Effects of Pb, Cu, Sb, In and Ag contamination on the proliferation of soil bacterial colonies, soil dehydrogenase activity, and phospholipid fatty acid profiles of soil microbial communities

Because of concerns about the toxicity of lead (Pb), the use of antimony (Sb), indium (In), silver (Ag), and other heavy metals are on the increase as its replacement in many kinds of industrial products, particularly in solders. In the present study, effects of Pb, Cu, Sb, In, and Ag contamination on bacterial growth inhibition in PTYG (peptone, tryptone, yeast extract, glucose) liquid media, soil dehydrogenase activity, concentrations and compositions of phospholipids fatty acids (PLFA) were assessed. Survival rates of bacterial colony-forming units were lower in the presence of various concentrations of Pb, Cu, Sb, In, Ag, Zn and Ni than in their absence. Soil dehydrogenase activity in Arenic Eutric Regosol was much decreased when the concentrations of Pb and Cu were 50 times their natural abundance and when Ag was at 100 times its natural abundance. Soil dehydrogenase activity was also much decreased in Eutric Cambisol when Cu was 50 times, and Ag was 100 times, their natural abundances. In contrast, Sb and In did not affect soil dehydrogenase activity at any concentration or in any type of soil. Concentrations and composition of PLFA did not show any conspicuous change. Cu, Sb, In and, especially, Ag, which are increasingly being used to replace Pb, should be considered to be potentially toxic. However, when evaluating the impact of waste metals on the environment, heavy metal solubility, speciation and interaction with organic matter in soil must be considered.