Abstract
This study systematically investigated the oxidative treatment of five selected pesticides, alachlor (ALA), carbendazim (CAR), diuron (DIU), pyrimethanil (PYR), and tebuconazole (TEB), by comparing their relative reactivities as a function of three different oxidative treatment processes (i.e., chlorine (HOCl), ozone (O3), and ozone/hydrogen peroxide (O3/H2O2)) under various oxidant dosages, reaction times, and pH conditions. For oxidative treatment, pesticide standards were spiked into rainwater. The removal efficiency of the selected pesticides varied considerably depending on the oxidative treatment processes. HOCl, O3, and O3/H2O2 treatments were highly effective at eliminating CAR (>80%) and PYR (>99%), while they were not significantly effective in removing TEB (<20%). In the case of DIU, HOCl (81%) was shown to be more effective than O3 (24%) and O3/H2O2 (49%). The removal efficiency of ALA was in the order of O3/H2O2 (49%) > O3 (20%) > HOCl (8.5%). The effect of increasing the solution pH from 5.0 to 9.0 on pesticide degradation varied between the oxidative treatment processes. Additionally, NH4+, NO2−, and humic acid in rainwater significantly inhibited pesticide degradation.
Highlights
Pesticides are commonly used to enhance crop production and prevent plant diseases, such as fungal infections [1]
The primary outcomes were as follows:DOC is a major rainwater component and has a more significant influence on t
The dosage of oxidants for the removal of 90% CAR was in the order of HOCl (18 μM) > O3 (21 μM) > O3/H2O2 (25 μM), and the dosage of oxidants for removal of 90% PYR was in the order of O3/H2O2 (9 μM) > O3 (11 μM) > HOCl (20 μM);
Summary
Pesticides are commonly used to enhance crop production and prevent plant diseases, such as fungal infections [1]. The United States Environmental Protection Agency reported that the global application of pesticides totaled more than 2 million tons and over USD 39 billion in 2007 [2]. Most pesticide contamination occurs due to pesticide use in agricultural fields, the use of pesticides in urban areas has gained further attention owing to their potential risk to the environment and human health (e.g., mutagenicity, toxicity, and carcinogenicity) [3]. Several studies have demonstrated the presence of pesticides in urban rainwater globally [4,5]. Alachlor (ALA) and diuron (DIU) were detected in rainwater samples in Strasbourg, France, with maximum concentrations of 5590 and 1025 ng/L, respectively [4]. Tebuconazole (TEB) was detected in Brunswick Land (Germany) in concentrations ranging between 12 and 187 ng/L [5] (Supplementary information, Table S1)
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