An Investigation of the Soil Property Changes and Heavy Metal Accumulation in Relation to Long-term Wastewater Irrigation in the Semi-arid Region of Iran

Concentrations and spatial distribution of Zn, Cu, Cd, and Pb along two landscapes including a wastewater-irrigated area and a control area were determined to assess the impact of long-term wastewater irrigation and landscape properties on heavy metal contamination. Some disturbed and undisturbed soil samples were taken from soil trenches and soil cores, located on three main landscape positions (upper slope, midslope, and lower slope) in northwestern Iran. The investigation showed that the mean concentration of the heavy metals followed the order Zn > Cu > Pb > Cd in the wastewater-irrigated soil and Pb > Zn > Cu > Cd in the control soils. On average, compared to similar positions in the control region, the wastewater-irrigated regions contained 3.0 (midslope) to 4.9 (lower slope), 2.7 (midslope) to 4.6 (lower slope), 3.3 (upper slope) to 4.1 (lower slope), and 1.7 (upper slope) to 2.6 (lower slope) times higher amounts of Zn, Cu, Cd, and Pb, respectively. Significant positive relationships (P < 0.05) were recorded between the heavy metals concentration with <0.002 mm particle-size fraction and organic matter content, the fractions linked to runoff and soil erosion. It is believed that the two soil fractions play a crucial role in the distribution of the metals along the wastewater-irrigated landscape. Despite the significant increase of heavy metals (P < 0.05) in the wastewater-irrigated soils compared with control soils, the concentration of all evaluated metals was below the maximum accepted limits (Zn < 300 mg/kg, Cu < 100 mg/kg, Cd < 5 mg/kg, and Pb < 100 mg/kg), and grouped as “not-enriched” to “moderately-enriched” categories regarding the topsoil enrichment index. Overall, the lower slope was shown to be more contaminated with the heavy metals compared to the other positions.     

The distribution of cadmium,copper, lead,zinc and calcium in the tissues of the earthworm Lumbricus rubellus sampled from one uncontaminated and four polluted soils

Summary The tissue distribution of Cu, Cd, Pb, Zn, and Ca in the earthworm Lumbricus rubellus living in non-polluted and heavy-metal polluted soils was investigated. Cd, Pb and Zn were primarily accumulated within the posterior alimentary canal. As the whole-worm Pb burden increased, the proportion of the metal accumulated within this tissue fraction increased. A similar pattern was found for Zn. By contrast, 70%–76% of the Cd burden was found in the posterior alimentary canal, irrespective of the whole-worm Cd content. The accumulation of Cd, Pb and Zn primarily in the posterior alimentary canal prevents dissemination of large concentrations of these metals into other earthworm tissues, and may thus represent a dextoxification strategy based on accumulative immobilisation. Cu was distributed fairly evenly in the tissue fractions investigated. There was no evidence of sequestration of this metal. The apparent lack of a detoxification strategy may contribute to the well-known susceptibility of earthworms to low environmental Cu concentrations. Indeed, earthworms from the site of highest soil Cu (Ecton) were markedly smaller than those from the other sites sampled. The highest Ca concentrations were found in the anterior alimentary canal, and were related to calciferous gland activity. A large proportion of Ca was also stored as a physiologically available pool in the posterior alimentary canal. Despite huge variations in soil Ca concentrations, the body wall Ca levels were fairly similar in L. rubellus from all the study sites. Thus, L. rubellus may become physiologically adapted to soils of exceptionally low Ca concentration. The observations are discussed in the context of the merits of analysing specific tissues, rather than whole organisms, for the purpose of monitoring metal bioaccumulation.     

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.     

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

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

Biochemical properties of soils of undisturbed and disturbed mangrove forests of South Andaman (India)

