Marine Chemistry最新文献

{"title":"Dynamic manganese cycling in the northern Gulf of Mexico","authors":"Jessalyn E. Davis ,&nbsp;Rebecca S. Robinson ,&nbsp;Emily R. Estes ,&nbsp;Veronique E. Oldham ,&nbsp;Evan A. Solomon ,&nbsp;Roger P. Kelly ,&nbsp;Katherine E. Bell ,&nbsp;Joseph A. Resing ,&nbsp;Randelle M. Bundy","doi":"10.1016/j.marchem.2024.104466","DOIUrl":"10.1016/j.marchem.2024.104466","url":null,"abstract":"<div><div>Transport processes along the river-ocean continuum influence delivery of nutrients, carbon and trace metals from terrestrial systems to the marine environment, impacting coastal primary productivity and water quality. Although trace metal transformations have been studied extensively in the Mississippi River Delta region of the Northern Gulf of Mexico, investigations of manganese (Mn) and the presence of ligand-stabilized, dissolved manganese (Mn(III)-L) and its role in the transformation of trace elements and organic matter during riverine transport and estuarine mixing have not been considered. This study examined the chemical speciation of dissolved and particulate Mn in the water column and sediment porewaters in the Mississippi River and Northern Gulf of Mexico in March of 2021 to explore transformations in Mn speciation along the river-ocean continuum and the impact of different processes on the distribution of Mn. Total dissolved Mn concentrations were highest in the Mississippi River and decreased offshore, while Mn(III)-L contributed most to the dissolved Mn pool in near-shore waters. Porewater profiles indicated that ligand stabilization prevented dissolved Mn(III) reduction below the depth of oxygen penetration and in the presence of equimolar dissolved iron(II). Dissolved Mn(III)-L was enriched in bottom waters at all Northern Gulf of Mexico stations, and diffusive flux modelling of porewater dissolved Mn suggested that reducing sediments were a source of dissolved Mn to the overlying water column in the form of both reduced Mn(II) and Mn(III)-L. A simple box model of the Mn cycle in the Northern Gulf of Mexico indicates that Mn(III)-L is required to balance the Mn budget in this region and is an integral, and previously unconsidered, piece of the Mn cycle in the Northern Gulf of Mexico. The presence of Mn(III)-L in this system likely has an outsized impact on trace element scavenging rates, oxidative capacity, and the carbon cycle that have not been previously appreciated.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104466"},"PeriodicalIF":3.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracing marine and terrestrial biochemical signatures of particulate organic matter in an Arctic fjord (Kongsfjorden)","authors":"Archana Singh ,&nbsp;Anand Jain ,&nbsp;Richa Singh ,&nbsp;Keisham S. Singh ,&nbsp;Biswajit Roy ,&nbsp;Manish Tiwari ,&nbsp;Divya David T. ,&nbsp;Ashok Jagtap","doi":"10.1016/j.marchem.2024.104468","DOIUrl":"10.1016/j.marchem.2024.104468","url":null,"abstract":"<div><div>Arctic fjords are hotspot for organic matter (OM) transformation and storage, however, the composition and sources of the particulate organic matter (POM) are still not completely understood. Further, due to the ongoing enhancement in the glacier melting, runoff, and precipitation, the coastal Arctic is expecting considerable increase in POM inputs. Therefore, we investigated the biochemical composition of the POM through the application of stable isotopes, C:N ratio, and biomolecules, across different regions and depths in Kongsfjorden (Svalbard) during the late-summer. We observed that Kongsfjorden-POM was characterized by low δ¹³C (−29.0 to −26.7 ‰) with similar values at different locations (inner to outer) of the fjord at each depth. However, C:N ratio showed increasing trend (5.7 to 10.9) from outer to inner fjord indicating marine to terrestrial transition. Monosaccharide distribution (such as fucose, galactose, arabinose, xylose, ribose, and rhamnose) and their diagnostic ratios supported the marine versus terrestrial gradient in the POM characteristics in the surface water across the fjord. Only the outermost station showed consistent biochemical distribution indicative of phytoplanktonic sources in the POM, while the rest of the fjord showed mixed signatures of marine and terrestrial sources. Higher abundance of mannuronic acid (26.6–50.8 mol%) at the middle and bottom depths highlighted possible macroalgal contribution to the POM. The stratified surface water had a relatively higher (0.5–2 ‰) δ¹³C and carbohydrates (40–65 μg/L) than the middle and bottom depths, with a strong positive correlation between δ¹³C and particulate carbohydrates, indicating a stratification-induced distribution of POM. The study showed the importance of non-phytoplanktonic OM sources, such as terrestrial, freshwater and macroalgae POM in the fjord water column, and the fate of labile (carbohydrates) fraction that predominates in stratified surface waters. Therefore, the future warm and wet Arctic will most likely lead to changes in the fate of the organic matter in the fjord water.