Leaching of Zinc,Cadmium, and Lead in a Sandy Soil Due to Application of Poultry Litter

Dissolved organic matter in poultry litter could contribute organic ligands to form complexes with heavy metals in soil. The soluble complexes with heavy metals can be transported downward and possibly deteriorate groundwater quality. To better understand metal mobilization by soluble organic ligands in poultry litter, soil columns were employed to investigate the movement of zinc (Zn), cadmium (Cd), and lead (Pb). Uncontaminated soil was amended with Zn, Cd, and Pb at rates of 400, 8, and 200 mg kg ^{? 1} soil, respectively. Glass tubes, 4.9-cm-diameter and 40-cm-long, were packed with either natural or metal-amended soil. The resulting 20-cm-long column of soils had bulk density of about 1.58 g cm ^{? 3} . Columns repacked with natural or amended soil were leached with distilled water, 0.01 M EDTA, 0.01 M CaCl ₂ , or poultry litter extract (PLE) solutions. Low amounts of Zn, Cd, and Pb were leached from natural soil with the solutions. Leaching of Zn, Cd, or Pb was negligible with distilled water. In the metal-amended soil, EDTA solubilized more Zn, Cd, and Pb than CaCl ₂ and PLE. The breakthrough curves of Zn and Pb in the PLE and CaCl ₂ were similar, indicating they have similar ability to displace Zn and Pb from soils. Compared with Zn and Cd the PLE had a small ability to solubilize Pb from metal-amended soil. Thus, the application of poultry litter on metal-contaminated soils might enhance the mobility of Zn and Cd.     

Manure Application and Cannabis Cultivation Influence on Speciation of Lead and Cadmium by Selective Sequential Extraction

The contamination of agricultural soils by heavy metals is a worldwide problem. Degradation of organic matter (OM) from organic amendments used in the remediation of metal-contaminated soils leads to changes in soil chemical properties shortly after their addition, which may affect the soil metal distribution. The effects of four differing organic amendments on chemical forms of Pb and Cd in a contaminated soil were investigated in a pot experiment of control unamended soil and soils amended with dry cow and poultry manures (20 g CM or PM kg^?1 soil), and cow and poultry manure extracts (2 g CME or PME kg^?1 soil) cultured with cannabis sativa. After eight weeks, a sequential extraction scheme was used to fractionate soil Pb and Cd into soluble-exchangeable (Sol-Exch), organic matter associated (AOM), and carbonates associated (ACar) forms. The addition of animal manures and their extracts increased the DTPA-extractable Pb and Cd in soil significantly. Soil Pb and Cd in Sol-Exch fraction were increased by manure applications. Both Pb and Cd in AOM fraction were increased by application of manures and their extracts. This increase was more obvious for Pb in application of cow and poultry manure extracts. The ACar chemical forms of Pb and Cd were also increased by application of manures and their extracts. The increases of Pb and Cd in Acar fraction was noticeable in soils treated with cow manure. Soil cultivation with cannabis sativa increased available, Sol-Exch, and AOM chemical forms of Pb in soil significantly compared to control soil. However, soil Pb and Cd in ACar fraction were decreased significantly by cannabis cultivation. The effect of cannabis cultivation on all of the Cd chemical forms (except on Sol-Exch) was similar to the results of Pb chemical forms. Plant cultivation had no significant effect on Cd in Sol-Exch chemical form.     

Cadmium speciation studies in the intestine of Lumbricus terrestris by electrophoresis of metal proteins complexes

Cadmium speciation of the intestinal compartment of the earthworm species, Lumbricus terrestris, has been investigated using polyacrylamide gel electrophoresis under non-denaturing conditions. Worms exposed to Cd(NO₃)₂ supplemented soils have been studied and compared to control samples. Prior to electrophoresis, the worm intestines were removed and dissected. Proteins in the crude intestinal extracts were separated using polyacrylamide gel electrophoresis. The cadmium distribution in the proteins has also been described. In a second set of experiments, cadmium bound to proteins was first isotopically exchanged with labelled cadmium (¹⁰⁹Cd) and then cadmium speciation was performed using gel electrophoresis. Autoradiography of this gel shows an intense band in the contaminated sample whereas this band was absent in the control sample. These results show that one type of major protein has a strong affinity for cadmium in the worm intestinal extract. This type of protein had a migration close of that of rabbit liver metallothionein used for comparison.     

