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1.
Pierre Anschutz Thomas SmithAurélia Mouret Jonathan DebordeStéphane Bujan Dominique PoirierPascal Lecroart 《Estuarine, Coastal and Shelf Science》2009
Sandy sediments of continental shelves and most beaches are often thought of as geochemical deserts because they are usually poor in organic matter and other reactive substances. The present study focuses on analyses of dissolved biogenic compounds of surface seawater and pore waters of Aquitanian coastal beach sediments. To quantitatively assess the biogeochemical reactions, we collected pore waters at low tide on tidal cross-shore transects unaffected by freshwater inputs. We recorded temperature, salinity, oxygen saturation state, and nutrient concentrations. These parameters were compared to the values recorded in the seawater entering the interstitial environment during floods. Cross-shore topography and position of piezometric level at low tide were obtained from kinematics GPS records. Residence time of pore waters was estimated by a tracer approach, using dissolved silica concentration and kinetics estimate of quartz dissolution with seawater. Kinetics parameters were based on dissolved silica concentration monitoring during 20-day incubations of sediment with seawater. We found that seawater that entered the sediment during flood tides remained up to seven tidal cycles within the interstitial environment. Oxygen saturation of seawater was close to 100%, whereas it was as low as 80% in pore waters. Concentrations of dissolved nutrients were higher in pore waters than in seawater. These results suggest that aerobic respiration occurred in the sands. We propose that mineralised organic matter originated from planktonic material that infiltrated the sediment with water during flood tides. Therefore, the sandy tidal sediment of the Aquitanian coast is a biogeochemical reactor that promotes or accelerates remineralisation of coastal pelagic primary production. Mass balance calculations suggest that this single process supplies about 37 kmol of nitrate and 1.9 kmol of dissolved inorganic phosphorus (DIP) to the 250-km long Aquitanian coast during each semi-diurnal tidal cycle. It represents about 1.5% of nitrate and 5% of DIP supplied by the nearest estuary. 相似文献
2.
Joan D. Willey 《Marine Chemistry》1975,3(3):227-240
Dissolved alumina can coprecipitate with dissolved silica from seawater enriched with both compounds. This coprecipitation is almost complete within 1h and maintains the concentration of dissolved alumina near naturally occurring oceanic concentrations, well below the alumina concentration of 0.50 ppm A1 found to be stable in filtered Sargasso seawater at 2°C. Only 0.5 ppm Si is necessary to initiate this coprecipitation, which indicates that the concentrations of dissolved alumina that occur in seawater and in interstitial water are a function of the concentration of dissolved silica as well as of the alumina solubility.Dissolved alumina is also quickly removed by solid amorphous silica from solutions of seawater enriched in dissolved alumina and also by several marine sediments in contact with the solution. This process may be an important factor in authigenic mineral formation in marine sediments. 相似文献
3.
Joan D. Willey 《Marine Chemistry》1977,5(3):267-290
Dissolved silica can coprecipitate with zinc from seawater or distilled water that has been enriched with both elements. More than 2 ppm Si are necessary for the reaction to begin. The coprecipitation shows pH dependence. The addition of pulverized illite or natural sediment as suspended particulate material does not enhance the reaction in seawater. The organic material present in the nearshore seawater samples decreases the rate and extent of reaction, as indicated by comparisons of results of experiments using natural seawater with results obtained using UV-irradiated seawater. In unbuffered distilled water the reaction must compete with hydrolysis of zinc; however, reaction does occur, which indicates that the seawater matrix is not essential for the reaction. The coprecipitation can limit the concentration of zinc in seawater to less than the solubility concentration assumed for ZnCO3 or Zn(OH)2. The results suggest that a zinc silicate can precipitate directly from seawater or interstitial water as an authigenic mineral. 相似文献
4.
Joan D. Willey 《Marine Chemistry》1975,3(3):241-251
Amorphous silica can polymerize in distilled water, in 0.6 N NaCl solution and in seawater to form a colloidal suspension that contains approximately 200 ppm Si. Solid amorphous alumina can prevent this polymerization in seawater and in 0.6 N NaCl, and can inhibit but not prevent it in distilled water. This prevention of polymerization may be an important factor in authigenic mineral formation.The presence of solid amorphous alumina with solid silica in the same solutions causes the final concentrations of dissolved silica to be lower than those attained by solid silica in the absence of solid alumina. The effects are similar whether the final levels are approached from above or below the saturation concentration for amorphous silica. This indicates that the observed concentration of dissolved silica will be a function of available alumina as well as of the silica solubility.The presence of solid amorphous alumina with quartz in seawater, 0.6 N NaCl solution and distilled water causes dissolved silica levels to remain below 0.7 ppm Si for at least 38 days. The same systems in the absence of alumina approach the solubility levels of quartz within that time period. 相似文献
5.
