Impact of formaldehyde on ozone formation in Central China: Important role of biogenic emission in forest region.

Formaldehyde (HCHO) is an important source for driving tropospheric ozone (O3) formation. This study investigated the combined effects of anthropogenic and biogenic emission on O3 formation in the Guanzhong Basin (GZB), Central China, providing useful information into the mechanisms of O3 formation due to the interaction between anthropogenic and biogenic volatile organic compounds (VOCs). A severe O3 pollution episode in summer of 2017 was simulated using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to examine the impacts of ambient HCHO on ground-level O3. Results showed secondary HCHO dominated ambient levels, peaking in the afternoon (up to 86 %), while primary emissions contributed 14 % on average. This enhanced O3 production by 7.7 % during the morning rush hour and 24.3 % in the afternoon. In addition, HCHO concentration peaked before that of O3, suggesting it plays significant role in O3 formation. Biogenic emission oxidation contributed 3.1 µg m-3 (53.1 %) of HCHO and 5.2 pptv (40.1 %) of hydroperoxyl radicals (HO2) in average urban areas, where the downwind regions of the forests had high nitrogen oxides (NOx) levels and favorable conditions for O3 production (17.3 µg m-3, 20.5 %). In forested regions, sustained isoprene oxidation led to elevated oxidized VOCs including HCHO and acetaldehyde downwind, which practiced further photolysis of O3 formation with anthropogenic NOx in urban areas. Sensitivity experiments recommend controlling industrial and traffic NOx emissions, with regional joint prevention and regulation, which are essential to reduce O3 pollution.

Disease types and pathogenic mechanisms induced by PM2.5 in five human systems: An analysis using omics and human disease databases.

Atmospheric fine particulate matter (PM2.5) can harm various systems in the human body. Due to limitations in the current understanding of epidemiology and toxicology, the disease types and pathogenic mechanisms induced by PM2.5 in various human systems remain unclear. In this study, the disease types induced by PM2.5 in the respiratory, circulatory, endocrine, and female and male urogenital systems have been investigated and the pathogenic mechanisms identified at molecular level. The results reveal that PM2.5 is highly likely to induce pulmonary emphysema, reperfusion injury, malignant thyroid neoplasm, ovarian endometriosis, and nephritis in each of the above systems respectively. The most important co-existing gene, cellular component, biological process, molecular function, and pathway in the five systems targeted by PM2.5 are Fos proto-oncogene (FOS), extracellular matrix, urogenital system development, extracellular matrix structural constituent conferring tensile strength, and ferroptosis respectively. Differentially expressed genes that are significantly and uniquely targeted by PM2.5 in each system are BTG2 (respiratory), BIRC5 (circulatory), NFE2L2 (endocrine), TBK1 (female urogenital) and STAT1 (male urogenital). Important disease-related cellular components, biological processes, and molecular functions are specifically induced by PM2.5. For example, response to wounding, blood vessel morphogenesis, body morphogenesis, negative regulation of response to endoplasmic reticulum stress, and response to type I interferon are the top uniquely existing biological processes in each system respectively. PM2.5 mainly acts on key disease-related pathways such as the PD-L1 expression and PD-1 checkpoint pathway in cancer (respiratory), cell cycle (circulatory), apoptosis (endocrine), antigen processing and presentation (female urogenital), and neuroactive ligand-receptor interaction (male urogenital). This study provides a novel analysis strategy for elucidating PM2.5-related disease types and is an important supplement to epidemiological investigation. It clarifies the risks of PM2.5 exposure, elucidates the pathogenic mechanisms, and provides scientific support for promoting the precise prevention and treatment of PM2.5-related diseases.

Exposure to polycyclic aromatic hydrocarbons (PAHs) from domestic heating and cooking combustion of different fuel types for elders in rural China.

