Concentrations of heavy metals and measurement of 40K in mine tailings in Zacatecas, Mexico

The aim of this study was to identify wild plant species with potential for remediation of As and Pb and to measure the 40K activity on soil mine tailings in Sombrerete, Zacatecas (North Central Mexico). The analysis of As and Pb was performed by atomic absorption spectrometry, while the concentration of 40K was carried out by low-resolution gamma-ray spectrometry. Plants growing on two mine tailings show ability to accumulate or tolerate heavy metals. Major family represented in the area was Asteraceae. Arsenic showed the highest concentrations, in soils, of 2004 and 1101 mg/kg, respectively, while Pb at 132 and 113 mg/kg, respectively. These results evidence that the tailings are highly contaminated and represent a potential risk for population and the environment. Wild plants that showed maximum values of As in their shoots were Asphodelus fistulosus (447 mg/kg), Pennisetum villosum (342 mg/kg) and Purshia mexicana (268 mg/kg). Presence of P. mexicana shrub is reported for the first time as accumulator of As in semi-arid region of Mexico. The concentration of 40K in soil samples from the mine tailings reported for the first time is in agreement with the mean values reported for the world. The wild plant species identified could be used for re-vegetation and stabilization of the mining wastes and contribute to decrease As bioavailability in arid and semi-arid regions.