The influence of salinity on the solubility of Zn and Cd sulphides in the Scheldt estuary   总被引：2，自引：0，他引：2  

L. J. A. Gerringa  H. J. W. de Baar  R. F. Nolting  H. Paucot 《Journal of Sea Research》2001,46(3-4)

In the estuary of the river Scheldt, where an oxygen gradient exists in addition to the salinity gradient, redox processes will be of major importance for trace metal mobilisation. In this study, the influence of salinity and pH on the redox processes of dissolved Zn and Cd sulphides is investigated together with the effects on the ratio of the dissolved Zn and Cd concentrations. The speciation of these metals is calculated with the chemical equilibrium programme +. Zn sulphides are oxidised at lower oxygen concentrations than Cd sulphides, due to lower stability constants, causing a sudden increase or peak in the dissolved Zn/Cd ratio. The formation of dissolved Cd chloride complexes when oxidation occurs at high salinities (S=15) increases the mobility of Cd, causing a decrease in the Zn/Cd peak of the total dissolved concentrations. The peak is three to four times smaller at S=15 than when oxidation occurs at S=2. The simple model calculations compare very well with field data. The Scheldt estuary is suitable to illustrate these calculations. In the 1970s, the anoxic part of the estuary reached S=15–20, but since the early 1980s it has dropped to S=2–10. Historic data on metals in the estuary from 1978, 1987 and the 1990s were used to compare with the equilibrium calculations. The increase of the dissolved Zn/Cd peak at low salinity as a consequence, of the decreasing anoxic region is confirmed well by the data. The good agreement between model calculations and field data is a proof of the extreme importance of redox processes for the solubility of Zn and Cd sulphides in the estuary.  相似文献   

Bioenhancement of cadmium transfer along a multi-level food chain     

Seebaugh DR  Goto D  Wallace WG 《Marine environmental research》2005,59(5):77-491

Previous studies have shown that metal partitioned to a subcellular compartment containing trophically available metal (TAM) is readily available to predators and may be enhanced by increased binding of metal to heat-stable proteins (HSP - e.g., metallothioneins). The aim of the current investigation was to determine the influence of TAM on the trophic transfer of Cd along an experimental, three-level food chain: Artemia franciscana (brine shrimp)-->Palaemonetes pugio (grass shrimp)-->Fundulus heteroclitus (mummichog). P. pugio were fed for 7 days on A. franciscana exposed to Cd in solution (including (109)Cd as radiotracer) and subjected to subcellular fractionation or fed to F. heteroclitus. An HSP-driven increase in the percentage of Cd associated with TAM (TAM-Cd%) in A. franciscana exposed to 1 muM Cd resulted in a bioenhancement (i.e., a greater than linear increase with respect to A. franciscana exposure) of Cd trophic transfer to P. pugio. Increased dietary Cd exposure did not affect TAM-Cd% in P. pugio nor trophic transfer to F. heteroclitus.  相似文献   

A surface complexation model for cadmium and lead adsorption onto diatom surface     

A. Glabert  O.S. Pokrovsky  C. Reguant  J. Schott  A. Boudou 《Journal of Geochemical Exploration》2006,88(1-3):110

This work is devoted to the physico-chemical study of cadmium and lead interaction with diatom–water interfaces for two marine planktonic (Thalassiosira weissflogii = TW, Skeletonema costatum = SC) and two freshwater periphytic species (Achnanthidium minutissimum = AMIN, Navicula minima = NMIN) by combining adsorption measurements with surface complexation modeling. Reversible adsorption experiments were performed at 20 °C after 3 h of exposure as a function of pH, metal concentration in solution, and ionic strength. While the shape of pH-dependent adsorption edge is similar among all four diatom species, the constant-pH adsorption isotherm and maximal binding capacities differ. These observations allowed us to construct a surface complexation model for cadmium and lead binding by diatom surfaces that postulates the constant capacitance of the electric double layer and considers Cd and Pb complexation with mainly carboxylic and, partially, silanol groups. Parameters of this model are in agreement with previous acid–base titration results and allow quantitative reproduction of all adsorption experiments.  相似文献   

