Marine Chemistry最新文献_第2页

Effects of mineral inputs on organic phosphorus (Adenosine 5′-monophosphate) sorption and implications for its biogeochemical behavior on marine sediments 矿物输入对海洋沉积物有机磷（5′-单磷酸腺苷）吸附的影响及其生物地球化学行为的意义

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-12-16 DOI: 10.1016/j.marchem.2025.104600

Yu Meng , Meng Lv , Xiao-Tong Zhang , Xiao-Yan Cao , Rong Chen , Gui-Peng Yang

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.

沿海地区矿物颗粒的径流输入影响着养分的迁移和转化。海岸带富营养化引起了人们对有机磷的关注，而矿物输入对有机磷迁移的影响尚不清楚。本研究研究了OP化合物（腺苷5′-单磷酸腺苷，AMP）在针铁矿、高岭土和两种矿物与天然沉积物的混合物上的吸附行为。傅里叶变换红外光谱（FTIR）和表面酸碱特征揭示了混合物中存在的相互作用。采用间歇法进行了吸附动力学和热力学实验。动力学数据用两室一阶方程描述，吸附等温线用Freundlich和Langmuir模型都能很好地拟合。针铁矿的吸附能力高于高岭土，且对盐度的吸附更为敏感。添加矿物的沉积物的吸附量明显低于预期，特别是与高岭土混合的沉积物的吸附量下降了57.4%。吸附过程中OP组分的分析表明，交换性或松散吸附的有机磷（Ex-Po）和铁/铝结合的有机磷（NaOH-Po）明显增加，以NaOH-Po为主。针铁矿和高岭土中作为生物可利用OP的Ex-Po和NaOH-Po的总和约为总吸附量的一半。与原始的离散型相比，添加矿物后沉积物中的Ex-Po增加，NaOH-Po减少，表明矿物与沉积物基质之间的相互作用降低了其保留AMP的能力。这些发现突出了矿物-沉积物相互作用在改变OP吸附特征中的重要作用，对其生物地球化学命运具有重要意义。

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引用次数: 0

Analysis of nutrient and hydrographic patterns on the GEOTRACES Pacific Meridional Section (GP15) using PYOMPA, a new framework for water mass analysis 利用新的水体质量分析框架PYOMPA分析GEOTRACES太平洋经向剖面（GP15）的营养和水文格局

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-12-12 DOI: 10.1016/j.marchem.2025.104598

R.M. Lawrence , A. Shrikumar , E. Le Roy , J. Swift , P.J. Lam , G.A. Cutter , K.L. Casciotti

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.

GEOTRACES GP15太平洋经向样带在56°N和20°S之间的太平洋中部取样了几个生物地球化学省。该样带旨在研究太平洋地区营养物质、微量元素和同位素（TEIs）分布的过程，包括它们的输入、损失和内部循环。在这项研究中，我们报告了GP15的营养物质（硝酸盐、亚硝酸盐、磷酸盐、硅酸盐）、水文（温度、盐度）和氧气数据，并使用改进的最佳多参数分析（PYOMPA）量化了水质量混合如何影响它们沿GP15的分布。通过对水质量分布施加“软”惩罚，并使用原型分析来定义端元属性，PYOMPA的结果不仅符合预期，而且产生了更低的残差，使我们能够更有信心地量化区域边界的水质量贡献。在PYOMPA中使用灵活的再生化学计量学也突出了区域再生和生物地球化学循环对GP15沿线养分分布的影响。这一分析有助于更好地理解太平洋中部的营养物质运输和再生模式，它抓住了经向翻转环流的关键特征。

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引用次数: 0

Riverine turbidity overrides nutrient enrichment in regulating coastal volatile sulfur compounds cycling 在调节沿海挥发性硫化合物循环方面，河流浊度超过了营养物质的富集

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-12-01 DOI: 10.1016/j.marchem.2025.104586

