Abstract
Air particulate samples were collected from one urban and two rural sites in NW England. Regression of Br and Pb showed the elements to be virtually uniquely associated at all sites, but with a lower ratio of
Br
Pb
in the town (0.25 ± 0.01) than at the rural sites (0.30 ± 0.01 and 0.33 ± 0.02). All the
Br
Pb
ratios were below that assumed to characterize fresh exhaust (0.386) and it is suggested that this is due not only to loss of Br, but more substantially to the collection of either resuspended street dust or re-entrained exhaust deposit emissions. Evidence for this was found in size-fractionated samples, for which fine fraction
Br
Pb
ratios near 0.386 were measured, both at urban and rural sites. Further evidence came from studies of the lead speciation. In contrast, a second urban site, at Ellesmere Port, showed evidence for Br loss in measurements of gaseous and particulate Br, which may be attributed to a different atmospheric composition at this site.