Bioremediation of pesticide-contaminated agricultural soils using native microbial consortia

Abstract:

Bioremediation, in its simplest form, is the use of living microorganisms to break down or transform environmental pollutants into less harmful compounds. Applied to agricultural soils carrying chlorpyrifos and endosulfan residues, the approach holds out the promise of cost-effective clean-up without the collateral damage of soil washing or chemical oxidation. This research evaluated three native microbial consortia isolated from long-history agricultural soils of Changsha and Chengdu districts for their ability to degrade chlorpyrifos in contaminated soil. Consortium A comprised two Pseudomonas strains; Consortium B was a four-strain Bacillus mix; Consortium C combined A, B and two Aspergillus isolates. Field-collected soil was artificially spiked to 100 mg kg⁻¹ chlorpyrifos, held in microcosms at 28 °C and 60 percent field capacity, and sampled at 15-day intervals over 60 days. Residual pesticide levels dropped to 46.3, 34.7 and 18.6 mg kg⁻¹ for Consortia A, B and C respectively, against 82.4 mg kg⁻¹ in the untreated control. Consortium C delivered 81.4 percent degradation and pushed residual levels well below the 50 mg kg⁻¹ regulatory ceiling. Microbial biomass carbon recovered to 168 percent of the pre-contamination baseline under Consortium C, and dehydrogenase activity rose by 2.4-fold. First-order kinetics gave a half-life of 19.3 days for Consortium C against 103.2 days for the untreated control. The findings argue that locally isolated microbial consortia, properly composed, can restore pesticide-contaminated soils to agronomic and regulatory acceptability within two months.