Coal Combustion Sources Research Articles

Pollution characteristics and ecological risk apportionment at a smelting site based on stochastic simulation

Geostatistical analysis and Pb isotope tracing were used to characterize the distribution patterns and the sources of heavy metals at a lead smelting site. Furthermore, ecological risks were apportioned based on stochastic theory. The results showed that soils were seriously contaminated by Pb, Zn, As, Cd, Cr and Hg, which reflected strong spatial heterogeneity. Based on MixSIAR model, the density distributions of three endmembers were deconstructed, in which 49.9% of Pb came from smelting activities, and 16.4% and 33.7% from coal combustion and geological source, respectively. Along with the integration of the apportionment of Pb isotope and Monte Carlo simulation, concentration-oriented probabilistic risk indicated that the moderate risk level was dominant, and Cd, As, Pb and Hg were sensitive factors. Source-oriented probabilistic risk presented that smelting contributed the most to risk accumulation. Therefore, the control of Cd, As, Pb and Hg and the disposal of potential smelting sources should be in priority.

Influence of anthropogenic activities and loess dusts on the rainwater hydrochemistry in the Chinese Loess Plateau

Rainwater hydrochemistry is an important indicator for tracing anthropogenic input on air quality. As the fastest economically developing city in the northwestern China and the Chinese Loess Plateau, rainwater chemistry, sources of dissolved solutes, and the influence of loess dust on rainwater chemistry in Xi'an city is unclear. Inorganic ions, δD and δ18O of two years' rainwater samples were measured to decipher the above issues. Rainwater samples were weakly alkaline (pH = 7.2) with the mean total dissolved solids (TDS) values of 43 mg/L. NH4+ and Ca2+ dominated in the cations and SO42− and NO3− dominated in the anions. The wet deposition of sulfur (S) and nitrogen (N) was 70.9 ± 67 mg·(m2·month)−1 and 244.8 ± 270.9 mg·(m2·month)−1, respectively. The meteoric water line in Xi'an was δD = 7.29δ18O+3.72 (R2 = 0.99). δD, δ18O, and d-excess analysis indicated the influence of evaporation on the dissolved solutes in rainwater, especially in the dry season. Rainwater acidity in the Xi'an city was mainly neutralized by Ca2+ and NH4+, and the neutralization ability in Xi'an city is higher than the southern China cities. Correlation analysis (CA), positive matrix factorization (PMF), and the backward air masses trajectory model identified high NH4+ and Ca2+ in rainwater were mainly originated from local agricultural activities and loess dust, while NO3− and SO42− were associated with local coal combustion and vehicle exhaust sources. High inputs of dusts and coal combustion in spring and winter resulted in elevated values of pH and major ions in Xi'an. Due to the air pollution control policy, air quality in Xi'an is getting better in recent years. Our study highlights the influence of anthropogenic activities and loess dusts on the rainwater hydrochemistry in Xi'an and provides important dataset for air pollution control for other cities in semi-arid and arid regions.

Incorporating source apportionment and bioaccessibility into human health risk assessment of heavy metals in a soil-rice system in the Jiulong River basin, southeast China

A positive matrix factorization–bioaccessibility–Monte Carlo simulation–human health risk assessment (PMF–BA–MCS–HHRA) model was developed to accurately assess the cumulative probability distributions of carcinogenic and non-carcinogenic risks posed by heavy metals in the soil-rice system of the Jiulong River basin, and to quantify the sources of the health risks. The results showed that natural, agricultural, industrial, and coal combustion sources were the four main sources of heavy metals. The bioaccessibilities of heavy metals through grain ingestion were significantly higher than other exposure pathways. A non-carcinogenic risk was posed by arsenic (As) and a carcinogenic risk by cadmium (Cd). The non-carcinogenic risks of heavy metals were higher for children than for adults, while the opposite was true for carcinogenic risks. The grain ingestion pathway presented the greatest health risk from heavy metals in the soil-rice system. The non-carcinogenic risks were mainly derived from industrial sources, while the carcinogenic risks primarily came from agricultural sources. Arsenic derived from industrial sources and Cd derived from agricultural sources should be prioritized for control. Grain ingestion should be considered the priority exposure pathway for control. These results provide important theoretical and practical references for human health risk assessment and source management of heavy metals in soil-rice systems.