The pore water concentrations of dissolved silica in sediment cores from the continental slope offshore from Cape Hatteras, North Carolina, varied from 150 to almost 700 μ,M with depth in the top 40 cm of sediment. Sediment cores from 630 to 2010 m depth had very similar profiles of dissolved silica in their pore waters, even though these cores came from regions greatly different in slope, topography, sedimentation rate, and abundance of benthic macrofauna. Cores from 474 to 525 m were more variable, both with respect to pore water dissolved silica profiles, and with respect to sediment texture. Experiments indicate that both the rate of dissolution of silica and the saturation concentration decrease as sediment depth below the sediment-seawater interface increases. These data are consistent with depletion of a reactive silica phase in surface sediment, which may be radiolarian tests, or the alteration of biogenic silica to a less reactive form over time. Experimental results suggest that the pore water dissolved silica concentration in sediments below the top few centimeters may be higher than the sediments could now achieve. The flux of dissolved silica out of these sediments is estimated to be 15 μmoles cm−2 yr−1. 相似文献
6.
Meagan Eagle Gonneea Paul J. Morris Henrieta Dulaiova Matthew A. Charette 《Marine Chemistry》2008,109(3-4):250
Over the past decade, radium isotopes have been frequently applied as tracers of submarine groundwater discharge (SGD). The unique radium signature of SGD is acquired within the subterranean estuary, a mixing zone between fresh groundwater and seawater in coastal aquifers, yet little is known about what controls Ra cycling in this system. The focus of this study was to examine controls on sediment and groundwater radium activities within permeable aquifer sands (Waquoit Bay, MA, USA) through a combination of field and laboratory studies. In the field, a series of sediment cores and corresponding groundwater profiles were collected for analysis of the four radium isotopes, as well as dissolved and sediment associated manganese, iron, and barium. We found that in addition to greater desorption at increasing salinity, radium was also closely tied to manganese and iron redox cycling within these sediments. A series of laboratory adsorption/desorption experiments helped elucidate the importance of 1) contact time between sediment and water, 2) salinity of water in contact with sediment, 3) redox conditions of water in contact with sediment, and 4) the chemical characteristics of sediment on radium adsorption/desorption. We found that these reactions are rapid (on the order of hours), desorption increases with increasing salinity and decreasing pH, and the presence of Fe and Mn (hydr)oxides on the sediment inhibit the release of radium. These sediments have a large capacity to sorb radium from fresh water. Combined with these experimental results, we present evidence from time series groundwater sampling that within this subterranean estuary there are cyclic periods of Ra accumulation and release controlled by changing salinity and redox conditions. 相似文献
7.
Although it is well-known that reactions occur within estuaries to alter the flux of dissolved aluminum from rivers into the oceans, the nature and relative importance of these reactions are not well defined. In this study we show that sediment-water interactions can have a significant influence on dissolved Al distributions in estuaries. Undisturbed sediments will act as a sink for dissolved Al because of diffusion across the sediment-water interface and reaction of Al within the sediment. Resuspension of sediments will cause a release of dissolved Al into relatively Si-depleted estuarine waters.Flocculation of colloidal material may cause a net consumption of dissolved Al in estuaries. Our results indicate, however, that this process may not, in many cases, be the primary cause for curvature in Al-Cl? profiles. An alternative model, whereby Al is displaced from organic matter complexes and adsorption sites in the estuarine zone and reacts with Si and cations in solution, is consistent with the data presented in this study as well as many other studies. In this case, the extent of net Al removal in estuaries will be determined by both the amount and nature of the dissolved organic matter present. 相似文献
8.
于2013年10~11月和2014年5~6月调查测定了东海陆架区海水中二甲亚砜(DMSO)的浓度,探讨了溶解态二甲亚砜(DMSOd)和颗粒态二甲亚砜(DMSOp)的水平和垂直分布、季节变化及其影响因素;此外,对沉积物间隙水中DMSOd的浓度以及表层海水中不同粒径的DMSOp和叶绿素a(Chl a)进行了分析。结果显示,秋季和夏初表层海水中DMSOd和DMSOp的平均浓度分别为(10.52±7.16)、(8.99±6.34)nmol·L^-1和(17.51±9.90)、(16.96±10.73)nmol·L^-1,存在明显的季节差异。秋季表层海水中DMSOp的高值区出现在Chl a较低的远岸海域,而夏初表层海水中DMSO的浓度从近岸到远海逐渐降低。间隙水中DMSOd的浓度明显高于底层海水中DMSOd的浓度,说明沉积物中存在DMSO的生产释放,可能是底层海水DMSO的重要来源。此外,粒径分布结果表明较大微型浮游植物(5~20μm)是秋季东海表层海水中DMSOp的主要贡献者。 相似文献
9.
