Phytoavailability of Cd and Zn in soil estimated by stable isotope exchange and chemical extraction

The distribution of labile Cd and Zn in two contrasting soils was investigated using isotopic exchange techniques and chemical extraction procedures. A sewage sludge amended soil from Great Billings (Northampton, UK) and an unamended soil of the Countesswells Association obtained locally (Aberdeen, UK) were used. ¹¹⁴Cd and ⁶⁷Zn isotopes were added to a water suspension of each soil and the labile metal pool (E-value) determined from the isotope dilution. Samples were obtained at 13 time points from 1h to 50 days. For the sewage sludge amended soil, 29 g Cd g^–1 (86% of total) and 806 g Zn g^–1 (65% of total) were labile and for the Countesswells soil the value was 8.6 g Zn g^–1 (13% of total); limits of detection prevented a Cd E-value from being measured in this soil. The size of the labile metal pool was also measured by growing plants for 90 days and determining the isotopic content of the plant tissue (L-value). Thlaspi caerulescensJ. & C. Presl (alpine penny cress), a hyperaccumulator of Zn and Cd, Taraxacum officinale Weber (dandelion) and Hordeum vulgare L. (spring barley) were used. L-values were similar across species and lower than the E-values. On average the L-values were 23±0.8 g Cd g^–1 and 725±14 g Zn g^–1 for the Great Billings soil and 0.29±0.16 g Cd g^–1 and 7.3±0.3 g Zn g^–1 for the Countesswells soil. The extractable metal content of the soils was also quantified by extraction using 0.1 M NaNO₃, 0.01 M CaCl₂, 0.5 M NaOH, 0.43 M CH₃COOH and 0.05 M EDTA at pH 7.0. Between 1.3 and 68% of the total Cd and between 1 and 50% of the total Zn in the Great Billings soil was extracted by these chemicals. For the Countesswells soil, between 6 and 83% of the total Cd and between 0.1 and 7% of the total Zn was extracted. 0.05 M EDTA and 0.43 M CH₃COOH yielded the greatest concentrations for both soils but these were less than the isotopic estimates. On the whole, E-values were numerically closer to the L-values than the chemical extraction values. The use of isotopic exchange provides an alternative estimate of the labile metal pool within soils compared to existing chemical extraction procedures. No evidence was obtained that T. caerulescens is able to access metal within the soil not freely available to the other plants species. This has implications for long term remediation strategies using hyperaccumulating plant species, which are unlikely to have any impact on non-labile Cd and Zn in contaminated soil.     

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.     

Phytoextraction of Risk Elements by Willow and Poplar Trees

To characterize the phytoextraction efficiency of two clones of willow trees (Salix x smithiana Willd., Salix rubens) and two clones of poplar trees (Populus nigra x maximowiczii, Populus nigra Wolterson) were planted in contaminated soil (0.4–2.0 mg Cd.kg^?1, 78–313 mg Zn.kg^?1, 21.3–118 mg Cu.kg^?1). Field experiment was carried out in Czech Republic. The study investigated their ability to accumulate heavy metals (Cd, Zn, and Cu) in harvestable plant parts. The poplars produced higher amount of biomass than willows. Both Salix clones accumulated higher amount of Cd, Zn and Cu in their biomass (maximum 6.8 mg Cd.kg^?1, 909 mg Zn.kg^?1, and 17.7 mg Cu.kg^?1) compared to Populus clones (maximum 2.06 mg Cd.kg^?1, 463 mg Zn.kg^?1, and 11.8 mg Cu.kg^?1). There were no significant differences between clones of individual species. BCs for Cd and Zn were greater than 1 (the highest in willow leaves). BCs values of Cu were very low. These results indicate that Salix is more suitable plant for phytoextraction of Cd and Zn than Populus. The Cu phytoextraction potential of Salix and Populus trees was not confirmed in this experiment due to low soil availability of this element.     

