Dry deposition to snow in an urban area

Wet and dry deposition were measured in Warren MI during the 1983-1984 winter. Dry deposition was measured to a snow surface in a cutoff bucket and from the increase in snow core concentrations with time. The deposition velocity was calculated from the ratio of the dry flux to the ambient concentration. The dry deposition velocities calculated to a snow surface were 0.082 cm/s for SO/sub 2/, 2.0 for HNO/sub 3/, 0.083 for NH/sub 4//sup +/, 2.0 for CA/sup + +/ and 4.3 for C1. The values were not significantly different for a snow/water surface during melting compared to a snow surface. However, higher values of 0.69 cm/s for SO/sub 2/, 6.2 for HNO/sub 3/, 0.33 for NH/sub 4//sup +/, and 4.2 for Ca/sup + +/ were found to a deionized water suface in the spring. The higher values could be due to the higher air temperature and a change from a solid to a liquid surface or to greater atmospheric mixing during this period. The relative importance of wet and dry deposition was examined during the snow cover period of December 18 to March 14. Dry deposition was very important accounting for 42-80% of the total flux of the majormore » ions. This was due both to the low precipitation volumes in the winter and the influence of local sources on dry deposition. Dry deposition increased the importance of sulfate relative to nitrate in the snowpack.« less