石墨炉原子吸收分光光度法测定土壤样品中痕量镉   总被引：2，自引：0，他引：2  

董丽  沈谷苗 《江苏地质》2004,28(1):42-44

研究了土壤样品中痕量镉的石墨炉原子吸收分光光度法测定最佳条件以及磷酸二氢铵与硝酸镁作基体改进剂对测定镉的基体改进效应，并比较了两种试样分解体系。方法检出限为0.01pg／L，精密度(RSD，n=8)为3．29％-7．69％，经国家一级标准物质分析验证，结果与标准值符合。  相似文献   

Fate of copper and cadmium in a sediment-water system,and effect on chitin degrading bacteria     

H. Neumann-Hensel  W. Ahlf 《洁净——土壤、空气、水》1995,23(2):72-75

Fate and effect of copper and cadmium on the degradation of chitin were studied in sediment microcosms. Artificial sediment was spiked with metals, and metal partitioning between sediment components, overlying water and bacteria was described. Most of the added metals were bound to sediment particles. Remarkable metal enrichments were found on Fe-oxide, Mn-oxide, and chitin. In sediments containing the nominal concentration of 100 mg/kg Cu, the chitin-degrading bacteria Cytophaga johnsonae showed a significant decrease in N-acetylglucoseaminidase activity. Toxicity of copper was attributed to free ions in the overlying water. The bacteria were more sensitive to copper than to cadmium. Inhibitory effects of cadmium were primarily caused by sediment-associated cadmium.  相似文献   

Two Experimental Methods to Determine the Speciation of Cadmium in Sediment from the River Neckar     

N. Martin  I. Schuster  St. Peiffer 《洁净——土壤、空气、水》1996,24(2):68-76

The binding forms of Cd to an anaerobic sediment of low sulfide content from Lauffen reservoir (River Neckar, Germany) were studied using two different approaches, i. e. sequential extraction (modified from published protocols) and titrimetric study of the pH-dependent Cd release. Thermodynamic equilibrium calculations were applied to calculate both the release pattern of Cd during the titrations and the speciation of Cd within the single fractions of the extraction protocol. The calculations were based on measured sediment parameters such as hydrous ferric oxide (HFO), acid volatile sulfide, carbonate content and total Cd content, and the extractants (oxalate, acid etc.) used. The results of the two independent approaches coincided well in that they both assigned more than two thirds of the total Cd content to be adsorbed to organic matter. Cd bound as CdS is of little importance. Sequential extraction after a 3-month oxidation period at pH 7 revealed a shift of Cd from being mainly bound in stronger surface complexes with organic matter to being mainly bound in weaker surface complexes with organic matter and HFO, and thus becoming more bioavailable. This study suggests that the use of sequential extraction although being frequently criticized due to its operational character can be used to determine binding forms of metal ions if they are accompanied by 1) careful supporting experiments, 2) analysis of important sediment parameters, and 3) the use of thermodynamic equlibrium models which can help to understand Cd speciation within the extraction fractions.  相似文献   

Effects of Deicing-Salts on Heavy Metal Mobility Zum Einfluß von Streusalzen auf die Beweglichkeit von Schwermetallen     

B. Bauske  D. Goetz 《洁净——土壤、空气、水》1993,21(1):38-42

Heavy metal input into roadside soils and effects of deicing salts are often discussed as separate environmental problems. However, a relationship between salt input and heavy metal mobility has already been detected in laboratory tests. During a 2-year field study, the soil solution of a roadside soil was continuously sampled. The results of soil solution analysis not only showed a strong rise in deicing-salt related sodium, calcium and chloride concentrations, but also high zinc and cadmium values in winter and spring. Additional laboratory tests confirmed the mobilizing effects of salt solution which contained NaCl and CaCl₂. Cation exchange and the formation of chlorocomplexes are discussed as the responsible mechanisms.  相似文献   

The speciation of dissolved copper,cadmium and zinc in Manila Bay,Philippines     

Velasquez IB  Jacinto GS  Valera FS 《Marine pollution bulletin》2002,45(1-12):210-217

At present, there is a very limited information on the levels and distribution of dissolved metals in Manila Bay. In this study, the horizontal and vertical distribution of operationally defined species (labile, bound and total) of dissolved copper (Cu), cadmium (Cd) and zinc (Zn) were determined using differential pulse anodic and cathodic stripping voltammetry in water samples obtained from 18 stations in November 1998. In addition, the 24-h variability in the concentrations of these species at different depths in the water column was determined. These measurements were complemented by the determination of temperature, salinity, dissolved oxygen, chlorophyll a, particulate organic carbon and nutrients. Results showed that more than 50% of total dissolved copper and cadmium were labile while 50% of total dissolved zinc was organically bound. Vertical profiles showed that Cu, Cd and Zn concentrations were generally high at the surface. Zinc and cadmium were characterised by the presence of a mid-depth minimum while copper did not show any clear vertical trend.

