Chemistry of rain water in Riyadh, Saudi Arabia

Twenty-three rain water samples were collected from 15 sampling locations in Riyadh during four rain events in 1994 and analyzed for pH, conductivity, TDS, alkalinity, Cl, NO3, F, SO4, Na, Mg, Ca, and 12 trace metals. The pH ranged between 6.83 and 8.21. The major cation and anion were Ca and SO4, contributing with 30.5% and 20.8%, respectively, to TDS. Moderate variation in major ions concentration was found to occur between different sites. The concentrations of different metals varied considerably from one sampling location to another. The dominant trace metal ions in the rain water samples were Zn, Pb, and Al. Samples collected from a site near a cement factory in Riyadh showed maximum concentrations of most of the major ions and metals. The concentrations of various ions in the first rain event were comparatively higher than the concentrations of these ions in the later rain events.