Qian-Yao Ma , Jun-Qi Yang , Meng-Yan Yu , Jiao-jiao Pang , Gui-Peng Yang

Volatile sulfur compounds (VSCs), including dimethyl sulfide (DMS), carbonyl sulfide (COS), and carbon disulfide (CS₂), play key roles in atmospheric chemistry and climate regulation. Riverine discharge supplies nutrients and chromophoric dissolved organic matter (CDOM) that can potentially stimulate the production of VSCs. Yet, field observations in many estuarine regions have revealed surprisingly low VSCs levels, implying that riverine enrichment alone cannot explain their variability. In this study, concentrations of DMS, COS, and CS₂ were quantified in surface waters, vertical profiles, and the overlying atmosphere of the Bohai and Yellow Seas during spring and summer 2024. Average surface concentrations of DMS, COS, and CS₂ were 6.3, 0.11, and 0.09 nmol L⁻¹ in spring, increasing to 9.7, 0.35, and 0.19 nmol L⁻¹ in summer. DMS showed strong positive correlation with chlorophyll-a, while COS correlated with CDOM. Riverine inputs of nutrients and CDOM from the Yellow River enhanced VSCs production, although elevated turbidity limited light availability and thus suppressed biological and photochemical pathways. Atmospheric mixing ratios in spring averaged 61.1, 408.7, and 105.5 pptv for DMS, COS, and CS₂, respectively. The estimated sea-to-air flux demonstrated that DMS was the dominant contributor to atmospheric sulfur in the study region, with fluxes of 5.4 μmol m⁻² d⁻¹ in spring and increasing to 15.0 μmol m⁻² d⁻¹ in summer. These results highlight the vital role of riverine discharge in modulating both nutrient supply and turbidity, thereby regulating the biological and photochemical pathways that control VSCs production and their subsequent sea-to-air emissions in coastal waters.

挥发性硫化合物（VSCs），包括二甲硫醚（DMS）、羰基硫醚（COS）和二硫化碳（CS2），在大气化学和气候调节中起着关键作用。河流排放提供营养物质和显色性溶解有机物（CDOM），可以潜在地刺激VSCs的产生。然而，在许多河口地区的实地观察显示，VSCs水平出奇地低，这意味着仅靠河流富集不能解释它们的变化。本文对2024年春夏渤海、黄海地表水、垂直剖面和上覆大气中DMS、COS和CS2的浓度进行了定量分析。DMS、COS和CS2的平均表面浓度春季分别为6.3、0.11和0.09 nmol L−1，夏季分别为9.7、0.35和0.19 nmol L−1。DMS与叶绿素-a呈显著正相关，COS与CDOM呈显著正相关。来自黄河的营养物质和CDOM的河流输入促进了VSCs的产生，尽管浊度升高限制了光的可用性，从而抑制了生物和光化学途径。DMS、COS和CS2春季大气混合比平均分别为61.1、408.7和105.5 pptv。估算的海气通量表明，DMS是研究区大气硫的主要贡献者，春季通量为5.4 μmol m−2 d−1，夏季增加到15.0 μmol m−2 d−1。这些结果强调了河流排放在调节营养供应和浊度方面的重要作用，从而调节控制VSCs生产及其随后在沿海水域向海洋空气排放的生物和光化学途径。

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引用次数: 0

Methane dynamics in the southeastern Arabian Sea: Patterns of distribution and annual emission estimates 阿拉伯海东南部的甲烷动态：分布模式和年排放估算

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-12-01 DOI: 10.1016/j.marchem.2025.104588

K.S. Arya , T.R. Gireeshkumar , Mary Sandra D'cunha , Mohammad Nishad T , K.R. Muraleedharan , V.B. Adarsh , Anjana Jayaprakash

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-a and turbidity during the SWM, indicating anaerobic methanogenesis via 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 (<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.

阿拉伯海东南部与气候相关的微量气体，包括甲烷（CH4）的产生途径和海气通量，由于其空间和季节异质性，尚未得到充分解决，并且存在很大的不确定性。为了了解CH4在西南和东北季风季节的分布和海气通量，我们对沿南海的5个沿海-海洋样带进行了测量。CH4浓度在SWM为3 ~ 151 nM(13±16 nM)， NEM为1 ~ 140 nM(16±38 nM)，呈梯度递减趋势，表明淡水流入和分层是控制CH4分布的关键过程。在SWM过程中，CH4浓度与叶绿素-a和浊度呈正相关，表明厌氧甲烷是通过微生态位发生的。尽管全球缺氧带被认为是CH4的重要来源，但在缺氧条件下，SEAS的CH4水平相对较低，可能是由于沉积物中的有机碳含量较低（< 5%）。海洋对空气CH4通量的范围为0.1 ~ 278 μM−2 day−1，海洋CH4年排放量的估计值（~ 0.006 Tg yr−1）与以前的估计值一致。SWM和NEM期间的全球变暖潜势分别为0.21±0.45和0.6±1.7 g CO2 eq m−2 day−1，年净排放量为0.18 Tg CO2 yr−1。本研究强调了SEAS作为CH4释放热点的重要性，强调海洋环境中与气候相关的痕量气体的精确和高分辨率测量对于改善未来气候预测、全球温室气体预算以及制定缓解战略以实现未来气候目标至关重要。