Dissolved Cu concentrations during the spatial and diurnal samplings ranged from 0.32 to 6.95 nM and 1.52 to 45.65 nM, respectively. For Cd, the concentrations in 18 stations ranged from 0.05 to 2.92 nM, and from 0.03 to 2.42 nM over a 24-h period. Zn concentrations ranged from 2.48 to 147.43 nM and 2.87 to 88.27 nM during the spatial and diurnal samplings, respectively. The large variation in the concentration of Cu, Cd and Zn in the bay was observed to be associated with the presence of a large vertical density gradient in the water column, which appeared to limit the exchange of materials between the surface and bottom waters. Elevated levels of these metals near point sources suggest anthropogenic inputs in the bay.  相似文献   

The influence of diet on comparative trace metal cadmium,copper and zinc accumulation in Thais clavigera (Gastropoda: Muricidae) preying on intertidal barnacles or mussels     

Blackmore G  Morton B 《Marine pollution bulletin》2002,44(9):870-876

The influence of diet on comparative metal accumulation was investigated using a predatory muricid gastropod Thais clavigera. Individuals were fed for up to 56 days on either barnacles, i.e., Tetraclita squamosa, or mussels, i.e., Perna viridis, collected from metal-contaminated and clean sites. Barnacles and mussels have contrasting metal handling strategies and, therefore, different body concentrations, intracellular distributions and detoxification systems. Field collection of prey items that accumulated body metal concentrations over a lifetime of exposure allowed bioavailability to the predator, T. clavigera, to be assessed naturally, which may not be the case for prey exposed to metals for a short time in the laboratory. T. clavigera that was fed cadmium- and copper-contaminated barnacles or mussels ingested significantly greater amounts compared to those fed conspecifics collected from clean locations. T. clavigera body cadmium and copper concentrations were not, however, significantly different between individuals fed either contaminated or clean prey. Amount of zinc ingested was similar in mussels collected from clean and contaminated environments but much less when compared to the barnacle prey. The body concentrations of zinc in T. clavigera fed mussels collected from both sites fell. In contrast, the amount of zinc ingested from barnacle prey was significantly greater from those collected from the metal-contaminated site as compared to the clean one. This was reflected as significantly greater body zinc concentrations in T. clavigera fed contaminated barnacles compared to those fed clean individuals. Copper and zinc accumulation from prey was, therefore, complex. It varied between metal and between prey type, but appeared to be related to the amount ingested and the metal handling strategy of the prey.  相似文献   

The use of transplanted cultured tropical oysters (Saccostrea commercialis) to monitor Cd levels in North Queensland coastal waters (Australia)     

Olivier F  Ridd M  Klumpp D 《Marine pollution bulletin》2002,44(10):1051-1062

Bivalves are commonly used to detect metal pollution in the marine environment. Commercially cultured Milky oysters (Saccostrea commercialis) were transplanted in various sites along the North Queensland coast and analyzed for two metals of potentially anthropogenic origin (Cd, Zn). To provide additional information, naturally occurring Black Lip oysters (Saccostrea echinata) were also collected at the transplantation sites. The study demonstrated that the oysters species transplanted are good bioindicators of these metal concentrations in tropical waters, sensitive to variations in the environment at concentrations which are much smaller than pollution signals commonly reported for temperate waters. Three transplant experiments were carried out from May 1999 to February 2000. Milky oysters transplanted to offshore areas (Orpheus Is., Kelso Reef) accumulated Cd in the soft parts whereas oysters sampled from cages placed in Ross Creek and the Herbert River estuaries showed a decrease in Cd concentration, which resulted from an increase in dry weight. Dry weight appeared to be an important covariant affecting Cd concentration in the oysters whereas it does not unambiguously affect Zn concentrations. For the duration of the experiments, oysters sampled from the Magnetic Is. reference site showed effectively constant Cd concentrations and total Cd contents which indicates that any seasonal cycle affecting metal concentration is weak. It was found that Cd accumulation in oysters increased as ambient dissolved Cd concentration decreased, from which it was concluded that for these oysters, the predominant source of Cd was from the particulate phase rather than the dissolved phase.  相似文献