Impact of long-term organochlorine pesticide contamination on soil microbial communities and enzymatic activity

Abstract Soil microorganisms play a crucial role in maintaining ecosystem stability and soil fertility; however, long-term pesticide contamination can significantly disrupt microbial functioning. The present study provides a comprehensive assessment of the microbiological and biochemical status of soils chronically contaminated with pesticides at a chemical burial site and adjacent areas. Soil samples were collected from several zones within the landfill and surrounding territories, including a reference site with minimal anthropogenic impact. The abundance and structure of major physiological groups of microorganisms were determined using culture-based methods, while soil enzymatic activities (catalase, peroxidase, polyphenol oxidase, and invertase) were assessed as indicators of biological activity. Residual concentrations of organochlorine pesticides were analyzed using gas chromatography with an electron capture detector. The results revealed a pronounced suppression of enzymatic activity and a significant reduction in microbial abundance in contaminated soils compared to the control. The most severe disturbances were observed in the central, western, and eastern zones of the burial site, characterized by elevated concentrations of dieldrin and endrin exceeding permissible levels by tens to hundreds of times. Bacterial communities dominated the microbial structure, whereas fungi and actinomycetes were strongly suppressed, indicating degradation of soil ecological functions. Spatial heterogeneity of biological responses suggested partial adaptation or limited recovery in peripheral zones. These findings demonstrate that even localized pesticide contamination leads to persistent impairment of soil microbial activity and enzymatic functioning. The results emphasize the importance of integrated microbiological and biochemical indicators for environmental monitoring and provide a scientific basis for the development of soil bioremediation strategies in chronically contaminated areas.

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