210Po Activity and Concentrations of Selected Trace Elements (As, Cd, Cu, Hg, Pb, Zn) in the Muscle Tissue of Tunas Thunnus albacares and Katsuwonus pelamis from the Eastern Pacific Ocean

Daily mineral intake (DMI) of Cu and Zn, percentage weekly intake (PWI) of As, Cd, Hg, Pb, and doses of ²¹⁰Po were estimated by using their elemental concentration in muscle of two tuna species and the average tuna consumption in Mexico. Skipjack tuna Katsuwonus pelamis had significantly (p?<?0.05) higher levels of As (1.38???g?g^?1 dw) and Cu (1.85???g?g^?1 dw) than yellowfin tuna Thunnus albacares, whereas Pb concentrations (0.18???g?g^?1 dw) were significantly (p?<?0.05) higher in T. albacares. The sequence of elemental concentrations in both species was Zn?>?Cu?>?As?>?Hg?>?Pb?>?Cd. In T. albacares, concentrations of Cd and Pb in muscle tissue were positively correlated (p?<?0.05) with weight of specimens, while Cu was negatively correlated. DMI values were below 10?%. PWI figures (<2?%) are not potentially harmful to human health. ²¹⁰Po concentration in T. albacares and K. pelamis accounts for 13.5 to 89.7?% of the median individual annual dose (7.1???Sv) from consumption of marine fish and shellfish for the world population.     

Impact of Land-Use Patterns on Chemical Properties of Trace Elements in Soils of Rural,Semi-Urban,and Urban Zones of the Niger Delta,Nigeria

The study of the concentrations of Cr, Zn, Cd, Pb, Ni, and Cu in soils under different land uses in rural, semi-urban, and urban zones in the Niger Delta was carried out with a view to providing information on the effects of the different land uses on the concentrations of trace elements in soils. Our results indicate significant variability in concentrations of these metals in soils under different land uses in rural, semi-urban, and urban zones. The maximum concentrations of metals in the examined soil samples were 707.5 mg.kg^?1, 161.0 mg.kg^?1, 2.6 mg.kg^?1, 59.6 mg.kg^?1, 1061.3 mg.kg^?1, and 189.2 mg.kg^?1 for Cr, Zn, Cd, Pb, Ni, and Cu, respectively. In the rural zone, the cassava processing mill is a potent source of Ni, Cr, Cu, and Zn while agricultural activities are a source of Cd, and automobile emissions and the use of lead oxide batteries constitute the major sources of Pb. In the urban zone, soils around the wood processing mill showed elevated concentrations of Cu, Cr, Zn, and Ni, while soils around automobile mechanic works and motor parks showed elevated levels of Pb. Elevated Cd concentrations were observed in soils under the following land uses: urban motor park, playground, welding and fabrication sheds, and metallic scrap dump. The contamination/pollution index of metals in the soil follows the order: Ni > Cd > Cr > Zn > Cu > Pb. The multiple pollution index of metals at different sites were greater than 1, indicating that these soils fit into “slight pollution” to “excessive pollution” ranges with significant contributions from Cr, Zn, Cd, Ni, and Cu.     

Cadmium,nickel, copper,and zinc influence on microfilament organization in Arabidopsis root cells

The plant cytoskeleton orchestrates such fundamental processes in cells as division, growth and development, polymer cross-linking, membrane anchorage, etc. Here, we describe the influence of Cd²⁺, Ni²⁺, Zn²⁺, and Cu²⁺ on root development and vital organization of actin filaments into different cells of Arabidopsis thaliana line expressing GFP-FABD2. CdSO₄, NiSO₄, CuSO₄, and ZnSO₄ were used in concentrations of 5–20 µM in this study. It was found that Cd, Ni, and Cu cause dose-dependent primary root growth inhibition and alteration of the root morphology, whereas Zn slightly stimulates root growth and does not affect the morphology of Arabidopsis roots. This growth inhibition/stimulation correlated with the various sensitivities of microfilaments to Cd, Ni, Cu, and Zn action. It was established that Cd, Ni, and Cu affected predominantly the actin filaments of meristematic cells. Cells of transition and elongation zones demonstrated strong actin filament sensitivity to Cd and Cu. Microfilaments of elongating root cells were more sensitive to Ni and Cu. Although Cd, Ni, and Cu stimulated root hair growth after long-term treatment, actin filaments were destroyed after 1 h exposure with these metals. Zn did not disrupt native actin filament organization in root cells. Thus, our investigation shows that microfilaments act as sensitive cellular targets for Cd, Ni, and Cu. More data on effects on native actin filaments organization would contribute to a better understanding of plant tolerance mechanisms to the action of these metals.     

