Lead and zinc in a contaminated pasture at minera,North Wales,and their impact on productivity and organic matter breakdown

Pb and Zn levels were determined in upper and lower soil horizons and vegetation at 14 sites along a 75 m transect in a pasture adjacent to an abandoned Pb/Zn mine spoil in North Wales, and in an uncontaminated control site 500 m from the transect.Water-soluble, 0.1 M calcium chloride, 0.5 M acetic acid, and nitric/perchloric acid extractable levels of soil Zn and Pb were estimated. Depth of accumulated litter and loss on ignition were also measured and estimates of soil humus content were obtained for all transect sites. Dry matter productivity was assessed during Summer 1978 in an exclosure adjacent to the transect.Loosely bound soil Zn and Pb levels increased in upper and lower horizons in soils up to 6 and 8 m respectively from the mine spoil. There was little or no water-extractable lead. Amounts of the more tightly bound forms of both metals declined exponentially from the mine spoil at the transect origin, a pattern of distribution suggesting that erosion by wind is almost exclusively the cause of pollution of adjacent pasture sites.With the exception of water-soluble metals, vegetation Pb and Zn levels were markedly lower than zinc levels. Apart from water-soluble Pb, metal levels in vegetation declined exponentially with distance along the transect.Productivity was very low on the toxic soils adjacent to the spoil but rose to ca. 5000 kg ha^?1 y^?1 10 m from the spoil and remained fairly constant thereafter. Litter was absent on the most and the least toxic soils, reached a peak of 3 cm depth at 6 m and declined steadily thereafter, none being recorded beyond 40 m. Loss on ignition and soil humic matter in upper soil horizons peaked at 387 and 230 mg g^?1 air dried soil 16 m along the transect. Lower soil horizons had maximum values of 224 (loss on ignition) and 100 mg g^?1 air dried soil (soil humic matter) 8 m from the spoil. In both horizons both declined steadily with increasing distance from the spoil, but greater amounts were recorded in all transect soils than in the control site.Sensitivity to metal contamination increased in the sequence; productivity < litter accumulation < soil organic matter breakdown < soil humus decomposition.     

History,ecology and physical and chemical nature of two metalliferous spoil tips in South‐West England

The ecology and nature of metalliferous spoil tips in the Tamar Valley area of South‐West England is discussed. The tips, which resulted from metal extraction during the late 19th and early 20th century, cause contamination of plants, animals, and ecosystems. The amount of vegetation cover is reduced whilst a diversity of genera occurs.     

Some aspects of tissue accumulation and tolerance to available heavy metal ions by Rubus Fruticosus L., A Colonizer of spoil tips in S.W. England

In the Tamar Valley of South West England are a number of metalliferous spoil tips. The tips have little vegetation due mainly to a substratum possessing adverse characteristics—a high concentration of metalions, a low nutrient status, rapid drainage and pronounced localised instability. Many of the tips have been colonised by Rubus fruticosus L. (blackberry), and its ecology is described. Clonal plants were utilised in field and glasshouse experiments, and metal uptake examined. Rubus fruticosus L. was noted to be tolerant of high concentrations of metal ions, and also to accumulate them. A trend towards xeromorphism is described.     

