Source apportionment of fine particulate matter organic carbon in Shenzhen, China by chemical mass balance and radiocarbon methods

Evaluation of a new real-time source apportionment system of PM2.5 and its implication on rapid aging of vehicle exhaust

Accurate identification and rapid analysis of PM2.5 sources and formation mechanisms are essential to mitigate PM2.5 pollution. However, studies were limited in developing a method to apportion sources to the total PM2.5 mass in real-time. In this study, we developed a real-time source apportionment method based on chemical mass balance (CMB) modeling and a mass-closure PM2.5 composition online monitoring system in Shenzhen, China. Results showed that secondary sulfate, secondary organic aerosol (SOA), vehicle emissions and secondary nitrate were the four major PM2.5 sources during autumn 2019 in Shenzhen, together contributed 76 % of PM2.5 mass. The novel method was verified by comparing with other source apportionment methods, including offline filter analysis, aerosol mass spectrometry, and carbon isotopic analysis. The comparison of these methods showed that the new real-time method obtained results generally consistent with the others, and the differences were interpretable and implicative. SOA and vehicle emissions were the major PM2.5 and OA contributors by all methods. Further investigation on the OA sources indicated that vehicle emissions were not only the main source of primary organic aerosol (POA), but also the main contributor to SOA by rapid aging of the exhaust in the atmosphere. Our results demonstrated the great potential of the new real-time source apportionment method for aerosol pollution control and deep understandings on emission sources.

Characteristics and source apportionment of particulate carbon in precipitation based on dual-carbon isotopes (13C and 14C) in Xi'an, China

Wet deposition is a dominant removal pathway of carbonaceous particles from the atmosphere, but few studies have assessed the particulate carbon in precipitation in Chinese cities. To assess the characteristics and sources of particulate carbon, we measured the concentrations, fluxes, stable carbon isotopes, and radiocarbon of particulate carbon, and some cations concentrations in precipitation in Xi'an, China, in 2019. In contrast to rainfall samples, particulate carbon in snowfall samples in Xi'an showed extremely high concentrations and wet deposition fluxes. The concentrations as well as wet deposition fluxes showed no significant (p > 0.05) differences between urban and suburban sites, and they also exhibited low seasonality in rainfall samples. Water-insoluble organic carbon (WIOC) accounted for the majority (∼90%) of the concentrations and wet deposition fluxes of water-insoluble total carbon (WITC) in precipitation. The best estimates of source apportionment of WITC in precipitation showed that biological sources were the main contributor (80.0% ± 10.5%) in summer, and their contributions decreased to 47.3% ± 12.8% in winter. The contribution of vehicle exhaust emissions accounted for 11.7% ± 3.5% in summer and 39.0% ± 4.3% in winter, while the contributions of coal combustion were relatively small in summer (8.3% ± 7.0%) and winter (13.8% ± 8.5%). Biomass burning accounted for 25.7% ± 9.3% and 89.9% ± 0.7% of the biological sources in summer and winter, respectively, with the remainder comprising other sources of contemporary carbon. These results highlight the nonnegligible contributions of biogenic emissions and biomass burning to particulate carbon in precipitation in this city in summer and winter, respectively.

Chemical characterization of particulate organic matter from commercial restaurants: Alkyl PAHs as new tracers for cooking

Cooking is one of the primary sources of particulate organic matter (POM) in urban environments. Numerous experiments have been performed to investigate the composition of POM generated during cooking. However, there still remain substantial uncertainties in our knowledge regarding the emission characteristics of alkyl polycyclic aromatic hydrocarbons (PAHs) from cooking. In addition, previous studies have selected several tracers for Chinese cooking; however, these results were acquired based on observations in the Pearl River Delta region of China, and only four of the eight Chinese cooking styles were tested. Therefore, the organic compositions of the PM_2.5 emitted from four Chinese cooking restaurants in different cities are examined to investigate the emission characteristics of alkyl PAH and to verify whether the selected tracers vary with geographical location and cooking styles. In this study, C1- and C2-phenanthrenes/anthracenes, and C1-pyrenes were detected in the PM_2.5 from the four tested restaurants, but the concentrations of these PAH alkyl homologues were all at low levels, and also much lower than the corresponding parent PAHs. However, the distribution pattern of the alkyl PAHs in the cooking fumes was significantly different from that in the PM from other emission sources. Additionally, some candidate tracers for cooking such as levoglucosan were less influenced by cooking styles or geographical location. Thus, these alkyl PAHs in conjunction with other specific tracers for cooking were utilized to estimate the contribution of cooking to ambient organic carbon. The results showed that the estimates from the chemical mass balance model that includes alkyl PAHs will be higher than the model that does not, and in the case of high alkyl PAHs ambient concentrations, the model that includes alkyl PAHs will provide more reasonable results.

