Humic-like substances (HULIS) in springtime aerosols at a high-altitude background station in the western North Pacific: Source attribution, abundance, and light-absorption

Shantanu Kumar Pani; Chung-Te Lee; Stephen M Griffith; Neng-Huei Lin

doi:10.1016/j.scitotenv.2021.151180

Humic-like substances (HULIS) in springtime aerosols at a high-altitude background station in the western North Pacific: Source attribution, abundance, and light-absorption

Sci Total Environ. 2022 Feb 25:809:151180. doi: 10.1016/j.scitotenv.2021.151180. Epub 2021 Oct 23.

Authors

Shantanu Kumar Pani¹, Chung-Te Lee², Stephen M Griffith¹, Neng-Huei Lin³

Affiliations

¹ Department of Atmospheric Sciences, National Central University, Taoyuan 32001, Taiwan.
² Graduate Institute of Environmental Engineering, National Central University, Taoyuan 32001, Taiwan; Center for Environmental Monitoring and Technology, National Central University, Taoyuan 32001, Taiwan.
³ Department of Atmospheric Sciences, National Central University, Taoyuan 32001, Taiwan; Center for Environmental Monitoring and Technology, National Central University, Taoyuan 32001, Taiwan. Electronic address: nhlin@cc.ncu.edu.tw.

PMID: 34699812
DOI: 10.1016/j.scitotenv.2021.151180

Abstract

Atmospheric humic-like substances (HULIS) are important components of biomass-burning (BB) emissions and highly associated with light-absorbing organic aerosols (often referred to as brown carbon). This study highlights the importance of BB-emitted HULIS aerosols in peninsular Southeast Asian outflow to the subtropical western North Pacific. We determined various key light-absorbing characteristics of HULIS i.e. mass absorption cross-section (MAC_HULIS), absorbing component of the refractive index (k_HULIS), and absorption Ångström exponent (AAE_HULIS) based on ground-based aerosol light absorption measurements along with HULIS concentrations in springtime aerosols at Lulin Atmospheric Background Station (LABS; 2862 m above mean sea level), which is a representative high-altitude remote site in the western North Pacific. Daily variations of HULIS (0.58-12.92 μg m^-3) at LABS were mostly linked with the influence from incoming air-masses, while correlations with BB tracers and secondary aerosols indicated the attribution of primary and secondary sources. Stronger light absorption capability of HULIS was clearly evident from MAC_HULIS and k_HULIS values at 370 nm, which were about ~1.5 times higher during BB-dominated days (1.16 ± 0.75 m² g^-1 and 0.05 ± 0.03, respectively) than that during non-BB days (0.77 ± 0.89 m² g^-1 and 0.03 ± 0.04, respectively). Estimates from a simple radiative transfer model showed that HULIS absorption can add as much as 15.13 W g^-1 to atmospheric warming, and ~46% more during BB-dominated than non-BB period, highlighting that HULIS light absorption may significantly affect the Earth-atmosphere system and tropospheric photochemistry over the western North Pacific.

Keywords: 7-SEAS/BASELInE; Biomass-burning; Long-range transport; Lulin Atmospheric Background Station; Peninsular Southeast Asia; Simple forcing efficiency.

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Altitude
Biomass
Carbon / analysis
Environmental Monitoring
Humic Substances* / analysis
Particulate Matter / analysis

Substances

Aerosols
Air Pollutants
Humic Substances
Particulate Matter
Carbon