Accumulation of zinc, cadmium and lead by field populations of Lemanea

A study has been made of the concentrations of zinc, cadmium and lead in populations of the red alga Lemanea growing in fast-flowing rivers in Britain, France. Germany, Ireland and Sardinia (Italy). The sites were selected to provide a wide range of aqueous concentrations of these metals. Many of the sites are influenced by past or present mining activities and Lemanea was found at aqueous concentrations of zinc up to 1.16 mg 1⁻¹. In contrast to previous studies with filamentous green algae, no evidence could be found to support the hypothesis that populations differ genetically in their ability to tolerate these heavy metals. Samples of alga consisted of pooled 2 cm long terminal tips of filaments detached from approx. 1 cm² rock surface. Significant positive correlations were found between the logarithm of the mean concentration of zinc, cadmium and lead in four such samples collected from within 10 m reaches at 59 sites and the logarithm of the concentration of each metal in both unfiltered and filtered water. The enrichment ratios for each metal decreased with increasing aqueous metal concentrations. Although the aqueous concentrations of the three metals were strongly intercorrelated, differences in the ratio of metal concentrations were reflected in the composition of Lemanea filaments. The results suggest that high levels of calcium (and/or magnesium) result in decreased uptake of zinc. Intensive sampling from a single population showed that part of the zinc content of filaments is sensitive to short-term fluctuations in concentrations in the surrounding water. In the particular population studied this was about 20%; a similar percentage could be eluted in the laboratory with EDTA. Transplants of Lemanea were made between reaches with different aqueous concentrations of zinc and in all cases the zinc concentration in filament tips increased or decreased to stabilise at a concentration similar to that in filaments native to the reach. It is suggested that chemical analyses of natural or transplanted populations of Lemanea could provide a valuable aid in monitoring contamination of rivers by zinc, cadmium or lead.     

Heavy metal accumulation and tolerance in plants from mine tailings of the semiarid Cartagena-La Unión mining district (SE Spain)

Mine tailings are a characteristic of landscapes where mineral extraction has occurred. These tailings usually contain high heavy metal concentrations and have low fertility. In arid and semiarid zones, erosion may be an additional problem. The removal of these tailings is often impractical due to their large volumes. Therefore, a need exists to develop in situ low cost technologies to effect surface stabilization. The use of vegetation can be an attractive option, since there are some native plant species that can colonize parts of these polluted sites unaided. Some edaphic factors were investigated, including heavy metal concentrations, in three mine tailings from a semiarid mining zone in Southeast Spain. High total metal concentrations were found: 5000-8000 mg/kg for lead and 7600-12300 mg/kg for zinc. Two of these mine tailings had pH values between 6 and 7, while the other was acidic, with a pH of 2.5. Metal solubility was pH dependent, with more than 10% of the total zinc soluble in the acid substrate and less than 1% in the neutral substrates. The metal concentrations (copper, lead and zinc) in shoots of native vegetation colonizing in these sites were studied. No species of hyperaccumulators were found. The highest concentrations were found in Zygophyllum fabago, with 530 mg/kg zinc, Helichrysum decumbens with 390 mg/kg lead, and Tamarix sp. with 11 mg/kg copper. An analysis of the rhizospheric soil of these plants indicated that Lygeum spartum grew in pH 3 soil and had low metal concentration in shoots (40 mg/kg zinc and 41 mg/kg lead).     

Records and sources of metal pollutants in a dated Loch Lomond sediment core

Lead, zinc, copper, chromium, arsenic and cadmium were measured in a sediment core from southern Loch Lomond for which ²¹⁰Pb dating indicated a sedimentation rate of 22±2 mg/cm²/yr corresponding to a mean accumulation rate of 0.36 mm/yr.While copper and chromium were enriched to only a minor extent, the lead, zinc, arsenic and cadmium concentrations were markedly enhanced in upper sections. Increasing anthropogenic input associated with industrial activity centred on Glasgow seems responsible for the vertical distribution of lead, zinc and cadmium but a high 0–1 cm level of arsenic (474 μg/g), strongly correlated with enhanced iron content in the surface oxidising layer of sediment, appears attributable to post-depositional diagenetic mobilisation and upward migration in the reducing zone of the sediment column.Leaching, using CH₃CO₂H/NH₂OH·HCl, released over 90% and 80% of the common metal pollutants, lead and zinc, from surface sediment. Onset of an approximately tenfold increase in lead and zinc concentrations above “background” levels of 13±2 μg/g and 47±13 μg/g to upper section levels of 140–170 μg/g and 450–460 μg/g respectively was placed at late-18th century, in accord with the records of the commencement of significant industrial activity in the Glasgow area. Current anthropogenic fluxes (μg/cm² /yr) of lead (2.51±0.34) and zinc (8.84±1.20) to the sediment are in agreement with recent atmospheric deposition data for the adjoining Clyde Sea Area.The general concordance between anthropogenic metal fluxes to Loch Lomond sediment and atmospheric deposition fluxes endorses the potential usefulness of Loch Lomond sediment data to the resolution of pollution sources in the adjoining sea lochs and firth of the Clyde Sea Area, illustrated here through consideration of the comparative distribution of chromium in relation to its historical use.     

