Influence of combined pollution of antimony and arsenic on culturable soil microbial populations and enzyme activities

The effects of both combined and single pollution of antimony (Sb) and arsenic (As) in different concentrations on culturable soil microbial populations and enzyme activities were studied under laboratory conditions. Joint effects of both Sb and As were different from that of Sb or As alone. The inhibition rate of culturable soil microbial populations under Sb and As pollution followed the order: bacterial > fungi > actinomycetes. There existed antagonistic inhibiting effect on urease and acid phophatase and synergistic inhibiting effect on protease under the combined pollution of Sb (III) and As (III). Only urease appeared to be the most sensitive indicator under Sb (V) and As (V) pollution, and there existed antagonistic inhibiting effect on acid phophatase and synergistic inhibiting effect on urease and protease under Sb (V) and As (V) combined pollution at most time. In this study, we also confirmed that the trivalent states of Sb and As were more toxic to all the microbes tested and more inhibitory on microbial enzyme activities then their pentavalent counterparts. The results also suggest that not only the application rate of the two metalloids but also the chemical form of metalloids should be considered while assessing the effect of metalloid on culturable microbial populations and enzyme activities. Urease and acid phosphatase can be used as potential biomarkers to evaluate the intensity of Sb (III) and As (III) stress.