GEOCHEMICAL AND MINERALOGICAL CHARACTERIZATION OF URBAN DUST FROM A SONORAN DESERT CITY, NW MÉXICO: ANTHROPOGENIC IMPRINT

Hermosillo city, located in NW Mexico, is a rapidly growing border city within the Sonoran desert. The climate is characterized by high temperatures and low but heavy annual rainfall, concentrated in a few hours in the year during the summer months (North American monsoon). The combination of the heavy short period rains with low vegetation cover and considerable percent of unpaved roads in city could increase the potential erosion in the region. Previous studies report high metal- and pesticide-concentrations in urban dusts from Hermosillo. Additionally, the city does not have a storm sewer system; therefore, the city is flooded in every monsoonal rainfall, until evaporation takes place. The combination of all these anthropogenic components may have a negative effect on the re-suspended urban dust. This could be a potential cause for the stomach illnesses and acute respiratory infections. It is important to remark the importance of mineralogical and geochemical characterization of urban dust, in order to start the understanding of potential sources, process, and possible human risk in arid regions. In this work, bulk metal content of soils around the city, road dust, Total Suspended Particles (TSP), and PM10 filters where analyzed. Also, other sources are considered as possible contributors in the region (i.e. cement plants, wollastonite mine, and marble rock quarries around the urban area). Mineralogical analyzes with X-ray diffraction and scanning electron microscopy on dust from the filters and roads were also carried out. Finally, the statistical treatment method used was multivariate analysis of principal component analysis (PCA). Multivariate analysis of geochemical data of dust differentiates traffic sources and cement industry products from the natural background in the area. TSP geochemistry seems to be strongly influenced by the cement industry in the area, whereas PM10 seems to be related to other sources (wollastonite mine and marble quarries). The mineralogy points out an important geogenic input on the dust, principally, quartz, plagioclase, calcite and clays. However some non-common minerals have been detected. Like some barites and copper and even Cr rich particulate have been found in the PM the SEM. An important traffic and cement imprint signature has been detected in Hermosillo dust.