Aerosol lead levels were determined in the atmosphere of Rawalpindi, Pakistan, at eight sampling sites with low to high traffic density, using the standard high volume sampling and the modified dithizone scrubbing based techniques. Flame AAS method was employed to analyze aerosol particulates for Pb collected on glass fiber filters from a high volume sampler running on an 8-hourly basis. Nitric acid based digestion method was employed for the dissolution of particulate mater. In parallel, the dithizone-carbon tetrachloride scrubbing method was used to trap the particulate matter in solution at an inlet air flow rate of 1.5 LPM, at three pie-selected monitoring times: 8:00, 12:00 and 16:00 hrs. The Pb levels determined by the former technique ranged from 22 mg/m3 to 57 mg/m3 and by the latter from 18 mg/m3 to 39 mg/m1 on the same days. Meteorological parameters, such as temperature, wind speed, wind direction and relative humidity, were also recorded to evolve a probable correlation with the distribution and dispersion of Pb in the local atmosphere. The usefulness of the two techniques is herein highlighted for monitoring the metal levels in typical urban atmosphere. Data on airborne Pb distribution from other parts of the world are described and discussed.
MUNIR H SHAH ,M JAFFAR ,M SAQIB ,
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