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Dust and pollution are frequently mixed together in East Asia, causing large uncertainties in assessing climate change and environmental influence and in relevant policymaking. To discern the dust effect on particle mass, we carried out long-term measurements of the mass and key chemical compositions of PM10, PM2.5, and PM1 from August 2007 to February 2012 and collected hourly data of PM10 and PM2.5 concentrations from January 2012 to October 2020 at Gosan, South Korea. The principal component analysis of measured species reveals two dominant factors, pollution and dust, accounting for 46% and 16% of the total variance, respectively. The mode distribution of PM10, PM2.5, and PM1 mass in addition to the dust events helps to provide a robust criterion of the dust impact. Dust can be identified by the mean + standard deviation (σ) of PM10, while the threshold is down to the mean concentration when dust particles experience precipitation. High PM2.5 concentration also presents dust impact, however, the criterion decreases from mean + σ in 2007–2012 to mean in 2012–2020. It indicates that dust is no longer a high-concentration event of PM2.5, but its influence gradually appears in low-concentration particles. Therefore, the dust criterion obtained from long-term PM10 concentration data is robust, however, the standard is based on PM2.5 changes over time and still needs to be determined by follow-up long-term observations.

International audience; 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.

International audience

The receptor model is an effectively and widely used tool for analyzing the source of PM2.5, and its development and improvement have always been focused and challenged. In this study, approaches of source analysis is applied and compared. The PM2.5 samples were collected in spring of 2015 at a remote background site of Weizhou, South China and were analyzed for water-soluble ions, trace metals, and sugars. The 28 measurement species were introduced into the positive matrix factorization (PMF) and a non-negative matrix factorization (NMF) model for inter-comparison of PM2.5 prediction. Results showed that the NMF model is a more robust tool to identify source types and source apportionment in the case of a small sample size (n = 31). In NMF, four source variants were obtained as dust (15.6%), biomass combustion (11.8%), secondary formation (17.6%), and coal combustion (54.9%), corresponding to four main source areas. These were Southeast Asia, South China Sea, Taiwan Strait, as well as Pearl River Delta, respectively. The areas were distinguished based on hybrid receptor models, potential source contribution function (PSCF) and concentration weighted trajectory (CWT), by introducing the daily loadings of each source factor from NMF method. These model results were highly consistent with categorized chemical characteristics of PM2.5, suggesting that NMF linking with hybrid receptor models provides valuable implications for exploring source types and source areas of PM2.5. Meanwhile, biomass combustion and coal combustion comparably contributed to the high PM2.5 concentrations indicating control strategy in South China in spring.

Based on source-specific saccharide tracers, the characteristic of biomass burning (BB) and biogenic emissions to saccharides was investigated in three rural sites at Lincang, where covered with 65 % of forest in the southwest border of China. The total saccharides accounted for 8.4 ± 2.7 % of OC, and 1.6 ± 0.6 % of PM2.5. The measured anhydrosugars accounted for 48.5 % of total saccharides, among which levoglucosan was the most dominant species. The high level of levoglucosan was both attributed to the local BB activities and biomass combustion smoke transported from the neighboring regions of Southeast Asia (Myanmar) and the northern Indian Peninsula. The measured mono (di) saccharides and sugar alcohols accounted for 24.9 ± 8.3 % and 26.6 ± 9.9 % of the total saccharides, respectively, were both proved to be mostly emitted by direct biogenic volatilization from plant materials/surface soils, rather than as byproducts of polysaccharides breakdown during BB processes. Five sources of saccharides were resolved by non-negative matrix factorization (NMF) analysis, including BB, soil microbiota, plant senescence, airborne pollen and plant detritus with the contribution of 34.0 %, 16.0 %, 21.0 %, 23.7 % and 5.3 %, respectively. The results provide the information on the magnitude of levoglucosan and contributions of BB, as well as the characteristic of biogenic saccharides, at the remote sites of Southwest China, which can be further applied to regional source apportionment models and global climate models.

