AN INVESTIGATION OF THE DOMINANT SOURCE REGIONS OF FINE SULFUR IN THE WESTERN UNITED-STATES AND THEIR AREAS OF INFLUENCE

Two methods for analyzing source-receptor relationships are used to determine the dominant source regions of particulate sulfur in the western U.S. The first method, area of influence analysis is based on the residence time of back trajectory endpoints. The other method, principal component analysis, involves examination of the gradients of the spatial eigenvectors of fine sulfur concentrations to determine source regions. Results of both methods are similar and show that southern California, northeastern Mexico, and the large coal-fired power plants in the Four Corners region contribute most strongly to the long-range transport of fine sulfur into remote areas of the western U.S. Several sources with smaller areas of influence are also identified.