The increase in food needs due to high population growth in Niger has led to the intensification of urban agriculture and the increased use of pesticides. The objective of this study is primarily to assess the polar pesticide contamination (mainly herbi-cides) of the Niger River and its tributary, the Mekrou River, in Niger, using both grab sampling and POCIS (Polar Organic Chemical Integrative Samplers), and then to evaluate the risk to the aquatic environment. Two water sampling campaigns were carried out during the wet and dry seasons. The polar pesticides were analyzed by liquid chromatography coupled with tandem mass spectrometry, which allowed the identification of compounds with concentrations in the grab samples above the WHO guide values and the EU directive: diuron with 2221 ng/L (EU quality guideline: 200 ng/L), atrazine with 742 ng/L (EU quality guideline: 600 ng/L) and acetochlor with 238 ng/L (EU quality guideline: 100 ng/L). The risk assess-ment study indicated that diuron and atrazine present a high risk for the aquatic environment during the wet season. The main source of water contamination is the intensive use of pesticides in urban agriculture near the city of Niamey, and the intensive cotton farming in the Benin. Moreover, the surveys (30 producers interviewed) showed that 70% of the pesticides used are not approved by the Interstate Committee for Drought Control in the Sahel (CILSS) and some are prohibited in Niger. The inventory of pesticides sold in the zone showed that active ingredients used by producers are 48% insecticides, 45% herbicides, and 7% fungicides.

The Nigerien Liptako in southwest Niger has gold mineralisations in Birimian formations (Paleoproterozoic) that have been mined for several decades. The objective of this study was to document the concentrations of arsenic and other toxic trace elements in groundwaters, river waters, suspended particulate matter and sediments and discuss the potential influence of artisanal gold mining on arsenic and trace elements enrichment. For this, forty-three groundwater samples (boreholes and wells) were analysed in mined and unmined areas. Surface waters, suspended particulate matters and sediments were sampled in three rivers at stations upstream and downstream from mining sites. Rock samples extracted from mine galleries were collected for mineralogical and geochemical characterization. In groundwater, arsenic concentrations ranged from 0.018 to 202 µg/L, exceeding drinking water guidelines (10 µg/L) in three artisanal gold mining areas. Manganese exhibited concen-trations exceeding the potability limit in 23% of the samples, mainly in the Continental Terminal aquifer. In rivers, arsenic was the element most enriched in suspended particulate matter and sediments, but its concentration in water did not exceed 3 µg/L. Mineralogical analysis of rocks showed traces of arsenic in association with iron oxides, suggesting a release of arse-nic in groundwater by desorption. The consumption of these waters rich in arsenic or manganese presents serious risks for health. These data represent the first large-scale investigation of arsenic and trace elements concentrations in groundwaters and surface waters in the Nigerien Liptako, where no or very scarce water quality measurements have been published yet.

The increase in food needs due to high population growth in Niger has led to the intensification of urban agriculture and increased use of pesticides. The objective of this study is to assess the polar pesticide contamination of the Niger River and its tributary, the Mekrou River, in Niger, using both grab sampling and POCIS (Polar Organic Chemical Integrative Samplers) and evaluate their ecological risks in the waters. Two water sampling campaigns were carried out during the rainy and dry seasons. The samples were analyzed by liquid chromatography coupled with mass spectrometry (HPLC/MS) and allowed the detection of compounds with concentrations above the WHO guide values and the EU directive: diuron with 3281 ng/L (EU quality guideline: 200 ng/L), atrazine with 1476 ng/L (EU quality guideline: 600 ng/L) and acetochlor with 255 ng/L (EU quality guideline: 100 ng/L). Diuron and Atrazine show a high ecological risk for aquatique environment. The main source of this water contamination is the intensive use of pesticides in urban agriculture near the city of Niamey and in an intensive cotton farming in the Benin. The results of surveys showed the influence of poor pesticide application practices and seventy percent (70%) of the pesticides used are not approved by the Interstate Committee for Drought Control in the Sahel (CILSS) and some are prohibited in Niger. These contaminations may raise concerns about the health of farmers along the Niger River and the Mekrou River.