Marine Chemistry最新文献

{"title":"Seasonal variations in mercury species and selenium in plankton from Kagoshima Bay, southern Kyushu, Japan: Impact of active submarine volcanoes on ecosystems","authors":"Takashi Tomiyasu ,&nbsp;Hayato Uwashitomi ,&nbsp;Taijyu Wakimaru ,&nbsp;Hitoshi Kodamatani ,&nbsp;Ryo Kanzaki ,&nbsp;Toru Kobari","doi":"10.1016/j.marchem.2026.104610","DOIUrl":"10.1016/j.marchem.2026.104610","url":null,"abstract":"<div><div>Seawater and plankton sampling were conducted every two months from 2019 to 2022 in the inner and central parts of Kagoshima Bay, where submarine volcanic activity continues at a bottom of 200 m depth in the inner part. Plankton samples were collected using a plankton net, with vertical hauls at depths of 0–140 m and 140–200 m just above the submarine volcano, and at 0–200 m in the central part of the bay. The collected samples were separated into phytoplankton (&lt; 100 mm) and zooplankton (&gt; 100 mm) for analysis of organic mercury, inorganic mercury and total selenium. The inorganic mercury concentrations in phytoplankton and zooplankton collected at the 140–200 m depth just above the submarine volcano were 1.80 ± 0.61 mg kg⁻¹ and 0.47 ± 0.34 mg kg⁻¹, respectively, while organic mercury concentrations were 0.15 ± 0.11 mg kg⁻¹ and 0.16 ± 0.09 mg kg⁻¹, respectively. These values were an order of magnitude higher than those found in plankton samples from the central part of the bay. In the inner part of the bay, the concentrations of these substances increased in summer and decreased in winter, mirroring fluctuations in seawater mercury concentrations, which are influenced by volcanic activity. The selenium concentrations in phytoplankton and zooplankton at 140–200 m above the submarine volcano were 1.64 ± 0.80 mg kg⁻¹ and 1.82 ± 0.86 mg kg⁻¹, respectively, while in the central part, they were 1.17 ± 0.58 mg kg⁻¹ and 1.84 ± 0.67 mg kg⁻¹, respectively. The organic mercury and selenium concentrations were higher in zooplankton than in phytoplankton at the locations of central part and 0–140 m above the fumaroles, which may suggest migration of organic mercury and selenium to higher trophic levels. Conversely, at the location just above the submarine volcano, no significant differences were observed between phytoplankton and zooplankton, and a significant negative correlation (<em>r</em> = −0.72, <em>p</em> &lt; 0.05) was observed between selenium and organic mercury concentrations in zooplankton with high mercury levels. This negative correlation may indicate an antagonistic effect of selenium on the accumulation of organic mercury in zooplankton.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"275 ","pages":"Article 104610"},"PeriodicalIF":2.5,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081236","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":"The distribution of chlorophyll-a degradation derivatives in the Holocene Black Sea and their marine ecological significance","authors":"Wenshuo Zhao ,&nbsp;Junpeng Fu ,&nbsp;Olawale O. Alo,&nbsp;Xiao-Lei Liu","doi":"10.1016/j.marchem.2026.104606","DOIUrl":"10.1016/j.marchem.2026.104606","url":null,"abstract":"<div><div>Chlorophyll-<em>a</em> degradation derivatives (Chl-<em>a</em>-DDs) provide valuable insights into past phytoplankton dynamics. Using a new LC-QToF-MS method, we identified eleven steryl chlorin esters (SCEs), eight oxidative chlorophyll transformation products (OxCs), four reductive chlorophyll transformation products (ReCs), and two cyclopheophorbide derivatives (CPBs) in the Holocene Black Sea sapropel. Total Chl-<em>a</em>-DDs reveal two productivity peaks: post-stratification (∼7.5 ka) and after surface freshening (∼3 ka). ReCs track progressive redox changes, and a peak in the 3¹-meso-pyropheophytin-<em>a</em>/pyropheophytin-<em>a</em> ratio in upper Unit II implies intensified euxinia between ∼5 and 3 ka B.P. Elevated OxCs in Units II and I suggest intracellular oxidation as the dominant chlorophyll transformation pathway. SCEs dominance in Unit III indicates fecal pellet as the primary organic carbon delivery mechanism preceding stratification, while their decline in Units II and I reflects reduced grazing under euxinia. Increase in CPBs under euxinia likely reflects protists' physiological responses to oxidative stress associated with light stress.