水泥固化稳定重金属污染土的工程性质试验研究

随着社会的快速发展,因工业生产以及人类活动引起的地基土重金属污染现象越来越严重。地基土受到重金属污染后,其工程性质会发生改变。固化稳定法是处理重金属污染土地基的常用方法之一。以人工制备的铅或锌重金属污染土为研究对象,通过系统的室内试验,着重研究水泥固化稳定重金属污染土的工程性质。试验结果表明,土体受到污染后,其强度降低;掺入水泥固化稳定的重金属污染土的强度随水泥掺入量以及养护龄期的增加显著增大。通过试验还发现,较低浓度重金属离子的存在可以促进水泥固化土抗剪强度的提高。     

Lead and zinc in the Wallsend Burn, an urban catchment in Tyneside, UK

This paper examines lead and zinc concentrations in topsoils and stream sediments of public access areas in an urban catchment in Tyneside, UK. It examines the extent and severity of metal contamination, explores spatial patterns in relation to urban and industrial development, and makes inferences about potential metal mobility. Total and acetic-acid extractable lead and zinc concentrations, organic content and pH were determined on 121 topsoil and 22 stream sediment samples using standard laboratory procedures. Using the lowest trigger thresholds for total lead and zinc, almost 75% and 91%, respectively, of topsoil samples were classified as contaminated; proportions were rather lower for acetic acid extractable metals. Similarly, approximately 45% and 95% of stream sediment samples were contaminated with lead and zinc, respectively. The spatial distribution of metal concentrations was characterized by a hotspot pattern, with highest values in central and southern parts of the catchment where there is a long urban and industrial history. The potential mobility of zinc is considerably greater than that of lead in both topsoils and stream sediments, and for both metals is slightly higher in the stream sediments than in the topsoils; both of these differences are statistically significant (P < 0.05). The implications of the findings in this paper for assessment and monitoring of metal contaminated areas are explored.     

Natural variation of copper,zinc, cadmium and selenium concentrations in Bembicium nanum and their potential use as a biomonitor of trace metals

Copper, zinc, cadmium and selenium were measured in the gastropod mollusc Bembicium nanum at two uncontaminated locations, Jervis Bay and Rosedale, NSW, to determine natural variability of metals associated with gender, mass, shore position and temporal variability. Trace metals were also measured in B. nanum at three industrialised locations to determine the accumulation of trace metals in contaminated environments.Copper, zinc, cadmium and selenium concentrations were not significantly different between male and female B. nanum. No significant relationships were found between zinc, cadmium and selenium concentrations and mass. There was a significant relationship between copper concentration and mass but only 19% of the variation was explained by mass. Generally inherent variability within samples had a greater influence than gender or variations in mass on trace metal concentrations.No trend was found in cadmium and selenium concentrations with variation in shoreline position. Copper and zinc concentrations increased further away from the low tide mark, with a decrease in metal concentrations at the furthest site from the water. Variability in metal concentrations is attributable to variations in food source, food availability and different immersion times.Copper, zinc, cadmium and selenium concentrations varied over a 12-month period. Copper, cadmium and selenium were taken up and lost over time, as metal body burden followed the same trend as metal concentrations. Zinc concentrations were influenced by mass. Copper and cadmium concentrations fluctuated throughout the 12-month period but with no clear seasonal trends. Selenium concentrations peaked in spring (October), with concentrations remaining uniform over the other months. These differences in mean concentrations between months were most likely due to inherent trace metal variability associated with differences in food availability and changes in metabolic rates associated with changes in temperature during the study period.Measurement of trace metals in B. nanum at contaminated sites showed that B. nanum accumulates metals in response to contamination.B. nanum meets most of the requirements to be a biomonitor of trace metal contamination as they are abundant, sedentary, easy to identify, provide sufficient tissue for analysis, tolerate high concentrations of pollutants and they accumulate trace metals in response to contamination. However, as trace metal concentration can vary with mass, shoreline position and temporally, care must be taken to collect individual organisms with similar mass from similar shoreline positions and times.     

