Effect of heavy metals on microbial communities and enzymatic activity in soil column experiment

Abstract

The experiment of model soil columns was performed in order to assess the functional diversity changes of soil microbial communities and enzymatic activity under the conditions of critical heavy metals (Pb, Zn and Cu) accumulation. The extremely high concentrations of contaminants were detected in the upper 0 – 0.1 m soil layer wherein the average total content of lead, copper and zinc reached up to 839, 773 and 844 mg kg⁻¹ respectively. Such a high contamination level reduced counts of all investigated microbial groups and significantly lowered enzymes activity when compared to respective uncontaminated soil estimated. In particular high susceptibility of actinomycetes, oligonitrophic and mineral N assimilating bacteria suggests about low adaptable possibilities of these microorganisms while fungi and spore-forming bacteria seemed possessing much more effective defensive mechanisms leading to a higher survival under stress environmental conditions. The evident decrease of soil biological activity was found to be in this descending order: Dehydrogenase (95 – 98%) → urease (65 – 97%) → saccharase (57 – 77%) → soil respiration (38 – 65%) as compared with natural soil.

Keywords:

• Soil column
• lead
• copper
• zinc accumulation
• microorganisms
• soil enzymatic activity

Acknowledgments

This work was financially supported by the Lithuanian State Science and Studies Foundation (grant No. K-070).