Elevational patterns of sulfur deposition at a site in the Catskill Mountains, New York

In this paper we report measurements of SO42- - fluxes in throughfall and b ulk deposition across an elevational transect from 800 to 1275 m on Slide M ountain in the Catskill Mountains of southeastern New York State. The net t hroughfall flux of SO42- (throughfall-bulk deposition), which we attribute to cloud and dry deposition, increased by roughly a factor of 13 across thi s elevational range. Part of the observed increase results from the year-ro und exposure of evergreen foliage at the high-elevation sites, compared to the lack of foliage in the dormant season in the deciduous canopies at low elevations. Comparison of the net throughfall flux with estimates of cloud deposition suggests that both cloud deposition and dry deposition increased with elevation. Dry deposition estimates from a nearby monitoring site fal l within the measured range of net throughfall flux for SO42-. The between- site variation in net throughfall flux was very high at the high-elevation sites, and less so at the lower sites, suggesting that studies of atmospher ic deposition at high-elevations will be complicated by extreme spatial var iability in deposition rates. Studies of atmospheric deposition in mountain ous areas of the eastern U.S. have often emphasized cloud water deposition, but these results suggest that elevational increases in dry deposition may also be important. (C) 1999 Elsevier Science Ltd. All rights reserved.