Urban summer rain

We have employed two multi-elemental techniques (INAA and ICP-AES) to determine sulphur, halogens and 14 other trace elements in urban summer rainfall. Quality control was assured using NBS reference materials. The overall accuracy and precision of these two methods makes possible the routine analysis of many environmentally important trace elements in acid rain related investigations. Enrichment factor calculations showed that several elements including S, Cu, Zn and Cr were abnormally enriched in the urban atmosphere. A comparison of three separate sites showed a strong gradient of metal deposition from the industrial to the outlaying areas. 

Atmospheric lead can be removed by two natural processes precipitation and dry deposition. Removal rates by precipitation are a function of such factors as air concentration and the intensity of rainfall. In the remote terrestrial ecosystem discussed above, the rate of transfer from the atmosphere was 5 g Pb/ha-yr as winter snow and 4 g Pb/ha-yr as summer rain. These values appear to be typical of remote areas and are much lower than values reviewed by Nriagu (13) for urban areas, where precipitation inputs reach 100-300 g Pb/ha-yr. 

---