Abstract

The effects of ammonium-rich and heavy-metal air pollution produced by the industrial enterprises at Navoiy (Uzbekistan) on soil freeliving nematodes and microbial population activities was investigated in soil samples collected in a 5-km radius surrounding the industrial enterprises. At each location (n=4), soil samples were collected from the upper layer (0–10 cm) for determination of soil moisture (SM), total organic carbon (Corg), total soluble nitrogen (TSN), soil electrical conductivity (EC) and cations (Ca2+, K+, Na+). Heavy metals (As, Cu, Pb, Zn), soil basal respiration (BR), microbial biomass (Cmic) and nematode populations were determined. The highest level of TSN was found near the industrial enterprises, with 23.8 and 24.0 mg/kg at NavoiAzot and NavoiGRES, respectively. Soil sample pH was found to be weakly alkaline, with levels ranging between 7.9 and 8.1. Mean soil moisture content varied from 0.75% to 0.93% of the wet weight, without any significant differences between the sampling stations. The heavy metals As, Cu, Pb and Zn were accumulated in the upper soil layer. A significant difference was found between soil heavy-metal content for Cu ( pb0.0005) and As ( pb0.02). Basal respiration and microbial coefficient (Cmic/Corg) were found to be significantly negatively correlated with Cu and As soil content. A significantly positive correlation was found between the Cd concentration and the metabolic quotient (qCO2) ( pb0.003). No significant correlation was observed between the soil microbial population and total soluble nitrogen. Furthermore, the qCO2, which is a known ecophysiological index for the soil microbial population, was found to be correlated with the total number of nematodes in general and with the bacteriovore-feeding group in particular. No significant correlation was observed between the soil microbial population and total soluble nitrogen.