Cadmium mobilisation and plant availability – the impact of organic acids commonly exuded from roots

The present work highlights metal-organic acid interactions with special reference to their plant availability. Pot experiments were conducted to investigate the effect of various organic (carboxylic and amino) acids on the uptake and translocation of root-absorbed Cd by maize (Zea mays) plants grown in sand and soil culture. Statistically significant increases in Cd accumulation from Cd-treated plants in the presence of increasing concentrations of organic acids, suggest the existence of Cd-organic acid interactions in the soil-plant system. In order to support the above hypothesis of formation of organically bound Cd, separate experiments were performed to synthesize and estimate its various forms viz. cationic, anionic and neutral. The chemical nature of the organically bound forms was ascertained by electrophoretic experiments. Amino acids have been found to be less effective in the mobilisation of cadmium compared to carboxylic acids. The results are discussed on the basis of the potential of organic acids to form complexes with Cd.     

Solubility and mobility of copper,zinc and lead in acidic environments

Understanding the chemical speciation of metals in solution is necessary for evaluating their toxicity and mobility in soils. Soil samples from the Powder River Basin, Wyoming were extracted with distilled deionised H₂O. Soil water extracts were subjected to chemical speciation to determine the relative distribution and chemical forms of copper (Cu), zinc (Zn) and lead (Pb) in acidic environments. As pyrite oxidised, the pH decreased from 6.6 to 2.4, concentration of dissolved sulfate (S_T) increased from 259 to 4,388 mg L^-1 and concentration of dissolved organic carbon (DOC) decreased from 56.9 to 14.4 mg L^-1. Dissolved Cu concentrations ranged from 0.06 to 0.42 mg L^-1 and dissolved Zn concentrations ranged from 0.084 to 4.60 mg L^-1. Dissolved concentrations of Pb were found to be 0.003 to 0.046 mg L^-1. Chemical speciation indicated that at near neutral pH, dissolved metal concentration in soil water extracts was dominated by DOC- metal complexes. At low pH, dissolved metal concentration in soil water extracts was dominated by free ionic forms (e.g. Cu²⁺, Zn²⁺, Pb²⁺) followed by ion pairs (e.g. CuSO₄ ⁰, ZnSO _inf4 ^sup0 , PbSO _in4 ^sup0 ). Results obtained in this study suggest that as soil pH decreased, the availability and mobility of metal ions increased due to the chemical form in which these metal ions are present in soil solutions.     

Cadmium: tissue distribution and binding protein induction in the painted turtle, Chrysemys picta

The freshwater painted turtle, Chrysemys picta, was used to investigate (a) the distribution of an injected dose of ¹⁰⁹Cd in tissues over a period of 192 h (8 days) and (b) the effect of non-isotopic cadmium injection on tissue metal-binding protein levels. Cadmium is cleared from the blood with 9% remaining in the circulation at 192 h. ¹⁰⁹Cd is found in all tissues, but is accumulated preferentially in liver, kidney, pancreas, and gastrointestinal tract. The liver is the primary site of Cd accumulation, accounting for 46.4% of the injected dose by 192 h and the highest Cd concentration (cpm/mg tissue). Steroidogenic tissues and the oviduct accumulate significant amounts of ¹⁰⁹Cd and the isotope is present in yolk. An increase in tissue metal-binding protein level after non-isotopic CdCl₂ injection is consistent with ¹⁰⁹Cd distribution, in that metal-binding protein concentration after CdCl₂ injection is highest in liver, followed by pancreas and kidney with low, but with significant levels of cadmium-binding protein in gonads and steroid target organs. We conclude that the liver is the major site of storage after a single injection of isotopic cadmium and induction of a metal-binding protein may be an adaptive response to exposure to cadmium.     

Inducible cadmium binding complexes of cabbage and tobacco

Cadmium complexes with apparent molecular weights of 10,000 were observed in aqueous extracts of Cd-treated cabbage (Brassica capitata L., cv. red danish) and tobacco (hybrid of Nicotiana glauca and N. langsdorffii) plants. The amount of complex (as Cd) recovered was found to be dependent on the concentration of the metal in the growth medium and the total time of exposure of plants to the metal. Induction of the complex at moderate levels of ¹¹²Cd exposure was monitored after labeling the complex with ¹⁰⁹Cd in vitro. The constitutive nature of the ligand of the complex in cabbage and tobacco leaves was suggested when control plant extracts were exposed to ¹⁰⁹Cd. Such extracts contained ¹⁰⁹Cd, which eluted from Sephadex G-50 in the region of Cd complex. Simultaneous labeling with ¹¹²Cd and ³⁵S or ³²P indicated that the complex contained sulfur but probably not phosphorus. The amount of ³⁵S which eluted coincident with ¹¹²Cd complex increased during complex induction. No evidence was found for the presence of 10,000 molecular weight Cd complex in stem exudates (vascular sap) of Cd-treated plants.     

