Modelling and measurements of below cloud scavenging processes in the highly industrialised region of Cubatão-Brazil

Below cloud scavenging has been investigated from rainwater chemistry measurements using a one-dimensional scavenging numerical model and surface data from the local atmospheric conditions. The local emissions of pollutants from a large industrial complex in the south-eastern Brazil were also evaluated in the modelling. The scavenging model was coupled to the measurements of SO2−4, NO−3 and NH+4 found in the rainwater samples. The concentration of gases and particles samplings and meteorological parameters measured during the study of rain episodes were used as input data in the numerical model, which simulates the raindrop interactions associated with the removal process. The results were compared with those actually measured. The variability of the rainwater concentrations estimated through the scavenging model was also compared to the chemical analysis of the rainwater collected by fractionated rain samplers. The results show a good agreement between both modelled and observed data as seen from the role of the raindrop size distribution in the below cloud scavenging of pollutants