Atmospheric aerosol compositions and sources at two national background sites in northern and southern China

Abstract

Although China's severe air pollution has become a focus in the field of atmospheric chemistry and the mechanisms of urban air pollution there have been researched extensively, few field sampling campaigns have been conducted at remote background sites in China, where air pollution characteristics on a larger scale are highlighted. In this study, an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), together with an Aethalometer, was deployed at two of China's national background sites in northern (Lake Hongze site; 33.23 • N, 118.33 • E; altitude 21 m) and southern (Mount Wuzhi site; 18.84 • N, 109.49 • E; altitude 958 m) China in the spring seasons in 2011 and 2015, respectively, in order to characterize submicron aerosol composition and sources. The campaign-average PM 1 concentration was 36.8 ± 19.8 µg m −3 at the northern China background (NCB) site, which was far higher than that at the southern China background (SCB) site (10.9 ± 7.8 µg m −3 ). Organic aerosol (OA) (27.2 %), nitrate (26.7 %), and sulfate (22.0 %) contributed the most to the PM 1 mass at NCB, while OA (43.5 %) and sulfate (30.5 %) were the most abundant components of the PM 1 mass at SCB, where nitrate only constituted a small fraction (4.7 %) and might have contained a significant amount of organic nitrates (5-11 %). The aerosol size distributions and organic aerosol elemental compositions all indicated very aged aerosol particles at both sites. The OA at SCB was more oxidized with a higher average oxygen to carbon (O / C) ratio (0.98) than that at NCB (0.67). Positive matrix factorization (PMF) analysis was used to classify OA into three components, including a hydrocarbon-like component (HOA, attributed to fossil fuel combustion) and two oxygenated components (OOA1 and OOA2, attributed to secondary organic aerosols from different source areas) at NCB. PMF analysis at SCB identified a semi-volatile oxygenated component (SV-OOA) and a lowvolatility oxygenated component (LV-OOA), both of which were found to be secondary species and could be formed from precursors co-emitted with BC. Using the total potential source contribution function model, the likely source areas of the major PM 1 components at both sites were a on large regional scale in East Asia. The possible sources may include not only emissions from the Chinese mainland but also emissions from ocean-going cargo ships and biomass burning in neighboring countries.Published by Copernicus Publications on behalf of the European Geosciences Union.

Volatility measurement of atmospheric submicron aerosols in an urban atmosphere in southern China

“…Huang et al (2012) also pointed out that HOA could be oxidized to SOA based on the analysis of their diurnal variations. This potential can be further supported by the fact that it was difficult to resolve HOA in downwind regions far from urban and industrial areas in China, implying that HOA had been oxidized during the air mass transport Zhu et al, 2016). There- fore, the modeling work needs to consider the process from HOA to SOA in future.…”

Characterization of nighttime formation of particulate organic nitrates based on high-resolution aerosol mass spectrometry in an urban atmosphere in China

“…During the sampling periods, chemical composition of non-refractory PM 1 was measured by an aerodyne HR-ToF-AMS, and detailed descriptions of this instrument are given in the literature (DeCarlo et al, 2006;Canagaratna et al, 2007). The setup and operation of the HR-ToF-AMS can be found in our previous publications (Huang et al, , 2012Zhu et al, 2016). To remove coarse particles, a PM 2.5 cyclone inlet was installed before the sampling copper tube with a flow rate of 10 L min −1 .…”

Characterization of nighttime formation of particulate organic nitrates based on high-resolution aerosol mass spectrometry in an urban atmosphere in China

“…Only non-refractory species can be vaporized and detected. The setup and operation of the HR-ToF-AMS can be found in our previous studies (Huang et al, 2010(Huang et al, , 2012Zhu et al,2016). To remove coarse particles, a PM2.5 cyclone inlet was placed on the roof of the building to introduce an air stream containing the remaining particles into a room through a copper tube with a flow rate of 10 l min −1 .…”

“…In addition to the PMF of the organic mass spectra (Zhang et al, 2011;Ng et al, 2010;Huang et al, 2013), the same analysis of the HR organic mass spectra, combined with NO + and NO2 + , ions was performed to identify the relative contributions of organ ic and inorganic nitrates (Hao et al, 2014;Xu et al, 2015b). In this study, the detailed PMF analysis procedure can be found in our previous publications (Huang et al, 2010;Zhu et al, 2016;He et al, 2011). For each season, three organic factors and one inorganic factor are identified: a hydrocarbon-like OA (HOA), a more-oxidized oxygenated OA (MO-OOA), a less-oxidized oxygenated OA (LO-OOA) and a nitrate inorganic aerosol (NIA).…”