Marine Chemistry最新文献

{"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":"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":"Analysis of nutrient and hydrographic patterns on the GEOTRACES Pacific Meridional Section (GP15) using PYOMPA, a new framework for water mass analysis","authors":"R.M. Lawrence ,&nbsp;A. Shrikumar ,&nbsp;E. Le Roy ,&nbsp;J. Swift ,&nbsp;P.J. Lam ,&nbsp;G.A. Cutter ,&nbsp;K.L. Casciotti","doi":"10.1016/j.marchem.2025.104598","DOIUrl":"10.1016/j.marchem.2025.104598","url":null,"abstract":"<div><div>The GEOTRACES GP15 Pacific Meridional Transect sampled several biogeochemical provinces in the central Pacific Ocean between 56°N and 20°S. This transect was designed to study processes driving the distributions of nutrients, trace elements, and isotopes (TEIs) in the Pacific, including their inputs, losses, and internal cycling. In this study, we report the nutrients (nitrate, nitrite, phosphate, silicate), hydrography (temperature, salinity), and oxygen data for GP15 and quantify how water mass mixing underlies their distributions along GP15 using a modified Optimum Multiparameter Analysis (PYOMPA). By imposing ’soft’ penalties on water mass distributions and using archetype analysis to define endmember properties, results from PYOMPA not only aligned with expectations but yielded lower residuals and allowed us to quantify water mass contributions at regional boundaries with more confidence. The use of flexible regeneration stoichiometry in PYOMPA also highlighted the impacts of regional regeneration and biogeochemical cycling on nutrient distributions along GP15. This analysis informs a better understanding of nutrient transport and regeneration patterns in the central Pacific Ocean, which captures key features of the meridional overturning circulation.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104598"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797427","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":"Effects of mineral inputs on organic phosphorus (Adenosine 5′-monophosphate) sorption and implications for its biogeochemical behavior on marine sediments","authors":"Yu Meng ,&nbsp;Meng Lv ,&nbsp;Xiao-Tong Zhang ,&nbsp;Xiao-Yan Cao ,&nbsp;Rong Chen ,&nbsp;Gui-Peng Yang","doi":"10.1016/j.marchem.2025.104600","DOIUrl":"10.1016/j.marchem.2025.104600","url":null,"abstract":"<div><div>The runoff input of mineral particles in coastal areas affects the migration and transformation of nutrients. Organic phosphorus (OP) has attracted much attention due to coastal eutrophication, while the migration under the influence of mineral inputs has not been understood deeply. This study investigated the sorption behavior of an OP compound (Adenosine 5’-monophosphate, AMP) on goethite, kaolin, and two mixtures of the minerals with natural sediment. Fourier transform infrared spectroscopy (FTIR) spectra and surface acid-base characteristics revealed interactions presented within the mixtures. Sorption kinetics and thermodynamics experiments were carried out through batch methods. The kinetic data were described using a two-compartment first-order equation, and the sorption isotherms were well-fitted by both the Freundlich and Langmuir models. Goethite exhibited a higher sorption ability than kaolin, and the sorption was more sensitive to salinity. The sorption capacity of mineral-added sediments was significantly lower than predicted, particularly for sediments mixed with kaolin, which decreased by 57.4 %. The analysis of OP fractions during sorption revealed an obvious increase in exchangeable or loosely sorbed organic phosphorus (Ex-Po) and iron/aluminium-bound organic phosphorus (NaOH-Po), with NaOH-Po dominating. The sum of Ex-Po and NaOH-Po, as the bioavailable OP, in goethite and kaolin was estimated to be around half of the total sorption amount. Compared to the discrete original ones, the Ex-Po in the sediment with the mineral addition increased while NaOH-Po decreased after sorption, suggesting that the presence of interactions between the minerals and sediment matrix reduced their ability to retain AMP. These findings highlight the significant role of mineral-sediment interactions in altering OP sorption characteristics, with important implications for their biogeochemical fate.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104600"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840687","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":"Do desert dust input and pronounced oxygen minimum zones act as sources or sinks for dissolved molybdenum and uranium? A GEOTRACES study in the eastern Atlantic Ocean","authors":"Sandra Poehle,&nbsp;Imelda B. Velasquez ,&nbsp;Andrea Koschinsky","doi":"10.1016/j.marchem.2025.104580","DOIUrl":"10.1016/j.marchem.2025.104580","url":null,"abstract":"<div><div>Molybdenum (Mo) and uranium (U) are usually considered as conservative metals in the oceanic water column though deviations have been observed in e.g. surface waters. The key objective was to study the impact of dust input and pronounced oxygen minimum zones (OMZs) on dissolved Mo and U in comparison with the truly conservative element rubidium (Rb) in seawater samples from two GEOTRACES research cruises: GA11 - NE-Atlantic affected by Saharan dust and the Mauritanian upwelling and GA08 - SE-Atlantic affected by Namibian dust and the Benguela upwelling.</div><div>We observed slightly higher Mo and U concentrations, 114.8 nmol/kg and 14.5 nmol/kg, respectively, under the Saharan dust plume trajectory (NE-Atlantic) compared to their average seawater concentrations (107 nmol/kg and 13.9 nmol/kg) leading to the assumption of Saharan dust being a source. Slightly lower than average Mo and U concentrations, 102.8 nmol/kg and 11.9 nmol/kg, respectively, above the suboxic Namibian shelf (SE-Atlantic) can be attributed to the formation of reduced solid Mo and U smaller than 0.015 μm. A first hint to a link between sediment-released organic matter and colloidal U requires more research.