Roles of Relative Humidity and Particle Size on Chemical Aging of Tropical Peatland Burning Particles: Potential Influence of Phase State and Implications for Hygroscopic Property

TY - JOUR

T1 - Roles of Relative Humidity and Particle Size on Chemical Aging of Tropical Peatland Burning Particles

T2 - Potential Influence of Phase State and Implications for Hygroscopic Property

AU - Chen, Jing

AU - Budisulistiorini, Sri Hapsari

AU - Itoh, Masayuki

AU - Kuwata, Mikinori

N1 - Funding Information: We would like to thank Dr. Haris Gunawan and Satomi Shiodera for assisting in biomass sample collection in Southeast Asia. This work was supported by the National Natural Science Foundation of China (Grant Nos. 42105075 and no. 42175121), the Singapore National Research Foundation (NRF) under its Singapore National Research Fellowship scheme (National Research Fellow Award, NRF2012NRF‐NRFF001‐031), the NRF Campus for Research Excellence and Technological Enterprise (CREATE) program (NRF2016‐ITCOO1‐021), and Nanyang Technological University. M.I. was funded by the Ministry of Education, Culture, Sports, Science, and Technology for Science Research of Japan (18H02238 and 19H05666) and Research Institute for Humanity and Nature (RIHN; Project No. 14200117). Publisher Copyright: © 2022. American Geophysical Union. All Rights Reserved.

PY - 2022/7/13

Y1 - 2022/7/13

N2 - Peatland fires in Southeast Asia are an important source of primary organic aerosol (POA). Chemical aging of POA in the atmosphere produces oxygenated POA (OPOA). The OPOA production influences optical and hygroscopic properties, modulating the regional climate. However, the roles of environmental parameters such as relative humidity (RH) on chemical aging of peatland burning particles have rarely been investigated. Utilizing the potential aerosol mass (PAM) reactor, we conducted laboratory experiments for POA aging of particles generated from smoldering combustions of surface peat, fern, and Acacia leaves. The corresponding experiments for secondary organic aerosol formation were also separately conducted. Properties and chemical compositions of the resulting particle were quantified by both the hygroscopic tandem differential mobility analyzer and time-of-flight aerosol chemical speciation monitor (ToF-ACSM). Conversion of peat combustion from POA to OPOA was pronounced when RH in the PAM reactor was higher. Considering that previous electromicroscopic observations demonstrated that peat combustion POA is likely (semi)solid, we postulate that oxidation of fresh peatland burning particles is faster at an elevated RH due to reduced viscosity following hygroscopic growth. Hygroscopicity parameter (κ) of aged POA particles linearly correlated with the mass fraction of OPOA that was quantified by the ToF-ACSM. The above results highlight the importance of simultaneously measuring the chemical aging and particle phase state of peatland burning POA for quantifying their climatic impacts.

AB - Peatland fires in Southeast Asia are an important source of primary organic aerosol (POA). Chemical aging of POA in the atmosphere produces oxygenated POA (OPOA). The OPOA production influences optical and hygroscopic properties, modulating the regional climate. However, the roles of environmental parameters such as relative humidity (RH) on chemical aging of peatland burning particles have rarely been investigated. Utilizing the potential aerosol mass (PAM) reactor, we conducted laboratory experiments for POA aging of particles generated from smoldering combustions of surface peat, fern, and Acacia leaves. The corresponding experiments for secondary organic aerosol formation were also separately conducted. Properties and chemical compositions of the resulting particle were quantified by both the hygroscopic tandem differential mobility analyzer and time-of-flight aerosol chemical speciation monitor (ToF-ACSM). Conversion of peat combustion from POA to OPOA was pronounced when RH in the PAM reactor was higher. Considering that previous electromicroscopic observations demonstrated that peat combustion POA is likely (semi)solid, we postulate that oxidation of fresh peatland burning particles is faster at an elevated RH due to reduced viscosity following hygroscopic growth. Hygroscopicity parameter (κ) of aged POA particles linearly correlated with the mass fraction of OPOA that was quantified by the ToF-ACSM. The above results highlight the importance of simultaneously measuring the chemical aging and particle phase state of peatland burning POA for quantifying their climatic impacts.

KW - chemical aging

KW - hygroscopic property

KW - phase state

KW - relative humidity

KW - tropical peatland burning

UR - http://www.scopus.com/inward/record.url?scp=85134895993&partnerID=8YFLogxK

U2 - 10.1029/2022JD036871

DO - 10.1029/2022JD036871

M3 - Article

AN - SCOPUS:85134895993

SN - 2169-897X

VL - 127

JO - Journal of Geophysical Research: Atmospheres

JF - Journal of Geophysical Research: Atmospheres

IS - 14

M1 - e2022JD036871

ER -