Solvent toxicity to amphibian embryos and larvae

Organic micropollutants are often damaging for aquatic organisms. Being usually hydrophobic compounds, they are often dissolved in an organic co-solvent which increases their solubility in water. The aim of this study was to study the toxicity of various solvents on embryos (protected or not by jelly coat) and on tadpoles of the common frog (Rana temporaria). Tested solvents were methanol (MeOH), methylene chloride (CH(2)Cl(2)), dimethyl sulfoxyde (DMSO), acetone (Ac) and ethanol (EtOH). Embryos exhibited higher mortality rates than tadpoles. Embryos with jelly were more sensitive to high concentration of solvents than embryos without jelly (except for acetone). According to these results, Ac, DMSO and CH(2)Cl(2) can be used as co-solvents in water to help the dissolution of micropollutants at concentration equal to or lower than 0.001 ml/l for frog embryos, and EtOH, Ac and CH(2)Cl(2) at concentration equal to or lower than 0.01 ml/l for Rana temporaria tadpoles.     

Bioaccumulation of trace elements in omnivorous amphibian larvae: implications for amphibian health and contaminant transport

Despite the influence that amphibians have on the flow of energy and nutrients in ecological systems, the role that amphibians play in transporting contaminants through food webs has received very little attention. This study was undertaken to investigate bioaccumulation of trace elements in amphibians relative to other small aquatic organisms in a contaminated wetland. We collected bullfrog larvae (Rana catesbeiana) along with three other species of small vertebrates and four species of invertebrates from a site contaminated with a wide array of trace elements and analyzed them for trace element concentrations and stable nitrogen and carbon isotope composition. We found that amphibian larvae accumulated the highest concentrations of most trace elements, possibly due to their feeding ecology. These results suggest that omnivorous amphibian larvae can serve as a critical link for trace element trophic transfer. Their propensity to accumulate trace elements may have important implications for amphibian health in contaminated environments and should be further investigated.     

Dietary mercury exposure and bioaccumulation in amphibian larvae inhabiting Carolina bay wetlands

Inorganic mercury and methylmercury concentrations were measured both in guts and remaining carcasses of southern leopard frog (Rana sphenocephala) larvae from 10 Carolina bay wetlands in South Carolina, USA. Significant variation among bays in methylmercury and inorganic mercury concentrations existed both in guts and carcasses. There was a moderate negative correlation between dissolved organic carbon concentration in bays and mean inorganic mercury concentrations in guts. There was also a weak positive correlation between pH in bays and mean methylmercury concentrations in carcasses. The ratio of methylmercury to inorganic mercury decreased with increasing total mercury concentration in guts and in larvae, but the rate of decrease was highly variable among bays. Ratios of concentrations in carcasses to concentrations in guts were inversely related to gut concentration. Mercury concentrations in carcasses in some bays were within the range of concentrations at which adverse effects have been observed in laboratory studies of R. sphenocephala.     

Difference of lead,copper and zinc concentrations between interiors and exteriors of peds in some contaminated soils

Solute transport of elements in soils depends on the soil structural and hydraulic properties, and it is controlled by sorption and diffusion, which both limit the mobility and distribution of elements in soils. This study was conducted to compare lead (Pb), copper (Cu) and zinc (Zn) concentrations between ped exteriors and interiors of some contaminated soils. The results show that the differences of the heavy metals between exteriors and interiors decreased in the order clayey soil, clayey loam soil, loam soil. For same soils, the differences decreased from Pb to Cu to Zn. The differences in readily extractable concentrations of the three metals between ped exteriors and interiors were much larger than the differences in their total metals, this may indicate that extractable metals were more recently deposited. The higher Pb and Cu concentrations in the ped exteriors than interiors may additionally be explained by anthropogenic input, movement and downward through preferential flow.     