Studies on soil quality of mangrove forests would be of immense use in minimizing soil degradation and in adopting strategies for soil management at degraded sites. Among the various parameters of soil quality, biological and biochemical soil properties are very sensitive to environmental stress and provide rapid and accurate estimates on changes in quality of soils subjected to degradation. In this study, we determined the general and specific biochemical characteristics of soils (0-30 cm) of inter-tidal areas of 10 undisturbed mangrove forest sites of S. Andaman, India. In order to determine the effects of disturbance, soils from the inter-tidal areas of 10 disturbed mangrove forest sites were also included in the study. The general biochemical properties included all the variables directly related to microbial activity and the specific biochemical parameters included the activities of extracellular hydrolytic enzymes that are involved in the carbon, nitrogen, sulfur and phosphorus cycles in soil. The pH, clay, cation exchange capacity, Al₂O₃ and Fe₂O₃ levels exhibited minimum variation between the disturbed and undisturbed sites. In contrast, organic C, total N, Bray P and K levels exhibited marked variation between the sites and were considerably lower at the disturbed sites. The study also revealed marked reductions in microbial biomass and activity at the disturbed sites. In comparison to the undisturbed sites, the levels of all the general biochemical parameters viz., microbial biomass C, microbial biomass N, N flush, basal respiration, metabolic quotient (qCO₂), ATP, N mineralization rates and the activities of dehydrogenase and catalase were considerably lower at the disturbed sites. Similarly, drastic reductions in the activities of phosphomonoesterase, phosphodiesterase, ß-g1ucosidase, urease, BAA-protease, casein-protease, arylsulfatase, invertase and carboxymethylcellulase occurred at the disturbed sites due mainly to significant reductions in organic matter/substrate levels. The data on CO₂ evolution, qCO₂ and ATP indicated the dominance of active individuals in the microbial communities of undisturbed soils and the ratios of biomass C:N, ATP:biomass C and ergosterol:biomass C ratios indicated low N availability and the possibility of fungi dominating over bacteria at both the mangrove sites. Significant and positive correlations between soil variables and biochemical properties suggested that the number and activity of soil microorganisms depend mainly on the quantity of mineralizable substrate and the availability of nutrients in these mangrove soils.     

佛山城市典型森林群落土壤重金属分布、流通及枯落物富集特征

富集重金属的枯落物分解可能提高重金属暴露率,增加人体接触健康风险。为了解南方城市土壤重金属在森林生态系统中的分布及流转情况,通过调查研究了佛山市8个典型森林群落土壤及枯落物重金属含量,分析了各森林群落枯落物对不同重金属的富集效应及重金属随枯落物回归土壤流通量。结果表明：1）城市森林各土壤重金属含量在不同典型群落间差异显著（P<0.05）,差异最大为Pb、Cr、Zn,As、Cu、Ni次之,Hg、Cd最小;土层深度（0-20,20-40,40-60 cm）对重金属含量影响显著（P<0.05）,差异最大为Cd、Hg,其次为As、Cu,最小为Zn、Ni、Pb、Cr。整体上,Cd、Hg、As、Pb、Zn在0-20 cm最高,表层富集特征明显,Cr和Ni在40-60 cm最高。2）8个森林群落中阴香-白楸-醉香含笑群落（CMMC）枯落物对8种重金属的综合富集系数（TBCF,66.76）最高,其中以Cd的富集效果最突出,富集系数为44.45,且对Pb、Cu、Zn也相对富集;最低的为黧蒴锥-香椿-樟树群落（CTCC）,综合富集系数（TBCF）为8.09,仅对Cd、Cr、Cu相对富集,对其余重金属富集效应不明显。3）相关分析显示,群落重金属枯落物流通量与0-60 cm土壤重金属平均含量（Cr和Ni除外）无显著相关性。本研究对城市森林建设管理及筛选重金属富集植物及群落具有较强理论及实践意义。     

Characterization of Bacteria in the Rhizosphere Soils of Polygonum Pubescens and Their Potential in Promoting Growth and Cd,Pb, Zn Uptake by Brassica napus

Microbe-enhanced phytoremediation has been considered as a promising measure for the remediation of metal-contaminated soils. In this study, two bacterial strains JYX7 and JYX10 were isolated from rhizosphere soils of Polygonum pubescens grown in metal-polluted soil and identified as of Enterobacter sp. and Klebsiella sp. based on 16S rDNA sequences, respectively. JYX7 and JYX10 showed high Cd, Pb and Zn tolerance and increased water-soluble Cd, Pb and Zn concentrations in culture solution and metal-added soils. Two isolates produced plant growth-promoting substances such as indole acetic acid, siderophore, 1-aminocyclopropane-1-carboxylic deaminase, and solubilized inorganic phosphate. Based upon their ability in metal tolerance and solubilization, two isolates were further studied for their effects on growth and accumulation of Cd, Pb, and Zn in Brassica napus (rape) by pot experiments. Rapes inoculated with JYX7 and JYX10 had significantly higher dry weights, concentrations and uptakes of Cd, Pb, Zn in both above-ground and root tissues than those without inoculation grown in soils amended with Cd (25 mg kg^?1), Pb (200 mg kg^?1) or Zn (200 mg kg^?1). The present results demonstrated that JYX7 and JYX10 are valuable microorganism, which can improve the efficiency of phytoremediation in soils polluted by Cd, Pb, and Zn.     

