Rainwater Chemistry at Urban and Suburban Areas in Greater Cairo

Mamdouh Ibraheim Khoder and A. A. Abdel Hameed

Department of Air Pollution Research, National Research Centre, Dokki, Giza, Egypt

Corresponding author: Mamdouh I. Khoder
    Department of Air Pollution Research,
    National Research Centre, Dokki, Giza, Egypt
    Telephone: +202 3371433/2905
    Fax number: +202 3370931
    E-mail: khoder_55@yahoo.com

CEJOEM 2007, Vol.13. No.2.: 141–158


Key words:
Rainwater; chemical composition; pH; urban and suburban areas; ion balance; ions; neutralization factors


Abstract:
Rainwater samples were collected from urban (El-Maadi, Cairo) and suburban (Kafr Tohormos, Giza) areas in greater Cairo during the winter season (2003–2004), and were analyzed for major cations (Ca2+, K+, Mg2+, Na+ and NH4+) and anions (SO42–, NO3, Cl and HCO3). The average concentrations of these ions in rainwater were found to follow the pattern Ca2+> SO42–> Mg2+> Cl> Na+> NH4+> K+> NO3> HCO3 at the urban area, and Ca2+> SO42–> Mg2+> Cl> Na+> NH4+> HCO3> K+> NO3at the suburban area. The concentrations of Ca2+, SO42–, Mg2+, Cl, Na+, K+ and NO3 at the urban area were significantly higher than those found at the suburban area. The ratios of different components with respect to sea water ratio, enrichment factors and sea salt fractions indicated that nearly all the Ca2+, SO42– and K+ and fractions of Mg2+ and Cl were of non-marine origin at both sites. The average values of pH were 6.94 at the urban area and 7.41 at the suburban area. Rainwater acidity at urban and suburban areas in greater Cairo appeared to decrease due to high loading of dust particles in the atmosphere, which are rich in alkaline species. The relationships between the acid ions NO3 and SO42– and the cations NH4+, Ca2+ and Mg2+, and also between the various anion and cation combinations indicated that the acidity of precipitation is neutralized. Neutralization factors revealed that Ca2+ is the most dominant neutralization substance in both the urban and the suburban areas in greater Cairo atmosphere.


Received: 5 July 2007
Accepted: 25 October 2007

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