Effects of ultraviolet-B radiation on behaviour and growth of three species of amphibian larvae

Effects of ultraviolet-B (UV-B) radiation on amphibian embryos have been investigated in a number of studies, but the effects on larvae have received less attention. We investigated the effects of UV-B radiation on the behaviour and growth of larvae of three amphibians (Rana arvalis, Rana temporaria and Bufo bufo) in two different experiments. First, we tested whether larvae of the three species actively avoid UV-B exposure if given a choice. We found no evidence for active avoidance of UV-B or changes in activity in the presence of UV-B in any of the species. Second, we assessed the effects of natural (1.25 kJm(-2)) and enhanced (1.58 kJm(-2)) UV-B radiation on the survival and growth of the three species and found that the exposure to UV-B radiation did not have any effect on survival rates of any of the species. However, UV-B radiation had a positive effect on the growth of R. arvalis and R. temporaria, whereas the growth of B. bufo tadpoles was unaffected by the UV-B treatments. Our results suggest that a short-term exposure to UV-B radiation does not induce any UV-B avoidance behaviour in tadpoles of these three species. Furthermore, unlike some previous studies, the results suggest that the young tadpoles of these species are not negatively affected by UV-B radiation. In fact, our results demonstrate that a moderate amount of UV-B radiation enhance tadpole growth rates in two of the three species.     

Variation in the relationship between blood lead and air lead

Estimates of the slope of the relationship between blood lead (μg dl⁻¹) and air lead (μg m⁻³) obtained in ten independent studies are compared. No significant differences were detected among the estimates which ranged from 0.6 to 3.1 μg dl⁻¹ per μg m⁻³ and represented male adult, female adult and child populations. A single best estimate of 1.2 μg dl⁻¹ per μg m⁻³ ( ± 0.2,95 per cent confidence limits) was obtained. It is concluded that, if the blood lead-air lead slope depends on various physical and biological factors, then studies providing more precise estimates are required to detect these differences.     

Chemical fractionation of copper, lead and zinc in ombrotrophic peat

Measurement of operationally defined chemical fractions in ombrotrophic peat samples provides information not obtained by total metal extractions. Examination of such sequential data permits interpretation of process dynamics. Results for copper, lead and zinc chemical fractionation of peat profiles from Ringinglow Bog, near Sheffield, Great Britain, are reported and discussed. Lead and zinc share similar patterns of partitioning. A considerable proportion of these records is in a form predisposed to transformation and mobilisation. In contrast, much of the copper is comparatively immobile, it being associated with the more chemically intractable fractions. The results suggest that peat copper deposition records may be used for reconstruction of pollution history. The use of lead and zinc records for these purposes is problematic.     

Solubility of lead, zinc and copper added to mineral soils

Elevated levels of heavy metals in soils are a result of industrial activities, atmospheric deposition, and the land application of sewage sludges and industrial by-products. Their persistence in the soil environment has created interest in the possible changes in solubility. In this study, total dissolved concentrations of Pb, Zn, and Cu were monitored in seven metal-amended soils (a calcareous and six acid mineral soils). Single metal solutions were added to soils and equilibrated (aged) for 40 days. During the 40 days the soil was allowed to air-dry and was rewetted in cycles of about 5 days. At the end of this reaction period, metal solubility was measured (by atomic absorption spectrometry and direct current plasma spectrometry) at the initial soil pH and at decreased pH values which were induced by addition of small aliquots of acid. As expected, solubility of added Pb, Zn, and Cu increased with a decrease in pH. Furthermore, the results showed that the solubility relationship with pH was similar in all non-calcareous soils. This suggests that metal solubility may be controlled by similar soil components, presumably involving soil characteristics such as pH, organic matter content, and soil mineralogy. For each metal, an approximate pH value was found at which solubility deviated from the solubility of metals when they occur in soils at typical (natural) values. This pH was about (pH+/-0.2): 5.2 for Pb, 6.2 for Zn, and 5.5 for Cu. Thus, pH values below these thresholds may enhance metal mobility, biological availability and toxicity in soils. Metals dissolved at higher pH in the calcareous soil (18.8 g kg(-1) inorganic carbon, initial pH 8.2). In a calcareous soil, a significant fraction of these metals react with carbonates, and decreased pH results in much higher metal dissolution. Yet, metal solubility in soils is not determined by the formation and dissolution of single metal compounds.     

