Chemical composition of rain water in Lebanon

Samples of rainfall water were collected from fifteen stations in Lebanon during the period between October 1999 and April 2000 (the rainy season in Lebanon). Nine of these stations are distributed along the urban coastal cities, from the north to the south. The remaining 6 stations, which have different altitudes ranging from 400m to 1200m high, are distributed in the mountainous rural areas. The concentrations of major cations (H+, Na+, Ca2+, Mg2+ and NH4+) and major anions ( Cl-, NO3-, HCO3- and SO42-) are determined for the first time in Lebanon. It has been found that the rain water is not acidic, due to the presence of carbonate dust particles in the atmosphere, which arise from the natural carbonate rocks, especially predominance in the mountains and internal regions of Lebanon. The high predominance of Na+ and Cl- in the coastal investigated stations, is attributed to marine aerosol spray. The concentrations of SO42- and NO3- are close to the concentrations expected in typical urban areas. The correlation between the concentration of chemical species confirms the influence of natural and anthropogenic sources