A method to dynamically constrain black carbon aerosol sources with online monitored potassium

The result of Aethalometer model to black carbon (BC) source apportionment is highly determined by the absorption Angstrom exponent (α) of aerosols from fossil fuel combustion (αff) and wood burning (αwb). A method using hourly measured potassium to calculate the αff and αwb values was developed in this study. Results showed that the optimal αff and αwb were 1.09 and 1.79 for the whole dataset. The optimal α values in the diurnal resolution were also calculated with αff and αwb varied in 1.02 –1.19 and 1.71–1.90, respectively. Using the dynamic α values, the Pearson correlation coefficient between BC and potassium from wood burning substantially improved compared to the results derived from the fixed α values. The method developed in this study is expected to provide more reasonable BC source identification results, which are helpful for air quality, climate, and human health modeling studies.