MASS-BALANCE FOR LEAD IN THE CALIFORNIA-SOUTH-COAST-AIR-BASIN - AN UPDATE

A mass balance for lead for the year 1989 in the South Coast Air Basin has inputs to the atmosphere of 600 +/- 190 kg/day and outputs of 580 +/- 160 kg/day, showing rough agreement. Stationary sources are respo nsible for only about 5% of the total lead emissions. The bulk of the lead is emitted from vehicles using leaded gasoline (37%) and unleaded gasoline (15%), as well as from resuspension of previously deposited lead on roads (43%). Over half of the total emitted lead deposits on r oads and nearby soil, while about one-third is carried out of the basi n by wind. A small amount, less than 10%, is deposited on surfaces thr oughout the basin. These percentages are approximately the same as tho se in a mass balance for the same region calculated for 1972, when lea d emissions from leaded gasoline were about a factor of 70 greater tha n leaded gas emissions in 1989. When the lead emissions are used as in puts to a simple continuously stirred flow reactor model for the basin , reasonable agreement is obtained between calculated and measured con centrations. (C) 1998 Academic Press.