Work by Sang Rin Lee and I on particle number and size distributions near roadways, using semi-Langrangian aerosol dynamics modeling. It's in HEI Report 179.
One of the best statistical evaluations for particle number out there (with the exception of some statistical models tested within their training data). Lee and Stanier achieved r = 0.76 for 24-h particle number prediction, and 85% of 24-h predictions within a factor of 2 of measured values, over 365 site-days over 18 sites in LA.
