[Evaluation of phosphate-containing amendments on remediation effect and influential factors in a lead/zinc mining tailings contaminated soil using TCLP and forms].

A pot experiment was conducted to evaluate the effects of phosphate-containing (P) amendments on the toxicity and bioavailability of Pb and Zn in a soil contaminated by mining tailings using toxicity characteristic leaching procedure (TCLP) and water soluble, exchangeable leaching procedures in order to find out the appropriate P application rates to reduce the soil TCLP extractable Pb to below the USA EPA's regulatory limit levels. The results showed that TCLP extractable Pb concentrations were significantly decreased by up to 93.3% for MPP treatments and up to 68.5% for SSP treatments after P application. The dose required to reduce leachable Pb below the EPA's regulatory limit level was found to be around the molar ratio of v(P/Pb) = 0.6 for MPP and 1.8 for SSP. It was also found both MPP and SSP could reduce the exchangeable Pb and Zn concentrations that all bio-available Zn forms including water soluble, exchangeable, and TCLP extractable forms in soil were significantly and negatively correlated to soil pH values, indicating that the content of Zn in the soil was mostly controlled by soil pH value even after P application. These results suggest that P as MPP and SSP could successfully decrease the toxicity and bioavailability of Pb and Zn in the contaminated soil.

[Assessment of health risk for mined soils based on critical thresholds for lead, zinc, cadmium and copper].

Contents of heavy metals (Pb, Zn, Cd, Cu) in soils in terms of point, line and area around a lead/zinc mine in Dongguan town, Zhejiang, China, were investigated to evaluate environmental quality based on index and health risk assessment model for safety of soils-human. The order for average contents of Pb, Zn, Cd, Cu in terms of point, line and area were Pb >> Zn >> Cu >> Cd. The contents of Pb, Zn, Cd, Cu in terms of point and line were much higher than that in terms of area, especially Pb and Zn contents. The distribution of soil heavy metals was asymmetric. The calculated critical threshold in soil for adult was higher than that for children. The average order of individual risk index for children and adult health was Pb >> Cd > Cu > Zn. Children were more easily affected by soil heavy metals, for that hazard indexes for children were 3 times of adult health. The environmental quality of Dongguan town was mainly safe correspondingly. The heavy metal environmental quality in terms of point and line near a lead/zinc mine had higher hazard risk and might bring potential hazard to local residents.

[Effect of chlorine and phosphorus on water soluble and exchangeable lead in a soil contaminated by lead and zinc mining tailings].

Effect of chlorine on in situ lead immobilization using phosphorus in a soil contaminated by lead and zinc mining tailings was evaluated. The results showed that water soluble and exchangeable Pb were reduced by 92.0%-95.1% in the soil after P application. It was also suggested that application dosage of phosphorus at the P/Pb molar ratio of 0.6, was enough to remediate Pb toxicity in the soil. Compared to without Cl treatment at the level of molar ratio of 0.6 P/Ph, water soluble and exchangeable Pb in the soil treated with Cl was reduced markedly. It was concluded that the effects chlorine addition on in situ lead (Pb) immobilization using phosphate were improved. Visual MINTEQ model was employed to figure out Pb and P species distribution and saturation indices for minerals in the soils treated by P and Cl. The results showed that Pb activity was controlled by lead phosphate in the soil, especially pyromorphite [Pb5(PO4)3Cl], which would be the reason for Pb bioactivity reduction in the soil after application of Cl and P. The effective Pb bioactivity reduction indicated that addition of Cl was necessary to to improve in situ lead immobilization using phosphorous in the lead-contaminated soil.

[Effects of phosphorus application on translocation of lead, zinc and cadmium in the soil-plant system].

A pot experiment was conducted to determine the influence of phosphorus (P) application on the translocation and accumulation of lead (Pb), zinc (Zn), and cadmium (Cd) in a soil solid-liquid-plant system using a plant Swamp Morningglory (Ipomoea aquatica Forak) as an indicator and Visual MINTEQ model. A contaminated soil containing 22,830 mg x kg(-1) Pb, 746 mg x kg(-1) Zn, and 10 mg x kg(-1) Cd was in the root was significantly decreased after P application, while the Zn concentration were increased, but no impact on Cd concentration after P application, compared to the control. Further more, concentrations of Pb, Zn, and Cd in plant tissue were sharply reduced after P application by 53%-92%, 35%-71%, and 59%-86%, respectively; Concentrations decreased exponentially with increasing amount of P; Relationship between Pb and Zn (r = 0.993, p < 0.01), between Pb and Cd (r = 0.986, p < 0.01) suggested that there was a positive relationship between the mechanisms controlling the phytoavailability of Pb, Zn, and Cd. It was suggested that Cd concentrations in the soil solution were reduced generally by P application as a result of the increased soil pH, and Zn concentrations were no change, but Pb concentrations were increased. Species distribution showed that PbHPO4, PbOH+ and PbH2PO4+ were the main complexation species of Pb in the soil equilibrium solution after P application. It was also suggested that Pb accumulation by root were negatively correlated to Pb in soil solution with coefficient of -0.872 (p < 0.05), and that water soluble Zn and Cd concentrations were reduced while the concentrations in root tissues were increased after P addition. These results indicate the difference between Zn, Cd and Pb and suggest that P as KH2PO4 successfully decreased the phytotoxicity of Pb, Zn, and Cd in the contaminated soil.