Lead,cadmium, and arsenic residues in animal tissues in relation to those in their surrounding habitat

The relationships of the residues of lead, cadmium, and arsenic in animal tissues to those in surrounding vegetation and soil were determined in a natural habitat representing a wide range of such residues. The samples studied were selected from 18 different locations. Analyses were performed on a total of 113 animals, 332 plant specimens (representing 33 species), and 408 soil samples (taken at different depths). For the purpose of evaluating relationships, the samples from each location were averaged and reported as parts per million on a dry weight basis. The average lead residues from different locations ranged from 1.4–9.2 ppm in the liver, 45–195 in bones, 4–283 in vegetation, and 15–1399 in soil samples. The cadmium contents ranged from 1–27 ppm in the liver, 3–77 in bones, 0.5–5 in vegetation, and 1–10 in soil. The arsenic contents in different components of the ecosystem varied with an average of 1–9 ppm in liver, 0.6–94 in vegetation, and 7–655 in soil samples. The soil residues varied considerably according to the depth of sampling. Little variation was noted in different species of vegetation or in soil and vegetation samples according to the time and year of sampling.Statistical analyses performed on the averages indicated a significant correlation between vegetation and soil residues for all three elements, and also between animal to vegetation and animal to soil cadmium residues. Multiple linear correlations for all elements in soil, vegetation, and animal tissues were determined. The results indicated a possibility of an increase in cadmium in animal tissues depending upon the increased residues of this metal in the environment.     

Assessment of fly ash-aided phytostabilisation of highly contaminated soils after an 8-year field trial: part 1. Influence on soil parameters and metal extractability

Sustainable management of large surface areas contaminated with trace elements is a real challenge, since currently applied remediation techniques are too expensive for these areas. Aided phytostabilisation appears to be a cost efficient technique to reduce metal mobility in contaminated soils and contaminated particle spread. In this context, this study aimed at evaluating the long-term efficiency of aided phytostabilisation on former agricultural soils highly contaminated with trace elements. The influence of afforestation and fly ash amendments to reduce metal mobility was investigated. Before being planted with a tree mix, the study site was divided into three plots: a reference plot with no amendment, the second amended with silico-aluminous fly ash and the third with sulfo-calcic fly ash. After eight years, some soil physico-chemical parameters, including cadmium (Cd), lead (Pb) and zinc (Zn) extractability were modified. In particular, pH decreased on the whole site while organic carbon content increased. The alteration of these parameters influencing trace element mobility is explained by afforestation. Over time, concentrations of CaCl₂-extractable metals increased and were correlated with the soil pH decrease. In the amended soils, extractable Cd, Pb and Zn concentrations were lower than in the reference soil. The results indicated that the two fly ashes buffered natural soil acidification due to vegetation development and limited trace element mobility and thus could limit their bioavailability. For long-term phytostabilisation, special attention should be focused on the soil pH, metal mobility and phytoavailability analysis.     

Assessing the fate of antibiotic contaminants in metal contaminated soils four years after cessation of long-term waste water irrigation

