Towards an understanding of the fine particle variations in the LFV: integration of chemical, physical and meteorological observations

Detailed analysis of particle measurements in the Lower Fraser Valley of British Columbia has provided process-related explanations for the elevated PM2.5 observations. The meteorological conditions from 24–30 August contributed to the build-up of particles including concentrated layers aloft. During this period, seven PM2.5 peaks were “diagnosed” based upon their origin, age and/or processes. Of interest were the peaks in the late evening of 26 August (expected large secondary organic contribution), 29 August in the early afternoon (oldest particles during the period mixed with fresh combustion organics) and two peaks on 30 August. These latter two peaks showed elevated sulphate and were less than 3 h apart. The first was related to heterogeneous production and the second homogeneous production and nucleation. The type of analysis presented in this paper helps to identify unique situations for more detailed process studies. Successful interpretation of the observed PM2.5 required detailed meteorological analyses and was only possible with hourly or better mass quantification and size-resolved chemical characterization of the particles plus vertical aerosol backscatter profiles from LIDAR. This demonstrates the value of co-locating these approaches in the study of the processes influencing tropospheric aerosols.