Chemical characteristics of rain water at an urban site of south western Turkey

Abstract

In this study, chemical composition of the rain water in Mugla was investigated from February to April 2002. Rain water samples were obtained from Mugla, a small city in south western Turkey. The Yatagan Power Plant is located 30 km northwest of Mugla city. The values of pH and the concentrations of major ions (Ca2+, Na+, K+, SO42-, NO3-, NH4+) in the rainwater samples were analyzed. The pH varied from 4.5 to 7.7 with an average of 6.9 which was in alkaline range considering 5.6 as the neutral pH of cloudwater with atmospheric CO2 equilibrium. In the total 30 rain events, only two events were observed in acidic range (< 5.6) which occurred after continuous rains. The equivalent concentration of components followed the order: Ca2+ > SO42- > NH4+ > NO3- > Na+ > K+ > H+. The volume-weighted mean (VWM) of the measured ionic sum is 371.62 mu eq/ l. The ratio of between sum cations and sum anions (Sigma cations/Sigma anions) is 1.52 mu eq/l. The alkaline components (Ca2+, Na+, K+) contribute 52%, NH+ 4 8%, whereas, the contribution from the acidic components is relatively small (40%). The low concentrations of H+ found in rainwater samples from Mugla suggest that an important portion of H2SO4 and HNO3 have been neutralized by alkaline particles in the atmosphere. The dust- rich local and surrounding limestone environment might have caused the high concentration of Ca2+ in Mugla area. The relatively high concentration of NH+ 4 observed at Mugla is suspected to be due to surrounding agricultural. The results obtained in this study are compared with those other studies conducted at various places in the world.