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"275 ","pages":"Article 104606"},"PeriodicalIF":2.5,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081235","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":"Examining the utility of barium isotopes as a tracer of large-scale seafloor methane venting","authors":"Ethan Petrou ,&nbsp;Luke Bridgestock ,&nbsp;Germain Bayon ,&nbsp;Nolwenn Lemaitre ,&nbsp;Ya-Zhen Wu ,&nbsp;Gideon M. Henderson ,&nbsp;Yu-Te Hsieh","doi":"10.1016/j.marchem.2026.104608","DOIUrl":"10.1016/j.marchem.2026.104608","url":null,"abstract":"<div><div>Periods of increased sedimentary barium (Ba) burial rates have been interpreted as evidence for climate-driven release of methane (CH₄) from sediments in the geological past, yet such interpretations remain ambiguous. Here, we present the first Ba isotope measurements from an active methane seep to directly evaluate whether Ba isotopes in seawater or authigenic carbonates can record Ba release associated with seafloor methane venting. Dissolved Ba concentration ([Ba]) and isotope composition (δ^138/134Ba) were measured in seawater profiles (1 m to 60 m above the seafloor) and in authigenic carbonates collected across the Regab pockmark on the Congo Margin. Seawater over the active methane venting site shows an increase of around 8% in dissolved [Ba] compared to ambient seawater at the Reference Site, indicating detectable benthic Ba release during methane venting. However, the δ^138/134Ba values of these samples (+0.23‰ to +0.42‰) are indistinguishable from ambient seawater, demonstrating that Ba released during methane venting does not impart a resolvable isotopic shift to the water column. An additional isotopically light Ba input may arise from the dissolution of Fe<img>Mn oxyhydroxide phases at the sediment water interface, but this interpretation is based on a single data point and requires further investigation. Authigenic carbonates at sites of high methane flux exhibit markedly lower δ^138/134Ba values (−0.30‰ to +0.20‰) that are markedly lower than seawater, coral carbonates, and published porewater values, indicating a potential Ba isotope fractionation linked to cold-seep carbonate formation. Overall, these findings suggest that Ba isotopes are unlikely to be a reliable tracer of Ba mobilisation associated with methane venting and challenges the interpretation of sedimentary Ba isotope records as indicators of past large-scale methane release.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"275 ","pages":"Article 104608"},"PeriodicalIF":2.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048954","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":"Responses of carbon monoxide photoproduction in surface seawater to environmental changes under simulated solar radiation","authors":"Xuan Ji ,&nbsp;Ming-Liang Zhao ,&nbsp;Yi-Ran Jia ,&nbsp;Cai-Jie Zhang ,&nbsp;Qi-Mei Du ,&nbsp;Jing Zhang ,&nbsp;Gui-Peng Yang","doi":"10.1016/j.marchem.2026.104607","DOIUrl":"10.1016/j.marchem.2026.104607","url":null,"abstract":"<div><div>The ocean is undergoing rapid environmental changes, but how carbon monoxide (CO) photoproduction responds to these changes remains uncertain. Therefore, we used simulated solar radiation to investigate the effects of ocean warming, acidification, deoxygenation, and nitrate concentration changes on CO photoproduction rate in the surface seawater of the Yellow Sea (YS), the East China Sea (ECS), the South China Sea (SCS), and the eastern Indian Ocean (EIO). Ultraviolet radiation contributed more than 90% to CO photoproduction. Dissolved organic matter (DOM) with high aromaticity and abundant humic-like component was an important precursor for CO photoproduction. Under the high-emission scenario, warming is projected to significantly enhance CO photoproduction rate by ∼15% in the terrestrial-influenced regions of the YS and ECS by 2100. In contrast, its effect is projected to be insignificant (an increase of ∼8%) in the oligotrophic SCS and EIO. Moreover, neither a pH reduction of 0.2 or 0.4 units nor deoxygenation are expected to have significant influence on CO photoproduction rate in the study areas. CO photoproduction increases with increasing nitrate concentration, which is attributed to hydroxyl radicals (•OH) produced by nitrate photolysis. The •OH generated by natural seawater photolysis in the investigated areas induced about 10%–23% of CO photoproduction.