Marine Chemistry最新文献

{"title":"Source contributions to iron cycling in marginal sea: Evidence from Iron isotope compositions of Changjiang Estuary sediments","authors":"Jiao Wang ,&nbsp;Ziwei Sun ,&nbsp;Huamao Yuan ,&nbsp;Jinming Song ,&nbsp;Ning Li ,&nbsp;Chen Li ,&nbsp;Yuanyuan Xiao","doi":"10.1016/j.marchem.2025.104575","DOIUrl":"10.1016/j.marchem.2025.104575","url":null,"abstract":"<div><div>As an important input area of riverine and terrigenous materials in the east coast of China, the knowledge on iron budget of marginal sea sediments in the Changjiang Estuary is significant to understand the iron cycle of marginal sea ecosystems. Iron isotope composition has been recently used as a critical indicator for understanding the iron cycle and biogeochemical processes of the Earth. This study reports the iron isotope variation of two sediment cores from the Changjiang Estuary, i.e., 3100–1 and DH5. The δ⁵⁶Fe values of samples from the core 3100–1 vary from +0.02 ‰ to +0.08 ‰ with an average of +0.05 ± 0.03 ‰, and the δ⁵⁶Fe values of samples from the core DH5 range from +0.02 ‰ to +0.10 ‰, with an average of +0.07 ± 0.05 ‰. The δ⁵⁶Fe values of sediments from these two cores are not significantly correlated with parameters for organic carbon content, chemical weathering, grain size, or redox condition. Together with the Principal Component Analysis, these indicate that source material inputs significantly affect iron isotope compositions in both cores. Meanwhile, the iron isotope compositions of the core DH5 can reflect changes of human activities in the Changjiang Basin. Our findings provide pivotal iron isotope evidence for understanding the marginal sea iron cycle under natural and anthropogenic impacts, offering an important perspective for further studies on the global marginal sea ecosystem.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104575"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465959","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":"Native S from seafloor hydrothermal sites: Messenger for magmatic degassing of metals into submarine hydrothermal systems","authors":"Vesselin Dekov ,&nbsp;Bleuenn Guéguen ,&nbsp;Toshiro Yamanaka ,&nbsp;Andrea Koschinsky ,&nbsp;Sven Petersen ,&nbsp;Sophie A.L. Paul ,&nbsp;Charlotte Kleint ,&nbsp;Wolfgang Bach ,&nbsp;Gert J. de Lange","doi":"10.1016/j.marchem.2025.104585","DOIUrl":"10.1016/j.marchem.2025.104585","url":null,"abstract":"<div><div>Native S⁰ precipitates in form of little chimneys, submarine crater lakes, stains and crusts on sediments, and as crack and vesicle fillings in rocks at the seafloor hydrothermal sites. Unlike the biogenic native S⁰ precipitated in anoxic and euxinic seafloor environment, the seafloor hydrothermal native S⁰ is a result of either disproportionation of magmatic SO₂ (δ³⁴S_sample &lt; δ³⁴S_{terrestrial mantle sulfide}) or synproportionation of magmatic SO₂ and H₂S (δ³⁴S_sample &gt; δ³⁴S_{terrestrial mantle sulfide}). Using it as a proxy for magmatic volatile flux we found out that it carried isotopic signal for magmatic degassing of Zn (δ⁶⁶Zn_sample &lt; δ⁶⁶Zn_{bulk silicate Earth}). Thus, the seafloor hydrothermal native S⁰ provides new isotopic evidence for direct magmatic contribution of metals to seafloor hydrothermal systems and appears to be a messenger for magmatic volatile metal discharge in the ocean.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104585"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145614313","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":"Cobalt mobility in high-energy beach sediments – a view on the redox cascade of trace metals combining in-situ observations and flow-through experiments","authors":"Anja Reckhardt ,&nbsp;Magali Roberts ,&nbsp;Felix Auer ,&nbsp;Moritz Holtappels ,&nbsp;Rena Meyer ,&nbsp;Michael Ernst Böttcher ,&nbsp;Katharina Pahnke","doi":"10.1016/j.marchem.2025.104583","DOIUrl":"10.1016/j.marchem.2025.104583","url":null,"abstract":"<div><div>Intertidal sandy high-energy beach subterranean estuaries (STE) represent complex and dynamic biogeochemical reactors. The aim of our study was to assess trace metal mobility, with a special focus on cobalt (Co), along redox and salinity gradients in the shallow to deep STE of a high-energy beach on Spiekeroog Island (Germany). Co is a micronutrient for phytoplankton growth and characterizing its transformation behavior in such systems contributes to the overall understanding of coastal Co cycling. Groundwater down to 24 m was sampled ∼every 6 weeks between 2022 and 2024 to obtain a high spatial and temporal resolution cross-sectional view on the STE