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104468"},"PeriodicalIF":3.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Boron to salinity ratios in the Fram Strait entering the Central Arctic: The role of sea ice formation and future predictions","authors":"Samantha Rush ,&nbsp;Penny Vlahos ,&nbsp;Chang-Ho Lee ,&nbsp;Kitack Lee ,&nbsp;Lauren J. Barrett","doi":"10.1016/j.marchem.2024.104463","DOIUrl":"10.1016/j.marchem.2024.104463","url":null,"abstract":"<div><div>The Arctic Ocean's sea ice loss dynamically impacts carbon uptake potential, as assessed through measured carbonate parameters, such as total alkalinity. In the open ocean, boron (B) is the third largest contributor to alkalinity via borate and is usually accounted for through the conservative boron to salinity ratio (B/S), and not directly measured. Here, we present findings on non-conservative boron dynamics, that results in significant B/S deviations, observed in ice melt zone waters, snow, slush, brine, and annual sea ice (<em>n</em> = 169) in the Fram Strait entering the Central Arctic. These samples were collected during the onset of the melt season on the 2023 ARTofMELT expedition, covering a wide practical salinity range (2–59). Barring snow, the average B/S ratio across the study was 0.1321 ± 0.0032 mg kg⁻¹ ‰⁻¹, similar to the mean B/S ratio measured amongst several polar water masses near Iceland, as well as the accepted B/S for other ocean regions. Results indicate minor deviations from accepted B/S ratios (indicating conservative behavior) across the sample practical salinity range and reflect an uncertainty in the borate contribution to total alkalinity of less than 2.9 μmol kg⁻¹ at in-situ temperatures. B fractionation appears to occur during sea ice formation, causing greater B in the sea ice reservoir whereas brine, slush, lead, and under-ice water reservoirs are depleted in B. As such, under-ice and lead, brine, and slush samples all had measured B/S ratios (0.1305 ± 0.0011, 0.1305 ± 0.0018, and 0.1304 ± 0.0017 mg kg⁻¹ ‰⁻¹, respectively) lower than the established ratio whereas the average sea ice B/S ratio (0.1331 ± 0.0035 mg kg⁻¹ ‰⁻¹) was closest to accepted values (0.1336 ± 0.0005 mg kg⁻¹ ‰⁻¹). Arctic open ocean samples also had a lower B/S ratio (0.1304 ± 0.0014 mg kg⁻¹ ‰⁻¹). Our findings, together with a previous Arctic B ice study, suggest that B (probably in the form of B(OH)₄⁻) is incorporated into authigenic CaCO₃ minerals, replacing CO₃²⁻ within the mineral lattice during sea ice formation. This process consequentially lowers the B/S ratio in the open Arctic Ocean, compared to the established global ocean ratio. Nevertheless, the incorporation of B into the sea ice reservoir does not fully account for the deficit of B in the Arctic Ocean samples, suggesting further accounting of B Arctic pathways is necessary. In future climate scenarios involving increased sea ice melt, the transition from multiyear to annual sea ice, permafrost thaw, and increased riverine discharge, the behavior of B in the Arctic Ocean is expected to become more dynamic.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104463"},"PeriodicalIF":3.0,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biogeochemical sulfur transformations in the cohesive and permeable tidal flat sediments of Jade Bay (North Sea)","authors":"Alexey Kamyshny Jr ,&nbsp;Debora Sela ,&nbsp;Rotem Klein ,&nbsp;Alexandra V. Turchyn ,&nbsp;Gilad Antler ,&nbsp;Holger Freund","doi":"10.1016/j.marchem.2024.104464","DOIUrl":"10.1016/j.marchem.2024.104464","url":null,"abstract":"<div><div>Intertidal flats are highly productive coastal marine ecosystems which are affected by fast changes in environmental conditions and host dynamic biogeochemical cycles in their sediments. Bioturbation by burrowing organisms and roots of plants strongly affects speciation and cycling of redox-sensitive elements in intertidal sediments. In this work, we have studied the impact of sediment type and vegetation on the cycling of redox-sensitive elements including sulfur, iron, and manganese in sandy and muddy tidal flats sediments in the Jade Bay (North Sea) and adjacent area. The redox speciation of these elements was analyzed in the pore-waters and the total sediment. The isotopic compositions of sulfur species were measured in non-vegetated sediments and in sediments which are inhabited by various plants. In the cohesive sediments, which are not affected by vegetation, a decrease in sulfate