Over the past few decades, northeast Asia has suffered from the extreme levels of PM2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 μm). Despite extensive efforts and the scientific advances in understanding PM2.5 pollution, the fundamental mechanisms responsible for the occurrence of high PM2.5 concentrations have not been comprehensively understood. In this study, we investigated the physical and chemical drivers for the formation and transformation of atmospheric particles using a four-year dataset of nanoparticle number size distributions, PM2.5 chemical composition, gaseous precursors, and meteorological variables in northeast Asia outflows. The empirical orthogonal function (EOF) analyses of size-separated particle numbers extracted two modes representing a burst of nanoparticles (EOF1) and an increase in PM2.5 mass (EOF2) associated with persistent anticyclone and synoptic-scale stagnation, respectively. The vertical structure of the particles demonstrated that the synoptic conditions also affected the daily evolution of boundary layer, promoting either the formation of nanoparticles through deep mixing or conversion into accumulation-mode particles in shallow mixed layers. In the haze-development episode equivalent to EOF2 during the KORUS-AQ (KORea-US Air Quality) campaign, the PM2.5 mass reached 63 μg m−3 with the highest contribution from inorganic constituents, which was accompanied by a thick coating of refractory black carbon (rBC) that linearly increased with condensation-mode particles. This observational evidence suggests that the thick coating of rBC resulted from an active conversion of condensable gases into particle-phase on the BC surface, thereby increasing the mass of the accumulation-mode aerosol. Consequently, this result complies with the strategy to reduce black carbon as a way to effectively mitigate haze pollution as well as climate change in northeast Asia.

Commodity plastic is ubiquitous in daily life and commonly disposed of via unregulated burning, particularly in developing regions. We report here the much higher emission factors (13.1 ± 7.5 g/kg) and toxicities of inhalable aerosols emitted from the unregulated burning of plastic waste based on field measurements and cellular experiments, including oxidative stress and cytotoxic tests in A549 cells. Plastic foam burning emitted aerosols possesses the highest EFs (34.8 ± 4.5 g/kg) and toxicities, which are 4.2- to 13.4-fold and 1.1- to 2.7-fold higher than those emitted from the burning of other waste types. These quantified toxicities are mainly attributed to aerosols containing carbonaceous matter, especially persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins, which originate from incomplete combustion processes. The aerosol emission amounts were estimated from the obtained experimental results. Approximately 70.2 million tons (29%) of plastic waste was burned without regulation worldwide in 2016, leading to 0.92 ± 0.53 million tons of toxic aerosols being released into the air, a majority of which occurred in developing regions. The results indicate improved combustion technology and control strategies are urgently needed in developing regions for discarded plastic -waste to mitigate toxic exposure risks and achieve sustainable development.

In this study, pot-culture experiments were conducted to investigate the single effect of Cd, PCBs, and the combined effect of Cd-PCBs with Tagetes patula L. The study highlights that the minimum concentration of PCBs (100 µg kg−1) could enable the growth of the plant with an increase in biomass by 27.76% when compared with the control. In all the experiments performed, the Cd concentrations over the surface parts were found to be above 100 mg kg−1. Significant positive correlations were observed between the Cd and PCBs concentrations accumulated in tissues of the soil and plants (p

For PM2.5 filter samples collected daily at the Chinese Research Academy of Environmental Sciences (Beijing, China) from December of 2013 to February of 2014 (the winter period), chemical characteristics and sources were investigated with an emphasis on haze events in different alert levels. During the 3 months, the average PM2.5 concentration was 89 µg m−3, exceeding the Chinese national standard of 75 µg m−3 in 24  h. The maximum PM2.5 concentration was 307 µg m−3, which characterizes developed-type pollution (PM2.5 / PM10>0.5) in the World Health Organization criteria. PM2.5 was dominated by SO42−, NO3−, and pseudo-carbonaceous compounds with obvious differences in concentrations and proportions between non-haze and haze episodes. The non-negative matrix factorization (NMF) analysis provided reasonable PM2.5 source profiles, by which five sources were identified: soil dust, traffic emission, biomass combustion, industrial emission, and coal combustion accounting for 13, 22, 12, 28, and 25  % of the total, respectively. The dust impact increased with northwesterlies during non-haze periods and decreased under stagnant conditions during haze periods. A blue alert of heavy air pollution was characterized by the greatest contribution from industrial emissions (61  %). During the Chinese Lantern Festival, an orange alert was issued and biomass combustion was found to be the major source owing to firework explosions. Red-alert haze was almost equally contributed by local traffic and transported coal combustion emissions from the vicinity of Beijing (approximately 40  % each) that was distinguished by the highest levels of NO3− and SO42−, respectively. This study also reveals that the severity and source of haze are largely dependent on meteorological conditions.

