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Accurately predicting the accumulation and toxicity of metals in organisms is a challenging work in ecotoxicology. Here, we developed and validated a physiologically based toxicokinetic and toxicodynamic (PBTK-TD) model for adult zebrafish exposed to Cd and Pb. The model included the gill, liver, intestine, gonad, carcass, and brain, which were linked by blood circulation in the PBTK process and by dynamic relationships between the target organ concentrations and mortality in the TD process. Results showed that the PBTK sub-model can accurately describe and predict the uptake, distribution and disposition kinetics of Cd and Pb in zebrafish. The exchange rates and the accumulation of the metals in the organs were significantly different. For Cd, the highest exchange rate was between blood and liver, and the greatest accumulation of Cd occurred in the liver. For Pb, the greatest accumulation occurred in the gill. The TD sub-model further indicated that metal concentrations in the gill may effectively act as more suitable indicator of Cd and Pb toxic effect than whole body or other organs. The proposed PBTK-TD model is helpful to understanding the fundamental processes by which zebrafish regulate the uptake and disposition of metal and to quantitatively predicting metal toxicity., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Lead (Pb) contaminated soil is of particular concern for infants and children due to their susceptibility to exposure, fast metabolic rates and rapidly developing neuronal systems. Determining the bioaccessibility of Pb in soils is critical in human health risk assessments, which can vary due to different soil properties and sources of Pb contamination. In this study, the potential relationships between soil properties and Pb bioaccessibility from various Pb sources including Pb contamination from mining (specifically, Broken Hill), three shooting ranges, a smelter and two industry sites (pottery and battery), were investigated using the Relative Bioavailability Leaching Procedure (RBALP). We found the following: (1) CEC, TOC, sand and silt content, and total Pb were significantly different (p < 0.05) between the two particle size fractions of < 2 mm and < 250 μm; (2) EC, CEC and total Pb were significantly correlated to Pb bioaccessibility (p < 0.05); and (3) soil analyses based on source of Pb demonstrated a strongly significant relationship between Pb bioaccessibility and soil properties (CEC, EC, clay content and total Pb) for mining soils from Broken Hill (r 2  = 0.86, p < 0.05, n = 18). These results demonstrated the influences of Pb contamination sources, soil properties and particle size fractions on Pb bioaccessibility as well as the prediction of Pb bioaccessibility using soil properties. The findings documented here will help in developing a predictive tool for human health risk assessment and the remediation of Pb contaminated soils., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Recently, several bioavailability-based models have been shown to predict acute metal mixture toxicity with reasonable accuracy. However, the application of such models to chronic mixture toxicity is less well established. Therefore, we developed in the present study a chronic metal mixture bioavailability model (MMBM) by combining the existing chronic daphnid bioavailability models for Ni, Zn, and Pb with the independent action (IA) model, assuming strict non-interaction between the metals for binding at the metal-specific biotic ligand sites. To evaluate the predictive capacity of the MMBM, chronic (7d) reproductive toxicity of Ni-Zn-Pb mixtures to Ceriodaphnia dubia was investigated in four different natural waters (pH range: 7-8; Ca range: 1-2 mM; Dissolved Organic Carbon range: 5-12 mg/L). In each water, mixture toxicity was investigated at equitoxic metal concentration ratios as well as at environmental (i.e. realistic) metal concentration ratios. Statistical analysis of mixture effects revealed that observed interactive effects depended on the metal concentration ratio investigated when evaluated relative to the concentration addition (CA) model, but not when evaluated relative to the IA model. This indicates that interactive effects observed in an equitoxic experimental design cannot always be simply extrapolated to environmentally realistic exposure situations. Generally, the IA model predicted Ni-Zn-Pb mixture toxicity more accurately than the CA model. Overall, the MMBM predicted Ni-Zn-Pb mixture toxicity (expressed as % reproductive inhibition relative to a control) in 85% of the treatments with less than 20% error. Moreover, the MMBM predicted chronic toxicity of the ternary Ni-Zn-Pb mixture at least equally accurately as the toxicity of the individual metal treatments (RMSE Mix  = 16; RMSE Zn only  = 18; RMSE Ni only  = 17; RMSE Pb only  = 23). Based on the present study, we believe MMBMs can be a promising tool to account for the effects of water chemistry on metal mixture toxicity during chronic exposure and could be used in metal risk assessment frameworks., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Pb tolerant mechanisms, plant physiological response and Pb sub-cellular localization in the root cells of Iris halophila were studied in sand culture and the Pb mine tailings. Results showed that the activities of superoxide dismutase (SOD) and peroxidase (POD) in the underground parts and the activity of catalase (CAT) in the aboveground and underground parts increased as Pb level was enhanced. Glutathione (GSH) and ascorbic acid (AsA) contents increased by Pb treatments. Pb deposits were found in the middle cell walls or along the inner side of epibiotic protoplasm of some cells which accumulated a large quantity of Pb and died. The dry weights (DWs) of aboveground parts under all Pb tailings treatments decreased insignificantly, while the DW of the underground parts growing in the pure Pb tailings decreased significantly. Pb, Cu, Cd, and Zn contents increased significantly as the levels of Pb tailings were enhanced and Pb contents in the aboveground and underground parts reached 64.75 and 751.75 μg/g DW, respectively, at pure Pb tailings treatment. The results indicated that I. halophila is a promising plant in the phytoremediation of Pb contaminated environment. Some antioxidant enzymes, antioxidants and compartmentalization of Pb were played major roles in Pb tolerance of I. halophila., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Predicting the accumulation and toxicity of mixtures of metals to aquatic organisms is a key challenge in ecotoxicological studies. In this study, the accumulation and toxicity of mixed essential (Cu) and nonessential (Cd and Pb) metals in zebrafish larvae exposed to a binary mixture of these elements at environmentally relevant concentrations were predicted using a refined toxicokinetic (TK)-toxicodynamic (TD) model aided with biotic ligand model (BLM) and toxic equivalent factor (TEF) approach. Competitive inhibition and non-competitive interaction/inhibition were observed in bio-uptake. Both Pb and Cd behaved as competitive inhibitors of Cu uptake at high Cu concentrations (>0.1 μM). By contrast, Cu uptake was independent of Cd or Pb when the Cu concentrations were below 10(-7) M. Furthermore, low concentrations of Cu had an adiaphorous effect on Cd or Pb uptake. Cd uptake was inhibited by Pb, and the Pb uptake rates consistently decreased in the presence of Cd. The accumulation processes of Cd-Pb, Cu-Cd, and Cu-Pb were accurately predicted by the BLM-aided TK models. The traditional TD model could successfully predict the toxicity of Cd-Pb mixtures, but not those of Cu-Cd or Cu-Pb mixtures. The revised TD model, which considered the possible different killing rates (Kk) above or below the threshold, offered better prediction for the toxicity of Cu-Cd or Cu-Pb mixtures. The overall findings may be of key significance in understanding and predicting metal uptake, accumulation, and toxicity in binary or multiple metal exposure scenarios., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The aim of this study was the multi-elemental detection of toxic metals such as lead (Pb) in non-crushed oyster shells by using a portable X-ray fluorescence (XRF) spectrometer. A rapid, simultaneous multi-element analytical methodology for non-crushed oyster shells has been developed using a portable XRF which provides a quick, quantitative, non-destructive, and cost-effective mean for assessment of oyster shell contamination from Pb. Pb contamination in oyster shells was further confirmed by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The results indicated that Pb is distributed in-homogeneously in contaminated shells. Oyster shells have a lamellar structure that could contribute to the high accumulation of Pb on oyster shells., (Published by Elsevier Ltd.)

