Primary nature of brown carbon absorption in a frigid atmosphere with strong haze chemistry
Introduction
Light-absorbing organic aerosol (OA), which is commonly referred to as brown carbon (BrC; Andreae and Gelencsér et al., 2006; Laskin et al., 2015), is increasingly involved in climate models to predict the radiative effects of particulate matter. BrC has both primary and secondary sources. Biomass burning (BB) is a major contributor to primary BrC (BrCpri), while precursors of secondary BrC (BrCsec) include both anthropogenic and biogenic volatile organic compounds (VOCs). It has been widely accepted that BrCsec is generally less absorbing than BrCpri and in addition, secondary BrC produced by anthropogenic precursors typically have stronger light absorption capacities than those from biogenic VOCs (Laskin et al., 2015). However, it remains difficult to properly constrain the emissions and subsequent atmospheric processes (e.g., transport and transformation) of BrC, adding substantial challenges to BrC simulation (Feng et al., 2013; Saleh et al., 2014; Zhang et al., 2017; Wang et al., 2018). The difficulties are partially due to the different optical properties observed in ambient aerosols versus laboratory generated BrC, which are usually produced by combustion of various fuels (fossil or biomass) or by oxidation of various precursors. For example, the field observation by Forrister et al. (2015) and the chamber experiment by Cappa et al. (2020), both of which focused on biomass burning smoke, showed opposite patterns for the evolution of BrC absorption, i.e., decreasing by more than 90% vs. increasing by a factor of 1.6 after 1 day of aging. Actually, comparison of BrC results across studies is frequently not straightforward, given the multitude of measurement methods. In general, two types of techniques have been widely used to determine BrC, i.e., spectrophotometric measurement of BrC solution (with water and methanol as the most commonly used solvents; Liu et al., 2013, 2015; Zeng et al., 2020) and attribution of wavelength-resolved aerosol absorption, either filter-based (Sandradewi et al., 2008) or in-situ (Lack et al., 2012), to BrC and black carbon (BC) absorption. While there are studies evaluating uncertainties of the respective approach (e.g., Lack and Langridge, 2013), comparisons between BrC measurement methods are still lacking and the inter-method difference (e.g., regarding its magnitude) has not been well addressed with limited studies (Shetty et al., 2019; Moschos et al., 2021).
Recently, research on BrC received a boost from a growing interest in incorporating OA absorption into climate models (Samset et al., 2018; Saleh, 2020). In China, BrC has been intensively explored in laboratory studies focusing on primary and/or secondary OA (e.g., Tang et al., 2020; Ni et al., 2021; Zhang et al., 2020, 2021), and in field observations covering not only megacities such as Beijing (Yan et al., 2015), Nanjing (Liu et al., 2019), Guangzhou (Qin et al., 2018) and Xi'an (Wu et al., 2020) but also remote sites such as those in or around the Tibetan Plateau (Li et al., 2016; Wu et al., 2018; Wang et al., 2019b). Despite the progress, there are still gaps to be filled, e.g., observational results on ambient BrC are far from being enough, considering the large spatial variations of primary emissions and meteorological conditions in China. This is particularly the case for the Harbin-Changchun (HC) metropolitan area, the northernmost national-level city cluster in China. HC consists of 11 cities located in the severe cold climate region in the Northeast Plain, and the extremely cold winter, with daily-average temperatures down to < −20 °C, differs it from other city clusters such as those located in the North China Plain, the Yangtze River Delta and the Fenwei Plain. However, there are much fewer studies focusing on the aerosols, including BrC, in HC (Tao et al., 2017), e.g., for the heating season when massive air pollutants are emitted (e.g., by burning of fossil fuels and biofuels; Li et al., 2020a) and transformed in the frigid atmosphere.