Sorption of copper, zinc and lead on soil mineral phases

Soil mineral phases play a significant role in controlling heavy metal mobility in soils. The effective study of their relation needs the integrated use of several analytical methods. In this study, analytical electron microscopy analyses were combined with sequential chemical extractions on soils spiked with Cu, Zn and Pb. Our aims were to study the metal sorption capacity of soil mineral phases and the effect of presence of iron oxide and carbonate on this property of soil minerals. Copper and Pb were found to be characterized by higher and stronger sorption on the studied samples than Zn. Only the former two metals showed significant differences in their immobilized metal amounts on the studied samples and soil mineral particles. Highest metal amounts were sorbed on the swelling clay mineral particles (smectites and vermiculites), but iron-oxide phases may also have similar lead sorption capacity. Alkaline conditions due to the carbonate content of soils resulted both in increased sorption on the mineral particles for Cu and in enhanced role of precipitation for all the studied metals. On the other hand, the intimate association of phyllosilicates and iron resulted in significant increase in metal sorption capacity of the given particle. The results of sequential extractions could be successfully completed by the analytical electron microscopy analyses for studying the sorption capacity of discrete mineral particles. Their integrated use helps us in better understanding the heavy metal-mineral interactions in soils.     

Non-enhanced phytoextraction of cadmium,zinc, and lead by high-yielding crops

Heavy metal soil contamination from mining and smelting has been reported in several regions around the world, and phytoextraction, using plants to accumulate risk elements in aboveground harvestable organs, is a useful method of substantially reducing this contamination. In our 3-year experiment, we tested the hypothesis that phytoextraction can be successful in local soil conditions without external fertilizer input. The phytoextraction efficiency of 15 high-yielding crop species was assessed in a field experiment performed at the Litavka River alluvium in the P?íbram region of Czechia. This area is heavily polluted by Cd, Zn, and Pb from smelter installations which also polluted the river water and flood sediments. Heavy metal concentrations were analyzed in the herbaceous plants’ aboveground and belowground biomass and in woody plants’ leaves and branches. The highest Cd and Zn mean concentrations in the aboveground biomass were recorded in Salix x fragilis L. (10.14 and 343 mg kg^?1 in twigs and 16.74 and 1188 mg kg^?1 in leaves, respectively). The heavy metal content in woody plants was significantly higher in leaves than in twigs. In addition, Malva verticillata L. had the highest Cd, Pb, and Zn concentrations in herbaceous species (6.26, 12.44, and 207 mg kg^?1, respectively). The calculated heavy metal removal capacities in this study proved high phytoextraction efficiency in woody species; especially for Salix × fragilis L. In other tested plants, Sorghum bicolor L., Helianthus tuberosus L., Miscanthus sinensis Andersson, and Phalaris arundinacea L. species are also recommended for phytoextraction.     

Mechanisms of lead, copper, and zinc retention by phosphate rock

The solid-liquid interface reaction between phosphate rock (PR) and metals (Pb, Cu, and Zn) was studied. Phosphate rock has the highest affinity for Pb, followed by Cu and Zn, with sorption capacities of 138, 114, and 83.2 mmol/kg PR, respectively. In the Pb-Cu-Zn ternary system, competitive metal sorption occurred with sorption capacity reduction of 15.2%, 48.3%, and 75.6% for Pb, Cu, and Zn, respectively compared to the mono-metal systems. A fractional factorial design showed the interfering effect in the order of Pb>Cu>Zn. Desorption of Cu and Zn was sensitive to pH change, increasing with pH decline, whereas Pb desorption was decreased with a strongly acidic TCLP extracting solution (pH = 2.93). The greatest stability of Pb retention by PR can be attributed to the formation of insoluble fluoropyromorphite [Pb(10)(PO(4))(6)F(2)], which was primarily responsible for Pb immobilization (up to 78.3%), with less contribution from the surface adsorption or complexation (21.7%), compared to 74.5% for Cu and 95.7% for Zn. Solution pH reduction during metal retention and flow calorimetry analysis both supported the hypothesis of retention of Pb, Cu, and Zn by surface adsorption or complexation. Flow calorimetry indicated that Pb and Cu adsorption onto PR was exothermic, while Zn sorption was endothermic. Our research demonstrated that PR can effectively remove Pb from solutions, even in the presence of other heavy metals (e.g. Cu, Zn).     