Helicid snails appear to regulate Pb more closely than other toxic metals, though it is reported as the least toxic. No regulatory mechanism has been described in animals, and the possible role of Mg in limiting Pb assimilation is examined here for the first time. Three populations of Cantareus aspersus were fed Pb and Ca with three levels of Mg for up to 64 days. Metal assimilation and production efficiency was calculated for each of 108 snails. Populations differed in their pattern of uptake but soft tissue Pb was unaffected by dietary Mg. The proportion of Pb assimilated did not change as soft tissue concentrations increased, indicating no specific regulatory mechanism. The daily addition of Pb to the soft tissues increases with growth rate suggesting uptake is instead some function of growth or cell turnover. Bioconcentration factors varied with time and are unreliable indicators of an evolved regulatory mechanism for Pb., (Copyright 2010 Elsevier Ltd. All rights reserved.)

The present study addresses the key issue of linking the chemical speciation to the uptake of priority pollutants Cd(II) and Pb(II) in the wastewater treatment plant effluents, with emphasis on the role of the colloidal organic matter (EfOM). Binding of Cd(II) and Pb(II) by EfOM was examined by an ion exchange technique and flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry in parallel to bioassays with green microalga Chlorella kesslerii in ultrafiltrate (<1 kDa) and colloidal isolates (1 kDa to 0.45 mum). The uptake of Cd by C. kesslerii was consistent with the speciation analysis and measured free metal ion concentrations, while Pb uptake was much greater than that expected from the speciation measurement. Better understanding of the differences in the effects of the EfOM on Cd(II) and Pb(II) uptake required to take into account the size dependence of metal binding by EfOM., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Particles from channelled emissions of a battery recycling facility were size-segregated and investigated to correlate their speciation and morphology with their transfer towards lettuce. Microculture experiments carried out with various calcareous soils spiked with micronic and sub-micronic particles (1650+/-20mg Pb kg(-1)) highlighted a greater transfer in soils mixed with the finest particles. According to XRD and Raman spectroscopy results, the two fractions presented differences in the amount of minor lead compounds like carbonates, but their speciation was quite similar, in decreasing order of abundance: PbS, PbSO(4), PbSO(4) x PbO, alpha-PbO and Pb(0). Morphology investigations revealed that PM(2.5) (i.e. Particulate Matter 2.5 composed of particles suspended in air with aerodynamic diameters of 2.5 microm or less) contained many Pb nanoballs and nanocrystals which could influence lead availability. The soil-plant transfer of lead was mainly influenced by size and was very well estimated by 0.01M CaCl(2) extraction.

Plants grown in contaminated areas may accumulate trace metals to a toxic level via their roots and/or leaves. In the present study, we investigated the distribution and sources of Pb and Cd in maize plants (Zea mays L.) grown in a typical zinc smelting impacted area of southwestern China. Results showed that the smelting activities caused significantly elevated concentrations of Pb and Cd in the surrounding soils and maize plants. Pb isotope data revealed that the foliar uptake of atmospheric Pb was the dominant pathway for Pb to the leaf and grain tissues of maize, while Pb in the stalk and root tissues was mainly derived from root uptake. The ratio of Pb to Cd concentrations in the plants indicated that Cd had a different behavior from Pb, with most Cd in the maize plants coming from the soil via root uptake.