Complex polycyclic aromatic compound mixtures in PM2.5 in a Chinese megacity: Spatio-temporal variations, toxicity, and source apportionment

Polycyclic aromatic compounds (PACs) are important toxic organic components in fine particulate matter (PM2.5), whereas the links between PM2.5 toxicity and associated PACs in ambient air are poorly understood. This study investigated the spatial–temporal variations of PACs in PM2.5 collected from 11 sampling sites across a Chinese megacity and characterized the reactive oxygen species (ROS) generation and cytotoxicity induced by organic extracts of PM2.5 based on cellular assays. The extra trees regression model based on machine learning and ridge regression were used to identify the key toxicants among complex PAC mixtures. The total concentrations of these PACs varied from 2.12 to 71.7 ng/m3 across the study city, and polycyclic aromatic hydrocarbons (PAHs) are the main PACs. The spatial variations of the toxicological indicators generally resembled those of the PAC concentrations, and the PM2.5 related to waste treatment facilities exhibited the strongest toxic potencies. The ROS generation was highly correlated with high molecular weight PAHs (MW302 PAHs), followed by PAHs with MW<302 amu and oxygenated PAHs, but not with nitrated PAHs and the plastics additives. The cell mortality showed weak correlations with these organic constituents. The associations between the biological endpoints and these PM2.5-bound contaminants were further confirmed by exposure to authentic chemicals. Four primary sources of PACs were identified, among which coal and biomass combustion sources (30.2% of the total PACs) and industrial sources (31.0%) were predominant. PACs emitted from industrial sources were highly associated with ROS generation in this city. Our findings highlight the potent ROS-generating potential of MW302 PAHs and the importance of industrial sources contributing to PM2.5 toxicity in this megacity, raising public concerns and further administration.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in sediments from Baiyang Lake, China.

The issue of polycyclic aromatic hydrocarbons (PAHs) has been an environmental focus worldwide. In this study, the contents, sources, and ecological risks of sixteen PAHs in the sediment of Baiyang Lake were estimated, and a list of priority pollutants was established. The total PAH contents ranged from 114 to 1010 ng·g-1. The composition of PAHs indicated that 4- to 6-ring PAHs predominated in the sediment samples. The diagnostic ratio analysis showed that combustion sources were predominant for PAHs in Baiyang Lake. Specifically, the positive matrix factorization model indicated that diesel engine emissions, gasoline engine emissions, wood combustion sources, and coal combustion sources contributed 22, 32, 24, and 22% of ∑PAHs, respectively. Based on the sediment quality guidelines, mean effects range median quotient, ecological risk quotient, and toxicity equivalent quotient methods, the comprehensive assessment results of PAHs in Baiyang Lake sediments indicated that the ecological risks were at medium and low levels. The priority pollutant list showed that benzo[b]fluoranthene and benzo[a]pyrene were the highest-priority pollutants and thus should be given more attention.

Content, Distribution, Source Analysis, and Risk Assessment of PAHs in Arable Soils of Taiyuan

PAHs (polycyclic aromatic hydrocarbons) accumulated in arable soils have significant impacts on farmland quality and human health, which has attracted wide attention from scientists and the public. A total of 22 arable soil samples were collected from Taiyuan, an old industrial city, including three districts (industrial zones, hilly areas, and sewage irrigation area), and the contents of 21 PAHs were detected using the GC-MS method. The sources of PAHs in soils were analyzed using the diagnostic ratios (DRs) method and positive matrix factorization (PMF) model, and the soil health risks were analyzed using the incremental lifetime cancer risk (ILCR) model. The results indicated that the average concentrations of Σ21PAHs and Σ16PAHs in arable soils of Taiyuan were 934.6 ng·g-1 and 787.7 ng·g-1, respectively, which were lower than the soil pollution risk screening value of agricultural land stipulated in GB 15168-2018. 3-5 rings PAHs were the dominant components, accounting for~90% of the Σ21PAHs. Approximately 60% of sites in industrial zones, 13% in hilly areas, and 33% in the sewage irrigation area had high PAHs contents larger than 1000 ng·g-1. The spatial distribution of PAHs showed that more severe PAHs pollution in the soil occurred in industrial areas than that in the other two districts. The DRs suggested that the combustion of coals, bio-masses, and traffic emissions were the dominant sources for PAHs pollution in arable soils in Taiyuan. The simulation results of the PMF model indicated that the sources and contribution rates of PAHs in cultivated soils were coal and biomass burning sources (59%), traffic sources (22%), and coking sources (19%). The risk assessment confirmed that the arable soils in Taiyuan had high potential carcinogenic risks; thus, more attention should be paid to the PAHs pollutions in arable soils.

