Air-Water Partitioning of Biomass-Burning Phenols and the Effects of Temperature and Salinity

摘要

Biomass burning (BB) emits organic gases that, with chemical aging, can form secondary organic aerosol (SOA) in both the gas and aqueous phases. One class of biomass- ' burning emissions, phenols, are of interest because they react rapidly in the aqueous phase to efficiently form SOA, which might affect climate and human health. However, while measurements exist for the air-water partitioning constants of some simple phenols, Henry's law constants (K_H) are unknown for more complex BB phenols. In this work, we use a custom-built apparatus to measure K_H for a suite of biomass-burning phenols that span a wide range of air-water partitioning coefficients. Comparing our measurements to predicted values from EPI Suite shows that this model consistently overestimates K_H unless a suitable measured phenol K_H value is included to adjust the calculations. In addition, we determine the effect of five salts on phenol partitioning by measuring the Setschenow coefficients (K_S). Across the eight phenols we examined, values of K_S depend primarily on salt identity and descend in the order (NH_4)_2SO_4 ＞ NaCl ＞ NH_4Cl ≥ KNO_3 ＞ NH_4NO_3. Lastly, we use our K_H and K_S results to discuss the aqueous processing of biomass-burning phenols in cloud/fog water versus aerosol liquid water.