A family of polyamino phenolic macrocyclic ligands. Acid-base and coordination properties towards Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions

The acid-base and coordination properties towards Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) of four polyamino-phenol macrocycles 15-hydroxy-3,6,9-triazabicyclo[9.3.1]pentadeca-11,13,1¹⁵-triene L1, 18-hydroxy-3,6,9,12-tetraazabicyclo[12.3.1]octadeca-14,16,1¹⁸-triene L2, 21-hydroxy-3,6,9,12,15-pentaazabicyclo[15.3.1]enaicosa-17,19,1²¹-triene L3 and 24-hydroxy-3,6,9,12,15,18-hexaazabicyclo[18.3.1]tetraicosa-20,22,1²⁴-triene L4 are reported. The protonation and stability constants were determined by means of potentiometric measurements in 0.15 mol dm⁻³ NMe₄Cl aqueous solution at 298.1 K. L1 forms highly unsaturated Co(II), Cu(II), Zn(II) and Cd(II) mononuclear complexes that are prone to give dimeric dinuclear species with [(MH₋₁L1)₂]²⁺ stoichiometry, in solution. L2 forms stable Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) mononuclear complexes that can coordinate external species as OH⁻ anion, giving hydroxylated complexes at alkaline pH. L3 forms stable Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) mononuclear complexes and Co(II), Ni(II), Cu(II) and Zn(II) dinuclear [M₂H₋₁L3]³⁺ species. L4 forms stable mono- and dinuclear Co(II), Cu(II), Zn(II) and Cd(II) complexes, but only mononuclear species with Pb(II). The effect of macrocyclic size is considered in the discussion of results.     

Mobility and Distribution of Zinc,Cadmium and Lead in Calcareous Soils Receiving Spiked Sewage Sludge

Leaching column experiments were conducted to determine the degree of mobility and the distribution of zinc (Zn), cadmium (Cd), and lead (Pb) because of an application of spiked sewage sludge in calcareous soils. A total of 20 leaching columns were set up for four calcareous soils. Each column was leached with one of these inflows: sewage sludge (only for two soils), spiked sewage sludge, or artificial well water (control). The columns were irrigated with spiked sewage sludge containing 8.5 mg Zn l^?1, 8.5 mg Cd l^?1, and 170 mg Pb l^?1 and then allowed to equilibrate for 30 days. At the end of leaching experiments, soil samples from each column were divided into 18 layers, each being 1 cm down to 6 cm and 2 cm below that, and analyzed for total and extractable Zn, Cd and Pb. The fractionation of the heavy metals in the top three layers of the surface soil samples was investigated by the sequential extraction method. Spiked sewage sludge had little effect on metal mobility. In all soils, the surface soil layers (0-1 cm) of the columns receiving spiked sewage sludge had significantly higher concentrations of total Zn, Cd and Pb than control soils. Concentration of the heavy metals declined significantly with depth. The mobility of Zn was usually greater than Cd and Pb. The proportion of exchangeable heavy metals in soils receiving spiked sewage sludge was significantly higher than that found in the control columns. Sequential extraction results showed that in native soils the major proportion of Zn and Pb was associated with residual (RES) and organic matter (OM) fractions and major proportion of Cd was associated with carbonate (CARB) fraction, whereas after leaching with spiked sewage sludge, the major proportion of Zn and Pb was associated with Fe-oxcide (FEO), RES, and CARB fractions and major proportion of Cd was associated with CARB, RES and exchangeable (EXCH) fractions. Based on relative percent, Cd in the EXCH fraction was higher than Zn and Pb in soils leached with spiked sewage sludge.     

Significance and Interspecific Variability of Accumulated Trace Metal Concentrations in Antarctic Benthic Crustaceans