堆肥和腐殖酸对土壤锌铅赋存形态的影响

通过实验室土壤培养实验,研究2种有机物质——腐殖酸和堆肥,单独或者复合应用对土壤中铅锌形态转化的影响。经过1～3个月的培养,发现单独添加腐殖酸和堆肥均可以显著改变土壤中Zn、Pb形态转化,使它们从容易被植物吸收利用的交换态和碳酸盐结合态向难以被植物吸收利用的有机结合态和残渣态转化。与对照相比,单独添加10%堆肥和5%腐殖酸并培养1～3个月后,导致土壤交换态Zn比重分别由38%～51%下降到14%～21%和26%～46%;铁锰氧化物结合态Zn比重分别由23%～34%提高到33%～56%和26%～45%;碳酸盐结合态Pb比重分别由12%～25%下降到1%～15%和2%～15%;残渣态Pb比重分别由12%～14%提高到32%～45%和20%～23%。其他结合态的Zn和 Pb比重也有不同程度的变化。说明堆肥和腐殖酸均可以固定土壤中的Zn和 Pb。而当两者一起使用时,可以中和它们各自所引起土壤pH的变化,而对重金属固定效率更明显增强。研究还发现,不管是腐殖酸还是堆肥,对Pb的固定效果均好于对Zn的固定。     

Computational spectroscopic study of copper, cadmium, lead and zinc interactions in the environment

Molecular modelling has been used to investigate the interactions of various heavy metals, in order to understand and possibly to control the nature and behaviour of metals, especially in the aquatic environment. The interactions of copper, cadmium, lead and zinc with organic acids were studied using density functional theory (DFT) calculations. Carboxylic acid was used as a model molecule. The structure of each metal carboxylate was optimized and the vibrational spectrum calculated. The results indicate that there is a shift in the calculated v_S(C=O) of metal carboxylates compared with that of carboxylic acid. It was also found that hexaaqua structures of both cadmium and zinc are stable whereas those of copper and lead are not. Furthermore, dipole moment calculations indicate that cadmium carboxylate dihydrate is more representative of cadmium interactions in the aquatic environment. Moreover, hexaaquo cadmium could further interact with surrounding molecules in the aquatic environment.     

Earthworms as biological monitors of cadmium, copper, lead and zinc in metalliferous soils

Earthworms (Lumbricus rebellus and Dendrodrilus rubidus) were sampled from one uncontaminated and fifteen metal-contaminated sites. Significant positive correlations were found between the earthworm and 'total' (conc. nitric acid-extractable) soil Cd, Cu, Pb and Zn concentrations (data log1) transformed). The relationships were linear, and the accumulation patterns for both species were similar when a single metal was considered, even though there were species difference in mean metal concentrations. Generally, the earthworm Cd concentration exceeded that of the soil; by contrast, the worm Pb concentration was lower than the soil Pb concentration in all but one (acidic, low soil Ca) site. Our observations suggest that Cu and Zn accumulation may be physiologically regulated by both species. Total-soil Cd explained 82-86% of the variability (V2) in earthworm Cd concentration; 52-58% of worm Pb and worm Zn concentrations were explained by the total-soil concentrations of the respective metals. Total-soil Cu explained only 11-32% of the worm Cu concentration. The effect of soil pH, total Ca concentration, cation-exchange capacity (CEC) and organic carbon on metal accumulation by L. rubellus and D. rubidus was investigated by multiple regression analysis. Soil pH (coupled with CEC) and soil Ca had a major influence on Pb accumulation (V2 of worm Pb increased to 77-83%), and there was some evidence that Cd accumulation may be suppressed in extremely organic soils. The edaphic factors investigated had no effect on Cu or Zn accumulation by earthworms. In the context of biomonitoring, it is proposed that earthworms have a potential in a dual role: (1) as 'quantitative' monitors of total-soil metal concentrations (as shown for Cd); and (2) as estimators of 'ecologically significant' soil metal, integrating the effects of edaphic factors (as shown for Pb).     

