Congkai Zhang

Heavy metal and persistent organic compound contamination in soil from Wenling: an emerging e-waste recycling city in Taizhou area, China.

The present study was conducted to investigate the levels and sources of heavy metals (Cu, Cr, Cd, Pb, Zn, Hg and As) and persistent organic compounds including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in soils taken from Wenling, an emerging e-waste recycling city in Taizhou, China. The results suggested that most heavy metals exceeded the respective Grade II value of soil quality standards from State Environmental Protection Administration of China and also exceeded the Dutch optimum values. Total PAHs in soil ranged from 371.8 to 1231.2 microg/kg, and relatively higher PAHs concentrations were found in soils taken from simple household workshops. PCBs were detectable in all samples with total concentrations ranging from 52.0 to 5789.5 microg/kg, which were 2.1-232.5 times higher than that from the reference site (24.9 microg/kg). Results of this study suggested soil in the Wenling e-waste recycling area were heavily contaminated by heavy metals, PAHs and PCBs. Furthermore, compared with large-scale plants, simple household workshops contributed more heavy metals, PAHs and PCBs pollution to the soil environment, indicating that soil contamination from e-waste recycling in simple household workshops should be given more attention.

Degradation of phenanthrene and pyrene in spiked soils by single and combined plants cultivation.

The present study was conducted to investigate the capability of four plant species (tall fescue, ryegrass, alfalfa, and rape seed) grown alone and in combination to the degradation of phenanthrene and pyrene (polycyclic aromatic hydrocarbons, PAHs) in spiked soil. After 65 days of plant growth, plant biomass, dehydrogenase activity, water-soluble phenolic (WSP) compounds, plant uptake and accumulation and residual concentrations of phenanthrene and pyrene were determined. Our results showed that presence of vegetation significantly enhanced the dissipation of phenanthrene and pyrene from contaminated soils. Higher degradation rates of PAHs were observed in the combined plant cultivation (98.3-99.2% phenanthrene and 88.1-95.7% pyrene) compared to the single plant cultivation (97.0-98.0% phenanthrene and 79.8-86.0% pyrene). Contribution of direct plant uptake and accumulation of phenanthrene and pyrene was very low compared to the plant enhanced dissipation. By contrast, plant-promoted biodegradation was the predominant contribution to the remediation enhancement. The correlation analysis indicates a negative relation between biological activities (dehydrogenase activity and WSP compounds) and residual concentrations of phenanthrene and pyrene in planted soils. Our results suggest that phytoremediation could be a feasible choice for PAHs contaminated soil. Moreover, the combined plant cultivation has potential to enhance the process.

Enhancement of phenanthrene and pyrene degradation in rhizosphere of tall fescue (Festuca arundinacea)

A greenhouse experiment was conducted with varying concentrations of phenanthrene (11-344 mg kg(-1)) and pyrene (15-335 mg kg(-1)) spiked in the soil to evaluate the phytoremediation of PAHs contaminated soil using tall fescue (Festuca arundinacea). After 65-day of tall fescue growth, plant biomass, microbial viable counts, dehydrogenase activity, water-soluble phenolic compounds, phenanthrene and pyrene residual concentrations and removal percentages were determined. The results showed that target PAHs (phenanthrene and pyrene) did not affect plant biomass at lower concentrations but a reduced biomass (only 53.5% of shoot and 29.7% of root compared to control) was observed at higher concentrations. Higher biological activities (microbial viable counts, water-soluble phenolic compounds, dehydrogenase activity) and PAHs degradation rates were detected in planted soils than unplanted controls. After harvest, 91.7-97.8% of phenanthrene and 70.8-90.0% of pyrene had been degraded in the planted soils, which were 1.88-3.19% and 8.85-20.69% larger than those in corresponding unplanted soils. This enhanced dissipation of target PAHs in planted soils might be derived from increased biological activity in the rhizosphere. The results of the present study suggest that the presence of tall fescue roots were effective in promoting the phytoremediation of PAHs contaminated soil.

Enhanced phytoremediation potential of polychlorinated biphenyl contaminated soil from e-waste recycling area in the presence of randomly methylated-β-cyclodextrins.

The crude recycling of electronic and electric waste (e-waste) is now creating soil pollution problems with organic compounds such as polychlorinated biphenyls (PCBs). The present study aimed to compare the phytoremediation potential of four plant species (rice, alfalfa, ryegrass and tall fescue) for PCBs contaminated soil from Taizhou city, one of the largest e-waste recycling centers in China. In addition, the enhanced effects of randomly methylated-beta-cyclodextrins (RAMEB) on PCBs phytoremediation potential were evaluated. Higher PCBs removal percentages of 25.6-28.5% in rhizosphere soil were observed after 120 days, compared with those of the non-rhizosphere (10.4-16.9%) and unplanted controls (7.3%). The average PCBs removal percentages of four plant species increased from 26.9% to 37.1% in the rhizosphere soil with addition of RAMEB. Meanwhile, relatively high microbial counts and dehydrogenase activity were detected in planted soils and a stimulatory effect by RAMEB addition was found. The present study indicated that all the plant candidates were feasible for phytoremediation of PCBs contaminated soil from the e-waste recycling area, and tall fescue with RAMEB amendment seemed as a promising remediation strategy. High PCBs removal percentage was due to the increased PCBs bioavailability as well as biostimulation of microbial communities after plantation and RAMEB addition.

