Soil polycyclic aromatic hydrocarbons (PAHs) generated from industrial processes are highly spatially heterologous, with limited quantitative studies on their main influencing factors. The present study evaluated the soil PAHs in three types of industrial parks (a petrochemical industrial park, a brominated flame retardant manufacturing park, and an e-waste dismantling park) and their surroundings. The total concentrations of 16 PAHs in the parks were 340–2.43 × 10³, 26.2–2.63 × 10³, and 394–2.01 × 10⁴ ng/g, which were significantly higher than those in the surrounding areas by 1–2 orders of magnitude, respectively. The highest soil PAH contamination was observed in the e-waste dismantling park. Nap can be considered as characteristic pollutant in the petrochemical industrial park, while Phe in the flame retardant manufacturing park and e-waste dismantling park. Low molecular weight PAHs (2–3 rings) predominated in the petrochemical industrial park (73.0%) and the surrounding area of brominated flame retardant manufacturing park (80.3%). However, high molecular weight PAHs (4–6 rings) were enriched in the other sampling sites, indicating distinct sources and determinants of soil PAHs. Source apportionment results suggested that PAHs in the parks were mainly derived from the leakage of petroleum products in the petroleum manufacturing process and pyrolysis or combustion of fossil fuels. Contrarily, the PAHs in the surrounding areas could have been derived from the historical coal combustion and traffic emissions. Source emissions, wind direction, and local topography influenced the PAH spatial distributions.

The health effects of potentially toxic elements (PTEs) in airborne particulate matter (PM) are strongly dependent on their size distribution and dissolution. This study examined PTEs within nine distinct sizes of PM in a Chinese megacity, with a focus on their deposited and dissolved bioaccessibility in the human pulmonary region. A Multiple Path Particle Dosimetry (MPPD) model was used to estimate the deposited bioaccessibility, and an in-vitro experiment with simulated lung fluid was conducted for dissolved bioaccessibility. During the non-heating season, the dissolved bioaccessible fraction (DBF) of As, Cd, Co, Cr, Mn, Pb and V were greater in fine PM (aerodynamics less than 2.1 μm) than in coarse PM (aerodynamics between 2.1 and 10 μm), and vice versa for Ni. With the increased demand of heating, the DBF of Pb and As decreased in fine particle sizes, probably due to the presence of oxide/silicate compounds from coal combustion. Inhalation health risks based on the bioaccessible concentrations of PTEs displayed the peaks in <0.43 μm and 2.1–3.3 μm particulate sizes. The non-cancer risk was at an acceptable level (95th percentiles of hazard index (HI) was 0.49), but the cancer risk exceeded the threshold value (95th percentiles of total incremental lifetime cancer risk (TCR) was 8.91 × 10⁻⁵). Based on the results of uncertainty analysis, except for the exposure frequency, the total concentrations and DBF of As and Cr in <0.43 μm particle size segment have a greater influence on the uncertainty of probabilistic risk.

Inhalation of respirable silica particles can cause serious lung diseases (e.g., silicosis and lung cancer), and the toxicity of respirable silica is highly dependent on its crystal form. Common combustion processes such as coal and biomass burning can provide high temperature environments that may alter the crystal forms of silica and thus affect its toxic effects. Although crystalline silica (i.e., quartz, tridymite, and cristobalite) were widely found at different temperatures during the burning processes, the sources and crystal transformation pathways of silica in the burning processes are still not well understood. Here, we investigate the crystal transformation of silica in the coal and biomass combustion processes and clarify the detailed transformation pathways of silica for the first time. Specifically, in coal burning process, amorphous silica can transform into quartz and cristobalite starting at 1100 °C, and quartz transforms into cristobalite starting at 1200 °C; in biomass burning process, amorphous silica can transform into cristobalite starting at 800 °C, and cristobalite transforms into tridymite starting at 1000 °C. These transformation temperatures are significantly lower than those predicted by the classic theory due to possibly the catalysis of coexisting metal elements (e.g., aluminum, iron, and potassium). Our results not only enable a deeper understanding on the combustion-induced crystal transformation of silica, but also contribute to the mitigation of population exposure to respirable silica.