The root uptake of lead (Pb) by trees and the transfer of Pb by leaf litter deposition to the forest floor were investigated through a pot experiment with Norway spruce. Natural Pb and radio isotopic lead (210Pb) were determined in needles and twigs and in the pot soil spiked with 210Pb. Calculations of the specific activity in plant material and in the supporting pot soil showed that less than 2% of the Pb content of needles and twigs originates from root uptake and approximately 98% are deposited from the atmosphere. Atmospheric Pb has declined by a factor of 7 from 1980 to 2007 but is still a major pathway of Pb to vegetation and topsoils. The conclusion from the experiment is that the internal circulation of Pb through root uptake, translocation and litterfall, gives an insignificant input of Pb to the forest floor compared to atmospheric deposition.

Metal accumulation by aquatic bryophytes was investigated using data for headwater streams of differing chemistry. The Windermere Humic Aqueous Model (WHAM) was applied to calculate chemical speciation, including competitive proton and metal interactions with external binding sites on the plants. The speciation modelling approach gives smaller deviations between observed and predicted bryophyte contents of Cu, Zn, Cd and Pb than regressions based on total filtered metal concentrations. If all four metals, and Ni, are considered together, the WHAM predictions are superior at the 1% level. Optimised constants for bryophyte binding by the trace metals are similar to those for humic substances and simple carboxylate ligands. Bryophyte contents of Na, Mg and Ca are approximately explained by binding at external sites, while most of the K is intracellular. Oxide phases account for some of the Al, and most of the Mn, Fe and Co.

Uptake of Pd, Cd and Pb by the marine macroalga, Ulva lactuca, has been studied in the presence of an anionic (sodium dodecyl sulphate, SDS), cationic (hexadecyltrimethylammonium bromide; HDTMA) and non-ionic (Triton X-100; TX) surfactant. Compared with the surfactant-free system, metal sorption was reduced in the presence of SDS or TX. Neither surfactant, however, had any measurable impact on cell membrane permeability, determined by leakage of dissolved free amino acids (DFAA), or on metal internalisation. We attribute these observations to the stabilisation of aqueous Cd and Pb by SDS and the shielding of otherwise amenable sorption sites by TX. Presence of HDTMA resulted in a reduction in the extent of both sorption and internalisation of all metals and a significant increase in the leakage of DFAA. Thus, by enhancing membrane permeability, HDTMA exerts the greatest influence on metal behaviour in the presence of U. lactuca.

Lichens were used to evaluate the metal pollution in a forest ecosystem around the smelter of Murdochville, Canada. As reached values 5.8 times higher in the smelter vicinity than in the 'background' sites. This enrichment was 2 times higher for 3 metals (Cu, Cd and Pb). The highest As, Ba, Cd, Cu, and Pb concentrations in lichens were 4, 112, 1, 23, 50 and 952 mg/kg respectively. Contamination declined exponentially with increasing distance from the smelter and was related to elevation and slope exposition to the smelter flux. (206)Pb/(207)Pb and (206)Pb/(204)Pb ratios were low close to the smelter (1.16 and 18), but increased with distance to constant values (1.19 and 18.7) and showed an inverse correlation with lead concentrations. Forest contamination was detectable up to 30 km from the smelter.

Over 400tons of Pb enters Swiss soils annually at some 2000 military shooting ranges (MSRs). We measured elements in the leaves of 10 plant species and associated rhizospheric soil on the stop butt of a disused MSR. The geometric mean concentrations of Pb, Sb, Cu, Ni in rhizospheric soils were 10,171mg/kg, 5067mg/kg, 4125mg/kg and 917mg/kg. Some species contained Pb, Cu and Ni, above concentrations (30mg/kg, 25mg/kg and 50mg/kg) shown to be toxic to livestock. Most contaminants in leaves resulted from surface deposition. However, at soil Pb concentrations >60,000mg/kg, Equisetum arvense and Tussilago farfara took up >1000mg/kg Pb into the leaves. These plants are not hyperaccumulators, having <100mg/kg Pb in leaves at lower soil concentrations. Removal of soil with more than 30,000 Pb, from which one could smelt this metal to offset remediation costs, followed by revegetation, would minimise dust and hence leaf-borne contaminants.

The metal concentrations in a copper mine tailings and desert broom (Baccharis sarothroides Gray) plants were investigated. The metal concentrations in plants, soil cover, and tailings were determined using ICP-OES. The concentration of copper, lead, molybdenum, chromium, zinc, arsenic, nickel, and cobalt in tailings was 526.4, 207.4, 89.1, 84.5, 51.7, 49.6, 39.7, and 35.6mgkg(-1), respectively. The concentration of all elements in soil cover was 10-15% higher than that of the tailings, except for molybdenum. The concentration of copper, lead, molybdenum, chromium, zinc, arsenic, nickel, and cobalt in roots was 818.3, 151.9, 73.9, 57.1, 40.1, 44.6, 96.8, and 26.7mgkg(-1) and 1214.1, 107.3, 105.8, 105.5, 55.2, 36.9, 30.9, and 10.9mgkg(-1) for shoots, respectively. Considering the translocation factor, enrichment coefficient, and the accumulation factor, desert broom could be a potential hyperaccumulator of Cu, Pb, Cr, Zn, As, and Ni.

