夏季长江口海域溶解态铁的分布及混合行为研究

本文基于2015年7月长江口的现场调查资料,分析讨论了长江河口区溶解态铁(DFe)的含量分布与混合行为及其影响因素。结果表明:长江径流携带大量的DFe入海,且口内区(Ⅰ)浓度高于混合区(Ⅱ)和外海区(Ⅲ),平均浓度分别为166.45±6.26nmol/L,14.04±8.80nmol/L和6.18±1.51nmol/L。受去除作用和海水稀释的影响,在河口区DFe的浓度下降率达到96.92%。DFe浓度与盐度的关系符合指数模型,由模型与理论稀释线估算的长江口海域DFe的理论最大去除率为97.75%,与实际测得的最大浓度下降率相近。长江冲淡水、苏北沿岸流和台湾暖流影响DFe的水平分布。受长江冲淡水影响,长江口外海域DFe浓度高达176.50nmol/L。苏北沿岸流主要影响研究区域北部的表层水,其携带的DFe浓度低于长江冲淡水。台湾暖流是导致研究区域东南部DFe浓度较低的主要原因,使得中层和底层水中浓度分别低至4.04nmol/L和4.79nmol/L。另外,在表层海水中DFe的分布受到叶绿素a、溶解有机碳和溶解氧的共同影响,DFe与叶绿素a、溶解氧呈显著负相关,与溶解有机碳呈显著正相关。     

Transformation of Fe （Ⅱ） and Fe （Ⅲ） in Enclosures of Dongshan Bay

根据2008年8月与11月在东山湾海域获得的调查资料对表层水中溶解态Fe（II）和Fe（III）含量、浮游植物叶绿素a、营养元素及其浓度等环境参数进行分析。结果表明,夏、秋季海水中Fe（II）浓度及其在总溶解铁中所占比例均与浮游植物叶绿素a呈正相关,其相关系数分别为0.7959、0.9219。现场围隔实验表明,海水中总溶解态Fe含量在24 h内有较大的变化,最大减少量达到17.4%。DS2站点海水中Fe（II）浓度及其在总溶解铁中所占比例随光照强度增加而增加。最高值与初始值相比较,叶绿素a较高的DS2站点海水中Fe（II）浓度增加较叶绿素a较低的DS5号站点高0.053μg/L。Fe（II）和Fe（III）加富实验研究了溶解态的Fe（II）和Fe（III）在海水中相互转化。高浓度的Fe（II）在海水中被氧化成Fe（III）,海水中浮游植物也会引发光还原作用使Fe（III）还原成Fe（II）。     

东山湾海水中Fe(II)和Fe(III)相互转化围隔实验研究

根据2008 年8 月与11 月在东山湾海域获得的调查资料对表层水中溶解态Fe(II)和Fe(III)含量、浮游植物叶绿素a、营养元素及其浓度等环境参数进行分析。结果表明, 夏、秋季海水中Fe(II)浓度及其在总溶解铁中所占比例均与浮游植物叶绿素a 呈正相关, 其相关系数分别为0.7959、0.9219。现场围隔实验表明, 海水中总溶解态Fe 含量在24 h 内有较大的变化, 最大减少量达到17.4%。DS2 站点海水中Fe(II)浓度及其在总溶解铁中所占比例随光照强度增加而增加。最高值与初始值相比较, 叶绿素a 较高的DS2 站点海水中Fe(II)浓度增加较叶绿素a 较低的DS5 号站点高0.053μg/L。Fe(II)和Fe(III)加富实验研究了溶解态的Fe(II)和Fe(III)在海水中相互转化。高浓度的Fe(II)在海水中被氧化成Fe(III),海水中浮游植物也会引发光还原作用使Fe(III)还原成Fe(II)。     

秋季浙闽沿岸溶解态Cu分布特征及其影响因素

铜(Cu)是海洋浮游植物生长不可或缺的痕量金属之一,对海洋初级生产力起着关键作用。河流是海洋中Cu的重要来源,河口及边缘海对河流输入的Cu起着重要的改造作用,但目前对Cu在浙闽沿岸的生物地球化学行为尚不明确。本研究使用自动固相萃取-电感耦合等离子体联用技术对2021年11月浙闽沿岸及其邻近水域表层水的溶解态铜(dCu)浓度进行分析。结果显示,该区域dCu浓度范围为3.38～26.28 nmol·L^–1,平均浓度为11.66±5.83nmol·L^–1。在研究区域内, dCu的空间分布呈北高南低,近岸高、远岸低的特征。此外, dCu在浙闽沿岸表现出较高的保守性,其与盐度呈显著负相关关系,表明dCu在一定程度上可用于指示人为影响。相关性分析表明,浙闽沿岸及其邻近水域表层dCu的生物地球化学行为和分布可能受到陆源输入、水团输运混合、化学絮凝与吸附等过程的影响。本研究结果有助于进一步理解Cu在海洋中的生物地球化学过程,为探究该区域的生态环境变化提供科学依据。     

