Geophysical Assessment of Toxicological Effects of Agrochemical Runoff in Groundwater: A Case of Dikumari, Yobe State.

This study employs the technique of Vertical Electrical Sounding (VES) combined with physicochemical analysis to evaluate the toxicological effects of agrochemicals runoff in groundwater aquifer in Dikumari, an irrigated environment. Ten (10) VES measurements (D1 – D10) were recorded across the study area using Schlumberger electrode configuration. Each VES measurement covers 200 m of current electrode spacing, which implies an AB/2 of about 100 m. Five (5) groundwater samples collected from different tube wells across the study area were also analyzed using Atomic Absorption spectroscopy (AAS) to evaluate groundwater contamination and to draw correlation with aquifer contamination. The shallow aquifer layer revealed resistivity variation ranging from 7.5 Ωm in D6 to about 173 Ωm in D2 with thickness variation ranging from 6.9 m in D3 to about 11.0 m in D6. Low resistivity variation occurred mostly away from residential area, and on irrigated sitewhich accounted for contamination (high conductivity) due to application of agrochemicals on the irrigated sites. Arsenic, Lead, and Nitrate concentrations were <0.01 mg/L, <0.01 mg/L and <50 mg/L respectively. Contamination due to agrochemical runoff in Dikumari, at present does not constitute public health concern, but may expose people to health risk, if pesticides, made up of highly toxic chemical compounds, capable of contaminating aquifer system in and around the study area.