We examined the concentrations of 11 trace metals in tissues from 10 body parts of Great Tits and Greenfinches collected at Badachu Park in the Western Mountains of Beijing, China to assess the metal accumulation level, distribution among body parts, and species and gender related variations. The highest concentrations of Hg, Ni, Zn, and Mn were found in the feather; Pb and Co in the bone; Cd, Cr, and Se in the kidney, and Cu in the liver and heart. Metal concentrations had substantial interspecific variation with Great Tits showing higher levels of Hg, Cr, Ni, and Mn than Greenfinches in tissues of most body parts. Gender related variations were body part and species specific. Meta-analyses using data from this study and other studies suggested that metal concentrations of Great Tits at our study site were relatively low and below the toxic levels.

The effect of two earthworm species, Lumbricus rubellus and Eisenia fetida, on the fractionation/bioavailability of Pb and Zn before and after soil leaching with EDTA was studied. Four leaching steps with total 12.5 mmol kg(-1) EDTA removed 39.8% and 6.1% of Pb and Zn, respectively. EDTA removed Pb from all soil fractions fairly uniformly (assessed using sequential extractions). Zn was mostly present in the chemically inert residual soil fraction, which explains its poor removal. Analysis of earthworm casts and the remainder of the soil indicated that L. rubellus and E. fetida actively regulated soil pH, but did not significantly change Pb and Zn fractionation in non-remediated and remediated soil. However, the bioavailability of Pb (assessed using Ruby's physiologically based extraction test) in E. fetida casts was significantly higher than in the bulk of the soil. In remediated soil the Pb bioavailability in the simulated stomach phase increased by 5.1 times.

Tobacco plants transformed with TaLCT1 were cultured on Knop's medium with modified calcium concentrations (0.01-3 mM) in the presence of Pb(2+), and in soil contaminated by lead. A 4-5 microM Pb(2+) administered in the presence of 1 mM Ca(2+) inhibited the root growth of transgenic plants to much lesser degree than of control plants, whereas in the presence of 3mM Ca(2+) no differences were found between the studied lines. The reduction of Pb(2+) toxicity in the presence of 1 mM Ca(2+) was not accompanied by a change in the lead tissue concentration. However, when Ca(2+) level in the medium was lowered to 0.01 mM, several fold higher root/shoot Pb ratio in transgenic plants was observed, twofold increase in the total amount of metal accumulated, and lower concentration of Pb in the xylem sap. Results suggest the involvement of TaLCT1 in the regulation of Ca-dependent Pb-detoxification, and under conditions of low calcium in lead uptake and distribution.

The mechanistic bioaccumulation model OMEGA (Optimal Modeling for Ecotoxicological Applications) is used to estimate accumulation of zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in the earthworm Lumbricus rubellus. Our validation to field accumulation data shows that the model accurately predicts internal cadmium concentrations. In addition, our results show that internal metal concentrations in the earthworm are less than linearly (slope<1) related to the total concentration in soil, while risk assessment procedures often assume the biota-soil accumulation factor (BSAF) to be constant. Although predicted internal concentrations of all metals are generally within a factor 5 compared to field data, incorporation of regulation in the model is necessary to improve predictability of the essential metals such as zinc and copper.

Trace elements were analyzed in fish of commercial interest to determine their importance in marine systems of the Western Indian Ocean and their bioaccumulation patterns. The results are equivalent or lower than levels reported in ichthyofauna worldwide. Certain values of muscular Cd, Hg, Pb and Zn were, however, above thresholds for human consumption. Levels varied among tissues, species and fish length, but were seldom influenced by the nutritional condition of the fish, its gender and its reproductive status. Correlations between hepatic Hg and Se levels in Swordfish (r2=0.747) and Yellowfin Tunas (r2=0.226), and among metallothionein linking metals imply the existence of detoxification processes in these species. Level differences between fish from the Mozambique Channel and Reunion Island reflect differences of diets rather than differences of elemental availability in both environments.

We quantified bioaccumulation of lead, mercury, and cadmium in bones from 105 greater white-toothed shrews (Crocidura russula) collected at the Ebro Delta, a polluted area, and the Medas Islands, a control site. Lead and mercury levels varied with site, age, and sex, although statistical significances depended on each factor. Globally, shrews from the polluted area exhibited significantly higher concentrations of Pb and Hg. Increment of Pb with age was particularly remarkable in wetland animals and was interpreted in relation to human activities, namely hunting. Unlike males, females from the Ebro Delta maintained low Hg levels, which were associated with gestation and lactation. Cadmium levels did not differ between sites, sexes, or ages. This study provides the first data on heavy metals in mammals from this wetland and suggests that C. russula is a good bioindicator of metal pollution. We concluded that sex and age may represent an important source of variation in the bioaccumulation of these metals in wild populations.

The stabilization of metal contaminated soil is being tested as an alternative remediation method to landfilling. An evaluation of the changes in Cu and Pb mobility and bioavailability in soil induced by the addition of coal fly ash and natural organic matter (peat) revealed that the amount of leached Cu decreased by 98.2% and Pb by 99.9%, as assessed by a batch test. Metal leaching from the treated soil was lower by two orders of magnitude compared to the untreated soil in the field lysimeters. A possible formation of mineral Cu- and Pb-bearing phases and active surface with oxides were identified by chemical equilibrium calculations. Low metal leaching during a two-year observation period, increased seed germination rate, reduced metal accumulation in plant shoots, and decreased toxicity to plants and bacteria, thereby demonstrating this stabilization method to be a promising technique for in situ remediation of Cu and Pb contaminated soil.