concentration, coupled with the presence of relatively high concentrations of hydrogen sulfide in the pore-waters and the presence of sulfide minerals as well the isotopic compositions of sulfur species are consistent with fast rates of sulfate reduction in the sediments. In the cohesive sediments affected by roots of <em>Salicornia stricta</em> and sediments desiccation, a cryptic sulfur cycle, which is characterized by microbial sulfate reduction coupled to fast reoxidation of hydrogen sulfide by Fe(III) (hydr)oxides and, possibly, by oxygen is present. Below the roots penetration depth, speciation of redox-sensitive elements is similar to those in the baren sediments. In the cohesive sediments affected by the roots of <em>Spartina anglica</em> and <em>Triglochin maritima</em>, which have longer roots, a cryptic sulfur cycle was detected in the upper 30 cm of sediments. At the sites that are characterized by permeable surface sediments and alternating permeable and cohesive layers in the deeper sediments, the composition of the sediment has a similar or even more significant impact on the speciation of the redox-sensitive elements than penetration of relatively weak roots of <em>Spartina anglica</em>. These sediments are characterized by the formation of hydrogen sulfide and sulfide oxidation intermediates in the cohesive layers and their diffusion to (and oxidation at) the boundaries between cohesive and permeable sediments. We conclude that in the cohesive sediments, the penetration of roots and desiccation leads to the formation of overall oxidized conditions, while in the sediments with alternating layers, permeability may provide a more significant control for speciation of redox-sensitive elements.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104464"},"PeriodicalIF":3.0,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corrigendum to “Characterizing the stable oxygen isotopic composition of the Southeast Indian Ocean” [Marine Chemistry 262 (2024) 104397]","authors":"Ryan H. Glaubke ,&nbsp;Amy J. Wagner ,&nbsp;Elisabeth L. Sikes","doi":"10.1016/j.marchem.2024.104460","DOIUrl":"10.1016/j.marchem.2024.104460","url":null,"abstract":"","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104460"},"PeriodicalIF":3.0,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatial and temporal dynamics of groundwater biogeochemistry in the deep subsurface of a high-energy beach","authors":"Anja Reckhardt ,&nbsp;Rena Meyer ,&nbsp;Stephan L. Seibert ,&nbsp;Janek Greskowiak ,&nbsp;Magali Roberts ,&nbsp;Simone Brick ,&nbsp;Grace Abarike ,&nbsp;Kojo Amoako ,&nbsp;Hannelore Waska ,&nbsp;Kai Schwalfenberg ,&nbsp;Iris Schmiedinger ,&nbsp;Oliver Wurl ,&nbsp;Michael Ernst Böttcher ,&nbsp;Gudrun Massmann ,&nbsp;Katharina Pahnke","doi":"10.1016/j.marchem.2024.104461","DOIUrl":"10.1016/j.marchem.2024.104461","url":null,"abstract":"<div><div>Intertidal sandy beach systems are considered complex biogeochemical reactors. At beach sites that are subject to high tidal and wave energy, seawater circulation can reach tens of meters deep into the subsurface and changing environmental conditions are assumed to lead to dynamic groundwater flow paths, saltwater-freshwater mixing zones, and a spatio-temporally variable groundwater biogeochemistry. Previous studies mainly focused on the upper meters of subterranean estuaries (STE), while the deep subsurface remained a black box. This study presents spatial (cross-shore) and temporal (∼ six-weekly, over 1.5 years) dynamics of the groundwater biogeochemistry that were observed down to 24 m below the ground surface (mbgs) of a sandy high-energy beach on Spiekeroog Island (Germany).</div><div>In addition to redox conditions along a cross-shore transect ranging from oxic to Fe oxide reducing/slightly sulfidic, we found a previously unknown, distinct vertical redox zonation as well. Temporal variations of the biogeochemistry within low salinity groundwater at the most landward station close to the dune base were mainly driven by storm flood related seawater infiltration. Around the high water line, the extent of the upper saline plume (USP) varied over time. Furthermore, temporal dynamics of the O₂ saturation at 6 mbgs indicated a seasonally shifting depth of the oxycline at this location. In the lower intertidal zone, groundwater solute concentrations displayed a temporally variable zone of deep freshwater discharge.</div><div>Regarding the impact of the deep STE on the groundwater biogeochemistry of the discharge zone, our data revealed that nutrient, Mn, and Fe release along the deep flow paths through the USP towards the discharge zone was limited, likely due decreasing availability of labile organic matter and subsequent slowing down of metabolic processes with depth. High concentrations of metabolites in the upper ∼ 2 mbgs of the discharge zone were, therefore, rather attributed to the incorporation of labile organic matter during continuous and storm flood related sediment relocation and/or the contribution of older waters, e.g., the subtidal saltwater wedge.