REVEAL - CHARACTERIZING FINE AEROSOLS IN THE FRASER-VALLEY, BC

The REVEAL field study was conducted during July and August 1993 to do cument the chemical and physical characteristics of ambient fine aeros ols in southwestern British Columbia (B.C.) (particularly the Lower. F raser Valley (LFV)) and to quantify the impact of those aerosols upon visibility in the LFV A description of the study motivations, objectiv es and monitoring protocols are presented herein along with results of analyses conducted using the REVEAL datasets. It is shown that: visib ility and aerosol concentrations/composition are highly variable in. t he temporal and spatial dimensions, and while organic matter dominates fine aerosol mass (accounting for 35-46% of the mean fine aerosol mas s) in the LFV, nitrate this region. The severity of visibility impairm ent in the valley despite comparatively low fine and sulphate dominate particle light scattering (b(SP)) (accounting for 55-67% of mean b(SP )) in mass concentrations is attributed to the high mass scattering ef ficiencies of the ambient aerosols (due in part to the relative abunda nce of ammonia/ium). Source types of ambient fine aerosols at four of the monitoring sites are identified using Principal Components Analysi s (PCA), and used to calculate first approximations of mass contributi ons by source type using repression analysis. Results indicate that di rect vehicle emissions, secondary aerosols and soil/road dust dominate the sources of fine aerosols in the LFV. Analysis of supplementary da ta indicates that the REVEAL monitoring period was characterized by fa irly typical summertime visibility and meteorological conditions for t he region and hence that it is possible to generalize from these analy ses. The gross spatial features of the secondary fine aerosol distribu tion in the LFV are explained in relation to the prevailing meteorolog y and spatial patterns of precursor emissions.