Geostatistical and Food Risk Assessment of Soils Contaminated by Trace Elements in the City of Dschang (Cameroon)

Spatial distribution of trace elements (TEs) in soils of the city of Dschang (Cameroon) was studied to identify their origin (geogenic vs. anthropogenic). The topsoil (at different depths) of 71 sites was analyzed using the rapid portable X-ray fluorescence analysis method. Soils from locations associated with metal-related activities exhibited the highest levels of contamination (average concentrations in mg kg−1: As, 8.2; Cr, 213.7; Cu, 201.8; Pb, 97.4; Zn, 838.0), followed by household waste dumps and agricultural plots (levels close to those of cultivated low-lying areas). The observed decrease in TE concentrations with depth (notably for Zn) supports the hypothesis of a human origin (compared with soil-geochemical background of control sites). Geostatistical approach indicated an underestimation of health risks associated with the consumption of crops from several sites. Specifically, 87.32%, 49.30%, and 47.89% of the sites exceeded the Food Crops Reference Value (FCRV) for Cr, Zn, and Cu, respectively. Additionally, the number of contaminated sites for each TE varies depending on the method: Cu > Zn > Pb > Cr > As = Ni > Cd and Cr > Zn > Cu > Ni > Pb > As > Cd with the geostatistical and FCRV approach respectively. From the first step of the soil chemical quality investigation, our study highlights the need to use methods based on health risks, especially for sensitive uses of soils such as food production.