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104607"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034499","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":"Characterizing organic carbon source, age, and degradation state in Northern Patagonia fjord surface sediments","authors":"Emily G. Watts ,&nbsp;Iván Pérez-Santos ,&nbsp;Jack A. Hutchings ,&nbsp;Derrick R. Vaughn ,&nbsp;Peter A. Raymond ,&nbsp;Andrew R. Zimmerman ,&nbsp;Zhanfei Liu ,&nbsp;Guido Mancilla-Gutiérrez ,&nbsp;Thomas S. Bianchi","doi":"10.1016/j.marchem.2026.104605","DOIUrl":"10.1016/j.marchem.2026.104605","url":null,"abstract":"<div><div>Fjords are a globally significant carbon sink with the highest burial rates of organic carbon (OC) per unit area of all marine depositional systems. As many fjords face the impacts of global change, understanding carbon cycling in these estuaries is crucial. We estimated OC sources and degradation state in Northern Patagonia (41°S to 47°S) fjord sediments using radiocarbon, stable isotopes, and chemical biomarkers. Surface sediment OC content ranged from 0.15 to 5.34%. Majority of this OC was modern, although there was a widespread but low petrogenic OC (OC_petro) content of 0.13, 95% confidence interval [0.08–0.18%]. This OC_petro can be the dominant and even sole source of OC to Northern Patagonia sediments in regions with low overall OC contents. There were steep gradients of modern terrestrial OC (OC_terr) contributions moving from fjords (∼70%) to broader bays and channels (∼6%), indicating these fjords act as OC_terr sinks. There was an apparent decoupling of OC_terr and marine OC (OC_mar) degradation in sediments, reflected by lignin and amino acid biomarkers. This decoupling likely results from the preferential association of OC_mar with minerals, illustrated by high OC_mar to surface area ratios (OC/SA; 0.38 mg C m⁻²) compared to terrestrial OC/SA (0.13 mg C m⁻²), a continuous supply of OC_mar compared to point source inputs of OC_terr, as well as the greater sensitivity of OC_mar to aerobic degradation. Overall, the Northern Patagonia fjord system is a sink of OC_terr, and OC cycling within these fjords will continue to evolve with anthropogenic global change.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104605"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077532","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":"The internal consistency between calculated and measured variables of the marine carbonate system in Arctic open and coastal waters, case study: Atlantic Arctic","authors":"Fernando Aguado Gonzalo,&nbsp;Katarzyna Koziorowska,&nbsp;Beata Szymczycha,&nbsp;Karol Kuliński","doi":"10.1016/j.marchem.2026.104604","DOIUrl":"10.1016/j.marchem.2026.104604","url":null,"abstract":"<div><div>The Arctic Ocean plays a crucial role in anthropogenic carbon sequestration, while also being among the regions most susceptible to Ocean Acidification (OA). To understand, quantify, and monitor the rapid biogeochemical changes in the Arctic shelves and coastal waters, it is necessary to accurately determine the complete marine carbonate system. However, the uncertainty range in the calculated values is still unclear, fogging our ability to properly estimate carbon inventory and OA. In this study, we collected samples in the Arctic open and coastal waters to estimate the internal consistency of total alkalinity (TA), pH, partial pressure of CO₂ (pCO₂) and dissolved inorganic carbon (DIC) when only two of them are measured and the other two calculated. In open ocean waters, calculated values generally show good consistency with observations, whereas in coastal areas, it was only possible to accurately calculate two variables: 1) pH using as input parameters pCO₂ together with either TA or DIC, and 2) pCO₂ using DIC and pH. Furthermore, we found that, in this dataset, using the TA estimated from its correlation with salinity together with pCO₂ also allowed obtaining accurate pH values in both coastal and ocean waters. This opens a new possibility of monitoring changes in the carbon cycle by measuring only salinity and pCO₂ in areas where its consistency has been evaluated. Finally, in this study, we provide guidelines for obtaining and reporting good-quality carbonate system data in Arctic coastal areas.