Despite its environmental (and financial) importance, there is no agreement in the literature as to which extractant most accurately estimates the phytoavailability of trace metals in soils. A large data set was taken from the literature, and the effectiveness of various extractants to predict the phytoavailability of Cd, Zn, Ni, Cu, and Pb examined across a range of soil types and contamination levels. The data suggest that generally, the total soil trace metal content, and trace metal concentrations determined by complexing agents (such as the widely used DTPA and EDTA extractants) or acid extractants (such as 0.1M HCl and the Mehlich 1 extractant) are only poorly correlated to plant phytoavailability. Whilst there is no consensus, it would appear that neutral salt extractants (such as 0.01 M CaCl(2) and 0.1 M NaNO(3)) provide the most useful indication of metal phytoavailability across a range of metals of interest, although further research is required.

Lead and cadmium uptake was investigated for common deciduous street trees in Beijing in this study. Species having Cd accumulation included Populus tomentosa, Sophora japonica and Catalpa speciosa. P. tomentosa had the highest ratios between leaf and soil Cd (0.848), followed by S. japonica (0.536), C. speciosa (0.493), Paulownia tomentosa (0.453) and Juglans regia (0.415). Pb levels were high in leaves of C. speciosa, J. regia and Pa. tomentosa. S. japonica had the highest ratio between leaf Pb and soil Pb (0.146), followed by Pa. tomentosa (0.143), Ginko biloba (0.103) and C. speciosa (0.095). A predictive foliar metal accumulation index (MAI) was developed and C. speciosa was calculated to have the highest MAI value (53.8). This suggests that C. speciosa would be a good choice for planting in areas of Beijing where soil contamination with Cd and Pb may be a problem.

The transfer characteristics of Cd and Pb from soils to the edible parts of six vegetable species were calculated from plant and corresponding surface soil samples collected from the fields in Fujian Province, southeastern China. The soil-to-plant transfer factors (TF) calculated from both total and DTPA-extractable Cd and Pb in the soils decreased with increasing total or DTPA-extractable Cd and Pb, indicating that the TF values of Cd and Pb depend on the soil metal content. For most plants studied, there was a significant relation between the TF values and the corresponding soil metal concentrations (total or DTPA-extractable) that was best described by an exponential equation (y=axb). We recommend that the representative TF value for a given crop-metal system should be estimated from the regression models between the transfer factors and the corresponding soil metal concentrations and at a given soil metal concentration.

Four sites were selected for collection of plants growing on polluted soil developed on tailings from Ag, Au, and Zn mines at the Zacatecas state in Mexico. Trace element concentrations varied between sites, the most polluted area was at El Bote mine near to Zacatecas city. The ranges of total concentration in soil were as follows: Cd 11-47, Ni 19-26, Pb 232-695, Mn 1132-2400, Cu 134-186 and Zn 116-827 mg kg(-1) air-dried soil weight. All soil samples had concentrations above typical values for non-polluted soils from the same soil types (Cd 0.6+/-0.3, Ni 52+/-4, Pb 41+/-3mg kg(-1)). However, for the majority of samples the DTPA-extractable element concentrations were less than 10% of the total. Some of the wild plants are potentially metal tolerant, because they were able to grow in highly polluted substrates. Plant metal analysis revealed that most species did not translocate metals to their aerial parts, therefore they behave as excluder plants. Polygonum aviculare accumulated Zn (9236 mg kg(-1)) at concentrations near to the criteria for hyperaccumulator plants. Jatropha dioica also accumulated high Zn (6249 mg kg(-1)) concentrations.

Combined use of batch equilibration adsorption and X-ray absorption spectroscopy (XAS) was employed to study the mechanisms of competitive adsorption of Pb, Cu, and Cd on Danish and Heilongjiang peat in single- and multi-solute systems. The adsorption capacity and initial adsorption rate on the same peat in single-solute systems followed the order Pb>Cu>Cd. Both the adsorbed amount of each metal (q'm) and its initial adsorption rate were decreased in multi-solute systems. It was observed that the adsorbed amounts of metals at low-energy adsorption sites (qm,1) decreased pronouncedly compared to those at high-energy adsorption sites (qm,2), indicating that the competitive adsorption of Pb, Cu and Cd occurred mainly at the low-energy adsorption sites. XAS study revealed that both Pb and Cu were coordinated in peat predominantly to carboxylic moieties without excluding the hydroxyl groups, thereby providing an insight into the mechanism of competitive adsorption of Pb and Cu on peat.

This work reports kinetic and equilibrium studies of cadmium(II) and lead(II) adsorption by the brown seaweed Cystoseira baccata. Kinetic experiments demonstrated rapid metal uptake. Kinetic data were satisfactorily described by a pseudo-second order chemical sorption process. Temperature change from 15 to 45 degrees C showed small variation on kinetic parameters. Langmuir-Freundlich equation was selected to describe the metal isotherms and the proton binding in acid-base titrations. The maximum metal uptake values were around 0.9 mmol g(-1) (101 and 186 mg g(-1) for cadmium(II) and lead(II), respectively) at pH 4.5 (raw biomass), while the number of weak acid groups were 2.2 mmol g(-1) and their proton binding constant, K(H), 10(3.67) (protonated biomass). FTIR analysis confirmed the participation of carboxyl groups in metal uptake. The metal sorption was found to increase with the solution pH reaching a plateau above pH 4. Calcium and sodium nitrate salts in solution were found to affect considerably the metal biosorption.