Enhanced cadmium accumulation in maize roots—the impact of organic acids

Low molecular weight organic acids are important components of root exudates and therefore, knowledge regarding the mechanisms of cadmium (Cd) uptake and distribution within plants under the influence of organic acids, is necessary for a better understanding of Cd behavior in the plant–soil system. In this study, acetic and malic acids increased the uptake of Cd by maize (Zea mays L. cv. TY2) roots and enhanced Cd accumulation in shoots under hydroponic conditions. Concentration-dependent net Cd influx in the presence and absence of organic acids could be resolved into linear and saturable components. The saturable component followed Michaelis–Menten kinetics, which indicated that Cd uptake across the plasma membrane was transporter-mediated. While the K _m values were similar, the V _max values in the presence of acetic and malic acids were respectively 6.0 and 3.0 times that of the control. Zinc transporters were the most probable pathways for Cd accumulation. It was hypothesized that Cd(II)–organic acid complexes associated with the root zone, could decompose and liberate Cd²⁺ for subsequent absorption by maize roots; and that in the layer of the roots or within the root free space, depletion of Cd²⁺ was buffered by the presence of Cd(II)–organic acid complexes. Plant response to elevated Cd levels involved overproduction of organic acids in maize roots as a resistance mechanism to alleviate Cd toxicity.     

Metal Complexation in Xylem Fluid : III. ELECTROPHORETIC EVIDENCE

The capacity of ligands in xylem fluid to form metal complexes was tested with a series of in vitro experiments using paper electrophoresis and radiographs. The xylem fluid was collected hourly for 8 hours from soybean (Glycine max L. Merr.) and tomato (Lycopersicon esculentum Mill.) plants grown in normal and Zn-phytotoxic nutrient solutions. Metal complexation was assayed by anodic or reduced cathodic movement of radionuclides (⁶³Ni, ⁶⁵Zn, ¹⁰⁹Cd, ⁵⁴Mn) that were presumed to have formed negatively charged complexes.     

The influence of pH and chloride on the retention of cadmium,lead, mercury,and zinc by soils

The extent of contamination of soils by toxic heavy metals not only depends on the rate of loading of the metal but also on the nature of the adsorbing surfaces, the degree of alkalinity or acidity of the soil and the presence of aqueous complexant ligands. This work reports on the role of pH on the retention of Cd, Hg, Pb and Zn by two soils and on the influence of the chloride, Cl‐, ion on the chemical speciation and retention of the four metals. Batch adsorption experiments were conducted from pH 3 to 7 in the presence of either 0.1 M LiCl or LiClO₄. The results of the study showed that high concentrations of Cl^‐ ions can greatly decrease the retention of Hg and have an increasingly lesser effect on Cd, Pb and Zn retention. The effect of the Cl^‐ons was directly related to the metal‐Cl formation constants. The results of computer modeling of Cd and Hg retention by goethite and humic acid fractions indicated the relative importance of aqueous vs. surface complexation on metal retention. For organic surfaces, which do not form ternary surface complexes, the presence of aqueous complexant ligands should always decrease the adsorption of the metal. For mineral surfaces, which do form ternary surface complexes, there may be increased or decreased metal retention depending on the formation constant of the aqueous metal‐ligand species, the intrinsic complexation constants for the various binary and ternary complexes of the metal and the concentration of the complexant ligand. Thus for Hg, which forms very strong aqueous species with Cl^‐ ions, reduced adsorption on goethite was predicted in the presence of 0.1 M LiCl, while enhanced adsorption was predicted for Cd and Pb. The results suggest caution in the disposal of Cl‐containing wastes onto metal‐contaminated soils. The deleterious effects of Cl^‐ ion addition would be greatest for soils with relatively high organic matter contents and low contents of hydrous ferric oxides.     

Subcellular distribution,chemical forms and thiol synthesis involved in cadmium tolerance and detoxification in Siegesbeckia orientalis L.