[Study on the determination of metsulfuron-methyl and its adsorption behavior on typical soils and minerals].

Adsorption behavior of metsulfuron-methyl on soils and minerals was investigated using batch experiment. The concentration of metsulfuron-methyl in supernatant was analyzed by capillary electrophoresis (CE) method. Metsulfuron-methyl, whose peak centered at 4.6 min in capillary electrophoresis chromatogram, was well separated from impurities in soil slurry. CE was shown to be fast with low operating cost in the routine determination of the herbicide, which was further confirmed by high performance liquid chromatograph (HPLC). Sorption isotherms were fitted to the Freundlich equation, where the parameter Kf was in the range of 0.82-199.69 for minerals and 1.97-10.48 for soils, respectively. Among the various factors influencing the sorption behavior of metsulfuron-methyl, soil pH appeared to be the most important one. The electrostatic interaction mechanism was applied in the explanation of the sorption behavior of metsulfuron-methyl.

[Quality evaluation of soil fluorine on Hangjiahu Plain based on GIS].

Contents of fluorine in the plough layer (0-20 cm) of paddy soils from Hangjiahu Plain were investigated to evaluate quality of fluorine using total fluorine index method. Kriging method was applied to study the spatial variability of soil total fluorine in relation to their influential factors and their distribution maps were obtained based on GIS. The results showed that the range of total fluorine (TF) contents in the soils from central and eastern parts of Hangjiahu Plain was higher than that from the western part. The concentrations of TF in soil had a close relationship with parent material, pH value, organic matter, cation exchange capacity content and soil texture. The main range of TF was 200-300 mg/kg, while TF contents accounting for 23.7% of the area were less than 200 mg/kg in the studied area. In which TF contents in soil in Yuhang County were the lowest, less than 100 mg/kg.

[Evaluation on environmental quality of Pb, Zn and Cu contents in vegetable plantation soils and vegetables in Hangzhou suburb].

Contents of heavy metals (Pb, Zn, Cu) in soils from 4 main vegetable plantations in Hangzhou suburb were investigated to evaluate environmental quality of heavy metals of soils and vegetables. Different evaluation methods and evaluation standards of heavy metals were used for comparison. Kriging method was applied to study the spatial variability of heavy metals in soil-vegetable system. The distribution maps of the spatial variability of heavy metals in soil-vegetable system in Jianggan District were obtained based on GIS method. The results show that the soils were polluted with Pb, Zn, and Cu using natural background values as evaluation standard. While using National Standard as evaluation standard, the soils were not polluted. Contents of heavy metals in Gongshu District were the highest of four investigated districts. The concentration distribution of heavy metals had different spatial variability. The content of Pb in vegetables was higher than those of Zn and Cu and exceeded the national vegetable sanitation standard. The order for their enrichment coefficients was as follows: Zn> Pb> Cu. The accumulation coefficient for green vegetable was higher than that of Chinese cabbage, indicating green vegetable could easily accumulate heavy metals from soils than Chinese cabbage.

Field demonstration of reduction of lead availability in soil and cabbage (Brassica Chinensis L.) contaminated by mining tailings using phosphorus fertilizers.

A field demonstration of reduction of lead availability in a soil and cabbage (Brassica Chinensis L.) contaminated by mining tailings, located in Shaoxing, China was carried out to evaluate the effects of applications of phosphorus fertilizers on Pb fractionation and Pb phyto-availability in the soil. It was found that the addition of all three P fertilizers including single super phosphate (SSP), phosphate rock (PR), and calcium magnesium phosphate (CMP) significantly decreased the percentage of water-soluble and exchangeable (WE) soil Pb and then reduced the uptake of Pb, Cd, and Zn by the cabbage compared to the control (CK). The results showed that the level of 300 g P/m(2) soil was the most cost-effective application rate of P fertilizers for reducing Pb availability at the first stage of remediation, and that at this P level, the effect of WE fraction of Pb in the soil decreased by three phosphorus fertilizers followed the order: CMP (79%)>SSP (41%)>PR (23%); Effectiveness on the reduction of Pb uptake by cabbage was in the order: CMP (53%)>SSP (41%)>PR (30%). Therefore our field trial demonstrated that it was effective and feasible to reduce Pb availability in soil and cabbage contaminated by mining tailings using P fertilizers in China and PR would be a most cost-effective amendment.

[Evaluation on environmental quality of heavy metals in soils and vegetables based on geostatistics and GIS].