大洋溶解铁的物质来源及其同位素示踪

铁(Fe)作为海洋初级生产所必需的微量和限制性营养元素影响着海洋生物群落结构、生态功能以及碳循环,理解溶解Fe的物质来源及其对气候变化的响应具有重要的科学意义。早期研究多强调风尘输入是维持大洋Fe循环的主要机制。近年来,随着海水Fe分析数据的积累,尤其是痕量元素及其同位素海洋生物地球化学循环研究计划(GEOTRACES)的开展,陆架沉积物和热液活动所释放Fe的贡献开始越来越受到重视。尽管如此,不同物源对开阔大洋溶解Fe的影响依然存在相当的不确定性。以海水溶解Fe的化学组分为出发点,强调有机配体对大洋Fe循环的决定性作用,综述了不同来源Fe的通量估计和第四纪大洋Fe来源的研究争议。铁同位素为理解大洋Fe的物源演变提供了新的工具。讨论了不同物源的Fe同位素特征,并提出结合沉积物的活动性Fe同位素和组分研究可能为理解过去陆架-热液活动-风尘输出与输运Fe的机制提供全新视角。     

厦门港近岸水域中粪大肠菌群分布的初步研究

早在1885年,埃希氏从粪便中发现了大肠杆菌(Escherichia coli),尔后用它作为水、食品、土壤等被粪便污染的标志,海水中大肠菌群是水质污染的重要指标之一.假若沿海城市沿岸、海水浴场和各种养殖场等水域遭受到污水严重污染时,都可能引起某些疾病的发生和流行.因此,调查和监测沿岸水域中粪大肠菌群数,将具有重要的卫生学和流行病学意义,国外,尤其是日本对港湾、流入海域河口和太平洋沿岸水域以及某些经济性海域(如贝类养殖场)大肠菌群的分布作过大量调查研究[1-9],研究指出,盐度、pH、紫外线照射强度和海洋细菌、浮游植物所产生的有害物质是影响海水中大肠菌群存活率的重要因素[10-13],迄今为止,有关海水中粪大肠菌群的分布,我国尚未见报道.本文对厦门港近岸水域中粪大肠菌群分布及其一些影响因素作了初步调查分析.     

长江口及其邻近海域大银鱼生态的初步研究

本文对长江口及其邻近海域大银鱼的繁殖、食性、生长、分布与洄游作了初步研究。长江河口大银鱼分布于盐度为0.01—30‰的水域。繁殖时期洄游到河口的淡水至12‰左右的咸淡水水域中产卵。大银鱼是在河口淡水和沿岸低盐度海水中繁殖的河口鱼类。湖泊中的大银鱼是被陆封在湖泊中的。     

河口生物学

河口生物学是研究河口这一特定水域中的生物的科学。河口是海水与淡水交汇及混合的水域,也包括一部分沿岸水域;其盐度和温度条件短期(半日)和长期(周年)变化都很大。河口水域的饵料很丰富,为许多生物的栖     

胶州湾海水痕量金属?溶解有机质分配特征及其影响因素探讨

采集胶州湾表层和底层海水样品,分析了Cu、Cr、Cd、Pb、Ni、Co等痕量金属在海水中的空间分布特征及其在不同分子量溶解有机质中的分配特征,并探讨了痕量金属?溶解有机质分配机理及浮游生物活动与盐度等环境因素对该分配过程的影响。结果表明,胶州湾海水中痕量金属呈近岸浓度较高的分布特征,在湾东北部出现高值区,Cd和Pb还分别在湾口与湾中部出现高值区。胶州湾海水中痕量金属平均有70.1%分配于低分子量(<1 kDa)组分中,其中Cu和Cd低分子量组分所占平均比例分别达79.0%与77.6%,Cr、Ni和Co稍低,分别为71.5%、67.3%及66.9%,Pb则仅为58.2%。海水中的溶解有机碳也以低分子量组分为主,所占比例平均达73.1%,且光谱特征显示低分子量溶解有机质中类腐殖质含量更高,含有丰富的羧基和羟基,金属配合能力较高,导致痕量金属多分配于低分子量溶解有机质中。高分子量溶解有机质(>1 kDa)所占比例与叶绿素a浓度呈显著正相关,表明浮游植物初级生产通过释放高分子量溶解有机质影响海水痕量金属?溶解有机质的分配过程。胶州湾湾顶盐度较低海域痕量金属高分子量组分略高,可能是生物活动及陆源输入(产生更多高分子量溶解有机质)与盐度(低盐有利于高分子量有机质的稳定性)共同作用的结果。     

