Lord Howe Island.
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21.
  • Drott, Andreas, et al. (författare)
  • Effects of oxic and anoxic filtration on determined methyl mercury concentrations in sediment pore waters
  • 2007
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 103, s. 76-83
  • Tidskriftsartikel (refereegranskat)abstract
    • Accurate determination of methyl mercury (MeHg) concentrations in sediment pore waters is crucial for an improved understanding of mercury (Hg) biogeochemistry, and for improved risk assessment of Hg contaminated sites. In the present study, effects of oxic (air) and anoxic (N2) filtration (after centrifugation) on determined pore water MeHg concentrations were investigated in severely Hg contaminated pulp fibre sediments from two estuaries of the Bothnian Sea, Sweden. MeHg was determined in the filtrate using species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID–GC–ICPMS), after ethylation with sodium tetraethylborate. Determined concentrations of MeHg were greater after anoxic filtration than after oxic filtration for all samples investigated, with MeHg(N2)/MeHg(air) ratios ranging between 3.4 and 343. Adsorption to newly formed Fe(III)/Mn(III/IV)-oxy/hydroxide surfaces is proposed as the main mechanism responsible for MeHg removal during oxic filtration. This is supported by decreases in dissolved Fe and Mn concentrations during oxic filtration, and by decreases in dissolved sulphur concentrations during oxic filtration in the samples with largest effect on MeHg concentrations. The latter is explained by adsorption of SO42− to newly formed Fe(III)/Mn(III/IV)-oxy/hydroxide surfaces. The effect of oxidation during filtration on pore water MeHg concentrations was largest in samples in which FeS(s) was not present, but with calculated pe-values below − 3. Thus, our results indicate that the largest errors with respect to pore water MeHg concentrations when filtering in air can be expected in samples with an intermediate redox potential, possibly buffered by a mixture of oxidation sensitive Fe(II/III) minerals.
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22.
  • Drott, Andreas, et al. (författare)
  • Potential demethylation rate determinations in relation to concentrations of MeHg, Hg and pore water speciation of MeHg in contaminated sediments
  • 2008
  • Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 112:1-2, s. 93-101
  • Tidskriftsartikel (refereegranskat)abstract
    • Specific, potential demethylation rate constants (kd, day− 1) were determined in fresh and brackish water sediments from seven different sites in Sweden originally contaminated with either Hg0(l) or phenyl-Hg. Variations in kd among and within sites were related to ambient concentrations of Hg (1–1143 nmol g− 1) and MeHg (4.4–575pmol g− 1), and to pore water speciation of MeHg. Chemical speciation modeling revealed that MeHgSH(aq), MeHgS−(aq) and MeHg–thiol complexes [MeHgSR(aq)] associated to dissolved organic matter were the dominant MeHg species in the sediment pore water at all sites. Potential rates of MeHg demethylation were determined as the decomposition of isotopically enriched Me204HgCl during 48 h of incubation in darkness under N2(g) at 23 °C. There was a significant (p < 0.001) positive relationship between ambient MeHg concentrations in sediments and kd across all sites, but no significant relationship between ambient Hg and kd. At the three sites with the highest ambient Hg concentrations in sediments (average ± SD, 185 ± 249 nmol g− 1), kd was not significantly correlated with pore water MeHg speciation. At sites with lower concentrations of ambient Hg in sediments (average ± SD, 11 ± 8.4 nmol g− 1), there was a significant (p = 0.02) positive relationship between calculated concentrations of MeHgSH(aq), MeHgS−(aq), or the sum of these two species, and kd. If it is assumed that an oxidative demethylation process dominated at sites with lower concentrations of ambient Hg in sediments, the results suggest that it may be dependent on a passive uptake of inorganic MeHgSH molecules. It was shown that additions of different amounts of MeHg and Hg tracers, in relation to the ambient concentrations of MeHg and Hg, could result in dramatically different kd values within and between sites. At one brackish water site, both absolute demethylation rates and kds were significantly, inversely related to ambient concentrations of MeHg (and Hg). In contrast, at another brackish water site with generally less kds, samples with low ambient MeHg experienced toxic effects and demethylation was not detected. This implies that added (and possibly ambient) MeHg/Hg, depending on the environmental conditions, may have either stimulating or inhibitory effects on demethylation processes.
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23.
  • Gallego-Urrea, Julian A., 1977, et al. (författare)
  • Determination of pH in estuarine and brackish waters: Pitzer parameters for Tris buffers and dissociation constants for m-cresol purple at 298.15K
  • 2017
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 195, s. 84-89
  • 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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24.
  • Gdaniec, Sandra, et al. (författare)
  • Thorium and Protactinium isotopes as tracers of marine particle fluxes and deep water circulation in the Mediterranean Sea
  • 2018
  • Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 199, s. 12-23
  • 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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25.
