Characterization of peroxyacetyl nitrate (PAN) under different PM2.5 concentration in wintertime at a North China rural site.

As a secondary pollutant of photochemical pollution, peroxyacetyl nitrate (PAN) has attracted a close attention. A four-month campaign was conducted at a rural site in North China Plain (NCP) including the measurement of PAN, O3, NOx, PM2.5, oxygenated volatile organic compounds (OVOCs), photolysis rate constants of NO2 and O3 and meteorological parameters to investigate the wintertime characterization of photochemistry from November 2018 to February 2019. The results showed that the maximum and mean values of PAN were 4.38 and 0.93 ± 0.67 ppbv during the campaign, respectively. The PAN under different PM2.5 concentrations from below 75 µg/m3 up to 250 µg/m3, showed different diurnal variation and formation rate. In the PM2.5 concentration range of above 250 µg/m3, PAN had the largest daily mean value of 0.64 ppbv and the fastest production rate of 0.33 ppbv/hr. From the perspective of PAN's production mechanism, the light intensity and precursors concentrations under different PM2.5 pollution levels indicated that there were sufficient light intensity and high volatile organic compounds (VOCs) and NOx precursors concentration even under severe pollution level to generate a large amount of PAN. Moreover, the bimodal staggering phenomenon of PAN and PM2.5 provided a basis that PAN might aggravate haze through secondary organic aerosols (SOA) formation.

Unexpectedly Increased Particle Emissions from the Steel Industry Determined by Wet/Semidry/Dry Flue Gas Desulfurization Technologies.

"Ultralow-emission" standards have started to be implemented for steel plants in China. Flue gas desulfurization (FGD) systems integrating desulfurization and dedusting, common end-of-pipe technologies before the stacks, have been a key process for controlling the complexity of sintering flue gas to meet ultralow-emission requirements. This study reports comprehensive analysis of the influence of wet/semidry/dry FGD systems on particulate emissions via a field investigation of five typical sinter plants equipped with various FGD devices. The size distribution and mass concentration of particulate matter (PM) are adjusted to different ranges by these FGD systems. Chemical analysis of the PM compositions shows that 20-95% of the mass of inlet PM is removed by FGD systems, while it is estimated that approximately 17, 63, 59, and 71% of the outlet PMs are newly contributed by desulfurizers and their byproducts for the tested wet limestone, wet ammonia, semidry circulating fluidized bed, and activated coke FGD systems, respectively. The newly contributed compositions of PM2.5 emitted from these FGD systems are dominated by CaSO4, (NH4)2SO4, CaSO4 + CaO, and coke carbon, respectively. These results suggest that the deployment of FGD technology should be comprehensively considered to avoid additional negative impacts from byproducts generated in control devices on the atmosphere.

Characteristics and sources of ambient Volatile Organic Compounds (VOCs) at a regional background site, YRD region, China: Significant influence of solvent evaporation during hot months.

Continuous measurement of 98 volatile organic compounds (VOCs) was conducted during 2017-2019 at a regional background site (Shanxi) located at northeast of Zhejiang Province, YRD region, China. The average concentration of total VOCs (TVOCs) was 25.4 ± 18.4 ppbv, and an increasing trend (+12.2 %) was observed. Alkanes were the most abundant VOC group among all seasons, accounting for 43.5 % of TVOCs. Oxygenated VOCs (OVOCs), aromatics, halides and alkenes contributed 15.9 %, 15.7 %, 11.7 % and 10.3 % of TVOCs concentration, respectively. Biogenic VOCs (BVOCs) and OVOCs showed distinguished diurnal cycle from primary anthropogenic VOCs. Photochemical reactivity analysis based on ozone formation potential (OFP) and OH loss rate (LOH) indicated that aromatics and alkenes were the most significant contributor, respectively. Toluene, xylene (m/p- and o-), ethene and propene were the largest contributor of annual OFP, with the mean OFP being 33.8 ± 44.3 µg·m-3, 31.9 ± 32.1 µg·m-3, 9.29 ± 11.4 µg·m-3, 22.1 ± 21.3 µg·m-3 and 12.8 ± 19.5 µg·m-3, respectively. Seven sources were identified with positive matrix factorization (PMF): petrochemical industry (13.8 %), biogenic emission (1.0 %), solvent usage-toluene (16.9 %), vehicular exhaust (43.8 %), Integrated circuits industry (3.8 %), solvent usage-C8 aromatics (10.9 %), and gasoline evaporation (9.8 %). Vehicular exhaust was the most significant source (43.8 %) during the whole measurement period. Solvent usage, petrochemical industry, and gasoline evaporation showed high temperature dependency. The integrated contribution of solvent usage and industrial processes were higher than vehicular exhaust during hot months. These sources also have higher chemical reactivities and can contribute more on O3 formation. Our results are helpful on determining the control strategies aiming at alleviating O3 pollution.

