Emission of Intermediate Volatile Organic Compounds from Animal Dung and Coal Combustion and Its Contribution to Secondary Organic Aerosol Formation in Qinghai-Tibet Plateau, China.

Intermediate volatility organic compounds (IVOCs) are important precursors to secondary organic aerosols (SOAs), but they are often neglected in studies concerning SOA formation. This study addresses the significant issue of IVOCs emissions in the Qinghai-Tibetan plateau (QTP), where solid fuels are extensively used under incomplete combustion conditions for residential heating and cooking. Our field measurement data revealed an emission factor of the total IVOCs (EFIVOCs) ranging from 1.56 ± 0.03 to 9.97 ± 3.22 g/kg from various combustion scenarios in QTP. The markedly higher EFIVOCs in QTP than in plain regions can be attributed to oxygen-deficient conditions. IVOCs were dominated by gaseous phase emissions, and the primary contributors of gaseous and particulate phase IVOCs are the unresolved complex mixture and alkanes, respectively. Total IVOCs emissions during the heating and nonheating seasons in QTP were estimated to be 31.7 ± 13.8 and 6.87 ± 0.45 Gg, respectively. The estimated SOA production resulting from combined emissions of IVOCs and VOCs is nearly five times higher than that derived from VOCs alone. Results from this study emphasized the pivotal role of IVOCs emissions in air pollution and provided a foundation for compiling emission inventories related to solid fuel combustion and developing pollution prevention strategies.

A review on advancements in atmospheric microplastics research: The pivotal role of machine learning.

Microplastics (MPs), recognized as emerging pollutants, pose significant potential impacts on the environment and human health. The investigation into atmospheric MPs is nascent due to the absence of effective characterization methods, leaving their concentration, distribution, sources, and impacts on human health largely undefined with evidence still emerging. This review compiles the latest literature on the sources, distribution, environmental behaviors, and toxicological effects of atmospheric MPs. It delves into the methodologies for source identification, distribution patterns, and the contemporary approaches to assess the toxicological effects of atmospheric MPs. Significantly, this review emphasizes the role of Machine Learning (ML) and Artificial Intelligence (AI) technologies as novel and promising tools in enhancing the precision and depth of research into atmospheric MPs, including but not limited to the spatiotemporal dynamics, source apportionment, and potential health impacts of atmospheric MPs. The integration of these advanced technologies facilitates a more nuanced understanding of MPs' behavior and effects, marking a pivotal advancement in the field. This review aims to deliver an in-depth view of atmospheric MPs, enhancing knowledge and awareness of their environmental and human health impacts. It calls upon scholars to focus on the research of atmospheric MPs based on new technologies of ML and AI, improving the database as well as offering fresh perspectives on this critical issue.

Nitroaromatic compounds in six major Chinese cities: Influence of different formation mechanisms on light absorption properties.

Nitroaromatic compounds (NACs) are important nitrogen organics in aerosol with strong light-absorbing and chemically reactive properties. In this study, NACs in six Chinese megacities, including Harbin (HB), Beijing (BJ), Xi'an (XA), Wuhan (WH), Chengdu (CD), and Guangzhou (GZ), were investigated for understanding their sources, gas-particle partitioning, and impact on BrC absorption properties. The concentrations of ΣNACs in PM2.5 in the six cities ranged from 9.15 to 158.8 ng/m3 in winter and from 2.02 to 9.39 ng/m3 in summer. Nitro catechols (NCs), nitro phenols (NPs), and nitro salicylic acids (NSAs) are the main components in ΣNACs, with NCs being dominant in particulate phase and NPs being dominant in the gas phase. Correlation analysis between different pollutant species revealed that coal and biomass combustions were the major sources of NACs in the northern cities during wintertime, while secondary formation dominated NACs in the southern cities during summertime. The contribution of ΣNACs to brown carbon (BrC) light absorption ranged from 0.85 to 7.98 % during the wintertime and 2.07-6.44 % during the summertime. The mass absorption efficiency at 365 nm (MAE365) were highest for 4-nitrocatechol (4NC, 17.4-89.0 m2/g), 4-methyl-5-nitrocatechol (4M5NC, 15.0-76.9 m2/g), and 4-nitroguaiacol (4NG, 11.7-59.8 m2/g). The formation of NCs and NG through oxidation and nitration of catechol and guaiacol led to a significant increase in aerosol light absorption. In contrast, NPs and NSAs formed by the photonitration and photooxidation in liquid phase showed high polarity but low light absorption ability, and the proportions of (NPs + NSAs) in the light absorption of ΣNACs were lower than 15.3 % in the six megacities.

