SEASONAL-VARIATION OF THE IONIC ALKYLLEAD SPECIES COMPOSITION OF RAINWATER

A comprehensive long-term survey of the concentration levels of ionic alkyllead species in rainwater at a residential location was carried out, relying on a funnel-in-bottle sampler and a well-assessed analytical procedure based on extraction, derivatization, and gas chromatography-atomic absorption spectrometry (GC-AAS). During the 1.5-year monitoring program (1986-1987), the total dissolved ionic alkyllead content of the samples never exceeded 230 ng L-1 Pb and averaged 45 ng L-1 Pb. The relative concentrations of the four major species PbMe3+, PbMe2(2+), PbEt3+, and PbEt2(2+) corresponded roughly to 4:1:2:2; the mixed methylethyllead species contributed only marginally. From the measurements, the local annual wet deposition of ionic alkyllead could be estimated at approximately 32-mu-g m-2 year-1 Pb. Interestingly, a seasonal variation characterized by lower concentrations in summer, which probably reflect a higher photochemical degradation rate in the atmosphere, was observed; the ethyllead species most clearly underwent this fluctuation. The results are discussed within the framework of previous studies, at this and other locations, of organolead in wet atmospheric deposition.