The Chemical Composition of Winter Fogs at São Paulo Highway Sites

Radiation and advection fogs were characterized at two sites nearby important roads next to São Paulo City, Brazil. Water-soluble ions, monosaccharides, other sugars and organic and elemental carbon (OC and EC) were determined. Both sites present a high number of fog events with mainly radiation fogs causing visibility problems to the automotive traffic (Castello Branco and Raposo Tavares roads). Samples were collected in nine events in 2009 and ten events in 2010, during wintertime. Two radiation and advection fog events have been herein presented. The radiation fog occurred in 2009 at Castello Branco Road (CBR), presented the highest concentration of pollutants comparing to all other events. The most abundant species are associated with biomass landfill and fossil fuel burning. Locally, the region has a strong impact by the fertilizer industries and traffic of heavy vehicles. The second most polluted event occurred also in 2009 at CBR, an advection fog presented species attributed to soil resuspension and anthropogenic emissions. The results are compared with rainwater composition studies.