Chronic exposure to PM10 induces anxiety-like behavior via exacerbating hippocampal oxidative stress.

As one of the most environmental concerns, inhaled particulate matter (PM10) causes numerous health problems. However, the associations between anxiety behavior and toxicity caused by PM10 have rarely been reported so far. To investigate the changes of behavior after PM10 exposure and to identify the potential mechanisms of toxicity, PM10 samples (with doses of 15 mg/kg and 30 mg/kg) were intratracheally instilled into rats to simulate inhalation of polluted air by the lungs. After instillation for eight weeks, anxiety-like behavior was evaluated, levels of oxidative stress and morphological changes of hippocampus were measured. The behavioral results indicated that PM10 exposure induced obvious anxiety-like behavior in the open field and elevated plus maze tests. Both PM10 concentrations tested could increase whole blood viscosity and trigger hippocampal neuronal damage and oxidative stress by increasing superoxide dismutase (SOD) activities and malondialdehyde levels, and decreasing the expressions of antioxidant-related proteins (e.g., nuclear factor erythroid 2-related factor 2 (Nrf2), SOD1 and heme oxygenase 1). Furthermore, through collecting and analyzing questionnaires, the data showed that the participants experienced obvious anxiety-related emotions and negative somatic responses under heavily polluted environments, especially PM10 being the main pollutant. These results show that PM10 exposure induces anxiety-like behavior, which may be related to suppressing the Nrf2/Keap1-SOD1 pathway.

Internal exposure potential of water-soluble organic molecules in urban PM2.5 evaluated by non-covalent adductome of human serum albumin.

Water-soluble organic molecules (WSOMs) in inhaled PM2.5 can readily translocate from the lungs into the blood circulation, facilitating their distribution to and health effects on distant organs and tissues in the human body. Human serum albumin (HSA), the most abundant protein carrier in the blood, readily binds exogenous substances to form non-covalent adducts and subsequently transports them throughout the circulatory system, thereby indicating their internal exposure. The direct internal exposure of WSOMs in PM2.5 needs to be understood. In this study, the non-covalent HSA-WSOM adductome was developed as a dosimeter to evaluate the internal exposure potential of WSOMs in urban PM2.5. The WSOM composition was acquired from non-target high-resolution mass spectrometry analysis coupled with multiple ionizations. The binding level of HSA-WSOM non-covalent adducts was obtained from surface plasma resonance. Machine learning combined WSOM composition and the binding level of HSA-WSOM non-covalent adducts to screen bindable (also internalizable) WSOMs. The concentration of WSOM ranged from 4 to 13 µg/m3 during our observation period. Of the 17,513 mass spectral features detected, 9,484 contributed to the non-covalent adductome and possessed the internal exposure potential. 102 major contributors accounted for 90.6 % of the HSA-WSOM binding level. The fraction of internalizable WSOMs in PM2.5 varied from 11.9 % to 61.3 %, averaging 26.2 %. WSOMs that have internal exposure potential were primarily lignin-like and lipid-like substances. The HSA-WSOMs non-covalent adductome represents direct internal exposure potential, which can provide crucial insights into the molecular diagnosis of PM2.5 exposure and precise assessments of PM2.5 health effects.

Toxicity source apportionment of fugitive dust PM2.5-bound polycyclic aromatic hydrocarbons using multilayer perceptron neural network analysis in Guanzhong Plain urban agglomeration, China.

