Emissions of Lead to the Environment

The single most important anthropogenic source of Pb to the global atmosphere remains vehicle emissions this source alone exceeds the natural fluxes [87] by a factor of approximately 30 times. Other important sources of atmospheric Pb are non-ferrous metallurgy and fossil fuel combustion from stationary sources (mainly coal-burning) (Table 1). Comparing the 1995 data with 1983 data 

Source Anthropogenic emissions for 1995 ftom Ref. [85], and natural emissions ftom Ref. [86]. 

Atmospheric Lead from Alkyllead Fuel Additives 

The chemistry of organolead compounds in the environment has been reviewed elsewhere [93-96], but a few salient aspects are summarized here. First, tetra-alkyllead compounds are volatile Henry s Law constant of 4.7 x 10 and 6.9 X 10 (Pam )/mol for tetramethyl and tetraethyllead, respectively, according to Wang et al. [97]. However, only a small fraction of the Pb leaving an automobile as exhaust is in this form, e.g., typically 0.1-10% [95]. In addition to the relatively low emission factor from leaded gasoline combustion, tetra-alkyllead compounds are rapidly decomposed by homogeneous gas phase reactions such as photolysis, reaction with ozone, triplet atomic oxygen, or hydroxyl radical [98,99] with half-lives of less than 10 h in summer and 40 h in 

An elegant demonstration of the temporal changes in environmental fluxes of alkyllead concentrations is the study of trimethyl Pb in Chateauneuf-du-Pape wines none was found in wine samples pre-dating the introduction of leaded gasoline, and peak concentrations were found in wine dating from 1978 since then, concentrations have declined markedly [103]. 

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