《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(10):1829-1853
Concentrations of dissolved sulfate and sulfur isotopic ratios of dissolved sulfide in surface sediments of the Peru shelf and upper slope indicate that the sediments can be divided into two depth intervals based on the dominant biogeochemical reactions. Although rates of bacterial sulfate reduction are high throughout Peru surface sediments, chemistry of the upper interval (<10–20 cm) is dominated by chemoautotrophic oxidation of dissolved sulfide and elemental sulfur, while the lower interval (>10–20 cm) is dominated by dissimilatory sulfate reduction. In three of the four cores examined here, pore water concentrations of sulfate in the top 10 cm of the sediment are significantly higher than those of the overlying seawater. Peak sulfate concentrations in pore water (37–53 mmol/l) are ∼1.3–1.9 times that of seawater sulfate and are located 1–6 cm below the sediment/water interface (SWI). The excess sulfate is most likely produced by oxidation of elemental sulfur coupled to reduction of nitrate, a reaction mediated by a facultative chemoautotrophic sulfide-oxidizing bacterium, Thioploca spp. Numerical simulations demonstrate that the anomalously high concentrations of dissolved sulfate can be produced by steady-state or non-steady-state processes involving high rates of bacterial oxidation of elemental sulfur. If bacterial sulfur oxidation is a transient phenomenon, then it is probably triggered by seasonal or El Niño-induced changes in water-column chemistry of the Peru undercurrent. 相似文献
10.
Katharine R. Hendry Michael P. Meredith Christopher I. Measures Damien S. Carson Rosalind E.M. Rickaby 《Estuarine, Coastal and Shelf Science》2010
The use of dissolved Al as a tracer for oceanic water masses and atmospheric dust deposition of biologically important elements, such as iron, requires the quantitative assessment of its sources and sinks in seawater. Here, we address the relative importance of oceanic versus atmospheric inputs of Al, and the relationship with nutrient cycling, in a region of high biological productivity in coastal Antarctica. We investigate the concentrations of dissolved Al in seawater, sea ice, meteoric water and sediments collected from northern Marguerite Bay, off the West Antarctic Peninsula, from 2005 to 2006. Dissolved Al concentrations at 15 m water depth varied between 2 and 27 nM, showing a peak between two phytoplankton blooms. We find that, in this coastal setting, upwelling and incorporation of waters from below the surface mixed layer are responsible for this peak in dissolved Al as well as renewal of nutrients. This means that changes in the intensity and frequency of upwelling events may result in changes in biological production and carbon uptake. The waters below the mixed layer are most likely enriched in Al as a result of sea ice formation, either causing the injection of Al-rich brines or the resuspension of sediments and entrainment of pore fluids by brine cascades. Glacial, snow and sea ice melt contribute secondarily to the supply of Al to surface waters. Total particulate Al ranges from 93 to 2057 mg/g, and increases with meteoric water input towards the end of the summer, indicating glacial runoff is an important source of particulate Al. The (Al/Si)opal of sediment core top material is considerably higher than water column opal collected by sediment traps, indicative of a diagenetic overprint and incorporation of Al at the sediment–water interface. Opal that remains buried in the sediment could represent a significant sink of Al from seawater. 相似文献
11.
大型海藻龙须菜凋落物分解对水质的影响 总被引：1，自引：0，他引：1
大型海藻龙须菜(Gracilaria lemaneiformis)规模栽培具有重要的经济和环境效益, 但藻体的凋落分解会对栽培区和邻近海域水环境造成一定影响。为探讨龙须菜凋落对水环境的影响, 本文通过45d的室内受控实验, 评估了龙须菜凋落分解过程中水体溶解氧和氮、磷的含量变化。结果发现, 干龙须菜实验组在实验期内水体溶解氧浓度显著降低(较对照组降低了82.81%); 水体氮、磷浓度显著提高, 总氮、总磷浓度较对照组分别上升了161.78%和759.93%。鲜龙须菜+海水+沉积物组在实验前中期(第0~21天)水体溶解氧浓度持续降低(较对照组降低了53.92%), 但在21d后又逐渐恢复至对照组水平; 其水体氮、磷浓度在实验中末期亦显著提高, 分解过程总氮、总磷浓度分别较对照组上升了36.65%和177.80%, 水体氮、磷变化曲线较干龙须菜组平缓且迟滞。鲜龙须菜凋落分解过程中的营养盐释放率低于干龙须菜, 沉积物对鲜龙须菜的分解及氮、磷和碳释放有促进作用, 但对干龙须菜的分解及氮、磷和碳释放有一定程度的减缓作用。龙须菜失重率、分解速率及营养盐释放率均呈现如下规律: 干龙须菜+海水组>干龙须菜+海水+沉积物组>鲜龙须菜+海水+沉积物组>鲜龙须菜+海水组。依据上述结果, 建议在龙须菜规模栽培和收获过程中应及时打捞脱落或衰老藻体, 尤其对已收获的大型海藻应妥善处理, 避免大型海藻腐烂而导致水体污染。 相似文献
12.