Polycyclic aromatic hydrocarbons (PAHs) in urban fugitive dust, known for their toxicity and ability to generate reactive oxygen species (ROS), are a major public health concern. This study assessed the spatial distribution and health risks of 15 PAHs in construction dust (CD) and road dust (RD) samples collected from June to November 2021 over the cities of Tongchuan (TC), Baoji (BJ), Xianyang (XY), and Xi'an (XA) in the Guanzhong Plain, China. The average concentration of ΣPAHs in RD was 39.5 ± 20.0 µg g-1, approximately twice as much as in CD. Four-ring PAHs from fossil fuels combustion accounted for the highest proportion of ΣPAHs in fugitive dust over all four cities. Health-related indicators including benzo(a)pyrene toxic equivalency factors (BAPTEQ), oxidative potential (OP), and incremental lifetime cancer risk (ILCR) all presented higher risk in RD than those in CD. The multilayer perceptron neural network algorithm quantified that vehicular and industrial emissions contributed 86 % and 61 % to RD and CD BAPTEQ, respectively. For OP, the sources of biomass and coal combustion were the key generator which accounted for 31-54 %. These findings provide scientific evidence for the direct efforts toward decreasing the health risks of fugitive dust in Guanzhong Plain urban agglomeration, China.

Insight into the Role of NH3/NH4+ and NOx/NO3- in the Formation of Nitrogen-Containing Brown Carbon in Chinese Megacities.

Particulate brown carbon (BrC) plays a crucial role in the global radiative balance due to its ability to absorb light. However, the effect of molecular formation on the light absorption properties of BrC remains poorly understood. In this study, atmospheric BrC samples collected from six Chinese megacities in winter and summer were characterized through ultrahigh-performance liquid chromatography coupled with Orbitrap mass spectrometry (UHPLC-Orbitrap MS) and light absorption measurements. The average values of BrC light absorption coefficient at a wavelength of 365 nm (babs365) in winter were approximately 4.0 times higher than those in summer. Nitrogen-containing organic molecules (CHNO) were identified as critical components of light-absorbing substances in both seasons, underscoring the importance of N-addition in BrC. These nitrogen-containing BrC chromophores were more closely related to nitro-containing compounds originating from biomass burning and nitrogen oxides (NOx)/nitrate (NO3-) reactions in winter. In summer, they were related to reduced N-containing compounds formed in ammonia (NH3)/ammonium (NH4+) reactions. The NH3/NH4+-mediated reactions contributed more to secondary BrC in summer than winter, particularly in southern cities. Compared with winter, the higher O/Cw, lower molecule conjugation indicator (double bond equivalent, DBE), and reduced BrC babs365 in summer suggest a possible bleaching mechanism during the oxidation process. These findings strengthen the connection between molecular composition and the light-absorbing properties of BrC, providing insights into the formation mechanisms of BrC chromophores across northern and southern Chinese cities in different seasons.

Exploration and comparison of the relationship between PAHs and ROS in PM2.5 emitted from multiple anthropogenic sources in the Guanzhong Plain, China.

Anthropogenic emissions have emerged as an important source of urban atmospheric PM2.5, exacerbating air pollution and the associated health implications. This study analyses PM2.5, originating from major anthropogenic sources (industries, motor vehicles, and solid-fuel combustion for domestic applications) in the Guanzhong Plain in China, along with the parent- (p-), alkylated- (a-), and oxygenated- (o-) polycyclic aromatic hydrocarbons (PAHs) and reactive oxygen species (ROS) levels in PM2.5. Industrial emissions are mainly characterised by high abundances of benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), and benz[a]fluoranthene (BaF). The 4-ring p-PAHs, such as fluoranthene (FLA), pyrene (PYR), benzo[a]anthracene (BaA), and chrysene (CHR) proportions and the diagnostic ratios of indeno[1,2,3-cd]pyrene (IcdP)/[IcdP + benzo[ghi]perylene (BghiP)] and 1-acenaphthenone (1ACO)/[1ACO + 9-fluorenone (9FO)] in motor vehicle emission PM2.5 were higher than the other sources. Household solid fuel combustion features high proportions of methylnaphthalene (M-NAP), i.e., 2 M-NAP and 1 M-NAP and 3-ring p-PAHs. Acenaphthylene (ACY), acenaphthene (ACE), anthracene (ANT), 1,4-chrysenequinone (1,4CHRQ), and reactive oxygen species (ROS) were positively correlated among the three anthropogenic sources. Moreover, the correlations between other PAHs and ROS varied significantly among the three sources. As mixed and compound organic pollutants, 2- and 3-ring p-PAHs were more positively correlated with the ROS activity of household solid fuel combustion sources compared with industrial and motor vehicle sources. Based on the relative contribution of these three sources to PAHs in PM2.5, we estimated the cancer risks of males and females in the Guanzhong area to be 2.95 × 10-6 and 2.87 × 10-6, respectively, exceeding the safety threshold of 1 × 10-6. This study provides a basic dataset for conducting a refined source apportionment of PM2.5 and a scientific basis for further understanding the relationship between PM2.5, PAHs, and ROS in northern China.

