Chemical and microbiological assessment of pendimethalin-contaminated soil after treatment with Fentonʹs reagent

This study assessed chemical effects and microbial response after Fentonʹs treatment of pendimethalin contaminated soils. The efficiency of the rapid chemical transformation of pendimethalin varied from 25% to greater than 90%. The highest efficiency was associated with a soil having comparatively low organic matter and low acid neutralizing capacity. This is consistent with the role of organic matter as a free radical scavenger and the optimum formation of free radicals at low pH. Potential heterotrophic activity, as measured by glucose mineralization, decreased with increasing pendimethalin concentration, but this inhibitory effect was removed after Fentonʹs treatment. Treatment also released BOD, COD, TOC, and nitrate into solution. The organic matter released into solution was biodegradable and served as a substrate for subsequent microbial growth. Analysis of the microbial population growing in the Fentonʹs treated soil leachates showed an overall decrease in (culturable) heterotrophic diversity, but an increase in the concentration of Pseudomonas species. These results suggest that Fentonʹs treatment of pendimethalin contaminated soil created favorable conditions for microorganisms desirable for bioremediation.