Biomonitoring and Sourcing Toxic Elements Using Vascular Epiphytes of the Tillandsia Genus in the Mining Region of Taxco de Alarcón, Guerrero, Southern Mexico

The concentration of As, Pb, Cd, Zn, Fe, Mn, and Cu and the Sr and Pb isotopic compositions were determined in four species of the vascular epiphyte Tillandsia (T. caput medusae, T. ionantha, T. recurvata, and T. sp), to evaluate their capacity to biomonitor the air quality and the sources of lithogenic particles and toxic elements in a severely contaminated site from the mining region of Taxco de Alarcón, Guerrero (southern Mexico). With the exception of Cu, mean concentrations are typically higher in the contaminated site relative to a reference (uncontaminated) site, and the incrustation of metal-bearing particles (mainly PM₁₀ and PM_2.5) on leaves and roots seems to be the most significant mechanism of incorporation of these pollutants to plants. The Sr isotopic composition indicated that surrounding lithology is the main source of lithogenic particles, whereas statistical tools and Pb isotope ratios revealed a genetic link of toxic elements in epiphytes with Taxco ores and mining wastes, which confirm the capacity of the evaluated epiphytes to record local environmental conditions. The presence of abundant metal-bearing particles, particularly in the PM_2.5, may represent a serious threat to the health of wild fauna, livestock, and humans in the zone. The study demonstrated that vascular epiphytes of the Tillandsia genus could be used as an efficient, low-cost, biotechnological tool for monitoring the air quality in severely contaminated polymetallic sites such as mining and smelting zones, as well as for sourcing lithogenic and metal-bearing particles.