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104604"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976560","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":"Determination of 14C concentration in coastal seawater of the Korean Peninsula using accelerator mass spectrometry","authors":"Min-Seok Oh ,&nbsp;Gwan-Ho Lee ,&nbsp;Weon Cheol Lim,&nbsp;Byung-Yong Yu","doi":"10.1016/j.marchem.2025.104602","DOIUrl":"10.1016/j.marchem.2025.104602","url":null,"abstract":"<div><div>Radiocarbon (¹⁴C) in seawater is a key tracer for investigating carbon cycling and air–sea exchange. This study quantified ¹⁴C concentrations in coastal seawater from 18 sites around the Korean Peninsula using accelerator mass spectrometry (AMS). A CO₂ extraction system optimized for 100 mL seawater samples was developed, achieving 85.5 ± 0.9 % recovery efficiency validated by certified reference materials. AMS results showed fraction modern carbon (fMC) values between 0.98 and 1.03, reflecting equilibrium with atmospheric ¹⁴CO₂. The East Sea exhibited relatively high fMC and Δ¹⁴C, likely due to open-ocean circulation. The West and South Seas showed lower fMC and negative Δ¹⁴C values, influenced by restricted mixing and terrestrial inputs. Average ¹⁴C concentrations were 4.99 × 10⁻³ Bq/L (East Sea), 5.22 × 10⁻³ Bq/L (West Sea), and 4.84 × 10⁻³ Bq/L (South Sea). These findings provide a regional baseline for coastal ¹⁴C and highlight the need for depth-resolved studies to better understand carbon dynamics.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104602"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925686","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":"Evidence for weathering of silicate minerals in ocean columns as the primary source of oceanic alkalinity","authors":"Tasuku Akagi,&nbsp;Hirotaka Nishino","doi":"10.1016/j.marchem.2025.104603","DOIUrl":"10.1016/j.marchem.2025.104603","url":null,"abstract":"<div><div>Based on the correlated increase of alkalinity (At) with that of silicic acid concentration [Si] in the Atlantic Ocean, the contemporaneous dissolution of carbonates and opal in the water column has been proposed as the mechanism for alkalinity production. We revisited existing datasets to examine, in greater detail, the relationship between oceanic At, [Si], total dissolved inorganic carbon (TIC) and its carbon stable isotope ratios (δ¹³C), to examine which of the two possible alkalinity sources, carbonate dissolution or silicate mineral weathering, is the most probable source of alkalinity.</div><div>We invariably find that At and [Si] are correlated and the slope ΔAt/ΔSi is almost identical for the intermediate water (2 &lt; potential temperature, <em>θ</em> &lt; 8 °C) of Atlantic, Indian and Pacific oceans. The At and [Si] correlation is difficult to explain by carbonate + opal dissolution, since the carbonate and biogenic opal production rates differ widely among the ocean basins.</div><div>We investigated the carbon sources from δ¹³C measurement of total dissolved inorganic carbon (TIC) in the intermediate water (2 &lt; <em>θ</em> &lt; 8 °C) and in the deeper water (<em>θ</em> &lt; 2 °C), separately. Waters characterized by the same pH are used in the investigation, since the δ¹³C of TIC generated during carbonate dissolution is constrained. In the intermediate water, the resulting data do not support the notion of carbonate dissolution as the alkalinity source, whereas in the deeper water both carbonate dissolution and silicate mineral weathering are shown as the producers of alkalinity. Carbonate dissolution only acts to relocate surface alkalinity to the deep water. We infer that dissolution of terrigenous silicate minerals within the oceans (a process we refer to as “ocean silicate weathering”) is the primary source of alkalinity in the oceans. This interpretation also explains the linear relationship between At and [Si] in the water.</div><div>Our findings do not contradict the conventional understanding of oceanic silicon cycles, if biogenic opal contains weatherable siliceous material. We previously showed that such matter is present in diatom frustules. Its uptake by fauna in deep water may provide a compelling explanation for the coupling of increases in [Si] and At. It is shown that ocean silicate weathering is a key to understanding the mechanism of CO₂ absorption by the ocean.