Characterization and mobility of mining tailings in the area with the highest artisanal mercury production in Mexico

Abstract

At the 1960 and 1970, cinnabar (HgS) was extracted in Mexico to obtain elemental mercury (Hg⁰). In most cases, these tailings or mining wastes (known as jales^[1] in Mexico) were disposed to open-sky and contaminated areas nearby places of exploitation. This paper presents the characterization of the physicochemical properties of two samples of mining waste with concentrations of mercury above the values established by the Mexican regulations (310 mg/kg), in order to estimate the mobility of the metal. Samples were located and gathered from the municipality of Pinal de Amoles, Querétaro, Mexico (West 99º 26' to 99° 43' and North 20° 58' to 21° 21'). Values were characterized measuring its pH values, hydraulic conductivity, organic matter content, total density, total mercury concentrations, and chemical species. Also, two leachates were generated through extractive tests for potentially toxic compounds (PECT, by its Spanish acronym) and for metals and metalloids (PEMyM, by its Spanish acronym). Results obtained were the following: Total mercury determined 374.72 and 333.43 mg/kg, the PECT results 108.29 and 111.68 mg/kg, the resulting PEMyM have values between 30.52 and 21.30 mg/kg for samples of “La Lorena” and “San Jose”, respectively, representing a high mobility from solid to liquid phase.

[1] Jales: Palaba derivada del náhuatl xalli, partículas muy pequeñas (arenas finas, según Cabrera, 2002) / A Nahuatl derived word, xalli, meaning very small particles (very fine sand, according to Cabrera, 2002)