PAM voltage-to-photochemically equivalent days calibration for this study can be found in the following manuscript:

Link, M. F., B. Friedman, R. Fulgham, P. Brophy, A. Galang, S. H. Jathar, P. Veres, J. M. Roberts, and D. K. Farmer (2016), Photochemical processing of diesel fuel emissions as a large secondary source of isocyanic acid (HNCO), Geophys. Res. Lett., 43, 40334041, doi:10.1002/2016GL068207.