CONCENTRATIONS OF ACIDIC AIR-POLLUTANTS IN THE NETHERLANDS

From October 1987 to April 1990 a monitoring study of atmospheric acid ity has been performed at three urban and five rural sites in The Neth erlands. Sampling was performed on a regular basis with annular denude r filter pack systems at all sites and a continuous sulfuric acid moni tor at one site. Very high ammonia concentrations (mean concentration higher than 10 mu g m(-3)) were observed at a site in an area with int ensive livestock farms. The mean ammonia concentration at the urban si tes was slightly higher than at the background sites. Despite the high ammonia concentrations the concentration of acid aerosol was not negl igible. High concentrations of acid aerosol have not been observed, th e highest daily average concentration, expressed as sulfuric acid, was 5.5 mu g m(-3). Daily average nitrous acid concentrations up to 20 mu g m(-3) have been observed, mostly at the more traffic influenced sit es. Small spatial variability of the concentration of the aerosol comp onents sulfate, nitrate and ammonium was found, consistent with the lo ng-range transport behavior of these components. Larger spatial variab ility was observed for the gaseous components HONO, HNO3 and particula rly ammonia, in agreement with the impact of local or regional sources . Copyright (C) 1996 Elsevier Science Ltd