Investgation And Bioremediation Of Combined Pollution In Farmland Soil From E-Waste Recvcling Area

The shortage of metal resources causes electronic waste (e-waste) recycling industry growing rapidly. The rough dismantling technique and irrational industrial distribution has lead to heavy metal-organic combined pollution of soil in e-waste recycling area. Bioremediation is a promising solution for heavy metal-organic combined pollution of farmland soil, and is a hot topic in current research. A farmland near a typical e-waste dismantling contaminated site in southeast China was chosen as the research subject. Based on a pollution investigation, a simulating bioremediation of artificial heavy metals-organic combined contaminated soil in the lab was conducted by joint using of plant, microorganism and soil animal. Basing on the results from the lab-scale experiment, a plot experiment of bioremediation was conducted for actual heavy metals-organic combined contaminated soil in the farmland. The main results and conclusions are as follows:(1) The average concentrations of Cu, Pb, Zn, Ni and Cd in the surface soil were 132.6 mg/kg,185.5 mg/kg,306.6 mg/kg,42.4 mg/kg and 1.1 mg/kg, respectively. The concentration of total polychlorinated biphenyls (PCBs) was 1.03 mg/kg, and the concentration of total polycyclic aromatic hydrocarbons (PAHs) was 0.60 mg/kg. According to related domestic standards or international reference limiting values, assessed by "single pollution index" method, the soil was seriously contaminated by heavy metals and organic pollutants.(2) In the lab-scale experiment, the initial concentrations of Cu, Cd and Pb in soil were 480.7 mg/kg,13.5 mg/kg and 410.0 mg/kg, the initial concentrations of phenanthrene, pyrene, PCB28, PCB52, PCB118, PCB153 and PCB180 were 0.50 mg/kg,5.11 mg/kg,0.63 mg/kg,1.51 mg/kg,1.64 mg/kg,1.82 mg/kg and 2.03 mg/kg, respectively. After simulative bioremediation of 90 days, the group of ryegrass-degrading bacteria-earthworm joint treatment has the higest removal rate of pollutants from soil. The removal rates of Cu, Cd and Pb were 13.7%,6.2% and 3.6%, respectively. The reduction rates of phenanthrene and pyrene were 99.2%and 64.1%, and the attenuation rates of PCB28, PCB52, PCB118, PCB153 and PCB180 were 76.1%,40.2%,14.0%,11.5% and 10.0%, respectively. Heavy metals were mainly removed by plant, while pyrene and the low chlorinated PCBs were mainly removed by microbio-degradation. However, the high chlorinated PCBs could not be effectively bioremediated.(3) A bioremediation of the contaminated farmland was conducted using plant-microorganism-animal joint treatment. The original concentrations of Cu, Cd and Pb in surface soil were 105.3 mg/kg,3.3 mg/kg and 104.3 mg/kg, respectively. After 45 tretments, the removal rates of these three pollutants were 3.4%,1.2% and 1.5%, respectively. The removal rates of PCB52, PCB118, PCB153, PCB180 and pyrene were 34.3%,9.9%,7.1%,6.5% and 54.6%, respectively, when their initial concentrations were 0.21 mg/kg,0.13 mg/kg,0.04 mg/kg,0.03mg/kg and 0.52 mg/kg, respectively. The results show that the plant-microorganism-animal joint treatment has good effects and promising application potential of remediation for actual heavy metals-organic combined contaminated farmland soil.