The behaviour of copper and zinc in the Scheldt estuary

The behaviour of copper and zinc in the Scheldt estuary, both in the particulate and the dissolved phase, is discussed for the period 1982–1983. The longitudinal particulate copper and zinc profiles fall below the dilution line, which is attributed to mixing and mobilization processes. In the dissolved phase both metals show a production region in the end member of the estuary, for copper a pronounced mid estuarine maximum is observed. Study of the metal speciation suggested that organic ligands might keep heavy metals in solution, especially in area of intensive production, and promote the subsequent export of these metals downstream the estuary.     

Toxicity of dissolved Cu, Zn, Ni and Cd to developing embryos of the blue mussel (Mytilus trossolus) and the protective effect of dissolved organic carbon

Marine water quality criteria for metals are largely driven by the extremely sensitive embryo-larval toxicity of Mytilus sp. Here we assess the toxicity of four dissolved metals (Cu, Zn, Ni, Cd) in the mussel Mytilus trossolus, at various salinity levels while also examining the modifying effects of dissolved organic carbon (DOC) on metal toxicity. In 48 h embryo development tests in natural seawater, measured EC50 values were 6.9-9.6 microg L(-1) (95% C.I.=5.5-10.8 microg L(-1)) for Cu, 99 microg L(-1) (86-101) for Zn, 150 microg L(-1) (73-156) for Ni, and 502 microg L(-1) (364-847) for Cd. A salinity threshold of >20 ppt (approximately 60% full strength seawater) was required for normal control development. Salinity in the 60-100% range did not alter Cu toxicity. Experimental addition of dissolved organic carbon (DOC) from three sources reduced Cu toxicity; for example the EC50 of embryos developing in seawater with 20 mg C L(-1) was 39 microg Cu L(-1) (35.2-47.2) a 4-fold increase in Cu EC50. The protective effects of DOC were influenced by their distinct physicochemical properties. Protection appears to be related to higher fulvic acid and lower humic acid content as operationally defined by fluorescence spectroscopy. The fact that DOC from freshwater sources provides protection against Cu toxicity in seawater suggests that extrapolation from freshwater toxicity testing may be possible for saltwater criteria development, including development of a saltwater Biotic Ligand Model for prediction of Cu toxicity.     

Suspended matter in the Scheldt estuary

The Scheldt estuary is characterised by a specific energy pattern resulting from the interaction of wave energy, tidal energy and river energy. It divides the estuary into three parts and governs suspended matter transport and distribution pattern. Observation of suspended matter transport shows the existence of three estuarine turbidity maxima (ETM), a marine-dominated ETM in the lower estuary at the river mouth, a river-dominated ETM in the upper estuary with suspended matter concentration reaching up to 300 mg/l, and the most important tide-dominated ETM in the middle estuary with suspended matter concentrations from several hundred milligrams per litre up to a few grams per litre. Resuspension is the dominant phenomenon in this last ETM due to the tidal related bottom scour, which is initiated when a critical erosion velocity of 0.56 m/s is exceeded. An assessment of residual current along the axis of the estuary shows distinctive pattern between the surface water flow and the near bottom water flow. Also the local morphology of the river, natural or man-made, has a prominent effect on the orientation and strength of the residual currents flowing along either side of the river or river bend. Evaluation of suspended matter concentration in relation to the current flow shows no systematic correlation either because of phenomena as scour lag and settling lag mainly in the middle estuary, or because of the current independency character of uniform-suspension mainly in the upper and lower estuary. Quantification of suspended matter load exhibits a net downstream transport from the upper estuary, a near-equilibrium sustainable status in the middle estuary and a net upstream transport of suspended matter from the lower estuary. The characteristic of suspended matter is induced by and is a function of e.g. tidal phase, spring-neap tide, longitudinal and vertical distribution mechanisms, seasons, short and long terms of anthropogenic influence and/or estuarine maintenance. Suspended matter is dominated by complex and cohesive organo-mineral aggregates. It consists of a variable amount of an inorganic fraction (average of 89%) and an organic fraction and occurs largely as flocs, the size of which is remarkably larger in the upper estuary and smallest within the ETM in the middle estuary. Independent time series measurements (1990–2000) of suspended matter property show an increasing sand fraction, a decreasing organic matter content, a rise in ¹³C as well as a decrease in water transparency. These independent measurements exhibit coherent consequences of estuarine maintenance operations. Maintenance dredging of the shipping channel and harbours and dumping operation in the Scheldt strengthen marine influence further landward, resulting in a sustained tidal range increment and upstream flow and transport of suspended matter.     

