Levels, composition and source apportionment of rural background PM10 in western Mexico (state of Colima)

The variability of levels and composition of PM10 were investigated (October 2006 to May 2007) in a semi-rural classified site located in the central region of the state of Colima (Western Mexico), away from the direct influence of pollution sources. Mean PM10 levels reached relatively high values (48 mu g/m(3)), due mainly to enhanced loads of crustal material (15 mu g/m(3)), carbonaceous aerosols (10 mu g/m(3)) and sulfate (9 mu g/m(3)). Dust resuspension, volcanic, industrial, agricultural, farming, and road traffic emissions, as well as regional pollution were identified as the main drivers of this variability. Furthermore, meteorological factors at local, regional and synoptic scales influenced such PM10 variability. A differentiation was found between the cold period, with average PM10 levels reaching 42 mu g/m(3), and the warm period, with 56 mu g/m(3). The first study period was characterized by high levels of SO4-2 (19 mu g/m(3)) arising from both anthropogenic and volcanic emissions, whereas the second one is characterized by a high contribution from crustal material (22 mu g/m(3)) from soil resuspension and volcanic ash. Principal component analysis (PCA) showed that the highest contribution to PM10 levels arises from the regional pollution (49%), followed by the industrial emissions, fuel oil combustion, road traffic and secondary sulfate (18, 17, 10 and 6%, respectively). This shows a large anthropogenic load in rural background PM pollution, consequently, we propose to build an air quality monitoring network in rural and urban areas of this region. (C) Author(s) 2011. This work is distributed under the Creative Commons Attribution 3.0 License.