Title: Interactive effects of Cd and PAHs on contaminants removal from co-contaminated soil planted with hyperaccumulator plant Sedum alfredii Authors
|Wang, Kai -|
|Zhu, Zhiqiang -|
|Haung, Huagang -|
|Li, Tingqiang -|
|He, Zhenli -|
|Yang, Xiaoe -|
Submitted to: Journal of Soils and Sediments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 10, 2012
Publication Date: February 10, 2012
Citation: Wang, K., Zhu, Z., Haung, H., Li, T., He, Z., Yang, X., Alva, A.K. 2012. Interactive effects of Cd and PAHs on contaminants removal from co-contaminated soil planted with hyperaccumulator plant Sedum alfredii. Journal of Soils and Sediments. 12:556-564. Interpretive Summary: Soils with multiple contaminants, i.e. heavy metals and organic contaminants, do occur in various regions of the world. Developing innovative strategies for remediation of co-contaminated soils is a major priority. Phytoremediation is a strategy of growing hyperaccumulator plants in contaminated soils and removal of biomass containing the contaminant from the contaminated soil. Most published research reports the application of this strategy for remediation of single contaminant soils. Evaluation of this strategy for remediation of co-contaminated soils is rather limited. The use of Cadmium (Cd) hyperaccumulator plant, Sedum alfredii, on remediation of Cd (0.92 and 6.38 mg/kg) and dissipation of polycyclic aromatic hydrocarbons (PAH; i.e. 25 and 150 mg/kg soil phenanthraline (PHE) or pyrene (PYR)) co-contaminated soil was investigated in this pot study. The elevated soil Cd increased the Sedum biomass when no PAH was present in the soil. The biomass decreased when the soil was co-contaminated with both concentrations of PHE or PYR. The dissipation of both PAHs was not influenced by Sedum plant. The dissipation of PYR was lower at elevated Cd concentration in the soil. Therefore, in Cd and PAH co-contaminated soil the negative effect of Cd on microbial activity may influence the biological dissipation of PAH.
Technical Abstract: Soil contamination by multiple organic and inorganic contaminants is common but its remediation by hyperaccumulator plants is rarely reported. The growth of a cadmium (Cd) hyperaccumulator Sedum alfredii and removal of contaminants from Cd and polycyclic aromatic hydrocarbons(PAHs) co-contaminated soil were reported in this study. Soil slightly contaminated by Cd (0.92 mg/kg DW) was collected from a vegetable field in Hangzhou and was spiked with two levels (0 and 6 mg/kg DW) of Cd and three levels (0, 25, and 150 mg/kg DW) of phenanthrene (PHE) or pyrene (PYR). A pot experiment was conducted in a greenhouse using S. alfredii with unplanted controls for 60 days. Shoot and root biomass of plants, dehydrogenase activity (DHA), and microbial biomass carbon in the soil weremeasured. Concentrations of Cd and PAHs in the plant and soil were determined. Elevated Cd level (6.38 mg/kg DW) increased S. alfredii growth. The presence of PAHs decreased the stimulatory effects of Cd on plant biomass and Cd concentrations in shoots in Cd spiked soil, thus decreasing Cd phytoextraction efficiency. Cadmium removal by S. alfredii after 60 days of growth varied from 5.8% to 6.7% and from 5.7% to 9.6%, in Cd unspiked and spiked soils, respectively. Removal rate of PAHs in the soil was similar with or without the plants. Removal rate of PYR decreased at the elevated Cd level in the soil. This appears to be due to a decrease in soil microbial activity. This is confirmed by a decrease in DHA, which is a good indicator of soil microbial activity. Our results demonstrate that S. alfredii could effectively extract Cd from Cd-contaminated soils in the presence of PHE or PYR; however, both PAHs exhibited negative effects on phytoextraction of Cd from Cd spiked soil (6.38 mg/kg DW). S. alfredii is not suitable for remediation of PAHs. The effects of Cd and PAHs concentrations on the removal rate of PAHs appear to be attributed to the changes in microbial activities in the soil.