  • Gonsior, Michael, et al. (författare)
  • Photochemical Production of Polyols arising from Significant Photo-transformation of Dissolved Organic Matter in the Oligotrophic Surface Ocean
  • 2014
  • Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 163, s. 10-18
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultrahigh resolution mass spectrometry of marine dissolved organic matter (DOM) has suggested the presence of many common molecular compositions throughout the open ocean. The majority of these supposedly ubiquitous molecules was concluded to represent the refractory marine DOM pool. This study demonstrates that 24 h of exposure of Atlantic and Pacific surface DOM to simulated sunlight causes phototransformation of about half of these supposedly refractory molecular compositions. It is suggested that these transformations are related to indirect photobleaching possibly involving reactive oxygen species (e.g. hydroxyl radicals), because very little change in the fluorescent component of the DOM (FDOM) was observed during the photo-degradation experiments. A significant decline in average mass with distinct decrease of average O/C ratios and concomitant increase of H/C ratios was observed. NMR spectra revealed a decrease in aromatic and olefinic unsaturation and the formation of a limited and near identical suite of oxygenated aliphatic compounds in both Atlantic and Pacific surface DOM. Their NMR characteristics indicated a mixture of about 10 polyols that are plausible products of convergent pathways of photochemical carbohydrate decomposition and oxidation of functionalized, branched aliphatic compounds. These prominent photochemical signature molecules amounted to -2% of total proton NMR integral and are expected to be quickly consumed by various microorganisms in the open ocean. These results may suggest a fast photo-induced large-scale cycling of DOM within the surface ocean dynamic equilibrium of photo- and bio-transformations. (C) 2014 Elsevier B.V. All rights reserved.
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26.
  • Granfors, Anna, 1978, et al. (författare)
  • Biogenic halocarbons in young Arctic sea ice and frost flowers
  • 2013
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 155, s. 124-134
  • Tidskriftsartikel (refereegranskat)abstract
    • The fate of halocarbons, naturally produced volatile halogenated organic compounds, in young Arctic sea ice was studied to better understand the role of sea ice in halocarbon cycling. In early spring, halocarbons were measured in sea ice frozen in core holes, during 12 days of formation and freezing. In order to understand which factors govern halocarbon concentration and distribution, salinity, temperature and biological parameters were monitored in the growing sea ice. It was found that sea ice participates in the cycling of halocarbons between sea and air. Sea ice concentrations and distributions of these compounds were influenced by production in the ice, where ice-inhabiting microorganisms caused local increases in halocarbon concentrations. Moreover, the halocarbon ice concentration decrease/change with time did not follow ice salinity, suggesting that additional removal processes caused sea ice to be a source of halogens to overlying air. The net production rate of bromoform in the surface of newly frozen ice was estimated to 14 pmol L−1 d−1 and the maximum removal rate was 18 pmol L−1 d−1. In addition frost flowers on newly formed sea ice were identified as contributors of halocarbons to the atmosphere with halocarbon concentrations in the same order of magnitude as in sea ice brine
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27.
  • Gustafsson, Örjan, et al. (författare)
  • The POC / 234Th ratio of settling particles isolated using split flow-thin cell fractionation (SPLITT)
  • 2006
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 100:3-4, s. 314-322
  • Tidskriftsartikel (refereegranskat)abstract
    • The common assumption that the ratio between particulate organic carbon (POC) and particulate 234Th obtained from shallow sediment traps and filterable particles are representative of the ratio in the total particle settling flux should be treated with caution in view of well-known biases associated with tethered shallow sediment traps and the decoupling between size and settling velocity of many natural particle regimes. To make progress toward reliably constraining the POC / 234Th ratio on truly settling particles, we have tested here a settling collection technique designed to remove any hydrodynamic bias; split flow-thin cell fractionation (SPLITT). These first results from a North Sea fjord and an open Baltic Sea time-series station indicates that the POC / 234Th ratio on the more complete particle-settling spectrum, isolated with SPLITT, was higher than the POC / 234Th ratio obtained simultaneously from tethered shallow sediment traps in seven out of seven parallel deployments with an average factor of 210%. The POC / 234Th ratio from the SPLITT was either in the same range or higher than that obtained on filtered "bulk" particles. To explain this novel data we hypothesize that the slowest settling fraction is organic-matter rich and does not strongly complex 234Th (i.e., high POC / 234Th). We suggest that this ultra-slow sinking fraction is better collected by SPLITT than with tethered sediment traps because of minimized hydrodynamic bias. This was tested using the ratio of POC / Al as a tracer of detrital mineral-ballast influenced settling velocity. The higher POC / Al ratios in SPLITT samples relative to in traps is consistent with the hypothesis that SPLITT is better suited for collecting also the slow-settling component of sinking particles. This important slow-settling component appears to here consist primarily of non-APS/TEP components of plankton exudates or other less-strongly 234Th-complexing organic matter. Further applications of the SPLITT technique are likely to return increasingly new insights on the composition (including "truly settling" POC / 234Th) of the total spectrum of particles settling out of the upper ocean.