Many studies revealed the rapid decline of atmospheric PM₂.₅ in Beijing due to the emission control measures. The variation of particle number concentration (PN) which has important influences on regional climate and human health, however, was rarely reported. This study measured the particle number size distributions (PNSD) in 3–700 nm in winter of Beijing during 2013–2019. It was found that PN decreased by 58% from 2013 to 2017, but increased by 29% from 2017 to 2019. By Positive matrix factorization (PMF) analysis, five source factors of PNSD were identified as Nucleation, Fresh traffic, Aged traffic + Diesel, Coal + biomass burning and Secondary. Overall, factors associated with primary emissions were found to decrease continuously. Coal + biomass burning dominated the reduction (65%) among the three primary sources during 2013–2017, which resulted from the great efforts on emission control of coal combustion and biomass burning. Fresh traffic and Aged traffic + Diesel decreased by 43% and 66%, respectively, from 2013 to 2019, as a result of the upgrade of the vehicle emission standards in Beijing-Tianjin-Hebei area. On the other hand, the contribution from Nucleation and Secondary decreased with the reduction of gaseous precursors in 2013–2017, but due to the increased intensity of new particle formation (NPF) and secondary oxidation, they increased by 56% and 70%, respectively, from 2017 to 2019, which led to the simultaneously increase of PN and particle volume concentration. This study indicated that NPF may play an important role in urban atmosphere under continuous air quality improvement.

Trace metal (loid) contamination in the atmosphere is widely monitored, but there is a gap in understanding its long-term patterns, especially in North China, which is currently a global contamination hotspot mainly caused by heavy industry emissions and coal combustion. Herein, historical trends of atmospheric As, Cd, Cr, Cu, Hg, Ni, Pb and Zn contamination in North China over the past ∼500 years are comparatively studied with sediment cores from two subalpine lakes (Gonghai and Muhai). Arsenic, Pb, Cd and Hg were main pollutants according to Pb isotopes and enrichment factors. Mercury contamination has increased continuously since the late 1800s and increasing As, Pb and Cd contamination started in the 1950s in Gonghai. In contrast, the contamination in Muhai lagged two decades for As, Cd and Pb and a half-century for Hg behind that in Gonghai, although the trends were similar. This contamination lag was attributed to the low sensitivity of Muhai sediment to early weak atmospheric metal contamination under 2.1-fold higher detrital sedimentation. As, Pb and Cd contamination has intensified since the 1980s, and the metals showed similar sedimentary fluxes in the cores. However, sedimentary fluxes of Hg contamination were 3.4-fold higher in Gonghai than in Muhai due to combination with organic matter. No obvious Cr, Cu and Ni contamination in the cores was mainly because of the low atmospheric deposition from anthropogenic sources relative to detrital input, although some of their atmospheric emissions were higher than those of As, Cd and Hg. Atmospheric As, Pb and Cd contamination was mainly from domestic sources of coal combustion and nonferrous smelting. Mercury contamination was mainly from global and Asian sources in the first half of the 20th century, and domestic emissions gradually dominated Hg contamination after the mid-1900s.

The diurnal variation, gas-particle partitioning, health risks, and sources of polycyclic aromatic hydrocarbons (PAHs) were investigated in a northern basin city of China in winter, 2020. The mean concentrations of particulate and gaseous PAHs were 87.90 ng m⁻³ and 69.65 ng m⁻³, respectively, and their concentrations were considerably enhanced during the domestic heating period. The relationship between the gas-particle partitioning coefficient of PAHs (KP) and subcooled liquid vapor pressure of PAHs (PL⁰) indicated organic absorption as the mechanism for this partitioning. However, the dual sorption model confirmed adsorption onto elemental carbon (EC). The health risks indicated by several equivalent parameters showed an important health effect of PAHs, especially of particulate PAHs bound onto PM₂.₅ during the heating period. Environmentally persistent free radicals (EPFRs) were also studied as an auxiliary parameter to evaluate the health impact of PAHs. According to the diagnostic ratios of PAHs and PMF model results, petroleum volatilization and coal combustion were the dominant sources of particulate PAHs during the non-heating and heating periods, respectively. The source apportionment results can help efficiently control PAHs and their health risks.

Dust is regarded as an important pathway of heavy metal(loid)s to the human body. Health risks posed by metal(loid)s from household dust are of particular concern. However, the contamination and sources of heavy metal(loid)s in household dust environments, as well as source identification of health risks related to heavy metal(loid)s from household dust for vulnerable populations such as children, have not been thoroughly studied in China, particularly for the areas involved with industrial activities such as ore mining. Thus, a cross-sectional study was conducted in a rural area famous for Pb/Zn ore mining, to assess the pollution sources and health risks of heavy metal(loid)s from household indoor and outdoor dust and to identify the contribution of household dust to the health risks for children. The results indicated that household environment was heavily contaminated by metal(loid)s, which were mainly attributed to mining activity. Meanwhile, the indoor/outdoor ratio and the redundancy analysis indicated that there were other pollution sources in indoor environments such as coal combustion, materials for interior building and decoration. Vapor inhalation was the main exposure pathway for Hg, while ingestion was the predominant pathway for other metal(loid)s. Although the cancer risks were relatively low, the HIt from household indoor and outdoor dust (2.19) was about twice the acceptable limit (1) and was primarily from Pb (64.52%) and As (23.42%). Outdoor dust was a larger contributor to the HI of Sb, As, Cr, Cd, Zn and Pb, which accounted for 51.37%, 58.63%, 52.14%, 59.66%, 52.87% and 64.47%, respectively, and the HIt was mainly from outdoor dust (60.76%). These results indicated that non-cancer health risks were largely from outdoor dust exposure, and strengthened the notion that concern should be given to the potential health risks from metal(loid)s in household dust both originating from mining activity and indoor environmental sources.

