*Corresponding author email: goudaibrachi@yahoo.fr Symbiosis Group Symbiosis Group Symbiosis www.symbiosisonlinepublishing.com ISSN Number: 2572-3162 The Transfer of Insecticides Used in Cotton Production to Aquatic Ecosystems in the Cotton Basin in Northern Benin AI GOUDA 1, 2* , I. IMOROU TOKO 1 , M IMOROU IDRISSOU 1 , P SPANOGHE 5 , ML SCIPPO 3 , Z SIDI 1 , T DJAGBE 1 , P KESTEMONT 4 & B SCHIFFERS 2 1 Laboratoire de Recherche en Aquaculture et Ecotoxicologie Aquatique (LaRAEAq), Département des Sciences et Techniques de Productions Animale et Halieutique (STPAH), Faculté d’Agronomie (FA), Université de Parakou (UP), Bénin. 2 Gembloux Agro-Bio Tech/Université de Liège (ULiège), Laboratoire de Phytopharmacie, Belgique 3 Laboratoire d’Analyse des Denrées Alimentaires, FARAH-Santé Publique Vétérinaire, Faculté de Médecine Vétérinaire/Université de Liège (ULiège), Belgique 4 Unité de Recherche en Biologie Environnementale et Evolutive (URBE), Faculté des Sciences, Université de Namur, Belgique. 5 Crop Protection Chemistry, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University Abstract The transfer of two insecticides (acetamiprid and chlorpyrifos) from cotton fields to a nearby water reservoir together with the ecotoxicological risks involved for this receiving environment were assessed by measuring their concentrations in runoff water and sediment samples collected both at the exit of the crop plots and in the reservoir after treatment. The multi-residue method by UPLC-MS/MS was used to determine the concentration of the different active substances in the collected samples. The results obtained indicate that acetamiprid and chlorpyrifos are almost always present regardless of the treatment period. The physico-chemical properties (solubility in water and adsorption to soil particles) explain a difference in behaviour between acetamiprid, present mainly in water, and chlorpyrifos, more concentrated in sediments. Calculations show that 0.005% of the acetamiprid applied in the basin around Gambanè flows to the reservoir, compared to 0.0003% of the chlorpyrifos applied. Depending on the sampling dates, the average runoff quantities for acetamiprid vary from 0.002 to 0.156 g/ha over 96 g/ha and from 0.001 to 0.039 g/ha for chlorpyrifos. The study shows that the transfer by runoff from the fields is relatively fast but is nevertheless influenced by rainfall, the distance of the fields to the reservoir, the slope and the characteristics of the environment. At the concentrations of acetamiprid observed in this receiving environment, the ecotoxicological risk would be negligible (Environmental Risk Index = 4) for aquatic organisms, earthworms and birds. However, concentrations of chlorpyrifos in the environment could be harmful to these organisms (Environmental Risk Index = 272). The aquatic ecosystem in this area is therefore exposed to the harmful effects of these active substances. Key words: acetamiprid; chlorpyrifos; UPLC-MS/MS; cotton Received: September 24, 2019; Accepted: October 16, 2019; Published: 14 November, 2019 *Corresponding author: Abdoul-Ibrachi GOUDA Gembloux Agro-Bio Tech/Université de Liège (ULiège), Laboratoire de Phytopharmacie, Belgium ; Email: goudaibrachi@yahoo.fr International Journal of Scientific Research in Environmental Science and Toxicology Open Access Research Article Introduction In Benin, the cotton sector accounts for about 80% of exports and 35% of tax revenues [18, 26, 48, 59]. To improve yields and control pests, the cotton sector alone consumes nearly 90% of the insecticide market and 96% of chemical fertilizers sold in the country [33, 60]. However, the use of plant protection products in the control of cotton pests and weeds has consequences for the health of farmers and consumers, as well as for the environment [53]. The vast majority of these chemicals, overused during successive agricultural campaigns, end up polluting the environment by various mechanisms including air drift, direct leaching into the soil or runoff at their surface under the effect of rainfall. Previous research in Benin has shown that local dispersion of plant protection products by wind during treatment depends, in addition to weather conditions, on the type of spraying equipment used (backpack sprayer or centrifugal cane) and the spraying height [29]. The leaching of active substances in soils has also been extensively documented as well as their transfer by runoff into aquatic ecosystems, which would depend on several factors including climate, crop type, soil condition and agricultural practices [13, 14, 15, 31, 39]. In all cases, the surrounding aquatic ecosystems (both surface and underground) are generally the final recipients of these active substances or their sometimes more toxic derivatives with sometimes harmful effects on indigenous organisms present or benefiting from the resources of these ecosystems[5,16,28,29,50]. Thus, in the water reservoirs that constitute the receiving aquatic ecosystems in the Beninese cotton basin, organisms could be permanently exposed to these pesticide residues. Some of these residues, may persist