Dynamics of dissolved and biogenic silica in the freshwater reaches of a macrotidal estuary (The Scheldt, Belgium)

Temporal evolution of dissolved and biogenic silica concentrations along the Scheldt tidal river and in its tributaries was investigated during 1 year in 2003. In the tributaries, dissolved silica (DSi) concentrations remained high and biogenic silica (BSi) concentrations were low throughout the year. In the tidal river during summer, DSi was completely consumed and BSi concentrations increased. Overall, most of the BSi was associated with living diatoms during the productive period in the tidal river. Nevertheless, the detrital BSi was a significant fraction of the total BSi pool, of which less than 10% could be attributed to phytoliths. The tidal river was divided into two zones for budgeting purposes. The highest productivity was observed in the zone that received the highest water discharge, as higher riverine DSi input fluxes induced presumably a less restrictive DSi limitation, but the discharge pattern could not explain all by itself the variations in DSi consumption. Silica uptake and retention in the tidal river were important at the seasonal time-scale: from May to September, 48% of the riverine DSi was consumed and 65% of the produced BSi was deposited, leading to a silica (DSi + BSi) retention in the tidal river of 30%. However, when annual fluxes were considered, DSi uptake in the tidal river amounted to 14% of the DSi inputs and only 6% of the riverine silica (DSi + BSi) was retained in the tidal river.     

Effects of organic amendments on Cd, Zn and Cu bioavailability in soil with repeated phytoremediation by Sedum plumbizincicola

Organic materials with different functional groups can be used to enhance metal bioavailability. Traditional organic materials (rice straw and clover) and ethylenediamine disuccinic acid (EDDS) were applied to enhance metal uptake from polluted soil by Sedum plumbizincicola after repeated phytoextraction. Changes in pH, dissolved organic carbon (DOC) and metal concentrations were determined in the soil solution after EDDS application. Amendment of the soil with ground rice straw or ground clove resulted in higher concentrations of Cd only (by factors of 1.92 and 1.71 respectively) in S. plumbizincicola compared to control soil. Treatment with 3 mmol kg(-1) EDDS increased all the metals studied by factors of 60.4, 1.67, and 0.27 for Cu, Cd, and Zn, respectively. EDDS significantly increased soil solution DOC and pH and increased soil plant-available metals above the amounts that the plants could take up, resulting in high soil concentrations of soluble metals and high risk of ground water contamination. After repeated phytoremediation of metal contaminated soils the efficiency of metal removal declines as the concentrations of bioavailable metal fractions decline. Traditional organic materials can therefore be much more effective and environmentally friendly amendments than EDDS in enhancing phytoremediation efficiency of Cd contaminated soil     

Seasonal variation of floc characteristics on tidal flats, the Scheldt estuary

The flocculation mechanism dominates the fate of suspended matter in the estuarine environment. By modifying the texture of suspended matter, flocculation is one of the principle factors determining the transport and deposition of suspended matter in estuaries. Surveys of the seasonal variation of dispersed particle and non-dispersed particle characteristics, organic matter content as well as suspended matter deposition in two contrasting intertidal environments, one freshwater and one brackish water, in the Scheldt estuary were undertaken at fortnightly intervals for a year. The study of non-dispersed particle, i.e. floc, is mainly focused on floc size, shape, and microstructure, properties presumed to be significant in the suspended matter transport processes in the estuary. In this study, floc size as well as floc sphericity correlate positively with the change of organic matter content and reveal that floc grows in a three-dimensional way with increasing organic matter. It is observed that relatively condensed, small and elongated flocs appear in winter and spring periods, while loose, large and spherical flocs occur during the summer. The study also reveals that suspended matter transported as dense flocs with size range of ca. 105–250 m have a greater effect on its short-term deposition than loose flocs with size range of ca. 250–500 m. As the measured suspended matter deposition is much higher in winter–spring than in summer, it is deduced here that highly compact and relatively dense flocs contribute to deposition during winter and spring periods resulting in a stable layer, while loosely formed flocs likely lead to an easier erodible layer during the summer. This study concludes that floc structure-related density is a more significant parameter than floc size in the suspended matter deposition processes.     