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28.
  • Hjalmarsson, Sofia, 1980, et al. (författare)
  • The exchange of dissolved inorganic carbon between the Baltic Sea and the North Sea in 2006 based on measured data and water transport estimates from a 3D model
  • 2010
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 121:1-4, s. 200-205
  • Tidskriftsartikel (refereegranskat)abstract
    • The Baltic Sea is one of the largest estuarine systems on earth. Two narrow straits, Öresund and The Belt Sea, together with a large transition area consisting of Kattegat and Skagerrak hamper interactions with the North Sea. The Baltic Sea water is low in salinity due to the large freshwater input from river runoff to the Baltic Sea but has an excess of inorganic carbon from dissolution of carbonate minerals in the river drainage basins. In this study we use dissolved inorganic carbon data from the Baltic Sea and the Kattegat together with modelled water transport to evaluate the dissolved inorganic carbon exchange between the Baltic Sea and the North Sea during 2006. The total inorganic carbon export from the Baltic Sea in the straits area is 5.5 ± 0.3 Tg C year−1, or 0.45 ± 0.03 1012 mol year−1. These numbers are about 1/3 lower than earlier reported export values and will hence have a corresponding effect on budget computations of the connected seas.
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29.
  • Hoffmann, L. J., et al. (författare)
  • Influence of trace metal release from volcanic ash on growth of Thalassiosira pseudonana and Emiliania huxleyi
  • 2012
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 132-133, s. 28-33
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent studies demonstrate that volcanic ash has the potential to increase phytoplankton biomass in the open ocean. However, besides fertilizing trace metals such as Fe, volcanic ash contains a variety of potentially toxic metals such as Cd, Cu, Pb, and Zn. Especially in coastal regions closer to the volcanic eruption, where ash depositions can be very high, toxic effects are possible. Here we present the first results from laboratory experiments, showing that trace metal release from different volcanic ashes can have both fertilizing and toxic effects on marine phytoplankton in natural coastal seawater. The diatom Thalassiosira pseudonana generally showed higher growth rates in seawater that was in short contact with volcanic ash compared to the controls without ash addition. In contrast to that, the addition of volcanic ash had either no effect or significantly decreased the growth rate of the coccolithophoride Emiliania huxleyi. It was not possible to attribute the effects to single trace metals, however, our results suggest that Mn plays an important role in regulating the antagonistic and synergistic effects of the different trace metals. This study shows that volcanic ash can lead to changes in the phytoplankton species composition in the high fall-out area of the surface ocean.
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30.
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31.
  • Hulth, Stefan, 1965, et al. (författare)
  • Nitrogen removal in marine environments: recent findings and future research challenges
  • 2005
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 94:1-4, s. 125-145
  • Tidskriftsartikel (refereegranskat)abstract
    • Respiratory reduction of nitrate (denitrification) is recognized as the most important process converting biologically available (fixed) nitrogen to N-2. In current N cycle models, a major proportion of global marine denitrification (50-70%) is assumed to take place on the sea floor, particularly in organic rich continental margin sediments. Recent observations indicate that present conceptual views of denitrification and pathways of nitrate reduction and N, formation are incomplete. Alternative N cycle pathways, particularly in sediments. include anaerobic ammonium oxidation to nitrite, nitrate and N-2 by Mn-oxides, and anaerobic ammonium oxidation coupled to nitrite reduction and subsequent N, mobilization. The discovery of new links and feedback mechanisms between the redox cycles of, e.g., C, N, S, Mn and Fe casts doubt on the present general understanding of the global N cycle. Recent models of the oceanic N budget indicate that total inputs are significantly smaller than estimated fixed N removal. The occurrence of alternative N reaction pathways further exacerbates the apparent imbalance as they introduce additional routes of N removal. In this contribution, we give a brief historical background of the conceptual understanding of N cycling in marine ecosystems, emphasizing pathways of aerobic and anaerobic N mineralization in marine sediments, and the implications of recently recognized metabolic pathways for N removal in marine environments. (c) 2004 Elsevier B.V. All rights reserved.
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32.