The impacts of regional transport on anthropogenic source contributions of PM2.5 in a basin city, China.

PM2.5 pollution events are often happened in urban agglomeration locates in mountain-basin regions due to the complex terra and intensive emissions. Source apportionment is essential for identifying the pollution sources and important for developing local mitigation strategies, however, it is influenced by regional transport. To understand how the regional transport influences the atmospheric environment of a basin, we connected the PM2.5 source contributions estimated by observation-based receptor source apportionment and the regional contributions estimated by a tagging technology in the comprehensive air quality model with extensions (CAMx) via an artificial neural network (ANNs). The result shows that the PM2.5 in Xi'an was from biomass burning, coal combustion, traffic related emissions, mineral dust, industrial emissions, secondary nitrate and sulfate. 48.8 % of the PM2.5 in study period was from Xi'an, then followed by the outside area of Guanzhong basin (28.2 %), Xianyang (14.6 %) and Weinan (5.8 %). Baoji and Tongchuan contributed trivial amount. The sensitivity analysis showed that the transported PM2.5 would lead to divergent results of source contributions at Xi'an. The transported PM2.5 from the outside has great a potential to alter the source contributions implying a large uncertainty of the source apportionment introduced when long-range transported pollutants arrived. It suggests that a full comprehension on the impacts of regional transport can lower the uncertainty of the local PM2.5 source apportionment and reginal collaborative actions can be of great use for pollution mitigation.

Insight into personal exposure characteristics and health effects of PM2.5 and PM0.25-bound PAHs and their derivatives with different heating ways in the Fenwei Plain, China.

Personal exposure (PE) to polycyclic aromatic hydrocarbons (PAHs) and their derivatives in particulate matter with two aerodynamic sizes of 2.5 and 0.25 µm (PM2.5 and PM0.25) from rural housewives was studied in the Fenwei Plain, China. A total of 15 households were divided into five different groups based on the type of solid fuel and heating device used, including biomass briquette-furnace (BBF), biomass-elevated Kang (BEK), outdoor lump coal-boiler (OLC), indoor briquette coal-stove (IBC), and electricity (ELE). The PE concentrations of the PAHs and biomarkers in urine collected from the participants were determined. The results showed that the PE concentrations of total quantified PAHs in the biomass group (i.e., BBF and BEK) were 2.2 and 2.0 times higher than those in the coal groups (i.e., OLC and IBC) in PM2.5 and PM0.25, respectively. The housewives who used biomass as fuel suffered from higher potential health impacts than the coal fuel users. The incremental lifetime cancer risk for the PAHs in PM2.5 in the BBF and BEK groups exceeded the international safety threshold. Furthermore, the PE concentrations of oxygenated PAH (o-PAHs) in PM2.5 and PM0.25 in the biomass groups and the nitrated PAHs (n-PAHs) in PM0.25 in the coal groups showed strong correlations with the biomarkers. The results of this study proved the associations between exposure to the different classes of PAHs and health hazards. The findings could also serve as a guideline in establishing efficient measures for using solid fuels for cooking and household warming in northern China.

Insight into the Primary and Secondary Particle-Bound Methoxyphenols and Nitroaromatic Compound Emissions from Solid Fuel Combustion and the Updated Source Tracers.