Solid fuel combustion emitted abundant pollutants, especially polycyclic aromatic hydrocarbons (PAHs) which had significant minus impact on human health in rural China. PAHs in PM2.5 emitted from different fuels combustion and hydroxylated metabolites of PAHs (OH-PAHs) in urine samples of different fuel users were detected in this study. The indoor PAHs were higher than that in outdoors for solid fuel use households, and the concentration of PAHs in the indoor of liquefied petroleum gas (LPG) use household was not much lower than solid fuel use households. Biogas-use household produced the lowest PAHs, which significantly reduced 64-82% compared with those emitted by solid fuel combustion. The different combustion conditions influenced the gaseous PAHs in indoors between two sampling sites. The gas/particle partition indicated that PAHs tended to occur in the particle phase with increased molecular weight, and the absorption was the main mechanism. The relative higher contribution of high molecular weight PAHs (HMW-PAHs) in solid fuel use households than in clean fuel use households, induced more health risks of PAHs. The concentration of Σ10OH-PAHs in the urine samples for elders of different fuel-use households displayed the trend of coal (83.27 ng/mL) > wood (79.32 ng/mL) > LPG (51.61 ng/mL) > biogas (28.96 ng/mL), and OH-NaPs was the predominant metabolites, which accounted for more than 90% of the total concentration. The carcinogenic risk of PAHs based on internal exposure was greater than or close to 10-4, with serious carcinogenic risks. This was different with the incremental lifetime cancer risk based on the atmospheric concentrations. The exposure of PAHs from solid fuel combustion for human being especially for the elders in this region should be concerned, and more data should be done for the internal exposure of PAHs.

Characteristics of PM2.5 bounded carbonaceous aerosols, carbon dioxide and its stable carbon isotopes (δ13C) in rural households in northwest China: Effect of different fuel combustion.

In order to fully understand the carbon emission from different fuels in rural villages of China, especially in the typical atmospheric pollution areas. The characteristics of carbonaceous aerosols and carbon dioxide (CO2) with its stable carbon isotope (δ13C) were investigated in six households, which two households used coal, two households used wood as well as two households used biogas and liquefied petroleum gas (LPG), from two rural villages in Fenwei Plain from March to April 2021. It showed that the fine particulate matter (PM2.5) emitted from biogas and LPG couldn't be as lower as expected in this area. However, the clean fuels could relatively reduce the emissions of organic carbon (OC) and element carbon (EC) in PM2.5 compare to the solid fuels. The pyrolyzed carbon (OP) accounted more total carbon (TC) in coal than the other fuels use households, indicating that more water-soluble OC existed, and it still had the highest secondary organic carbon (SOC) than the other fuels. Meantime, the coal combustions in the two villages had the highest CO2 concentration of 527.6 ppm and 1120.6 ppm, respectively, while the clean fuels could effectively reduce it. The average δ13C values (-26.9‰) was much lighter than almost all the outdoor monitoring and similar to the δ13C values for coal combustion and vehicle emission, showing that they might be the main contributors of the regional atmospheric aerosol in this area. During the sandstorm, the indoor PM2.5 mass and CO2 were increasing obviously. The indoor cancer risk of PAHs for adults and children were greater than 1 × 10-6, exert a potential carcinogenic risk to human of solid fuels combustion in rural northern China. It is important to continue concern the solid fuel combustion and its health impact in rural areas.

Combined use of principal component analysis/multiple linear regression analysis and artificial neural network to assess the impact of meteorological parameters on fluctuation of selected PM2.5-bound elements.

Based on the data of the State of Global Air (2020), air quality deterioration in Thailand has caused ~32,000 premature deaths, while the World Health Organization evaluated that air pollutants can decrease the life expectancy in the country by two years. PM2.5 was collected at three air quality observatory sites in Chiang-Mai, Bangkok, and Phuket, Thailand, from July 2020 to June 2021. The concentrations of 25 elements (Na, Mg, Al, Si, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Sr, Ba, and Pb) were quantitatively characterised using energy-dispersive X-ray fluorescence spectrometry. Potential adverse health impacts of some element exposures from inhaling PM2.5 were estimated by employing the hazard quotient and excess lifetime cancer risk. Higher cancer risks were detected in PM2.5 samples collected at the sampling site in Bangkok, indicating that vehicle exhaust adversely impacts human health. Principal component analysis suggests that traffic emissions, crustal inputs coupled with maritime aerosols, and construction dust were the three main potential sources of PM2.5. Artificial neural networks underlined agricultural waste burning and relative humidity as two major factors controlling the air quality of Thailand.

Characteristics, sources, and health risk assessment of atmospheric particulate mercury in Guanzhong Basin.

