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| Microbial activity and community diversity in a variable charge soil as affected by cadmium exposure levels and time |
| Jia-li SHENTU, Zhen-li HE, Xiao-e YANG, Ting-qiang LI |
| MOE Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310029, China; University of Florida, Institute of Food and Agricultural Sciences, Indian River Research and Education Center, Fort Pierce, FL 34945, USA |
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Abstract Effects of cadmium (Cd) on microbial biomass, activity and community diversity were assessed in a representative variable charge soil (Typic Aquult) using an incubation study. Cadmium was added as Cd(NO3)2 to reach a concentration range of 0~16 mg Cd/kg soil. Soil extractable Cd generally increased with Cd loading rate, but decreased with incubation time. Soil microbial biomass was enhanced at low Cd levels (0.5~1 mg/kg), but was inhibited consistently with increasing Cd rate. The ratio of microbial biomass C/N varied with Cd treatment levels, decreasing at low Cd rate (<0.7 mg/kg available Cd), but increasing progressively with Cd loading. Soil respiration was restrained at low Cd loading (<1 mg/kg), and enhanced at higher Cd levels. Soil microbial metabolic quotient (MMQ) was generally greater at high Cd loading (1~16 mg/kg). However, the MMQ is also affected by other factors. Cd contamination reduces species diversity of soil microbial communities and their ability to metabolize different C substrates. Soils with higher levels of Cd contamination showed decreases in indicator phospholipids fatty acids (PLFAs) for Gram-negative bacteria and actinomycetes, while the indicator PLFAs for Gram-positive bacteria and fungi increased with increasing levels of Cd contamination.
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Received: 24 December 2007
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