Atrazine, an herbicide used to control grassy and broadleaf weed, has become an essential part of agricultural crop protection tools. It is widely sprayed on corn, sorghum and sugar cane, with the attendant problems of its residues in agri-food and washing water. If ingested into humans, this residual atrazine can cause reproductive harm, developmental toxicity and carcinogenicity. It is therefore important to find clean and economical degradation processes for atrazine. In recent years, many physical, chemical and biological methods have been proposed to remove atrazine from the aquatic environment. This review introduces the research works of atrazine degradation in aqueous solutions by method classification. These methods are then compared by their advantages, disadvantages, and different degradation pathways of atrazine. Moreover, the existing toxicological experimental data for atrazine and its metabolites are summarized. Finally, the review concludes with directions for future research and major challenges to be addressed.

High resolution mass spectrometry (HRMS) was coupled with ultra-high-performance liquid chromatography (uHPLC) to monitor atrazine (ATZ) degradation process of Fenton/ultrasound (US) treatment in real time. Samples were automatically taken through a peristaltic pump, and then analysed by HPLC-HRMS. The injection in the mass spectrometer was performed every 4 min for 2 h. ATZ and its degradation metabolites were sampled and identified. Online Fenton experiments in different equivalents of Fenton reagents, online US experiments with/without Fe²⁺ and offline Fenton experiments were conducted. Higher equivalents of Fenton reagents promoted the degradation rate of ATZ and the generation of the late-products such as Ammeline (AM). Besides, adding Fe²⁺ accelerated ATZ degradation in US treatment. In offline Fenton, the degradation rate of ATZ was higher than that of online Fenton, suggesting the offline samples were still reacting in the vial. The online analysis precisely controls the effect of reagents over time through automatic sampling and rapid detection, which greatly improves the measurement accuracy. The experimental set up proposed here both prevents the degradation of potentially unstable metabolites and provides a good way to track each metabolite.

Atrazine, the most commonly used herbicide, has been reported to pollute the water environment and do harm to human health. It is thus urgent to find an efficient way to degrade atrazine. Although various advanced oxidation processes including high voltage electrical discharge (HVED) have been applied to degrade atrazine, the formation kinetics of its metabolites are still incomplete, and the detoxification of the degradation process remains to be clarified. Here, the degradation of atrazine by HVED was investigated, in comparison with traditional Fenton oxidation and ultrasound treatment. Nineteen metabolites of atrazine degradation were identified and quantified by high performance liquid chromatography coupled with high resolution mass spectrometry (HPLC-HRMS) techniques. Results show that HVED is more advantageous because of its high degradation rate for atrazine (89%), short processing time (1000 s, corresponding to 10 ms effective time), and the presence of the less toxic main metabolite hydroxyatrazine. Hydroxyl radicals (˙OH) play an important role in atrazine degradation. Adding ferrous ions (Fe²⁺) during HVED and ultrasound processes is beneficial for the degradation of atrazine, because of the ˙OH radicals released from hydrogen peroxide (H₂O₂). Based on the formation kinetics of atrazine degradation metabolites, detailed mechanisms of atrazine degradation pathways were proposed.

Although atrazine has been banned, residues of the compound and its metabolites are still detected in certain areas of French groundwater. In response to the European Green Deal, this study focuses on the degradation of atrazine in tap water and the toxicological evolution of different treatments. The degradation efficiency of atrazine in deionized water by high-voltage electrical discharge (HVED) and high-frequency ultrasound (HFUS) was higher than that in tap water with the same initial atrazine concentration, likely due to competition from impurities in tap water, such as ions and other organic compounds. Additionally, acute toxicity testing using Daphnia magna was conducted to assess the toxicological impact of the degradation processes. Acute toxicity (LC50) values were used to evaluate the toxicity of the different treatment solutions initially containing atrazine. High-resolution mass spectrometry coupled with liquid chromatography (LC-HRMS) was employed to identify and compare the transformation products generated by each degradation technique. Furthermore, an in-silico toxicity evaluation using the QSAR model was proposed and compared to the experimental data. The in-vivo assessment revealed that atrazine solutions treated with Fenton oxidation (LC50 < 0.1 mg/L) were significantly more toxic than those treated with HFUS (LC50 > 5 mg/L) or HVED (1.5 < LC50 < 2.5 mg/L). However, in the in-silico evaluation, Fenton oxidation appeared less toxic, as residual toxicity from ferrous ions and hydrogen peroxide was not considered. Consequently, the degradation of atrazine by HVED and HFUS proved to be more efficient and environmentally favorable.