Total gaseous mercury levels in the vicinity of the Central Mexico mountain mining zone and its dispersion area

Mercury emitted to the atmosphere has a long residence time (up to a year) and can travel long distances before being deposited to land or ocean surfaces. The objective of this study were to evaluate the total gaseous mercury (TGM) ambient levels in the San Joaquín, Querétaro, mining region and to observe whether the TGM emissions from mining activity impact other regions of the country due to its dispersion. TGM was measured using an automatic Tekran model 2537A air mercury analyzer; the monitoring was carried out during March, April, and May 2015. From the ambient measurements carried out, the 8-h average concentrations range from 67 to 74 ng/m 3 , while the monthly averages for these three months were from 40 to 41 ng/m 3 (1.3 ± 0.4 ng/m −3 ). Mercury concentrations did not vary significantly during the 24-h survey measurement, reporting an average value of 40.3 ± 0.75 ng/m 3 (40.1 ng/m 3 averages) and an extreme value of 235 ng/m 3 . In order to identify the possible TGM fate, a set of trajectories was obtained for different time periods using the wind fields from the Water Research and Forecasting (WRF) meteorological model and a dispersion was performed by using the CALPUFF model driven by the WRF-CALMET model to identify the TGM levels in the site vicinity.