Trace metals (Cd, Cu, Pb and Zn) were analysed in crustaceans collected on Polarstern cruises ANT XVI/2 (1999) and ANT XXI/2 (2003/04, BENDEX) to the Weddell Sea. Our study provides further evidence for the frequently reported “Cd anomaly” in polar crustaceans, with data ranging from 1.2 (Ceratoserolis trilobitoides) to 6.2 mg Cd kg^–1 DW (Notocrangon antarcticus) in 1999 and from 1.2 (Waldeckia obesa) to 20.3 mg Cd kg^–1 (Tryphosella murrayi) in 2003. Pb concentrations well below 1 mg kg^–1 in most of the samples analysed might serve as a regional or even global background value for comparison in biomonitoring studies. Increasing Cu concentrations from eggs of decapods (e.g., 5 vs. 51 mg kg^–1 in N. antarcticus) or juveniles in the brood pouch of an amphipod species to adult females indicate that the enzymatic requirements and haemocyanin component demand for Cu in early life‐history stages is probably not met without a distinct bioaccumulation of this essential element after hatching. Most interestingly, Cd also increases (<0.1 vs. 6.2 mg kg^–1 in N. antarcticus). This could be the consequence of efficient uptake mechanisms for Cu that cannot discriminate between this element and Cd. Cu and Zn concentrations in decapods of this study are largely within the range reported worldwide (40–90 mg Cu kg^–1 and 40–80 mg Zn kg^–1), indicating that these elements are regulated. The enormous heterogeneity of Cd and Zn in many amphipod species investigated (e.g., from 0.6 in Gnathiphimedia mandibularis to 34.4 mg Cd kg^–1 in Orchomenopsis acanthura and from 41 in Eusirus antarcticus to 1244 mg Zn kg^–1 in Iphimediella bransfieldi) supports the hypothesis of the “Cd anomaly” and suggests that there is probably no consistent metabolic demand for the essential element Zn in this taxonomic group. The heterogeneity of Cu in amphipods is less pronounced. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simultaneous extraction of soil phytoavailable cadmium,copper, and lead by chelating resin membrane

Cadmium, copper, and lead were extracted from suspensions of contaminated soils using metal chelating exchange resin membranes. Nine soils with widely varying properties and Cd, Cu and Pb levels were tested. Soil suspensions made up with 4 g in 40 mL deionized water were equilibrated with 5 cm² Ca-saturated Chelex exchange resin membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs. Resin membrane extractable Cd, Cu and Pb of the soils were correlated with Cd, Cu, and Pb uptake by young wheat seedlings grown in these soils and compared with soil Cd, Cu, and Pb extracted by 0.1 M HCl, 0.01 M CaCl₂, and 0.005 M Diethylenetriamine pentaacetic acid (DTPA). The amounts of Cd, Cu and Pb extracted by the Ca-saturated Chelex membrane from all tested soils correlated well with those absorbed by young wheat seedlings. The Ca-saturated Chelex membrane extractable Cd, Cu and Pb of the soil had the strongest correlation with plant uptake Cd, Cu and Pb among the extraction methods we tested. It was demonstrated that the Ca-saturated Chelex membrane extraction is an appropriate method in simultaneously estimating Cd, Cu and Pb phytoavailability of soil and is applicable to a wide range of soils.     

The Heavy Metal Content of Wild Edible Mushroom Samples Collected in Canakkale Province,Turkey

In this study, concentrations of heavy metals (Cd, Cr, Cu, Pb, and Zn) were determined in three edible mushroom species (Lactarius deliciosus, Russula delica, and Rhizopogon roseolus) collected in five sampling sites in Canakkale province, Turkey. Mean values of Cd, Cr, Cu, Pb, and Zn were 0.72, 0.26, 28.34, 1.53, and 64.62 mg/kg, respectively. The highest concentrations of Cd, Cu, Pb, and Zn were determined in species R. delica, while Cr was observed in L. deliciosus. In terms of the nutritional aspect, taking into account the concentration of Provisional Tolerable Weekly Intake recommended by FAO/WHO, the maximum concentration of Cd is a restrictive factor for consumption of the collected mushroom species. The concentrations of the other elements have no health risks when consumed at optimal levels.     

Cd, Cu, Zn, Se, and Metallothioneins in Two Amphibians, Necturus maculosus (Amphibia, Caudata) and Bufo bufo (Amphibia, Anura)