The effects of bone char (BC) application on the bioavailability of Pb in a polluted soil from Hunan Province, China were examined. The Pb-contaminated soil was treated with two types of bone char, one from the UK and the other from China. The bioavailability of Pb was determined in terms of the uptake by Chinese cabbage (Brassica chinensis L.), sequential extraction and X-ray diffraction analysis. The results indicate that the Pb concentrations in both shoots and roots decreased with increasing quantities of added bone char, and the application of BC from the UK at the rate of 1.6% (w:w) had the largest effect. Lead Pb concentrations in the shoots and roots decreased by 56.0% and 75.9%, respectively, whereas the application of BC from Zhejiang Province, China at the rate of 1.6% (w:w) reduced Pb concentrations in the shoots and roots to 2.04 mgkg(-1) and 8.42 mgkg(-1), respectively, only 45.8% and 30.2% compared to the control treatment. Sequential extraction results indicate that the addition of bone char, as a metal-immobilizing agent, substantially transforms soil Pb from non-residual fractions to the residual fraction. The transformation was further confirmed using X-ray diffraction studies.

European walnut (Juglans regia) plants were grown in pots, on peat soil contaminated with lead (Pb), for four years. European walnut was chosen because it grows in Mediterranean climates, it yields a high biomass, and a fine quality wood. In the above ground parts Pb concentration was 1000 times lower than in roots: in 50 g roots there was 450 mg of Pb. Microanalysis of roots found in periderm more than 50% of the total root Pb. Pb L(III) EXAFS spectroscopy was performed on: root powder from Pb-exposed plants, Pb-impregnated cellulose and lignin. Comparison of plant material with lignin and cellulose helped to envisage a plant disposal strategy for Pb. This may consist in establishing links with large organic molecules, which are abundant constituents of cell walls. EXAFS spectroscopy evidenced the presence of Pb-O bindings within the ligno-cellulosic structure in roots. Lead was scantly conveyed to the shoots, giving to walnut plants an added asset in Pb phytostabilization.

The orthopteran insect Tetrix tenuicornis, collected from polluted and unpolluted areas, was used to study heavy metal accumulation and its impact on stress protein levels and on changes in the number and morphology of chromosomes in mitotic and meiotic cells. During two consecutive years, insects were collected from polluted areas of zinc-lead mine spoils near Bolesław (Poland) and from unpolluted areas near Busko and Staszów (Poland). T. tenuicornis from the polluted area showed 1.5, 4.03, 4.32 and 41.73 times higher concentrations of copper (Cu), zinc (Zn), lead (Pb) and cadmium (Cd), respectively, than insects of the same species collected from unpolluted areas. Insects exposed to heavy metals showed only small changes, and rather a decrease in the concentration of constitutive and inducible heat shock proteins Hsp70, the level of which increases under stress conditions. A cytogenetic study of T. tenuicornis revealed intra-population anomalies in chromosome number and morphology in mitotic and meiotic cells and the presence of an additional B chromosome in germinal cells. In 50% of females collected from polluted areas, mosaic oogonial mitotic chromosome sets and diploid, hypo- or hypertetraploid, tetraploid, and octoploid chromosome numbers were detected. In turn, 14.6% of males showed a heterozygous deficiency of chromatin in L2 and M3 bivalents in addition to the presence of B chromosomes.

Significant hyperaccumulation of Zn, Cd and Pb in field samples of Thlaspi praecox Wulf. collected from a heavy metal polluted area in Slovenia was found, with maximal shoot concentrations of 14,590 mg kg(-1) Zn, 5960 mg kg(-1) Cd and 3500 mg kg(-1) Pb. Shoot/root ratios of 9.6 for Zn and 5.6 for Cd show that the metals were preferentially transported to the shoots. Shoot bioaccumulation factors exceeded total soil Cd levels 75-fold and total soil Zn levels 20-fold, further supporting the hyperaccumulation of Cd and Zn. Eighty percent of Pb was retained in roots, thus indicating exclusion as a tolerance strategy for Pb. Low level colonisation with arbuscular mycorrhizal fungi (AMF) of a Paris type was observed at the polluted site, whereas at the non-polluted site Arum type colonisation was more common. To our knowledge this is the first report of Cd hyperaccumulation and AMF colonisation in metal hyperaccumulating T. praecox.

Submersed plants can be useful in reducing heavy metal concentrations in stormwater, since they can accumulate large amounts of heavy metals in their shoots. To investigate the effects of water temperature and salinity on the metal uptake of two submersed plant species, Elodea canadensis (Michx.) and Potamogeton natans (L.), these plants were grown in the presence of Cu, Zn, Cd, and Pb at 5, 11, and 20 degrees C in combination with salinities of 0, 0.5, and 5 per thousand. The metal concentrations in the plant tissue increased with increasing temperature in both species; the exception was the concentration of Pb in Elodea, which increased with decreasing salinity. Metal concentrations at high temperature or low salinity were up to twice those found at low temperature or high salinity. Plant biomass affected the metal uptake, with low biomass plants having higher metal concentrations than did high biomass plants.