Samuela Capellacci Cecilia Battocchi Silvia Casabianca Marco Giovine Giorgio Bavestrello Antonella Penna 《Marine Ecology》2013,34(1):103-111
In this study, we demonstrate that dissolved silica obtained from mineral (crystalline quartz), biogenic amorphous (diatomaceous earth) and artificial amorphous sources (Aerosil) influence the growth rate of two marine diatoms, Chaetoceros sp. and Skeletonema marinoi. Diatoms were reared in four different experimental conditions in artificial seawater containing either dissolved silica previously obtained through dissolution of the mineral crystalline quartz or two amorphous substrates, biogenic diatomaceous earth or artificial Aerosil silica. Sodium metasilicate was used as control. When the silica in the different media reached concentrations higher than 107 μm , particles were eliminated by filtration and the diatom cells were inoculated. Maximum cell density, growth and silica assimilation rates of both species in the presence of dissolved silica derived from crystalline quartz and metasilicate were higher than those obtained with the other silica sources. These results are discussed against the background of previous geochemical studies that have shown that silica–water interactions are strictly dependent on the silica polymorphs involved and on the ionic composition of the solution. Our results demonstrate that the soluble silicon compounds generated in seawater by crystalline sources are highly bioavailable compared with those generated by biogenic and amorphous materials. These findings are potentially of considerable ecological importance and may contribute to clarifying anomalous spatial and temporal distributions of siliceous organisms with respect to the presence of lithogenic or biogenic silica sources in marine environments. 相似文献
13.
海湾区海水中的溶存甲烷 Ⅰ.分布特征及成因 总被引：1，自引：0，他引：1
本文基于日本东京湾、伊势湾和浜名湖的调查资料，详细地讨论了海湾区海水中溶存甲烷的分布特征、成因及其来源。溶存甲烷在海湾中的分布主要受物理混合过程所控制；由河流携入和沉积物中产生是海湾区海水中溶存甲烷的两个主要来源。 相似文献
14.
The behaviour of dissolved silica was studied in Tokyo Bay during six surveys in 1979 and 1980. The data from late spring and mid-summer samples showed concave mixing curves of silica versus salinity, whereas for the winter samples a simple conservative dillution curve was obtained. Plots of particulate silicon to particulate aluminium showed that even for winter samples as well as summer ones there were some processes removing silica from solution. The processes could not be adequately explained by adsorption onto suspended solids. The data are indicative of uptake by diatoms as the principal removal mechanism. Most of the diatom skeletons settled to the bottom where dissolution was rapid. The silica-salinity curves in this study thus demonstrate an apparent removal process for dissolved silica. This is because during summer the displacement rate of biogenic silica from a unit water column to the bottom as fecal pellets or by sinking is greater than the supply rate of dissolved silica by the action of diffusion and mixing of bottom water enriched with dissolved silica whereas in winter these rates are reasonably balanced. 相似文献
15.
Surface sediment samples taken from the East China Sea off the Changjiang estuary are used as raw materials for phosphorus releasing experiment. It is found that after being thoroughly mixed with seawater for about 10 minutes, phosphorus released from the sediments reaches its maximum value. Adsorption kinetics can be fitted with both Elovich equation and two-constant rate equation. The releasing amount is closely related to the composition of the sediments. Phosphorus release from silty and muddy sediment is higher than from that dominated by sandy composition. For the desorption reaction, iron-phosphorus(Fe-P) is the most active one, with a releasing ratio higher than other phosphorus forms,followed by absorbed-phosphorus (Ad-P) and organic bound phosphorus (OP). All of them can be referred to as bio-available phosphorus. The results demonstrate that phosphorus in sediments can be released into seawater under suitable hydrodynamic conditions, and have a great impact on the nutrition state and primary productivity of marine biosphere. 相似文献
16.