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引用次数: 0

Native S from seafloor hydrothermal sites: Messenger for magmatic degassing of metals into submarine hydrothermal systems 来自海底热液点的原生S：金属岩浆脱气进入海底热液系统的信使

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-12-01 DOI: 10.1016/j.marchem.2025.104585

Vesselin Dekov , Bleuenn Guéguen , Toshiro Yamanaka , Andrea Koschinsky , Sven Petersen , Sophie A.L. Paul , Charlotte Kleint , Wolfgang Bach , Gert J. de Lange

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 < δ³⁴S_{terrestrial mantle sulfide}) or synproportionation of magmatic SO₂ and H₂S (δ³⁴S_sample > 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 < 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.

在海底热液区，原生硫以小烟囱、海底火山口湖、沉积物上的污渍和结壳的形式沉淀，并以裂缝和囊泡的形式充填在岩石中。与缺氧和富氧海底环境下的生物成因原生硫不同，海底热液原生硫是岩浆SO2 （δ34Ssample <； δ 34地幔硫化物）的不成比例作用或岩浆SO2与H2S （δ34Ssample >； δ 34地幔硫化物）的共比例作用的结果。将其作为岩浆挥发通量的代表，发现其携带Zn （δ66Znsample <； δ66Znbulk硅酸盐土）岩浆脱气的同位素信号。因此，海底热液原生S0为金属对海底热液系统的直接岩浆贡献提供了新的同位素证据，并可能是海洋中岩浆挥发性金属排放的信使。

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引用次数: 0

Copper speciation and its relationship with dissolved organic matter in a hypersaline coastal lagoon 高盐沿海泻湖中铜的形态及其与溶解有机质的关系

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-12-01 DOI: 10.1016/j.marchem.2025.104581

Maria Sol Hernández-Conesa , Juan Santos-Echeandía , Patricia Bernárdez , Xosé Antón Álvarez-Salgado , Mar Nieto-Cid , Paula Sánchez-Marín

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 (

{\log K ´}_{{Cu}^{2 +}}

) 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.

Mar Menor（伊比利亚半岛东南部）是欧洲最大的高盐沿海泻湖。这一生态系统受到人为影响的严重影响，导致金属和其他污染物进入。众所周知，总金属浓度不能很好地预测其生物利用度，应考虑其化学形态。铜（Cu）是一种环境关注的金属，其形态主要受天然有机配体的控制。本工作旨在研究泻湖中溶解铜的化学形态及其与溶解有机质（DOM）的关系。为此，在2021年和2022年的六次环境调查中，在泻湖的不同地点采集了36个水样。以水杨醛肟为竞争配体，采用阴极溶出伏安法（cl - adcsv）研究了溶解铜的化学形态。通过元素组成（C和N）和光学性质（荧光和吸光度）对同一样品中的DOM进行了表征。溶解铜的形态可以用单配体模型来解释，配体浓度（LCu）在15.89 ~ 90.82 nM之间；条件稳定常数（logK´Cu2+）在11.36和12.92之间变化。LCu与溶解有机碳（DOC）浓度、254 nm吸收、类腐殖质荧光强度呈正相关，表明腐殖质材料是控制该地区Cu形态形成的主要配体。此外，doc归一化后的LCu与芳香性指数SUVA254呈显著正相关，说明DOM芳香性可以很好地反映腐植质DOM的金属结合能力。尽管Mar Menor的DOC浓度非常高，但Cu络合与其他DOC较低的沿海地区相似，这可能是由于泻湖的高盐性质造成的。

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引用次数: 0

Dynamics of nutrients and organic matter and their control mechanisms at the river mouths of major Chinese rivers 中国主要河流河口养分和有机质动态及其调控机制

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-11-30 DOI: 10.1016/j.marchem.2025.104587

Xintong Jiang , Mengyu Wang , Yue Ming , Ailin Yao , Xianye Wang , Lei Gao

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.

