RESUMO
Chlorinated organic compounds are important contributors to the anthropogenic enhancement of stratospheric ozone depletion. We report measurements of stratospheric isotope fractionation in such a compound. Stratospheric and tropospheric difluorodichloromethane (CF2Cl2) were found to have the largest relative 37Cl/35Cl isotope ratio difference ever measured for a natural compound. The increase of the relative isotope ratio difference with altitude was tightly correlated to the corresponding decrease in the CF2Cl2 mixing ratio. The observed relationship has a high potential to provide new insights into atmospheric chemistry and transport processes.
RESUMO
A method has been developed for estimating crudely the quantity of lead in dusts derived from paint flakes. This involves an assessment of the paint mass in the dust: gravimetrically in the coarse fractions, and by microscopic measurement in the fine fractions. Some street and house dust samples were examined. The street dusts contained up to 20% of lead from paint, and the house dusts up to 15%. However, it was the least lead-polluted dusts that contained the highest proportions of lead from paint. In the samples examined the paint flakes contained only low to moderate amounts of lead (0.07-4.21% w/w) and in the case of high lead paints the contribution from this source could be considerably greater.