Removal of lead and zinc ions from aqueous solutionusing Amasya zeolites from Turkey

A 3-D Eulerian-Lagrangian approach to moving vehicles is presented that takes into account the traffic-induced flow rate and turbulence. The method is applied to pollutant dispersion in an individual street canyon and a system of two street canyons forming a perpendicular intersection. The approach is based on computational fluid dynamics (CFD) calculations using a Eulerian approach for continuous phase and a Lagrangian approach for moving vehicles. The wind speed was assigned values of 4, 7 and 12 m/s. One-way and two-way traffic with different traffic rates per lane is considered. In the case of the intersection, a longitudinal wind direction was assumed. Predictions show differences in the pollutant dispersion in the case of one-way and two-way traffic.     

锌精炼铅塔燃烧系统烟气温度模糊控制研究

针对锌精馏铅塔动态过程中的非线性、非最小相位特征、不稳定性、时滞和负荷干扰,基于模糊控制策略下给出了锌精馏铅塔燃烧系统新的控制方法.运用模糊控制系统对锌精馏铅塔的烟气温度进行仿真研究和实时控制结果表明,该研究所设计的模糊控制器能够克服许多干扰因素,产生了良好的控制效果.     

Growth and metal accumulation in vetiver and two Sesbania species on lead/zinc mine tailings

The lead (Pb)/zinc (Zn) tailings contained high concentrations of heavy metals (total Pb, Zn, Cu and Cd concentrations 4164, 4377, 35 and 32 mg kg(-1), respectively), and low contents of major nutrient elements (N, P, and K) and organic matter. A field trial was conducted to compare growth performance, metal accumulation of Vetiver (Vetiveria zizanioides) and two legume species (Sesbania rostrata and Sesbania sesban) grown on the tailings amended with domestic refuse and/or fertilizer. It was revealed that domestic refuse alone and the combination of domestic refuse and artificial fertilizer significantly improved the survival rates and growth of V. zizanioides and two Sesbania species, especially the combination. However, artificial fertilizer alone did not improve both the survival rate and growth performance of the plants grown on tailings. Roots of these species accumulated similar levels of heavy metals, but the shoots of two Sesbania species accumulated higher (3-4 folds) concentrations of Pb, Zn, Cu and Cd than shoots of V. zizanioides. Most of the heavy metals in V. zizanioides were accumulated in roots, and the translocation of metals from roots to shoots was restricted. Intercropping of V. zizanioides and S. rostrata did not show any beneficial effect on individual plant species, in terms of height, biomass, survival rate, and metal accumulation, possibly due to the rather short experimental period of 5 months.     

Mayfly larvae (Baetis rhodani and B. vernus) as biomonitors of trace metal pollution in streams of a catchment draining a zinc and lead mining area of Upper Silesia,Poland

Larvae of two Baetis species were used to investigate spatial and temporal variability in the bioavailabilities of cadmium, copper, lead, zinc and iron in the river Biala Przemsza and its tributaries draining an area of lead and zinc mining in Upper Silesia, Poland. Accumulated metal concentrations were measured in April, May, August and November 2000. Both species indicated significant local geographical variability in availabilities of zinc, iron, lead and cadmium, but not copper. Accumulated concentrations of lead, zinc and cadmium confirmed the high general contamination of the Biala Przemsza system by these three trace metals. Larvae showed little seasonal variation in concentrations of cadmium, copper, lead and iron. Accumulated zinc concentrations were low in Baetis rhodani in August, perhaps as a result of insufficient time for high concentrations to accumulate since hatching of the larvae. Samples collected in August most nearly matched criteria of the greatest availability of larvae for collection and their size homogeneity, minimising the possibilities of any effect of differential larval size and/or age on accumulated metal concentrations. Mayfly larvae are members of a suite of potential stream biomonitors in Central Europe, which together can provide information on the different sources of bioavailable trace metals present in aquatic ecosystems.