Anthropogenic nitrogen oxide transport and deposition in Eastern North America

Abstract

A long-range atmospheric transport and transformation model is presented for nitrogen oxides emitted by man-made sources. The model parameters are optimized by matching the model output—annual average nitrate (NO − 3) wet deposition—to observed deposition at 109 precipitation sampling stations in eastern N America that operated continuously in the years 1980–1982. The root-mean-square residual between observations and predictions is 2.9 kg NO − 3 ha −1 y −1 or 19.7% of the root-mean-square observed value. The trend of estimated annual average NO − 3 concentrations in precipitation at Hubbard Brook, New Hampshire compares well with the observations from 1964 to 1981. Transfer coefficients decay nearly exponentially with distance with length scales of 200–800 km, depending on source-receptor orientation with respect to the resultant annual wind direction. The model is used for source apportionment of NO − 3 wet deposition at several receptors and for estimating a nitrogen budget for eastern N America, including the transboundary fluxes between the U.S. and Canada.