Rate of precipitation scavenging of nitrates on central Long Island

Abstract

By comparing deposition of nitrate in successive hours of precipitation samples taken over a six year period at Brookhaven National Laboratory (BNL), Long Island, New York, we have estimated scavenging coefficients in air, λ, for nitrate under a variety of meteorological and seasonal conditions. The square root transformation of the scavenging coefficients λ½ yields an approximately normal distribution; the mean value is 1.1 × 10−4 s−1, in general agreement with previous experimental and theoretical estimates. An interesting property of the distribution of the scavenging coefficients is that the ratio of the mean value of λ½ to its standard deviation varies little from 2.4 for various subsets of data; this property may limit the choice of stochastic models which describe the scavenging process. A trend analysis of the relationship between scavenging coefficients and rainfall rate indicates that the scavenging coefficient of nitrate does not increase for rainfall rates ≤3.2 mm h−1. The indicated increase at greater rainfall rates is qualitatively similar to model predictions but is based upon a small number of data points. The mean scavenging coefficient for winter rain events is greater than for snow.

Ultrafine particle scavenging coefficients calculated from 6 years field measurements

“…However, usually they are not. Our approach to the problem is somewhat similar to that presented by Sperber and Hameed (1986). If Eq.…”

Fate of ammonia in the atmosphere?a review for applicability to hazardous releases

“…The most extensive studies, Sperber and Hameed [33] and Shimshock and de Pena [29], fail to find a link between measured scavenging coefficients and the precipitation intensity. Both groups observed a wide range of scavenging coefficients, from less than 10 -5 to 4.0 x 10~4s -1 in Sperber's study and from 6.6 x 10~6 to 8.…”

Some characteristics of precipitation and dry periods on Long Island

“…The 50-100% increase in the mean length of dry and precipitation periods and the different frequency functions of the event data have ramifications for estimating residence times of soluble species in the atmosphere. The estimate of residence time from the models of Grandell (1972, 1981) is very sensitive to the mean value t, and the frequency function of dry periods for the range of observed scavenging coefficients of nitrate, sulfate and ammonium (Sperber, 1985;Hameed and Sperber, 1986;Sperber and Hameed, 1986). Residence time varies in a linear fashion with rd while an order of magnitude increase of the scavenging coefficient results in a factor of two decrease in residence time Grandell, 1972, 1981 ;Fisher, 1983;Sperber, 1985).…”