Siegesbeckia orientalis L. is a promising species for cadmium (Cd) phytoextraction with large biomass and fast growth rate, while little information about their intracellular mechanisms involved in Cd tolerance and detoxification has been explored. A soil pot experiment with total target Cd concentrations of 0, 10, 50, 100, and 150 mg kg^?1 were designed to investigate the subcellular distribution, chemical forms and thiol synthesis characteristics of Cd in S. orientalis. More than 90% of Cd was bound to the soluble fractions (48.4–76.5%) and cell walls (19.9–46.3%). Increasing soil Cd concentrations enhanced Cd sequestration into the cell walls. Most of the Cd (69.8–82.7%) in the plant organ was mainly in the forms of pectate and protein integrated Cd and undissolved Cd phosphate, while a minor portion (6.8–20.9%) was in the forms of the inorganic Cd and the water soluble Cd. Nonprotein thiols and phytochelatins significantly increased with increasing soil Cd treatment levels, while glutathione concentrations had no obvious change trends. Therefore, intracellular detoxification mechanisms of Cd in S. orientalis mainly rely on formation of less toxic Cd chemical forms, store of a large amount of Cd in cell wall and synthesis of thiol compounds.     

Influence of Lime and Organic Matter on the Mobility of Cadmium in Cadmium-Contaminated Soil in Relation to Nutrition of Spinach

Cadmium and cadmium compounds are water soluble, mobile in most soils, bio-available, and tend to bio-accumulate. A pot culture experiment was conducted on contaminated soil to study the influence of lime and organic matter on the mobility of cadmium in spinach and its rhizosphere soil. Application of lime (50% and 100% lime requirement) and organic matter (0.5 and 1% by weight of soil) to soil decreased the availability of Cd to the soil and plant throughout the crop growth. The highest diethylene triamine penta-acetic acid (DTPA) extractable Cd was 10.84 mg kg^?1 in the treatment OM₀ L₀ (No application of organic matter and lime) at 20 days after sowing of spinach. Likewise, the highest Cd concentration in spinach roots and shoots were 19.80 and 17.0 mg kg^?1 in the treatment OM₀ L₀ at 20 days after sowing. The Cd concentration in spinach roots and shoots were decreased by 63.23 and 71.88%, respectively, in the treatment OM₁ L₁₀₀ (application of FYM at 1.0% by weight of soil and lime at 100% lime requirement) after 60 days of growth. The lowest concentrations of Cd in the soil and plant after the harvest of the crop were 2.88 and 4.27 mg kg^?1, respectively, in the treatment OM₁ L₁₀₀ and resulted in 65.75 and 71.55% decrease over control (OM₀ L₀). The highest total chlorophyll content of leaves was 2.19 mg kg^?1 of fresh weight in the treatment OM₁ L₁₀₀ at 40 days of crop growth.     

Rapid transformations of plant water-soluble organic compounds in relation to cation mobilization in an acid Oxisol

The maintenance of plant residues on the surface of acid soils in no-tillage cropping systems reportedly increases the downward mobility of Ca and Al. This study investigated the effects of application of aqueous extracts of residues of radish (Raphanus sativus), blue lupine (Lupinus angustifolius), black oat (Avena strigosa), soybean (Glicine max), and wheat (Triticum aestivum), without incubation (initial extract) or incubated (15-day extract), on the chemistry of an acid Oxisol in 0.20-m columns. The application of initial extracts of plant residues increased the pH and the KCl-extractable contents of Ca²⁺, Mg²⁺ and Mehlich 1-extractable K⁺, and decreased the KCl-extractable Al³⁺ in the following order: blue lupine > radish > black oat > soybean > wheat. The Ca concentrations of the effluents, after application of the initial extracts of radish and blue lupine, were virtually the same as those in the extracts before application, whereas K was decreased by 40 – 90%, and more Al was extracted from the soil than the amount determined as KCl-extractable Al. The initial and 15-day extracts had similar effects on soil Ca and Al, however, the capacity of mobilizing Ca and Al was markedly decreased in the latter. This difference was associated with the type and relative composition of organic compounds in the water soluble organic fraction in both extracts as determined by gas chromatography–mass spectrometry (GC–MS). The concentration of water soluble organic compounds in the fresh green manures residues became drastically decreased (50% on average) after the incubation. The initial extracts of blue lupine and radish had a high proportion (20 and 30%, respectively) of the organic compounds as short-chain fatty acids with a high capacity of forming stable complexes with Ca and Al. In contrast, the 15-day extracts were predominated by long-chain fatty acids and aromatic compounds, which did not show the same effect. Fresh green-manure residues had water-soluble organic compounds of low molecular weight with high capacity of forming stable complexes with Ca and Al. The biological oxidation of these organic compounds occurred rapidly, markedly decreasing the capacity to mobilize cations in the aqueous plant-residue extracts.     

