IMPLICATIONS OF AMMONIA EMISSIONS FOR FINE AEROSOL FORMATION AND VISIBILITY IMPAIRMENT - A CASE-STUDY FROM THE LOWER FRASER VALLEY, BRITISH-COLUMBIA

Ammonia enhances atmospheric aerosol formation and, once in the aeroso l form, enhances the light extinction characteristics of those aerosol s. In this paper, an ammonia emissions inventory is developed for the Lower Fraser Valley (LFV) of British Columbia and used in conjunction with ambient ammonia and ammonium measurements to explain: (i) the obs erved temporal and spatial variability of fine inorganic aerosol compo sition and concentrations in the valley, and (ii) the severity and spa tial variability of visibility degradation in the LFV. It is proposed here that advection of urban emissions of nitrogen and sulphur oxides over agricultural areas in the eastern and central valley with higher ammonia emissions favours subsequent ammonium nitrate and sulphate for mation. This leads to higher fine mass concentrations and lowest visib ility in the predominantly agricultural regions of the valley. (C) 199 8 Elsevier Science Ltd. All rights reserved.