Combined effects of temperature and monsoon on seasonal variations of atmospheric polycyclic aromatic hydrocarbons in the coastal Shanghai, China

An intensive sampling program was conducted at two coastal sites of megacity Shanghai - the emerging town Lingang New Area (LGNA), and the petrochemical-industry zone Jinshan Area (JSA) from July 2016–June 2017, to study the occurrence, sources, environmental behavior and fate of atmospheric polycyclic aromatic hydrocarbons (PAHs). Results showed the median concentrations of total atmospheric PAHs were 18 ng m−3 and 12 ng m−3 in JSA and LGNA, respectively, which were lower than those recently detected in northern coastal China, and previously detected in urban/suburban Shanghai. There was strong/opposite temperature dependence for gaseous and particle-bound PAHs, indicating the importance of ongoing local and nearby volatilization; While the gas-particle partitions of individual PAH compound changed dramatically with seasons, with most easily adsorbed on particles during colder months. The potential source contribution function (PSCF) and concentration weight trajectory (CWT) model demonstrated the interactions of terrestrial and marine air mass regulated by the East Asian monsoon. Specifically, PAHs released by wintertime coal heating in northern China and summertime marine shipping in East China Sea, that transported through northwest and southeast monsoon, respectively, and aggravated the pollution of coastal Shanghai, especially for the background site in LGNA. The positive matrix factorization (PMF) source apportionment suggested the dominance of petrogenic sources for gaseous PAHs, coal and biomass combustion sources for particle-bound PAHs, and further demonstrated the seasonal variations of these potential sources. Atmospheric PAHs would deposit to the coastal waters, with gaseous absorption fluxes almost an order of magnitude higher than those of particle-bound deposition.

Integration of adsorption based post-combustion carbon dioxide capture for a natural gas-fired combined heat and power plant

This paper proposes a continuous CO2 capture system for natural gas combined heat and power (CHP) facility and explores the potential of low-temperature vacuum-swing adsorption (VSA) process for post-combustion CO2 capture (PCC) in the context of carbon capture and storage (CCS). Although VSA has strong potential for efficient CO2 capture in district-scale energy systems, previous case studies have largely focused on high-emission coal combustion sources, making VSA application challenging for these conditions. We address this issue by theoretically designing a ready-to-operate flue gas cleaning process with CCS for a medium-sized 4.3 MW natural gas CHP operating in the local industry. Our in-depth analysis examines the most critical parts such as dehydration, involving condenser and temperature-swing adsorption (TSA), and CO2 capture via VSA. The conceptual design and performance of VSA are approached by developing a mathematical model to estimate the technology size and performance. This work shows that utilising a small fraction of heat recovered from CHP-generated flue gas is sufficient to supply the necessary heat for auxiliary units, and that using natural cooling water for dehydration effectively reduces moisture (87 vol%) and energy demand for final dehydration via TSA. Furthermore, it demonstrates that 4-step VSA consisting of 15 columns using zeolite 13X can separate CO2 with a desired purity of 90.4%, meeting the requirements for CO2 storage and transportation onshore, at a 15.6% recovery rate. The cost of achieving high CO2 purity without pre-pressurising the CO2-rich flue gas, while maintaining cycle simplicity, is discussed. Overall, our paper provides a comprehensive approach to retrofitting distract-scale power plants with CO2-lean emissions, presenting a ready-to-operate flue gas cleaning technology based on real operating conditions and technical restrictions, which can contribute towards decarbonisation.

Chemical processes of wintertime aerosols over the East China Sea based on aircraft and ground measurements: Comparison with the Sea of Japan

