Microbial characteristics of a Zn and Cd contaminated soil chemically amended for growth of a heavy metal-hyperaccumulating plant

Abstract

A pot experiment was conducted to examine the effects of chemical amendment on the microbial characteristics of a heavy metal-contaminated soil used for the growth of a hyperaccumulating plant, Sedum alfredii Hance. The results show that the abundance of the soil microbes bacteria, actinomycetes and fungi) is significantly (at p=0.01) related to the removal rate of Zn and Cd from the soil, the dry biomass of Sedum alfredii Hance, Cmic, and Cmic/Nmic except that the number of fungi is only significantly (at p=0.05) related to Cmic/Nmic. All the soil treatments enhanced the activities of soil microbes. In general, the increase in activity of different types of microbes was in the following decreasing order: bacteria>actinomycetes>fungi. Of all the treatments, Treatment 7 (mixing 1 000 g of the contaminated soil with 6 g of red mud, 15 g of zeolitic rock powder and 15 g of biosolids) formed a best soil medium for the growth of the soil microbes. The microbial biomass C concentration in Treatment 7 was as high as 345.64 mg·kg-1, which was statistically different from other treatments and represented the highest value among all the treatments in this experiment. This work has implications for the future development of a combined chemical and biological remediation technique for the cleanup of Zn and Cd contaminated soils.