Possible involvement of plasma histidine in differential brain permeability to zinc and cadmium

Zinc gets into the brain parenchyma across the blood-brain and the blood-cerebrospinal fluid barriers, while cadmium hardly gets into the brain parenchyma. Because histidine may be involved in zinc transport across the brain barrier systems, the binding to histidine was compared between zinc and cadmium to understand the difference in brain permeability to both metals. Sephadex G-10 gel filtration indicated that ¹⁰⁹Cd, unlike ⁶⁵Zn, does not bind to histidine. When the plasma incubated with ⁶⁵Zn or ¹⁰⁹Cd was dialyzed in physiological saline containing histidine (0-10 mM), ⁶⁵Zn concentration in the dialysate was increased with the increase of the histidine concentration, suggesting the transfer of zinc from plasma proteins to histidine. The low affinity of zinc to plasma proteins may be important for brain permeability to this metal. On the other hand, ¹⁰⁹Cd was not detected in the dialysate in the presence of 0.1 mM histidine, which is equal to the concentration in the plasma, suggesting no transfer of cadmium from plasma proteins to histidine. These results suggest that the avid binding of cadmium to plasma proteins is related to brain impermeability to this metal.     

Role of rhizosphere mechanisms in Cd uptake by various wheat cultivars

In each wheat type, cultivars have different propensities to accumulate Cd in their grains, likely depending on Cd uptake by roots and/or Cd distribution in the plant. This study investigates the processes in the root–soil interface and their role in high or low grain Cd accumulation. Twenty-four cultivars of spring bread, winter bread, durum, and spelt wheat with different grain Cd accumulation levels were investigated regarding removal of Cd from soil, pH, Cd and organic acids in root exudates, and cation-exchange capacity of roots (rootCEC). In addition, we investigated ¹⁰⁹Cd uptake from a nutrient solution resembling soil solution. The removal of Cd from the rhizosphere soil increased, likely due to increased rootCEC with increased grain Cd accumulation propensity, except in spring bread wheat. The ¹⁰⁹Cd uptake from solution did not differ between high and low grain Cd accumulators. If the soil Cd concentration was elevated, rootCEC increased, as did pH, and succinic acid levels in the exudates, while lactic and citric acid levels in root exudates decreased. This work indicates that high grain Cd accumulators take up more Cd from soil than do low accumulators. But not by a different capacity to take up Cd from soil solution. The higher rootCEC in high accumulating cultivars may influence the release of Cd from the soil particles.     

Microbial immobilization of cadmium released from CdO in the soil

The effect of microorganisms on the fate of Cd introduced into the soil as cadmium oxide (CdO) was investigated. Cadmium oxide (875 µg Cd per gram of soil) was added to -irradiated (sterile) and non-sterile soils. The soils were incubated for 90 days at 18 °C under aerobic conditions with moisture kept at 60% of water-holding capacity. Half of the samples in each treatment were supplemented with starch (0.5%, w/w) in order to stimulate microbial growth in the non-sterile soil. After various time intervals (7- or 10-day), soil samples from each treatment were extracted with deionized distilled water (ratio 1:40) or 0.25 M CaCl₂ (ratio 1:5). The results indicated that during the incubation period the amount of Cd extracted from the non-sterile soil with either solvent was markedly lower than that extracted from the -irradiated sterile control. The addition of starch to the non-sterile soil reduced the concentration of Cd in the 0.25 M CaCl₂ extracts without affecting the Cd-content in the water extracts. Short-term experiments in which Cd was added to the soil as a solution of Cd(NO₃)₂ indicated that irradiation did not affect the sorption of Cd to the soil. The addition of bacterial mass (1 mg of dry weight g^–1 soil) decreased the amount of Cd extracted with water as well as that extracted with 0.25 M CaCl₂. Under sterile conditions the solubility of CdO in soil extracts was higher than in the other extractants. The addition of glucose (0.5%, w/w) or a glucose/starch mixture (0.5%, w/w of each) to the sterile soil increased the amount of extractable Cd after a short incubation (18 h at 18 °C). The obtained results suggest that primarily physicochemical reactions are involved in dissolving CdO in the soil but that microbial activity may be responsible for the immobilization of the released metal.     

Role of Organic Amendments to Mitigate Cd Toxicity and Its Assimilation in <i>Triticum aestivum</i> L.

