Light absorption of brown carbon in eastern China based on 3-year multi-wavelength aerosol optical property observations at the SORPES station and an improved Absorption Ångstrom exponent segregation method

Abstract

Abstract. Brown carbon (BrC), a certain group of organic carbon (OC) with strong absorption from the visible to ultraviolet (UV) wavelengths, makes considerable contribution to light absorption on both global and regional scales. High concentration and proportion of OC has been reported in China, but studies of BrC absorption based on long-term observations are rather limited in this region. In this 20 study, we reported 3-year results of light absorption of BrC based on continuous measurement at the Station for Observation Regional Processes of the Earth System (SORPES) in the Yangtze River Delta, China combined with Mie-theory calculation. Light absorption of BrC was obtained using an improved Absorption Ångstrom exponent (AAE) segregation method to calculate AAE of 'pure' and nonabsorbing coated black carbon (BC) at each time step based on Mie-theory simulation and 25 measurement of multi-wavelength aerosol light absorption. By using this improved method, the variation of AAE over time is taken into consideration, making it applicable for long-term analysis.The yearly average light absorption of BrC (babs_BrC) at 370 nm was 4.3 Mm -1 at the SORPES station.The contribution of BrC to total aerosol absorption (PBrC) at 370 nm ranged from 6% to 18% (10 th and 90 th percentiles, respectively), and reached up to ~28% in biomass burning-dominant season and winter. 30

Significant Promotion of Light Absorption Ability and Formation of Triplet Organics and Reactive Oxygen Species in Atmospheric HULIS by Fe(III) Ions

“…found that the use of aromatic chromophores with visible light trapping ability and appropriate excited-state energy levels could effectively enhance the visible light absorption ability of certain transition metal complexes and prolong the triplet-state lifetime . In this way, the low-energy excited states (either singlet or triplet states) can be switched from the conventional metal-to-ligand charge transfer to π–π* states, while the ISC process of π–π*→ π–π* is often efficient, and the spin–orbit coupling (SOC) of the π–π* state leads to a longer-lived T 1 state due to the larger energy gap of the T 1 / S 0 state. ,, Although previous studies have focused on rare metals such as Ru, its homologue Fe retains a similarity to rare metals in studies on the properties of metal-to-ligand charge transfer excited states, which should be an important reason for the increased yield of the triplet state in the Fe 3+ -coupled system for highly oxidative HULIS.…”

“…Brown carbon (BrC) aerosols, which can absorb near-ultraviolet and visible light, − are important contributors to the radiative forcing and the greenhouse effect in the troposphere . As an important component of BrC, humic-like substances (HULIS) can also produce active intermediates, such as triplet organics and reactive oxygen species (ROS) via photochemistry, ,, and further initiate the aging process of organic aerosols in the particle phase. − For example, it has been found that triplet organics can oxidize isoprene and induce a portion of ROS, such as hydroxyl radical ( · OH), single oxygen ( 1 O 2 ), and superoxide (O 2 ·– ). , The atmospheric concentrations of HULIS, which mainly originated from terrestrial biomass burning (11–36%) and coal combustion (11–41%), are in the range of 0.39–13.4 μg·m –3 in China. − …”

Impacts of Regional-transported Biomass Burning Emissions on Chemical and Optical Properties of Carbonaceous Aerosols in Nanjing, East China

“…The light absorption coefficient of WSOC at 365nm is used to represent water-soluble BrC, which is organic carbon with a capacity of absorbing radiation (Yan et al, 2015;Hecobian et al, 2010;Wang et al, 2018a). The mean babs value was 9.4 ± 4.8 M m -1 , higher than the summertime value but lower than the wintertime value in Beijing and Guangzhou (Yan et al, 2015;Qin et al, 2018).…”

Review of Brown Carbon Aerosols in China: Pollution Level, Optical Properties, and Emissions

“…In addition, recent studies also suggest that BrC emitted from biomass burning is unstable due to chemical losses (Forrister et al., 2015; X. Wang, Heald, et al., 2016). The decay of BrC absorption due to photobleaching associated with aging processes could result in a 50% decrease of its DRF (Brown et al., 2018; X. Wang, Heald, et al., 2018).…”

“…S. Li et al (2018), Liakakou et al (2020), Meng et al (2020), Mo et al (2021), Park et al (2020, 2018), Park and Yu (2016), Peng et al (2020), Y. Qin et al (2018), Satish et al (2020, 2017), Shen et al (2017), Soleimanian et al (2020), J. Sun et al (2021, 2016, 2017), Tang et al (2020), Tian et al (2019), Voliotis et al (2017), J Wang, Nie, et al (2018),. Y., M Xie et al (2019Xie et al ( , 2017Xie et al ( , 2018,.…”