biogeochemistry. Sediments collected from cores were used to determine the sedimentary basis for trace metal cycling. Co concentrations in groundwater revealed a specific mobilization horizon, which was predominantly related to zones of incipient manganese (Mn) reduction. Iron (Fe) reducing conditions resulted in Co fixation in the solid phase, possibly due to accompanying slight net microbial sulfate (SO₄²⁻) reduction and the formation of Co-bearing Fe sulfides or Co sulfide (CoS). Solid phase analyses indicated that the potential for reactive Fe, Mn, and Co mobilization was highest in a former tidal flat sediment layer, which is currently covered by ∼5 m of beach sands and underlain by Pleistocene glacio-fluvial deposits. Co mobilization and fixation behavior observed under in-situ conditions was reproduced in a laboratory flow-through experiment illustrating high release and removal rates of Co along a redox gradient of oxic to Fe and potentially slightly SO₄²⁻ reducing conditions in comparison to the redox-related reactivity of uranium (U), molybdenum (Mo), and rhenium (Re). With regard to coastal element cycling, high-energy beach STEs may favor Co mobilization due to high electron acceptor supply resulting in less reducing conditions and spatially extended intermediate redox levels. Furthermore, discharge of elements like Fe, Mn, and Co may be enhanced by advective groundwater flow in contrast to diffusion-dominated systems, where the exfiltration is more likely to be limited by re-oxidation processes.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104583"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145568514","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":"Seasonal dynamics of DOM diversity and molecular composition in the NW Mediterranean Sea","authors":"Nawal Bouchachi ,&nbsp;Hélène Lavanant ,&nbsp;Carlos Afonso ,&nbsp;Isabelle Schmitz ,&nbsp;Barbara Marie ,&nbsp;Ingrid Obernosterer ,&nbsp;Eva Ortega-Retuerta","doi":"10.1016/j.marchem.2025.104562","DOIUrl":"10.1016/j.marchem.2025.104562","url":null,"abstract":"<div><div>In the Mediterranean Sea, an accumulation of dissolved organic matter (DOM) is observed during the stratified summer period, which is decoupled from the spring phytoplankton maxima. This has been classically explained by nutrient limitation, that hampers prokaryotic DOM uptake of the labile DOM released by phytoplankton. However, relatively high heterotrophic prokaryotic activity in summer led us to hypothesize that the accumulated DOM might be recalcitrant and derived from these microorganisms. To test this, we tracked the seasonality of DOM molecular composition and chemical diversity using FT-ICR MS from 2019 to 2021 in the NW Mediterranean Sea, and framed it using a broad suite of environmental and biological parameters. Our results reveal a clear seasonal variation in DOM molecular composition and diversity in the surface mixed layer. Changes in composition reflected a higher proportion of molecular formulae containing CHO in spring and a higher proportion of molecular formulae containing CHOS and CHONS in summer. Proxies of DOM recalcitrance, such as aromaticity, unsaturation, and molecular size, were higher in summer, confirming our hypothesis of an accumulation of recalcitrant DOM in summer. In parallel, an increase in DOM diversity (as number of total molecular formulae, their relative intensity, their average distance (Dist) in the van Krevelen space and their functional diversity) was observed, suggesting that the accumulated DOM in summer is likely the result of the interplay between different processes including dissolved primary production, photodegradation and prokaryotic activity. Our results may have significant implications for carbon sequestration through the microbial carbon pump in the Mediterranean Sea as this DOM accumulated in the surface is likely to be stored once exported into deep layers.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104562"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096880","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":"Dissolved iron distribution and budget in the Solomon Sea","authors":"Géraldine Sarthou ,&nbsp;Eva Bucciarelli ,&nbsp;Fabien Quéroué ,&nbsp;François Lacan ,&nbsp;Hélène Planquette ,&nbsp;Viet Q. Pham ,&nbsp;Maxime Grand ,&nbsp;Catherine Pradoux ,&nbsp;Martine Rodier ,&nbsp;Sophie Bonnet ,&nbsp;Gérard Eldin ,&nbsp;Sophie Cravatte ,&nbsp;Catherine Jeandel ,&nbsp;Alexandre Ganachaud","doi":"10.1016/j.marchem.2025.104567","DOIUrl":"10.1016/j.marchem.2025.104567","url":null,"abstract":"<div><div>As part of the PANDORA cruise (GEOTRACES GP12), concentrations of dissolved iron (dFe) were measured at 11 stations inside and outside the Solomon Sea, a semi-enclosed sea in the western tropical Pacific, with complex topography and straits, and strong western boundary currents supplying the equatorial current system. These measurements aimed to better assess the various sources of dFe in our study area and the Solomon Sea's potential as a source of dFe for the Equatorial Undercurrent (EUC). A simple box model allows calculating and discussing the fate of the dFe in the different water layers flowing through the Solomon Sea and suggests that the amount of dFe enrichment within the enclosed sea was not significant for the lower thermocline and intermediate waters, indicating that most of the dFe was acquired prior to reaching the Solomon Sea at the entrance and/or that inputs are approximately balanced by scavenging within the basin for these two layers. In contrast, dFe enrichment was significant for the upper thermocline layer and the deep waters, highlighting enrichments from external sources, as well as combination of internal processes, such as scavenging and/or organic complexation. The relative dFe contribution of the Solomon Sea to EUC was 20 %, on average. Other sources might thus provide dFe to the EUC, along the water transport downstream of the Solomon Sea (e.g. Bismarck Sea) or from the northern hemisphere. Diazotrophs such as <em>Trichodesmium</em> might also contribute to the dFe enrichment of the EUC after export and remineralization at depth outside the Solomon Sea.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104567"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145220621","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":"Polyamines as predominant organic basic compounds in the Antarctic Peninsula","authors":"Kentaro Saeki ,&nbsp;Daniel P. Zitterbart ,&nbsp;Kazuya Ikari ,&nbsp;Joseph D. Warren ,&nbsp;Kylie Owen ,&nbsp;Shin-Ichi Ohira ,&nbsp;Kei Toda","doi":"10.1016/j.marchem.2025.104572","DOIUrl":"10.1016/j.marchem.2025.104572","url":null,"abstract":"<div><div>Polyamines, such as putrescine, spermidine, and spermine, are vital for marine microorganisms as nutrients and bioactive compounds. While their presence has been studied in various marine regions, they remain unexamined in the Antarctic region, and no study has compared polyamines with monoamines, another class of organic nitrogen compounds. This study quantified polyamines and monoamines in seawater in the West Antarctic Peninsula region using 4-(<em>N</em>,<em>N</em>-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F) derivatization and HPLC-MS/MS. Polyamines were detected in Antarctica for the first time at sub-μM to μM levels, and it was approximately two orders of magnitude higher than reports from lower-latitude regions. Although total polyamine concentrations did not differ significantly among the five sites sampled, distinct patterns in polyamine composition were observed between the sites. In Wilhelmina Bay, total polyamines exhibited a positive but non-significant association with zooplankton backscatter (NASC), while cadaverine alone correlated significantly (<em>r</em> = 0.53, <em>n</em> = 15, <em>p</em> = 0.04). Our results established a baseline for Antarctic polyamines and revealed bay-to-bay differences in species composition. These baseline observations set the stage for tracking how polyamine dynamics respond to environmental change in the Southern Ocean.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104572"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324718","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":"Copper speciation and its relationship with dissolved organic matter in a hypersaline coastal lagoon","authors":"Maria Sol Hernández-Conesa ,&nbsp;Juan Santos-Echeandía ,&nbsp;Patricia Bernárdez ,&nbsp;Xosé Antón Álvarez-Salgado ,&nbsp;Mar Nieto-Cid ,&nbsp;Paula Sánchez-Marín","doi":"10.1016/j.marchem.2025.104581","DOIUrl":"10.1016/j.marchem.2025.104581","url":null,"abstract":"<div><div>The Mar Menor (SE Iberian Peninsula) is the largest hypersaline coastal lagoon in Europe. This ecosystem is severely affected by anthropogenic impacts, causing the entry of metals and other contaminants. It is well known that total metal concentrations are not good predictors of their bioavailability, and its chemical speciation should be considered. Copper (Cu) is a metal of environmental concern whose speciation is largely controlled by natural organic ligands. The present work aims at studying the chemical speciation of dissolved Cu in the lagoon and its relationship