Investigating relationships between aerosol and rainwater compositions at different locations in Turkey Ahmet Türküm, Hakan Pekey ⁎, Beyhan Pekey 1 , Gürdal Tuncel Department of Environmental Engineering, Middle East Technical University, Ankara 06531, Turkey article info abstract Chemical compositions of atmospheric aerosol and rainwater samples collected at four different locations in Turkey were compared to investigate the relationship between aerosol and rainwater compositions. Results showed that aerosol composition could be reflected closely in rainwater composition if below-cloud processes dominate in-cloud processes. This was clearly observed for crustal elements at all stations and for most elements at the urban station. However, at rural stations there were differences in rain and aerosol that were attributed to significant contributions from in-cloud processes. Seasonal patterns observed in aerosol composition showed general agreement with the corresponding temporal variations observed in concentrations of elements in rainwater. These observations suggest that certain features of rainwater composition can be constructed if concentration data are available for aerosol. However, differences in the data observed at the different stations and among various elements or element groups showed that the composition of rainwater constructed from aerosol data can be only a crude effort. Similarities between rain and aerosol compositions were more pronounced at the urban station as compared to the rural stations. Scavenging ratios calculated using paired daily data were variable both among stations and within a single station. Long-term averaged data were found to be more reliable in calculating scavenging ratios of elements and ions at all stations. © 2008 Elsevier B.V. All rights reserved. Keywords: Aerosol Rainwater Temporal variations Scavenging ratio 1. Introduction Precipitation plays an important role in identifying fluxes for many elements and species at atmosphere–ecosystem inter- faces (Galloway et al., 1982; Slinn, 1983). However, field studies show that concentrations in wet depositions are highly variable, which makes it difficult to quantify fluxes without long-term campaigns (Al-Momani et al., 1998; Tuncer et al., 2001). Most elements found in rainwater come from the aerosol and gas phase, either incorporated directly in the clouds (in-cloud scavenging) or washed out by the precipitation (below-cloud scavenging). A better understanding of the rainfall phenomena therefore can be achieved only by studying the relationship between aerosol and rainwater media (Jaffrezo and Colin, 1988). Atmospheric aerosol and rainwater both provide media to understand the state of air pollution at a receptor and potential impacts on ecosystems. Mass and chemical compo- sition of atmospheric particles has been extensively used to understand the (a) health effects of associated particles and the pollutants, (b) mechanisms of transport from source to receptor, and (c) reasons for visibility degradation (Samura et al., 2003; Hauck et al., 2004). However, chemical composi- tion of rainwater is being used to understand the transport of pollutants, acidity, persistent organic compounds, and pre- sence of heavy metals from the atmosphere to terrestrial and marine ecosystems and to assess the effect of such transport on the degradation of various ecosystem components (Thalmann et al., 2002; Deboudt et al., 2004). Atmospheric Research 89 (2008) 315–323 ⁎ Corresponding author. Present address: Department of Environmental Protection, Kocaeli University, Kocaeli 41275 Turkey. Tel.: +90 262 351 3482; fax: +90 262 351 3629. E-mail address: hpekey@gmail.com (H. Pekey). 1 Present Address: Department of Environmental Engineering, Kocaeli University, Kocaeli 41380, Turkey. 0169-8095/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.atmosres.2008.03.010 Contents lists available at ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmos