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1.
The chemical forms and distribution of dissolved arsenic species in the estuary of the River Beaulieu (Hampshire, U.K.) are reported. ‘Inorganic arsenic (V)’ in both the marine and riverine estuary inputs are in true solution, passing through ultrafiltration membranes having a nominal molecular weight cut-off of 500 daltons. Extensive removal of dissolved ‘inorganic arsenic (V)’ is apparent from the distribution of arsenic in the estuary, with laboratory mixing experiments indicating that removal is favoured in the low salinity region. ‘Inorganic arsenic (III)’ and methylated arsenic species account for up to 41% and 70% of the dissolved arsenic, respectively, but are only found during the warmer months when water temperatures exceed ca. 12°C. 相似文献
2.
《Estuarine, Coastal and Shelf Science》1987,25(4):413-434
The distribution of 239,240Pu between dissolved and particulate forms has been measured in four estuaries on the north-east coast of the United States (Connecticut River, Delaware Bay, Chesapeake Bay, and Mullica River). The data cover the whole salinity range from freshwater input to shelf waters at 35‰ and includes one profile from a nearly anoxic basin in the Chesapeake Bay.In the organic-rich Mullica River estuary, large-scale removal of riverine dissolved 239,240Pu occurs at low salinities due to salt-induced coagulation, a mechanism analogous to that for iron and humic acids. Within the 0 to 25–30‰ zone in the other three estuaries, the activity of dissolved 239,240Pu increases almost conservatively. The activities of particulate 239,240Pu are highest in the more turbid waters of low salinity regime (0–15‰), but become increasingly insignificant with respect to dissolved 239,240Pu as salinities increase. At higher salinities corresponding to shelf water, there is a sharp increase in dissolved 239,240Pu activity. The dissolved 239,240Pu activity within each estuary appears to be inversely related to the flushing time of water. For example, Chesapeake Bay has a 6–12 month flushing time and has much lower dissolved 239,240Pu activities than does the Connecticut River Estuary which has a flushing time of a few days. This and other data from the shelf waters are interpreted as indicating that the sharp decrease in dissolved 239,240Pu activities between shelf and estuarine waters is driven by removal within the estuaries themselves rather than on the shelf.Dissolved 239,240Pu activities are lower in the nearly-anoxic bottom waters of Chesapeake Bay indicating enhanced removal by redox transformation of Pu [i.e., Pu(V) to Pu(IV)]. 相似文献
3.
The spectral absorption properties of chromophoric dissolved organic matter (CDOM) and their distributions in two Chinese estuaries, the Yangtze River Estuary and the Jiulong River Estuary, were studied during August 2003 (wet season) and during different seasons between 2003−2005, respectively. The CDOM concentrations (a355) of fresh end members in the Jiulong River Estuary varied seasonally, while its quality remained relatively stable. However, the a355 of the marine end members exhibited less variability. Application of a conservative mixing model indicated that CDOM behaved conservatively in the Yangtze River Estuary. No photobleaching removal was observed at high salinity region of this estuary. Although CDOM showed conservative behavior for many cruises in the Jiulong River Estuary, there was evidence for removal in the low salinity regions during some cruises. Laboratory mixing experiments and a salt addition experiment suggested that particle sorption of CDOM maybe the possible reason for the removal. These results showed that absorption properties of CDOM can be used as a tool to observe the quantitative and qualitative dynamics of DOM during estuarine mixing. 相似文献
4.
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。 相似文献
5.
Sherry M. Lippiatt Matthew T. Brown Maeve C. Lohan Carolyn J.M. Berger Kenneth W. Bruland 《Estuarine, Coastal and Shelf Science》2010
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. 相似文献
6.