Mercury (Hg) has received increasing public attention owing to its high toxicity and global distribution capability via long-range atmospheric transportation. Guanzhong Basin (GB) is vital for the industrial and economic development of Shaanxi Province. To determine the concentration, spatial distribution, seasonal variation, sources, and health risks of particulate-bound mercury (PBM), PM2.5 samples were collected at three sampling sites representing urban, rural, and remote areas during winter and summer in GB. The three sampling sites were in Xi'an (XN), Taibai (TB), and the Qinling Mountains (QL). The mean PBM concentrations in XN, TB, and QL in winter were 130 ± 115 pg m-3, 57.5 ± 47.3 pg m-3, and 53.6 ± 38.5 pg m-3, respectively, higher than in summer (13.7 ± 7.11 pg m-3, 8.01 ± 2.86 pg m-3, and 7.75 ± 2.85 pg m-3, respectively). PBM concentrations are affected by precipitation, meteorological conditions (temperature and mixed boundary layer), emission sources, and atmospheric transport. During the sampling period, the PBM dry deposition in XN, TB, and QL was 1.90 µg m-2 (2 months), 0.835 µg m-2 (2 months), and 0.787 µg m-2 (2 months), respectively, lower than the range reported in national megacities. According to backward trajectory and potential source contribution factor (PSCF) analysis, mercury pollution in XN is mainly affected by local pollution source emissions, whereas the polluted air mass in TB and QL originates from local anthropogenic emissions and long-distance atmospheric transmission. The non-carcinogenic health risk values of PBM in XN, TB, and QL in winter and summer were less than 1, indicating that the risk of atmospheric PBM to the health of the residents was negligible.

Characteristics and health risk assessment of indoor and outdoor PM2.5 in a rural village, in Northeast of China: impact of coal and biomass burning.

Fine particulate matter (PM2.5) has health effects that may depend on its sources and chemical composition. In this study, characteristics of PM2.5 chemical composition and health risk assessment from Songyuan, China, were investigated during day and night in indoor and outdoor from February 4 to 19, 2021. Relative high concentrations of PM2.5 were obtained in indoor environment than outdoor, with 503.95 ± 209.62 µg/m3 during the day and 357.52 ± 232.81 µg/m3 at night for the indoor environment. Relatively high total carbon, organic carbons, elemental carbons, polycyclic aromatic hydrocarbons (PAHs), and oxygenated polycyclic aromatic hydrocarbons (OPAHs) were obtained in indoor environment. However, the average concentrations of PAHs were higher during night (73.57 ± 43.09 ng/m3) in indoor and OPAHs during day (6.027 ± 2.960 ng/m3) in outdoor. They had different I/O distributions of these compounds during day and night. Indeno(1,2,3-cd) pyrene was the dominant PAHs, and benzanthrone was the dominant OPAHs; this is different with the previous studies. The high indoor/outdoor ratios showed the indoor coal and biomass burning greatly affect the indoor pollutants. Average ILCR health risk assessment for PAHs was all higher than 10-6 for different age gender, suggesting there has potential cancer risk existed for populations living in the rural coal and biomass burning area Songyuan, China.

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.

Refractory black carbon aerosols in rainwater in the summer of 2019 in Beijing: Mass concentration, size distribution and wet scavenging ratio.

Black carbon (BC) aerosols in the atmosphere play a significant role in climate systems due to their strong ability to absorb solar radiation. The lifetime of BC depends on atmospheric transport, aging and consequently on wet scavenging processes (in-cloud and below-cloud scavenging). In this study, sequential rainwater samples in eight rainfall events collected in 2 mm interval were measured by a tandem system including a single particle soot photometer (SP2) and a nebulizer. The results showed that the volume-weighted average (VWA) mass concentrations of refractory black carbon (rBC) in each rainfall event varied, ranging from 10.8 to 78.9 µg/L. The highest rBC concentrations in the rainwater samples typically occurred in the first fraction from individual rainfall events. The geometric mean median mass-equivalent diameter (MMD) decreased under precipitation, indicating that rBC with larger sizes was relatively aged and preferentially removed by wet scavenging. A positive correlation (R2 = 0.73) between the VWA mass concentrations of rBC in rainwater and that in ambient air suggested the important contribution of scavenging process. Additionally, the contributions of in-cloud and below-cloud scavenging were distinguished and accounted for 74% and 26% to wet scavenging, respectively. The scavenging ratio of rBC particles was estimated to be 0.06 on average. This study provides helpful information for better understanding the mechanism of rBC wet scavenging and reducing the uncertainty of numerical simulations of the climate effects of rBC.

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.

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.

High time-resolution source apportionment and health risk assessment for PM2.5-bound elements at an industrial city in northwest China.

