Spatial distribution, mobility and potential health risks of arsenic and lead concentrations in semiarid fine top-soils of Durango City, Mexico

Abstract

Significant amounts of mining wastes containing Fe-oxide rich phases (i.e., hard rock dumps, tailing impoundments) have been historically deposited in semiarid soils within Durango City. Urban mapping along with mineralogical and geostatistical analyses were carried out to determine levels of concentration, spatial distribution, and relationships between As-bearing and Pb-bearing phases and their mobilities for different sites around this city. It was found that fine As-bearing particles (<5–10 μm) comprised of Pb3(AsO4)2-like, FeAsS, and complex structures were the main phases in urban sprawl soil, while PbO2-like, PbS, and (Ba, Pb)SO4-like were the main Pb-bearing phases (<5 μm). Levels of As and Pb vary in urban sprawl soil from 4.37 to 42 and 8.3 to 82.5 mg kg−1, respectively, and are higher in the soil adjacent to Cerro de Mercado, where the mining area is conurbated, from 55.1 to 221 and 21.6 to 107.3 mg kg−1, respectively. Most of these concentrations were associated with the finest soil fraction (<10–250 μm), enhancing health risks due to inhalation or incidental intake. The spatial distribution patterns of these elements were mainly related to high traffic density and mining waste for Pb, and eolic dispersion of fine soil particles for As. A low mobility was found for Pb (up to 3%), indicating a low environmental risk if released, whereas As mobility changes from a low to a medium risk level (0.1–37.1%). Geostatistical analysis suggested correlations between soil pollution and distance regarding hard rock and tailing impoundment sources.