The Contributions of Open Sources to Ambient TSP Levels

A companion paper showed that the annual (1976) emissions of particles from open sources, those sources too great in extent to control through enclosure or ducting, in the U.S. were over 500 × 10⁶ tons. Here it is demonstrated that on the average, a single open source class (unpaved roads) contributes 1.2 times as much to the variability of statewide-averaged measured annual mean TSP levels as all conventional sources. The nine other major open source classes do not appear to contribute significantly to measured TSP levels, due to patterns of source and monitor location. Although, on the average, the total contributions of unpaved roads to TSP are larger than conventional source contributions, the per ton contributions are only approximately one-ninth as great. Both precipitation frequency and adjacent states’ TSP levels are found to be stronger determinants of the between-state variability in TSP levels than conventional open source emissions. Several states, including NM, IL, AL, NJ, PA, CA, ID, ND, Rl, DE, CT, and WV (depending upon criterion of importance) are identified for further research on the feasibility, practicality, importance, and cost-effectiveness of control of emissions of dust from unpaved roads.