Serum levels of Cd, Pb, Cu and Zn in cigarette smokers

In order to show the accumulation of Cd, Pb, Cu and Zn in smokers, levels of these metals in serum were determined in 108 subjects: 32 non-smokers, 37 average cigarette smokers and 39 heavy cigarette smokers. The analysis was carried out by potentiometric stripping analysis (PSA) with the Tecator "Striptec System". Backward oxidation time of the amalgamated metals, by means of electrolysis, in a thin "film" of mercury in an electrode, gives their concentration measure. Our data showed an increase in average values of Cd and Pb in the serum of heavy smokers compared with average and non-smokers. Instead, as regards Cu and Zn, no differences were found in the two groups of smokers compared with the non-smokers used as controls. Results obtained of the Cd and Pb levels in serum are compatible with the presence of these metals in cigarette tobacco and inhaling them could contribute to disease connected with their accumulation in the human organism. For these subjects the increase in Cd values is of particular importance as it could predispose pulmonary emphysema.     

根瘤菌对土壤铜、锌和镉形态分配的影响

以湖南郴州红壤和河北巩义褐土为供试土壤。制备Cu、Zn、Cd污染土壤。接种大豆根瘤菌(Rhi-zobium fredii)HN01,用连续提取法浸提土壤中不同形态的重金属．结果表明。褐土接种根瘤菌后固相结合态Zn总量降低10％。专性吸附态、氧化锰结合态和有机结合态Zn减少达9％～26％．红壤中结合态Zn的总量变化不显著,但专性吸附态和氧化锰结合态Zn含量显著减少。交换态Zn含量显著增加．褐土中接种根瘤菌抑制了Cu向土壤溶液的释放,固相结合态Cu总量增加18％,可交换态、专性吸附态、氧化锰结合态和有机结合态的Cu增加20％～54％．接种根瘤菌对土壤中Cd的溶解没有明显的抑制或促进作用,但改变了红壤中各形态Cd的含量高低顺序．Cd污染红壤中可交换态和有机结合态Cd含量分别增加22％和11％,专性吸附态和氧化锰结合态Cd分别减少14％和29％．根瘤菌对不同类型重金属及不同土壤中重金属形态影响的差异主要与土壤pH降低有关．     

菌根植物根际环境对污染土壤中Cu、Zn、Pb、Cd形态的影响

采用根垫法和连续形态分析技术,分析了生长在污灌土壤中菌根小麦和无菌根小麦根际Ｃｕ、Ｚｎ、Ｐｂ、Ｃｄ的形态分布和变化趋势。结果表明,下对照土壤相比,菌根际土壤中交换态Ｃｕ含量显著增加,交换态Ｃｄ呈减少的趋势;与非菌根际相比,Ｃｕ、Ｚｎ、Ｐｂ的有机结合态在菌根根际中显著增加,而４种测定金属２的碳酸盐态和铁锰氧化态都没有显著改变,该结果表明,植物根系能影响根际中金属形态的变化,且菌根比无菌根的影响程度大     

Effects of Cu,Cd and Zn on photosynthesis of freshwater benthic algae

One hundred and eighteen algal isolates comprising seven classes were obtained from a range of sites from polluted rivers running through Cu or Zn mining regions, and from unpolluted rivers. All the isolates were tested for photosynthetic activity when exposed to Cu, Cd or Zn. The tolerance levels of Bacillariophyceae, Charophyceae, Cyanophyceae and Chlorophyceae to Cu showed significant positive correlations with Cu concentrations in the field. However the distribution of metal sensitivities of the algae from the sites with the same metal concentration was broad. Both Bacillariophyceae and Charophyceae had a number of strains whose sensitivity to Cu differed more widely in relation to Cu levels in the environment than Cyanophyceae and Chlorophyceae. Cyanophyceae were sensitive to all three metals, whether or not isolates were obtained from polluted sites, whereas Chlorophyceae tended to have high tolerance even in isolates from unpolluted sites. For Cd and Zn the correlation between tolerance levels and concentrations in the field was not so clear as for Cu. The occurrence of Cu tolerance was shown in 4 diatom species and one Charophyceae, whereas metal resistance occurred in some Chlorophyceae. Cu-tolerant isolates tended also to be Zn-tolerant in Bacillariophyceae, and Cd-resistant isolates tended also to be Zn-resistant in Chlorophyceae.     

Litter accumulation in woodlands contaminated by Pb,Zn, Cd and Cu

Summary Close to a primary lead-zinc-cadmium smelter the standing crop of litter in woodlands was found to be elevated relative to more distant sites. The total litter accumulation is similar to that from contaminated sites reported by other authors but in this case the concentrations of heavy metals are considerably lower than those reported for other sites. Evidence is provided to support the hypothesis that within the woodlands studied, litter accumulation is not closely pH dependent, but is clearly related to both cadmium and zinc concentrations in litter. Litter accumulation occurs in certain particle size ranges and fractionation shows that the weight of accumulated litter in these size ranges is highly correlated to cadmium concentrations. These results are discussed in relation to the reported possible long term effects of metal contamination on decomposition processes and the possibility of adaptation to these adverse effects.     