Rob F. Nolting Wim Helder Hein J. W. de Baar Loes J. A. Gerringa 《Journal of Sea Research》1999,42(4):2393
Dissolved and particulate trace metals (Cu, Cd, Pb, Zn, Ni, Fe and Mn) measured at six stations along the Scheldt estuary in October/November 1978 are compared with more recent data. Based on Ca content in the suspended matter, three distinct geochemical regions could be distinguished: the upper estuary (salinity 1–7) dominated by fluvial mud, mid-estuary (salinity 7–17) where the composition of the suspended matter remained relatively constant, and the lower estuary where marine mud prevailed. Re-suspension of sediments is the major factor controlling the composition of the particles in the upstream region. Anoxic conditions prevailed in the upper part of the estuary extending to a salinity of 15 in 1978, while at present the seaward boundary of the anoxic water body is located at less saline waters. Furthermore, the present-day metal load is much lower than in 1978. As a consequence of the changed situation, maxima in dissolved concentrations of redox-sensitive metals in the mid/lower estuary have moved as well, which affects the trace metal re-distribution pattern. In the anoxic zone, exchange processes between dissolved and particulate metal fractions were strongly redox regulated, with Fe and Mn as excellent examples. Iron was removed from the dissolved phase in the early stages of mixing resulting in an increase in the suspended particulate matter of the leachable ‘non-residual' Fe fraction from 2 to 3.5%. Due to its slower kinetics, removal of Mn from solution occurred in mid-estuary where oxygen concentrations increased. Cu, Cd and Zn on the contrary were mobilised from the suspended particles during estuarine mixing. External inputs of Pb, and to a lesser extent of Cu, in the lower estuary resulted in the increase of their particulate and the dissolved concentrations. Calculated Kd (distribution coefficient) values were used to assess the redistribution between the dissolved and particulate phase of the investigated metals. Due to the existence of the anoxic water body in the upper estuary, the importance of redox processes in determining the Kd values could be demonstrated. The sequence of Kd values in the upper estuary (Fe, Cd, Zn, Pb > Cu > Ni, Mn) is significantly different from that in the lower estuary (Fe > Mn > Pb, Ni, Zn, Cu, Cd). Thus, in such a dynamic estuary single metal-specific Kd values cannot be used to describe redistribution processes. 相似文献
7.
河水径流是海洋营养盐最重要的来源之一。河流排放的营养盐为河口海区自养生物的繁殖提供了重要保证，但是过量的营养盐反会引起海水污染和水域富营养化，从而危及海洋生物的生命活动。研究河口及其附近海域营养盐的分布变化，不仅对了解它们在河水－海水界面的转移规律，而且对河口生态学的研究均具有重要意义，因此日益受到重视(顾宏堪等，1981；王正芳等，1983；林植青等，1984；吕小乔等，1985；沈志良等，1987)。
本文主要对黄河口及其附近海区水中硝酸盐、亚硝酸盐、氨氮和磷酸盐的分布特征、在河口的转移过程以及它们与浮游植物的关系等进行一些探讨。 相似文献
8.
The concentrations of rare earth elements in the dissolved, acid-soluble and residual phases in surface waters of the Changjiang
Estuary were determined using ICP-MS. The main purposes of the study are to understand the estuarine geochemistry of rare
earth elements and to explore water-particle interactions in the Changjiang estuarine mixing zone. The results show that there
are two distinct processes operating on dissolved rare earth elements in the estuary: large scale removal at low salinities
due to salt-induced coagulation and remarkable release at mid to high salinities. These processes result in modification of
the effective river water flux and the systematical fractionation of the dissolved rare earth elements toward the East China
Sea. The increase in concentration of dissolved rare earth elements in the mid to high salinity waters of the Changjiang Estuary
suggests a sediment source in the mixing zone of the estuary, which is located over a shallow, broad shelf where there is
extensive physical contact between bottom sediment and estuarine waters. Acid-soluble rare earth elements, the concentrations
of which also dropped sharply in the low salinity region, appear to be controlled by salt-induced coagulation process and
intense deposition of suspended particulate matter in the low salinity region. In the mid to high salinities, all acid-soluble
rare earth element concentrations increase slightly with increasing salinity, suggesting that resuspension of sediments occurred.
In contrast, the residual rare earth element concentrations are relatively constant with salinity variation in the Changjiang
estuarine surface waters. 相似文献
9.
The mixing behaviour of iron, manganese, phosphate and humic acid in a Delaware salt marsh creek was studied using field data, laboratory mixing experiments, and geochemical mass balance equations. Property-salinity diagrams for field data indicated that the removal of iron is 56–70% in the 0–10‰ salinity range. A proposed mechanism of removal is the flocculation of colloidal iron, perhaps with humic acid. Phosphate, however, undergoes 195% addition in the same low salinity region, which may be due to release of phosphate from resuspended sediments. Dissolved manganese is conserved, as is humic acid throughout the salt marsh mixing zone. Within the uncertainty of the data the maximum possible removal of humic acid is 23%.Laboratory mixing experiments that simulated salt marsh mixing along the same salinity gradient as observed in the field (5–25‰) showed only small-scale additions and removals compared to the field results. Such small-scale changes occurred largely at salinities >10‰ in the laboratory experiments, whereas most removals and additions occurred at salinities <10‰ in the field. Mixing studies also showed little difference between prefiltered and unfiltered mixes. The studies suggest that simple mixing of salt marsh waters, with or without suspended material, does not strongly influence the observed behaviour of dissolved constituents in salt marshes, and that other processes (e.g. sediment or intertidal exchange) must dominate their behaviour. 相似文献
10.