Spreading of urban wastewater on agricultural land may lead to concomitant input of organic and inorganic pollutants. Such multiple pollution sites offer unique opportunities to study the fate of both heavy metals and pharmaceuticals. We examined the occurrence and fate of selected antibiotics in sandy-textured soils, sampled four years after cessation of 100 years irrigation with urban wastewater from the Paris agglomeration. Previous studies on heavy metal contamination of these soils guided our sampling strategy. Six antibiotics were studied, including quinolones, with a strong affinity for organic and mineral soil components, and sulfonamides, a group of more mobile molecules. Bulk samples were collected from surface horizons in different irrigation fields, but also in subsurface horizons in two selected profiles. In surface horizons, three quinolones (oxolinic acid, nalidixic acid, and flumequine) were present in eight samples out of nine. Their contents varied spatially, but were well-correlated one to another. Their distributions showed great similarities regarding spatial distribution of total organic carbon and heavy metal contents, consistent with a common origin by wastewater irrigation. Highest concentrations were observed for sampling sites close to irrigation water outlets, reaching 22 μg kg⁻¹ for nalidixic acid. Within soil profiles, the two antibiotic groups demonstrated an opposite behavior: quinolones, found only in surface horizons; sulfamethoxazole, detected in clay-rich subsurface horizons, concomitant with Zn accumulation. Such distribution patterns are consistent with chemical adsorption properties of the two antibiotic groups: immobilization of quinolones in the surface horizons ascribed to strong affinity for organic matter (OM), migration of sulfamethoxazole due to a lower affinity for OM and its interception and retention in electronegative charged clay-rich horizons. Our work suggests that antibiotics may represent a durable contamination of soils, and risks for groundwater contamination, depending on the physicochemical characteristics both of the organic molecules and of soil constituents.     

Lead isotope ratio measurements by ICP-QMS to identify metal accumulation in vegetation specimens growing in mining environments

The use of variations in stable Pb isotope ratios has become a well-established diagnostic technique for characterising sources of lead contamination. In this work, lead isotope ratios in mining wastes (lead content 320-130,000 mg kg-1) and vegetation specimens (lead concentration 7-650 mg kg-1) have been determined by inductively coupled plasma quadrupole-based mass spectrometry (ICP-QMS) in order to investigate lead bioaccumulation in Buddleia davidii growing on wastes from two abandoned Pb/Zn mining areas in Spain. The accuracy of the isotope ratio measurements was evaluated by analysing a certified isotopic standard NIST SRM 981. Good agreements were obtained between the lead isotope ratios measured and the certified values (deviations within 0.01-0.2%). The results indicate that the lead isotopic ratios in vegetation samples collected in the mining areas differed from those of a specimen from an uncontaminated site (control sample). However, close lead isotope ratio values were found between vegetation specimens and mining tailings. Therefore, the results suggest that lead in the collected vegetation specimens is most likely related to the influence of mining activities rather than to other sources like past leaded-petrol emissions.     

Animal excrement: a potential biomonitor of heavy metal contamination in the marine environment

To assess the feasibility of using animal excrement to biomonitor the extent of heavy metal contamination in the marine environment, concentrations of mercury (Hg), lead (Pb), copper (Cu) and zinc (Zn) in the fresh excrement of seabirds and marine mammals, along with other biomaterials, from the Arctic, Antarctica (West and East), and Xisha Archipelago of the South China Sea were determined. Results show that the excrement of marine animals at higher trophic levels generally contained high levels of Hg, demonstrating the biomagnification of Hg through food chains in different remote regions. Significant variations in metal accumulation in the excrements were observed among the distinctive geographical areas, with the highest Hg concentration in Xisha Archipelago and the highest Pb concentration in the Arctic, which reflects different levels of air metal pollution at various sampling locations. Concentrations of Cu in the excrements primarily correlate to the geochemical background levels in the regions. High Cu concentrations were found near the Great Wall Station in West Antarctica where a copper mineralized belt exists. No clear spatial variation pattern was found for Zn accumulation in the excrement. This study shows that animal excrement can be used as bioindicators for the level of metal contamination in the marine environment, with the advantages of easy sampling, accurate detection (i.e., with high levels of metal accumulation), and reconstructing historical metal contamination trends by long-term monitoring of sedimentary excrements.     