The environmental risks of pollution in the Scheldt estuary

The ecotoxicological effects of pollution in the Scheldt estuary is evaluated for several routes of exposure by comparing observed concentrations of micro-contaminants in water and tissues of biota with toxicity data in literature. Ecological risks are estimated for dissolved trace metals according to the method of VAN STRAALEN (1990) using published data on NOECs from aquatic toxicity tests concerning reproduction, mortality and growth for cold blooded marine and estuarine organisms. Of eight investigated trace metals, zinc and nickel cause the highest risks, both affecting up to 4% of the aquatic species. The occurrence of bioaccumulation of PCBs and cadmium is investigated in several trophic levels. High concentrations of PCBs are observed in tissues of biota and may indicate adverse effects on top predators (seals, terns), especially in the brackish zone. Environmental risks of other organic micro-contaminants have not been indicated due to the limited number of data on toxicity or environmental concentrations. The effects of a mixture of pollutants in sediments from the Scheldt estuary were investigated with an oyster larvae bioassay showing an increased toxicity in upstream direction. Moreover, in the upper part of the estuary, preconditions regarding the oxygen concentration are not met and overshadow the toxic effects of pollution with micro-contaminants. Especially in the less contaminated part of the estuary more ecotoxicolgical research is required to perform an integral risk evaluation. At present, still little is known about effects that may occur in the field.     

Modelling of water and sediment quality in the Scheldt estuary

In 1987 the Tidal Waters Division (Ministry of Transport, Public Works and Water Management, The Netherlands) initiated the SAWES project (Systems Analysis WEstern Scheldt). In the framework of this project, a water quality model for the Scheldt estuary was made. The model aims to establish the relation between pollution inputs and the concentration of pollutants in the abiotic compartments and to establish the fate of wasted substances. The model includes oxygen, nitrogen and trace metals. Due to the low oxygen content of the upper Scheldt estuary, a new model approach for trace metals had to be developed, taking into account precipitated metal sulphides. The calibration, verification and sensitivity analysis of the model provided a good understanding of the chemistry of the estuary. Afterwards the model was used to support policy making by computing how the water and sediment quality in the estuary respond to reduced inputs of waste.     

Water quality modelling of the western Scheldt estuary

In 1987 the National Institute for Coastal and Marine Management (theNetherlands) initiated the SAWES project (Systems Analysis WEstern Scheldt).The main goals of the project were to acquire knowledge with respect to thepollution problems in the Scheldt estuary and to apply this knowledge tomanagement issues of the Scheldt on an operational level. The main interestwas to understand quantitatively the relation between inputs of pollutingsubstances and effects on the ecosystem. In the framework of the project, awater quality model for the Scheldt estuary was made. In 1995, the modelarea was expanded to include the Belgian coastal region at the mouth of theestuary. The model calculates the fate of discharged substances andestablishes the relation between pollution inputs and the resulting waterquality, including general water quality (oxygen, pH, alkalinity, major ionchemistry and nutrients) as well as pollutant concentrations. The modelincorporates all chemical processes which affect these concentrations,including the precipitation/dissolution of metal sulphides which to a largeextent controls the fate of trace metals. Based on calibration andverification exercises, it has been shown that the model provides a goodrepresentation of the physical and chemical processes taking place withinthe estuary and can therefore be used to support policy development for theestuary. For example, the model can compute how the water and sedimentquality in the estuary will respond to reduced inputs of waste or to suchhuman activities as dredging. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Effect of Electrolyte Type and Concentration on the Release of Cd,Cu, Ni,and Zn in Some Contaminated Calcareous Soils

This paper reports the results of desorption experiments of cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) from some contaminated calcareous soils under four electrolyte types (CaCl₂, MgCl₂, NaCl and Na₂SO₄) with different electrolyte concentrations (0.5, 4 and 10 mM). Among electrolytes, CaCl₂ significantly released more metals from soils. There was a negative relationship between total Cu and Zn content and percentage of Cu and Zn released (average of electrolyte concentrations) using CaCl₂ solution, indicating a higher Cu and Zn released when their total content was low. Generally, Cd, Cu, and Zn speciation was affected by both type of electrolytes and their concentrations, whereas Ni speciation stayed mostly stable and was almost unaffected by applied solutions. It can be suggested that beside competition with cations, chloro-complexation is important parameter in Cd release, while CuOH⁺, and to some extent ZnOH⁺ are important species affecting release of Cu and Zn. The distribution coefficient (K_d) values for each metals greatly varied with the types of electrolytes and electrolyte concentration. On the basis of average percentage of metal released under different electrolytes and concentrations the following sequences was found: Cd > Cu > Ni > Zn. The results are important in understanding the mobility of metals under different solutions and indicating that, Cd and Zn soils may pose a higher and lower mobility and ecological risk in contaminated calcareous soils, respectively.     

