Abstract

HERNANDEZ-SILVA, Gilberto et al. Presence of total mercury in the soil-plant-atmosphere relationship in southern area of Sierra Gorda, Querétaro, México. TIP [online]. 2012, vol.15, n.1, pp.05-15. ISSN 1405-888X.

More than two thousand years of historical exploitation dominate the native ore area in San Joaquin, Querétaro. Azogues and Ranas-San Joaquín (>300 mg kg^-1), as well as Calabacillas-Santa Rita and La Lana (30.1-300 mg kg^-1) were identified as the most contaminated soil areas with Hg contents above the permissible limits by NOM and WHO. Soils provide maize plant (Zea mays) with a significant amount of total mercury through translocation mechanisms (0.2-8.7 mg kg^-1 in roots and 0.2-8.2 mg kg^-1 in stem and leaf); in grain, the mercury amount is between 0.04 to 0.87 mg kg^-1 (0.5 mg k^-1g is the maximum concentration allowed). In the insoluble fraction of rain water, the average was 67.47 μ L^-1, and 36.49 μ L^-1 in the soluble fraction. The daily average of Hg vapor was 67 ng m^-3 during 38 days of analysis, with a range of 40 to 100 ng m^-3 showing a high difference on mercury volatilization. Soils, sediments and cinnabar tailings are the sources providing Hg to the plant maize through translocation mechanisms and through particulate material that is carried to the atmosphere by the wind and forward redistributed. The Hg vapor concentrations were above the permissible threshold. This behavior of variables involved in this study shows that San Joaquín's human population is exposed to a Hg concentration that is variable and above the permissible limits, which might pose a high risk for human health and the environment.

Keywords : Rainwater; maize plant; mercury; Mexico; Sierra Gorda; Hg vapor.

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