Photochemical degradation of pyrazosulfuron-ethyl in aqueous solution

Abstract

Este trabalho descreve o comportamento fotoquímico do pirazosulfuronato de etila em soluções aquosas. A fotodegradação do pirazosulfuronato de etila foi investigada pela primeira vez em dois comprimentos de onda de irradiação diferentes e valores de pH variando de 2,00 a 10,00. Os resultados mostram que a taxa de fotodegradação foi mais rápida em meio ácido do que em meio básico, quando pyrazosulfuron-etil estava na forma neutra. Os tempos de meia-vida do pirazosulfuronato de etila sob luz ultravioleta e luz solar simulada foram 27,17 e 153,33 min, respectivamente. As reações seguiram cinética de primeira ordem. As rotas de degradação foram propostas de acordo com os resultados de identificação dos fotoprodutos: clivagens carbono-enxofre e nitrogênio-enxofre e fotohidrólise da ponte de sulfonilureia. Concluiu-se que comportamentos de fotodegradação podem ocorrer dentro da família de sulfonilureia, dependendo dos valores de pH da solução aquosa e dos comprimentos de onda de irradiação.This report describes photochemical behaviors of pyrazosulfuron-ethyl in aqueous solution. The photodegradation of pyrazosulfuron-ethyl for the first time was investigated in aqueous solution at two different irradiation wavelengths and pH values ranging from 2.00 to 10.00. Results show that the rate of photodegradation was faster in acidic medium than that in basic medium, when pyrazosulfuron-ethyl was in neutral form. The half-lives of pyrazosulfuron-ethyl under ultra-violet light and simulated sunlight were found to be 27.17 and 153.33 min, respectively. The reactions followed first-order kinetics. The degradation pathways were proposed according to the identification results of photoproducts: carbon-sulfur and nitrogen-sulfur cleavages and photohydrolysis of the sulfonylurea bridge. It was concluded that photodegradation behaviors can occur within the sulfonylurea family, depending on the pH values of aqueous solution and the irradiation wavelengths.

Interactive Application of Zinc and Herbicides Affects Broad-leaved Weeds, Nutrient Uptake, and Yield in Rice

“…Such herbicides inhibit acetolactate synthase (ALS), a key enzyme in the pathway of branched-chain amino acids In each column, numbers followed by the different letters are statistically significant at 0.05 level of probability Zn− and Zn+, without Zn and with Zn addition, respectively; N, nitrogen; P, phosphorus; K, potassium ±Standard error value In each column, numbers followed by the different letters are statistically significant at 0.05 level of probability Zn− and Zn+ without Zn and with Zn addition, respectively; N, nitrogen; P, phosphorus; K, potassium ±Standard error value (leucine, isoleucine, and valine) in plants (Ray 1984). As postemergence herbicides, both of azimsulfuron (Pathak et al 2011) and pyrazosoulfuron-ethyl (Wang et al 2013) are absorbed by roots and leaves, and also inhibit the enzyme acetolactate synthase in susceptible weed plants. Based on the mechanism of action of both Zn and applied herbicides, the growth and nutritional status of rice weeds were negatively affected (Table 4).…”

The role of indirect photochemical degradation in the environmental fate of pesticides: a review

“…57 For several herbicides in this class, there is only information on the direct photodegradation rates and mechanisms. These herbicides include amindosulfuron, 302 cinosulfuron, 311,312 upyrsulfuron-methyl, 314 nicosulfuron, 317 pyrazosulfuron-ethyl, 318 rimsulfuron, 319 triasulfuron, 311,312,323 and triusulfuron-methyl. 326 As described below, for several sulfonylureas compounds which have been studied in more detail, direct photodegradation is oen relatively slow and pH-dependent.…”

Dissipation and fate of ready mix combination of pyrazosulfuron-ethyl and pretilachlor in rice field

“…It can be applied as pre-or early post-emergence and has outstanding activity against a broad spectrum of annual and perennial weeds. Fate and persistence of sulfonylurea herbicides in soil are widely affected by the soil acidity, temperature, moisture content, soil microbial diversity and biochemical activity (Wang et al 2013).It was almost unstable under acidic environment and hydrolysis of sulfonamide linkages the prime degradation path of pyrazosulfuron-ethyl in water (Singh and Singh 2013). It dissipates rapidly from puddled rice soil with ahalf-life1.9 days in field water and 11 days in soil (Ishii et al 2004).…”