Photooxidation of wetland and riverine dissolved organic matter: altered copper complexation and organic composition

In natural waters, the uptake of transition metals such as copper (Cu) by aquatic biota depends on the activity of the free cupric ion ({Cu²⁺}) rather than on total Cu concentration. Thus, an important ecological function of dissolved organic matter (DOM) in aquatic ecosystems is Cu–DOM complexation, which greatly decreases the {Cu²⁺}. However, Cu bioavailability is greatly modified by source and environmental history of DOM because DOM affinity for Cu varies by orders of magnitude among DOM sources; moreover, DOM is photochemically unstable. During 72-h irradiation experiments at intensities approximating sunlight with DOM from a palustrine wetland and a third-order river, we investigated photooxidative effects on DOM complexation of Cu as well as spectral and chemical changes in DOM that might explain altered Cu complexation. Irradiation decreased Cu complexation by riverine DOM, but unexpectedly increased Cu complexation by wetland DOM, resulting in 150% greater {Cu²⁺} in riverine DOM at the same dissolved organic carbon concentrations. The specific ultraviolet absorption (SUVa) and humic substances tracked photochemical changes in the conditional stability constants of Cu–DOM complexes, suggesting that the aromaticity of DOM influences its affinity for Cu. Carbonyl concentration in ¹³C nuclear magnetic resonance spectra (¹³C-NMR) covaried directly with Cu binding-site densities in DOM. However, no aspect of Cu–DOM complexation consistently covaried with fluorophores (i.e., the fluorescence index) or low molecular weight organic acids. Our results suggest that global increases in UV radiation will affect Cu–DOM complexation and subsequent Cu toxicity depending on light regime as well as DOM source. Handling editor: K. Martens     

重金属Cd、Zn、Cu、Pb对土壤微生物和酶活性的影响

采用室内培养实验(25℃),研究了不同培养时间下重金属Cd、Zn、Cu、Pb(浓度分别为50,800,400,800mg.kg-1)污染对土壤微生物和酶活性的影响。结果表明,土壤蔗糖酶、过氧化氢酶和脱氢酶活性随着培养时间的增加而显著下降,在培养20d的时候达到最小值,然后酶活性缓慢升高。Cu对脲酶活性以及Cd对酸性磷酸酶和脲酶活性的抑制作用随时间增加而增加。土壤微生物生物量碳、细菌、真菌和放线菌数量随培养时间的增加均表现出先降低后升高的变化趋势。Cd和Cu对微生物生物量氮的抑制作用则随着培养时间的增加而增强,在培养30d时微生物生物量氮到达最低值,分别较培养10天减少了12.6%和16.5%。     

The action of Cd, Cu, Cr, Zn, and Pb on fluid composition of Anodonta cygnea (L.): organic components

The heavy metals, Cd, Cu, Cr, Zn, and Pb, were used to incubate healthy specimens of the freshwater mussel species, Anodonta cygnea. Afterwards, their biological fluids, either haemolymph or extrapallial fluid were analyzed for the presence of several organic constituents, known to be important for biomineralization, such as proteins, glycosaminoglycans (GAGs) and glucosamine. Proteins were subjected to further study, namely through the total amino acid determination after acid hydrolysis. The most disturbing pollutants tested seem to be Pb, Zn, and Cr, which caused highly decreased overall compositions, namely with respect to protein, and glucosamine, in comparison to the control group. This suggests that this group contributes to a decrease of the metabolic activity, and thus mineralization, in the exposed animals.     

Separation and purification of (Cd, Cu, Zn)-metallothionein in carp hepato-pancreas

1. Cd-binding protein was isolated from the hepato-pancreas of carp administered CdCl2 (2 mg/kg). 2. This protein had a high absorption at 254 nm derived from Cd-mercaptide binding, and a low absorption at 280 nm derived from the absence of aromatic amino acids; the authors recognized the presence of two types. 3. The amino acid composition of the proteins was determined. The contents of cysteine residues were 34.24% and 31.90% in MT-I and -II respectively. Tyrosine, phenylalanine, tryptophan, histidine, leucine and arginine residues were absent in both types.