The most prominent source of Cu contamination in soils is metal mining and processing, partly since the Middle Age. However, coal mining and combustion can also cause (some) Cu contamination. We studied the distribution of Cu concentrations and isotope ratios in soils of the Huaibei coal mining area. The contribution of the coal mining and combustion to total Cu concentrations in soil was determined with a two-end-member mixing model based on the distinct δ⁶⁵Cu values of the Cu emitted from coal mining and combustion and in native soil. The mean Cu concentration of 75 mg kg⁻¹ exceeded the local soil background value (round to 22.13 mg kg⁻¹). The similar δ⁶⁵Cu value of grass near the coal mining and combustion operation as in gangue and flying ash indicated a superficial Cu contamination. Mining input was the dominant source of Cu in the contaminated soils, contributing up to 95% and on average 72% of the total Cu in the topsoils. The mining-derived Cu was leached to a depth of 65 cm, where still 29% of the Cu could be attributed to the mining emissions. Grasses showed lower δ⁶⁵Cu values than the topsoils, because of the preferential uptake of light Cu isotopes. However, the Δ⁶⁵Cugᵣₐₛₛ₋ₛₒᵢₗ was lower in the contaminated than the uncontaminated area because of superficial adsorption of isotopically heavy Cu from the mining emissions. Overall, in this study the distinct δ⁶⁵Cu values of the mining-derived Cu emissions and the native soil allowed for the quantification of the mining-derived Cu and had already reached the subsoil and contaminated the grass by superficial adsorption in only 60 years of mining operation.

Twenty-five years after the first look at polycyclic aromatic compounds (PACs) in Canada, this article presents current knowledge on Canadian PAC emission sources. The analysis is based on national inventories (the National Pollutant Release Inventory (NPRI) and the Air Pollutant Emissions Inventory (APEI)), an analysis of Canadian forest fires, and several air quality model-ready emissions inventories. Nationally, forest fires continue to dominate PAC emissions in Canada, however there is uncertainty in these estimates. Though forest fire data show a steady average in the total annual area burned historically, an upward trend has developed recently. Non-industrial sources (home firewood burning, mobile sources) are estimated to be the second largest contributor (∼6-8 times lower than forest fires) and show moderate decreases (25%–65%) in the last decades. Industrial point sources (aluminum production, iron/steel manufacturing) are yet a smaller contributor and have seen considerable reductions (90% +) in recent decades. Fugitive emissions from other industrial sources (e.g. disposals by the non-conventional oil extraction and wastewater sectors, respectively) remain a gap in our understanding of total PAC emissions in Canada. Emerging concerns about previously unrecognized sources such as coal tar-sealed pavement run-off, climate change are discussed elsewhere in this special issue. Results affirm that observations at the annual/national scale are not always reflective of regional/local or finer temporal scales. When determining which sources contribute most to human and ecosystem exposure in various contexts, examination at regional and local scales is needed. There is uncertainty overall in emissions data stemming in part from various accuracy issues, limitations in the scope of the various inventories, and inventory gaps, among others.

The Yangtze River Delta (YRD) is one of the fastest developing areas in eastern China and contains many chemical industry parks. The profiles and sources of polycyclic aromatic hydrocarbons (PAHs) in soil in chemical industry parks and surrounding areas in the YRD were investigated by analyzing soil samples (n = 64) were collected in the YRD and Rudong chemical park (RD), a typical chemical park in the Yangtze River Delta. The total concentrations of 19 PAHs in the YRD soil samples were 16.3–4694 ng g⁻¹ (mean 688 ng g⁻¹), and the total concentrations of PAHs in RD were 21.6–246 ng g⁻¹ (mean 75.4 ng g⁻¹). The PAHs in soil in YRD were dominated by four-ring and five-ring PAHs, and the PAHs in RD were dominated by two-ring and three-ring PAHs. It suggested that PAHs may have been supplied to soil in YRD predominantly through coal combustion and vehicle emissions, PAHs in the soil of RD may be due to the volatilization and leakage of chemical raw material. According to the different distribution characteristics of PAHs, the ratio (1.5) of (2 + 3) rings/4 rings was proposed to identify the chemical source of PAHs. The PAH isomer ratios and principal component analysis/multiple linear regression (PCA/MLRA) results indicated that PAHs concentrations in soil in the YRD and RD are mainly supplied by industrial and traffic emissions. Incremental lifetime cancer risks (ILCRs) indicated that PAHs in soil pose negligible cancer risks to children and adults, but much stronger risks to children than adults.