The concentrations of lead, zinc, copper and cadmium accumulated by 12 emergent-rooted wetland plant species including different populations of Leersia hexandra, Juncus effusus and Equisetum ramosisti were investigated in field conditions of China. The results showed that metal accumulation by wetland plants differed among species, populations and tissues. Populations grown in substrata with elevated metals contained significantly higher metals in plants. Metals accumulated by wetland plants were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them. That some species/populations could accumulate relatively high metal concentrations (far above the toxic concentration to plants) in their shoots indicates that internal detoxification metal tolerance mechanism(s) are also included. The factors affecting metal accumulation by wetland plants include metal concentrations, pH, and nutrient status in substrata. Mostly concentrations of Pb and Cu in both aboveground and underground tissues of the plants were significantly positively related to their total and/or DTPA-extractable fractions in substrata while negatively to soil N and P, respectively. The potential use of these wetland plants in phytoremediation is also discussed.

Sediments from lakes near Rouyn-Noranda, Quebec, contain elevated concentrations of several metals, including Cd, Cu, Pb and Zn. Amphipods, fingernail clams, mayflies and tanytarsid midges were absent, and sediment toxicity was observed in chronic tests with Hyalella in sediments from Lac Dufault, the lake closest to Rouyn-Noranda. Bioaccumulation by Hyalella demonstrated elevated bioavailability of Cd, Co, Cr, Pb and Tl, but only Cd was accumulated to levels close to the toxic threshold. Copper, which is regulated by Hyalella, was not elevated in these amphipods, but it was elevated in overlying water in the toxicity tests. Toxic effects in Lac Dufault sediments are probably caused primarily by Cd, at least in amphipods, with a possible minor contribution from Cu. An integrated assessment, including sediment chemistry, benthic community composition, sediment toxicity, metal bioaccumulation in benthos, and comparison of bioaccumulation and/or overlying water concentrations with threshold effect concentrations, provides the best indication of effects and their cause.

A field study was undertaken to determine whether 207Pb and 111Cd, applied to the exterior bark of sugar maple (Acer saccharum Marsh.), white ash (Fraxinus americana L.) and white pine (Pinus strobus L.), could enter xylem tissue. Stable isotope tracers (3 microg Pb ml(-1); 2 microg Cd ml(-1)) were applied separately to bark in simulated rainfall, acidified to pH 4.5, in multiple doses over a 4 month (July-October) period. Tree cores were extracted from the region of application in the following March, and Pb and Cd isotopes were measured in bark and the outer tree rings using inductively coupled plasma mass spectrometry. The majority of the applied stable isotope tracer recovered (over 94%) was present in bark tissue, although a small amount of each metal tracer entered the outer (1-3) tree rings in all trees. Despite high concentrations of excess 207Pb in bark (up to 50 microg g(-1)), the maximum concentration of excess 207Pb measured in tree rings was only around 50 ng g(-1), which represents less than 30% of the background Pb concentration in wood at the study site. High excess 111Cd concentrations in bark (up to 35 microg g(-1)) also resulted in small increases in 111Cd in wood (up to 50 ng g(-1)), but due to lower background Cd concentrations in wood, such increases more than doubled the amount of Cd in wood compared with background levels. However, at sites where such high bark Cd concentrations are found, uptake from Cd-contaminated soil would probably be much greater than found at our study site. It appears that Cd and Pb applied to bark can enter woody tissue, but that this route of uptake is likely to be a minor contributor to the metal burden in wood.

The intracellular localization of heavy metals using autometallography (AMG) and X-ray microanalysis was studied in the palps, the digestive gland and the gills of mussels Mytilus galloprovincialis, after an experimental exposure to 0.1 mg l(-1) of Hg and 0.1 mg l(-1) of Pb, for 30 and 60 days. In the examined tissues, autometallographical black silver deposits (BSD) were localized mainly in the residual bodies and heterolysosomes of the digestive cells, as well as in the dense bodies of the epithelial cells. Metal deposition after Hg exposure was much more abundant compared to Pb exposure. Using X-ray microanalysis, Hg was traced on the BSD in all examined tissues, while Pb was not traced in these deposits. The results are discussed in comparison to previous results on long-term exposure to the same metals; in addition, the palps are introduced as a new metal storing organ and, finally, the use of X-ray microanalysis under a scanning electron microscope in order to enhance the specificity of AMG is suggested.

The potential value of the marine prosobranch Nerita saxtilis as an efficient biological monitor to heavy metal pollution in the Red Sea was investigated. Storage ability of lead and cadmium was compared in shell, headfoot and digestive gland of the marine snail N. saxtilis collected from Al-Hamrauin area at El-kuseir (lead, 300.35 +/- 28.53 microg/l, 1,716 +/- 16.14. cadmium 20.01 +/- 1.8 microg/l, 161.72 +/- 21.4 mean +/- S.D. for water and sediment, respectively) relative to that of inhabiting marine water and sediment employing atomic absorption spectrometry to determine the organ with highest capability of heavy metal accumulation. The influence of metal storage on light microscopic structure of that organ was investigated. Also, the ultrastructure localization of storage sites in the same organ was determined employing transmission electron microscopy. The digestive gland was shown to accumulate both metals at conccntrations that are several orders of magnitude higher than those in the surrounding marine water. The bioaccumulation capability of lead and cadmium was ranked in the following order; digestive gland > headfoot > shell for lead and digestive gland > shell > headfoot for cadmium. In spite of its evident highest metal storage capability, no histopathological changes were observed in the digestive gland of that marine prosobranch. Enlarged electron dense vesicles and many granules were observed in ultrathin sections in digestive cells of these snails and are suggested to be the sites of storage of detoxified metals. The results of that finding indicate the possibility of using the marine prosobranch N. saxtilis as biomonitor for heavy metal contaminants in the Red Sea.

