Chemical and stable carbon isotopic composition of PM<sub>2.5</sub> from on-road vehicle emissions in the PRD region and implications for vehicle emission control policy

Abstract

Abstract. Vehicle emissions are a major source of urban air pollution. In recent decade, the Chinese government has introduced a range of policies to reduce vehicle emissions. In order to understand the chemical characteristics of PM2.5 from on-road vehicle emissions in the Pearl River Delta (PRD) region and to evaluate the effectiveness of control policies on vehicle emissions, the emission factors of PM2.5 mass, elemental carbon (EC), organic carbon (OC), water-soluble organic carbon (WSOC), water-soluble inorganic ions (WSII), metal elements, organic compounds and stable carbon isotopic composition were measured in the Zhujiang tunnel of Guangzhou, in the PRD region of China in 2013. Emission factors of PM2.5 mass, OC, EC and WSOC were 92.4, 16.7, 16.4 and 1.31 mg vehicle−1 km−1 respectively. Emission factors of WSII were 0.016 (F-) ~ 4.17 (Cl−) mg vehicle−1 km−1, contributing about 9.8% to the PM2.5 emissions. The sum of 27 measured metal elements accounted for 15.2% of PM2.5 emissions. Fe was the most abundant metal element, with an emission factor of 3.91 mg vehicle−1 km−1. Emission factors of organic compounds including n-alkanes, polycyclic aromatic hydrocarbons, hopanes and steranes were 91.9, 5.02, 32.0 and 7.59 μg vehicle−1 km−1, respectively. Stable carbon isotopic composition δ13C value was −25.0‰ on average. An isotopic fractionation of 3.2‰ was found during fuel combustion. Compared to a previous study in Zhujiang tunnel in 2004, emission factors of PM2.5mass, EC, OC, WSII except Cl- and organic compounds decreased by 16.0 ~ 93.4%, which could be attributed to emission control policy from 2004 to 2013. However, emission factors of most of the metal elements increased significantly, which could be partially attributed to the changes in motor oil additives and vehicle conditions. There are no mandatory national standards to limit metal content from vehicle emissions, which should be a concern of the government. A snapshot of the 2013 characteristic emissions of PM2.5 and its constituents from the on-road vehicular fleet in the PRD region retrieved from our study would be helpful for the assessment of past and future implementations of vehicle emission control policy.

Evidence of Rural and Suburban Sources of Urban Haze Formation in China: A Case Study From the Pearl River Delta Region

“…Filter samples were extracted in ultrapure water (18.2 MΩ) with a centrifuge, sonicated in an ice-water bath, and filtered using a Teflon syringe filter (0.22 μm; Dai et al, 2015). ], and chlorine [Cl À ]) using ion chromatography (883 Basic IC plus, Metrohm, Switzerland).…”

Radiocarbon‐derived source apportionment of fine carbonaceous aerosols before, during, and after the 2014 Asia‐Pacific Economic Cooperation (APEC) summit in Beijing, China

“…The 14 C level of WSOC between the periods before and after APEC is almost the same, although the period after APEC summit was impacted by the coal combustion due to the central heating as we mentioned above. This is because ambient WSOC is a mixture of secondary OC (SOC) and biomass-burning primary OC (POC) that is emitted by biomass burning and fossil fuel combustion barely produces water-soluble POC [Weber et al, 2007;Dai et al, 2015]. Conversely, the contribution of nonfossil sources to WIOC after APEC summit is lower by 15% comparing to other two periods, which also suggests that coal combustion predominantly release the WIOC fraction.…”

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

“…The higher WSOC fraction in OC during summer may be related to biomass burning emissions and SOA formation which produce more WSOC (Ram et al, 2012;Yan et al, 2015). The lower WSOC fractions in OC during winter could be attributed to enhanced emissions from coal combustion and motor vehicles which produce a large fraction of water-insoluble organics (Dai et al, 2015;Daellenbach et al, 2016;Yan et al, 2017). Abs365,MSOC is approximately 2 times (range 1.7-2.3) higher than Abs365,WSOC, which is similar to the results measured in Beijing (Cheng et al, 2016), southeastern Tibetan Plateau (Zhu et al, 2018), Gwangju, Korea (Park et al, 2018) and the Research Triangle Park, USA (Xie et al, 2019), indicating that the optical properties of BrC could be largely underestimated when using water as the extracting solvent.…”