Factors determining the centrifugal organization of remnant Festuca grassland communities in Alberta

Abstract. This paper describes the species composition of remnant grasslands in the aspen parkland region of Alberta and its relation to soil characteristics and small‐scale disturbance. Our findings are consistent with the centrifugal model of communities with Festuca hallii dominating undisturbed ‘core’ habitat and the composition of more ‘peripheral’ habitats varying in soil properties and in the magnitude of disturbance. Invasive non‐native species are not present in the core habitat and are present only in the disturbed sites, most abundantly in those with the highest soil nitrogen. The centrifugal model, as it applies to these remnant grasslands, differs from its previous application to wetlands and forests in that the core communities are not on the most fertile sites, but on the least disturbed. These findings have implications for the management of prairie remnants to exclude invasive exotic species.     

浙江及邻近地区蛇足石杉依存环境的初步研究

对浙江及邻近地区产的蛇足石杉(Huperzia serratct)7个种群的自然环境进行野外观察,测定了土壤含水量、电导率、有机质含量、pH值,植株和土壤中K、Ca、Mg、Fe、Zn、Cu、Mn、Na、A1、Pb、Cd 11种元素的含量,以及植株中石杉碱甲(HupA)含量。结果表明,蛇足石杉种群多分布于海拔350-1700m的山地密林下或沟谷阴湿土中,郁闭度、年均降雨量、空气相对湿度均较大：环境中土壤含水量为10％-30％,pH值4．57—5．31,电导率0．061—0．385mscm^-1,有机质含量6．18％-9．75％;蛇足石杉对K、Ca、Zn和Na的需要程度较高,对Pb、Cu、Cd3种重金属元素的富集能力较强,在人工栽培中应注意协调各元素的合理配给：蛇足石杉较适宜生长的环境条件为：土壤电导率以及pH值相对较低;郁闭度高,年均降雨量和空气相对湿度较大。基于土壤理化性质,对7个种群分布点进行除趋势对应分析,表明石杉碱甲含量高的磐安种群分布点具有特殊性,提示环境条件对蛇足石杉中HupA含量有较大的影响。     

五节芒对重金属污染土壤微生物生物量和呼吸的影响

选择3个五节芒在重金属污染地的定居点作为研究样地,其中两个为Pb/Zn矿尾矿砂堆积地（W：黄岩铅锌尾矿;Y：三门铅锌尾矿）,一个为冶炼厂附近污染农田（N）,分别测定其根围与根际土壤微生物基础呼吸、微生物量碳、微生物量氮、土壤理化特性和土壤重金属含量.结果表明：根际土壤微生物基础呼吸和微生物量氮均显著地高于根围土壤（P<0.05）,除了N样地外,微生物量碳在根围与根际之间差异不显著（P>0.05）.根际土壤有机碳、总氮（Y样地除外）和离子交换量（N样地除外）低于根围土壤.根际重金属（Pb、Zn、Cu、Cd）总量与DTPA（二乙三胺五乙酸）可提取量普遍低于根围土壤.冗余分析（RDA）表明,根围和根际土壤微生物与土壤理化特性呈不同程度的正相关,而与土壤重金属含量呈现不同程度的负相关.主分量及回归分析同样证明土壤微生物总体变化与土壤理化特性呈正相关（根围R²=0.653;根际R²=0.690）,而与重金属含量呈负相关（根围R²=0.610;根际R²=0.662）.     

