During July and August 1993 the REVEAL (Regional Visibility Experimental Assessment in the Lower Fraser Valley) field campaign was undertaken to characterize summertime visibility and ambient aerosol loadings in southwestern British Columbia (B.C.).

Highlights of analyses of the REVEAL data:

• Visibility and aerosol concentrations/composition are highly variable in the temporal and spatial dimensions.
• While organic matter dominates fine aerosol mass (accounting for 35-46% of the mean fine aerosol mass) in the LFV, nitrate and sulphate dominate particle light scattering (b_sp) (accounting for 55-67% of mean b_sp) in this region.
• The severity of visibility impairment in the valley despite comparatively low fine mass concentrations is attributed to the high mass scattering efficiencies of the ambient aerosols (due in part to the relative abundance of ammonia/ium).
• Results of source apportionment analyses of fine aerosols at four of the monitoring sites indicate that direct vehicle emissions, secondary aerosols and soil/road dust dominate the sources of fine aerosols in the LFV.
• Visibility conditions are frequently degraded below publically defined 'acceptable levels'.

Following REVEAL it was decided to undertake a second less intensive study (REVEAL II). The main aims of REVEAL II were to collect and analyze ambient data in order:

• To characterize aerosol and visibility conditions in the Lower Fraser Valley (LFV) over an entire year.
• To provide public information regarding the sources and effects of current aerosol concentrations.

Analysis of the REVEAL data were reported in a number of refereed journal articles. A non-inclusive list is as follows:

Barthelmie R.J., and Pryor S.C. (1998): Implications of ammonia emissions for fine aerosol formation and visibility impairment - A case study from the Lower Fraser Valley, British Columbia. Atmospheric Environment 32 345-352 .

Barthelmie R.J., and Pryor S.C. (1997): Secondary organic aerosols: Formation potential and ambient data. The Science of the Total Environment 205 167-178.

Pryor S.C., Barthelmie R.J., Hoff R., Sakiyama S., Simpson R., and Steyn D. (1997): REVEAL: Characterizing fine aerosols in the Fraser Valley, B.C.. Atmosphere-Ocean 35 209-227.

Pottier J., Pryor S.C., and Banta R. (1997): Synoptic variability related to boundary layer and surface features observed during Pacific '93. Atmospheric Environment 31 2163-2173.

Hoff R., Harwood M., Sheppard A., Froude F., Martin J., Strapp W. (1997): Use of airborne LIDAR to determine aerosol sources and movement in the Lower Fraser Valley, BC. Atmospheric Environment 31 2123-2134.

Pryor S. C., Simpson R., Guise-Bagley L., Hoff R., and Sakiyama S. (1997): Visibility and aerosol composition in the Fraser Valley during REVEAL. Journal of the Air and Waste Management Association 41 147-156.

Pryor S. C. (1996): Assessing public perception of visibility for standard setting exercises. Atmospheric Environment 30 2705-2716.

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