Photochemical Oxidation of Terbufos

Abstract

We studied the photochemical oxidation of an organophosphorus pesticide, terbufos, in surface waters because its oxidation products are of concern. Terbufos sulfoxide and terbufos sulfone have toxicities for aquatic organisms similar to those of the parent compound. We measured a photolysis rate constant under natural sunlight conditions in distilled water of 0.68 Ϯ 0.17/h near Clemson, South Carolina, USA. Actinometer studies resulted in a mean reaction quantum yield for terbufos of 5.8 ϫ 10 Ϫ3 . The measured half-life of 64 min is considerably faster than any of the other chemical or biochemical oxidation half-lives in soil or hydrolysis half-lives reported in the literature. Photolysis should be considered in evaluating the risk of terbufos to surface waters and aquatic organisms.

Titanium dioxide-mediated heterogeneous photocatalytic degradation of terbufos: Parameter study and reaction pathways

“…Household uses include the control of cockroaches, houseflies, and termites along with the protection of plants of horticultural interest [5,6]. Terbufos is very toxic to aquatic organisms, with an acute LC50 for fish species ranging from 0.77 to 20 ppb [7,8]. Although terbufos was one of the extremely hazardous substances on the United States' Superfund National Priority List and was a candidate for the Draft Drinking Water Contaminant List that followed the Safe Drinking Water Act (1997), the United States alone consumed 4.5 millions pounds of terbufos in corn products in 1996 [9].…”

A low concentration of atrazine does not influence the acute toxicity of the insecticide terbufos or its breakdown products to Chironomus tepperi

“…Many studies do not consider the toxic effects of pesticide transformation/degradation products due, to a presumption that they are of little or no toxicological relevance (Day 1991). Terbufos is transformed via microbial or chemical oxidation or by UV irradiation into the sulfoxide and sulfone products (Chapman et al 1982;Lee et al 1999;USEPA 2006). The higher water solubilities of terbufos sulfoxide and terbufos sulfone relative to the parent compound indicate a likelihood for these contaminants to enter surface and ground water (USEPA 2006).…”