Contents of heavy metals (Pb, Zn, Cd, Cu) in soils and vegetables from Dongguan town in Shangyu city, China were studied using geostatistical analysis and GIS technique to evaluate environmental quality. Based on the evaluation criteria, the distribution of the spatial variability of heavy metals in soil-vegetable system was mapped and analyzed. The results showed that the distribution of soil heavy metals in a large number of soil samples in Dongguan town was asymmetric. The contents of Zn and Cu were lower than those of Cd and Pb. The concentrations distribution of Pb, Zn, Cd and Cu in soils and vegetables were different in spatial variability. There was a close relationship between total and available contents of heavy metals in soil. The contents of Pb and Cd in green vegetables were higher than those of Zn and Cu and exceeded the national sanitation standards for vegetables.

[Assessment of toxicity of heavy metal contaminated soils by toxicity characteristic leaching procedure].

The contents of heavy metals (Cu, Zn, Pb and Cd) in soils from a lead-zinc mine in Shangyu, Zhejiang Province, China, were analyzed and their toxicity was assessed by toxicity characteristic leaching procedure (TCLP), which was developed by US EPA. The TCLP method is a currently recognized international method for evaluation of heavy metal pollution in soils. The available levels of Cu, Zn, Pb and Cd were 8.2-36 mg x kg(-1), 23-143 mg x kg(-1), 6.4-1367 mg x kg(-1) and 0.41-2.2 mg x kg(-1), respectively, while the international standard were 15 mg x kg(-1), 25 mg x kg(-1), 5 mg x kg(-1) and 0.5 mg x kg(-1), respectively. The results show that soils around the mine are polluted with heavy metals Cu, Zn, Pb and Cd, especially polluted by Zn and Pb, followed by Cd and Cu. Moreover, the heavy metals in the soils extracted by TCLP indicate that fluid 2 is more effective than fluid 1 in extracting the heavy metals from the polluted soils and there is a positive correlation between fluid 1 and fluid 2. The contents of available heavy metals by TCLP are correlated with contents of total heavy metals.

Risk assessment of heavy metal contaminated soil in the vicinity of a lead/zinc mine.

Heavy metal contamination of soils through anthropogenic activities is a widespread and serious problem confronting scientists and regulators throughout the world. In this study we investigated the distribution, chemical species and availability of lead, zinc, cadmium and copper in nine surface (0 to 20 cm) soils from near an abandoned lead/zinc mine tailings located in Shaoxing, Zhejiang, China. Total heavy metal contents ranged from 5271 to 16369 mg/kg for Pb, 387 to 1221 mg/kg for Zn, 3.0 to 9.3 mg/kg for Cd and 65 to 206 mg/kg for Cu. In general, all heavy metals exceeded China National Standards for Soil Environmental Quality of Heavy Metals by a factor of 3-65 times. Comparison of the heavy metal concentrations (Pb, Zn, Cd and Cu) with clay content revealed a strongly significant relationship while significant relationship (P < 0.001) was also obtained between Cd + Zn and Pb + Cu. Solid phase speciation of the soils using Tessier procedure showed that the heavy metals were distributed in the order: residual > organically complexed-Fe-Mn oxides occluded > carbonate bound > exchangeable > water soluble. In the organic matter fraction, the ratio of Pb (29.1%) to its total concentration in the soils was higher than those of Zn (4.70%), Cd (3.16%) and Cu (9.50%). The percentages of the water soluble and the exchangeable fractions of Pb (1.80%) and Cd (2.74%) were markedly greater than those of Zn (0.10%) and Cu (0.15%), suggesting that Pb and Cd are relatively more mobile and hence more toxic in the contaminated soils. Strongly significant relationships between H2O-Pb, H2O-Zn and H2O-Cu, strong positive correlations between H2O-Pb, H2O-Zn, H2O-Cu and organic matter in soil were found. The content of H2O-Pb, H2O-Zn, H2O-Cu was negatively correlated with pH values. The similar negative relationships between pH values and exchangeable heavy metals were also recorded. It is suggested that increasing soil pH or liming the soil could decrease bioavailability of heavy metals in the soil.

Impact of triazophos insecticide on paddy soil environment.

A laboratory incubation study was carried out to elucidate the dynamic response of insecticide (triazophos) on a paddy field soil health under controlled moisture (flooded soil) and temperature (25 degrees C). The insecticide was applied at five levels that were 0.0 (control), 0.5 field rate (FR), 1.0 FR, 5.0 FR, and 10.0 FR, where FR was 1500 ml/hm2, and the parameters were studied at 1, 4, 7, 14, and 21 days after treatments' addition. The electron transport system (ETS)/dehydrogenase activity exhibited a negative correlation with insecticide concentrations, and the activity affected adversely as the concentration increased. The higher doses of 5 and 10 field rates significantly reduced the ETS activity, while lower rates failed to produce any significant inhibiting effect against the control. The toxicity of insecticide decreased towards decreasing the ETS activity with the advancement of incubation period. The insecticide caused an improvement in the soil phenol content and it increased with increasing concentration of insecticide. The insecticide incorporation applied at various concentrations did not produce any significant change in soil protein content and it remained stable throughout the incubation period of 21-days. The response of biomass phospholipid content was nearly similar to ETS activity. The phospholipid content was decreased with the addition of insecticide and the toxicity was in the order: 10 FR (field rate) > 5 FR > 1.0 FR > 0.5 FR > control and it also decreased with incubation period.