Source-specific contributions of particulate matter to asthma-related pediatric emergency department utilization

Ambient particulate matter smaller than 2.5 μm (PM_2.5) is associated with different chronic diseases. It is crucial to identify the sources of ambient particulate matter to reduce the impact on health. Still, only a few studies have been linked with specific ambient particulate matter sources. In this study, we estimated the contributions of sources of PM_2.5 and examined their association with daily asthma hospital utilization in Cincinnati, Ohio, USA. We used a model-based clustering method to group days with similar source-specific contributions into six distinct clusters. Specifically, elevated PM_2.5 concentrations occurring on days characterized by low coal combustion contributions showed a significantly reduced risk of hospital utilization for asthma (rate ratio: 0.86, 95% CI: [0.77, 0.95]) compared to other clusters. Reducing coal combustion contribution to PM_2.5 levels could be an effective intervention for lowering asthma-related hospital utilization.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13755-021-00141-z.

The 10-Year Study of the Impact of Particulate Matters on Mortality in Two Transit Cities in North-Eastern Poland (PL-PARTICLES)

The detrimental influence of air pollution on mortality has been established in a series of studies. The majority of them were conducted in large, highly polluted cities-there is a lack of studies from small, relatively clean regions. The aim was to analyze the short-term impact of particulate matters (PMs) on mortality in north-eastern Poland. Time-stratified case-crossover design was performed for mortality in years 2008-2017. Daily concentrations of PM_2.5 (28.4 µg/m³, interquartile range (IQR) = 25.2) vs. (12.6 µg/m³, IQR = 9.0) and PM₁₀ (29.0 µg/m³, IQR = 18.0) vs. (21.7 µg/m³, IQR = 14.5) were higher in Łomża than Suwałki (p < 0.001). Impact of PM_2.5 on mortality was recorded in Łomża (odds ratio (OR) for IQR increase 1.061, 1.017-1.105, p = 0.06, lag 0) and Suwałki (OR for IQR increase 1.044, 1.001-1.089, p = 0.004, lag 0). PM₁₀ had an impact on mortality in Łomża (OR for IQR increase 1.028, 1.000-1.058, p = 0.049, lag 1). Cardiovascular mortality was affected by increase of PM_2.5 in Łomża (1.086, 1.020-1.156, p = 0.01) and Suwałki (1.085, 1.005-1.171, p = 0.04). PM_2.5 had an influence on respiratory mortality in Łomża (1.163, 1.021-1.380, p = 0.03, lag 1). In the whole studied region, despite differences in the air quality, the influence of PMs on mortality was observed.

Characteristics and temporal variations of organic and elemental carbon aerosols in PM1 in Changchun, Northeast China

The present study offers the first evaluation of organic and elemental carbon (OC and EC) of submicron (PM₁) fraction in Changchun (Northeast China) during a year-long sampling period (October 24, 2016 to October 23, 2017). More than 288 PM₁ (particulate matter with an aerodynamic diameter of less than 1 μm) samples were collected. The PM₁ concentrations ranged from 3.78 to 451.08 μg·m^-3, with an average of 57.73 μg·m^-3, which was 1.65 times higher than the Chinese National Standard II. Following the concept of the well-known IMPROVE algorithm, OC and EC values were obtained. The OC values ranged from 1.18 to 82.54 μg∙m^-3, and the EC values were from 0.30 to 14.19 μg∙m^-3. Total carbon (TC = EC + OC) constituted 9.11-40.35% of the total PM₁ mass, and OC dominated over EC. The average OC/EC ratio was 4.78, which implied a low percentage for vehicles and a high contribution of coal and biomass consumption to PM₁. Among OC, the annual primary organic carbon (POC) value was 7.69 μg∙m^-3, accounting for 63% of the OC, while secondary organic carbon (SOC) contributed 37% with 4.12 μg∙m^-3. Among EC, CHAR (EC1) dominated over SOOT (EC2 + EC3), and the CHAR/SOOR ratio ranged from 2.91 to 28.55. The results of the OC and EC values as well as the OC/EC and CHAR/SOOT ratios suggest that possible sources of PM₁ include vehicles, coal burning, cooking, and biomass burning.