with dissolved organic matter (DOM). For this purpose, 36 water samples were taken in different locations of the lagoon during six environmental surveys in 2021 and 2022. The chemical speciation of dissolved Cu was studied using cathodic stripping voltammetry (CLE-AdCSV), using salicylaldoxime as competing ligand. DOM was characterized by means of elemental composition (C and N), and optical properties (fluorescence and absorbance) in the same samples. Dissolved Cu speciation could be explained by a one ligand model, with ligand concentrations (L_Cu) ranging between 15.89 and 90.82 nM; and conditional stability constants (<span><math><msub><mrow><mi>log</mi><mspace></mspace><mi>K</mi><mo>´</mo></mrow><mrow><msup><mrow><mi>Cu</mi></mrow><mrow><mn>2</mn><mo>+</mo></mrow></msup></mrow></msub></math></span>) varying between 11.36 and 12.92. L_Cu positively and significantly correlated with dissolved organic carbon (DOC) concentration, absorption at 254 nm, and humic-like fluorescence intensity, suggesting that humic materials were the main ligands controlling Cu speciation in this area. In addition, the significant positive correlation found between DOC-normalized L_Cu and the aromaticity index SUVA₂₅₄ indicates that DOM aromaticity can be a good proxy of the metal binding ability of humic DOM. Despite the very high DOC concentrations present in Mar Menor, Cu complexation was similar to that found in other coastal areas with lower DOC, which may be explained by the hypersaline nature of the lagoon.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104581"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145614216","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":"pHT measurements of TRIS buffer solutions in an artificial seawater matrix in the salinity range 5–40 and temperature range 5–40 °C. Part 1: Measurements and data fitting","authors":"Gaëlle Capitaine ,&nbsp;Rieke Schäfer ,&nbsp;Frank Bastkowski ,&nbsp;Daniela Stoica ,&nbsp;Olivier Pellegrino ,&nbsp;Raquel Quendera ,&nbsp;Eric P. Achterberg ,&nbsp;Thibaut Wagener ,&nbsp;Simon L. Clegg ,&nbsp;Steffen Seitz ,&nbsp;Paola Fisicaro","doi":"10.1016/j.marchem.2025.104551","DOIUrl":"10.1016/j.marchem.2025.104551","url":null,"abstract":"<div><div>Spectrophotometric measurements of seawater total pH (<span><math><mi>p</mi><msub><mi>H</mi><mi>T</mi></msub></math></span>) contribute to the knowledge of the oceanic carbonate system, and hence to the assessment of the ocean carbon cycle and the monitoring of ocean acidification. Spectrophotometric measurements rely on the characterization of the indicator dye's second dissociation constant, obtained from measurements on solutions of known <span><math><mi>p</mi><msub><mi>H</mi><mi>T</mi></msub></math></span>. Therefore, Harned cell potentiometric measurements were performed on equimolal TRIS buffers (i.e. buffers containing equal molalities of 2-amino-2-(hydroxymethyl)-1,3-propanediol (TRIS, CAS reference number 77–86-1) and TRIS hydrochloride (TRIS.HCl)), made in an artificial seawater (ASW) matrix. Buffer solutions were prepared in an ASW matrix of nominal practical salinities from 5 to 40, and Harned cell measurements were performed on these solutions at temperatures from 5 °C to 40 °C. This provides, for the first time, <span><math><mi>p</mi><msub><mi>H</mi><mi>T</mi></msub></math></span> values of ASW/TRIS buffers that are consistent for the entire ranges of salinity relevant for oceanographic measurements, and for a wide range of temperature. The work presented includes a comparison of results from three National Metrology Institutes to assess reproducibility, and provides a function allowing the calculation of equimolal ASW/TRIS buffers <span><math><mi>p</mi><msub><mi>H</mi><mi>T</mi></msub></math></span> as a function of salinity, temperature and TRIS buffer molality. This function can be used to derive <span><math><mi>p</mi><msub><mi>H</mi><mi>T</mi></msub></math></span> values for zero TRIS molality, thus representing a pure ASW (i.e. a chemical environment unaffected by the presence of TRIS and TRIS.HCl), and referring to a true <span><math><mi>p</mi><msub><mi>H</mi><mi>T</mi></msub></math></span> scale. These values are needed for the characterization of the second dissociation constant of the dye with perspective of traceability to the International System of units.