Effect of Metals Contamination on Soil Microbial Diversity, Enzymatic Activity, Organic Matter Decomposition and Nitrogen Mineralisation (A Review)

Abstract

Soil is home to remarkable diversity of life from microbes to moles and a well-established ecosystem among these different organisms exists. Microorganisms either independently or in association with other organisms are playing very important role in the plant nutrients recycling. Soil metal concentrations above certain limits disrupt this ecosystem and as a result plant nutrient cycling process. Metal contamination in soils cause proportions of some groups of microorganisms to increase than the others. Compared with bacteria certain groups of fungi are less affected by soil metal pollution. Phospholipid fatty acid (PLFA) measurements in metal contaminated soils show that within bacterial population, metals are more toxic to gram-positive than gram-negative bacteria. Significant reductions in enzymatic activities occur in soils contaminated with metals and generally metals are more toxic to intra-cellular enzyme activities (e.g. dehydrogenase) than extra-cellular activities (e.g. phosphatase). Similarly, enzymes produced by bacteria are more affected by metal contamination than those produced by fungi. Organic matter decomposition and nitrogen mineralisation, which are carried out by various groups of microorganisms can also be affected by increased metal concentrations in the soils.

The use of bentonite and organic amendments for remediation of Cd contaminated fields: An environmental perspective

“…In the present study, the Shannon and Simpson indices were increased to a certain extent by bentonite addition alone and in combination with organic amendments, with the significant increase (p < 0.05) following BMR1 and BMR2 treatment, relative to CK. On the basis of the sensitivity of community population, structure, and even diversity to heavy metals, soil microbial community are regarded as a valuable indicator for the remediation progresses of heavy metal contaminated soils (Khan, 2000). Studies…”