EFFECTS OF INOCULATION WITH ARBUSCULAR MYCORRHIZAL FUNGI ON MAIZE GROWN IN MULTI-METAL CONTAMINATED SOILS

Pot culture experiments were established to determine the effects of colonization by arbuscular mycorrhizal fungi (AMF) (Glomus mosseae and G. sp) on maize (Zea mays L.) grown in Pb, Zn, and Cd complex contaminated soils. AMF and non-AMF inoculated maize were grown in sterilized substrates and subjected to different soil heavy metal (Pb, Zn, Cd) concentrations. The root and shoot biomasses of inoculated maize were significantly higher than those of non-inoculated maize. Pb, Zn, and Cd concentrations in roots were significantly higher than those in shoots in both the inoculated and non-inoculated maize, indicating the heavy metals mostly accumulated in the roots of maize. The translocation rates of Pb, Zn, and Cd from roots to shoots were not significantly difference between inoculated and non-inoculated maize. However, at high soil heavy metal concentrations, Pb, Zn, and Cd in the shoots and Pb in the roots of inoculated maize were significantly reduced by about 50% compared to the non-inoculated maize. These results indicated that AMF could promote maize growth and decrease the uptake of these heavy metals at higher soil concentrations, thus protecting their hosts from the toxicity of heavy metals in Pb, Zn, and Cd complex contaminated soils.     

Physical disturbance of an upland grassland influences the impact of elevated UV-B radiation on metabolic profiles of below-ground micro-organisms

This investigation determined the response of soil microbial communities to enhanced UV‐B radiation and disturbance in upland grassland. A factorial field experiment encompassing two levels of UV‐B supplementation (simulating ambient and a 30% increase in stratospheric ozone) and two levels of disturbance (disturbed and undisturbed) was established at Buxton Climate Change Impacts Laboratory, Derbyshire, UK, and maintained for 7 years prior to sampling. Enhanced UV‐B increased microbial utilization of carbohydrates, carboxylic acids, polymers and aromatic compounds present in Biolog® GN plates when inoculated with soils taken from disturbed plots, but did not affect carbon utilization of soil microbial communities associated with undisturbed plots (UV‐B×Disturbance interaction, P<0.05 for each substrate type). UV‐B treatment did not affect numbers of bacteria or fungi. Direct microscopic counts showed fewer bacteria in soil originating from disturbed plots than from undisturbed plots (Disturbance, P<0.001), although a greater number of culturable bacteria and fungi were isolated from disturbed than from undisturbed soils (Disturbance, P<0.001). No UV‐B‐ or disturbance‐related differences in protein, starch or urea hydrolysis were exhibited by bacterial isolates. UV‐B treatment did not affect total plant biomass within undisturbed plots or the biomass of individual groupings of grasses, forbs and mosses. Per cent root length colonized by arbuscular mycorrhizal fungi (AMF) was not affected by enhanced UV‐B radiation in the undisturbed plots. Neither AMF nor plant biomass was measured in disturbed plots. The key findings of this study show that UV‐B‐mediated alterations in carbon utilization occurred in soil microbial communities subjected to disturbance, but such changes were not observed in communities sampled from undisturbed grassland. Differences in the catabolic potential of microbial communities from disturbed grassland subjected to enhanced UV‐B are probably related to plant‐mediated changes in resource availability or quality.     

Terrestrial Arthropods as Indicators of Ecological Restoration Success in Coastal Sage Scrub (California, U.S.A.)

Abstract Ecological restoration enjoys widespread use as a technique to mitigate for environmental damage. Success of a restoration project often is evaluated on the basis of plant cover only. Recovery of a native arthropod fauna is also important to achieve conservation goals. I sampled arthropod communities by pitfall trapping in undisturbed, disturbed, and restored coastal sage scrub habitats in southern California. I evaluated arthropod community composition, diversity, and abundance using summary statistics, cluster analysis, and detrended correspondence analysis (DCA) and investigated influence of vegetation on arthropod communities with multiple regression analysis. Arthropod diversity at undisturbed and disturbed sites was greater than at sites that were 5 and 15 years following restoration ( p < 0.05). Number of arthropod species was not significantly different among undisturbed, disturbed, and restored sites, and two restoration sites had significantly more individuals than other sites. Vegetation at disturbed and undisturbed sites differed significantly; older restorations did not differ significantly from undisturbed sites in diversity, percent cover, or structural complexity. In multiple regression models, arthropod species richness and diversity was negatively related to vegetation height but positively related to structural complexity at intermediate heights. Exotic arthropod species were negatively associated with overall arthropod diversity, with abundance of the earwig Forficula auricularia best predicting diversity at comparison (not restored) sites (r² = 0.29), and abundance of the spider Dysdera crocata and the ant Linepithema humile predicting diversity at all sites combined (r² = 0.48). Native scavengers were less abundant at restored sites than all other sites and, with a notable exception, native predators were less abundant as well. DCA of all species separated restored sites from all other sites on the first axis, which was highly correlated with arthropod diversity and exotic arthropod species abundance. Lower taxonomic levels showed similar but weaker patterns, with example families not discriminating between site histories. Vegetation characteristics did not differ significantly between the newly restored site and disturbed sites, or between mature restoration sites and undisturbed sites. In contrast, arthropod communities at all restored sites were, as a group, significantly different from both disturbed and undisturbed sites. As found in other studies of other restoration sites, arthropod communities are less diverse and have altered guild structure. If restoration is to be successful as compensatory mitigation, restoration success standards must be expanded to include arthropods.     