Aircraft and ground-level observations of wintertime aerosols over the East China Sea (ECS) around Japan's southwestern islands were conducted from the boundary layer to the middle troposphere (0–4.5 km) and compared to those over the Sea of Japan (SOJ) during the same period, for the purpose of comprehensive elucidation on modification process of chemical composition in aerosols at the Asian outflow receptor regions. The deficient values of Cl− in both cases for ECS and SOJ were higher at ground level than at high altitudes because of the acidic gas (HNO3, H2SO4) concentrations. Most Na+ and Cl− at high altitudes and at ground level originated from sea salt, because the (Na+ + Cl−) concentrations of which in the boundary layer observed were linearly related to the production flux of sea spray aerosol. The contribution of sea salt aerosols to cloud condensation nuclei appears to be low over the ECS, contrary to the SOJ. The non-sea salt (nss)-K+ concentrations and the path of backward trajectories suggest a significant impact of biomass burning on the SOJ associated with woodburning for residential heating in the Korean Peninsula. A similar difference was observed in NH4+/nss-SO42– equivalent ratios (∼0.5 for the ECS; ∼1 for the SOJ), which likely indicates ammonium sulfate aerosols produced in urban and industrial regions of Korea. The high aerosol Ca2+ concentration in the boundary layer over the ECS was accompanied by those of Na+, Cl−, NO3−, and nss-SO42– during cold front passages, as observed in SOJ. This indicates that Ca(NO3)2, CaSO4, and CaCl2 were formed via the reactions of acidic gases and Ca-rich dust particles from desert areas in the Asian continent, followed by the production of NaNO3 by uptake of acidic gases into sea salt in the ECS. This notion is supported by high Se(VI)/Se (IV) ratios (>2) that indicate an oxidative process during long-range transport from coal combustion sources.

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.

Seasonal Distribution and Source Apportionment of Chemical Compositions in PM2.5 in Nanchang, Inland Area of East China

PM2.5 was sampled in four seasons of 2021 in Nanchang. Organic carbon (OC), elemental carbon (EC), and water-soluble ions were the main chemical compositions in PM2.5. The annual average of OC/PM2.5 and EC/PM2.5 was 17.1% and 2.1%, respectively, while nine water-soluble ions were 56.7%. The order of each ion percentage in PM2.5 was NO3− &gt; SO42− &gt; K+ &gt; Na+ &gt; NH4+ &gt; Cl− &gt; NO2− &gt; Ca2+ &gt; Mg2+. The OC/EC (6.54, 13.17, 8.95, 7.99) and Char-EC/Soot-EC (0.88, 0.64, 1.32, 3.74) indicated that the carbon aerosols mainly originated from coal combustion, biomass combustion, and motor-vehicle emissions. High concentrations of Cl− and Ca2+ in spring were associated with dust sources. A good correlation between Na+, SO42−, and NO3− suggests the formation of Na2SO4 and NaNO3. The results of PM2.5 source apportionment by positive matrix factorisation (PMF) showed five main sources: motor-vehicle sources (18–33%), secondary sources (16–36%), coal combustion sources (16–30%), biomass-combustion sources (10–28%), and dust sources (5–7%). Backward trajectory clustering analysis showed PM2.5 in spring and autumn were more influenced by medium distance and local air but mainly influenced by local sources in winter.

Integrated Analysis on Source-exposure Risk of Heavy Metals in Farmland Soil Based on PMF Model: A Case Study in the E-waste Dismantling Area in Zhejiang Province

In order to explore the characteristics and sources of heavy metals in farmland soil and their risks to human health and to provide an important scientific basis for farmland pollution control, 133 surface soils (0-20 cm) were collected from typical agricultural production areas in Zhejiang Province, and the contents of soil Cd, Pb, Cr, Cu, Zn, Ni, As, and Hg were determined. Various methods were applied to evaluate the degree of heavy metal pollution in farmland and its ecological risks in the study area. The method of combining Kriging interpolation and positive definite matrix factor analysis (PMF) was applied to analyze the pollution sources and quantify the contribution of each pollution source. Combined with the health risk assessment model, the risk to human health of each pollution source was evaluated from the perspective of source exposure. The results showed that the average ω(Cd), ω(Pb), ω(Cr), ω(Cu), ω(Zn), ω(Ni), ω(As), and ω(Hg) were 0.76, 65.22, 92.02, 103.92, 198.49, 36.65, 5.97, and 0.20 mg·kg-1, respectively. The average contents of Cd and Cu were higher than the risk screening values of soil contamination of agricultural land, and 85.71% and 96.24% of soil was contaminated by heavy metals. The average contents of Pb, Cr, Zn, and Ni exceeded the soil background values of the Wenhuang Plain in Zhejiang Province, and the As and Hg contents were within the limit values. The potential soil ecological risks were mainly light-moderate, accounting for 90.98%, and both high and higher risk accounted for 4.51%; Cd was the main potential ecological risk element. The main sources of heavy metal pollution in the study area were the sources of the electronic waste dismantling process (26.82%), the mixed sources of coal combustion and traffic emissions (34.50%), mixed sources of natural parent materials and agricultural inputs (25.59%), and e-waste pickling runoff and solid waste leaching sources (13.09%). The health risk of heavy metal exposure to children was significantly greater than that in adults. Mixed sources of natural parent materials and agricultural inputs contributed the most to human health risks, and Cr was the element with the greatest contribution to human health risks.