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104551"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144933633","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":"Factors influencing the variability of stable isotopes of carbon, nitrogen, and sulfur in benthic macrofauna from Admiralty Bay, maritime Antarctic","authors":"Agnieszka Jędruch ,&nbsp;Marcelina Ziółkowska ,&nbsp;Natalia Bulik ,&nbsp;Piotr Paneth ,&nbsp;Ewa Korejwo ,&nbsp;Dominika Saniewska","doi":"10.1016/j.marchem.2025.104564","DOIUrl":"10.1016/j.marchem.2025.104564","url":null,"abstract":"<div><div>This study examines benthic macrofauna from Admiralty Bay, maritime Antarctic, using triple stable isotope approach (<em>δ</em>¹³C, <em>δ</em>¹⁵N, and <em>δ</em>³⁴S) to assess the impact of melting glaciers and human activity on trophic interactions in this unique ecosystem. Four species – the limpet <em>Nacella concinna</em>, the sea urchin <em>Sterechinus neumayeri</em>, the starfish <em>Odontaster validus</em>, and the brittle star <em>Ophionotus victoriae</em> – were analyzed to characterize their isotopic composition and trophic niches. The results indicate that diet and feeding strategies were the main drivers of <em>δ</em>¹³C, <em>δ</em>¹⁵N, and <em>δ</em>³⁴S variability, demonstrating the utility of a multi-isotope approach for revealing diet composition, trophic plasticity, and benthic–pelagic coupling in polar benthic communities. Elevated <em>δ</em>¹³C values, typical of benthic primary producers, and depleted <em>δ</em>³⁴S values, indicative of sulfur derived from sediments, confirmed a strong reliance of benthic macrofauna on benthic food sources. In contrast, decrease in <em>δ</em>¹³C together with higher and typically marine <em>δ</em>³⁴S, can indicate higher contribution of pelagic diet sources. Spatial isotopic patterns further revealed areas influenced by glacial melt and shifting ice conditions, where consumers were relatively enriched in <em>δ</em>¹³C and <em>δ</em>¹⁵N compared to sites with rather open-ocean conditions. Notably, <em>δ</em>³⁴S emerged as a possible early indicator of human-related disturbance, with depletion reflecting increased anthropogenic sulfur inputs and reduced oxygen conditions in benthic habitats linked to nutrient enrichment. Concurrent to ³⁴S-depletion enrichment in ¹⁵N supports the role of nitrogen inputs from human activities. These findings demonstrate that stable isotopic tracers, particularly when incorporating sulfur alongside carbon and nitrogen, provide a powerful tool to detect and interpret ecological responses to both natural and anthropogenic drivers, offering insights into local ecosystem shifts and their broader implications for Antarctic food webs under climate change and growing human pressure.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104564"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096873","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":"Desorption dynamics of black carbon in a subtropical estuary","authors":"Qinghua Zhang ,&nbsp;Weifeng Yang ,&nbsp;Ziming Fang ,&nbsp;Zeheng Lin ,&nbsp;Minfang Zheng ,&nbsp;Mengya Chen","doi":"10.1016/j.marchem.2025.104576","DOIUrl":"10.1016/j.marchem.2025.104576","url":null,"abstract":"<div><div>The geochemical behavior of black carbon (BC) in the estuary system controls the magnitude of riverine BC into coastal seas and thus the budget of BC in the ocean. However, the poor understanding of BC behavior in estuaries prevents us from well quantifying the riverine BC export. Here, eight cruises were conducted in the Jiulong River estuary to delineate the behavior of dissolved black carbon (DBC) determined using the benzenepolycarboxylic acid (BPCA) method, as well as its influence on riverine DBC estimation. DBC showed a range of 1.16–7.88 μmol L⁻¹. On an estuarine scale, DBC correlated negatively with salinity in all cruises (<em>p</em> &lt; 0.05), revealing a dominant dilution effect of seawater during the transport of riverine DBC to the Taiwan Strait. Notably, the continuous addition behavior of DBC was identified in the low salinity zones based on high-solution samplings, attributing to the desorption of soluble BC from particulate matter. Simulation analysis indicated that the desorption followed a pseudo-first-order kinetic law. The kinetic constants varied from 0.053 h⁻¹ to 0.84 h⁻¹ with the maximum in summer. Incorporating desorbed DBC, the annual export rate of riverine DBC was 1.1 Gg yr⁻¹, about 26 % higher than 0.9 Gg yr⁻¹ estimated based on the traditional algorithm (i.e., without addition). The first examination of DBC desorption kinetics provided insights into the behavior of BC in the estuary and the riverine DBC magnitude into the ocean.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104576"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465957","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}