Chemical Signatures Related to Atmospheric Impact on Groundwater: Initial Analysis for Central Benin, West Africa

Groundwater samples collected from wells penetrating the crystalline rock of central Benin were characterized using ICP-MS and ICP-OES. The resulting element analyses demonstrate several strong relationships indicative of different forcing functions on the groundwater geochemistry. Among the signatures that can be inferred from these analytical results are: -1-Indication of impact from Saharan dust with an apparent increase in the importance of this source with increasing latitude. Among the indicator elements were Ti, Si, and Sc. -2-Indication of impact from a source related to ocean water with a decline in the strength of this signature with increasing latitude. Among the indicator elements were Na and Sr. -3-Indication of possible impact from anthropogenic sources including isolated contamination in individual wells and regional signatures apparently of atmospheric origin. -4-Indication of local impact of mineralogy as evidenced by deviation from the regional trends within at least one small subregion of wells. These results indicate that the chemical characteristics of groundwater in central Benin may provide valuable insight into the impacts of atmospheric sources on the chemistry of groundwater. Analysis of these chemical characteristics may also provide an important tool for estimating the relative importance of different precipitation patterns on the recharge in this region of western Africa.