Effects of surfactants on the photolysis of chlorothalonil on pepper (Capsicum annuum var. grossum Sendt).

Chlorothalonil is a widely used fungicide on pepper and other vegetables in China. The present study was aimed to evaluate effects of three different surfactants, sodium dodecyl sulfonate (SDS), Span-20, and cetyltrimethylammonium bromide (CTAB), on the photolysis of chlorothalonil on peppers under irradiation of either high-pressure mercury lamp (HPML) or sunlight inside and outside greenhouse. Results showed that both SDS and Span-20 at a low concentration exhibited a photosensitization effect on the photolysis of chlorothalonil under HPML. Such effect gradually decreased with increasing concentrations of either surfactant prior to photoquenching effects observed. In contrast, CTAB showed a photoquenching effect on chlorothalonil photolysis, which was gradually enhanced with an increasing CTAB concentration. SDS, Span-20, and CTAB had consistent effects on the photolysis of chlorothalonil under sunlight as those observed under HPML irradiation. The use of appropriate surfactants as pesticide additives at optimal concentrations could decrease the residue of pesticide in agricultural food and improve food safety.