To better respond to heavy air pollution, the local government of Baoji City, a traditionally industry dominated city in northwest China, released several warning levels between December 2019 and January 2020. The system aims to provide a more efficient control of pollution sources. In this study, a high-time resolution measurement of PM2.5-bound elements was applied to capture the diurnal-scale dynamic processes associated with major pollution activities in northwest China. A series of elements were quantified and used for source apportionment using the positive matrix factorization (PMF) model. Combined with the local characteristics, nine sources were resolved with contributions in descending order: fugitive dust (36.6 %), biomass burning (20.1 %), traffic-related (10.4 %), coal combustion (10.0 %), titanium alloy smelting (7.2 %), As-related industry (6.9 %), Zn-related industry (5.6 %), molybdenum alloy smelting (2.5 %), and Cr-related industry (0.7 %). The health risk assessment indicated non-carcinogenic risks for Mn and carcinogenic risks for As and Cr in both adults and children. The cumulative non-carcinogenic risk for the elements was 3.2 times the safety threshold, while the carcinogenic risk (CR) was 6.8 and 27 times the acceptable levels for children and adults, respectively. For source-resolved risks, As- and Cr-related industry emissions showed the highest carcinogenic risk. Five of the nine resolved sources for adults have CR values 1.4 and 9.7 times the acceptable level. This study provides valuable information for developing targeted strategies to control air pollutants and protect public health.

Health benefits from substituting raw biomass fuels for charcoal and briquette fuels: In vitro toxicity analysis.

PM2.5 (particulate matters with diameter ≤ 2.5 µm) from biomass fuel combustion has been identified as a major cause of cardiopulmonary diseases. Briquette and charcoal are two representative processed fuels that exhibit different emission characteristics. This study compared three types of biomass fuels (maize straw, wheat straw, and wood branches) and their respective processed fuels in terms of their emission factors (EFs). The bioreactivity of human alveolar epithelial (A549) cells to exposure to various fuel-emitted PM2.5 was assessed. The EFs of lactic dehydrogenase (LDH) and interleukin-6 (IL-6) were calculated to compare actual cytotoxicity. The PM2.5 EFs of maize and wheat straw were higher than those of wood branches, and following the processes of briquetting and carbonization, the EFs of PM2.5 and chemical components were effectively reduced. Cell membrane damage and inflammatory responses were observed after A549 cell exposure to PM2.5 extracts. The expression of bioreactivity to briquettes and charcoals was lower than that to raw fuels. The EFs of LDH and IL-6 were also significantly reduced after briquetting and carbonization. This underscores the necessity of fuel treatment for reducing cytotoxicity. The crucial chemical components that contributed to cell oxidative and inflammatory responses were identified, including organic and elemental carbon, water-soluble ions (e.g., K+, Mg2+, and Ca2+), metals (e.g., Fe, Cr, and Ni), and high-molecular-weight PAHs. This study elucidated the similarities and differences of PM2.5 emissions and cytotoxicity of three types of biomass fuel and demonstrated the positive effects of fuel treatment on reducing adverse pulmonary effects.

Associations of personal exposure to domestic heating and cooking fuel emissions and epidemiological effects on rural residents in the Fenwei Plain, China.

Solid fuel combustion for domestic heating in northern China in the wintertime is of great environmental and health concern. This study assesses personal exposure to particulate matter with different aerodynamic diameters and multiple gaseous pollutants from 123 rural residents in Yuncheng, the Fenwei Plain. The subjects are divided into groups based on the unique energy source applied, including biomass, coal, and electricity/no heating activities. The health effects of the exposures are expressed with four urinary biomarkers. The personal exposure levels to three different aerodynamic particle sizes (i.e., PM10, PM2.5, and PM1) of the electricity/no heating group are 5.1 % -12 % lower than those of the coal group. In addition, the exposure levels are 25 %-40 % lower for carbon monoxide (CO) and 10.8 %-20.3 % lower for ozone (O3) in the electricity/no heating group than the other two fuel groups. C-reactive protein (CRP) in the urine of the participants in biomass and coal groups is significantly higher than that in the electricity/no heating group, consistent with the observations on other biomarkers. Increases in 8-hydroxy-2 deoxyguanosine (8-OHdG), interleukin-8 (IL-8), and vascular endothelial growth factor (VEGF) are observed for the exposures to higher concentrations of air pollutants. For instance, PMs and nitrogen dioxide (NO2) show significant impacts on positive correlations with 8-OHdG and IL-8, while O3 positively correlates with CRP. PM1 exhibits higher effects on the biomarkers than the gaseous pollutants, especially on VEGF and IL-8. The study indicates that excessive use of traditional domestic solid fuels could pose severe health effects on rural residents. The promotion of using clean energy is urgently needed in the rural areas of northern China.