高强度的人类活动对全球主要河流向海洋输出的营养物和有机物的通量和组成产生了强烈影响。本研究的目的是确定控制中国8条主要河流向海洋输送的陆地营养物质和有机质分布和变化的机制。江河流域水库和水坝的不断建设，使其具有水库的特征，河道破碎化加剧，水体透明度提高，保水时间延长，营养物质滞留时间延长，浮游植物生物量和产量增加。本文给出了“水库程度”（即河道类似水库或湖泊的程度）的初步定义，并提供了一个经验方程来粗略量化河流的水库程度。在中国8条主要河流的河口采集了不同季节的地表水样本，并测量了这些样本中营养物质和有机物的浓度和组成。旋转主成分分析表明，水库程度和污染程度是决定这些河流中养分和有机质分布和变化的最重要因素。我们发现，小河流的水库度往往高于大河，平原河流高于山地河流。由于八个流域的水库和水坝仍在建设中，河流的水库度将继续增加。但随着环保工程的实施，污染程度有所降低。因此，不同生物地球化学参数在未来将呈现出不同的变化趋势。该研究结果有助于阐明全球河流输送养分和有机质的控制机制和未来演变趋势。

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引用次数: 0

Resilience of pH to seasonal change in a large subtropical lagoonal estuary 亚热带大型泻湖河口pH值对季节变化的恢复力

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-11-24 DOI: 10.1016/j.marchem.2025.104577

Paco Quintana , Eunice Machado , Rodrigo Kerr

Coastal ecosystems exhibit a wide range of pH trends, from −0.023 to 0.023 pH units yr⁻¹, making them particularly susceptible to acidification or basification. These variations are primarily driven by ecosystem metabolism and the influence of oceanic and riverine endmembers, as observed in the subtropical system of the Patos Lagoon Estuary (PLE, southern Brazil), where biogeochemical variability is largely governed by mixing of water masses with different properties. This study provides the first quantification of the seasonal variability of pH buffering capacity in the inner and outer zones of PLE. From May 2017 to September 2023, we assessed temporal variability using multiple approaches: (i) carbonate system parameters, (ii) sensitivity factors, (iii) buffering capacity of pH to fractional change of dissolved inorganic carbon (βDIC), (iv) metabolic effects on pH, and (v) environmental drivers of pH. The results revealed a distinct seasonal pH pattern, especially between summer with winter and spring, with consistently higher values at the outer station compared to the inner station, though spatial differences were not statistically significant. In winter and particularly in early spring, calcium carbonate (CaCO₃) dissolution prevailed due to riverine input characterized by low buffering capacity. Along the salinity gradient, pH exhibited a pronounced difference, particularly between low and high salinity conditions. However, the persistent negative deviation of the metabolic effect on pH throughout the year and in salinity ranges, even under seawater conditions, supports the characterization of this coastal ecosystem as a net CO₂ source, with especially high variability at mid-salinity conditions. Although the salinity gradient was comparable between stations, they exhibited differences in the magnitude of pH sensitivity to seasonal biogeochemical changes. These findings indicate that PLE functions as a system with moderate to low buffering capacity, with the outer zone showing greater resilience to pH fluctuations.

沿海生态系统的pH值变化范围很广，从- 0.023到0.023 pH单位/年，这使它们特别容易受到酸化或碱化的影响。这些变化主要是由生态系统代谢以及海洋和河流末端成员的影响驱动的，正如在巴西南部帕托斯泻湖河口（PLE）的亚热带系统中所观察到的那样，那里的生物地球化学变异在很大程度上是由不同性质的水团混合控制的。该研究首次量化了PLE内外带pH缓冲能力的季节变化。从2017年5月到2023年9月，我们使用多种方法评估了时间变异：(1)碳酸盐体系参数，(2)敏感性因子，(3)pH对溶解无机碳分数变化的缓冲能力，(4)代谢对pH的影响，以及(5)pH的环境驱动因素。结果表明，pH值具有明显的季节变化规律，特别是夏季与冬季和春季之间，尽管空间差异不显著，但外站的pH值始终高于内站。在冬季，特别是初春，由于河流输入的缓冲能力较低，碳酸钙（CaCO3）溶解占主导地位。在盐度梯度上，pH值表现出明显的差异，特别是在低盐度和高盐度条件下。然而，即使在海水条件下，全年和盐度范围内代谢对pH值的持续负偏差也支持了这一沿海生态系统作为二氧化碳净源的特征，在中等盐度条件下具有特别高的变异性。虽然盐度梯度在站点之间具有可比性，但它们对季节性生物地球化学变化的pH敏感性程度存在差异。这些发现表明，PLE作为一个具有中等到低缓冲能力的系统，其外部区域对pH波动表现出更大的弹性。

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引用次数: 0

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 沙漠尘埃输入和明显的最低氧区是溶解钼和铀的源还是汇？东大西洋的GEOTRACES研究

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-11-20 DOI: 10.1016/j.marchem.2025.104580

Sandra Poehle, Imelda B. Velasquez , Andrea Koschinsky

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.