The accumulation of cadmium, its affinity for metallothioneins (MTs), and its relation to copper, zinc, and selenium were investigated in the experimental mudpuppy Necturus maculosus and the common toad Bufo bufo captured in nature. Specimens of N. maculosus were exposed to waterborne Cd (85???g/L) for up to 40?days. Exposure resulted in tissue-dependent accumulation of Cd in the order kidney, gills > intestine, liver, brain > pancreas, skin, spleen, and gonads. During the 40-day exposure, concentrations increased close to 1???g/g in kidneys and gills (0.64?C0.95 and 0.52?C0.76; n?=?4), whereas the levels stayed below 0.5 in liver (0.14?C0.29; n?=?4) and other organs. Cd exposure was accompanied by an increase of Zn and Cu in kidneys and Zn in skin, while a decrease of Cu was observed in muscles and skin. Cytosol metallothioneins (MTs) were detected as Cu,Zn?Cthioneins in liver and Zn,Cu?Cthioneins in gills and kidney, with the presence of Se in all cases. After exposure, Cd binding to MTs was clearly observed in cytosol of gills as Zn,Cu,Cd?Cthionein and in pellet extract of kidneys as Zn,Cu,Cd?Cthioneins. The results indicate low Cd storage in liver with almost undetectable Cd in liver MT fractions. In field trapped Bufo bufo (spring and autumn animals), Cd levels were followed in four organs and found to be in the order kidney > liver (0.56?C5.0???g/g >0.03?C0.72???g/g; n?=?11, spring and autumn animals), with no detectable Cd in muscle and skin. At the tissue level, high positive correlations between Cd, Cu, and Se were found in liver (all r?>?0.80; ???=?0.05, n?=?5), and between Cd and Se in kidney (r?=?0.76; n?=?5) of autumn animals, possibly connected with the storage of excess elements in biologically inert forms. In the liver of spring animals, having higher tissue level of Cd than autumn ones, part of the Cd was identified as Cu,Zn,Cd?Cthioneins with traces of Se. As both species are special in having liver Cu levels higher than Zn, the observed highly preferential Cd load in kidney seems reasonable. The relatively low Cd found in liver can be attributed to its excretion through bile and its inability to displace Cu from MTs. The associations of selenium observed with Cd and/or Cu (on the tissue and cell level) point to selenium involvement in the detoxification of excessive cadmium and copper through immobilization.     

Electrochemical synthesis and crystal structures of nickel(II), copper(II), zinc(II) and cadmium(II) complexes with N,N′-bis[(4-methylphenyl)sulfonyl]ethylenediamine

The electrochemical oxidation of anodic metal (nickel, copper, zinc and cadmium) in acetonitrile solutions containing N,N′-bis[(4-methylphenyl)sulfonyl]ethylenediamine H₂L and an additional nitrogen coligand, such as 1,10-phenanthroline, yielded mixed complexes of general formula [ML(phen)₂] (M=Ni, Cu, Zn and Cd). The compounds have been characterized by microanalysis, IR and UV-Vis (Ni, Cu complexes) spectroscopy, FAB mass spectrometry, ¹H NMR spectroscopic studies (Zn, Cd complexes) and EPR spectroscopy (Cu and Ni complexes). All compounds have also been characterized by single crystal X-ray diffraction. The molecular structures of these compounds consist of individual monomeric molecules in which the metal atom is in an [MN₆] distorted octahedral environment.     

Effects of Municipal Sewage Sludge Doses on the Chlorophyll Contents and Heavy Metal Concentration of Sugar Beet (Beta vulgaris var. saccharifera)

The present study was conducted to assess the suitability of sewage sludge amendment (SSA) in soil for Beta vulgaris var. saccharifera (sugar beet) by evaluating the heavy metal accumulation and physiological responses of plants grown at a 10%, 25%, and 50% sewage sludge amendment rate. The sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently increasing accumulation in plant parts. Cd, Pb, Ni, and Cu concentrations in roots were significantly higher in plants grown at 25% as compared to 50% SSA; however, Cr and Zn concentration was higher at 50% than 25% SSA. The concentrations of heavy metal showed a trend of Zn > Ni > Cu > Cr > Pb > Cd in roots and Zn > Cu > Ni > Cr > Pb > Cd in leaves. The only instance in which the chlorophyll content did not increase after the sewage sludge treatments was 50%. There were approximately 1.12-fold differences between the control and 50% sewage sludge application for chlorophyll content. The sewage sludge amendment led to a significant increase in Pb, Cr, Cd, Cu, Zn, and Ni concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency (US EPA). The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake and the leaf and root concentrations of Ni, Zn, Cd, Cu, Cr, Pb, and Zn in plants as compared to those grown on unamended soil. More accumulation occurred in roots and leaves than in shoots for most of the heavy metals. The concentrations of Cd, Cr, and Pb were more than the permissible limits of national standards in the edible portion of sugar beet grown on different sewage sludge amendment ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet may not be a good option due to risk of contamination of Cr, Pb, and Cd.     