Transfer of soil contaminants to home-produced eggs and preventive measures to reduce contamination

Uptake studies have shown that chickens foraging on soils contaminated with environmental pollutants accumulate these compounds into their eggs. Home-produced eggs thereby show higher contamination levels than commercially produced eggs. It was the aim of this study to identify the major source of two environmental pollutants in home-produced eggs, i.e. dioxins and lead, to formulate preventive measures to reduce the contamination levels of such eggs, and to assess the feasibility of the formulated measures in terms of the perception and behavior of private egg producers towards such measures. The major source of dioxins and lead in eggs, i.e. the soil, was identified by transfer calculations of the pollutants from the feed and soil towards eggs. Preventive measures to reduce soil intake or geophagy and hence egg contamination levels, were formulated and their feasibility evaluated through interviews with private chicken owners. The results show that a paved surface inside the henhouse, an indoor feeding place and providing a sufficient surface area per chicken were considered the most appropriate in terms of feasibility and willingness to apply the measures by the private chicken owners. To enhance the effect of the measures, a combination of measures supported and promoted at policy level is considered as a good strategy to reduce contamination levels in home-produced eggs.     

Spatial and temporal variations in Pb concentrations and isotopic composition in road dust, farmland soil and vegetation in proximity to roads since cessation of use of leaded petrol in the UK

Results are presented for a study of spatial distributions and temporal trends in concentrations of lead (Pb) from different sources in soil and vegetation of an arable farm in central Scotland in the decade since the use of leaded petrol was terminated. Isotopic analyses revealed that in all of the samples analysed, the Pb conformed to a binary mixture of petrol Pb and Pb from industrial or indigenous geological sources and that locally enhanced levels of petrol Pb were restricted to within 10 m of a motorway and 3 m of a minor road. Overall, the dominant source of Pb was historical emissions from nearby industrial areas. There was no discernible change in concentration or isotopic composition of Pb in surface soil or vegetation over the decade since the ban on the sale of leaded petrol. There was an order of magnitude decrease in Pb concentrations in road dust over the study period, but petrol Pb persisted at up to 43% of the total Pb concentration in 2010. Similar concentrations and spatial distributions of petrol Pb and non petrol Pb in vegetation in both 2001 and 2010, with enhanced concentrations near roads, suggested that redistribution of previously deposited material has operated continuously over that period, maintaining a transfer pathway of Pb into the biosphere. The results for vegetation and soil transects near minor roads provided evidence of a non petrol Pb source associated with roads/traffic, but surface soil samples from the vicinity of a motorway failed to show evidence of such a source.     

Plant-available lead and other metals in British garden soils

An account is given of an investigation of the fertility status and heavy metal content of garden soils in England and Wales and the availability to and uptake of lead by radish generally, and by potatoes in two villages of contrasting epidemiological history. Intentional interference (i.e., cultivation) of gardens by man has resulted in a generally high level of fertility, but inadvertent additions of lead and other metals have resulted in many garden soils being contaminated. There are regional differences in fertility but not in heavy metal content. In rural areas, uncontaminated soils were associated with allotments and new gardens, and lead contamination was identified in urban and industrial areas as a result of pollution from vehicle exhausts, industry, mining and miscellaneous sources. Mature gardens in rural areas were also contaminated by lead and evidence is presented to support a hypothesis of increasing pollution with time, perhaps due to coal ash from chimneys. Radish absorbed soil lead and certain gardens produced plants the lead content of which was close to or above the legal limit of 2 mg/kg Pb. Potato was a weaker absorber of lead but plant contents still reflected lead contamination of soil. Consumption of vegetables from contaminated gardens could account for an appreciable proportion of the maximum safe daily intake of lead.     

