Airborne observations constrain heterogeneous nitrogen and halogen chemistry on tropospheric and stratospheric biomass burning aerosol

We report field-derived N2O5 uptake coefficients, gamma(N2O5), and ClNO2 yields, phi(ClNO2), from two aircraft campaigns observing fresh smoke in the lower and mid troposphere and processed/aged smoke in the upper troposphere and lower stratosphere (UTLS).

Derived phi(ClNO2) varied across the full 0-1 range but was typically <0.5 and smallest in a PyroCB (<0.05). Derived gamma(N2O5) was low in agricultural smoke (0.2-3.6 x 10(-3)), extremely low in mid-tropospheric wildfire smoke (0.1 x 10(-3)), but larger in PyroCB processed smoke (0.7-5.0 x 10(-3)). Aged biomass burning aerosol in the UTLS had a higher gamma(N2O5) of 17 x 10(-3) that increased with sulfate and liquid water, but that was 1-2 orders of magnitude lower than values for aqueous sulfuric aerosol used in stratospheric models.