Chemical Characteristics and Brown Carbon Chromophores of Atmospheric Organic Aerosols Over the Yangtze River Channel: A Cruise Campaign

Abstract

Organic aerosols (OAs) have important influences on the climatic implications and health effects of atmospheric aerosols. Among the complex OA constituents, brown carbon (BrC) accounts for a substantial mass fraction and is of special interest because of its light‐absorbing properties. In this study, the chemical composition of atmospheric OAs over the middle‐lower Yangtze River (MLYR) channel, as well as the BrC, was investigated during a ship cruise campaign in winter 2015. In total, more than 1,000 molecular formulas were determined using a combination of ultra‐high performance liquid chromatography (UHPLC), a diode array detector (DAD), and Orbitrap high‐resolution mass spectrometry (HRMS). Large numbers and enhanced signal abundances for known tracers as well as monocyclic and polycyclic aromatics indicate that biomass burning and fossil combustion are important sources of OAs over the MLYR channel. In addition, 13 chromophores with strong light absorption, mostly representing established biomass burning tracers, were unambiguously determined by UHPLC/DAD/HRMS and contributed to 35–37% of the total light absorption of OAs at 290 nm and 58–70% at 350 nm. Sixty‐three previously identified biomass burning chromophores were also positively identified in the mass spectrometric analysis here but embedded in the humped signal during the spectroscopic analysis. These BrC chromophores exhibit high degrees of unsaturation, suggesting that these compounds are aromatic, nitro‐aromatic, and polycyclic aromatic type of species. Our results highlight the significant influence of biomass burning and fossil combustion on atmospheric OAs over the MLYR channel in the winter, strongly enhancing light‐absorbing properties and decreasing air quality.

Measurement report: Molecular composition, optical properties, and radiative effects of water-soluble organic carbon in snowpack samples from northern Xinjiang, China

“…The BC concentrations in snow were measured by a custom-developed two-sphere integration (TSI) spectrophotometer (Wang et al, 2020b) and have been reported by Shi et al (2020). The distribution of BC concentrations in snow samples is also shown in Fig.…”

Naphthalene‐Derived Secondary Organic Aerosols Interfacial Photosensitizing Properties

“…The OH‐initiated oxidation of naphthalene produces a number of different oxygenated compounds with high molecular weight and low‐volatility, which can partition into particles and contribute to SOA mass (Chan et al., 2009; Kautzman et al., 2010; Riva et al., 2015). Naphthoquinone, a naphthalene oxidation product (McWhinney et al., 2013), is commonly found in atmospheric aerosols (e.g., Shanghai, China [Wang et al., 2017]; Tempe, USA [Delhomme et al., 2008]; Kurashiki City, Japan [Oda et al., 2001]; Yangtze River channel [Wang et al., 2020b]), and is known to be an efficient photosensitizer, inducing redox chemistry or producing reactive oxygen species (De Lucas et al., 2014; McNeill & Canonica, 2016). SOA derived from oxidation of naphthalene under high‐NO x conditions has been shown to be weakly fluorescent (Lee et al., 2014), resilient to photobleaching (Aiona et al., 2018), efficient in photosensitizing singlet oxygen in aqueous solutions (Manfrin et al., 2019), capable of photosensitized oxidation of halide ions (Gemayel et al., 2021), and moderately effective in photosensitized oxidation of d‐limonene (Malecha & Nizkorodov, 2017).…”

Indoor heterogeneous photochemistry of molds and their contribution to HONO formation

“…The system was operated in both ESI+ and ESI− mode with a resolving mass power of 140 000 at m/z 200. A sodium acetate solution (2 mM in 50/50, v/v, ACN/water) was used for the mass calibration; this solution provides a series of negative and positive adduct ions in the scanning range of m/z 50–750 41,42 . The calibration method consisted in filling the syringe with a 2 mM solution of sodium acetate and setting the syringe pump flow rate to 20 µl min −1 .…”

“…41,42 This software provides the main functionality for MS data processing: raw data import, mass detection, chromatogram building, deisotoping, alignment, identification, and duplicate peak filtering. The detailed processing steps and settings can be found in Wang et al 42 and in Table S1. Molecular formulas tentatively identified were expressed as C c H h O o N n S s , where c, h, o, n, and s correspond to the numbers of carbon, hydrogen, oxygen, nitrogen, and sulfur atoms in the molecular formula, respectively.…”