Measuring isotopic ratios in aerosol particles is a powerful tool for identifying major sources, particularly in separating fossil from non-fossil sources and investigating aerosol formation processes. We measured the radiocarbon, stable carbon, and stable nitrogen isotopic composition of PM2.5 in Beijing (BJ) and Changdao (CD) in the North China Plain (NCP) from May to mid-June 2016. The mean PM2.5 concentrations were 48.6 ± 28.2 μg m−3 and 71.2 ± 29.0 μg m−3 in BJ and CD, respectively, with a high contribution (∼66%) from secondary inorganic aerosol (SIA; NO3−, NH4+, and SO42−). The mean δ13C of total carbon (TC) and δ15N of total nitrogen (TN) values differed significantly between the two sites (p-value of

The North China Plain (NCP) is the most heavily polluted region in China and the explosive growth (EG) events of PM2.5 frequently occur in winter in this region. A campaign from 17 Nov. 2018 to 1 Mar. 2019 was conducted at a rural site in NCP. EG events of PM2.5 were defined as the dynamic increase in PM2.5 concentration by 100 μg/m3 within half day. The intensity of EG events were then graded by the time cost, i.e. 3, 6 and 9 h. EG events with a total number of 120 were identified during the study. Mean growth rates and corresponding standard deviations of PM2.5 of 3 h-, 6 h- and 9 h-EG events were 43.4 ± 6.9, 19.3 ± 1.8 and 12.5 ± 0.5 μg/m3/h, respectively. All of them except one 3 h-EG event occurred with windspeed lower than 2 m/s. Based on the evolution of hourly chemical composition of PM2.5, the EG events were investigated on their formation mechanism. The average mass fraction ratios of SNA (sulphate, SO42−; nitrate, NO3−; ammonium, NH4+) in PM2.5 were 26.3%/18.7%, 32.6%/18.0% and 33.6%/26.9% in 3 h-, 6 h- and 9 h-EG events in the daytime/nighttime, respectively. About two thirds of EG events occurred in the nighttime with a significant increase in the concentrations of organic matter (OM) and chloride (Cl−), which is attributable to nocturnal primary emissions such as coal combustion. In addition, CO-scaled growth rate was calculated as chemical growth rate, the results indicate that OM was the dominant components in EG events.

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.

In East Asia, soil dust is a major component of aerosols and is mixed with various pollutants during transport, resulting in large uncertainty in climate and environmental impact assessment and relevant policymaking. To diagnose the influence of soil dust and anthropogenic pollution on bulk aerosol, we conducted long-term measurements of mass, water-soluble ions, and carbonaceous compounds of PM10, PM2.5, and PM1 at Gosan Climate Observatory, South Korea, from August 2007 to February 2012. The principle component analyses of all measured species reveal that the impact of anthropogenic pollution, soil dust, and agricultural fertilizer accounts for 46 %, 16 %, and 9 % of the total variance, respectively. Particularly, the loadings of agricultural component were high in the warmer months with the least occurrence of high concentration events and have increased over time. In mode analysis of PM10, PM2.5, and PM1 mass concentrations, the mean + σ was comparable to the 90th percentile and thus, suggested as a robust criterion that determines the substantial impact of soil dust and haze pollution on particulate matter. The results of this study imply that non-combustion sources such as soil dust will impose constraints to the reduction of PM2.5 as well as PM10 concentrations. In addition, questions are raised as to whether the yearly average concentration is suitable for environmental standard in northeast Asian region.