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.

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.

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.

钼（Mo）和铀(U)通常被认为是海洋水柱中的保守金属，尽管在地表水中观察到偏差。主要目的是研究沙尘输入和明显的氧最小带（OMZs）对溶解Mo和U的影响，并与两个GEOTRACES研究巡航（受撒哈拉沙尘和毛里塔尼亚上升流影响的GA11 - NE-Atlantic和受纳米比亚沙尘和本格拉上升流影响的GA08 - SE-Atlantic）的海水样品中的真正保守元素铷（Rb）进行比较。我们观察到，在撒哈拉沙尘羽流轨迹（NE-Atlantic）下，Mo和U的浓度分别为114.8 nmol/kg和14.5 nmol/kg，略高于其平均海水浓度（107 nmol/kg和13.9 nmol/kg），从而假设撒哈拉沙尘是一个来源。在缺氧的纳米比亚大陆架（SE-Atlantic）上方，Mo和U的浓度分别为102.8 nmol/kg和11.9 nmol/kg，略低于平均水平，这可能是由于小于0.015 μm的Mo和U的还原固体形成。沉积物释放的有机物和胶体U之间的联系需要更多的研究。相比之下，Rb浓度随深度保持不变，不受东北大西洋和东南大西洋区域影响，约为。1.3 μmol/kg表现出真正的保守性。我们的研究表明，由于气候变化等原因，低氧水的扩张可能会向低氧条件转变，并在未来发生更广泛的沙尘事件，这可能会影响Mo和U的分布和潜在的同位素特征。

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引用次数: 0

Cobalt mobility in high-energy beach sediments – a view on the redox cascade of trace metals combining in-situ observations and flow-through experiments 高能海滩沉积物中的钴流动性-结合原位观察和流动实验对痕量金属氧化还原级联的看法

IF 2.5 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry

Pub Date : 2025-11-18 DOI: 10.1016/j.marchem.2025.104583

Anja Reckhardt , Magali Roberts , Felix Auer , Moritz Holtappels , Rena Meyer , Michael Ernst Böttcher , Katharina Pahnke

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.

潮间带砂质高能滩地下河口是复杂动态的生物地球化学反应器。我们的研究目的是评估痕量金属的流动性，特别关注钴（Co），沿着氧化还原和盐度梯度在Spiekeroog岛（德国）的高能量海滩的浅层到深层STE。Co是浮游植物生长的微量营养元素，表征其在这些系统中的转化行为有助于全面了解沿海Co循环。在2022年至2024年期间，每6周对24米以下的地下水进行采样，以获得STE生物地球化学的高时空分辨率横断面视图。从岩心中收集的沉积物用于确定痕量金属循环的沉积基础。地下水Co浓度表现出特定的动员层，这主要与锰（Mn）的早期还原带有关。铁（Fe）还原条件导致Co在固相中固定，可能是由于伴随轻微的净微生物硫酸盐（SO42−）还原和形成含Co的Fe硫化物或Co硫化物（CoS）。固相分析表明，在前潮滩沉积层中，Fe、Mn和Co的活性动员潜力最高，该沉积层目前被约5米的海滩砂覆盖，并被更新世冰川-河流沉积物所覆盖。与铀(U)、钼（Mo）和铼（Re）的氧化还原相关反应性相比，在原位条件下观察到的Co的移动和固定行为在实验室流动实验中得到了再现，表明Co在氧化还原到Fe和潜在的轻微SO42 -还原条件下沿氧化还原梯度的高释放和去除率。关于海岸元素循环，高能海滩STEs可能有利于Co的动员，因为高电子受体供应导致较少的还原条件和空间扩展的中间氧化还原水平。此外，与扩散为主的系统相比，平流地下水可能会增加Fe、Mn和Co等元素的排放，扩散为主的系统更有可能受到再氧化过程的限制。

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引用次数: 0