Assessment of groundwater contamination by pesticide residues in market garden sites, department of Madaoua-Niger

In the Department of Madaoua-Niger, the intensification of market gardening and the uncontrolled use of unregistered pesticides in the majority of cases are sources of pollution of water resources that are also used for human consumption, animal watering and household needs. The objective of this study is to quantify pesticide residues in water from market garden in order to show their level of contamination by its residues and the health risks associated with its consumption. Fifteen (15) water samples from market garden drilling were taken at the end of the 2019 dry season and analyzed by the QuEChERS method. Seventeen pesticide residues belonging to five chemical families, namely organochlorines, organophosphates, pyrethroids, carbamates and dinitroanillins were quantified at concentrations ranging from 0.02 to 0.5 µg/l. The results show that the waters of these market garden sites are contaminated by aldrin (0.1-0.3 µg/l), heptachlor (0.05-0.5 µg/l), glyphosate (0.17-0.5 µg/l), deltamethrin (0.12-0.35 µg/l), cypermethrin (0.2-0.46 µg/l), and lambda-cyhalothrin (0.11-0.34 µg/l). Their concentrations increase from 1.10 to 16.66 times their WHO and EU MRLs in all samples. In addition, the concentrations of DDT, α-endosulfan, β-endosulfan, chlorpyrifos methyl, pendimethalin and carbofuran exceed their EU drinking water MRLs by 1 to 5 times in all samples. The sum of the concentrations of all quantified pesticide residues ranges from 2.427 to 3.675 µg / l and is 4.73 to 7.95 times higher than the WHO and EU potability standard of 0.5 µg / l for the total concentrations of active ingredients determined in a water sample. Some pesticides such as DDT, aldrin, dieldrin, endosulfan, and lindane are even banned according to Annex III of the Rotterdam Convention for health or environmental reasons. The search for pesticide residues has revealed the pollution of water from the market garden sites studied.