Enriched concentrations of bromine, chlorine, and iodine in urban rainfall as determined by instrumental neutron activation analysis

Concentrations of bromine, chlorine and iodine were determined in bulk rain as part of a detailed urban monitoring program. Instrumental neutron activation gives simultaneous nondestructive analysis of these halogens with detection limits of 2, 30 and 1 ng/g for bromine, chlorine, and iodine, respectively. Results for enrichment factor calculations based on crustal, seawater and lake water reference elements were somewhat contradictory. Elemental ratios of Br/Cl, I/Cl, Br/PB, and Cl/Pb, together with an analysis of chlorine in urban surface materials, support the suggestions that local anthropogenic sources may cause the high bromine and chlorine concentrations observed in urban precipitation while fractionation from an oceanic source is likely responsible for high iodine concentrations.