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

• Published in: Environmental science & technology Vol. 54; no. 7; pp. 3823 - 3830
• Main Authors: McFall, Alexander S, Johnson, Alex W, Anastasio, Cort
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 07.04.2020
• Subjects: Aerosols; Aging; Air temperature; Ammonium chloride; Ammonium nitrate; Ammonium sulfate; Biomass; Biomass burning; Burning; Fog; Gases; Henrys law; Partitioning; Phenols; Salts; Sodium chloride; Temperature effects; Water
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.9b06443

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 (NH4)2SO4 > NaCl > NH4Cl ≥ KNO3 > NH4NO3. 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.