Methoxyphenols and nitroaromatic compounds (NACs) have strong atmospheric radiative forcing effects and adverse effects on human health. They are emitted from the incomplete combustion of solid fuels and are secondarily formed through photochemical reactions. Here, an on-site study was conducted to determine the primary emission and secondary formation of particulate phase products from a variety of solid fuels through a potential aerosol mass-oxidation flow reactor. Emission factors for total quantified methoxyphenols and NACs (i.e., EF∑Methoxyphenols and EF∑NACs) varied by 2 orders of magnitude among different fuels, which were greatly influenced by volatile matter, incomplete combustibility, flame intensity, and combustion temperature. Guaiacol and 4-nitro-2-vinylphenol were used as tracers for primary organic aerosol due to the low aged-to-fresh ratios (0.21-0.97), while 4-methyl-guaiacol, 4-ethyl-guaiacol, eugenol, 4-methyl-syringol, isoeugenol, acetovanillone, syringaldehyde, homovanillin acid, vanillin acid, and syringic acid were identified as secondary organic aerosol (SOA) (aged-to-fresh ratios between 1.90 and 4.20). During simulated aging, the -CHO group reacted with the hydroxyl radical (•OH) to form the -COOH group, but there was no correlation between syringol and 4-nitrosyringol, implying that •OH is the main reactant rather than the nitriate radical (•NO3) in the atmospheric aging processes of methoxyphenols. Aging caused substantially different emission profiles due to variable photochemical reaction properties. The fresh EFs for guaiacol emitted from the biomass burning ranged from 3.80 ± 0.44 to 26.2 ± 5.40 mg·kg-1, which were much higher than those in coal combustions (of 0.03 ± 0.01 to 1.42 ± 0.28 mg·kg-1). However, the aged EFs (EFaged) for guaiacol was 1.02 ± 0.06 to 1.61 ± 0.11 mg·kg-1 in most biomass combustions, which were comparable with those of the bituminous chunk (1.20 ± 0.16 mg·kg-1). Therefore, guaiacol, a traditional biomass marker, is not an ideal tracer for aged PM2.5 emitted from biomass burning. Indeed, the syringol/guaiacol and syringol/4-nitrosyringol ratios were found to be more suitable and efficient to be used in source characterization.

Characterization and Risk Assessment of PM2.5-Bound Polycyclic Aromatic Hydrocarbons and their Derivatives Emitted from a Typical Pesticide Factory in China.

Polycyclic aromatic hydrocarbons (PAHs) and their derivatives have received extensive attention due to their negative effects on the environment and on human health. However, few studies have performed comprehensive assessments of PAHs emitted from pesticide factories. This study assessed the concentration, composition, and health risk of 52 PM2.5-bound PAHs during the daytime and nighttime in the vicinity of a typical pesticide factory. The total concentration of 52 PAHs (Σ52PAHs) ranged from 53.04 to 663.55 ng/m3. No significant differences were observed between daytime and nighttime PAH concentrations. The average concentrations of twenty-two parent PAHs, seven alkylated PAHs, ten oxygenated PAHs, and twelve nitrated PAHs were 112.55 ± 89.69, 18.05 ± 13.76, 66.13 ± 54.79, and 3.90 ± 2.24 ng/m3, respectively. A higher proportion of high-molecular-weight (4-5 rings) PAHs than low-molecular-weight (2-3 rings) PAHs was observed. This was likely due to the high-temperature combustion of fuels. Analysis of diagnostic ratios indicated that the PAHs were likely derived from coal combustion and mixed sources. The total carcinogenic equivalent toxicity ranged from 15.93 to 181.27 ng/m3. The incremental lifetime cancer risk from inhalation, ingestion, and dermal contact with the PAHs was 2.33 × 10-3 for men and 2.53 × 10-3 for women, and the loss of life expectancy due to the PAHs was 11,915 min (about 0.023 year) for men and 12,952 min (about 0.025 year) for women. These results suggest that long-term exposure to PM2.5 emissions from a pesticide factory has significant adverse effects on health. The study results support implementing the characterization of PAH emissions from pesticide factories and provides a scientific basis for optimizing the living environment around pesticide factories.

County-level and monthly resolution multi-pollutant emission inventory for residential solid fuel burning in Fenwei Plain, China.

The Fenwei Plain (FWP) in central China is the fourth largest plain nationwide. This region has experienced severe air pollution during the past decades, largely due to residential solid fuel burning. A regional-scale emission inventory covering multi-pollutants was currently unavailable for this area due to the lack of localized emission factors (EFs) from various sources. In this study, localized EFs derived from previous in situ measurements and detailed county-level activity data were used to develop an emission inventory of particulate and gaseous pollutants for the source sector of five residential solid fuels in the FWP in 2020. Emissions of particulate matter with an aerodynamic diameter of ≤2.5 µm (PM2.5), organic carbon (OC), elemental carbon (EC), ions, polycyclic aromatic hydrocarbons (PAHs), carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), and volatile organic compounds (VOCs) were estimated to be 230-290, 89-160, 20-29, 31-54, 0.93-22, 2100-3600, 64-87, 9.3-12, and 45-92 Gg/yr, respectively. The county-level distribution characteristics differed between pollutant species due to their different EFs and consumption patterns of solid fuels. Shouyang County emitted most for all pollutants (2.66%-4.91% of the region total) except PM2.5 and SO2, for which Xiangfen and Hongtong County emitted the most (2.64% and 2.90%), respectively. Emissions were higher in cold (SO2 during November to January, other pollutants during November to February) than warm months. Uncertainties in this newly developed emission inventory were estimated to be 25.2%-69.8%, much lower than those of existing ones, demonstrating the reliability of this inventory. Gini coefficients indicated that EC, PAHs, NOx, and VOC emissions exhibited evident regional disparities, e.g., Yuncheng and Jinzhong had high pollution levels despite low economic output. Future emission control policies should first focus on developing regions with high pollution in FWP.