L.E. Fox 《Estuarine, Coastal and Shelf Science》1983,16(4):431-440
A simple method for the determination of dissolved humic acid based on carbon analysis is presented. This method was used to measure the distribution of dissolved humic acids in seven coastal plain estuaries located in the middle-Atlantic United States. Results indicate that 100% of the dissolved humic acid was removed during estuarine mixing, although concurrent measurements of dissolved organic carbon showed either production or conservative behavior in regions of the estuary where humic acid removal was observed. It is apparent from these observations that removal of dissolved humic acid is a minor part of the estuarine transport of dissolved organic carbon.Laboratory experiments carried out by mixing river water with sea water demonstrated that salt-induced removal of dissolved humic acid was insignificant in two of three estuaries studied. These results suggest in situ removal of dissolved humic acid may not be universally caused by increasing estuarine salinity. 相似文献
11.
The distribution of dissolved (soluble and total) and particulate (leachable and total) aluminum was examined in the Columbia River and estuary, in near-field and far-field river plumes, and in adjacent coastal waters of Washington and Oregon during the River Influence on Shelf Ecosystems (RISE) cruise of May/June 2006. Dissolved and particulate aluminum (Al) concentrations were significantly greater in the river than in the coastal waters that mixed to form the plume. Dissolved Al concentrations in the Columbia River (∼80 nM) were low relative to other major rivers. Leachable and total particulate Al concentrations within the river reached concentrations greater than 1000 nM and 18,000 nM, respectively. Dissolved Al within the Columbia River estuary showed a significant removal (∼60%) at salinities between 0 and 10 with salt-induced flocculation of colloidal Al complexes and enhanced particle scavenging being probable explanations for aluminum removal. Dissolved and particulate Al concentrations were significantly greater in near-field plumes relative to surrounding coastal waters. As the plume advected from near-field to far-field away from the river mouth, dilution of the plume with lower dissolved Al surface waters as well as particle scavenging along the flow path appeared to be controlling dissolved Al distributions. Particle settling as well as dilution with lower particle-load waters led to observed decreases in particulate Al as the plume moved from near-field to far-field. However, the percent-leachable particulate aluminum in both near-field and far-field plumes was remarkably constant at ∼7%. Dissolved and particulate Al in a far-field plume over 100 km southwest of the Columbia River mouth were over an order-of-magnitude greater than surrounding waters, illustrating the importance of the Columbia River plume as a mechanism for transporting Al offshore. Aluminum could be used to trace the input of biologically-required elements such as iron into waters off the shelf. 相似文献
12.
利用高精度的电感耦合等离子体质谱仪对2014年1月长江口表层水中溶解铀浓度及其234U/238U比值、2013年3月长江口表层沉积物中各矿物组分的铀含量及其234U/238U比值进行了测定,研究了其空间分布特征和影响因素。结果表明:除了长江径流和海水之外,长江口还有其他的溶解铀来源。水体中过剩铀与悬浮颗粒物浓度呈现显著相关性（r2=0.96）。对长江口表层沉积物进行的序列提取实验进一步表明,水体中悬浮颗粒物或沉积物中可解吸态和碳酸钙结合态铀可以在河口区域释放进入水体,而铁锰氧化物和有机物结合铀比较稳定,不受河口区混合过程的影响。每千克颗粒物或沉积物能够释放约2 μmol颗粒态铀,使其转化为溶解态。然而,铁氢氧化物和细颗粒物的絮凝吸附作用也可使溶解铀同时从河口水体中清除。在低盐度区,铀的清除和添加过程速率相近,使溶解铀呈现暂时的"伪保守"现象:颗粒态释放的铀具有明显低的234U/238U比值,导致水体的234U/238U低于保守混合值。在中高盐度区域,溶解铀呈现明显的富集现象。但是由于水相和颗粒相中的铀交换,可释放颗粒态铀的234U/238U接近溶解铀的234U/238U比值,从而导致水体的234U/238U比值呈现出保守性。长江口颗粒物的铀释放通量为（3.48±0.41）×105 mol/a,约占输入的总颗粒态铀通量（1.80±0.17）×106 mol/a的19.3%。长江口输入东海的溶解铀总通量（河流溶解态铀与河口添加铀之和）为（2.68±0.13）×106 mol/a,约为世界河流入海铀通量的11.7%。 相似文献
13.
