Total concentrations and fractionation of heavy metals in road-deposited sediments collected from different land use zones in a large city (Nanjing), China

Abstract

In order to investigate heavy metal contamination in an urban environment during urbanization and economic development, 35 road-deposited sediment samples were collected from seven different land-use zones (commercial, residential, traffic, scenic park, educational, industrial and peri-urban) in Nanjing, a large city in P.R. China. The ranges of total metal concentrations found were: 28.7–272 mg kg^?1 for Cu; 24.8–268 mg kg^?1 for Ni; 37.3–204 mg kg^?1 for Pb; 140–798 mg kg^?1 for Zn; 0.44–2.19mg kg^?1 for Cd; and 60.6–250 mg kg^?1 for Cr. Metal fractionation was carried out using a modified three-step European Bureau of References (BCR) sequential extraction procedure. Cadmium and Zn were found predominantly associated with the acid extractable fractions; Ni and Cr were dominant in the residual fraction; Pb was predominantly associated with the residual and reducible fractions; Cu was dominant in the oxidizable and residual metal fractions. Based on the sum of the acid-extractable, reducible, and oxidizable fractions, Cd, Zn and Pb are potentially the most toxic metals in the road-deposited sediment in Nanjing. No significant differences, except for Zn, were found in the metal fractionation pattern for Cu, Ni, Pb, Cd, and Cr in different land use zones.     

Cadmium and zinc in plants and soil solutions from contaminated soils

In an experiment using ten heavy metal-contaminated soils from six European countries, soil solution was sampled by water displacement before and after the growth of radish. Concentrations of Cd, Zn and other elements in solution (K, Ca, Mg, Mn) generally decreased during plant growth, probably because of uptake by plants and the subsequent redistribution of ions onto soil exchange sites at lower ionic strength. Speciation analysis by a resin exchange method showed that most Cd and Zn in non-rhizosphere solutions was present as Cd2+ and Zn2+, respectively. The proportion of free ions was slightly lower in rhizosphere solutions, mainly due to an increase in dissolved organic carbon during plant growth. Solution pH increased during plant growth, although the bulk soil pH generally remained constant. Cd concentrations in leaves and tubers were more closely correlated with their total or free ionic concentrations in rhizosphere solutions (adjusted R2 0.90) than with their concentrations in soils (adj. R2 0.79). Cd concentrations in non-rhizosphere solutions were only poorly correlated with Cd concentrations in leaves and tubers. In contrast to Cd, there were no soil parameters that individually predicted Zn concentrations in leaves and tubers closely. However, multiple correlation analysis (including Zn concentrations in rhizosphere solutions and in bulk soils) closely predicted Zn concentrations in leaves and tubers (adj. R2 = 0.85 and 0.70, respectively). This suggests that the great variability among soils in the solubility of Zn affected the rate of release of Zn into solution, and thus Zn uptake. There was no such effect for Cd, for which solubility varied much less. Furthermore, the plants may have partly controlled Zn uptake, as they took up relatively less at high solution concentrations of Zn.Free ionic concentrations in soil solution did not predict concentrations of Cd or Zn in plants better than their total concentrations in solution. This suggests that with these soils, analysis of Cd and Zn speciation is of little practical importance when their bioavailability is assessed.     

Effects of biochar amendments on speciation and bioavailability of heavy metals in coal-mine-contaminated soil

An incubation experiment was executed on applying biochar as a soil remediation amendment to discuss an effect of the various addition rates on the speciation and bioavailability of heavy metals in mining-contaminated soil. The result showed that the content of Cd in soil was 9.51 times higher than the Huainan soil background values. The contents of Cu, Zn and As were 2.97, 1.60 and 1.42 times the background values, respectively, and the total contents of all heavy metals were higher than the standard values of soil environment quality GB15618-1995 set by the China Ministry of Environmental Protection. Speciation analysis indicated that Cu and Cd were mainly associated with the reducible fraction, while Zn and As were dominated by the residual fraction. After biochar was added to contaminated soil, the residual fractions of heavy metals increased, while the acid-soluble fractions reduced. According to the results of CaCl₂ extraction experiment, CaCl₂-extractable concentrations of Cu, Zn, As, and Cd were observed with a biochar dosage rate of 10%, which were 57.26%, 51.37%, 6.94% and 42.04% lower than those of control soil samples, respectively, but there were no obvious changes of CaCl₂-extractable As.     