Sources and Ecological Risk Assessment of Heavy Metal(loid)s in Agricultural Soils of Huzhou,China

To identify sources of heavy metal(loid) (HM) contamination in agricultural soils of Huzhou, surface soil samples were sampled from 89 different agricultural regions in 2012. Concentrations of heavy metal(loid)s, along with pH, total phosphorus (TP), total nitrogen (TN), and soil organic matter (SOM), were determined. Ecological risk was then assessed using a modified Hakanson ecological risk index, and the sources of contamination were determined using principal component analysis (PCA). Mean concentrations of heavy metal(loid)s were 10.26, 23.21, 83.75, 22.81, 0.25, 61.86, 33.03, and 0.15 mg kg^?1 for As, Cu, Zn, Ni, Cd, Cr, Pb, and Hg, respectively. Cu, Zn, Ni, Cr, Cd, Hg, and Pb were correlated positively with TP and there were obvious positive correlations among Cu, Zn, Ni, Cr, and Cd. Risk index (RI) values varied from 39 to 1246 with a mean value of 137. Enrichment of Pb, Zn, Cu, and especially Cd can be attributed to excessive use of nitrogen and phosphorus fertilizers containing heavy metals, as well to surface irrigation and natural soil formation. While the ecological risk of most agricultural soils in Huzhou is low, it is recommended that the use of phosphate and nitrogen fertilizers be restricted and production technology be improved to reduce the heavy metal(loid) concentrations. Results suggest that the Chinese environmental quality standard for soil should be revised to better address heavy metal(loid) contamination.     

Heavy metal contamination in vegetables grown around peri-urban and urban-industrial clusters in Ghaziabad,India

Heavy metal contamination of agricultural soils resulting from rapid industrialization and urbanization is of great concern because of potential health risk due to dietary intake of contaminated vegetables. The present study aims to evaluate the status of heavy metals contamination of agricultural soils and food crops around an urban-industrial region in India. Transfer factor values of Cu, Cr, Pb, Cd, Zn, and Ni from soil to vegetable was estimated. The mean heavy metal concentrations (mg/kg) in agricultural soils (Cu: 17.8, Cr: 27.3, Pb: 29.8, Cd: 0.43, Zn: 87, Mn: 306.6, Fe: 16984, and Ni: 53.8) were within allowable concentrations for Indian agricultural soil. The concentrations of Pb, Cd, Zn, and Ni in crops/vegetables exceeded the World Health Organization/Food and Agriculture Organization safe limits. Relative orders of transfer of metals from soil to edible parts of the crops/vegetables were Cd > Pb > Ni > Zn > Cu > Cr. The enrichment factors of heavy metals in soil indicated minor to moderately severe enrichment for Pb, Cd, and Ni; minor to moderate enrichment for Zn; no enrichment to minor enrichment for Mn; and no enrichment to moderate enrichment for Cu at different sites. Ecological risk index of soil showed considerable contamination in one of the wastewater irrigated sites.     