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104461"},"PeriodicalIF":3.0,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbonate system and acidification of the Adriatic Sea","authors":"Carolina Cantoni ,&nbsp;Cinzia De Vittor ,&nbsp;Jadran Faganeli ,&nbsp;Michele Giani ,&nbsp;Nives Kovač ,&nbsp;Alenka Malej ,&nbsp;Nives Ogrinc ,&nbsp;Samo Tamše ,&nbsp;Valentina Turk","doi":"10.1016/j.marchem.2024.104462","DOIUrl":"10.1016/j.marchem.2024.104462","url":null,"abstract":"<div><div>Although the marginal seas represent only 7 % of the total area of the ocean, CO₂ fluxes are important for the carbon budget, exposing them to the intense process of anthropogenic ocean acidification. The Adriatic Sea is currently a CO₂ sink (−0.5 to −1 mol C m⁻² y⁻¹) with an annual flux comparable to the net sink rates in the NW Mediterranean. Based on a comparison of two winter cruises carried out in the 25-years interval between 1983 and 2008, an acidification rate of 0.003 pH_T units y⁻¹ was estimated in the northern Adriatic which is similar to the Mediterranean open waters (with recent estimations of −0.0028 ± 0.0003 pH_T units y⁻¹) and the surface coastal waters (−0.003 ± 0.001 and − 0.0044 ± 0.00006 pH_T units y⁻¹). The computed Revelle factor for the Adriatic Sea (approximately 10) indicates that the buffer capacity is rather high and that the waters do not appear to be particularly exposed to acidification. Total alkalinity (TA) in the Adriatic (2.6–2.7 mmol kg⁻¹) is in the upper range of TA measured in the Mediterranean Sea. This is primarily due to the riverine inputs which transport carbonates dissolved from the Alpine dolomites and karstic watersheds. The Adriatic Sea is the second sub-basin (319 Gmol y⁻¹), following the Aegean Sea (which receives the TA contribution from the Black Sea), that contribute to the riverine TA discharges into the Mediterranean Sea. About 60 % of the TA inflow into the Adriatic Sea is attributed to discharge from the Po River with a TA of ∼3 mmol kg⁻¹ and TA decreases with increasing salinity. The north Adriatic dense water spreading and cascading is an efficient mechanism for exporting TA and DIC at depth, from the northern Adriatic towards the bottom of the South Adriatic Pit and possibly to the eastern Mediterranean. Saturation states indicate that the waters of the Adriatic are supersaturated throughout the year with respect to aragonite (Ω_Ar). However, the saturation state is considerably lower in the bottom water layers, due to the prevalence of the bottom layer and benthic remineralisation in the stratification period. Effects on calcifying organisms and phytoplankton are expected in the future.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104462"},"PeriodicalIF":3.0,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bomb-radiocarbon in the Northern Indian Ocean","authors":"Harsh Raj,&nbsp;Siby Kurian","doi":"10.1016/j.marchem.2024.104459","DOIUrl":"10.1016/j.marchem.2024.104459","url":null,"abstract":"<div><div>Bomb-radiocarbon is a useful tracer to study ocean circulation and air-sea CO₂ exchange processes. In the present study bomb radiocarbon distribution in dissolved inorganic carbon of the Northern Indian Ocean around late 2010s has been evaluated. In the late 2010s surface waters in the Northern Indian Ocean had ∆¹⁴C values ranging between 9 and 17 ‰ which is comparable or even higher than that of the contemporaneous atmospheric ∆¹⁴C values. Water column measurements showed that the bomb ¹⁴C inventory in the Arabian Sea and the Bay of Bengal has increased between 1990s and 2010s. During the same period, the eastern and western equatorial Indian Ocean showed either no change or a slight decline in the water column bomb ¹⁴C inventory. These bomb ¹⁴C inventory values were also used to estimate the air-sea CO₂ exchange rate and net CO₂ flux over the Northern Indian Ocean region. Bomb ¹⁴C-based estimate of net CO₂ flux from the Arabian Sea is 75 ± 24 Tg C yr⁻¹ and the Bay of Bengal is 1 ± 7 Tg C yr⁻¹, which is comparable to the estimates reported by previous investigations in the region. The present observations show that the bomb ¹⁴C is being transferred to the deeper depths of the ocean, emphasizing the need for continued ¹⁴C measurements to gain further insights into subsurface processes in the region.