Neutralization of Anthropogenic Acidic Particles by NH₃ From Wildfire Over Tropical Peatland

TY - JOUR

T1 - Neutralization of Anthropogenic Acidic Particles by NH3 From Wildfire Over Tropical Peatland

AU - Budisulistiorini, Sri Hapsari

AU - Yang, Liudongqing

AU - Chen, Jing

AU - Cheng, Manqiu

AU - Kuwata, Mikinori

N1 - Funding Information: We acknowledge Guorong Chen for assisting the atmospheric observation. The authors gratefully acknowledge the NOAA Air Resources Laboratory for the providing the HYSPLIT transport used in this publication. This research was supported by the National Natural Science Foundation of China (42175121 and 42150610485), National Research Foundation Singapore under its Singapore NRF Fellowship scheme (National Research Fellow Award, NRF2012NRF-NRFF001-031), and NRF Campus for Research Excellence and Technological Enterprise (CREATE) Programme (NRF2016-ITCOO1-021). Funding Information: We acknowledge Guorong Chen for assisting the atmospheric observation. The authors gratefully acknowledge the NOAA Air Resources Laboratory for the providing the HYSPLIT transport used in this publication. This research was supported by the National Natural Science Foundation of China (42175121 and 42150610485), National Research Foundation Singapore under its Singapore NRF Fellowship scheme (National Research Fellow Award, NRF2012NRF‐NRFF001‐031), and NRF Campus for Research Excellence and Technological Enterprise (CREATE) Programme (NRF2016‐ITCOO1‐021). Publisher Copyright: © 2024. American Geophysical Union. All Rights Reserved.

PY - 2024/2/16

Y1 - 2024/2/16

N2 - Acidity is an essential characteristic of aerosol particles that influences chemical and physical properties. Aerosol particles in tropical Asia, such as Singapore, have been reported as highly acidic due to intense anthropogenic sulfur emissions. At the same time, the region has also been experiencing wildfire over tropical peatlands, which is recognized as an intense source of NH3. Here, we investigated the role of NH3 from wildfire on aerosol particles in Singapore by employing the aerosol mass spectrometric technique. The observation was conducted both during wildfire haze (2015 October and 2019 September–October) and non-haze (2018 October and 2019 April) periods. The observation result demonstrated that inorganic ionic species in Singapore were neutralized by NH4+ during the haze periods. Namely, the degree of neutralization of aerosol particles (i.e., measured NH4+ concentration/predicted NH4+ concentration by assuming that NH4+ fully neutralized SO42−, NO3−, and Cl−) was lower than 0.77during the non-haze periods. On the other hand, the corresponding values were higher than 0.93 during the haze periods. In addition, NO3− concentration during the daytime of the haze period in 2015 was higher than that in other observation periods. A thermodynamic model calculation suggested that the regime shifts from the “NH3 sensitive region” to the “NH3 and HNO3 sensitive region” or “HNO3 sensitive region” might have occurred during the haze period. In the future, continuous monitoring of both gas- and particle-phase inorganic chemical species will need to be conducted to investigate the impact of wildfire haze on atmospheric chemical processes in more detail.

AB - Acidity is an essential characteristic of aerosol particles that influences chemical and physical properties. Aerosol particles in tropical Asia, such as Singapore, have been reported as highly acidic due to intense anthropogenic sulfur emissions. At the same time, the region has also been experiencing wildfire over tropical peatlands, which is recognized as an intense source of NH3. Here, we investigated the role of NH3 from wildfire on aerosol particles in Singapore by employing the aerosol mass spectrometric technique. The observation was conducted both during wildfire haze (2015 October and 2019 September–October) and non-haze (2018 October and 2019 April) periods. The observation result demonstrated that inorganic ionic species in Singapore were neutralized by NH4+ during the haze periods. Namely, the degree of neutralization of aerosol particles (i.e., measured NH4+ concentration/predicted NH4+ concentration by assuming that NH4+ fully neutralized SO42−, NO3−, and Cl−) was lower than 0.77during the non-haze periods. On the other hand, the corresponding values were higher than 0.93 during the haze periods. In addition, NO3− concentration during the daytime of the haze period in 2015 was higher than that in other observation periods. A thermodynamic model calculation suggested that the regime shifts from the “NH3 sensitive region” to the “NH3 and HNO3 sensitive region” or “HNO3 sensitive region” might have occurred during the haze period. In the future, continuous monitoring of both gas- and particle-phase inorganic chemical species will need to be conducted to investigate the impact of wildfire haze on atmospheric chemical processes in more detail.

KW - aerosol

KW - ammonia

KW - degree of neutralization

KW - partitioning

KW - peatland

KW - wildfire

UR - http://www.scopus.com/inward/record.url?scp=85183745550&partnerID=8YFLogxK

U2 - 10.1029/2023JD039873

DO - 10.1029/2023JD039873

M3 - Article

AN - SCOPUS:85183745550

SN - 2169-897X

VL - 129

JO - Journal of Geophysical Research: Atmospheres

JF - Journal of Geophysical Research: Atmospheres

IS - 3

M1 - e2023JD039873

ER -