  • Humphreys, Matthew P., et al. (författare)
  • Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties: Artificial seawater from 0 to 45 °C
  • 2022
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 244
  • Tidskriftsartikel (refereegranskat)abstract
    • Accurate chemical speciation models of solutions containing the ions of seawater have applications in the calculation of carbonate system equilibria and trace metal speciation in natural waters, and the determination of pH. Existing models, based on the Pitzer formalism for the calculation of activity coefficients, do not yet agree with key experimental data (potentiometric determinations of H+ and Cl− activity products in acidified artificial seawaters) and, critically, do not include uncertainty estimates. This hampers applications of the models, and also their further development (for which the uncertainty contributions of individual ion interactions and equilibrium constants need to be known). We have therefore implemented the models of Waters and Millero (Mar. Chem. 149, 8-22, 2013) and Clegg and Whitfield (Geochim. et Cosmochim. Acta 59, 2403-2421, 1995) for artificial seawater, within a generalised treatment of uncertainties, as a first step towards a more complete model of standard seawater and pH buffers. This addition to the models enables both the total uncertainty of any model-calculated quantity (e.g., pH, speciation) to be estimated, and also the contributions of all interaction parameters and equilibrium constants. Both models have been fully documented (and some corrections made). Estimates of the variances and covariances of the interaction parameters were obtained by Monte Carlo simulation, with simplifying assumptions. The models were tested against measured electromotive forces (EMFs) of cells containing acidified artificial seawaters. The mean offsets (measured – calculated) at 25 °C for the model of Waters and Millero are: 0.046 ± 0.11 mV (artificial seawater without sulphate, 0.280 mol kg−1 to 0.879 mol kg−1 ionic strength); and −0.199 ± 0.070 mV (artificial seawater, salinities 5 to 45). Results are similar at other temperatures. These differences compare with an overall uncertainty in the measured EMFs of about 0.04 mV. Total uncertainties for calculated EMFs of the solutions were dominated by just a few contributions: mainly H+-Cl−, Na+-Cl−, and H+-Na+-Cl− ionic interactions, and the thermodynamic dissociation constant of HSO4−. This makes it likely that the accuracy of the models can readily be improved, and recommendations for further work are made. It is shown that standard EMFs used in the calibration of the marine ‘total’ pH scale can be accurately predicted with only slight modification to the original models, suggesting that they can contribute to the extension of the scale to lower salinities.
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33.
  • Illuminati, S., et al. (författare)
  • In-situ trace metal (Cd, Pb, Cu) speciation along the Po River plume (Northern Adriatic Sea) using submersible systems
  • 2019
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 212, s. 47-63
  • 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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34.
  • Ingri, Johan, et al. (författare)
  • Changes in trace metal sedimentation during freshening of a coastal basin
  • 2014
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 167, s. 2-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Holocene freshening has turned the Bothnian Bay, northern Baltic Sea into an oligotrophic basin. Sequestering of trace elements has changed significantly during the oligotrophication process. In principle, trace metals have been transferred from permanently buried sulfides to Fe–Mn-oxyhydroxides in the top layers of the sediment. The oxyhydroxide layers restrict the flux of trace metals from the sediment to the oxic bottom water. Hence, Fe–Mn cycling in the suboxic sediment enriches a number of trace metals in the surface sediment. Arsenic, Sn, Ge and Bi show enrichment in the Fe-oxyhydroxide layer, whereas Mo, Cd, Ni, Co, Cu, and Sb are enriched in the uppermost Mn-oxyhydroxide layer. This natural redox cycling in the sediment obscures pollution effects.The oligotrophication process started approximately 3500 years ago, reflected in decreasing deposition of Zn, a proxy for phytoplankton production, and formation of Mn oxyhydroxide layers. Similarly, Ba/Al data indicate a decrease in the pelagic input of plankton. Barium data also suggest that dissolved sulfide in the sediment never reached high concentrations. Germanium is closely related to Ba, suggesting that Ge can be used as a proxy for phytoplankton production. Vanadium, U, Re, and Mo all indicate that the bottom water never has been significantly sulfidic during the last 5500 years. Rhenium data indicate that the organic carbon oxidation rate has decreased during the last 5500 years. Cadmium follows the organic matter distribution, but started to increase 1000 YBP (years before present). The reason for this enhanced input of Cd is unclear.
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35.
  • Ingri, Johan, et al. (författare)
  • Size distribution of colloidal trace metals and organic carbon during a coastal bloom in the Baltic Sea
  • 2004
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 91:1-4, s. 117-130
  • Tidskriftsartikel (refereegranskat)abstract
    • The physico-chemical speciation of organic carbon and selected metals was measured during a coastal bloom in Ekhagen Bay, Baltic Sea, using ultrafiltration.One important objective with the study was to see if any depletion of trace metals could be measured in the directly bioavailable fraction (<1000 Da, the soluble low molecular weight fraction, LMW) during a plankton bloom. Filters with five different cut-offs were used (1 kD (1000 Da), 5 kD, 10 kD, 100 kD and 0.22 μm) in order to delineate the size distribution of colloidal organic carbon (COC) and trace metals. During the bloom in May, LMW Al, Co, Cu, Mn and Ni concentrations decreased although the colloidal and particulate concentrations were relatively high. Data show that desorption of colloidal and particulate bound trace metals to the LMW fraction was slower than the process depleting the LMW fraction. Estimates of the maximum active uptake of Cu, Ni and Mn by the phytoplankton, and the loss of non-bioactive Al from the LMW fraction, indicate that processes other than active uptake by phytoplankton must contribute to the observed depletion of trace metals in the LMW fraction. Hence, in order to estimate the bioavailable pool of trace metals for plankton during bloom conditions, these other processes must be understood and quantified. Transparent Exopolymeric Particles (TEP, reflecting sugar-rich phytoplankton exudates) increased around eight times during the plankton bloom. We hypothesize that the formation of TEP is a process that might be important for the transfer of trace metals from the LMW to the particulate fraction during the phytoplankton bloom, but the significance of TEP for this depletion in Baltic Sea surface water remains to be shown.
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36.
  • Jonsson, Sofi, et al. (författare)
  • Distribution of total mercury and methylated mercury species in Central Arctic Ocean water and ice
  • 2022
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 242
  • Tidskriftsartikel (refereegranskat)abstract
    • The central Arctic Ocean remains largely unexplored when it comes to the presence and cycling of mercury and its methylated forms including mono- and dimethylmercury (MMeHg and DMeHg, respectively). In this study, we quantified total Hg (HgT) and methylated Hg species in seawater, ice cores, snow, brine, and water from melt ponds collected during the SWEDARCTIC 2016 expedition to the Amerasian and Eurasian side of the Lomonosov Ridge. In the water column, concentrations of HgT, MMeHg and DMeHg ranged from 0.089 to 1.5 pM, <25 to 520 fM and from <1.6 to 160 fM, respectively. HgT was enriched in surface waters while MMeHg and DMeHg were low at the surface (i.e. in the polar mixed layer) and enriched at a water depth of around 200–400 m. A 1:2 ratio of DMeHg to MMeHg was observed in the water column suggesting a lower ratio in the central parts of the Arctic Ocean than what has previously been reported from other parts of the Arctic Ocean. At the ice stations, average HgT ranged from 0.97 ± 1.2 pM in the ice cores to 27 ± 17 pM in melt pond waters and average MeHgT (total MeHg) from 28 ± 15 fM in brine to 130 ± 18 fM in melt pond water. The HgT observed in melt ponds and brine was an order of magnitude greater than HgT observed in surface waters and HgT in the upper part of the ice-cores was ~4–8 times higher HgT in comparison to lower layers. Our study suggests that ice may act as a source of HgT to surface waters but not to be a likely source of the methylated Hg forms. Unlike elemental Hg, DMeHg did not enrich in surface waters covered by ice. Concentrations of DMeHg observed in the ice cores and other samples collected from the ice stations were low, suggesting ice to not act as a source of DMeHg to the atmosphere nor to surface waters.
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37.
  • Jutterström, Sara, 1975, et al. (författare)
  • Uptake of CO2 by the Arctic Ocean in a changing climate
  • 2010
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 122:1-4, s. 96-104
  • Tidskriftsartikel (refereegranskat)abstract
    • Carbon system data from five expeditions over the time period of 1991 to 2005 in the central Arctic Ocean are evaluated with respect to the partial pressure of carbon dioxide in the surface waters. Nearly all waters were undersaturated with values typically below 300 μatm. In the areas occupied during several expeditions the variability is substantial, making it unrealistic to produce a coherent pCO2 map. The potential oceanic uptake of CO2 in the Arctic Ocean is evaluated as the difference in calculated total dissolved inorganic carbon at equilibrium with the atmosphere and that measured. The uptake capacity as computed from the under-saturation of the surface waters, although not homogenous across the separate basins, is on average 13 ± 3 g C m− 2 within the surface mixed layer of the central Arctic Ocean. The uptake capacity is dependent on several variables and processes, many likely to change as the Arctic environment responds to different climate forcings. For instance, the projected decrease in summer sea ice cover allows for air–sea equilibrium resulting in an estimated potential increase in CO2 uptake of 1.3 ± 0.3 Tg C year− 1. Other factors influencing the uptake capacity of the surface mixed layer that are discussed in this contribution are changes in the depth of the surface mixed layer, temperature and primary production, all impacting the partial pressure of CO2.
  •  
38.
