Black carbon in PM2.5, data from two urban sites in Guadalajara, Mexico during 2008

The BC and PM2.5 concentrations in Guadalajara, Mexico were measured in 2008 using a two–wavelength Aethalometer and a Partisol sampler, respectively. The aerosols were collected within two sites of the local Network Monitoring Stations, Centro in downtown and Miravalle in the south. BC was measured from January to December and PM2.5 from January to August. The 24–h PM2.5 mean concentrations were 73 and 90 µg m‐3 at Centro and Miravalle, respectively. Mexican air quality 24–h standard (65 µg m–3) was exceeded by 79% of the PM2.5 samples. The BC study period was divided into three seasons: two dry seasons (DS1 and DS2) and one rainy season (RS). The hourly BC median concentrations at Centro and Miravalle were 1.3–8.7 and 1.5–13.8 µg m‐3 in DS1 while 1.4–3.3 and 1.9–6.4 µg m–3 in RS, and 1.4–7.0 µg m‐3 in DS2. When the 24–h mean BC concentration is compared to the mass concentration of PM2.5, it shows that BC comprises less than 10% of the fine particles measured at the same period. Considering the meteorological parameters wind speed and wind direction, data analysis indicates that the BC concentration is mainly influenced by local sources at Centro, but by regional and/or long–range transport and local sources at Miravalle site. The strong correlation between BC and carbon monoxide concentrations confirmed that these two species at the two sites have common sources.