Spatial distribution characteristics, source analysis and risk assessment of polycyclic aromatic hydrocarbons in topsoil of a typical chemical industry park

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in soil and are difficult to degrade, posing a great threat to the ecological environment and human health. Therefore, research on the distribution characteristics and risks of PAHs is of great significance to protect human and ecosystem health. Taking a typical chemical industry park in Chongqing as an example, the spatial distribution characteristics of PAHs content in 54 topsoil samples in the typical area were analyzed, and the soil PAHs pollution was evaluated by incremental models such as single-factor index and Nemerow comprehensive index. A factor decomposition model Positive Definite Matrix Factorization (PMF) was used to analyze the sources of PAHs. The results showed that 16 kinds of optimally controlled PAHs were detected, and the content of ΣPAHs in the topsoil ranged from ND to 16.07 mg/kg, with an average value of 1.78 mg/kg; spatially, pollutant levels are higher in the south and southwest of the park as well as in the center; source analysis showed that Chongqing The PAHs pollution in this typical chemical industry park in the city is from coke combustion sources, traffic emission sources, biomass combustion sources, oil sources, coal combustion sources and oil leakage sources, and the contribution rates to PAHs are 10.7%, 35.2%, 20.7%, and 5.0%, 24.6%, and 3.7%; respectively. The health risk assessment of soil PAHs shows that there is no potential carcinogenic risk of PAHs in different age groups in this area, and the main exposure route of adults is dermal &amp;gt; ingestion &amp;gt; inhalation, and the main exposure route of children is ingestion &amp;gt; dermal &amp;gt; inhalation.

Light absorption properties of brown carbon aerosol after following the switch from coal to natural gas policy in China: A case study of winter particulate matter over Xi'an, northwestern China

To control haze pollution, the Xi'an city in northwestern China replaced coal by natural gas in industrial and household heating at the end of 2017. Following this change we studied here the light absorption properties of brown carbon (BrC)in atmospheric particulate matter (PM2.5) over Xi'an in 2018. PM2.5 samples were collected from November 15 to December 25, 2018, and the light absorption properties of brown carbon in methanol-soluble organic carbon (MSOC) and water-soluble organic carbon (WSOC) were analyzed. Compared to a previous study from the coal combustion period, the mass absorption efficiency (MAE) increased in the sampling period while the radiation-forced absorption fraction of brown carbon relative to elemental carbon reduced, indicating that the light-absorbing capacity and efficiency of brown carbon has improved. Furthermore, highly positive linear relationships (r > 0.80) occur between the absorption coefficient and typical products of biomass burning and vehicle emission, except for coal combustion (r = 0.57). Additionally, an estimation from the positive matrix factorization and multivariable linear regression model results showed that biomass burning, motor vehicle emission, and secondary source took up approximately 89.53% of AbsWSOC,365. The contribution of coal combustion to light absorption BrC was the lowest (7.36% for AbsMSOC,365 and 10.24% for AbsWSOC,365) in our study, which differs from previous studies in Xi'an. Therefore, the emission source of bulk coal combustion has a relatively small influence on the light absorption of BrC in Xi'an.

Pollution Assessment and Source Analysis of Heavy Metals in Atmospheric Deposition in a Lead-zinc Smelting City Based on PMF Model