Quantitative speciation of heavy metals in soil and crops of agricultural fields of Islamabad,Pakistan

Abstract

Two root crops: carrot (Daucus carota) and spring onion (Allium fistulosum) and soil samples were selected from the agricultural fields located near Islamabad, Pakistan to determine their elemental content. Field soil speciation of the two crops was also carried out to analyse the correlation of the elements in field crop and soil. Concentrations of selected elements were evaluated in the leaf, stem, root and flowering part of the crops using flame atomic absorption spectrophotometry. The results showed that elements are mostly concentrated in soil rather than crop parts following the sequence Zn>Cu>Pb>Ni>Cr>Cd. Furthermore, soil speciation showed that Ni and Cr are more prevalent in the Fe–Mn oxide fraction, Zn and Cd as the carbonate bound fraction and Cu is found in the organic bound form. However, concentrations of Pb are similar across the carbonate, Fe–Mn oxide and organic bound fractions. The highest average concentration of Zn is found as the carbonate bound fraction (2.09 ± 0.005 mg kg^?1) and Cu as the organic bound (1.51 ± 0.029 mg kg^?1) in soil samples taken from the agricultural field of Daucus carota.     

Bioavailability of heavy metals in sediments of two coastal lagoons in Rio de Janeiro,Brazil

The distribution and bioavailability of trace metals in two contrasting tropical coastal lagoons were studied. The concentration of trace metals in aquatic macrophytes was compared with those found in sediments under weakly and strongly bound forms. The results showed that total metal concentrations in sediments did not explain the concentration found in plants. The highest concentrations in macrophytes were observed in the lagoon which had a higher fraction of metals weakly bound to sediments, but presented the lower total metal content. Low redox potential was the major variable keeping metals in non-bioavailable forms, possibly as refractory sulfides and metal-organic complexes. Among the macrophytes, rooted species showed lower concentrations of metals as compared to algae.     

Quick sequential procedure for speciation analysis of heavy metals in soils by supersonic extraction

Abstract

In order to improve the extraction efficiency and reduce the operation time, supersonic energy by means of supersonic bath was used to the modified Tessier sequential extraction for speciation analysis of heavy metals in soils. Extractable contents of Cu, Fe, Mn, Ni, Pb and Zn were measured by flame atomic absorption spectroscopy. The merit of the supersonic extraction (SE) applied to the modified Tessier, method is not only that the operation time for the first 4 fractions was reduced from ca 18 h to 8 h, comparing with conventional extraction (CE), but also the extraction efficiency was higher. There were no significant differences between the data obtained by the proposed method using supersonic extraction and the reference values of the standard reference materials of EES-2 and EES-3. The results for both of SE and CE in the soil samples were consistent. The extractable Cu, Ni and Zn in the sample No. 1 were mainly associated with the third fraction (Fe-Mn oxides fraction), and fourth fraction (organic matter fraction) in the sample No. 2. The extractable Fe and Mn were all mainly associated with the third fraction, and Pb the fourth fraction in both of the samples. The effects of varying concentrations of hydroxylamine hydrochloride on the extraction of metals were also studied.     

Distribution of extractable heavy metals in different soil fractions

Abstract

Due to the difficulties of precisely characterizing environmentally contaminated soil, the effects of heavy metals on plants are studied using uncontaminated soil spiked with known quantities of heavy metals. One problem in using spiked soils is how accurately the distribution of metals mimics stabilized natural soils. We studied the distribution of cadmium, chromium, copper, lead, nickel, and zinc in soil fractions after application in soluble form. The soil samples included a control (an uncontaminated Typic Argiudoll) and two samples spiked with either a moderate or high heavy metal concentration). After application of the salts the soils were subjected to wet/dry cycles over the course of three months. The soils were fractionated using a sequential chemical extraction procedure employing: (1) CaCl₂,(2) NaOH, (3) Na₂EDTA and (4) HNO₃, HCl, and HF. Soil physical separation was carried out by ultrasonic dispersion. The heavy metal levels were determined using ICP-AES. Each heavy metal displayed a unique behavior when added to soil in the form of soluble salts. Cadmium and zinc remained in the soluble fraction, indicating that no equilibrium was attained, while nickel primarily appeared in the insoluble fraction. Chromium, copper and lead were distributed among various soil chemical fractions. The highest levels of all metals appeared in the clay fraction except lead which was mainly present in the silt fraction.     

