Marine Chemistry最新文献

{"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}

{"title":"Tracking suspended particulate organic matter biochemistry from glacial meltwater runoff to coastal waters of an Antarctic fjord","authors":"Claudia Parodi ,&nbsp;Luis Cerpa ,&nbsp;Zhuoyi Zhu ,&nbsp;Jing Zhang ,&nbsp;Pablo Muniz ,&nbsp;Natalia Venturini","doi":"10.1016/j.marchem.2024.104455","DOIUrl":"10.1016/j.marchem.2024.104455","url":null,"abstract":"<div><div>Increased glacier melting runoff in Antarctica involves intensification of freshwater, nutrients, sediments and organic matter inputs from land to the sea, which is impacting coastal ecosystems. Basic environmental characteristics of water and biochemical composition of suspended particulate organic matter (POM) both in the proglacial melting runoff system (PROGLARS) of Collins Glacier and marine surface waters of Collins Bay was studied based on organic biopolymers and molecular level analysis of amino acids (AAs), to discern among sources and degradation state in the two environments. Hierarchical Clustering Analysis revealed that PROGLARS stations and marine stations form two distinct groups in terms of water physicochemical characteristics and suspended POM biochemical composition. These differences are the consequence of low restricted contribution of freshwater from Collins Glacier runoff into the coastal-marine environment. Our results evidenced low concentrations of terrestrial suspended POM in marine waters of Collins Bay mainly attributed to low meltwater inputs between the 1st and 7th of February 2018. In terms of macromolecular composition, the predominance of proteins, denote the labile nature of suspended POM in the two environments. Suspended POM in Collins Bay is labile, poorly degraded, representing a protein supplemented food resource, with high energetic value and easily assimilated by heterotrophic marine organism. AAs composition supported less degraded suspended POM derived from marine phytoplankton in surface waters of Collins Bay, whereas, great degradation of suspended POM in the proglacial runoff system of Collins Glacier. Changes in the biochemistry of suspended POM caused by glacial melting and retreat, may affect food features and availability, the productivity of ecosystems, and ultimately, the capacity of Antarctic fjords to act as carbon sinks and climate regulators. Considering low influence of Collins Glacier meltwater in coastal marine waters of Collins Bay, due to the relatively slow retreat of Collins Glacier and low development of its meltwater runoff system, the results of our work are relevant as baseline information for comparison with other Antarctic fjords. Further knowledge about meltwater runoff and suspended POM input dynamics in Antarctic coastal ecosystems, is critical, particularly in areas prone to undergo increased glacier melting in the following decades.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104455"},"PeriodicalIF":3.0,"publicationDate":"2024-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323957","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 distribution of dissolved free amino acids in three Iberian Atlantic estuaries","authors":"Valentina Amaral ,&nbsp;Jesús Forja ,&nbsp;Barbara Steger-Mähnert ,&nbsp;Gerhard J. Herndl ,&nbsp;Cristina Romera-Castillo","doi":"10.1016/j.marchem.2024.104456","DOIUrl":"10.1016/j.marchem.2024.104456","url":null,"abstract":"<div><p>Rivers and estuaries are the main link between land and ocean, transferring significant amounts of dissolved organic carbon. These ecosystems receive large amount of dissolved organic matter (DOM) from diverse sources, both allochthonous and autochthonous. Within this pool, dissolved free amino acids (DFAA) represent the most labile fraction, offering valuable insights into DOM composition and diagenetic processes. Our study focused on three Iberian Atlantic estuaries—Guadalquivir, Guadiana, and Tinto-Odiel— that differ in hydrology, land use and DOM sources. We studied the longitudinal distribution of DFAA and their response to tidal cycles across these estuaries. Despite similar DFAA concentrations between estuaries (176.6 nM to 1770 nM) were found, variations in specific amino acids like glutamic acid, taurine, and aspartic acid pointed to a substantial influence of terrestrial inputs in Guadalquivir and Guadiana estuaries and an anthropogenic influence in Tinto-Odiel. Predominant amino acids—serine, glycine, ornithine, and asparagine —comprised more than 50 mol% of the estuarine DFAA pool. The dominance of serine, glycine, and ornithine indicated substantial DOM degradation, possibly associated with the loss of labile DOM during estuarine transport. Concurrently, asparagine prevalence was linked to allochthonous DOM input particularly associated with terrestrial runoff, lateral input, and anthropogenic activities at estuarine margins. Our results underscore the impact of tidal cycles on DFAA distribution and emphasize the potential of DFAA in unraveling estuarine DOM dynamics and their role as indicators of reactivity and composition in estuarine biogeochemistry.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104456"},"PeriodicalIF":3.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142271942","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":"A comparative study of optical and size properties of dissolved organic matter in the lower Mississippi River and Pearl River","authors":"Zhengzhen Zhou ,&nbsp;Hui Lin ,&nbsp;Eurico J. D'Sa ,&nbsp;Laodong Guo","doi":"10.1016/j.marchem.2024.104453","DOIUrl":"10.1016/j.marchem.2024.104453","url":null,"abstract":"<div><p>Monthly water samples were collected from the lower Mississippi and Pearl Rivers between January 2009 and August 2011 to investigate the heterogeneity in the dynamic variations of dissolved organic carbon (DOC), colloidal organic carbon, chromophoric and fluorescence dissolved organic matter (CDOM and FDOM), PARAFAC-derived fluorescent components, and other optical properties including spectral slope, specific UV absorbance (SUVA), and fluorescence indices between the two contrasting river systems. The lower Mississippi River exhibits relatively lower concentrations of DOC (306 ± 41 μM C) and CDOM (27.9 ± 5.7 m⁻¹ at 254 nm), featuring lower aromaticity (indicated by SUVA₂₅₄) and apparent