Large contributions of biogenic and anthropogenic sources to fine organic aerosols in Tianjin, North China

Abstract

Abstract. In order to better understand the molecular composition and sources of organic aerosols in Tianjin, a coastal megacity in North China, ambient fine aerosol (PM2.5) samples were collected on a day/night basis from November to December 2016 and from May to June 2017. The organic molecular composition of PM2.5 components, including aliphatic lipids (n-alkanes, fatty acids, and fatty alcohols), sugar compounds, and photooxidation products from isoprene, monoterpene, β-caryophyllene, naphthalene, and toluene, was analysed using gas chromatography–mass spectrometry. Fatty acids, fatty alcohols, and saccharides were identified as the most abundant organic compound classes among all of the tracers detected in this study during both seasons. High concentrations of most organics at night in winter may be attributed to intensive residential activities such as house heating as well as the low nocturnal boundary layer height. Based on tracer methods, the contributions of the sum of primary and secondary organic carbon (POC and SOC respectively) to aerosol organic carbon (OC) were 24.8 % (daytime) and 27.6 % (night-time) in winter and 38.9 % (daytime) and 32.5 % (night-time) in summer. In detail, POC derived from fungal spores, plant debris, and biomass burning accounted for 2.78 %–31.6 % (12.4 %; please note that values displayed in parentheses in the following are average values) of OC during the daytime and 4.72 %–45.9 % (16.3 %) at night in winter, and 1.28 %–9.89 % (5.24 %) during the daytime and 2.08 %–47.2 % (10.6 %) at night in summer. Biomass-burning-derived OC was the predominant source of POC in this study, especially at night (16.0±6.88 % in winter and 9.62±8.73 % in summer). Biogenic SOC from isoprene, α-∕β-pinene, and β-caryophyllene exhibited obvious seasonal and diurnal patterns, contributing 2.23±1.27 % (2.30±1.35 % during the daytime and 2.18±1.19 % at night) and 8.60±4.02 % (8.98±3.67 % and 8.21±4.39 %) to OC in winter and summer respectively. Isoprene and α-∕β-pinene SOC were obviously elevated in summer, especially during the daytime, mainly due to strong photooxidation. Anthropogenic SOC from toluene and naphthalene oxidation showed higher contributions to OC in summer (21.0±18.5 %) than in winter (9.58±3.68 %). In summer, toluene SOC was the dominant contributor to aerosol OC, and biomass burning OC also accounted for a high contribution to OC, especially at night-time; this indicates that land/sea breezes also play an important role in the aerosol chemistry of the coastal city of Tianjin in North China.

Molecular characterization of firework-related urban aerosols using Fourier transform ion cyclotron resonance mass spectrometry

“…Under the influence of firework emission, both the O/C and H/C ratios decreased in the NYE N aerosol, while the DBE and the DBE/C ratio increased. Formulae with 0 < H/C ≤ 1.0 and O/C ≤ 0.5 dominantly have high DBE values (≥ 7.0), which is consistent with oxidized PAHs; e.g., the smallest PAH, naphthalene (C 10 H 8 ), has an H/C of 0.8 and a DBE of 7 (Tong et al, 2016;Feng et al, 2012). Moreover, as shown in Figs.…”

“…In addition, a high intensity of compounds with low DBE values and O atoms was present in the FW-related aerosols, such as C 16 H 32 O 2 , C 18 H 36 O 2 , C 20 H 40 O 2 , C 22 H 44 O 2 , and C 24 H 48 O 2 . They have an even carbon advantage, which could be fatty acids Kang et al, 2017;Fan et al, 2020). CHO compounds with aromatic index (AI) > 0.5, a characteristic of condensed aromatic ring structures, were also more abundant in the LNY daytime (777 compounds) than in the NYE nighttime (484 compounds) ( Table 3).…”

“…The levels of haze pollution are strongly dependent on the source of haze particles, e.g., industry, coal combustion, vehicle emissions, cooking, and biomass burning (Sun et al, 2013;Zheng et al, 2005). Among different haze particle sources the firework (FW) emission can be expected to play an important role in urban air quality during festivals (Feng et al, 2012;Jing et al, 2014;Jiang et al, 2015;Tian et al, 2014). However, the chemical composition of FW-related aerosols, especially the organic fraction, is not well characterized.…”

“…Published by Copernicus Publications on behalf of the European Geosciences Union. There are a high number of pollutants released by FW burning, such as sulfur dioxide, nitrogen oxide, volatile organic compounds, and particles comprising inorganic materials (e.g., potassium and sulfate), and organic compounds (e.g., n-alkanes and polycyclic aromatic hydrocarbons, PAHs) (Feng et al, 2012). They impose threats on human health (Sarkar et al, 2010) and can reduce visibility (Vecchi et al, 2008).…”

Seasonal variation and secondary formation of size-segregated aerosol water-soluble inorganic ions in a coast megacity of North China Plain

“…Tianjin, the largest coastal city in the NCP, is located along the Haihe River and is adjacent to both the Bohai Sea and the East China Sea. Owing to its location, the city has suffered severe haze pollution along with rapid economic and industrial development over the past few decades (Fan et al 2020).…”