The Relationship Between Sulphur Dioxide and Sulphate in the Cairo Atmosphere

Alia A. Shakour1 and Ashraf S. Zakey2

1 National Research Center, Giza, Egypt
2 Egyptian Meteorological Authority. Dokki, Cairo, Egypt
 
Corresponding author: Alia A. Shakour
Air Pollution Department,
National Research Center. Dokki, Giza, Egypt
Phone: (+20) 2-337-1362
FAX: (+20) 2-337-0931
e-mail: ma@idsc.gov.eg (for the second author)

CEJOEM 1998, Vol.4. No.1.:82-90


Key words:
Air quality, monitoring, photochemical reaction 

Abstract: Sulphur dioxide gas and sulphate particles were evaluated in the atmosphere of a residential site at the eastern sector of Cairo city. Sulphur dioxide concentrations were measured hourly from July 1993 to December 1995, while sulphate concentrations were determined daily for one year (July 1993 to August 1994). The maximum monthly concentration of SO2 was 262 mg/m3 while the maximum annual concentration was 94 mg/m3 which exceeded much the Egyptian and WHO air quality standard. Hourly SO2 concentration shows that the maximum value of SO2 at 9 a.m. is associated with high traffic emissions which is a major source of SO2 in this residential area. The annual mean concentration of sulphate is 36 mg/m3 which is approximately nine times greater than the USA air quality. The maximum value of sulphate was recorded during winter season, this indicated that high relative humidity enhanced the conversion of sulphur dioxide to sulphate. This oxidation process of sulphate is called droplet phase reaction. 

Received: 11 August 1997
Accepted: 12 February 1998 
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Posted: 15 November 1998