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+>
NO3– at 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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