Trace elements in outdoor and indoor PM2.5 in urban schools in Xi'an, Western China: characteristics, sources identification and health risk assessment.

The PM2.5-bounded elements were measured in outdoor and indoor from two urban middle schools in Xi'an. The PM2.5 mass was from 42.4 to 283.7 µg/m3 with bounded element from 3.4 to 41.7 µg/m3. Both the particle mass and the bounded elements displayed higher levels compared with previous studies in school environments. The most abundant elements were Ca, K, Fe, S, Zn and Cl both indoor and outdoor in two schools, which accounted for about 90% of the total elements. Strong correlations between indoor and outdoor were obtained along with relative effect from students' and teachers' activities on the indoor distributions between workdays and weekends. There had different indoor/outdoor (I/O) distributions for the two schools. It revealed the main outdoor sources for elements in JT and predominance of indoor sources in HT. The principal component analysis investigated main sources of elements in this study were coal combustion, geogenic dust and industrial emission, even though there displayed differences in the two school classrooms. The health risk assessment showed that the cancer risk for Ni and Pb was below the safe value while As and Cr might pose acceptable potential threat to both students' and teachers' health. The total non-cancer risks of accumulative multi-metals in JT exhibited to be higher than 1, indicating that there existed the potential non-carcinogenic health risks of exposure metals.

Water-soluble iron in PM2.5 in winter over six Chinese megacities: Distributions, sources, and environmental implications.

Water-soluble iron (ws-Fe) in PM2.5 plays a crucial role in biogeochemical cycles and atmospheric chemical processes. The anthropogenic sources of ws-Fe have attracted considerable attention owing to its high solubility. However, few studies have investigated the content of PM2.5 ws-Fe in the urban environment. In the present study, we characterized the spatial distributions of ws-Fe in six Chinese megacities in the winter of 2019. Furthermore, we investigated the speciation of PM2.5 ws-Fe (ws-Fe(II) and ws-Fe(III)), potential sources of ws-Fe, and association between ws-Fe and particle-bound reactive oxygen species (ROS). Higher ws-Fe concentrations were observed in northern cities (Harbin, Beijing, and Xi'an) than in southern cities (Chengdu, Wuhan, and Guangzhou). Moreover, atmospheric ws-Fe concentrations in urban China were several folds higher than those in urban areas of the United States and several orders of magnitude higher than those in remote oceans, indicating that China is a key contributor to global atmospheric ws-Fe. The dominant form of ws-Fe was ws-Fe(III) in Beijing, whereas ws-Fe(II) was more abundant in the other five cities. The concentrations of ws-Fe and ws-Fe(II) concentrations increased with increasing PM2.5 levels in all the six cities, however, we did not observe any consistent pattern of ws-Fe(III) concentration. Biomass burning was a dominant source of ws-Fe in all cities except Beijing. A strong positive correlation was observed between particle-bound ROS content and ws-Fe; this finding is consistent with those of previous studies indicating that ws-Fe in PM2.5 notably influences atmospheric chemical processes and human health.

Concentrations and source identification of priority polycyclic aromatic hydrocarbons in sediment cores from south and northeast Thailand.

In this study, the environmental fate of carcinogenic polycyclic aromatic hydrocarbons (PAHs) in tropical lake sediments and their potential sources have been discussed. 15 PAHs (i.e. ΣPAH) have been investigated in two lakes, namely Songkhla Lake (SKL) and Nong Han Kumphawapi Lake (NHL), which are located at the southern and north-eastern parts of Thailand, respectively. Since these two lakes are registered as important wetlands under the Ramsar convention (United Nations Educational, Scientific and Cultural Organization: UNESCO), the quantitative identification of potential contributors of PAHs is an inevitable analytical tool for launching an evidence-based policy. The ΣPAH concentrations observed in SKL and NHL sediments (n = 135) were in the range of 19.4-1,218 ng g-1 and 94.5-1,112 ng g-1, respectively. While the exponential decline of ΣPAH contents were detected in SKL sediments, NHL showed a trend of enhancing PAH contents with depth. The averaged benzo [a]pyrene (B [a]P) contents of surface sediments in both lakes were much below the value stipulated by the United States Environmental Protection Agency (US-EPA) guidelines for carcinogen risk assessment. Based on numerous multivariate statistical techniques coupled with source apportionment analysis, "biomass burning" and "anthropogenic activities" are two potential contributors of the PAHs detected in the study areas. To achieve the long-term conservation of nature with related ecosystem services and cultural values, it is therefore important to promote decision-making based on ecotoxicological studies of carcinogenic substances.

