Microbial indicators for assessing the adverse impact of technical-grade hexachlorocyclohexane on soil quality
Technical-grade hexachlorocyclohexane (HCH) has been widely used for human health and agricultural purposes. Consequently, HCH residues have entered the soil ecosystem with concomitant deleterious effects on soil quality. The aim of this study was to assess the impact of HCH on soil microbial properties as biological indicators of soil quality. To this end, non-polluted soil was spiked with different amounts of a heavily HCH-polluted soil in order to obtain a concentration gradient between 0 and 1,500 mg HCH kg-1 dry matter soil. The mixtures were incubated under laboratory conditions for 2 months. Dehydrogenase activity, fluorescein diacetate hydrolysis activity (FDA), basal respiration, substrate-induced respiration (SIR), microbial biomass carbon, metabolic potential, and the soil quality index were negatively affected by increasing HCH concentrations in soil, in many cases following an exponential pattern. FDA and SIR appear a priori suitable indicators for the impact of HCH on soil microbial properties and, hence, soil quality.