REVEAL II Summary of Data Analysis

SUMMARY

Analyses of the data collected during REVEAL II indicate:

Visibility conditions:

*In accord with analysis of the REVEAL data sets, average visibility as determined from nephelometer measurements is better at CHIL than CLBR. During REVEAL II the average meteorological range at both sites calculated for periods of simultaneous measurements were as follows: CLBR = 30 km, CHIL = 36 km.
*Although there is a high degree of spatial correlation between light scattering measurements, light scattering is higher and more variable at CLBR than CHIL.
Summertime visibility episodes in the central-eastern FV often occur after a period of elevated ozone concentrations.
Surface visual range from Vancouver and Abbotsford International Airports, light scattering from nephelometers, and visibility estimated from photographs show a high degree of association.
Light scattering measurements from CLBR and CHIL show the highest degree of association (correlation) in the daytime. This implies that at night local conditions may be decoupled from regional air quality.

PM₁₀ concentrations (PM₁₀ = particulate matter with diameter less than 10 痠):

Hourly PM₁₀ concentrations observed using TEOMs deployed at a number of sites in the Fraser Valley exceeded 30 痢m^-3 on an average of one hour in ten, and occasionally exceeded 50 痢m^-3 during REVEAL II.
PM₁₀ concentrations in the valley were highest at T28 (Downtown Abbotsford).
On average PM_2.5 contributes in excess of half of 24 hour average PM₁₀. (This indicates the presence of significant quantities of secondary aerosols.)

PM_2.5 concentrations and composition (PM_2.5 = particulate matter with diameter less than 2.5 痠):

Average fine mass measured during REVEAL, was approximately 8 痢m^-3 at CLBR and 9 痢m^-3 at CHIL. These values are six times the natural background concentration proposed for the western USA.
Comparison of elemental concentrations and fine mass from duplicate filter A analyses conducted at University of Guelph and University of California at Davis indicate a high correlation, but significant differences between absolute reported elemental concentrations for most of the measured species. Click here for sample plots of fine mass, sulphur and light absorption.
Inorganic aerosol species dominated measured fine mass during REVEAL II at both CLBR and CHIL but organic aerosols are a consistently high proportion of measured mass.
Elemental carbon concentration were significantly higher at CHIL than CLBR which may reflect the local influence of diesel tucks at the Chilliwack Works Yard.
The mean seasonal contributions of the five components of fine mass indicate: Highest nitrate and sulphate were observed in the summer. Highest organic mass was observed in the autumn and winter seasons. Lowest elemental carbon concentrations were observed during the summer. Highest soil concentrations were observed in winter perhaps due to the influence of strong outflow events and the large source areas available during the winter season.

PM_2.5 and visibility conditions:

*Average particle light scattering efficiencies are higher at CLBR than CHIL. This indicates that on a per unit mass basis aerosols at CLBR degrade visibility more efficiently than those sampled at CHIL. This reflects differing aerosol composition and is an explanation of the observation that meteorological range is lower at CLBR despite lower average fine mass.
Reconstructed light scattering budgets indicate inorganic aerosol species dominated light scattering at both CLBR and CHIL.
Days with high light scattering were characterized by higher nitrate and organic aerosol concentrations suggesting that these aerosol components may be the primary cause of variability of visibility conditions.

Source apportionment of PM_2.5:

Receptor modeling to identify sources of ambient aerosols indicates the following components dominate the sources of fine mass at the two receptor sites:

CLBR:	Mobile emissions, secondary aerosols, primary geologic materials, industrial emissions and a marine contribution (listed in terms of average contribution to measured mass).
CHIL:	Mobile emissions, secondary aerosols, primary diesel emissions, primary geologic materials, a marine contribution and a local component (dominated by iron) (listed in terms of average contribution to measured mass).

All items listed with an asterisk indicate findings which indicate the impact of local ammonia emissions on local visibility conditions and fine aerosol speciation. This hypothesis which was first presented in Pryor and Barthelmie (1996) is in good accord with observed aerosol ammonium measurements which indicate higher ammonium concentrations at CLBR than CHIL.

Reports from which these results are taken:

Pryor S.C. and Barthelmie R.J. (1996): REVEAL II: Characterizing fine aerosols in the Lower Fraser Valley. Final report of Part 1 analysis and database. Submitted to Fraser Cheam Regional District, Chilliwack.

Pryor S.C. and Barthelmie R.J. (1999): REVEAL II: Characterizing fine aerosols in the Lower Fraser Valley. Final report of data analysis and database construction. Submitted to Fraser Cheam Regional District, Chilliwack.