Bioavailability and speciation of arsenic in urban street dusts from Baoding city,China

Twenty-one street dust samples were collected from the urban sites in Baoding, China, to investigate the species and bioavailabilty of arsenic in them. The ecological risk and bioavailability of arsenic were evaluated using three models including Bioavailability Factor (BF), Contamination Factors (C_f)and Geoaccumulation Index model (I_geo). The species of arsenic in the dust samples were analyzed using an optimized BCR sequential extraction method. The total concentrations of As in the street dust samples ranged from 13.16 mg kg^?1 to 67.26 mg kg^?1. Geoaccumulation index (I_geo) of As ranged from 0.28 to 1.99. The speciation analysis indicated that As in the street dust samples were mainly in the residual fraction (F4), and the proportion ranged from 84.35% to 87.07%. Moreover, the ranges of the BF and C_f were 0.650–0.129 and 0.119–0.186, respectively. The results indicated that arsenic contained in the street dust samples was with low bioavailability.     

Chemical mobility and bioavailabity of sediment-bound heavy metals influenced by salinity

The transfer of metals from contaminated sediments to algal cell walls (Scenedesmus quadricauda) and organisms from various trophic levels (euryhaline osmoconform hydroid Cordylophora caspia and algae Brachiomonas submarina) was studied with a multichamber device. The system consists of a central chamber which contained the mud suspension and six external chambers containing the different biological indicators. The solids in the central and external chambers are separated by 0.45 m-diameter membranes which allow diffusion of the mobilized, dissolved metal compounds. Experiments were performed with dredged sediments at various salinities (0.5, 1.0, 1.5, and 2.0 percent, respectively) and the kinetic of re-adsorption was obtained by taking samples after different time intervals. High enrichment of Cd was found in the living alga Brachiomonas submarina, but on the other side only a weak influence of salinity on re-adsorption could be observed. Model experiments with ionic Cd showed a clear dependency on Cd-sorption on the algae, Cd-concentration in solution, and salinity. These results indicate that the transfer of metals mainly depends on the specific surface properties of the substrates and on the specific chemical form of the dissolved mobilized metal.     

Time evolution of Pb(II) speciation in Pampa soil fractions

Abstract

Soil pollution by heavy metals, particularly lead, is an important environmental concern; the bioavailability of such pollutants is strongly dependent on their chemical form. Here, the speciation of Pb(II) in soil fractions as a function of time shortly after its incorporation is studied, using a selective sequential extraction method. The sample came from an Argentinean Pampas region and was extensively characterised, including Rietveld analysis of the silt+clay fraction XRD pattern to find the major mineral components. Experiments were run twice, once in the winter and once in the summer. The results show different speciation time profiles in both cases, showing faster changes in winter due to the higher water content. The summer experiment corresponds to an earlier stage in the speciation profile evolution compared with winter. The soluble/exchangeable fraction decreases with time in summer but shows a lower and constant value in the winter. A high proportion is found to be adsorbed onto the stable (aluminosilicates+quartz) mineral fraction. The results strongly suggest that, even at a short time following soil pollution with Pb, a high proportion is adsorbed onto the mineral fraction, with only a low fraction being bioavailable. The most stable (mineral incorporated) form is observed to increase with time. Soil water content appears to be more important than temperature in determining the differences between the two.     

