Trace elements in atmospheric precipitation at Northern Jordan measured by ICP-MS: acidity and possible sources

Rainwater samples were collected in a rural region in Northern Jordan using 24-h sampling periods from December 1998 to April 2000. All samples were analyzed for major ions (Na+, K+, Ca2+, H+, Mg2+, NH4+, Cl−, NO3− and SO42−) and trace metals (Pb, Cd, Zn, Cu, Al, Fe, Mn, Mo, Ni, Sb and V). The majority of the rain samples collected had pH values higher than 5.6. The average pH was 6.4±0.9. High values of pH were attributed to the neutralization by natural alkaline local dusts which contain large fractions of calcite. The annual average SO42−-to-NO3− ratio is 1.8, which is close to that observed in more polluted regions. Concentrations of measured species were lower than those reported for other rural sites worldwide. Elements of anthropogenic origins (Zn, Pb, As, Sb, Ag and Cd) were highly enriched with respect to crustal composition. Factor analysis permitted the identification of four source groups, namely crustal dust, sea-salt spray, road traffic and combustion and secondary aerosol formation processes.