Source apportionment of carbonaceous aerosols using hourly data and implications for reducing PM2.5 in the Pearl River Delta region of South China.

Ambient fine particulate matter (PM2.5) levels in South China have been decreasing in the past decade, but the decreasing rates differed between its major chemical components, e.g., with much small rates for carbonaceous aerosols than for secondary inorganic aerosols. To investigate the sources of carbonaceous aerosols in this region, a comprehensive campaign was carried out in urban Guangzhou in the winter of 2019-2020 using a combination of various instruments. Data generated from this campaign include hourly total carbon (TC), black carbon (BC), criteria air pollutants and meteorological parameters, 4-hourly particle-bound elements, and chemically-resolved daily PM2.5. Similar diurnal patterns were observed for TC, CO and NO2, suggesting TC was very likely related to vehicle exhaust emission. Secondary organic carbon (SOC) estimated using the Minimum R squared (MRS) method accounted for 35 ± 17% of OC, indicating strong atmospheric oxidation capacity. Four major source factors for carbonaceous aerosols were identified by positive matrix factorization (PMF) model, including coal combustion, traffic emissions, soil dust and ship emissions, which accounted for 37 ± 23%, 39 ± 23%, 14 ± 10% and 10 ± 13%, respectively, of TC mass concentration, 38 ± 24%, 38 ± 23%, 14 ± 10% and 10 ± 12%, respectively, of OC mass concentration, and 29 ± 21%, 43 ± 22%, 14 ± 11% and 14 ± 15%, respectively, of EC mass concentration. Among these sources, traffic emission was the most important one, suggesting the necessity for promoting clean energy vehicles and relieving urban traffic congestion.

Intermediate-volatility aromatic hydrocarbons from the rubber products industry in China.

As key components of intermediate-volatility organic compounds (IVOCs), intermediate-volatility aromatic hydrocarbons (IAHs) are important precursors of ozone and secondary organic aerosol (SOA). Rubber products (RP) industry has significant influence on ozone and SOA formation, yet few studies are available to characterize their emissions of IAHs. Here we conducted measurements of IAHs emitted from rubber products (RP) factories in China. Tens of C10-C12 IAH species were identified with C10H14-AH (such as tetramethyl benzene) and naphthalene (C10H8) as the dominant species, accounting for 57.0 % - 100.0 % of total IAHs emissions. On average, IAHs showed higher concentrations (1.1 × 102-1.2 × 103 µg m-3) in mixing, extrusion, painting, crushing, and grinding processes than those (8.2-14 µg m-3) in vulcanization and gumming processes as well as warehouse. Moreover, IAHs concentrations were 1.3-1.7 times of volatile aromatic hydrocarbons (VAHs; C6-C9 aromatics) in the emissions from mixing, extrusion, crushing and grinding processes. The average IAHs to volatile organic compounds (VOCs) ratios also showed relatively higher values (0.1-0.7) in these processes, which were significantly higher than those of 0.01-0.03 observed in other industries, and even comparable to the IVOCs to VOCs ratio of 0.2 used for estimating solvent-related emission. The ozone and SOA formation potential values of IAHs were 1.1-2.6 times and 0.9-3.9 times those of VAHs, respectively, and were 0.5-1.0 times and 0.9-1.9 times those of total VOCs in emissions of mixing, extrusion, crushing, and grinding processes of the RP industry. The total emission of IAHs was estimated to be 115.8 Gg from the RP industry in China, which could account for 64.5 % of total IAH emissions from all industrial sectors. This study further suggests that the RP industry might be an important emission source of IAHs with substantially higher ozone and SOA formation potentials.

[Characteristics and Source Apportionment of Volatile Organic Compounds (VOCs) in a Typical Industrial Area in Dongguan During Periods of Ozone and Non-ozone Pollution in Summer].

To investigate the characteristics and sources of atmospheric volatile organic compounds (VOCs) in a typical industrial zone in Dongguan, 56 VOCs species were continuously measured in Houjie Town of Dongguan in summer of 2020. In addition, mass concentrations of O3, NOx, and CO and meteorological data were synchronously collected. Then, characteristics of total VOCs and major species, the contributions of major VOCs species to ozone formation potential (OFP), and source apportionment of VOCs under the different ozone concentrations were discussed. The mean mixing ratio of VOCs was 53.1×10-9 including aromatics (24.7×10-9), alkanes (23.7×10-9), alkenes (3.9×10-9), and alkynes (0.7×10-9). The mean mixing ratios of aromatics, alkanes, alkenes, and alkynes increased approximately 10%, 43%, 38%, and 98% during the period of ozone pollution, respectively, compared with those during the period of non-ozone pollution. Aromatics contributed the most to OFP during the periods of both ozone pollution and non-ozone pollution, followed by alkanes, alkenes, and alkynes. Solvent sources, liquefied petroleum gas (LPG) leakage, fossil fuel combustion, and hydrocarbon volatilization were resolved using the PMF model, which accounted for 60%±20%, 16%±11%, 15%±11%, and 9%±6% of total VOCs, respectively. During the period of ozone pollution, the contribution of solvent sources to the total VOCs decreased to 44%, whereas that of LPG leakage and hydrocarbon volatilization increased to 21% and 16%, respectively.