| Heavy metal pollution is one of the most serious environmental problern, which has caused widespread concern. The spatial distribution, heavy metal species and environmental risks of these metals in soils, including aciding area, deserted paddy field, deserted area and sediments from a traditional e-waste aciding site(Guiyu, one of the largest e-waste dismantling centers in the world) were investigated. Based on above results, the fixation rate and leaching behaviors of heavy metals after incineration of these soils from guiyu was studied. All results are shown as follows:The total concentrations of 12 heavy metals in surface soils(SS, 0-20 cm), middle soils(MS, 30-50 cm) and deep soils(DS, 60-80 cm) from an acid leaching area, a deserted paddy field and a deserted area of Guiyu were measured. The results showed that the acid leaching area was heavily contaminated with heavy metals, especially in SS. The mean concentrations of Ni, Cu, Zn, Cd, Sn, Sb, and Pb in SS from the acid leaching area were 278.4, 684.1, 572.8, 1.36, 3472, 1706, and 222.8 mg/kg, respectively. Heavy metal pollution in the deserted paddy field mainly concentrated in SS and MS. The average values of Sb in SS and MS from the deserted paddy field were 16.3 and 20.2 mg/kg, respectively. Both of them were higher than the indicative level of Dutch standands(15 mg/kg). However, heavy metal contamination of the deserted area was principally found in the DS. Extremely high concentrations of heavy metals were also observed at some special research sites, further confirming that the level of heavy metal pollution was very serious. The geoaccumulation index(Igeo) values revealed that the acid leaching area was severely polluted with heavy metals in the order of Sb>Sn>Cu>Cd>Ni>Zn>Pb, while deserted paddy field was contaminated predominately by metals in the order of Sb >Sn>Cu. It was obvious that, the concentrations of some uncommon contaminants, such as Sb and Sn, was higher than principal contaminants, such as Ni, Cu, Zn and Pb, suggesting that particular attention should be directed to Sn and Sb contaminations in the future research of heavy metals in soils from e-waste processing areas. Correlation analysis suggested that Li and Be in soils from the acid leaching area and its surrounding environment might have originated from other industrial activities, whereas Ni, Cu, Zn, Cd, Pb, Sn and Sb contaminations were most likely caused by uncontrolled electronic waste(e-waste) processing.The spatial distribution, bioavailability, potential risks and emission sources of 12 heavy metals in sediments from an acid leaching site of e-waste in guiyu were investigated. The results showed that the sediments from the acid leaching site were significantly contaminated with Cu, Zn, Cd, Sn, Sb and Pb, especially in the middle sediments(30-50 cm), with average concentrations of 4820, 1260, 10.7, 2660, 5690 and 2570 mg/kg, respectively. Cu, Cd and Pb were mainly present in the non-residual fractions, suggesting that the sediments from the acid leaching site may exert considerable risks. Mn, Ni, Zn, Sn and Sb were predominantly associated with the residual fraction. Despite their low reactivity and bioavailability, uncommon pollutants, such as Sn and Sb, may exert environment risks due to their extremely elevated total concentrations. All of these results indicate that there is an urgent need to control the sources of heavy metal emission and to remediate contaminated sediments.Heavy metal pollutions in soils and sediments from the e-waste recycling site were serious. The solidification//stabilization method, thermal treatment, was used in this study. The effects of incineration temperature and incineration time on the fixation and leaching behavior of heavy metals in soils from an e-waste processing site were systematically investigated. Results showed that the fixation rates of Be, V, Cr, Mn, Co,Ni, Cu, Zn,Cd, Sn and Sb in these soils were 81.7%, 92.8%, 90.0%, 85.4%, 99.8%, 95.9%, 99.6%, 93.0%, 87.4%, 89.0% and 93.3%, respectively after incineration at 700 °C, 45 min. Both of them were higher than 80%. Meanwhile, the concentrations of Be, Cr, Co, Ni, Zn and Cd in TCLP leaching liquids decreased obviously. Both of them were lower than the corresponding background concentrations of groundwater in Dutch standard. It should be noted that the Cu concentration in TCLP leaching liquid clearly decreased from 461 μg/L(before incineration) to 66.4 μg/L(after incineration at 700 °C, 45 min). Therefore, the best incineration condition for soil remediation may be 700 °C, 45 min.In conclusion, the soils and sediments in the e-waste aciding area from guiyu were seriously polluted by various heavy metal contaminants. Thermal treatment is a suitable method for the remediation of most heavy metal pollutants. It should noted that becaues the p H values of soils and sediments from e-waste aciding area were low and these soils and sediments contains a large number of plastic debris, some secondary organic pollutants which were of great concern may be released to surrounding environment during primitive e-waste recycling activities. |
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