Compositions, sources, and potential health risks of volatile organic compounds in the heavily polluted rural North China Plain during the heating season.

Severe volatile organic compound (VOC) pollution has become an urgent problem during the heating season in the North China Plain (NCP), as exposure to hazardous VOCs can lead to chronic or acute diseases. A campaign with online VOC measurements was conducted at a rural site in Wangdu, NCP during the 2018 heating season to characterize the compositions and associated sources of VOCs and to assess their potential health risks. The total concentration of VOCs with 94 identified species was 77.21 ± 54.39 ppb. Seven source factors were identified by non-negative matrix factorization, including coal combustion (36.1%), LPG usage (21.1%), solvent usage (13.9%), biomass burning and secondary formation (14.2%), background (7.0%), industrial emissions (4.5%), and vehicle emissions (3.3%). The point estimate approach and Monte Carlo simulation were used to estimate the carcinogenic and non-carcinogenic risks of harzadous VOCs. The results showed that the cumulative health risk of VOCs was above the safety level. Acrolein, 1.2-dichloroethane, 1,2-dichloropropane, chloroform, 1,3-butadiene, and benzene were identified as the key hazardous VOCs in Wangdu. Benzene had the highest average carcinogenic risk. Solvent usage and secondary formation were the dominant sources of adverse health effects. During the Spring Festival, most sources were sharply reduced; and VOC concentration declined by 49%. However, coal and biomass consumptions remained relatively large, probably due to heating demand. This study provides important references for the control strategies of VOCs during the heating season in heavily polluted rural areas in the NCP.

Significant impact of coal combustion on VOCs emissions in winter in a North China rural site.

The measurement of volatile organic compounds (VOCs) was carried out using an online GC-FID/MS at a rural site in North China Plain from 1 Nov. 2017 to 21 Jan. 2018. Their concentrations, emission ratios and source apportionment are investigated. During the entire experiment period, the average mixing ratio of VOCs was 69.5 ± 51.9 ppb, among which alkanes contributed the most (37% on average). Eight sources were identified in the non-negative matrix factorization (NMF) model as short-chain alkanes (13.3%), biomass burning (4.6%), solvent (10.8%), industry (3.7%), coal combustion (41.1%), background (4.5%), vehicular emission (7.7%) and secondary formation (14.2%). In addition to the formation of OVOCs through photochemical reactions, the primary sources, such as coal combustion, biomass burning, vehicular emission, solvent and industry, can also contribute to OVOCs emissions. High OVOCs emission ratios thus were observed at Wangdu site. Primary emission was estimated to contribute 50%, 45%, 73%, 77%, 40%, and 29% on average to acrolein, acetone, methylvinylketone (MVK), methylethylketone (MEK), methacrolein and n-hexanal according to NMF analysis, respectively, which was well consistent with the contribution from photochemical age method. Secondary organic aerosol formation potential (SOAFP) was evaluated by SOA yield, which was significantly higher under low-NOx condition (13.4 µg m-3 ppm-1) than that under high-NOx condition (3.2 µg m-3 ppm-1). Moreover, the photochemical reactivity and sources of VOCs showed differences in seven observed pollution episodes. Among, the largest OH loss rate and SOAFP were found in severe pollution plumes, which were induced primarily by coal combustion. Therefore, mitigation strategies for severe pollution formation should focus on reducing coal combustion emitted VOCs that lead to SOA formation.