Abstract
Triazine herbicides are widely used both in Brazil and internationally and are frequently detected in natural environments and drinking water. This study assesses atrazine degradation through solar radiation under tropical conditions and determines the toxicity of the intermediates. Atrazine degradation is tested through ultrapure water, humic acid solution and natural water experiments, with exposure to sunlight to simulate a natural environment. A yeast estrogen screen (YES) assay and Artemia salina test are carried out during the abiotic degradation. The atrazine degradation depends on the radiation intensity, since the experiments conducted in the summer reached 50% after ca. 17 days. No significant variations in this herbicide concentration are observed after 90 days of exposure in the fall. Atrazine degradation is observed only in humic acid and is responsible for indirect photolysis. Intermediates, namely, desethylatrazine (DEA) and deisopropylatrazine (DIA), are identified and quantified at the μg L–1 level. Thus, with the degradation of atrazine in water, the medium toxicity may decrease, since DEA and DIA have mean effective concentrations that kill 50% of Artemia salina (EC50) similars to atrazine (13 mg L–1). No estrogenic activity in the YES is detected for atrazine and its metabolites. These findings evidence that radiation intensity and organic substances in tropical countries influence the half-life of pesticides in aquatic environments.
Highlights
The use of chemical compounds for insect pest control and food crop protection has been a common practice for centuries
The atrazine degradation results for fall and summer are displayed in Figures 2 and 3 and Table 5
Degradation assays confirm that indirect photolysis is the mechanism responsible for pesticide degradation in summer and fall, triggered by humic acids dissolved in the matrix
Summary
The use of chemical compounds for insect pest control and food crop protection has been a common practice for centuries. The analytical curves of the ATZ, DEA and DIA standards were completed for all matrices (type I ultrapure water, HA solution and natural river water) and prepared at 1.30, 1.00, 0.70, 0.40 and 0.10 mg L–1 concentrations. After counting the live larvae, the mean effective concentrations (EC50) of ATZ and its degradation products, DEA and DIA, which result in the death of 50% of exposed organisms, were determined. In this case, the effect was acute, as observed by the test organism lethality.
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