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104603"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925687","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":"Phosphorus speciation and C:N:P stoichiometry in particles in the East Sea (Japan Sea), Northwest Pacific","authors":"Chihyun Oh,&nbsp;Taehee Na,&nbsp;Jeomshik Hwang","doi":"10.1016/j.marchem.2025.104601","DOIUrl":"10.1016/j.marchem.2025.104601","url":null,"abstract":"<div><div>Particulate phosphorus (P) can exist in several species, particularly in marginal seas, where sediment resuspension can affect particle fluxes. The effect of P speciation on the C:N:P stoichiometry of particulate organic matter is poorly constrained. We investigated the C:N:P stoichiometry in the East Sea (Japan Sea), which is a marginal sea in the Northwest Pacific, by analyzing sinking particles collected at water depths of 500, 1000, and 2250 m (i.e., 50 m above the seafloor), along with suspended particles in the surface waters and the underlying sediments. We measured particulate organic carbon (POC), particulate nitrogen (PN), and particulate P. The P was separated into total P (TP), organic P (OP), inorganic P (IP), non-apatite inorganic P (NAIP), and apatite P (AP) following the Standards, Measurements, and Testing (SMT) protocol of the European Commission. In addition, Al, Si, and Ca were analyzed to estimate the contents of lithogenic material, opal, and CaCO₃ in the sinking particles. The POC:PN ratio increased from 8.2 at 500 m water depth to 8.9 in the surface sediment, whereas the POC:TP and PN:TP ratios decreased from 229 and 28 at 500 m to 68 and 7.6 in the surface sediment, respectively. The IP flux exhibited a strong positive correlation with the Al flux (R² = 0.92), which is a proxy for material derived by sediment resuspension. After correction based on the content of Al, to eliminate the contribution from sediment resuspension, nearly all of the IP was accounted for by the resuspension-derived fraction, implying that sediment resuspension could be the dominant source of IP in sinking particles in a marginal sea environment. The mean biogenic (i.e., resuspension-corrected) C:N:P ratios were 238:36:1 in suspended particles in the surface water, 444:56:1, 359:45:1, 329:37:1 in sinking particles at water depths of 500, 1000, and 2250 m, respectively, and 109:12:1 in the surface sediment. The biogenic C:N:P stoichiometry suggests that surface IP is labile and subject to rapid recycling in the upper 500 m of the sea. We suggest that C:TP is an appropriate measure of the stoichiometry of biogenic particles in the upper layer, whereas C:OP is more appropriate for sinking particles affected by resuspension in the deeper interior of the sea.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104601"},"PeriodicalIF":2.5,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840237","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 new sub-routine for the molecular component of the mixed-kinetics dissolution model of CaCO3 in seawater-like solutions","authors":"Victor W. Truesdale ,&nbsp;Jim Greenwood ,&nbsp;Tim Southern","doi":"10.1016/j.marchem.2025.104599","DOIUrl":"10.1016/j.marchem.2025.104599","url":null,"abstract":"<div><div>As a prelude to further understanding the dissolution kinetics of CaCO₃ in the oceanic water-column, the principles of Chemical Kinetics are applied generally to what recently was defined as the <em>solution-oriented approach</em> to CaCO₃ dissolution kinetics. The ultimate objective of the study is to probe what is known commonly as, the ‘mixed-kinetics model’ for dissolution; a sequence of molecular and diffusion reactions derived, historically, from the use of the spinning-disc reactor. As a first step, the paper shows how carbonate chemistry can be introduced into the molecular component, to generate the ions that subsequently diffuse across the hydrodynamic boundary layer surrounding the solid, into the bulk solution. The intention is to discover how control of the whole reaction shifts between molecular and diffusion components with change in stirring conditions, as that condition is a significant barrier to linking laboratory and field studies. In the interim, however, the study presents four archetypal, [Ca²⁺] versus time plots (geometric templates) that cover reactors either open or closed to CO₂, and in which pH is either fixed or variable. These plots provide a better alternative to the more common one of rate versus reaction extent, Ω, favoured in oceanography, but which has proved to be unsatisfactory. In turn, these new templates are compared with existing standard kinetics curves, for example, one from the analytic solution for a non-hydrolysing AB-salt, e.g., gypsum.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104599"},"PeriodicalIF":2.5,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840236","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}