The contribution of glomalin-related soil protein to Pb and Zn sequestration in polluted soil

The distribution of lead and zinc in glomalin-related soil protein (GRSP), a widespread glycoprotein presumably produced by arbuscular mycorrhizal fungi (AMF) in soil, and in some other soil fractions (soil organic matter - [SOM], carbonates, phosphates, etc.) was studied in soils from an area near a lead smelter that differed in SOM, carbonates and heavy metal (HM) content. Total GRSP represented 5.4-21.2% of the SOM and was positively correlated with the soil Pb and Zn concentrations (r=0.57 and 0.66, p=0.007 and p=0.001 for Pb and Zn, respectively). Pb and Zn were predominantly bound to carbonates and organic matter. The amount of lead bound to GRSP varied between 0.69 and 23.4 mg g(-1) DW GRSP which is 0.8-15.5% of the total soil Pb. The amount of GRSP-bound metal was positively correlated with the total concentration in the case of Pb (r=0.90, p=0.000) but the opposite was found for Zn (r=-0.41, p=0.048), indicating that GRSP predominantly binds Pb. The percentages of HM-GRSP in HM-SOM were variable and were not correlated with SOM content.     

优先流作用下的胶体-重金属共迁移试验研究

土壤中的重金属污染物大部分源自外界的工、农业排放,地表土层是重金属迁移至地下的必经途径。由于干缩和动植物活动,地表土中存在大孔隙,形成污染物运移的优势通道,在一些情况下,这些通道是重金属穿过包气带向下迁移的唯一途径。针对胶体对重金属具有较大吸附能力且在优先流条件下具有移动性,从而可能加快重金属污染物迁移这一问题,通过等温吸附试验确定了上海表层褐黄色粉质黏土与土壤胶体对重金属镉、铅的吸附特征,制备具有可重复性优先流特征的试验土柱,进行优先流条件下胶体-重金属共迁移土柱淋滤试验,分析得到胶体-重金属共迁移规律。试验结果表明,胶体对重金属的吸附能力明显高于粉质黏土。有胶体情况下,镉出流量是无胶体情况下镉出流量的1.49倍,铅的出流量是无胶体情况下的33.88倍,有胶体情况下土上吸附的重金属和孔隙溶液中的重金属浓度都低于无胶体的情况,更多的重金属随胶体向下迁移,优先流条件下胶体明显加快了重金属的迁移。虽然铅的源浓度和淋滤时间都大于镉,但铅的出流量仅约为镉的1/13,由于易发生吸附,铅在土中的迁移能力较弱。     

Lead poisoning combined with cadmium in sheep and horses in the vicinity of non-ferrous metal smelters

The diagnosis of lead poisoning combined with cadmium in sheep and horses living on farmland in the vicinity of non-ferrous metal smelters in Baiyin of Gansu province in China was based on laboratory findings as well as clinical signs. The concentrations of lead, cadmium, copper and zinc in soils, water, forages, feed and blood, hair and tissues of affected sheep and horses were determined in the surroundings of the smelters in Baiyin and controls. Haematological values were also measured. The concentrations of these elements in soils, forages, water and feed were significantly higher than those in the control area (P<0.01). The contents of lead and cadmium were 9.3 and 690 times in forages, respectively, 10 and 35.6 times in feed. The concentrations of lead and cadmium in blood, hair and tissues of the affected sheep and horses were significantly higher than reference values and control animals (P<0.01). The occurrence of anaemia in affected animals belonged to a hypochromic and microcytic pattern. Lead and cadmium intake levels, estimated according to the ingestion rates of forages, illustrates that the apported lead and cadmium through the ingestion of vegetation growing in the closest sites to the smelters were approximately 6.0 mg Pb/kg body wt./day and 1.1 mg Cd/kg body wt./day in horses, 21.4 mg Pb/kg body wt./day and 4.0 mg Cd/kg body wt./day in sheep, surpassing the fatal dosages for horses of 1.7 mg Pb/kg body wt./day and for sheep of 4.4 mg Pb/kg body wt./day and 1.0 mg Cd/kg body wt./day. It is, therefore, suggested that the disease of sheep and horses in this region is caused by lead poisoning combined with cadmium, mainly due to environment heavy metal pollution by industrial activity. Meanwhile, as such levels of contamination in animal food and grain pose a significant potential risk to human health, these results have formed the basis for subsequent research on levels of metal contamination in human tissues from affected populations. Thus, it can be seen that knowledge of lead and cadmium concentrations in livestock in this region is important for assessing the effects of pollutants on domestic animals themselves and contaminant intakes by humans.