Estimation of Cd,Pb, and Zn Bioavailability in Smelter-Contaminated Soils by a Sequential Extraction Procedure

Chemical fractionation methods may be capable of providing an inexpensive estimate of contaminant bioavailability and risk in smelter-contaminated soil. In this study, the relationship between metal fractionation and methods used to estimate bioavailability of these metal contaminants in soil was evaluated. The Potentially BioAvailable Sequential Extraction (PBASE) was used for Cd, Pb, and Zn fractionation in 12 soils contaminated from Pb and Zn mining and smelting activities. The PBASE procedure is a four-step sequential extraction: extraction 1 (E1) is 0.5 M Ca(NO₃)₂, E2 is 1.0 M NaOAc, E3 is 0.1 M Na₂EDTA, and E4 is 4 M HNO₃. Metal bioavailability for two human exposure pathways, plant uptake (phytoavailability) and incidental ingestion (gastrointestinal, Gl, availability), was estimated using a lettuce (Lactuca sativa L.) bioassay and the in vitro-Gl Physiologically Based Extraction Test(PBET). Metal in the PBASE E1 fraction was correlated with lettuce Cd (P < 0.001) and Zn (P < 0.05) and was the best predictor of Cd and Zn phytoavailability. Only total metal content or the sum of all PBASE fractions, ΣE_1–4, were correlated (P < 0.001) with PBET gastric phase for Pb. The sum of the first two PBASE fractions, ΣE_1–2, was strongly correlated (P < 0.001) with Pb extracted by the PBET intestinal phase. The PBASE extraction method can provide information on Cd and Zn phytoavailability and Gl availability of Pb in smelter-contaminated soils.     

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.     

METAL UPTAKE AND ALLOCATION IN TREES GROWN ON CONTAMINATED LAND: IMPLICATIONS FOR BIOMASS PRODUCTION

Phytostabilization aims to reduce environmental and health risks arising from contaminated soil. To be economically attractive, plants used for phytostabilization should produce valuable biomass. This study investigated the biomass production and metal allocation to foliage and wood of willow (Salix viminalis L.), poplar (Populus monviso), birch (Betula pendula), and oak (Quercus robur) on five different soils contaminated with trace elements (TE), with varying high concentrations of Cu, Zn, Cd, and Pb as well as an uncontaminated control soil. In the treatment soils, the biomass was reduced in all species except oak. There was a significant negative correlation between biomass and foliar Cd and Zn concentrations, reaching up to 15 mg Cd kg^?1 and 2000 mg Zn kg ^?1 in willow leaves. Lead was the only TE with higher wood than foliage concentrations. The highest Pb accumulation occurred in birch with up to 135 mg kg ^?1 in wood and 78 mg kg ^?1 in foliage. Birch could be suitable for phytostabilization of soils with high Cd and Zn but low Pb concentrations, while poplars and willows could be used to stabilise soils with high Cu and Pb and low Zn and Cd concentrations.     

新疆焉耆盆地辣椒地土壤重金属污染及生态风险预警

从新疆加工辣椒主产地(焉耆盆地)采集105个辣椒地典型土壤样品,测定其中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn等8种重金属元素的含量。采用污染负荷指数(Pollution load index,PLI)、潜在生态风险指数(Potential ecological risk index,RI)和生态风险预警指数(Ecological risk warning index,I_(ER))对辣椒地土壤重金属污染及生态风险进行评价。结果表明:(1)焉耆盆地辣椒地土壤Cd、Cr、Ni、Pb和Zn含量的平均值分别超出新疆灌耕土背景值的1.65、1.40、1.32、3.21、6.42倍。辣椒地土壤Pb和Zn呈现重度污染,Cd、Cr和Ni轻度污染,As、Mn和Cu无污染。(2)土壤PLI平均值为1.40,呈现轻度污染。各重金属元素单项生态风险指数从大到小依次为:Cd、Ni、As、Cu、Pb、Cr、Zn。土壤RI平均值为18.40,属于轻微生态风险态势,IER平均值为-4.78,属于无警态势;博湖县辣椒地污染水平、潜在生态风险程度与生态风险预警等级最高,焉耆县污染水平、潜在生态风险程度与生态风险预警等级最低。(3)辣椒地土壤As、Cd、Pb与Zn主要受到人类活动的影响,Cr、Cu、Mn和Ni主要受到土壤地球化学作用的控制。Cd是焉耆盆地辣椒地生态风险等级最高的重金属元素,研究区农业生产过程中要防范Cd的污染风险。