Spatial and temporal variations in inhalable CuZnPb aerosols within the Mexico City pollution plume
Abstract
We report on the CuPbZn content of PM10 and PM2.5 samples collected from three sites (urban T0, suburban T1 and rural T2) during the Mexico City MILAGRO campaign of March 2006. Daytime city centre concentrations of ∑CuZnPb(PM10) were much higher (T0 > 450 ng m−3) than at the suburban site (T1 < 200 ng m−3). Rural site (T2) ∑CuZnPb(PM10) concentrations exceeded 50 ng m−3 when influenced by the megacity plume but dropped to 10 ng m−3 during clean northerly winds. Nocturnal metal concentrations more than doubled at T0, as pollutants became trapped in the nightly inversion layer, but decreased at the rural site. Transient spikes in concentrations of different metals, e.g. a “copper event” at T0 (CuPM10 281 ng m−3) and “zinc event” at T1 (ZnPM10 1481 ng m−3) on the night of March 7–8, demonstrate how industrial pollution sources produce localised chemical inhomogeneities in the city atmosphere. Most metal aerosols are <2.5 μm and