| Popis: |
During 1968-1971, 8763 samples were collected at 59 sites in US cities for a study of particulate lead concentrations in air. Each site was sampled continuously for a full year. These samples have been analyzed for total suspended particulate matter and for cadmium, chromium, lead, manganese, nickel, and zinc. Results of over 42,000 analyses are summarized in convenient graphical form, showing geometric means, geometric standard deviations, maxima, and minima. Supplementary tables present these data and cumulative frequency distributions. This historical data base should be a useful reference to determine effects of changes in fuel consumption patterns and trends. It presents a uniquely extensive cross-sectional picture of trace metal concentrations determined by a single highly experienced laboratory. Results were compared with available recent data for 17 identical sites. Recent lead concentrations averaged 35% of the older values, and some reductions occurred in concentrations of other metals. |