In this study, we investigated the optical properties and sources of BrC during a recent heating season in Harbin, the central city of HC. As can be seen from the air quality data published by the China National Environmental Monitoring Center (CNEMC), a unique feature of this campaign was that it covered January of 2020, during which Harbin was listed in the bottom 10 Chinese cities with worst air quality. The monthly-average concentration of fine particulate matter (PM2.5) reached as high as 155 μg/m3 in Harbin. Thus, this study provided observational results on BrC during heavily-polluted winter haze events in a largely unexplored city cluster, which could enrich the understanding of BrC in China.
Section snippets
Field observation
Field measurements were conducted following the procedures described in Cheng et al. (2021b). Briefly, PM2.5 samples were collected on a daily basis in the campus of Harbin Institute of Technology (HIT) from 16 October 2019 to 4 February 2020 (N = 112), using a low volume sampler (MiniVol; Airmetrics, OR, USA) operated with quartz-fiber filters (2500 QAT-UP; Pall Corporation, NY, USA) at a flow rate of 5 L/min. The samples were cut into four punches, and the following laboratory analyses were
Enhanced secondary BrC formation at high RH
MSOC concentrations apportioned to the SA-1 and SA-2 factors were specified as the masses of secondary BrC (BrCsec). Considerable variations were identified in the time series of BrCsec during the measurement period. As shown in Fig. 2a, the first half of the campaign, i.e., mid-October to early December 2019, exhibited relatively low BrCsec concentrations, with an average of 1.78 ± 1.18 μgC/m3. However, a large increase of BrCsec occurred for the second half of this study, with persistently
Conclusions
As a recently-identified driver for climate change, BrC remains largely unexplored for Northeast China, with few observational results available to constrain the simulation of BrC for this region. To address this lack of understanding, field measurements were conducted in the central city of the Harbin-Changchun metropolitan area, which differs from other city clusters in China due to its extremely cold winter. The campaign covered a month representing one of the worst atmospheric pollution
Credit author contribution statement
Yuan Cheng: Conceptualization, Methodology, Writing-Original Draft. Xu-bing Cao, Qin-qin Yu, Zhen-yu Du and Lin-lin Liang: Investigation. Jiu-meng Liu: Conceptualization, Methodology, Writing-Review & Editing. Peng Wang: Validation. Cai-qing Yan: Formal analysis. Qiang Zhang and Ke-bin He: Supervision, Writing-Review & Editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the National Natural Science Foundation of China (41805097), the Natural Science Foundation of Heilongjiang Province (YQ2019D004), the State Key Laboratory of Urban Water Resource and Environment (ES202006), Longfengshan Regional Atmospheric Background Station and Heilongjiang Touyan Team.
References (76)
- et al.
Seasonal and spatial variations of optical properties of light absorbing carbon and its influencing factors in a typical polluted city in Yangtze River Delta, China
Atmos. Environ.
(2019) - et al.
Brown carbon in atmospheric fine particles in Yangzhou, China: light absorption properties and source apportionment
Atmos. Res.
(2020) - et al.
The characteristics of brown carbon aerosol during winter in Beijing
Atmos. Environ.
(2016) - et al.
A yearlong study of water-soluble organic carbon in Beijing II: light absorption properties
Atmos. Environ.
(2014) - et al.
Insights into the origin and evolution of carbonaceous aerosols in a mediterranean urban environment
Chemosphere
(2019) - et al.
Optical characteristics and source apportionment of brown carbon in winter PM2.5 over Yulin in Northern China
Atmos. Res.
(2018) - et al.
High time resolution observation of PM2.5 brown carbon over Xi'an in northwestern China: seasonal variation and source apportionment
Chemosphere
(2019) - et al.
Light absorption characteristics of carbonaceous aerosols in two remote stations of the southern fringe of the Tibetan Plateau, China
Atmos. Environ.
(2016) - et al.
Impact of secondary and primary particulate matter (PM) sources on the enhanced light absorption by brown carbon (BrC) particles in central Los Angeles
Sci. Total Environ.
(2020) - et al.
Light-absorbing and fluorescent properties of atmospheric brown carbon: a case study in Nanjing, China
Chemosphere
(2020)
Chemical characteristics and light-absorbing property of water-soluble organic carbon in Beijing: biomass burning contributions
Atmos. Environ.