The diffusion coefficient of dissolved silica revisited 总被引：1，自引：0，他引：1
The diffusion coefficient of dissolved silica was determined for two different salinities, 36 and 0, at temperatures ranging from 2 °C to 30 °C and at an average pH value of 8.1. Our results show limited influence of salinity and a variation by a factor of 2 to 3 of the silica diffusion coefficient within the temperature range considered in this study. The values obtained at 25 °C are in agreement with previous work carried out at room temperature for seawater and freshwater. The dependency on temperature and viscosity of the diffusion coefficient agrees well with the Einstein–Stokes equation. The composition of the solvent appears to be an important factor because it modifies the viscosity and allows for the complexation of the dissolved silica with less mobile ions, while its pH controls the dissolved silica speciation. In seawater, the higher viscosity and the presence of dissociated and polymeric species result in a decrease of the diffusion coefficient compared to freshwater systems. 相似文献
17.
18.
莱州湾滨海湿地沉积物重金属的空间分布 总被引：8，自引：0，他引：8
通过研究莱州湾河口区滨海湿地沉积物重金属Pb,Zn,Cd,Cu的含量变化,分析表层沉积物及柱状沉积物,以期了解莱州湾河口区滨海湿地重金属含量的区域性变化,并从柱状沉积物剖面了解沉积物重金属累积的历史变化。研究结果表明,莱州湾河口区与邻近海域沉积物重金属含量在空间分布上与垂直分布上均呈现一定幅度的变化,且高浓度重金属显示区域内重金属呈现污染状况;在沉积物柱状剖面中,发现重金属含量在上层有大幅度增加之现象。另外,利用围隔式生态实验装置研究了该滨海湿地区域污染沉积物中重金属Pb,Zn,Cd,Cu在海水环境中的行为。结果表明,海水中的还原环境能抑制污染沉积物中重金属的释放,有助于体系中原有的重金属清除出水,而低生产力条件下,Pb,Zn表现出释放行为;高生产力和高悬浮物含量条件下,Pb和Zn表现出先释放后迁移,而Cd和Cu则呈现出相反的现象。 相似文献
19.
基于室内物理模拟实验, 对长江沉积物进行淡水和海水环境下沉积物搬运过程碳释放通量实验模拟。结果表明, 模拟实验初期, 淡水和海水均为大气CO2的源, 但淡水CO2释放通量略高于海水;淡水、海水两种环境下, CH4释放通量均较小, 为弱释放-弱吸收过程。对两种环境下碳通量对比研究发现,Eh 值可能是造成淡水和海水环境下CO2通量差别的主要原因, 而pH 值可能对CO2通量差别的影响较小。两种环境下温室气体通量差别的具体原因仍需进一步研究。通过模拟对比试验, 旨在为系统地认识长江流域水库的温室效应与减排提供科学依据, 为我国清洁水电能源发展提供理论参考。 相似文献
20.
Permeable coastal sediments act as a reactive node in the littoral zone,transforming nutrients via a wide range of biogeochemical reactions.Reaction rates are controlled by abiotic factors,e.g.,salinity,temperature or solute concentration.Here,a series of incubation experiments,using flow-through reactors,were conducted to simulate the biogeochemical cycling of nitrate (NO_3~?) and phosphorus (P) in permeable sediments under differentNO_3~?availability conditions (factor I) along a salinity gradient (admixture of river and seawater,factor II).In an oligotrophic scenario,i.e.,unamendedNO_3~?concentrations in both river and seawater,sediments acted as a permanent net source ofNO_3~?to the water column.The peak production rate occurred at an intermediate salinity(20).IncreasingNO_3~?availability in river water significantly enhanced netNO_3~?removal rates within the salinity range of 0 to 30,likely via the denitrification pathway based on the sediment microbiota composition.In this scenario,the most active removal was obtained at salinity of 10.When both river and seawater were spiked with NO_3~?,the highest removal rate switched to the highest salinity (36).It suggests the salinity preference of theNO_3~?removal pathway by local denitrifiers (e.g.,Bacillus and Paracoccus) and thatNO_3~?removal in coastal sediments can be significantly constrained by the dilution relatedNO_3~?availability.Compared with the obtained variation forNO_3~?reactions,permeable sediments acted as a sink of soluble reactive P in all treatments,regardless of salinity andNO_3~?input concentrations,indicating a possibility of P-deficiency for coastal water from the intensive cycling in permeable sediments.Furthermore,the net production of dissolved organic carbon (DOC) in all treatments was positively correlated with the measuredNO_3~?reaction rates,indicating that the DOC supply may not be the key factor forNO_3~?removal rates due to the consumption by intensive aerobic respiration.Considering the intensive production of recalcitrant carbon solutes,the active denitrification was assumed to be supported by sedimentary organic matter. 相似文献