The Influence of Meteorology and Atmospheric Transport Patterns on the Sulfate Levels in Raiwater in Orizaba Valley, Veracruz, Mexico

Abstract

This work assessed the relationship between synoptic circulation patterns, meteorological conditions and sulfate levels in rainwater in Orizaba Valley, Veracruz, Mexico during 2015. Samples were collected by using an automatic deposition sampler considering three climatic periods: Cold fronts or Nortes, Dry and Rainy seasons. Sulfate in rainwater was determined by turbidimetry (NMX-AA-SCFI-074-1981). A backward trajectory model (HYSPLIT) was used to characterize the potential source regions and transport pathways for air parcels arriving to Orizaba Valley; trajectories extended five days during 2015 were calculated. Mean concentrations of sulfate were 105.33, 37.5, and 52.5 μEq·l -1 , for Cold Fronts, Dry and Rainy seasons, respectively. An evident dilution pattern was observed with lower concentration levels when rainfall increased. Mean values for sulfate concentration exceeded the background hemispheric value reported by Galloway <i>et al.</i> (1982) for remote sites (10 μEq·l -1 ), exceeding almost 10, 3.7 and 5.2 times, during the Nortes, Rainy and Dry seasons, respectively. From the obtained results, it was concluded that the high sulfate levels in the rainwater measured in Orizaba Valley had their origin in different upwind regional sources as a result of long-range transport during Rainy and Nortes seasons.