Assessment and bioremediation of soils contaminated by uncontrolled recycling of electronic-waste at Guiyu, southeast China.

摘要

The major objectives of this study were to (1) characterize the persistent toxic substances (PTS, including PAHs, PCBs, PBDEs and PCDD/Fs) and their concentration and distribution in soils at Guiyu area of SE China, affected by uncontrolled E-waste recycling, and (2) investigate the interactions of PAH-degrading bacteria, arbuscular mycorrhizal fungi (AMF) and higher plant on enhanced bioremediation of PAH contaminated soil.;Guiyu soils were grossly contaminated by PAHs, PCBs and deca-BDE. The ranges of TEQ concentration for PCBs and PCDD/Fs in Guiyu soils were 0.28-314, and 0.386-15429 pg WHO-TEQ g-1, respectively. In general, the concentrations of all PTS increased sharply in the same order of reservoir areas (RS) rice fields (RF) areas near burning sites (NOBS) E-waste open burning sites (OBS). OBS soils had extremely high levels of total PCBs (73.8-1443 mug kg-1), PBDEs (2906-44373) and PCDD/Fs (30.0-968), which were the highest when compared with data available. NOBS were also heavily contaminated by all PTS, with the concentrations 6-50 times of those in RS. Concentrations of PAHs, PCBs and deca-BDE in RF exceeded the background values reported elsewhere. RS area was slightly affected, but contained considerable concentrations of naphthalene (87.6 mug kg-1), BDE-209 (2.76) and OCDD (0.39). Similar PTS profiles (except profiles of PCB congeners and PCDD/F homologues) were found among the four sites, and OBS had a similar PCDD/F homologue profile with that of typical combustion source, which indicated that the emission gases and fly ash generated from open burning of E-waste in OBS were one of the main sources of PTS in Guiyu. This is the first detailed scientific investigation on PTS contamination in soil caused by open burning of E-waste.;In the multi-component bioremediation system including PAH-degrading bacteria (Acinetobacter sp.), AMF (Glomus mosseae ) and ryegrass (Lolium multiflorum), AMF significantly (p0.05) improved the growth of ryegrass, and enhanced the resistance of ryegrass to PAHs contamination through decreasing free radical damage to cell membranes. Ryegrass cultivation improved growth of PAH-degrading bacteria and increased peroxidase activities in soil, which consequently enhanced the dissipation of PHE and PYR. Interactions of ryegrass with AMF or PAH-degrading bacteria significantly (p0.05) accelerated the dissipation of PHE and PYR from soil. Mild solvent extractable PHE and PYR were significantly (p0.01) correlated with PHE and PYR in ryegrass root, which confirmed that mild solvent extractable PAH in soil can be used to estimate PAH bioavailability to plant.;Using a rhizobox experiment, a decreasing dissipation gradient of PHE and PYR was revealed along radial direction of maize (Zea mays L.) root, with the highest dissipation rates in rhizosphere zone followed by near rhizosphere zone and bulk soil zone in outer compartments. AMF significantly (p0.05) enhanced the accumulation of PHE and PYR by plant roots, partially due to the hyphal transportation from outer compartment soil. The present results indicated that there is a potential for the development of a multi-component phytoremediation system for PAH contaminated soil, involving PAH-degrading bacteria, AMF and plant.