Hormesis response of marine and freshwater luminescent bacteria to metal exposure

The stimulatory effect of low concentrations of toxic chemicals on organismal metabolism, referred to as hormesis, has been found to be common in the widely used luminescence bioassay. This paper aims to study the hormesis phenomenon in both marine and freshwater luminescent bacteria, named Photobacterium phosphorem and Vibrio qinghaiensis. The effects of Cu (II), Zn (II), Cd (II) and Cr (VI) on luminescence of these two bacteria were studied for 0 to 75 minutes exposure by establishing dose- and time-response curves. A clear hormesis phenomenon was observed in all four testing metals at low concentrations under the condition of luminescence assays.

Levels and distributions of polycyclic aromatic hydrocarbons in agricultural soils in an emerging e-waste recycling town in Taizhou area, China

The present study investigated the levels, distributions, profiles and possible sources of polycyclic aromatic hydrocarbons (PAHs) in agricultural soils around Zeguo, an emerging e-waste recycling town in Taizhou area, China. Concentrations of sixteen USEPA priority PAHs and soil organic matter were analyzed in 59 agricultural soil samples. The total PAH concentrations ranged from 262.6 to 3,420.2 μg/kg, with the average values in a gradually descending order: agricultural soil near e-waste recycling plants and workshops (1,336.0 μg/kg) > agricultural soil in villages with open burning and e-waste recycling activities (945.8 μg/kg) > agricultural soil in other villages (466.5 μg/kg). Analysis of the distribution patterns of the PAHs showed that phenanthrene, anthracene, fluoranthene and pyrene were the dominant species. The significant correlations among individual, low-molecular-weight (LMW), high-molecular-weight (HMW) and total PAHs and the very similar PAH profiles in the three sampling areas indicated that the PAHs might have come from similar sources. The ratios of Anthracene to sum of Anthracene and Phenanthrene concentrations (Ant/(Ant+Phe)) and fluoranthene to sum of fluoranthene and pyrene concentrations (Flt/(Flt+Pyr)) were calculated and principal component analysis (PCA) was performed and the results suggested that an anthropogenic source such as the combustion of a petroleum product or coal during the e-waste recycling process seemed to be the main source of PAHs in the Zeguo agricultural soil. In conclusion, soils taken from Zeguo agricultural areas were considered to be heavily polluted, and the emerging e-waste recycling activities had definite effects on PAH soil concentrations.

Levels, Distributions and Profiles of Polychlorinated Biphenyls in Paddy Fields from Two Towns in a Typical Electronic Waste Recycling Area of Eastern China

Surface soil (0∼10 cm) samples from Zeguo and Wenqiao, two towns in a typical electronic waste (E-waste) recycling area of eastern China, were collected and analyzed for polychlorinated biphenyls (PCBs). The mean concentration of total 58 PCBs congeners in Zeguo and Wenqiao were 62.8 and 144.8 μg·kg−1 (dry weight), respectively, with a range from 13.3 to 242.2, and 27.1 to 526.3 μg·kg−1, respectively. The concentrations of total PCBs decreased in the order of paddy fields near E-waste recycling workshops (NEW) > paddy fields near E-waste recycling plants (NEP) > paddy fields in open burning villages (OBV) > paddy fields in other villages (OV). The difference of PCBs composition in OBV or OV areas between Zeguo and Wenqiao indicated that the PCBs concentration in paddy fields were affected significantly by atmospheric transportation and direct discharge. Furthermore, the composition of PCBs in Zeguo and Wenqiao was different, Zeguo soils near the E-waste recycling working plants and workshops contained more high chlorinated PCB congeners and less low chlorinated PCBs compared with Wenqiao soil, possibly indicating the difference of PCBs major source were different. The results of present study suggested that the soil in Zeguo and Wenqiao towns was heavily polluted by PCBs because of E-waste recycling activities. Compared with the large scale E-waste recycling plants, the small simple household workshops have been contributing more PCBs pollution to the soil environment. However, due to the lack of data about the human exposure in this area, it is unconvincing that the analysis of soil samples collected from the crude and inappropriate E-waste recycling area would pose significant threat to human. It is expected to learn much more about the extent and long-term effects of these particular E-waste activities on environmental and human health.