Comparison between dry deposition fluxes measured with water and solid surfaces, and estimated by an inferential model

The quantification of the dry atmospheric input to natural surfaces is curr ently a complet task. In this study a water surface sampler (DAS) was used contemporary to conventional solid surface samplers (wet&dry and bulk) to m onitor the dry deposition in a densely inhabitated and industrialised area. The dry contribution to the total deposition was 33-56% for sulfate, 11-39 % for ammonium and 18-28% for nitrate ion, depending on the measurement tec hnique. Among the three samplers, the DAS one was the most efficient to col lect sulfate, ammonium and nitrate. The comparison of the seasonal trends s howed that the dry collector using a polyethylene surface, collected mainly aerosol particles of ammonium sulfate, while the aqueous surface of DAS sa mpler was able to sample also the gaseous form of the pollutants. Sulfate a nd nitrate nux values determined from direct measurements were also compare d with those obtained by a resistance model. The sulphate measured values f itted quite well with those predicted from the model showing similar season al variations. The quantitative differences observed in winter could be due to an increase in the acidity of water, used as collecting medium, which l owered the solubility of gaseous sulphur dioxide. In order to investigate t he effect of water, used as collecting medium, which lowered the solubility of gaseous sulphur dioxide. In order to investigate the effect of water ac idity on the deposition on a water body, a series of experiments were carri ed out.