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Investigation of the relationship between aerosol and rainwater composition

Türküm, Ahmet
Chemical composition of particles and rain water at three sites in Turkey were extensively compared to determine if there is a relationship between aerosol and rain composition. If such relationship exists, it can allow one to construct rain water composition using aerosol data. This is important because, rain composition data is scarce as sampling and analysis of very low concentrations of elements and ions in rain water is more difficult compared to sampling and analysis of atmospheric aerosol. Results showed that aerosol composition can be closely reflected in composition of rain water if below cloud processes dominate over the incloud processes. This is clearly observed for crustal elements in all stations and for most of the elements in urban Ankara station. However, in rural stations there were differences in rain and aerosol that is attributed to significant contribution from in cloud processes. Seasonal patterns and enrichment factors observed in aerosol composition showed general agreement with corresponding temporal variations observed in rain water concentrations of elements, but short term variations became visible only if data is averaged over a long period of time. These observations suggest that certain features of rain water composition can be constructed from if concentration data is available for aerosols. However it should be noted that there are also significant differences between stations and between elements or element groups, indicating that composition of rain water constructed from aerosol data can only be a crude one. Similarities between rain and aerosol compositions is more pronounced in urban Ankara station compared to rural stations used in this study. Factor analysis performed to aerosol and rain water data sets showed that source types affecting chemical composition of rain and particles are generally the same, bur contribution of each