To explore the pollution characteristics and sources of heavy metals in atmospheric deposition in a typical lead-zinc smelting city, 511 effective atmospheric deposition samples from 22 points in different functional areas of a city in Henan Province were collected monthly during 2021. The concentrations and spatial-temporal distribution of heavy metals were analyzed. The geo-accumulation index method and health risk assessment model were utilized to evaluate the heavy metal pollution degree. The sources of heavy metals were quantitatively analyzed using a positive matrix factorization (PMF) model. The results showed that the average concentrations of ω(Pb), ω(Cd), ω(As), ω(Cr), ω(Cu), ω(Mn), ω(Ni), and ω(Zn) in atmospheric deposition samples were 3185.77, 78.18, 273.67, 149.50, 453.60, 810.37, 54.38, and 2397.38 mg·kg-1, respectively, which were all higher than the soil background values of Henan Province. All heavy metals except Mn had significant seasonal variation characteristics. The concentrations of Pb, Cd, As, and Cu in the industrial area with lead-zinc smelting were significantly higher than those in other functional areas, and the concentration of Zn was the highest in the residential mixed area. The results of the geo-accumulation index showed that the pollution of Cd and Pb were the most serious, followed by that of Zn, Cu, and As, which belonged to the serious-extreme pollution category. The main exposure route of non-carcinogenic risk was hand-mouth intake. Pb and As posed the greatest non-carcinogenic risk to children in all functional areas. The carcinogenic risks of Cr, As, Cd, and Ni through the respiratory system to humans were all below the threshold values. The analysis of the PMF model showed that the main sources of heavy metals in atmospheric deposition were industrial pollution sources (39.7%), transportation sources (28.9%), secondary dust sources (14.4%), incineration and coal combustion sources (9.3%), and natural sources (7.8%).

Types and Source Apportionment of Polycyclic Aromatic Hydrocarbons (PAHs) in Soil-Groundwater of a Closed Coking Plant in Shanxi Province, China

To clarify the impact of coking industry activities on the soil-groundwater Polycyclic aromatic hydrocarbon (PAH) occurrence, a typical coking site in Shanxi Province was taken as the study area, and soil and groundwater samples were collected to analyze the pollution level, composition, and distribution of PAHs in soil-groundwater. The sources of PAHs in the study area were identified based on the positive matrix decomposition model (PMF); the health risks of PAHs were calculated based on the carcinogenic and non-carcinogenic health risk model from the Technical Guidelines for Risk Assessment of Soil Pollution for Construction Land (HJ 25.3-2019) and toxicity equivalent quantity (TEQ). The results showed that ∑PAHs of soil ranged from 0 to 6077.7 mg/kg, with an average value of 198.02 mg/kg; ∑PAHs of groundwater ranged from 0 to 18.30 mg/L, with an average value of 9.39 mg/L. In horizontal distribution, ∑PAH content and types in the tar processing area were much higher than those in the surrounding area, and PAHs might migrate to the southwest through infiltration; in vertical distribution, ∑PAH content reached a peak at 5 m underground. According to the PMF model results, four primary sources of ∑PAHs were identified, which were the coking production source (55.0%), coal and petroleum combustion source (22.6%), atmospheric deposition source (13.1%) and residents living source (9.3%). The total average ∑PAH carcinogenic and non-carcinogenic health risks of soil in the study area were 7.05 × 10−6 and 0.695; the average TEQBaP−∑PAHs was 1.650 mg·TEQ/g; as for groundwater, they were 3.08 × 10−6 and 32.04; the average TEQBaP−∑PAHs was 9.390 μg·TEQ/L, indicating that PAHs both in soil and groundwater had potential health risks. This study provides a basis for the same coking site type for pollution control, secondary utilization, and data support for future site restoration.

Insight study of rare earth elements in PM2.5 during five years in a Chinese inland city: Composition variations, sources, and exposure assessment

The booming development of rare earth industry and the extensive utilization of its products accompanied by urban development have led to the accelerated accumulation of rare earth elements (REEs) as emerging pollutants in atmospheric environment. In this study, the variation of REEs in PM2.5 with urban (a non-mining city) transformation was investigated through five consecutive years of sample collection. The compositional variability and provenance contribution of REEs in PM2.5 were characterized, and the REEs exposure risks of children and adults via inhalation, ingestion and dermal absorption were also evaluated. The results showed an increase in the total REEs concentration from 46.46 ± 35.16 mg/kg (2017) to 81.22 ± 38.98 mg/kg (2021) over the five-year period, with Ce and La making the largest contribution. The actual increment of industrial and traffic emission source among the three pollution sources was 1.34 ng/m3. Coal combustion source displayed a downward trend. Ingestion was the main exposure pathway for REEs in PM2.5 for both children and adults. Ce contributed the most to the total intake of REEs in PM2.5 among the population, followed by La and Nd. The exposure risks of REEs in PM2.5 in the region were relatively low, but the trend of change was of great concern. It was strongly recommended to strengthen the concern about traffic-related non-exhaust emissions of particulate matter.

