Seasonal and Spatial Variability of PM2.5 Concentration, and Associated Metal(loid) Content in the Toluca Valley, Mexico

Abstract

The Toluca Valley Metropolitan Area (TVMA) is the fth largest urban center in Mexico, located at high altitude, 2660 meters above sea level (m.a.s.l.) surrounded by mountain ranges. It is composed of heterogenous residential and industrial areas with dense vehicular tra c. This combination of geography and urbanization create a metropolitan area with high levels of air pollutants. The objective of this study was to provide evidence of the seasonal and spatial variation of metal(lloid)s in particulate matter minor to 2.5 microns (PM 2.5) in Toluca Valley. Four sites were sampled between 2013-2014, that include urban and industrial areas, in the dry-cold (November-February) and hot-dry (March-May) season; PM 2.5 were collected using high and medium volume samplers. Metal and metalloids concentrations in PM 2.5 were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Our results show the highest 24-hour PM 2.5 concentration in the northern area, followed by the southern industrial area, and the lowest concentrations was observed in the southwest area independent of the season. Metals and metalloids with a recovery percentage above 80% were Cobalt (Co), Chrome (Cr), Copper (Cu), Manganese (Mn), and Antimony (Sb). The maximum concentrations of them were observed during the dry-cold season, in the urban-industrial sites found in the north and southern areas. Co, Cr, Cu, Mn, and Sb concentrations were up to one hundred or thousand folded in the dry-cold season compared to dry-hot season due to weather and geographical features of TVMA. The 24-hour PM 2.5 and metal(lloid)s concentrations exceed national and international guidelines to protect population health.