黄河口及其邻近海区溶解态砷的分布及存在形式

作者以阳极溶出伏安法和氢氧化铁共沉淀—DDC—Ag法测定了黄河口表层海水中溶解态总砷、溶解态有机砷、溶解无机砷、砷(Ⅲ)和砷(Ⅴ)的含量。实验结果表明:1、黄河口区表层海水中丰水期溶解态无机砷的平均浓度(2.26μgL~(-1))高于枯水期的平均浓度(1.43μgL~(-1));2、枯水期内,表层海水中溶解态无机砷浓度与海水盐度之间存在良好的相关性,而在丰水期内无此相关关系;3、两航次中溶解态无机砷的平面分布呈明显的梯度分布,即由河口向渤海湾中部方向溶解态无机砷浓度递减。     

A comparison of iron limitation of phytoplankton in natural oceanic waters and laboratory media conditioned with EDTA

The solubility of iron in oxic waters is so low that iron can be a limiting nutrient for phytoplankton growth in the open ocean. In order to mimic low iron concentrations in algal cultures, Ethylenediaminetetraacetate (EDTA) is commonly used. The presence of EDTA enables culture experiments to be performed at a low free metal concentration, while the total metal concentrations are high. Using EDTA provides for a more reproducible medium. In this study Fe speciation, as defined by EDTA in culture media, is compared with complexation by natural organic complexes in ocean water where Fe is thought to be limited. To grow oceanic species into iron limitation, a concentration of at least 10⁻⁴ M EDTA is necessary. Only then does the calculated [Fe³⁺] concentrations resemble those found in natural sea water, where the speciation is governed by natural dissolved organic ligands at nanomolar concentrations. Moreover, EDTA influences the redox speciation of iron, and thus frustrates research on the preferred source of Fe-uptake, Fe(III) or Fe(II), by algae. Nowadays, one can measure the extent of natural organic complexation in sea water, as well as the dissolved Fe(II) state, and can use ultra clean techniques in order to prevent contamination. Therefore, it is advisable to work with more natural conditions and not use EDTA to create iron limitation. This is especially important when the biological availability of the different chemical fractions of iron are the subject of research. Typically, many oceanic algae in the smallest size classes can still grow at very low ambient Fe and are not easily cultivated into limitation under ambient sea water conditions. However, the important class of large oceanic algae responsible for the major blooms and the large scale cycling of carbon, silicon and other elements, commonly has a high Fe requirement and can be grown into Fe limitation in ambient seawater.     

Iron regeneration and organic iron(III)-binding ligand production during in situ zooplankton grazing experiment

To elucidate iron regeneration and organic iron(III)-binding ligand formation during microzooplankton and copepod grazing on phytoplankton, incubation experiments were conducted in the western subarctic Pacific. During 8 days of dark incubation of ambient water and that amended with plankton concentrate, dissolved iron and organic iron(III)-binding ligands accumulated, approximately proportionally to the decrease in chlorophyll a. The observed increases in dissolved iron concentration were much greater than those expected from the consumption of phytoplankton biomass and previously reported Fe:C value of cultured algal cells, suggesting resolution from colloidal or particulate iron adsorbed onto the algal cell surface. When copepods were added to the ambient water, organic iron(III)-binding ligands accumulated more rapidly than in the control receiving no copepod addition, although consumed phytoplankton biomass was comparable between the two treatments. Bioassay experiment using filtrates collected from the incubation experiment showed that organic ligands formed during microzooplankton grazing reduced the iron bioavailability to phytoplankton and suppressed their growth. Moreover, picoplankton Synechococcus sp. and Micromonas pusilla were more suppressed by the organic ligands than the diatom Thalassiosira weissflogii. In conclusion, through microzooplankton and copepod grazing on phytoplankton, organic iron(III)-binding ligands as well as regenerated iron are released into the ambient seawater. Because the ligands lower iron bioavailability to phytoplankton through complexation and the degree of availability reduction varies among phytoplankton species, grazing by zooplankton can shift phytoplankton community structure in iron-limited waters.     

