Urban organic aerosol composition in Eastern China differs from North to South: Molecular insight from a liquid chromatography-Orbitrap mass spectrometry study

Particulate air pollution in China is influencing human health, ecosystem and climate. However, the chemical composition of particulate aerosol, especially of the organic fraction, is still not well understood. In this study, particulate aerosol samples with a diameter ≤ 2.5 μm (PM2.5) were collected in January 2014 in three cities located in Northeast, East and Southeast China, i.e., Changchun, Shanghai and Guangzhou, respectively. Organic aerosol (OA) in the PM2.5 samples was analyzed by ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution Orbitrap mass spectrometry in both negative mode (ESI−) and positive mode electrospray ioni…

Measurement report: PM<sub>2.5</sub>-bound nitrated aromatic compounds in Xi'an, Northwest China – seasonal variations and contributions to optical properties of brown carbon

Abstract. Nitrated aromatic compounds (NACs) are a group of key chromophores for brown carbon (light-absorbing organic carbon, i.e., BrC) aerosol, which affects radiative forcing. The chemical composition and sources of NACs and their contributions to BrC absorption, however, are still not well understood. In this study, PM 2.5 -bound NACs in Xi'an, Northwest China, were investigated for 112 daily PM 2.5 filter samples from 2015 to 2016. Both the total concentrations and contributions from individual species of NACs show distinct seasonal variations. The seasonally averaged concentrations of NACs are 2.1 (spring), 1.1 (summer), 12.9 (fall), and 56 ng m −3 (winter). Thereinto, 4-nitrophenol …

Supplementary material to "Measurement report: PM<sub>2.5</sub>-bound nitrated aromatic compounds in Xi'an, Northwest China: Seasonal variations and contributions to optical properties of brown carbon"

Concentrations, optical properties and sources of humic-like substances (HULIS) in fine particulate matter in Xi'an, Northwest China

Humic-like substances (HULIS) are ubiquitous in the atmospheric environment, which affects both human health and climate. We present here the mass concentration and optical characteristics of HULIS isolated from aerosol samples collected in Xi'an, China. Both mass concentration and absorption coefficient (Abs365) of HULIS show clear seasonal differences, with the highest average in winter (3.91 μgC m-3 and 4.78 M m-1, respectively) and the lowest in summer (0.65 μgC m-3 and 0.55 M m-1, respectively). The sources of HULIS_C and light absorption of HULIS were analyzed by positive matrix factorization (PMF) and four major sources were resolved, including secondary formation, biomass burning, c…

Characterization of the light absorbing properties, chromophores composition and sources of brown carbon aerosol in Xi'an, Northwest China

Abstract. The impact of brown carbon aerosol (BrC) on the Earth's radiative forcing balance has been widely recognized but remains uncertain, mainly because the relationships among BrC sources, chromophores, and optical properties of aerosol are poorly understood. In this work, the light absorption properties and chromophore composition of BrC were investigated for samples collected in Xi'an, Northwest China from 2015 to 2016. Both absorption Ångström exponent and mass absorption efficiency show distinct seasonal differences, which could be attributed to the differences in sources and chromophore composition of BrC. Three groups of light-absorbing organics were found to be important BrC ch…

Water-Insoluble Organics Dominate Brown Carbon in Wintertime Urban Aerosol of China: Chemical Characteristics and Optical Properties.

The chromophores responsible for light absorption in atmospheric brown carbon (BrC) are not well characterized, which hinders our understanding of BrC chemistry, the links with optical properties, and accurate model representations of BrC to global climate and atmospheric oxidative capacity. In this study, the light absorption properties and chromophore composition of three BrC fractions of different polarities were characterized for urban aerosol collected in Xi'an and Beijing in winter 2013-2014. These three BrC fractions show large differences in light absorption and chromophore composition, but the chromophores responsible for light absorption are similar in Xi'an and Beijing. Water-ins…

One-year characterization of organic aerosol markers in urban Beijing: Seasonal variation and spatiotemporal comparison

Abstract Organic aerosol (OA) is a major component of fine particulate matter (PM); however, only 10%–30% of OA have been identified as individual compounds, and some are used as markers to trace the sources and formation mechanisms of OA. The temporal and spatial coverage of these OA markers nonetheless remain inadequately characterized. This study presents a year-long measurement of 92 organic markers in PM2.5 samples collected at an urban site in Beijing from 2014 to 2015. Saccharides were the most abundant (340.1 ng m−3) species detected, followed by phthalic acids (283.4 ng m−3). In summer, high proportions (8%–24%) of phthalic acids, n-alkanes, fatty acids, and n-alcohols indicate dom…