Indoor/outdoor relationships of PM2.5-associated toxic metals/metalloids at a rural residence in North China: Sources and probabilistic health risks

Levels of toxic metals/metalloids (TMs) in indoor air are of vital importance to the health of residents due to the high toxicity of TMs and the fact that the majority of the time is spent indoors. Currently, the relationship between indoor and outdoor TMs at rural residences remains unclear. In this study, 24-h samples of indoor and outdoor fine particulate matter (PM2.5) were simultaneously collected at a rural residence during the heating season in North China. The results revealed that the concentrations of PM2.5 and certain TMs indoors were higher than those outdoors (p < 0.05), and the low correlation between the indoor and outdoor concentrations indicates the slight influences of indoor and outdoor TMs. Among the TMs, the As concentration exceeded its environmental threshold (6 ng/m3) both indoors and outdoors. An integrated approach comprising positive matrix factorization (PMF), infiltration factor analysis, correlation analysis, and polar plot analysis was used to identify the sources of TMs. Regarding indoor emissions, indoor coal combustion, indoor cooking sources and fugitive dust were identified, while in regard to outdoor emissions, the sources included traffic emissions, coal combustion, fugitive dust, and industrial emissions. The probabilistic risk estimated via Monte Carlo simulations indicated that both the noncancer health risk (HI) and cancer risk (TCR) were unacceptable as the corresponding safety thresholds were exceeded (HI > 1 and TCR>10−4). In particular, As dominated both the noncancer and cancer risks (nearly 40%). Therefore, more efforts are needed to reduce the As concentration and coal combustion source in rural areas.

Temporal responses of PM2.5-bound trace elements and health risks to air control policy in a typical northern city in China during 2016–2020

A package of macro-control policies at the national level was an effective way to control air pollution. It was of great practical significance to study the trends of pollution sources and source-specific health risks of PM2.5-bound trace elements under long-term policies implementation, which in turn can not only gain insight into the substantive impact of policies, but also provide accurate guidance for future environmental management. In this study, winter PM2.5 samples were collected in Baoding City in northern China from 2016 to 2020, and variations in pollution sources and source-specific health risks of trace elements in PM2.5 were comprehensively analyzed. The results demonstrated that the concentrations of 10 elements displayed a declining trend, especially those of As, Sn, Zn, Sb, and Cd. By contrast, the concentration of Cr increased (except in 2020). Although the non-carcinogenic risk (NCR, including dust source) and carcinogenic risk (CR) from coal combustion and industrial emissions had decreased in the past five years, the NCR and CR still exceed the widely accept level for both adults and children in the winter of 2020. Coal combustion source was no longer the major contributor to the health risks caused by PM2.5-bound trace elements in winter, but vehicle related non-exhaust emissions have gradually become the main source of pollution.

Apportionment of Chemical Components and Sources of PM2.5 in Shihezi City of Xinjiang, China

In order to reveal the pollution characteristics and sources of PM2.5, in this study, we collected PM2.5 filter membrane samples in Shihezi continuously from December 2020 to January 2021, and analyzed 10 kinds of water-soluble inorganic ions (WSIIs) and 24 inorganic elements (IEs), as well as organic carbon (OC) and elemental carbon (EC). The sources and transport paths of PM2.5 were also analyzed via PMF modeling and backward trajectory clustering analysis. The results show that, in winter, Shihezi can have a mean PM2.5 mass concentration as high as 164.69 ± 76.48 μg/m3, and the PM2.5 mass concentration on polluted days is 3.3 times that of clean days. Water-soluble inorganic ions (WSIIs), total carbon (TC), and inorganic elements (IEs) make up the percentage of PM2.5 mass concentration by 64.9%, 9.3%, and 2.6%, respectively. SO42−, NO3−, and NH4+ (SIAs) are the major WSIIs, accounting for 91.0% of the WSII concentration. The heavier the pollution, the more SIAs contribute to PM2.5. The OC mean mass concentration is 14.04 ± 5.32 μg/m3. As the winter pollution becomes worse and worse, the value of OC/PM2.5 decreases constantly while that of SOC/OC follows an opposite trend. During the process of heavy pollution in Shihezi, the secondary transformation of total carbon cannot be ignored. The positive definite matrix factorization (PMF) model result suggests that the main pollution origins of PM2.5 in Shihezi City comprise secondary sources, coal-burning sources, motor vehicle sources, industrial sources, and flying dust sources. The backward trajectory clustering analysis denotes that the winter pollution in Shihezi mainly comes from the local pollutants in Manas and the short-distance transport of pollutants from the Urumqi-Changji Region.