Heavy metals uptake by vegetables growing in sewage irrigated soil: relationship with heavy metal fractionation in soil

Abstract

Concentrations of the heavy metals Cd, Ni, Cr, Zn, Mn, Co and Cu in soils and vegetable samples (i.e. green chili and gourd) taken from six vegetable fields in the vicinity of Lahore, Pakistan were measured. These soils have been irrigated for a long time with untreated sewage effluents. A control site was selected that has history of fresh canal water irrigation. The sequential extraction procedure developed by Tessier was adopted to demarcate five metal fractions: exchangeable, acid soluble, reducible, oxidizable and residual. The extractants and digests were analysed by atomic absorption spectrometry. The fractionation procedure showed that all the metals were dominant (>50%) in the residual phase in control as well as in waste waster irrigated soils. The concentrations of all the metals in edible parts of the vegetables collected from wastewater irrigated soils, were above critical levels. The total metal concentrations in wastewater irrigated soils followed the order Mn> Co> Zn> Cr> Ni> Cu> Cd, while in control soils the ord er was Mn> Zn> Ni> Co> Cr> Cu> Cd. In order to understand the uptake of metals from soil to vegetables, correlation analyses were performed between metal concentrations in different fractions of soil and their concentrations in vegetables. Correlation analysis was performed at 95% and 99% confidence level. The meaningful significant negative correlation was observed between Cd_F5–Cd_chili,Cr_Total–Cr_gourd,Mn_F5–Mn_Chili,Gourd, Co_F5, _Total–Co_chili, Cu_Total–Cu_Chili which indicate the non availability of total content and residual fraction to studied vegetables. The positive correlation was observed between Cd_Fl-Cd_ChiU, Cd_Fl–Cd_gourd, Ni_{Fi, F3}–Ni_Gourd, Cr_{Fi, F3}, _F4–Cr_ChiU, Cr_F2–Cr_Gourd, Zn_{Fi, F2}–Zn_Gourd, Mn_F3–Mn_Chili, Mn_Fi–Mn_Gourd, Co_F2–Co_Chili, Cu_Fi–Cu_Chili. The positive correlation, especially for the first (exchangeable) second (acid soluble) and for the third (reducible) extraction steps, was obtained which indicate the bioavailability of these metal fractions to plant.     

Sludge-Derived Cu and Zn in a Humic-Gley Soil: Effect of Dissolved Metal-Organic Matter Complexes on Sorption and Partitioning

A sequential extraction scheme was combined with sorption isotherm analysis in order to investigate sorption of sewage sludge-derived Cu and Zn to the A-horizon of a humic-gley soil as a whole, and to the operationally defined exchangeable (1?M MgCl₂), carbonate (1?M NaOAc), Fe/Mn oxide (0.04?M NH₂OH.HCl), and organic (0.02?M HNO₃+30% H₂O₂) soil fractions. Sorption parameters were compared for a sample of sludge leachate (with 97.4% of Cu and 63.2% of Zn present as dissolved metal-organic matter complexes, as calculated by geochemical modeling involving MINTEQA2 and verified using an ion exchange resin method) with that of a reference solution exhibiting the same chemical characteristics as the leachate, except for the presence of dissolved organic material. Dissolved metal-organic matter complexes were found to significantly (P<0.05) depress sorption to the bulk soil and each fraction. The greatest depression of Cu and Zn sorption was observed for the exchangeable, carbonate, and Fe/Mn oxide fractions, while the organic fraction of the soil was the least affected. This reflects a greater affinity for the exchangeable, carbonate, and Fe/Mn oxide fractions by the free divalent metal (Cu²⁺, Zn²⁺), with sorption by these fractions attributed to cation exchange, chemisorption, and co-precipitation processes. The sorption characteristics of the organic fraction indicated that Cu and Zn sorption by soil organic matter mostly involved dissolved metal-organic matter complexes. This may be attributed to hydrophobic interactions between nonpolar regions of the dissolved metal-organic matter complexes and solid-phase soil organic matter.     

Bioavailability of arsenic in soil and mine wastes of the Tamar valley,SW England

ABSTRACT

The southern part of the Tamar valley area in SW England is highly mineralised and mines in the region were the world's principal producers of tin, copper and arsenic during the mid nineteenth century. The Devon Great Consols Mine, covering 67.6 ha (167 acres) is situated in this area. Residues from the mining activity resulted in unvegetated spoil tips and local soils highly contaminated with As (range 120–52600 μg/g As). Sequential chemical extraction procedures were conducted on eight surface samples (0–15 cm) taken from a 2.0 km long transect from within the mine site to agricultural grassland. The proportion of water extractable As in agricultural top soils was lower (0.05–0.3%) than the values obtained for mine wastes (0.02–1.2%). Arsenic was found to be concentrated in the Fe-organic and residual fractions, which accounted for up 93 % of the total As in mine spoil and nearby soils.     

