Development of Instrumentation for Measurement of Concentrations and Surface-Exchange Fluxes of Air Pollutants

Automated denuder systems have been developed for measurement of concentrations and exchange fluxes of ammonia and for simultaneous measurement of concentrations of nitric acid, nitrous acid, hydrochloric acid and sulfur dioxide. A new technique was established for sampling and analysis of aerosol, based on growth of particles under conditions of supersaturation and collection of the droplets in a cyclone. Surface exchange of ammonia has been studied over wheat, heathland and coniferous forest. Deposition to leaf surfaces is very efficient under humid conditions. Emission of ammonia from semi-natural vegetation was observed under dry conditions during the day. The dry deposition velocity of different size classes of particles was measured over a coniferous forest. The deposition velocity for sulfates showed a near-linear increase with u* and was twice as high as previously inferred, 1.2–1.5 cm s−1 on average.