Chemical composition and potential health risks of tire and road wear microplastics from light-duty vehicles in an urban tunnel in China.

Tire and road wear microplastics (TRWMPs) are one of the main non-exhaust pollutants of motor vehicles, which cause serious environmental and health issues. Here, TRWMPs in PM2.5 samples were collected in a tunnel in urban Xi'an, northwest China, during four periods [I: 7:30-10:30, II: 11:00-14:00, III: 16:30-19:30, IV: 20:00-23:00 local standard time (LST)] in summer of 2019. The chemical components of rubbers, benzothiazoles, phthalates, and amines in TRWMPs were quantified, with a total concentration of 6522 ± 1455 ng m-3 (mean ± standard deviation). Phthalates were predominant in TRWMPs, accounting for 64.8% on average, followed by rubbers (33.2%) and benzothiazoles (1.19%). The diurnal variations of TRWMPs showed the highest concentration in Period III (evening rush hour) and the lowest concentration in Period I (morning rush hour), which were not exactly consistent with the variation of the number of light-duty vehicles passed through the tunnel. The result implied that the number of vehicles might not be the most important contributor to TRWMPs concentration, whereas meteorological variables (i.e., precipitation, and relative humidity), vehicle speed, vehicle class, and road cleaning also affected their abundances. The non-carcinogenic risk of TRWMPs in this study was within the international safety threshold, but their carcinogenic risk exceeded the threshold by 2.7-4.6 times, mostly dominated by bis(2-ethylhexyl)phthalate (DEHP). This study provides a new basis for the source apportionment of urban PM2.5 in China. The high concentrations and high potential cancer risks of TRWMPs represent the requirement for more efficient measures to control light-duty vehicle emissions.

Examination of long-time aging process on volatile organic compounds emitted from solid fuel combustion in a rural area of China.

Volatile organic compounds (VOCs) emitted from solid fuels combustion (e.g., biomass and coal) are still the dominant precursors for the formation of tropospheric ozone (O3) and secondary organic aerosols (SOAs). Limited research focused on the evolution, as known as atmospheric aging, of VOCs emitted during long-timescale observations. Here, freshly emitted and aged VOCs from common residual solid fuel combustions were collected onto absorption tubes before and after passing through an oxidation flow reactor (OFR) system, respectively. The emission factor (EF) of freshly emitted total VOCs is in descending order of corn cob ≥ corn straw > firewood ≥ wheat straw > coals. Aromatic and oxygenated VOCs (OVOCs) are the two most abundant groups, accounting for >80% of the EF of total quantified VOCs (EFTVOCs). Briquette technology shows an effective reduction of the VOC emission, demonstrating a maximum 90.7% lower EFTVOCs in comparison to that of biomass fuels. In contrast, each VOC shows significantly different degradation in comparison to EF of freshly emitted and after 6- and 12-equivalent day aging (actual atmospheric aging days calculated from aging simulation). The largest degradations after 6-equivalent days of aging are observed on alkenes in the biomass group (60.9% on average) and aromatics in the coal group (50.6% on average), consistent with their relatively high reactivities toward oxidation with O3 and hydroxyl radical. The largest degraded compound is seen for acetone, followed by acrolein, benzene, and toluene. Furthermore, the results show that the distinction of VOC species based on long-timescale (12-equivalent day aging) observation is essential to further explore the effect of regional transport. The alkanes which have relatively lower reactivities but high EFs could be accumulated through long-distance transport. These results provide detailed data on fresh and aged VOCs emitted from residential fuels which could be used to explore the atmospheric reaction mechanism.