The Accumulation of Risk and Essential Elements in Edible Mushrooms Chlorophyllum rhacodes,Suillus grevillei,Imleria badia,and Xerocomellus chrysenteron Growing in the Czech Republic

Risk and essential elements were determined in fruiting bodies of wild growing edible mushrooms Chlorophyllum rhacodes, Suillus grevillei, Imleria badia, and Xerocomellus chrysenteron collected in an unpolluted site in South Bohemia, the Czech Republic. The elements were also determined in underlying soils and the bioconcentration factors were calculated. The analyses revealed that C. rhacodes accumulated Ag, Cu, Rb, Se, Zn, As, Cd, and Tl. On the other hand, S. grevillei accumulated Cd, Rb, Ag, Se, and Cs. I. badia and X. chrysenteron strongly accumulated Rb, Cs, and Ag; these species showed the ability to accumulate Cu and Zn as well. Contents of detrimental Cr^VI were in all cases below the quantification limit (0.003 mg kg^?1 dry matter). Studied mushroom species (mainly C. rhacodes) accumulated some toxic elements. However, no considerable effect on human health is expected since they are usually consumed as a delicacy and do not represent a major component of diet.     

Vertical and Horizontal Distributions of Zn,Cd, Pb,Cu, and Hg in Uncultivated Soil in the Vicinity of a Zinc Smelter at Odda,Norway

In the present work the extent and variation of Zn, Cd, Pb, Cu, and Hg loading in undisturbed surface soil (0–5 cm) and the vertical transport of the metals in soil profiles are studied in the vicinity of a zinc smelter in Norway. Three major controlling factors on the metal concentrations in soil have been assessed: 1) distance from the anthropogenic point source; 2) organic matter content (O.M.); and 3) the prevailing wind directions. Moreover metal distributions in proximal soil profiles in 1972 and 2003 are compared. Current concentrations of Zn, Cd, Pb, Cu, and Hg in surface soil reach 14000, 60, 980, 430, and 7.0 mg·kg ^{? 1} , respectively, near the smelter and decrease regularly with distance in the northerly direction according to the regression model (y = ax^{? b} ). The Zn concentrations are significantly different from the background range up to 30 km from the smelter, whereas the other metals approach background at only 10 km distance. Subsurface concentration peaks of Pb, Cu, and Hg are found at greater depth in soil profiles than peaks of Zn and Cd. Levels of Zn, Cd, and Pb in surface soil seem to have decreased from 1972 to 2003, whereas for Cu the levels appear not to be significantly different.     

Factors affecting immobilization of heavy metals by purple nonsulfur bacteria isolated from contaminated shrimp ponds

In order to remove heavy metals (HMs) from contaminated shrimp pond at the highest concentrations found of; 0.75 mg/l Cd²⁺, 62.63 mg/l Pb²⁺, 34.60 mg/l Cu²⁺ and 58.50 mg/l Zn²⁺, two strains of purple nonsulfur bacteria isolated from shrimp ponds (NW16 and KMS24) were investigated for their ability to immobilize HMs in 3% NaCl in both microaerobic-light and aerobic-dark conditions. Based on metabolic inhibition and metabolic-dependent studies, it was concluded that both strains removed HMs using biosorption and also bioaccumulation. The efficiency of removal by both strains with both incubating conditions tested was in the order of lead (Pb) > copper (Cu) > zinc (Zn) > cadmium (Cd). Optimal conditions for removal of HMs by strain NW16 were; cells in the log phase at 4.5 mg DCW/ml, pH 6.0, and 30°C for 30 min. With microaerobic-light conditions, the relative percent removal of HMs was: Pb, 83; Cu, 59; Zn, 39; Cd, 23 and slightly more with the aerobic-dark conditions (Pb, 90; Cu, 69; Zn, 46; Cd, 28). Cells in the log phase at 5.0 mg DCW/ml, pH 5.5, and 35°C for 45 min were optimal conditions for strain KMS24 and there were no significant differences for the removal percentages of HMs with either incubating conditions (averages: Pb, 96; Cu, 75; Zn, 46; Cd, 30). The presence of Ca²⁺ and Mg²⁺ significantly decreased the removal capacity of HMs for both strains.     

