TY - JOUR
T1 - Molecular Analysis of Secondary Brown Carbon Produced from the Photooxidation of Naphthalene
AU - Siemens, Kyla
AU - Morales, Ana
AU - He, Quanfu
AU - Li, Chunlin
AU - Hettiyadura, Anusha P S
AU - Rudich, Yinon
AU - Laskin, Alexander
PY - 2022/3/1
Y1 - 2022/3/1
N2 - We investigate the chemical composition of organic light-absorbing components, also known as brown carbon (BrC) chromophores, formed in a proxy of anthropogenic secondary organic aerosol generated from the photooxidation of naphthalene (naph-SOA) in the absence and presence of NOx. High-performance liquid chromatography equipped with a photodiode array detector and electrospray ionization high-resolution mass spectrometer is employed to characterize naph-SOA and its BrC components. We provide molecular-level insights into the chemical composition and optical properties of individual naph-SOA components and investigate their BrC relevance. This work reveals the formation of strongly absorbing nitro-aromatic chromophores under high-NOx conditions and describes their degradation during atmospheric aging. NOx addition enhanced the light absorption of naph-SOA while reducing wavelength-dependence, as seen by the mass absorption coefficient (MAC) and absorption Ångström exponent (AAE). Optical parameters of naph-SOA generated under low- and high-NOx conditions showed a range of values from MACOM 405nm ∼ 0.12 m2 g–1 and AAE300–450nm ∼ 8.87 (low-NOx) to MACOM 405nm ∼ 0.19 m2 g–1 and AAE300–450nm ∼ 7.59 (high-NOx), consistent with “very weak” and “weak” BrC optical classes, respectively. The weak-BrC class is commonly attributed to biomass smoldering emissions, which appear to have optical properties comparable with the naph-SOA. Molecular chromophores contributing to naphthalene BrC absorption were identified with substantial nitro-aromatics, indicating that these species may be used as source-specific markers of BrC related to the anthropogenic emissions.
AB - We investigate the chemical composition of organic light-absorbing components, also known as brown carbon (BrC) chromophores, formed in a proxy of anthropogenic secondary organic aerosol generated from the photooxidation of naphthalene (naph-SOA) in the absence and presence of NOx. High-performance liquid chromatography equipped with a photodiode array detector and electrospray ionization high-resolution mass spectrometer is employed to characterize naph-SOA and its BrC components. We provide molecular-level insights into the chemical composition and optical properties of individual naph-SOA components and investigate their BrC relevance. This work reveals the formation of strongly absorbing nitro-aromatic chromophores under high-NOx conditions and describes their degradation during atmospheric aging. NOx addition enhanced the light absorption of naph-SOA while reducing wavelength-dependence, as seen by the mass absorption coefficient (MAC) and absorption Ångström exponent (AAE). Optical parameters of naph-SOA generated under low- and high-NOx conditions showed a range of values from MACOM 405nm ∼ 0.12 m2 g–1 and AAE300–450nm ∼ 8.87 (low-NOx) to MACOM 405nm ∼ 0.19 m2 g–1 and AAE300–450nm ∼ 7.59 (high-NOx), consistent with “very weak” and “weak” BrC optical classes, respectively. The weak-BrC class is commonly attributed to biomass smoldering emissions, which appear to have optical properties comparable with the naph-SOA. Molecular chromophores contributing to naphthalene BrC absorption were identified with substantial nitro-aromatics, indicating that these species may be used as source-specific markers of BrC related to the anthropogenic emissions.
U2 - https://doi.org/10.1021/acs.est.1c03135
DO - https://doi.org/10.1021/acs.est.1c03135
M3 - مقالة
C2 - 35231168
SN - 0013-936X
VL - 56
SP - 3340
EP - 3353
JO - Environmental Science & Technology
JF - Environmental Science & Technology
IS - 6
ER -