The cultivation of strawberries generally requires substantial use of pesticides, and abamectin is the active principle of one of those most commonly employed. Conventional water treatment does not remove pesticides efficiently, so there is a need to investigate alternative procedures. The use of advanced oxidation processes (AOPs) can achieve good results in removal of toxic organic compounds present in aqueous solutions. The photo-Fenton process, one example of an AOP, was employed to study the degradation of abamectin. Results showed that when natural water samples contaminated with abamectin were treated using the photo-Fenton process, 70% of the initial amount of the compound was removed within 60 minutes of UV irradiation, and 60% mineralization was observed after 180 minutes of reaction. 1. Introduction Biocides are one of the most important classes of compounds introduced into surface waters by human activities [1]. They are widely used in agriculture and can contaminate rivers and other water bodies due to transport from cultivated areas [2–5]. Although the pesticide industry has developed new compounds that are more effective, even at lower concentrations, and that present lower environmental impacts [6], the misuse of such pesticides can pose considerable toxicity risks to operators, consumers, and the wider environment [7]. The cultivation of strawberries uses large amounts of pesticides. One of the most commonly employed is Vertimec 18 EC, which contains 1.8% (w/v) of abamectin, the active principle. Abamectin belongs to the avermectin group and has the molecular formula C48H72O14 (avermectin B1a) + C47H70O14 (avermectin B1b). It is used primarily as a biocide. Abamectin is a toxic chemical and can be fatal if inhaled, ingested, or absorbed by the skin. It causes skin and eye irritation, and at high doses can cause damage to the central nervous system (CAS no., 71751-41-2). The substance is also highly toxic to fish and aquatic invertebrates. The maximum acceptable daily intake (ADI) is 0.01？mg？kg？1 body weight, and the maximum residue limit is 0.02？mg？kg？1 of the commercial product [8]. Effluents containing biocides cannot usually be treated efficiently using biological techniques, since the effluents are toxic to the microorganisms involved so that the biodegradation efficiency is reduced [9]. An alternative treatment that has been investigated is based on the use of advanced oxidation processes (AOPs), which are very efficient for the removal of potentially toxic organic compounds from water systems. In AOPs, hydroxyl radicals are formed
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