Tolerance and hyperaccumulation of a mixture of heavy metals (Cu,Pb, Hg,and Zn) by four aquatic macrophytes

In the present investigation, four macrophytes, namely Typha latifolia (L.), Lemna minor (L.), Eichhornia crassipes (Mart.) Solms-Laubach, and Myriophyllum aquaticum (Vell.) Verdc, were evaluated for their heavy metal (Cu, Pb, Hg, and Zn) hyperaccumulation potential under laboratory conditions. Tolerance analyses were performed for 7 days of exposure at five different treatments of the metals mixture (Cu⁺², Hg⁺², Pb⁺², and Zn⁺²). The production of chlorophyll and carotenoids was determined at the end of each treatment. L. minor revealed to be sensitive, because it did not survive in all the tested concentrations after 72 hours of exposure. E. crassipes and M. aquaticum displayed the highest tolerance to the metals mixture. For the most tolerant species of aquatic macrophytes, The removal kinetics of E. crassipes and M. aquaticum was carried out, using the following mixture of metals: Cu (0.5 mg/L) and Hg, Pb, and Zn 0.25 mg/L. The obtained results revealed that E. crassipes can remove 99.80% of Cu, 97.88% of Pb, 99.53% of Hg, and 94.37% of Zn. M. aquaticum withdraws 95.2% of Cu, 94.28% of Pb, 99.19% of Hg, and 91.91% of Zn. The obtained results suggest that these two species of macrophytes could be used for the phytoremediation of this mixture of heavy metals from the polluted water bodies.     

Microbial community and extracellular polymeric substances analysis of anaerobic granular sludge exposed to selenate,cadmium and zinc

The microbial community and extracellular polymeric substances composition of anaerobic granular sludge exposed to selenate (~10 mg/L), cadmium (Cd) and zinc (Zn) (~2 and 5 mg/L) were investigated by high-throughput sequencing and fluorescence excitation emission matrix (FEEM) spectra, respectively. As a response to selenate, Cd and/or Zn exposure, significant fluorescence quenching of fulvic-like acids and humic-like substances was observed. With selenate, Cd and/or Zn in the influent with respective concentrations of 10, 5 and 5 mg/L, the abundance of the phyla Proteobacteria, Firmicutes, Spirochaetae, Cloacimonetes and Synergistetes increased significantly, and the dominant taxa in the anaerobic granular sludge exposed to Se, Cd and/or Zn were Halothiobacillaceae (10.2%), Pseudomonas (8.8%), Synergistaceae (7.7%), Spirochaetaceae (7.2%), Blvii28 wastewater sludge group (6.7%), Telmatospirillum (4.6%), Veillonellaceae (4.3%), Geobacter (4.0%) and Enterobacteriaceae (3.0%). Compared with the inoculum, the abundance of the archaea Methanobacterium and Methanosaeta decreased to below detection limit in the UASB reactor after 116 days exposure to Se, Cd and Zn.     

Distribution and bioavailability of heavy metals in different particle-size fractions of sediments in Taihu Lake,China

Abstract

Taihu Lake is one of the most important water sources in the economically developed central-eastern part of China, and metal pollution is a major concern for the lake. The distribution and bioavailability of Cd, Cr, Cu, Pb, Sb and Zn were analysed in undifferentiated bottom sediments and in various particle-size fractions of the sediment from different parts of the lake. The average concentration of total metals in undifferentiated sediments ranged from 0.86 mg kg^-1 (Cd) to 95.45 mg kg^-1 (Zn) for the entire lake, with the highest concentrations in Zhushan Bay. The concentration of heavy metals was higher in extremely fine sands (0.064–0.125 mm) and fine sands (0.125–0.25 mm) than in other fractions. Sequential extractions showed that Cu, Zn and Cd were the most bioavailable accounting for 55.6%, 38.7% and 30.0% of their total concentration, respectively. However, the bioavailable proportion of many metals was not significantly different between grain grades except for Cu and Zn, which were higher in silts (<0.064 mm) than in other grades. Compared with the background values of local soils, the concentration of Zn, Cd, Cu, Pb and Sb was higher, indicating enrichment in the sediment. From ecological safety concerns, Zn, Cd and Cu should be examined closely because of their higher bioavailabilty in the sediment.