In soil biota, higher and enduring concentration of heavy metals like cadmium (Cd) is hazardous and associated with great loss in growth, yield, and quality parameters of most of the crop plants. Recently, in-situ applications of eco-friendly stabilizing agents in the form of organic modifications have been utilized to mitigate the adverse effects of Cd-toxicity. This controlled experiment was laid down to appraise the imprints of various applied organic amendments namely poultry manure (PM), farmyard manure (FYM), and sugarcane press mud (PS) to immobilize Cd in polluted soil. Moreover, phytoavailability of Cd in wheat was also accessed under an alkaline environment. Results revealed that the addition of FYM (5–10 ton ha^-1 ) in Cd-contaminated soil significantly increased germination rate, leaf chlorophyll content, plant height, spike length, biological and grain yield amongst all applied organic amendments. Moreover, the addition of FYM (5–10 ton ha^-1 ) also reduced the phytoavailability of Cd by 73–85% in the roots, 57–83% in the shoots, and 81–90% in grains of wheat crop. Thus, it is affirmed that incorporation of FYM (5–10 ton ha^-1 ) performed better to enhance wheat growth and yield by remediating Cd. Thus, the application of FYM (5–10 ton ha^-1 ) reduced the toxicity induced by Cd to plants by declining its uptake and translocation as compared to all other applied organic amendments to immobilize Cd under sandy alkaline polluted soil.     

Accumulated forms of thallium and cadmium in Lemna minor. I. Distribution in aqueous soluble and insoluble fractions

Abstract

The distribution and chemical forms of thallium (Tl) and cadmium (Cd) in Lemna minor have been investigated using extractants of different polarity, enzyme digestion and ultrafiltration and chromatographic methods. Over 80% of Tl and 60% of Cd taken up by the plant was found in aqueous soluble forms. Water was more efficient than ethanol in extracting both elements; about 30% of bound Cd was released by dilute HCI treatment and Cd was mainly bound to pectins and proteins in the cell wall fractions but only a small proportion of Tl was associated with these components. In the aqueous soluble extracts a sizeable proportion of Cd was complexed with soluble moieties, including proteins; whereas Tl seems to be mainly present in the free ionic form.     

Cadmium influx across isolated Carcinus gill epithelium interaction of lanthanum and calcium with cadmium influxes

The effects of Ca and La on Cd transport across apical and basolateral gill surfaces were examined in isolated perfused Carcinus gills. In the gills exposed to diluted sea water enriched with calcium by addition of CaCl₂ to 11.9 and 15.9 mmol·l^-1 the Cd influxes decreased by 55% and 85%, respectively, compared to those observed in diluted sea water (6.9 mmol Ca·l^-1). When Ca was added to the perfusate to increase its concentration at the basolaterally oriented gill surfaces, Cd influx inhibition was less pronounced than when Ca was added apically. The effect of Ca on ¹⁰⁹Cd influxes appears, therefore, to be exerted at the apical gill surface. Additionally, the effects of various concentrations of the non-specific Ca channel blocker La (added to diluted sea water) on ¹⁰⁹Cd influxes in isolated perfused Carcinus gills were studied. ¹⁰⁹Cd influxes are shown to be lanthanum concentration dependent. The half-maximum inhibition of cadmium influxes by La occurred at 1.4·10^-6 mol·l^-1. Cadmium transport is discussed in terms of non-specific influx utilizing Ca channels.Abbreviations DSW diluted sea water - cpm counts per minute - BBMV brush-border membrane vesicles     

Bioaccumulation and Partitioning of Cadmium within the Freshwater Mussel Dreissena polymorpha Pallas

Kinetics of uptake, partitioning and elimination of cadmium were investigated in experimental studies with the freshwater mussel, Dreissena polymorpha. The radioactive cadmium isotopes ¹⁰⁹Cd and ¹¹⁵Cd were used as tracers. Shells, soft parts and body fluid of the mussel exhibited considerable differences in accumulation and elimination. Accumulation factors up to more than 70,000 were calculated for the periostracum, whereas accumulation factors for the whole mussels ranging up to 3,000 were calculated. The shells bound a great deal of cadmium, but only loosely, and the metal could be readily eliminated after transfer to uncontaminated water. In contrast, no significant amounts of the cadmium incorporated in the soft parts were eliminated. The results indicate that the major portion of cadmium in the soft parts is strongly bound and cannot be eliminated by exchange processes.