Sunlight Nitrate-Induced Photodegradation of Chlorotoluron: Evidence of the Process in Aquatic Mesocosms

Abstract

The nitrate-induced photodegradation of chlorotoluron was demonstrated to occur efficiently in natural water through two series of experiments in outdoor aquatic mesocosms. During the first campaign, it was shown that the pesticide degradation kinetics was clearly dependent on nitrate concentration. This parameter also influenced the accumulation of the first- and second-generation byproducts, including predominantly N-terminus oxidation products and nitro-derivatives of the phenyl ring. The latter compounds, specific to the NO3- -induced photoprocess, appeared particularly abundant as compared to laboratory-simulated sunlight irradiation conditions. During the second campaign, a dual day-night sampling was achieved, which demonstrated the almost exclusive role of photodegradation versus biodegradation.

Photodegradation of the azole fungicide climbazole by ultraviolet irradiation under different conditions: Kinetics, mechanism and toxicity evaluation

“…While HA scavenged radicals as light-absorbing species and result in a quenching effect on the reaction system [33,38], so the higher of the HA concentration, the more evident of the inhibitory effects, which was consistent with the previous reports [19,39]. In contrast, a promoting effect of 10 mg/L NO 3 − on the photodegradation of CZ was discovered, which might be caused by the generation of nitrogen reactive species (NRS) and ROS from NO 3 − under the UV-254 nm [40,41]. However, 5 or 50 mg/L NO 3 − almost had no effects on the photodegradation of CZ, this was probable due to the insufficient of NO 3 − or the competitive photoabsorption by the high concentration of NO 3 − [19].…”

Pesticide behavior in modified water-sediment systems

“…The most reactive species is ·OH attacking C-H bonds in a relatively nonselective manner at diffusion-controlled rates, and it most likely participates in the photodegradation of pesticide. The photoinduced homolytic cleavage of the N-O bond in NO 3 − and NO 2 − producing ·OH was confirmed by formation of nitro and nitroso derivatives in the photolysis of chlortoluron 51) and monolinuron. 52) CO 3 −· is more selective than ·OH toward electron-rich S-and N-containing chemicals, 53) and the negative correlation of 55) These results show that the two anions act as a radical source and that CDOM has the dual character of a radical scavenger and a photo-sensitizer ( Fig.…”

Investigation of photodegradation and hydrolysis of selected substituted urea and organophosphate pesticides in water

“…Nélieu et al (2004) studied the photodegradation of monolinuron and found out that addition of nitrates increase the photodegradation of the compound. Shankar et al (2008) and Nélieu et al (2009) also observed faster photodegradation rates of several phenylureas in the presence of nitrates. Regarding the other two pH values, only monolinuron was decreased by 10% and 15% at pH 7 and 9, respectively (Fig.…”