Estimating Secondary Organic Aerosol Production from Toluene Photochemistry in a Megacity of China

The production of secondary organic aerosols (SOA) from toluene photochemistry in Shanghai, a megacity of China, was estimated by two approaches, the parametrization method and the tracer-based method. The temporal profiles of toluene, together with other fifty-six volatile organic compounds (VOCs), were characterized. Combing with the vapor wall loss corrected SOA yields derived from chamber experiments, the estimated toluene SOA by the parametrization method as embodied in the two-product model contributes up to ∼40% of the total SOA budget during summertime. 2,3-Dihydroxy-4-oxopentanoic acid (DHOPA), a unique product from the OH-initiated oxidation of toluene in the presence of elevated NO_x, was used as a tracer to back calculate the toluene SOA concentrations. By taking account for the effect of gas-particle partitioning processes on the fraction of DHOPA in the particle phase, the estimated toluene SOA concentrations agree within ∼33% with the estimates by the parametrization method. The agreement between these two independent approaches highlight the need to update current model frameworks with recent laboratory advances for a more accurate representation of SOA formation in regions with substantial anthropogenic emissions.

Chemical Composition and Source Apportionment of PM2.5 in Urban Areas of Xiangtan, Central South China

Xiangtan, South China, is characterized by year-round high relative humidity and very low wind speeds. To assess levels of PM_2.5, daily samples were collected from 2016 to 2017 at two urban sites. The mass concentrations of PM_2.5 were in the range of 30–217 µg/m³, with the highest concentrations in winter and the lowest in spring. Major water-soluble ions (WSIIs) and total carbon (TC) accounted for 58–59% and 21–24% of the PM_2.5 mass, respectively. Secondary inorganic ions (SO₄²⁻, NO₃⁻, and NH₄⁺) dominated the WSIIs and accounted for 73% and 74% at the two sites. The concentrations of K, Fe, Al, Sb, Ca, Zn, Mg, Pb, Ba, As, and Mn in the PM_2.5 at the two sites were higher than 40 ng/m³, and decreased in the order of winter > autumn > spring. Enrichment factor analysis indicates that Co, Cu, Zn, As, Se, Cd, Sb, Tl, and Pb mainly originates from anthropogenic sources. Source apportionment analysis showed that secondary inorganic aerosols, vehicle exhaust, coal combustion and secondary aerosols, fugitive dust, industrial emissions, steel industry are the major sources of PM_2.5, contributing 25–27%, 21–22%, 19–21%, 16–18%, 6–9%, and 8–9% to PM_2.5 mass.

Primary biogenic and anthropogenic sources of organic aerosols in Beijing, China: Insights from saccharides and n-alkanes

Sugars and n-alkanes are important organic constituents of atmospheric fine particulate matter (PM_2.5). For better understanding their sources and seasonal variations in urban atmosphere, sugar compounds (anhydrosugars, sugars and sugar alcohols) and homologue n-alkanes (C₁₈-C₃₇) were studied in PM_2.5 samples collected from September 2013 to July 2014 in Beijing, China. In general, all measured compounds showed the lowest levels in summer. Higher concentrations of sugar compounds and n-alkanes were observed in winter, probably due to elevated combustion emissions (e.g., coal, biofuel and agricultural residue burning) and stable meteorological conditions during heating season. Levoglucosan was the major sugar species in all seasons particularly in autumn and winter, highlighting the significant contribution of biomass burning to fine organic aerosols throughout the whole year especially in cold seasons. Plant waxes contributed to n-alkanes the most in late spring (54.5%) and the least in winter (11.6%); while fossil fuel combustion had the largest contribution in winter (385 ng m^-3). The weak odd-carbon predominance of n-alkanes in wintertime aerosols also suggests fossil fuel combustion as the important source of organic aerosols in the heating season. Soil resuspension, fossil fuel combustion and biomass burning, and secondary sources are the main sources of OC in PM_2.5 at Beijing. The seasonal variation in source contributions indicates that meteorological condition is a key factor in controlling PM_2.5 levels. Furthermore, dust storms in spring can strongly enhance the atmospheric level of fine organic matter in Beijing.