</div><div>In contrast, Rb concentrations remained constant with depth, unaffected by regional influences in the NE and SE Atlantic, with approx. 1.3 μmol/kg showing truly conservative characteristics.</div><div>Our study implies that the expansion of less oxygenated waters with a potential shift towards euxinic conditions and more extensive dust events in the future due to e.g. climate change may affect the distribution and potentially isotopic signatures of Mo and U.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104580"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692281","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":"Methane dynamics in the southeastern Arabian Sea: Patterns of distribution and annual emission estimates","authors":"K.S. Arya ,&nbsp;T.R. Gireeshkumar ,&nbsp;Mary Sandra D'cunha ,&nbsp;Mohammad Nishad T ,&nbsp;K.R. Muraleedharan ,&nbsp;V.B. Adarsh ,&nbsp;Anjana Jayaprakash","doi":"10.1016/j.marchem.2025.104588","DOIUrl":"10.1016/j.marchem.2025.104588","url":null,"abstract":"<div><div>The production pathways and sea-to-air fluxes of climate-relevant trace gases, including methane (CH₄), in the southeastern Arabian Sea (SEAS), are poorly addressed and suffer significant uncertainties due to their spatial and seasonal heterogeneity. We measured CH₄ in five coastal-oceanic transects along the SEAS during the southwest (SWM) and northeast monsoon (NEM) seasons to understand the distribution and sea-to-air fluxes.CH₄ concentrations ranged from 3 to 151 nM (13 ± 16 nM) in SWM and from 1 to 140 nM (16 ± 38 nM) in NEM, decreasing in a gradient towards the offshore, which indicated that freshwater influx and stratification were key processes controlling the CH₄ distribution. CH₄ concentrations were positively correlated with chlorophyll-<em>a</em> and turbidity during the SWM, indicating anaerobic methanogenesis <em>via</em> micro-niches. Although globally hypoxic zones are considered a significant source of CH₄, the SEAS exhibited relatively low CH₄ levels under hypoxia, possibly due to the low organic carbon (&lt;5 %) in sediments. The sea-to-air CH₄ fluxes in the SEAS ranged from 0.1 to 278 μM m⁻² day⁻¹, and the estimated annual CH₄ emissions from the SEAS (∼0.006 Tg yr⁻¹) align with previous estimates. The global warming potential during SWM and NEM was 0.21 ± 0.45 and 0.6 ± 1.7 g CO₂ eq m⁻² day⁻¹, with net annual emissions of 0.18 Tg CO₂ yr⁻¹. The present study highlights the significance of SEAS's role as a hotspot for CH₄ release, emphasising that accurate and high-resolution measurements of climate-relevant trace gases from the marine environment are essential for improving future climate projections, global greenhouse gas budgets, and the development of mitigation strategies to achieve future climate goals.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104588"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692279","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":"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":"2026-01-01","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":"Dynamics of nutrients and organic matter and their control mechanisms at the river mouths of major Chinese rivers","authors":"Xintong Jiang ,&nbsp;Mengyu Wang ,&nbsp;Yue Ming ,&nbsp;Ailin Yao ,&nbsp;Xianye Wang ,&nbsp;Lei Gao","doi":"10.1016/j.marchem.2025.104587","DOIUrl":"10.1016/j.marchem.2025.104587","url":null,"abstract":"<div><div>The high-intensity human activities have had a strong impact on the flux and composition of nutrients and organic matter exported from major rivers to the sea worldwide. The goal of this study was to identify the mechanisms that control the distributions and variations of terrestrial nutrients and organic matter transported from the eight major Chinese rivers to the oceans. The continuous construction of reservoirs and dams in river basins causes them to resemble reservoirs, which results in intensified fragmentation of water channels, more transparent water bodies, longer water retention times, greater retention of nutrients, and enhanced biomass and production of phytoplankton. Herein we provide a preliminary definition of “reservoir degree” (i.e., the extent to which a river channel resembles a reservoir or a lake) and offer an empirical equation to roughly quantify the reservoir degree of rivers. We collected surface water samples at the river mouths of China's eight major rivers from different seasons and measured concentrations and compositions of nutrients and organic matter in these samples. Rotated principal component analysis of our data showed that reservoir degree and pollution degree are the two most important factors determining the distributions and variations of nutrients and organic matter in these rivers. We found that the reservoir degrees were often higher in small rivers than in large rivers and in plain rivers versus mountainous rivers. As reservoirs and dams are still being constructed in all the eight river basins, the reservoir degrees of the rivers will continue to increase. Under the implementation of environmental protection projects, however, their pollution degrees would decrease. Therefore, the different biogeochemical parameters will show divergent variation trends in the future. The results of this study help clarify the control mechanisms and the future evolution trends of nutrients and organic matter transported by rivers worldwide.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"274 ","pages":"Article 104587"},"PeriodicalIF":2.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692280","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}