The chemical composition of rainwater over Büyükçekmece Lake, Istanbul

In the present study, the precipitation near Büyükçekmece Lake, which is one of the important drinking water sources of Istanbul city, was studied during October 2001–July 2002. Seventy-nine bulk precipitation samples were collected at two sampling stations near the Lake (41°2′35″N, 28°35′25″E and 41°5′30″N, 28°37′7″E). The study comprised the determination of H+, Cl−, NO3−, SO42−, NH4+, Na, K, Mg, Ca, Al, Ba, Fe, Cu and Mn concentrations in bulk deposition rain event samples. The average volume-weighted pH value was found to be 4.81, which points out that the rain is slightly acidic. High sulfate concentrations were observed together with high H+ ion values. Sulfur emissions were the major cause for the observed high hydrogen ion levels. On the basis of factor analysis and correlation matrix analysis, it has been found that in this region, acid neutralization is brought about by calcium rather than the ammonium ion. The varimax rotated factor analysis grouped the variables into four factors, which are crustal, marine and two anthropogenic sources.