  • Kaltin, Staffan, et al. (författare)
  • Uptake of atmospheric carbon dioxide in Arctic shelf seas: evaluation of the relative importance of processes that influence pCO2 in water transported over the Bering–Chukchi Sea shelf
  • 2005
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 94:1-4, s. 67-79
  • Tidskriftsartikel (refereegranskat)abstract
    • The uptake of atmospheric carbon dioxide in the water transported over the Bering–Chukchi shelves has been assessed from the change in carbon-related chemical constituents. The calculated uptake of atmospheric CO2 from the time that the water enters the Bering Sea shelf until it reaches the northern Chukchi Sea shelf slope (1 year) was estimated to be 86±22 g C m−2 in the upper 100 m. Combining the average uptake per m3 with a volume flow of 0.83×106 m3 s−1 through the Bering Strait yields a flux of 22×1012 g C year−1. We have also estimated the relative contribution from cooling, biology, freshening, CaCO3 dissolution, and denitrification for the modification of the seawater pCO2 over the shelf. The latter three had negligible impact on pCO2 compared to biology and cooling. Biology was found to be almost twice as important as cooling for lowering the pCO2 in the water on the Bering–Chukchi shelves. Those results were compared with earlier surveys made in the Barents Sea, where the uptake of atmospheric CO2 was about half that estimated in the Bering–Chukchi Seas. Cooling and biology were of nearly equal significance in the Barents Sea in driving the flux of CO2 into the ocean. The differences between the two regions are discussed. The loss of inorganic carbon due to primary production was estimated from the change in phosphate concentration in the water column. A larger loss of nitrate relative to phosphate compared to the classical ΔN/ΔP ratio of 16 was found. This excess loss was about 30% of the initial nitrate concentration and could possibly be explained by denitrification in the sediment of the Bering and Chukchi Seas.
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39.
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40.
  • Karlsson, Emma S., et al. (författare)
  • Contrasting regimes for organic matter degradation in the East Siberian Sea and the Laptev Sea assessed through microbial incubations and molecular markers
  • 2015
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 170, s. 11-22
  • 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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41.
  • Kitidis, V., et al. (författare)
  • Methane and nitrous oxide in surface water along the North-West Passage, Arctic Ocean
  • 2010
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 121:1-4, s. 80-86
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissolved methane and nitrous oxide in seawater were measured along a 6700 km transect of the North-West Passage between the North Atlantic Ocean and Beaufort Sea in the Arctic Ocean. Over- and under-saturation with respect to atmospheric equilibrium were observed for both gases. Methane and nitrous oxide were in the range of 58–528% and 82–181% saturation, respectively. Under-saturation was attributed to melt-water with low methane and nitrous oxide, while over-saturation was found under multi-year sea-ice. Elevated methane was also found in the vicinity of the marginal ice zones and the Mackenzie River plume. Our data support both water column and sedimentary sources of methane and nitrous oxide. We found first-order methane oxidation in surface seawater with a rate constant of 3.8 × 10−3 h−1. Based on these results and a conceptual model, we suggest that future sea-ice retreat may decrease the residence times of methane and nitrous oxide in the surface Arctic Ocean and thus enhance the sea–air flux of these climatically active gases.
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42.
  • Krall, Lindsay, et al. (författare)
  • Submarine groundwater discharge at Forsmark, Gulf of Bothnia, providedby Ra isotopes
  • 2017
  • Ingår i: Marine Chemistry. - Amsterdam : Elsevier. - 0304-4203 .- 1872-7581. ; 196, s. 162-172
  • 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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43.
  • Kubeneck, L. Joëlle, et al. (författare)
  • Phosphorus burial in vivianite-type minerals in methane-rich coastal sediments
  • 2021
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 231
  • Tidskriftsartikel (refereegranskat)abstract
    • Sediments are a key sink for phosphorus (P) in coastal systems. This allows coastal areas to act as a filter for P that is transported from land to sea. Recent work suggests that vivianite-type ferrous iron (Fe(II))-P minerals may be more important as a sink for P in coastal sediments than previously thought. Here, we investigate the occurrence of such vivianite-type minerals in sediments of three eutrophic coastal sites with contrasting dynamics with respect to iron (Fe) and sulfur (S), covering a salinity range of 0 to 7. We only find authigenic vivianite-type minerals at the low and intermediate salinity sites, where Fe is available in excess over sulfide production. Sequential extractions combined with SEM-EDS and μXRF analysis point towards substitution of Fe in vivianite-type minerals by other transition metal cations such as magnesium and manganese, suggesting potentially different formation pathways modulated by metal cation availability. Our results suggest that vivianite-type minerals may act as a key sink for P in sediments of many other brackish coastal systems. Climate change-driven modulations of coastal bottom water salinity, and hence, Fe versus S availability in the sediment, may alter the role of vivianite-type minerals as a P burial sink over the coming decades. Model projections for the Baltic Sea point towards increased river input and freshening of coastal waters, which could enhance P burial. In contrast, sea level rise in the Chesapeake Bay area is expected to lead to an increase in bottom water salinity and this could lower rates of P burial or even liberate currently buried P, thereby enhancing eutrophication.
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44.