Influence of atmospheric inputs on the iron distribution in the subtropical North-East Atlantic Ocean

Aerosol (soluble and total) iron and water-column dissolved (DFe, < 0.2 μm) and total dissolvable (TDFe, unfiltered) iron concentrations were determined in the Canary Basin and along a transect towards the Strait of Gibraltar, in order to sample across the Saharan dust plume. Cumulative dust deposition fluxes estimated from direct aerosol sampling during our one-month cruise are representative of the estimated deposition fluxes based on near surface water dissolved aluminium concentrations measured on board. Iron inventories in near surface waters combined with flux estimates confirmed the relatively short residence time of DFe in waters influenced by the Saharan dust plume (6–14 months). Enhanced near surface water concentrations of DFe (5.90–6.99 nM) were observed at the Strait of Gibraltar mainly due to inputs from metal-rich rivers. In the Canary Basin and the transect towards Gibraltar, DFe concentrations (0.07–0.76 nM) were typical of concentrations observed in the surface North Atlantic Waters, with the highest concentrations associated with higher atmospheric inputs in the Canary Basin. Depth profiles showed that DFe and TDFe were influenced by atmospheric inputs in this area with an accumulation of aeolian Fe in the surface waters. The sub-surface minimum of both DFe and TDFe suggests that a simple partitioning between dissolved and particulate Fe is not obvious there and that export may occur for both phases. At depths of around 1000–1300 m, both regeneration and Meddies may explain the observed maximum. Our data suggest that, in deep waters, higher particle concentrations likely due to dust storms may increase the scavenging flux and thus decrease DFe concentrations in deep waters.     

Variations in the chemical lability of iron in estuarine, coastal and shelf waters and its implications for phytoplankton

The relationship between total and chemically labile Fe has been studied in estuarine, coastal and shelf waters of the Gulf of Maine, U.S.A. Measurements of the labile fraction of total Fe, defined by complexation with 8-hydroxyquinoline in 1 h, correlate with the availability of Fe to marine phytoplankton and therefore can be used to estimate Fe availability in seawater. The results show that the relative lability (=labile/total) of Fe in seawater varied both spatially and temporally from near-zero to 100%. Although particulate Fe (>0.45 μm) was generally less labile than dissolved Fe (<0.45 μm), the particulate fraction often contributed substantially to labile Fe concentrations overall. Conversely, as much as 75% of ‘dissolved’ Fe was non-labile, and therefore was probably not available to phytoplankton. In seawater/river-water mixing experiments, aggregation diminished the relative lability of Fe by 30%, even though much of it remained in the ‘dissolved’ fraction. Considering phytoplankton nutrition, these results demonstrate that equating dissolved Fe concentrations with ‘available’ metal can be misleading. Furthermore, the large variability observed in the labile proportion of total Fe in seawater indicates that Fe availability to phytoplankton cannot be estimated by applying fixed lability-ratios to total Fe concentrations.     

The Distribution and Redox Chemistry of Iron in the Pettaquamscutt Estuary

A series of high resolution (10 cm) vertical profiles of iron were determined across the oxic/anoxic boundary in the Lower Pond of the Pettaquamscutt Estuary. Selective chemical treatments and multiple analytical methods were used to detemine the oxidation state and lability of iron across the oxic/anoxic boundary. The vertical distributions of dissolved and total iron were determined by atomic absorption spectroscopy, and dissolved Fe(II) and reducible iron were determined using a modified Ferrozine spectrophotometric method. Well-developed maxima of total dissolved iron ≈7·5 μM occurred within the oxic/anoxic transition zone. Analysis of Fe(II) by the FZ method indicates that more than 95% of the dissolved iron determined by atomic absorption spectroscopy within the maximum is in the form of Fe(II). The concentration of dissolved Fe(II) ranged from <4 nM in oxygenated surface waters to between 7 and 8 μM at the total dissolved iron maximum.Both dissolved and total iron samples were treated with ascorbic acid to quantify the fraction of iron that was reducible in this system. Dissolved iron is quantitatively reduced to Fe(II) by 3·5 m depth, and particulate iron was almost completely dissolved by 6 m. Thermodynamic speciation calculations indicate that the dominant species of Fe(II) in the anoxic waters is the Fe(HS)⁺complex. In addition, the concentration of Fe(II) in the anoxic zone appears to be controlled by precipitation of a sulfide phase, the ion activity product for waters below 7 m is in good agreement with the solubility product of mackinawite.The vertical distribution of oxidation states of the metals indicates non-equilibrium conditions due to microbiological and chemical processes occurring in the redox transition zone. A one-dimensional vertical, eddy diffusion model is presented that incorporates redox reactions of iron, sulfide and oxygen. The modeling suggests the maximum in Fe(II) can be achieved through inorganic oxidation and reduction reactions, however the depth at which the maximum occurs is sensitive to sulfide oxidation, which appears to be dominated by biological oxidation. The magnitude of the Fe(II) maximum depends on the flux of iron into the basin, and reductive dissolution of particulate iron.     