Twenty-one wild brown rats (Rattus norvegicus) were collected from four areas of Milan (Italy). Main organs were harvested from each rat, fixed in 10% neutral buffer formalin, and embedded in paraffin. Organ sections were stained with hematoxylin and eosin, kidney sections were also stained with the Ziehl-Neelsen method. Graphite furnace atomic absorption spectrophotometry was performed on all kidney samples. The presence of inclusion bodies and karyocytomegaly was scored. Six adult rats out of 21 (28.6%) showed kariocytomegaly and intranuclear inclusion bodies of the renal proximal tubules, characteristic of lead toxicity. The nuclear inclusion bodies were always Ziehl-Neelsen positive. The six rats which showed the characteristic histological alterations ascribed to lead, had lead concentrations statistically higher than the three control rats (4 microg/g wet wt. versus 0.09 microg/g wet wt., P<0.001) and than the captured wild rats. Intranuclear inclusion bodies were found in rats with kidney lead concentrations greater than 0.6 microg/g wet weight. There were significant differences between the four areas of capture. The incidence of intranuclear inclusion bodies and karyocytomegaly in proximal tubular cells was higher in rats with high lead levels detected by spectrophotometry. The present results indicate a renal lead concentration of 0.6 microg/g wet weight as a threshold to detect histologic kidney changes due to lead absorption. Results demonstrate that the examination of adult free-living rats may be considered an appropriate method to obtain a rapid, sensitive, easy, cost effective estimate of lead contamination in urban areas. Animal models allow us to evaluate potential human health risk associated with environmental contamination.

The concentrations of mercury (Hg), cadmium (Cd), lead (Pb) and selenium (Se) were determined in liver, kidney and muscle samples from 20 Baltic ringed seals (Phoca hispida botnica) (3-32 years), and from 17 ringed seals (Phoca hispida) (0-20 years) from Svalbard, in the Arctic. The concentrations of Hg and Se were considerably higher in the Baltic ringed seals, but the Cd concentrations lower than in the Svalbard ringed seals. There was no big geographical difference with respect to Pb concentrations. Se and Hg concentrations showed a significant positive correlation in both regions. By comparison with earlier studies on Baltic seals, the metal concentrations have remained at the same level since the 1980s. Of the metals we studied, only the level of Hg in Baltic ringed seals can be considered high (mean 53 mg/kg, range 6.5-124 mg/kg wet wt. for liver), but probably not high enough to cause metal intoxication. No pathological changes associated with metal intoxication were observed in the seals.

Small-scale element distribution in soil-plant-systems in patches of Empetrum nigrum (microsites) at heavy metal contaminated sites located 0.5 and 4 km from the copper-nickel smelter at Harjavalta was investigated. The Cu concentrations of E. nigrum varied between 12 and 2300 mg/kg dw and showed increasing accumulation with increasing tissue age. Stems contained more Cu than leaves of the same age. The distribution pattern of Ni and Pb in the above-ground biomass followed that of Cu. Roots contained relatively low concentrations of all airborne heavy metals. In the soil, the highest concentrations of total Cu occurred in the humus (Oh) layer: on average 49,450 mg/kg dw at 0.5 km distance and 12,025 mg/kg dw at 4.0 km. Despite the extremely high Cu concentrations in the topsoil, the concentrations in the mineral soil below a depth of 10 cm did not exceed 2.5 mg/kg dw at any site.

The ability of Pycnoporus sanguineus to adsorb heavy metals from aqueous solution was investigated in fixed-bed column studies. The experiments were conducted to study the effect of important design parameters such as column bed height, flow rate and initial concentration of solution. The breakthrough profiles were obtained in these studies. A mathematical model based on external mass transfer and pore diffusion was used for the prediction of mass transfer coefficient and effective diffusivity of metals in macro-fungi bed. Experimental breakthrough profiles were compared with the simulated breakthrough profiles obtained from the mathematical model. Bed Depth Service Time (BDST) model was used to analyse the experimental data and evaluated the performance of biosorption column. The BDST model parameters needed for the design of biosorption columns were evaluated for lead, copper and cadmium removal in the column. The columns were regenerated by eluting the metal ions using 0.1 M hydrochloric acid solution after the adsorption studies. The columns were subjected to repeated cycles of adsorption of same metal ions and desorption to evaluate the removal efficiency after adsorption-desorption.

Lead and zinc levels in sediments and biota from the fjord system surrounding the lead/zinc mine at Maarmorilik, West Greenland, were investigated to evaluate the impact of waste rock and marine-deposited tailings on the marine biota. Concentrations of metal in the sediment were up to 8,922 +/- 622 microg g(-1) (dry wt.) for lead and 19,351+/- 476 microg g(-1) (dry wt.) for zinc. Levels of lead and zinc were also elevated in a suite of monitor organisms. The feeding modes of the organisms were used to explain the sources of metals to the organisms. After closure of the mine, the concentrations of metals in the upper centimetres of the sediments decreased, and a decreased impact of metals on the brown alga Fucus distichus was observed. However, the metals in the sediments still affect the marine biota in the area.