Environmental and health impacts of household energy conversion on PAHs and their derivatives in PM2.5 in typical areas of northern China.

Heavy use of solid fuels in rural households of northern China emits huge amounts of fine particulate matter (i.e., PM2.5) that pose notable indoor air pollution and severe inhalation health risks. In this study, the environmental and health benefits of clean energy substitution were accessed by monitoring indoor and personal exposure to polycyclic aromatic hydrocarbons (PAHs) and their derivatives, and pulmonary function and biological parameters. After substitutions of traditional lump coal and biomass fuels by clean coal, indoor concentrations of parent PAHs (p-PAHs), alkylated PAHs (a-PAHs), oxygenated PAHs (o-PAHs), and nitro PAHs (n-PAHs) reduced by 71 %, 32 %, 70 %, and 76 %, while personal exposure concentrations decreased by 82 %, 87 %, 93 %, and 86 %, respectively. However, the proportion of low molecular weight PAHs increases, especially for 2-ring a-PAHs and 3-ring n-PAHs. Domestic solid fuel burning induces greater damage to the small airway than the large airway. Pulmonary function parameter reductions in the clean coal group are much less than those in the other two fuel groups. Salivary interleukin-6 (IL-6) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) significantly correlated with PAH species, among which p-PAHs and PAHs derivatives strongly with IL-6 and 8-OHdG, respectively. The correlation between PAHs and biomarkers in urine is insignificant. In addition, the use of clean coal can reduce the cancer risk for the four classes of PAHs by 60 %-97 %, mainly owing to the lower contributions from p-PAHs and o-PAHs. The result of the study provides scientific support for clean energy retrofit and an understanding of health benefits from solid fuel substitutions.

[Pollution Characterizations and Oxidative Potentials of Water-Soluble Organic Matters at Different Polarity Levels in Winter PM2.5 Over Xi'an].

Atmospheric fine particulate matter (PM2.5) can produce reactive oxygen species (ROS), which have adverse effects on health. Acidic, neutral, and highly polar water-soluble organic matter (WSOM) is an important component of ROS in organic aerosols. PM2.5 samples were collected in winter 2019 in Xi'an City to deeply explore the pollution characteristics and health risks of WSOM components with different polarity levels. The results showed that the concentration of WSOM in PM2.5 in Xi'an was (4.62±1.89) µg·m-3, humic-like substances (HULIS) were an important part of WSOM (78.81%±10.50%), and the proportion of HULIS was higher in haze days. The concentration levels of three WSOM components with different polarities in haze and non-haze days were:neutral HULIS (HULIS-n)>acidic HULIS (HULIS-a)>highly-polarity WSOM(HP-WSOM) and HULIS-n>HP-WSOM>HULIS-a. The oxidation potential (OP) was measured using the 2',7'-dichlorodihydrofluorescein (DCFH) method. It was found that the law of OPm in haze and non-haze days was HP-WSOM>HULIS-a>HULIS-n, and the characteristic of OPv was HP-WSOM>HULIS-n>HULIS-a. During the whole sampling period, OPm was negatively correlated with the concentrations of the three components of WSOM. The OPm of HULIS-n (R2=0.8669) and HP-WSOM (R2=0.8582) in haze days were highly correlated with their respective concentrations. The OPm of HULIS-n, HULIS-a, and HP-WSOM in non-haze days were strongly dependent on their respective component concentrations.

Effects of indoor air purification intervention on blood pressure, blood­oxygen saturation, and heart rate variability: A double-blinded cross-over randomized controlled trial of healthy young adults.

