Monitoring lead in suspended air particulate matter in Ho Chi Minh City

Airborne lead has been measured in Ho Chi Minh City in the framework of an environmental monitoring programme since late 1992. Air particulate matter was collected atop an eight-storey building in working hours in a near-downtown residential area. The average concentrations of lead and total suspended particulate matter (TSP) for the 1993–1994 period were (179 ± 12) and (90 ± 6) μg m−3, respectively. Autoexhaust is believed to be a major source of lead; however, refuse burning and firecracker discharges may also contribute to some extent. Lead, while decreasing in rainy season, exhibited a rather irregular seasonal pattern resulting in a poor anticorrelation with rainfall in contrast with TSP. Lead values from 60 to 240 ng m−3 covering over 60% of measured data fit very well with a lognormal distribution mode which reflects the lognormality of wind speed with almost the same atmospheric stability condition. The deviations from this main distribution mode of lead concentrations outside this range are interpreted as due to the changes in atmospheric stability conditions that occurred during seasonal transition periods as well as under prolonged cyclonic and anticyclonic conditions.