ABSTRACT
Our study aimed at acquiring information about the biological effect of pesticides and their degradates produced by UV-treatment on microbiological activity. Five photosensitive pesticides (carbendazim, acetochlor, simazine, chlorpyrifos, EPTC) and six representative soil microbes (Bacillus subtilis, Pseudomonas fluorescens, Mycobacterium phlei, Fusarium oxysporum, Penicillium expansum, Trichoderma harzianum) were applied throughout our model experiments. The antimicrobial effects of the pesticides and their degradates were assessed with filter paper disk method. The antimicrobial effect of the degradation products exhibited marked differences in terms of pesticide types, irradiation time, and the test organisms. Acetochlor and its photolytic degradation products were found to be more toxic to bacteria than fungi. All the three bacteria proved to be sensitive to the basic compound and its degradation products as well. The end product of carbendazim was weakly antibacterial against P. fluorescens and B. subtilis but strongly antifungal against T. harzianum. Chlorpyrifos and its end product inhibited neither test organisms, but the degradates hindered the growth of four of them. The basic compound of EPTC and the degradates of simazine exhibited significant toxicity to the test bacteria. It might be claimed that the pesticide photodegradation may result in significant changes in soil microbiota, as well as formation of biologically harmful degradates.
Subject(s)
Anti-Infective Agents/radiation effects , Anti-Infective Agents/toxicity , Bacteria/drug effects , Fungi/drug effects , Pesticides/radiation effects , Pesticides/toxicity , Ultraviolet Rays , Bacteria/growth & development , Benzimidazoles/radiation effects , Benzimidazoles/toxicity , Carbamates/radiation effects , Carbamates/toxicity , Chlorpyrifos/radiation effects , Chlorpyrifos/toxicity , Fungi/growth & development , Simazine/radiation effects , Simazine/toxicity , Soil Microbiology , Soil Pollutants/radiation effects , Soil Pollutants/toxicity , Thiocarbamates/radiation effects , Thiocarbamates/toxicity , Toluidines/radiation effects , Toluidines/toxicityABSTRACT
The photodegradation of three triazines, atrazine, simazine, and prometryn, in aqueous solutions and natural waters using UV radiation (lambda > 290 nm) has been studied. Experimental results showed that the dark reactions were negligible. The rate of photodecomposition in aqueous solutions depends on the nature of the triazines and follows first-order kinetics. In the case of the use of hydrogen peroxide and UV radiation, a synergistic effect was observed. The number of photodegradation products detected, using FIA/MS and FIA/MS/MS techniques, suggests the existence of various degradation routes resulting in complex and interconnected pathways.