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104459"},"PeriodicalIF":3.0,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sulfur isotopic fractionation during hydrolysis of carbonyl sulfide","authors":"Yasmin Avidani ,&nbsp;Alon Angert ,&nbsp;Chen Davidson ,&nbsp;Xinyu Xia ,&nbsp;Yongli Gao ,&nbsp;Alon Amrani","doi":"10.1016/j.marchem.2024.104458","DOIUrl":"10.1016/j.marchem.2024.104458","url":null,"abstract":"<div><div>Carbonyl Sulfide (OCS) is the most abundant sulfur-containing gas in the atmosphere, and it is used as a proxy for terrestrial gross primary productivity (GPP). Oceans are the major source of OCS to the atmosphere, produced by photochemical and “dark” reactions. Hydrolysis to H₂S and CO₂ is the major removal process of OCS from the ocean's surface. Measuring the sulfur isotope values (δ³⁴S) and the isotopic fractionation (ε) associated with these major OCS sources and sinks could decrease the uncertainties in its fluxes. In the current study, we aim to determine the ε during the hydrolysis process of OCS (ε_h). We used a purge and trap system coupled to a GC/MC-ICPMS to measure δ³⁴S values during hydrolysis under different temperatures (4–40 °C), salinities (0.2–40 g/L), and pH (4–9), representing various natural environmental conditions. In addition, we use the quantum chemical method to calculate the equilibrium ε_h and compare it to the empirical results. Our results for the low salinity (S =0.2 g/L; pH 8.0) water show a temperature dependency of the ε_h from −3.9 ‰ ± 0.2 ‰ (4 °C,) to −2.2 ± 0.6 ‰ (40 °C). The higher fractionation at low temperatures has implication for ice-core data interpretation. However, in natural seawater at 4<span><math><msup><mrow></mrow><mo>°</mo></msup><mi>C</mi></math></span> and 22 °C (S = 40 g/L, pH 8.2) there was no such temperature dependency and the ε_h averaged −2.6 ± 0.3 ‰. Thus, it seems that salinity cancels the temperature effect close to the freezing temperature of water. Varying the pH between 4 and 9 (at 22 °C) did not result in any ε_h trend. Ab-initio calculations suggest that OCS hydrolysis is not controlled by equilibrium. The ε_h values we report will aid in quantifying the impact of OCS's hydrolysis on the observable sulfur isotopic signature of OCS in oceanic and in freshwater environments. This in turn will facilitate more accurate mass-balance calculations for the OCS budget from the ocean to the atmosphere.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104458"},"PeriodicalIF":3.0,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142357597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microplastics in wild Saccostrea cucullata oysters in Sri Lanka: Pollution status and risk assessment","authors":"K.P.G.K.P. Guruge ,&nbsp;K.M.S.N. Abeysinghe ,&nbsp;Tharindu Bandara ,&nbsp;P.B.T.P. Kumara","doi":"10.1016/j.marchem.2024.104457","DOIUrl":"10.1016/j.marchem.2024.104457","url":null,"abstract":"<div><div>Microplastics (MPs) have widely been reported in many marine organisms that cause significant environmental concern. Oysters are known to accumulate MPs through their filter-feeding mechanism yet studies focused on MPs pollution in oysters along with ecological risk assessment are scarce. In this study, we investigated MPs pollution in wild <em>Saccostrea cucullata</em> oysters and assessed the ecological risk of MPs pollution in oysters and their habitats along the southern and western coasts of Sri Lanka. Oyster MPs abundance varied from 0.63 to 2.20 particles g⁻¹ wet weight (ww), which showed a significant positive correlation with MPs abundances in surrounding surface seawater and surface sediment. The average MPs abundances in oysters, surface seawater and surface sediment showed significant spatial differences where high MPs abundances were reported in areas that had high anthropogenic activities. Size classification of MPs revealed that small size (100 μm-1 mm) blue fibres were dominant in oysters, surface seawater and surface sediment likely due to the high abundance of discarded fishing nets in studied areas. The abundance of various polymer types indicated that low-density polyethene polymers were most abundant (oysters, 45.74 %; surface seawater, 42.91 % and surface sediment, 39.62 %). Results of the ecological risk assessment indicated that MPs pollution in the environment was low (Level I). However, MPs pollution in oysters ranged from low to moderate risk levels (Level I-II), where moderate risk was reported in the areas with high MPs contamination. Therefore, our study highlights that mitigation of MPs pollution on the southern and western coast of Sri Lanka is important to alleviate the increasing ecological risk of MPs pollution in <em>Saccostrea cucullata</em>.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104457"},"PeriodicalIF":3.0,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142357598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}