The use of indoor air purifier (IAP) has received growing attention as a mitigation strategy for reducing indoor air pollution, but the evidence on their cardiovascular benefits is unclear. This study aims to evaluate whether the use of IAP can reduce the adverse effects of indoor particulate matter (PM) on cardiovascular health among young healthy population. A randomized, double-blind, cross-over, IAP intervention of 38 college students was conducted. The participants were assigned into two groups to receive the true and sham IAPs for 36 h in random order. Systolic and diastolic blood pressure (SBP; DBP), blood oxygen saturation (SpO2), heart rate variability (HRV) and indoor size-fractioned particulate matter (PM) were real-time monitored throughout the intervention. We found that IAP could reduce indoor PM by 41.7-50.5 %. Using IAP was significantly associated with a reduction of 2.96 mmHg (95 % CI: -5.71, -0.20) in SBP. Increased PM was significantly associated with increased SBP (e.g., 2.17 mmHg [0.53, 3.81], 1.73 mmHg [0.32, 3.14] and 1.51 mmHg [0.28, 2.75] for an IQR increment of PM1 [16.7 µg/m3], PM2.5 [20.6 µg/m3] and PM10 [37.9 µg/m3] at lag 0-2 h, respectively) and decreased SpO2 (-0.44 % [-0.57, -0.29], -0.41 % [-0.53, -0.30] and - 0.40 % [-0.51, -0.30] for PM1, PM2.5 and PM10 at lag 0-1 h, respectively), which could last for about 2 h. Using IAPs could halve indoor PM levels, even in relatively low air pollution settings. The exposure-response relationships suggested that the benefits of IAPs on BP may only be observed when indoor PM exposure is reduced to a certain level.

Insights into the nitroaromatic compounds, formation, and light absorption contributing emissions from various geological maturity coals.

Nitroaromatic compounds (NACs) are essential components of atmospheric organic aerosols. Coal combustion is a key source of atmospheric NACs. In this study, a triple-quadrupole liquid chromatography-mass spectrometry (LC-MS) system was used to identify ten individual NAC emitted in combustions of chunk coal and its briquette at different maturity levels. The Gaussian calculation was applied to quantify the absorption contribution of NACs to brown carbon (BrC). The emission factors (EFs) of total quantified NACs (ΣNACs) are 21.80-4429.55 µg/kg. 4-Nitrocatechol (4NC) is the most abundant NACs, accounting for 25.5-82.3 % of the ΣNACs and has the largest contribution to light absorption (0.34-29.23 %). The EFs for ΣNACs of chunk coal are 1.1-3.0 times those of its briquette, while the coal with volatile matter (VM) = 35.83 % shows the highest NAC emissions. The reaction pathway analysis demonstrates that NACs in briquette are generated through the pyrolysis of coal tar at an early stage of coal combustion, while volatile organic compounds (VOCs) that are emitted in chunk coal contribute greatly to the formations of NACs. The molecular properties analysis reveals that ΣNACs contribute 0.47-35.27 % to BrC light absorption. Anthracite coal (VM = 8.01 %) demonstrates the lowest light absorption coefficient (babs-365). Since bituminous coal (with VM = ~10 %-40 %) is popularly used for heating in rural China in winter, the results of this study could assist to evaluate the climate and environmental impacts on the NACs emission from coal combustion on a regional scale. Finally, the results highlighted that replacements of bituminous by clear fuel (such as chunk or briquette anthracite) could reduce NACs emission effectively.

VOC emission profiles from typical solid fuel combustion in Fenhe River Basin: Field measurements and environmental implication.

This study examined volatile organic compounds (VOCs) emitted from the combustion of seven typical biomass fuel types in a traditional stove, elevated kang, and biomass furnace and from the combustion of three types of coal in coal furnaces. The results revealed that emission factors (EFs) of VOCs emitted from combustion processes ranged from 48.8 ± 29.1 mg/kg (for anthracite combustion in an outdoor boiler) to 5700 ± 6040 mg/kg (for sesame straw combustion in a traditional stove). Changing the fuel type engendered a more significant EF reduction (82.7%) than changing the stove type (51.8%). The emitted VOCs (including oxygenated VOCs, OVOCs) can be ordered as follows (in descending order) in terms of proportion: OVOCs > alkenes > aromatic VOCs > alkanes > halo hydrocarbons > alkynes. These results indicate solid fuel combustion processes warrant attention because they produce high OVOC emissions. The ozone formation potential (OFP) values derived for VOCs emitted from solid fuel combustion ranged from 5.83 ± 0.72 to 1910 ± 1750 mg/kg. Clean fuel and clean stove technologies both exhibited >80% efficiency levels in reducing OFP emissions (e.g., 80.6% reduction for the optimal fuel; 89.4% reduction for a clean stove). Therefore, the difference between VOC emission profiles from different combustion technologies should not be ignored. This study also noted substantial differences between VOC emissions from residential combustion and industrial combustion. Accordingly, attention should be paid to the local characteristics of fuels and stoves and to VOC emissions from residential combustion.