Partitioning of Zn,Cd, Pb,and Cu in organic-rich soil profiles in the vicinity of a zinc smelter

Abstract

A five-step sequential extraction procedure was applied to organic-rich soil samples from five soil profiles situated 1–8 km from a zinc smelter. The partitioning of Zn, Cd, Pb, and Cu into five operationally defined fractions (exchangeable, “carbonate’’-bound, reducible, oxidizable, and residual) was studied at different soil depths down to 35cm. In the surface soil (0–1 cm) a major part of Pb and Cu was extracted in the oxidizable fraction, whereas for Zn and Cd slightly more was extracted in the ‘‘carbonate”-fraction than in the other four fractions. Extracted metal proportions in the oxidizable fraction were respectively of the order of 30%, 20%, 50%, and 80% for Zn, Cd, Pb, and Cu in the surface soil for all sites, but these proportions decreased with soil depth. In the surface soil less than 20% of all the elements were extracted in the residual fraction, but the proportions associated with this fraction generally increased with soil depth. In the C-horizon, differences in extracted proportions of Pb and Cu in the residual fraction were probably due to geochemical factors, whereas for Zn the low extracted proportion at a highly contaminated site (20%) may be due to Zn migration to the C-horizon at this site. For Cd the extracted proportions in the C-horizon were lower than for the other elements, generally below 20%, presumably because Cd is weaker in terms of its adsorption to the soil than the other elements studied. Total concentrations of the metals decreased strongly with increasing distance from the smelter, but less systematic differences were observed for their distributions among fractions. Potentially bioavailable metal proportions (exchangeable + “carbonate”-bound fraction) in the surface soil were about 50%, 60%, 20%, and 10% for Zn, Cd, Pb, and Cu, respectively. In C-horizon soil the mobility sequence Cd>Zn>Pb = Cu was generally observed. The present results indicate that the concentrations and chemical fractionation of Zn, Pb, and Cd in these soils represent a considerable risk to natural terrestrial food chains.     

Use of crops for in situ phytoremediation of polluted soils following a toxic flood from a mine spill

Following a toxic flood from a mine spill that affected over 45 km² in Southern Spain, experiments were conducted in 1999 to test the feasibility of using crops for phytoremediation of the area, after the mechanical removal of the mud. Two cereals, barley and triticale, and two Brassicaspp., rapeseed and ethiopian mustard, were planted in three contaminated plots, 50 × 100 m each, and in a control plot outside the affected area. Soil and plant contents of As, Cd, Cu, Pb, Tl and Zn were measured and bioaccumulation coefficients (BC) were calculated at maturity. The four crops tested accumulated Cd and Zn in the above-ground biomass only in the plot on acid soil. Both species of Brassica accumulated Tl (average BC of 3.6 and 1.4 for rapeseed and mustard, respectively, in contaminated plots). None of the four crop plants accumulated As, Cu and Pb under the experimental conditions. Maximum plant uptake values from soil were 5.4 mg m^–2 of As, 0.54 mg m^–2 of Cd, 9.7 mg m^–2 of Cu, 7.0 mg m^–2 of Pb, 3.4 mg m^–2 of Tl, and 260 mg m^–2 of Zn. Total crop uptake gave estimates for successful phytoremediation of at least five decades, casting doubts on the feasibility of using these crops for decontamination of the area. Nevertheless, cereal grains had mineral contents below toxicity levels for livestock, therefore it might be possible to use these crops for livestock feed while reducing deep percolation and gradually removing metals from polluted soils.     

Distribution,speciation, and ecological risk assessment of heavy metals in surface sediments of Jiaozhou Bay,China