  • Kumar Ranjan, Rajesh, et al. (författare)
  • Elemental and stable isotope records of organic matter input and its fate in the Pichavaram mangrove–estuarine sediments (Tamil Nadu, India)
  • 2011
  • Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 126:1-4, s. 163-172
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to evaluate the sources and fate of organic matter (OM) in the Pichavaram mangrove–estuarine ecosystem, Corg, Ntot, C/Natm, and stable isotopes (δ13Corg and δ15Norg) of five 210Pb dated sediment cores were investigated. Core A was collected from the Vellar Estuary, cores B, C, and D from mangrove forests, and core E was from the Coleroon Estuary. In mangrove sediments, Corg, Ntot, and C/Natm concentration varied from 1.2 ± 0.52%, 0.08 ± 0.03%, and 16.6 ± 4.1%, respectively. In the estuaries, Corg, Ntot, and C/Natm varied from 0.37 ± 0.19%, 0.03 ± 0.01%, and 12.3 ± 2.9%, respectively. In mangrove forests the δ13Corg and δ15Norg values varied from − 24.3 ± 1.8‰ and 4.2 ± 0.86‰, whereas in estuaries these values were − 23.2 ± 1.6‰ and 5.1 ± 1.3‰, respectively. The variation represents variable inputs of marine and terrestrial OM in these area, OM degradation, replacement of native vegetation due to increasing salinity, and early diagenetic changes. Some of these changes could be attributed to anthropogenic activities that have been happening in the Pichavaram complex over the last few decades. OM once deposited in the sediments is rapidly decomposed or remineralized in both mangrove and estuarine sites. The rate of Corg burial is more in mangrove forests than estuaries. Early diagenetic changes are modeled in the cores based on C/N stoichiometry. This was most applicable in mangrove sediments (core C) where ~ 56% C was remineralized representing a first order diagenetic model.
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45.
  • Kumar Ranjan, Rajesh, et al. (författare)
  • Sediment biomarker profiles trace organic matter input in the Pichavaram mangrove complex, southeastern India
  • 2015
  • Ingår i: Marine Chemistry. - : Elsevier. - 0304-4203 .- 1872-7581. ; 171, s. 44-57
  • 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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46.
  • Liem-Nguyen, Van, et al. (författare)
  • Spatial patterns and distributional controls of total and methylated mercury off the Lena River in the Laptev Sea sediments
  • 2022
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 238
  • Tidskriftsartikel (refereegranskat)abstract
    • A warmer climate is predicted to accelerate the export of mercury (Hg) from Siberian rivers to the Arctic Ocean, yet there is a dearth of process-oriented studies on the speciation and fate of Hg in the shelf sea system. Here, we present data on total Hg (HgT) and methylmercury (MeHg) in Laptev Sea surface sediments along a cross-shelf transect starting at the mouth of the Lena River. Concentrations of HgT along the 330 km cross-shelf transect ranged within a fairly narrow span from 480 to 150 pmol g(-1) d.w., while concentrations of MeHg decreased one hundredfold from 13 pmol g(-1) d.w. near the Lena river to 0.095 pmol g(-1) d.w. in the more distall stations. The highest concentrations of HgT and MeHg were observed close to the river delta and were associated with a high supply of organic carbon (OC). Enrichment of the OC normalized HgT concentration (HgTOC) and depletion of the OC normalized MeHg concentration (MeHgOC) across the shelf suggests bulk OC content to not be the only driver of the HgT and MeHg spatial distributions. Based on correlations observed between HgTOC and MeHgOC and proxies for sediment physics and organic matter pools we suggest the spatial distribution of Hg and MeHg to also be influenced by hydrodynamic sorting of riverine-derived material. For MeHg, depletion of the MeHgOC across the shelf is likely driven by the trapping of terrestrial MeHg in sediments close to the river delta before it is degraded in the water column.
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47.
