Gbati Napo^{1, 2,}, Kossitse Venyo Akpataku^{1, 3}, Alfa-Sika Mande Seyf-Laye^{1, 3}, Masamaéya D. T. Gnazou¹, Limam Moctar Bawa¹, Gbandi Djaneye-Boundjou¹

The shallow Continental Terminal aquifer constitutes the primary water resource for drinking purpose in the coastal sedimentary basin of Togo, facing population growth, mining development, industrialization, and intensive agriculture. This study aims to assess groundwater quality and associated human health risks, to ensure the sustainable water supply in the basin. Major chemical parameters, and trace elements of forty-two samples of shallow groundwater and eight samples of surface water collected during march 2019 were analysed using AFNOR methods. The dataset obtained was used to evaluate drinking water quality and safety. The results showed that groundwater was slightly acid (4.83 < pH < 7.63, mean of 5,63) and fresh to brackish (82.4 < TDS < 6610 mg/L, mean of 652 mg/L). In contrast, surface water was circum-neutral (6.24 - 7.8, mean of 6,91), and fresh to very saline (134 < TDS < 33915 mg/L, mean of 9580 mg/L). For both groundwater and surface water, the cations and anions abundance order was respectively Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and Cl^- > SO₄^2- > HCO₃^-> NO₃^-. Thus, water samples were predominantly Na - Cl water type (~88 %). The water quality index score based on major ions indicated that 93% of the groundwater samples were classified as excellent and good for drinking. The non-carcinogenic risk ranged from 3.887 to 17.650 for children, from 2.272 to 10.135 for adult females, and from 1.785 to 8.104 for adult males and was related principally to manganese, nitrate, arsenic, fluoride and cadmium. The carcinogenic risk ranged from 0.004 to 0.006 for children, 0.003 to 0.004 for adult females, and from 0.002 to 0.003 for adult males and was caused by arsenic and cadmium. The water quality is affected by seawater intrusion, evaporite dissolution and anthropogenic contamination. The consumption of groundwater may cause health effect on human.

coastal sedimentary basin, groundwater, water quality index, human health risk assessment, trace elements, Togo