A new method for extraction of methanol-soluble brown carbon: implications for investigation of its light absorption ability
Environ. Pollut.
Light absorption properties of brown carbon over the southeastern Tibetan Plateau
Sci. Total Environ.
Emission factors for open and domestic biomass burning for use in atmospheric models
Atmos. Chem. Phys.
Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols
Atmos. Chem. Phys.
Biomass-burning-derived particles from a wide variety of fuels – Part 2: effects of photochemical aging on particle optical and chemical properties
Atmos. Chem. Phys.
Size-resolved characterization of the chromophores in atmospheric particulate matter from a typical coal-burning city in China
J. Geophys. Res. Atmos.
Light absorption by organic carbon from wood combustion
Atmos. Chem. Phys.
Air quality and health benefits of China's current and upcoming clean air policies
Faraday Discuss
Strong impacts of legitimate open burning on brown carbon aerosol in Northeast China
Environ. Sci. Technol. Lett.
Dramatic changes in Harbin aerosol during 2018–2020: the roles of open burning policy and secondary aerosol formation
Atmos. Chem. Phys.
Photochemical degradation affects the light absorption of water-soluble brown carbon in the South Asian outflow
Sci. Adv.
Determination of levoglucosan in biomass combustion aerosol by high-performance anion-exchange chromatography with pulsed amperometric detection
Atmos. Environ.
Brown carbon: a significant atmospheric absorber of solar radiation?
Atmos. Chem. Phys.
Evolution of brown carbon in wildfire plumes
Geophys. Res. Lett.
Day-night variability of water-soluble ions in PM10 samples collected at a traffic site in southeastern Spain
Environ. Sci. Pollut. Res.
Water-soluble organic aerosol material and the light-absorption characteristics of aqueous extracts measured over the Southeastern United States
Atmos. Chem. Phys.
Brown carbon aerosol in urban Xi’an, Northwest China: the composition and light absorption properties
Environ. Sci. Technol.
Water-Insoluble organics dominate brown carbon in wintertime urban aerosol of China: chemical characteristics and optical properties
Environ. Sci. Technol.
Light absorbing properties of primary and secondary brown carbon in a tropical urban environment
Environ. Sci. Technol.
Water-soluble organic carbon aerosols during a full New Delhi winter: isotope-based source apportionment and optical properties
J. Geophys. Res. Atmos.
Light absorption properties of brown carbon in the high Himalayas
J. Geophys. Res. Atmos.
Non-methane organic gas emissions from biomass burning: identification, quantification, and emission factors from PTR-ToF during the FIREX 2016 laboratory experiment
Atmos. Chem. Phys.
On the attribution of black and brown carbon light absorption using the Ångström exponent
Atmos. Chem. Phys.
Brown carbon and internal mixing in biomass burning particles
Proc. Natl. Acad. Sci. U.S.A.
Relationship between oxidation level and optical properties of secondary organic aerosol
Environ. Sci. Technol.
Chemistry of atmospheric brown carbon
Chem. Rev.
Fast pyrolysis of LERDADEs for renewable biofuels
IET Renew. Power Gener.
Cited by (7)
A short climatology of black and brown carbon and their sources at a suburban site impacted by smoke in Brazil
2024, Journal of Environmental Sciences (China)Wintertime Heavy Haze Episodes in Northeast China Driven by Agricultural Fire Emissions
2024, Environmental Science and Technology LettersA Review on Brown Carbon Aerosol in China: From Molecular Composition to Climate Impact
2024, Current Pollution ReportsContinuous Measurement and Molecular Compositions of Atmospheric Water-Soluble Brown Carbon in the Nearshore Marine Boundary Layer of Northern China: Secondary Formation and Influencing Factors
2023, Journal of Geophysical Research: AtmospheresMeasurement report: Diurnal variations of brown carbon during two distinct seasons in a megacity in northeast China
2023, Atmospheric Chemistry and Physics