Assessment of Total Mercury Levels Emitted from ASGM into Soil and Groundwater in Chami Town, Mauritania

Abstract

Artisanal and small-scale gold mining (ASGM) is a serious growing concern in Sub-Saharan Africa. In Mauritania, recent gold discoveries in the north and northwest have led to an increase in ASGM centers, reflecting trends across the region and posing considerable risks of mercury (Hg) contamination. Notwithstanding this fact, the extent of mercury contamination in the region remains unclear due to insufficient knowledge on the mechanisms of Hg dispersion in hyper-arid regions. In light of this, the present study aimed to acquire fundamental knowledge to elucidate the dispersion mechanism of mercury through conducting soil and groundwater sampling in and around Chami town, Mauritania, where ASGM activities have intensified. We analyzed 180 soil samples and 5 groundwater samples for total mercury (total Hg) using cold vapor atomic absorption spectrometry (CVAAS) and atomic fluorescence spectrometry (AFS) methods. The total Hg levels in soil samples ranged from 0.002 to 9.3 ppm, with the highest concentrations found at ASGM sites. Groundwater samples exhibited low total Hg levels (0.25–1.25 ng/L). The total Hg content in soil and groundwater samples was below Japanese standards, yet soil samples from hotspot points exceeded other international standards. Our study emphasizes the Hg dispersion patterns around Chami town, suggesting a gradual decrease in total Hg with increasing distance from ASGM sites and a potential influence of wind dynamics. The knowledge accumulated in this study provides essential insights into the Hg dispersion mechanisms in Chami town, laying the foundation for establishing a predictive model of Hg contamination in hyper-arid regions.