Mobility and speciation of mercury in soils from a mining zone in Villa Hidalgo, SLP, Mexico: A preliminary risk assessment
2020
Quintanilla-Villanueva, G.E. | Villanueva-Rodríguez, M. | Guzmán-Mar, J.L. | Torres-Gaytan, D.E. | Hernández-Ramírez, A. | Orozco-Rivera, G. | Hinojosa-Reyes, L.
The mineralized district La Tapona in Villa Hidalgo SLP was widely known as a mercury producer at the end of the XIX century. Although primary production was stopped since 1994 in Mexico, the presence of mercury and the artisanal and small-scale mercury mining represents a risk to the local population living in the surrounding. Thus, the study aimed to determine the impact of Hg on the inhabitants of Villa Hidalgo, SLP, Mexico. Soil and groundwater samples were collected from seven localities in the autumn of 2016. In these communities, water is used for human activities, such as irrigation, housework, and human consumption. Total Hg was determined in local waters and soils; furthermore, Hg fractionation and Hg speciation (methyl mercury) were investigated in soils. The results were correlated to physicochemical parameters as well as mineralogy and main geochemistry. The total mercury (THg) content in water was lower than the threshold value at all the monitoring sites, whereas the THg content in the soil samples ranged from 0.34 to 41.76 mg kg⁻¹, which exceeded the national regulations for a single site. In soil, the residual mercury was the main Hg fraction, and methylmercury was not detected. The most critical factors that affect soil fraction distribution and low Hg mobility in the studied area were the low organic carbon content, and high concentrations of iron, aluminum, and calcium. These results could indicate the association of mercury with sulfides and crystalline oxides of iron and manganese. Although low Hg mobility was detected, the children's population was more sensitive to the non-carcinogenic risk caused by Hg as corroborated with the results of the hazard indexes (HI: 0.11 – 3.90) being the soil ingestion the main route of exposure.
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