This paper analyzed the distribution and speciation of seven heavy metals in sediments in Jiaozhou Bay. The ecological risk was assessed using three index approaches (i.e., risk assessment code (RAC), contamination factor (CF), and potential ecological risk index (PERI)) and by a comparison with sediment quality guidelines (Chinese Marine Sediment Quality Standards (CMSQS), and threshold effect level (TEL) and probable effect level (PEL) from the USEPA). Pb, Cr, As, Cu, Zn, and Hg contents at most sites were above the corresponding TEL and Class I criteria (CMSQS) value. Particularly, high contents of Cu, detected at sites S₇ (124.5 mg kg^?1) and S₈ (118.3 mg kg^?1), exceeded the respective PEL value, indicating that harmful biological effects might occur. Speciation analysis, individual CF, and RAC calculations suggested that Cd had the highest bioavailable fraction and thus posed a very high risk to aquatic ecosystem; Cu and Zn showed a medium–high risk. Both global CF and PERI analysis indicated a high pollution risk at sites S₇, S₁, S₃, and S₂, but the assessments of specific sites were different. The incomplete consistency suggested that it is necessary to consider both total contents and chemical speciation for providing a more realistic appraisal for the risk of heavy metals in sediments.     

Evaluation of Heavy Metals Pollution Loadings in the Sediments of the Ave River Basin (Portugal)

Sediment samples from the Ave river basin were collected with the aim of determining metal total pollution contents. Cr, Cu, Fe, Mn, Pb, Zn and VM at 550 °C were determined. Some physico-chemical parameters were also quantified in water samples collected in the water column just above the sediments.

Metal contamination factors (CF) indicated that sediments were not contaminated with Cu and Pb, slightly with Zn and moderately with Cr.

For sediments with high metal pollution loadings, the original BCR (Community Bureau of Reference) metal speciation protocol was also applied. Speciation studies showed that chromium was mainly associated with the oxidisable plus residual fractions (>85%). These results suggest that changes in the physico-chemical properties of the river water (e.g. pH, Eh) should not be accompanied by a significative release of chromium from sediments.

The relationships between chromium speciation fractions, physic-chemical parameters of the sediments and water samples were studied by Principal Component Analysis, and allowed to reduce the dimensionality of the data matrix from 14 to 3 significant components accounting for 89% of the variance. It was found that hydrous Fe/Mn oxides and organic matter are the “carriers” of chromium associated to fractions exchangeable and oxidable.     

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.     

Characterization of Heavy Metal Fractions in Agricultural Soils by Sequential Extraction Procedure: The Relationship Between Soil Properties and Heavy Metal Fractions

The present research was conducted to determine heavy metals in agricultural soils from Çanakkale, Turkey, using a sequential extraction procedure (acid soluble, reducible, oxidizable, and residual) as proposed by the Community Bureau of Reference (BCR) of the European Commission. Soil samples were taken from 12 different cultivated sites and analyzed for Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn concentrations. The results revealed an order of Mn > Cd > Pb > Co > Ni > Cu > Zn > Cr for the heavy metals based on the sum of the first three fractions (acid soluble + reducible + oxidizable). The relationships between soil properties and each metal fraction were identified through Pearsons's correlation analysis. Hierarchical cluster analysis was performed to determine the behaviors and similarities of metals in each fraction. While Mn, Pb, and Zn exhibited subjective behaviors in the acid-soluble fraction, Cd, Co, Cu, Cr, and Ni exhibited similar behaviors with each other.     

Activation and ecological risk assessment of heavy metals in dumping sites of Dabaoshan mine,Guangdong province,China

In Dabaoshan mine, dumping sites were the largest pollution source to the local environment. This study analyzed the activation and ecological risk of heavy metals in waste materials from five dumping sites. Results indicated that the acidification of waste materials was severe at all dumping sites, and pH decreased below 3.0 at four of the five sites. There was a drastic variation in Cu, Zn, Pb, and Cd concentrations in different sites. Site A with 12915.3 mg kg^?1 Pb and 7.2 mg kg^?1 Cd and site C with 1936.2 mg kg^?1 Cu and 5069.0 mg kg^?1 Zn were severely polluted. Higher concentrations of water-soluble Cu were probably the critical constraint for local pioneer plants. A significant positive correlation was found between the concentrations of water-soluble and HOAc-extractable elements, and the regression analysis showed that, compared with Cu, Zn and Cd, Pb was more difficult to be transformed from HOAc extractable to water soluble. Concentration of water soluble metals should be an important index, same as concentration of HOAc extractable metals, in assessing ecological risks, availability, and toxicity of heavy metals. The modified ecological risk index indicated that all dumping sites had very high potential ecological risks. It is necessary to decrease the availability of heavy metals to reduce the impact of waste materials on environment.