molecular weight (or higher spectral slope) with weak seasonal variability. The Pearl River, in contrast, has elevated levels of DOC (537 ± 212 μM C) and CDOM (66.4 ± 31.4 m⁻¹), characterized by higher aromaticity, higher molecular weight, and significant seasonality, primarily originating from soil-derived allochthonous sources. The abundance of the &gt;1 kDa colloidal DOC was, on average, 58 ± 3 % of the bulk DOC in the lower Mississippi River and 68 ± 6 % in the lower Pearl River. The &gt;1 kDa high-molecular weight DOM (HMW-DOM) consistently had lower spectral slope and biological index (BIX) values, but higher humification index (HIX) values compared to both bulk DOM and low-molecular-weight DOM (LMW-DOM) counterparts. These trends could be representative of other similar large and small rivers. Four PARAFAC-derived fluorescent components (three humic-like and one protein-like) were identified for both rivers. A positive correlation between discharge and terrestrial humic-like fluorescent components indicated their dominant allochthonous sources, while the protein-like component decreased with increasing discharge, consistent with its autochthonic source and a dilution effect during high flow seasons. The occurrence of large flood events during the sampling period contributed to large DOC pulses, with DOM of higher aromaticity and HMW-DOM. This has important implications for coastal ocean ecosystems, which are increasingly impacted by river flooding events under changing climate conditions. Our results also provide an improved understanding of DOM dynamics in two representative rivers and establish a baseline dataset for future studies to assess changes in sources and composition of DOM and their impacts on the coastal ocean in response to climate, hydrological, and anthropogenic influences.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104453"},"PeriodicalIF":3.0,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142243413","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":"Two-dimensional determination of dissolved manganese in sediment porewaters","authors":"Aurélia Mouret ,&nbsp;Constance Choquel ,&nbsp;Aubin Thibault de Chanvalon ,&nbsp;Florian Cesbron ,&nbsp;Thierry Jauffrais ,&nbsp;Didier Jézéquel ,&nbsp;Patrick Launeau ,&nbsp;Anthony Barbe ,&nbsp;Romain Levrard ,&nbsp;Alan Nicol ,&nbsp;Céline Charbonnier ,&nbsp;Edouard Metzger","doi":"10.1016/j.marchem.2024.104454","DOIUrl":"10.1016/j.marchem.2024.104454","url":null,"abstract":"<div><p>We present a new method for imaging dissolved manganese at millimeter scale by coupling DET (diffusive equilibrium in thin film) and colorimetric techniques. The method is an adaptation of the porphyrin approach for the measurement of dissolved Mn by substitution of Mn(II) and Mn(III) to Cd in the Cd(II)–POR complex. Optimization of the Cd-POR concentrations was required for transposition to 2D-DET. A commercial flatbed scanner and a hyperspectral camera were used for imaging. Using the hyperspectral camera, detection limit is about 5 μM and measuring range is up to 520 μM. The method was applied on the field in a tidal mudflat of the French Atlantic coast and in sediments inhabited by polychaetes. These first images allowed to precisely describe two-dimensional millimeter features such as burrows and highlighted the role of bioirrigation in benthic Mn fluxes. This new technique offers the possibility to investigate the reactivity of microenvironments towards dissolved Mn in two dimensions in a wide range of laboratory and <em>in situ</em> studies using a non-destructive tool.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104454"},"PeriodicalIF":3.0,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0304420324001051/pdfft?md5=d3dee2023242a4aa1fbe4587bffaa871&pid=1-s2.0-S0304420324001051-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142244156","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":"Vanadium redox speciation in the acid-extractable phase of Krka River estuary surface sediment","authors":"Lucija Knežević ,&nbsp;Nuša Cukrov ,&nbsp;Elvira Bura Nakić","doi":"10.1016/j.marchem.2024.104452","DOIUrl":"10.1016/j.marchem.2024.104452","url":null,"abstract":"<div><p>This study investigated the redox speciation and mobility of V in the acid-extractable fraction of surface sediments from the Krka River estuary using an optimized IC-UV/Vis analytical method. The separation of V(IV) and V(V) redox species was done using anion-exchange based chromatographic method, while pseudo-total V concentrations were measured using HR ICP-MS analytical instrumentation. Extracted V concentrations from the sediment fraction (pH = 5, HCl) and determined pseudo-total V concentrations were used to calculate the Enrichment Factor (EF) and Risk Assessment Code (RAC), indicating potential anthropogenic influence and environmental risk. A simple PHREEQC model was developed to asses V speciation in the oxic bottom seawater layer simulating possible remobilization of the leached sediment phase. The results of the study show that minor fraction of V is present in the acid-extractable phase across the surface sediment of Krka River estuary. Higher V mobility is mostly observed at locations rich with clay minerals, terrigenous input, and carbonates. Anthropogenic influence was linked to higher enrichment but lower mobility, suggesting binding to less mobile sediment phases (reducible, organic and residual fractions). The predominance of reduced V(IV) species in the acid-extractable sediment fraction indicates a potentially low V toxicity risk in the sediments of Krka River estuary, even in cases of high potential remobilization of V. However, the model predicted complete oxidation of V(IV) to V(V) upon remobilization into the oxic bottom water layer. This highlights the complexity of V behavior in natural estuarine systems, where the toxicity risks of possible V remobilization still remain unclear. Results of this study demonstrate the need for the strengthening efforts in speciation of V in the mobile sediment phase to obtain a cohesive outlook on its potential toxicity and biogeochemical cycling.</p></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104452"},"PeriodicalIF":3.0,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142271941","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}