Iron, manganese and aluminum in upper waters of the western South Pacific Ocean and its adjacent seas

Total dissolvable iron, manganese and aluminum distributions in upper waters were determined in the western South Pacific, Solomon Sea, Coral Sea, and Tasman Sea. In these oceanic regions, the surface aluminum distributions well reflect the atmospheric deposition pattern of mineral dust in the western South Pacific reported previously. Surface manganese distributions derive mainly from lateral transportation from the coastal sediments of western tropical islands. Compared to Mn and Al, the Fe distributions reflect the nutrient cycle in upper waters. Iron limitation over the vast South Pacific, as revealed by physiological features of phytoplankton, seems to be caused by low atmospheric dust deposition and low Fe:N ratios in deep waters. In the western South Pacific, with its unique geographic and oceanographic settings, the local sources of trace metals might considerably affect their biogeochemical cycles.     

Leachable particulate iron in the Columbia River,estuary, and near-field plume

This study examines the distribution of leachable particulate iron (Fe) in the Columbia River, estuary, and near-field plume. Surface samples were collected during late spring and summer of 2004–2006 as part of four River Influence on Shelf Ecosystems (RISE) cruises. Tidal amplitude and river flow are the primary factors influencing the estuary leachable particulate Fe concentrations, with greater values during high flow and/or spring tides. Near the mouth of the estuary, leachable particulate Fe [defined as the particulate Fe solubilized with a 25% acetic acid (pH 2) leach containing a weak reducing agent to reduce Fe oxyhydroxides and a short heating step to access intracellular Fe] averaged 770 nM during either spring tide or high flow, compared to 320 nM during neap tide, low flow conditions. In the near-field Columbia River plume, elevated leachable particulate Fe concentrations occur during spring tides and/or higher river flow, with resuspended shelf sediment as an additional source to the plume during periods of coastal upwelling and spring tides. Near-field plume concentrations of leachable particulate Fe (at a salinity of 20) averaged 660 nM during either spring tide or high flow, compared to 300 nM during neap tide, low flow conditions. Regardless of tidal amplitude and river flow, leachable particulate Fe concentrations in both the river/estuary and near-field plume are consistently one to two orders of magnitude greater than dissolved Fe concentrations. The Columbia River is an important source of reactive Fe to the productive coastal waters off Oregon and Washington, and leachable particulate Fe is available for solubilization following biological drawdown of the dissolved phase. Elevated leachable Fe concentrations allow coastal waters influenced by the Columbia River plume to remain Fe-replete and support phytoplankton production during the spring and summer seasons.     

The chemical speciation of iron in the north-east Atlantic Ocean

The distribution of dissolved iron and its chemical speciation (organic complexation and redox speciation) were studied in the northeastern Atlantic Ocean along 23°W between 37 and 42°N at depths between 0 and 2000 m, and in the upper-water column (upper 200 m) at two stations further east at 45°N10°W and 40°N17°W in the early spring of 1998. The iron speciation data are here combined with phytoplankton data to suggest cyanobacteria as a possible source for the iron binding ligands. The organic Fe-binding ligand concentrations were greater than that of dissolved iron by a factor of 1.5–5, thus maintaining iron in solution at levels well above it solubility. The water column distribution of the organic ligand indicates in-situ production of organic ligands by the plankton (consisting mainly of the cyanobacteria Synechococcus sp.) in the euphotic layer and a remineralisation from sinking biogenic particles in deeper waters. Fe(II) concentrations varied from below the detection limit (<0.1 nM) up to 0.55 nM but represented only a minor fraction of 0% to occasionally 35% of the dissolved iron throughout the water column. The water column distribution of the Fe(II) suggests biologically mediated production in the deep waters and photochemical production in the euphotic layer. Although there was no evidence of iron limitation in these waters, the aeolian iron input probably contributed to a shift in the phytoplankton assemblage towards increased Synechococcus growth.