Journal of Global Ecology and Environment

Former agricultural soils may retain trace metals after cultivation has ceased, particularly where chemical fertilisers were previously applied. This study assessed selected soil-quality indicators and residual lead (Pb) and arsenic (As) at three former agricultural sites and one control site at the University of Man, Côte d’Ivoire. Each site was subdivided into three square plots. Two composite samples were collected from each of the three plots at each site along the vertical profile, from two soil horizons: [0–20 cm] and [20–40 cm]. More specifically, on each square plot, five (5) soil cores, one in the center and four at the corners of the plot, were collected using an auger driven vertically to the desired depth to form a composite sample. Thus, for the three former agricultural sites and the control site, 120 soil cores were collected, for a total of 24 composite samples distributed across the two depth levels. Organic matter was estimated based on organic carbon, and Pb and As concentrations were determined by inductively coupled plasma optical emission spectrometry following acid digestion. Contamination and ecological risk were evaluated using the geo-accumulation index and the single-metal ecological risk index. Soil pH ranged from 4.06 to 5.30, indicating acidic conditions, while organic matter content ranged from 10% to 17%. Arsenic concentrations ranged from 0.06 to 0.39 mg/kg, and lead concentrations ranged from 0.04 to 0.30 mg/kg. Concentrations were generally higher at the former agricultural sites than at the control site and tended to decrease with depth. Geo-accumulation index values were negative at all sites, while ecological risk values ranged from 0.38 to 1.89 for As and from 0.01 to 0.08 for Pb, remaining below the low-risk threshold. These findings indicate low contamination and ecological risk for the two assessed metals under the indices and reference values applied.