Research Projects

A three-week dry deposition measurement field program in the South Coast Air Basin of California is described, the objectives of which were to quantify the deposition velocities, and their associated uncertainties, for sulfur dioxide, sulfate aerosol, nitrogen oxides, and nitric acid. The measurements took place in May and June, 1986, on a flat, grass-covered surface near Carson, California. Deposition velocities were estimated by the profile method, based on gas concentration gradient measurements and associated wind and temperature data acquired on a 5 meter tower, using a sampling frequently of 1 Hz. The estimated nighttime sulfur dioxide deposition velocity was 2.6 cm/s, exceeding the daytime value of -2.1 cm/s. The nitrogen oxides deposition velocities were estimated to be very close to zero, regardless of time of day. The estimated nitric acid deposition velocities were slightly negative (indicating no deposition). Insufficient data were obtained to estimate sulfate aerosol deposition velocities. The estimated deposition velocity measurement uncertainties ranged from 0.1 cm/s to 3.3 cm/s.