Abstract

The effect of ammonium-rich and heavy-metal air pollution produced by the Navoiy industrial enterprises on soil free-living nematodes and microbial population activities was investigated in soil samples collected in a 5-km radius surrounding the industrial enterprises. At each location, soil samples were collected (n=4) from the upper layer (0-10 cm) for the 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 population were determined. Soil pH was found to be weakly alkaline, with levels ranging between 7.9 to 8.1. Mean soil moisture content varied from 0.75 to 0.93%, without any significant differences between the sampling stations. The Cu, Pb, and As were accumulated in the upper soil layer. A significant difference was found between soil heavy metal content for Cu (p<0.0005) and As (p<0.02). BR 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) (p<0.003). The highest level of TSN was found near the industrial enterprises, with 23.8 and 24.0 mg kg-1 at NavoiAzot and NavoiGRES, respectively. No significant correlation was observed between the soil microbial population and TSN. 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 bacterivore-feeding group in particular. Nitrogen pollution significantly influenced the total number of nematodes and the distribution of nematode communities. TSN was correlated with the total density of nematodes (p<0.05) and plant-parasites trophic group (p<0.02). Results of the present study elucidate the direct and indirect effects of industrial pollution on soil microbial biomass and the nematode community around the Navoiy industrial complex.