根据2002—2003年珠江口12个航次的调查资料,分析探讨了不同调查时间和区域浮游幼虫的组成类型、丰度变化和环境因子的影响。以表层盐度(S)变化将调查海域划分成三个区域:I区(S<25)、II区(2530)。12个航次的调查结果显示:调查海域共出现浮游幼虫12个类型,隶属5个动物门,II区和III区的类型数一般高于I区,软体动物门和棘皮动物门的幼虫只出现在II区和III区。其中2002年7月(夏季)、2003年1月(冬季)和4月(春季)的3个大航次结果表明珠江口浮游幼虫的平均丰度为61ind/m3,三个区域的平均丰度比较为II区(124ind/m3)>I区(33ind/m3)>III区(27ind/m3),春夏季的丰度高于冬季。另外在I区进行了9个小航次调查的研究表明:I区浮游幼虫平均丰度较高,月份之间的丰度差别明显,不同站位之间也有差别。温度和食料是影响珠江口浮游幼虫丰度变化的主要因素。 相似文献
14.
The behavior of dissolved and particulate iron and manganese and dissolved silicon has been studied as a function of chlorinity in the Peconic River estuary, New York. This study sought to identify important geochemical processes in a relatively pristine estuary facing increasing anthropogenic impact.Dissolved iron behaved in the classical non-conservative manner exhibiting removal of nearly 80% at very low chlorinities, while particulate iron increased by a corresponding amount over the same chlorinity range. Dissolved manganese was enriched by up to 200% over its predicted concentration at low and intermediate chlorinities by desorption from suspended particulates and by a probable benthic flux. Dissolved silicon was enriched by up to 100% at low and intermediate chlorinities also from a probable benthic flux. These fluxes were estimated to be 5 μg cm?2 day?1 for dissolved manganese and 70 μg cm?2 day?1 for dissolved silicon.The quantity of both particulate iron and manganese increased at high chlorinities due to an influx of suspended inorganic particulates. In the intermediate to high chlorinity region, oxidation of sediment-derived manganese is believed to contribute to the observed increase in particulate manganese.Total iron was essentially conservative throughout most of the estuary, while total manganese was non-conservative presumably due to extensive remobilization of dissolved manganese from the sediments. 相似文献
15.
东山湾海水中Fe(II)和Fe(III)相互转化围隔实验研究 总被引：1，自引：0，他引：1
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)。 相似文献
16.
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
17.
Norio Ogura Yoshiharu Tanaka Jun-ichi Itoh Katsufumi Takahashi 《Journal of Oceanography》1984,40(3):184-191
Behaviour of dissolved and particulate proteinaceous substances in the estuary of the Tama River was investigated through field observations and laboratory experiments. Concentrations of dissolved proteinaceous substances in estuarine water were determined at eight stations between the mouth of the Tama River (TA-15) and a point 16km upstream (TA-8), using the colorimetric method of Lowryet al. (1951) that employs Folin phenol reagent. The results were expressed in terms of Folin phenol active substances (FPAS). It was found that FPAS decreased with increasing salinity and that the proportion of high molecular weight FPAS (molecular weight greater than 100,000) decreased rapidly in the estuary.The shapes, sizes and numbers of amorphous particulate substances stained by Amido Black 10B, called Amido Black active substances (ABAS), were determined under a microscope. The numbers of ABAS retained on Millipore HA filters (mean diameter: 10–80µm) amounted to 450ml–1 in the estuarine water about 6km from the mouth of the estuary (Station TA-12M). Some of these aggregates are considered to be producedin situ by flocculation of high molecular weight FPAS during estuarine mixing. ABAS were also produced in experiments by mixing filtered river water with sea water. 相似文献
18.
Diatom succession and silicon removal from freshwater in estuarine mixing zones: From experiment to modelling 总被引：1，自引：0，他引：1
Estuaries act as filters for land derived material reducing the river input to the coastal zone. Silicon (Si) removal from freshwater which is tightly linked to the growth of diatoms was studied in the estuarine mixing zone where the mixing of freshwater and seawater results in a salinity gradient. Three planktonic diatom species with different origin and salinity tolerance were grown in an artificial salinity gradient. Salinity stress and nutrient depletion led to a specific succession of the three diatoms along the salinity gradient. When available light was increased, diatoms reached higher biomass and the Si removal from water column was more efficient along the mixing. From this experiment, a conceptual model of Si transformations and removal from freshwater was build and applied to an idealized stratified estuary. Sensitivity analysis with varying initial conditions and parameter values pointed transit time of freshwater in the estuary, freshwater and seawater mixing rate and river turbidity as important interactive factors influencing Si removal from freshwater. Other factors like the total amount and the salinity tolerance of diatoms in the upstream river were shown to significantly affect riverine Si removal from the surface layer of an estuary. Finally it appears that Si removal from freshwater in estuarine mixing zones proceeds in two ways: a first rapid death and sedimentation of planktonic stenohaline diatoms imported from the river and second, the growth and subsequent settling of planktonic euryhaline diatoms of either freshwater or marine origin. 相似文献
19.
