Determining of risk areas due to exposure to heavy metals in the Toluca Valley using epiphytic mosses as a biomonitor.

The work aim is to identify the risk areas by exposure to Cr, Cu, Pb and Zn in the Metropolitan Zone of Toluca Valley (MZTV) using the mosses Fabriona cilaris and Leskea angustata as a biomonitors, geostatistical interpolation and multi-criteria evaluation by analytical hierarchy process. The results from the estimation of the enrichment factors (EF) showed that Pb is the heavy metal with the highest values, followed by the Zn, Cu and Cr. The EF obtained for all heavy metals show that there is a moderate to high anthropogenic enrichment. The above indicates that in the MZTV there are emission sources that contribute (significantly) in the amount of Cr, Cu, Pb and Zn accumulated in the biomonitor. Combustion processes, vehicle emissions, biomass burning, brick kiln emissions, agricultural and livestock activities, manufacturing industry and re-deposition by the action of the wind, were identified as the main heavy metals sources in the MZTV. Risk maps showed the high and medium risk areas are located in sites with poor urban vegetation coverage and close to highways and industrial parks. Low risk areas are located in sites with high urban vegetation coverage. The method used for identifying risk areas is a rapid and low-cost evaluation tool can allow local government environmental agencies to define public policies on air pollution control.