Propranolol degradation through processes based on the generation of hydroxyl free radical.

Pharmaceutical substances such as propranolol (PRO) are an emerging class of aquatic contaminants that have increasingly been detected in ground and surface water. For this reason, the aim of this study was to evaluate the efficiency of advanced oxidation systems for the PRO degradation. The tests started with anodic oxidation (AO), using 0.01, 0.05, and 0.1 M Na2SO4 as the supporting electrolyte and 16, 32, 48, and 64 mA cm-2 as current density. Under the best conditions obtained in AO, the electro-Fenton (EF) process was reviewed, where the effect of Fe2+ was analyzed with 5, 10, 15, and 20 mg Fe2+ L-1. The Fenton reaction (FR) was studied using the Fe2+ concentration that promoted the highest percentage of PRO removal and initial concentration of 16 mg L-1 of H2O2, in addition to these conditions, in the photo-Fenton (PF) system, the effect of UV light with wavelengths 254 and 365 nm were evaluated. The results obtained showed that the degradation efficiency of the EF > AO > PF > FR system along with a percent removal of 94.52, 90.4, 25.97, and 4.4%, respectively. The results showed that PRO can be removed through the studied systems, with the EF system being the most efficient.

Comparative ecological risks of pesticides used in plantation production of papaya: application of the SYNOPS indicator.

Pesticides are used intensively for crop protection in tropical fruit plantations. Assessments of the relative risks posed by pesticides are needed to assist in the development of management plans that minimize ecological impacts. In this study, the risk indicator SYNOPS_2 was used to compare risks to aquatic ecosystems by pesticides commonly used in papaya plantations. Plant interception and spray drift were measured during six applications of three pesticides (chlorothalonil, chloropyrifos, and malathion) using a turbo fan driven sprayer. Plant interception was estimated to be higher (42.6+/-12.7%; p=0.04) in late (8-14 months old) than in early (4 months old) trees (20.1+/-25.3%). Chlorothalonil concentrations of up to 11.0 microg L(-1) were found in water from an adjacent ditch after field application. Concentrations of this pesticide (7.4+/-4.1 microg L(-1)) in runoff water were also significantly (p<0.01) higher than those of malathion (2.4+/-1.9 microg L(-1)) and chlorpyrifos (0.8+/-0.5 microg L(-1)). Good correlation between measured and predicted values (r2=0.56-0.85, p<0.01) showed that SYNOPS_2 is able to describe trends in runoff pollution in papaya plantations. Linear equations were obtained in order to correct numerical disagreement between measured and calculated runoff concentrations. An independent test showed a reasonable agreement between measured chlorothalonil concentrations and the predicted values using the proposed equations. Fifteen pesticides used in papaya cultivation were ranked according to their calculated chronic biological risk index. Pesticides with the highest risk index for non-target organisms were: chlorothalonil for algae, lambda cyahalotrin for Daphnia and fish, and malathion for earthworms. Chlorothalonil was the pesticide with the highest exposure level in water and therefore represents a high risk for aquatic life. Results show that SYNOPS_2 can be used as a pesticide risk indicator on papaya and possibly other tropical fruit plantations.