Comparison of black carbon, primary and secondary brown carbon light absorption and direct solar absorption at the foothill and summit of Mt. Hua, China.

Atmospheric black carbon (BC), primary and secondary brown carbon (BrCpri and BrCsec) are the light-absorbing carbonaceous aerosol components. The vertical changes in the BC and BrC distributions are not generally known. Here, we presented a study of the spectral light absorption properties, direct solar absorption, and potential source areas of BC and BrC at the foothill (375 m a.s.l.) and summit (2060 m a.s.l.) of Mt. Hua, China. More than tripled BC and BrC light absorption coefficient were observed at the foothill compared to the summit. The dominant carbonaceous light-absorbing was attributed to BC with the percentages of 77 % (foothill) and 79 % (summit), respectively. The light absorption coefficient and direct solar absorption of BrCpri were much higher than those of BrCsec at foothill, especially in winter. The enhancing contributions of BrCsec light absorption coefficient and direct solar absorption were observed with high RH and visibility at the summit. The light absorption properties of BC, BrCpri, and BrCsec may be attributed to the emissions, meteorological conditions, and photochemical oxidation. The inferred potential source spatial distributions of BC and BrCpri showed different patterns at the foothill and summit. The results underlined the primary emission effects (including BC and BrCpri) at the foothill and the importance of BrCsec at the summit, respectively.

Assessment of the inhalation exposure and incremental lifetime cancer risk of PM2.5 bounded polycyclic aromatic hydrocarbons (PAHs) by different toxic equivalent factors and occupancy probability, in the case of Xi'an.

Polycyclic aromatic hydrocarbons (PAHs) are widespread toxic pollutants in the atmosphere and have attracted much attention for decades. In this study, we compared the health risks of PAHs based on different toxic equivalent factors (TEFs) in a heavily polluted area during heating and non-heating periods. We also pay attention to occupancy probability (OP) in different polluted areas. The results showed that there were big differences for calculations by different TEFs, and also by OP or not. Age groups except adults were all lower calculated by OP than not. The sensitivity analysis results on the incremental lifetime cancer risks (ILCR) for population groups by Monte Carlo simulation identified that the cancer slope factor extremely affected the health risk assessment in heating periods, followed by daily inhalation exposure levels. However, daily inhalation exposure levels have dominated the effect on the inhalation ILCR and then followed by the cancer slope factor in non-heating periods. The big differences by different calculations investigated that it is important to set up the correlations between the pollution level and health risks, especially for the longtime health assessment.

A comprehensive evaluation of PM2.5-bound PAHs and their derivative in winter from six megacities in China: Insight the source-dependent health risk and secondary reactions.

Atmospheric PAHs (polycyclic aromatic hydrocarbons) and their derivatives are a global concern that influences environments and threatens human health. Concentrations of 52 PAHs and the main derivatives in six Chinese megacities were measured in the winter of 2019. The concentrations of ∑PAHs (sum of 52 PAHs) ranged from 19.42 ± 7.68 to 65.40 ± 29.84 ng m-3, with significantly higher levels in northern cities (Harbin [HB], Beijing [BJ], and Xi'an [XA]) than southern ones (Wuhan [WH], Chengdu [CD] and Guangzhou [GZ]). Source apportionment of ∑PAHs was conducted by the PMF model and results showed coal combustion and traffic emissions were the two dominant sources, which dominated ∑PAHs in northern and southern cities, respectively. Biomass burning was also characterized as a crucial source of ∑PAHs and showed extremely high contributions in XA (42.5%). Assisted by the individual PAH source apportionment results, the source-depend TEQ (total BaP equivalent) and incremental lifetime cancer risk (ILCR) were firstly reported in these cities. The results highlighted the contributions of coal combustion and biomass burning to both TEQ and ILCR, which were underestimated by ∑PAHs source apportionment. Secondary organic aerosol-derived PAHs were demonstrated to increase the TEQ compared with the fresh PAHs and three parameters, namely temperature, relative humidity, and O3 concentrations were characterized by multiple linear regression as the principal factors influencing secondary reactions of PAHs in winter. This study provides accurate human health-orientated results and potential control measures to mitigate the toxicity of secondary formed PAHs, and significantly decrease the uncertainty level of traditional methods. The results also revealed great progress in air pollution control by the Chinese government in the past 20 years, but still a long way to go to formulate strict emission control strategies from both environmental and human health-protective perspectives.