  • Luis Mas, Jose, et al. (författare)
  • Analysis of a major Aeolian dust input event and its impact on element fluxes and inventories at the DYFAMED site (Northwestern Mediterranean)
  • 2020
  • Ingår i: Marine Chemistry. - : ELSEVIER. - 0304-4203 .- 1872-7581. ; 223
  • Tidskriftsartikel (refereegranskat)abstract
    • Continental dust can be suspended and transported by the wind, reaching seawater masses far away from its source. The deposition of the aerosols on the ocean surface can alter the abundance of chemical species in the water column and contribute to element inventories in seafloor sediments. A major Saharan dust intrusion into the Western Mediterranean Sea was recorded at the DYFAMED site (Ligurian Sea) in 20th February 2004. We determined the influence of this dust event on the concentration of 30 minor and trace level elements (TE) in sinking particles collected by sediment traps deployed at 200 m and 1000 m depth, and how a dust flux event like this contributed to the exchange of TE, including Fe, with the water column during major dust events. With coupled sediment traps and aerosol samples, we assessed the short-term implications of dust events in the water column. The event produced a flux of fast (>111 m d(-1)) and slow ( < 20 m d(-1)) sinking dust particles, detected during 3 weeks at 200 m and 4 weeks at 1000 m depth. Additionally, the obtained results of element concentrations and particles flux show that a single dust deposition event can produce a sinking flux equivalent to annual deposition rates of elements relevant to biogeochemical cycles and/or pollution studies: (>60% for Cr and Cu, >70% for Al, > 80% for Ni and Zn, > 90% for V and Mn, > 100% for Fe and Pb). The corresponding Enrichment Factors (EF) for the minor and TE analyzed in the sediment traps during the dust event were calculated. EF was used to determine how minor and trace element concentrations in sinking particles vary. The values ranged between 0.35 and 421 in both 200 m and 1000 m sediment traps. For most of the analyzed elements, the obtained EF values were higher than 1. On the contrary, V, Y, Zr, Nb, and Ce showed EF similar to 1 while Cr, Ni, Cu, Zn, Sn, and Pb showed EF < 1. Despite the variability in the EF values, vertical fluxes integrated during the dust deposition event increased from 200 m to 1000 m, except for I, which decreased. This contrasts strongly with the element fluxes integrated for the complete sampling period, which decrease or increase from 200 m to 1000 m, depending on the element. This suggests that sinking dust particles were acting generally as sinks of the TE. We conclude that, apart from I, a substantial portion of the elements from atmospheric dust input from a single deposition event can reach the mesopelagic layer of the Western Mediterranean basin without increasing the budget of those elements in the water column.
  •  
48.
  • Matrai, P.A., et al. (författare)
  • Are high Arctic surface microlayers a potential source of aerosol organic precursors?
  • 2008
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 108:1-2, s. 109-122
  • Tidskriftsartikel (refereegranskat)abstract
    • Particulate organic matter, including microorganisms, small water-insoluble particles and microaggregates, can form a substantial part of the summer aerosol over the open leads of the central Arctic Ocean. The increased presence of leads during the summer melt increases the biological activity of the region possibly resulting in accumulation of organic material, especially in the surface microlayer. Preferential microlayer enrichment of particulate and dissolved organic matter and gases might be reflected in derived aerosols. The subsurface seawater and microlayer concentrations were determined for dimethyl sulfide (DMS) and its biogenic precursor dimethylsulfoniopropionate (DMSP), dissolved combined amino acids (DCAA) and individual aminoacids, proteins, chlorophyll a (chl a) and bacterial cells as well as bacterial production. Enrichment factors and surface excess concentrations in the surface microlayer were calculated. Concentrations of particulate and dissolved DMSP, chl a-containing material, and bacterial cells were consistently enriched in arctic lead microlayers at 89°N in August 2001. DMS, protein and DCAA concentrations, however, were not in excess in surface microlayers, although proteins were occasionally enriched. The average mole % DCAA composition was similar in subsurface and microlayer water. Enrichment spikes and excess concentrations followed freezing events and did not co-occur with enhanced bacterial production.
  •  
49.
  • Mattson, Erik, 1980, et al. (författare)
  • The relationship between biophysical variables and halocarbon distributions in the waters of the Amundsen and Ross Seas, Antarctica
  • 2012
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 140, s. 1-9
  • Tidskriftsartikel (refereegranskat)abstract
    • Little is known regarding the distribution of volatile halogenated organic compounds (halocarbons) in Antarctic waters and their relation to biophysical variables. During the austral summer (December to January) in 2007-08 halocarbon and pigment concentrations were measured in the Amundsen (100-130 degrees W) and Ross Sea (158 degrees W-160 degrees E). In addition, halocarbons were determined in air, snow and sea ice. The distribution of halocarbons was influenced to a large extent by sea ice, and to a much lesser extent by pelagic biota. Concentrations of naturally produced halocarbons were elevated in the surface mixed layer in ice covered areas compared to open waters in polynyas and in the bottom waters of the Ross Sea. Higher concentrations of halocarbons were also found in sea ice brine compared to the surface waters. Incubations of snow revealed an additional source of halocarbons. The distribution of halocarbons also varied considerably between the Amundsen and Ross Seas, mainly due to the different oceanographic settings. For iodinated compounds, weak correlations were found with the presence of pigments indicative of Phaeocystis, mainly in the Ross Sea. Surface waters of the Amundsen and Ross Seas are a sink for bromoform (saturation anomalies, SA, -83 to 11%), whereas sea ice was found to be both a source and sink (SA -61-97%). In contrast, both surface waters and sea ice were found to be a source of chloroiodomethane (SA -6-1 200% and 91-22 000 resp.). Consequently, polar waters can have a substantial impact on global halocarbon budgets and need to be included in large-scale assessments. (C) 2012 Elsevier B.V. All rights reserved.
  •  
50.
  • Nerentorp, Michelle, 1986, et al. (författare)
  • Mercury flux over West Antarctic Seas during winter, spring and summer
  • 2017
  • Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203 .- 1872-7581. ; 193, s. 44-54
  • 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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