Distribution, sources, and potential risk of polycyclic aromatic hydrocarbons in soils from an industrial district in Shanxi, China

Spatial distribution, environmental behavior, and health risk assessment of PAHs in soils at prototype coking plants in Shanxi, China: Stable carbon isotope and molecular composition analyses

To investigate the environmental behavior of and carcinogenic risk posed by 16 priority-controlled polycyclic aromatic hydrocarbons (PAHs), soil samples and air samples from the coke oven top were collected in two prototype coking plants (named PF and JD). The PF soils contained more PAHs than the JD soils because the PF plant employed the side-charging technique and had a lower coke oven height. The soils from both plants contained enough PAHs to pose a carcinogenic risk, and this risk was higher in the PF plant. Data were collected on the source characteristic spectrum of stable carbon isotopic composition (δ13C) of PAHs emitted from the coke oven top (δ13C values of -36.02‰ to -32.05‰ for gaseous PAHs and -34.09‰ to -25.28‰ for particulate PAHs), and these data fill a research gap and may be referenced for isotopic-technology-based source apportionment. Diagnostic ratios and isotopic technology revealed that the coking plant soils were mainly influenced by the coking process, followed by vehicle exhaust; the soils near the boundary of each plant were slightly affected by C3 plant burning. For most PAHs [excluding fluoranthene, benzo(k)fluoranthene, indeno(1,2,3-c,d)pyrene, and dibenzo(a,h)anthracene], the dominant migration process was the net volatilization of PAHs from soil to air. In the PF plant, 13C was depleted in gaseous PAHs during volatilization.

Impact of Atmospheric Conditions and Source Identification of Gaseous Polycyclic Aromatic Hydrocarbons (PAHs) during a Smoke Haze Period in Upper Southeast Asia

Gaseous polycyclic aromatic hydrocarbons were measured in northern Thailand. No previous studies have provided data on gaseous PAHs until now, so this study determined the gaseous PAHs during two sampling periods for comparison, and then they were used to assess the correlation with meteorological conditions, other pollutants, and their sources. The total concentrations of 8-PAHs (i.e., NAP, ACY, ACE, FLU, PHE, ANT, FLA, and PYR) were 125 ± 22 ng m-3 and 111 ± 21 ng m-3, with NAP being the most pronounced at 67 ± 18 ng m-3 and 56 ± 17 ng m-3, for morning and afternoon, respectively. High temperatures increase the concentrations of four-ring PAHs, whereas humidity and pressure increase the concentrations of two- and three-ring PAHs. Moreover, gaseous PAHs were estimated to contain more toxic derivatives such as nitro-PAH, which ranged from 0.02 ng m-3 (8-Nitrofluoranthene) to 10.46 ng m-3 (1-Nitronaphthalene). Therefore, they could be one of the causes of local people's health problems that have not been reported previously. Strong correlations of gaseous PAHs with ozone indicated that photochemical oxidation influenced four-ring PAHs. According to the Pearson correlation, diagnostic ratios, and principal component analysis, mixed sources including coal combustion, biomass burning, and vehicle emissions were the main sources of these pollutants.

Dissemination and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in water and sediment of Buriganga and Dhaleswari rivers of Dhaka, Bangladesh

Concentration, source, ecological and health risks of sixteen polycyclic aromatic hydrocarbons (PAHs) were estimated for water and sediment samples of two urban rivers namely Buriganga River (BR) and Dhaleswari River (DR). The mean concentration of ∑PAHs in BR water and sediment were 9619.2 ngL-1 and 351.6 ngg-1, respectively. Furthermore, the average PAH concentrations detected in DR water and sediment were 1979.1 ngL-1 and 792.9 ngg-1, respectively. The composition profile showed that 3-ring PAHs were dominant in the water matrix; however, 5-ring PAHs were prevalent in the sediment samples of both rivers. Sources apportion study of PAHs indicated that mixed combustion and petroleum sources are responsible for PAHs contamination in the rivers. Ecological risk study of water suggested that the aquatic lives of both rivers are threatened by Fla, BbF, BkF, DahA, and IcdP, as presented above the threshold level. Comparison with sediment quality guidelines (SQGs) indicated that adverse effects might cause occasionally in the sediment ecosystem in DR at certain sampling sites for Nap, Acy, Fl, Phe, Ant, Pyr, Chr, BaP, and DahA. On the other hand, the presence of Nap, Acy and DahA might occasionally cause adverse biological effects in the BR sediment ecosystem. Estimated hazard quotient (HI > 1) and carcinogenic risk (CRtotal > 10-4) values indicated that local inhabitants living in the vicinity of the rivers are prone to high health risks.

Investigation of the concentration, origin and health effects of PAHs in the Anzali wetland: The most important coastal freshwater wetland of Iran

This study investigated the concentration of PAHs in 19 water samples, 34 sediment samples and 22 fish samples of Anzali Wetland, located in north of Iran. The average concentration of ∑PAHs in the wetland sediment was 89.19 μg/kg (8.28-806.64) and 78.31 ng/L (5.14-253.37) in the wetland water. Also, the average concentration of ∑PAHS in the muscle of the investigated fish in the wetland was 23 μg/kg (56.1 to 7.6). The source apportionment of PAHs in water and sediment considering isomeric ratios and statistical methods reveals the predominance of petrogenic origin of the compounds in water and pyrogenic origin in sediment. Overall, the level of contamination in fish is relatively low to moderate, considering ∑PAHs. The findings present clear evidence of low to moderate level of contamination in the wetland, the PAHs contamination however could cross their ecological thresholds in future unless control measures are taken to protect the wetland.

Distribution and biodegradation potential of polycyclic aromatic hydrocarbons (PAHs) accumulated in media of a stormwater bioretention

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic compounds that can be captured and accumulate in the bioretention cell media, which may lead to secondary pollution and ecological risks. This research aimed to understand the spatial distribution of 16 priority PAHs in bioretention media, identify their sources, evaluate their ecological impact, and assess the potential for their aerobic biodegradation. The highest total PAH concentration (25.5 ± 1.7 μg/g) was observed 1.83 m from the inlet and 10-15 cm deep. The individual PAHs with the highest concentrations were benzo [g,h,i]perylene in February (1.8 ± 0.8 μg/g) and pyrene in June (1.8 ± 0.8 μg/g). Data indicated that primary sources of PAHs were fossil fuel combustion and petroleum. The ecological impact and toxicity of the media were assessed by probable effect concentrations (PECs) and benzo [a]pyrene total toxicity equivalent (BaP-TEQ). The results showed that the concentrations of pyrene and chrysene exceeded the PECs, and the average BaP-TEQ was 1.64 μg/g, primarily caused by benzo [a]pyrene. The functional gene (C12O) of PAH-ring cleaving dioxygenases (PAH-RCD) was present in the surface media, which indicated that aerobic biodegradation of PAHs was possible. Overall, this study revealed the PAHs accumulated most at medium distance and depth, where biodegradation may be limited. Thus, the accumulation of PAHs below the surface of the bioretention cell may need to be considered during long-term operation and maintenance.

Concentrations, phase exchanges and source apportionment of polycyclic aromatic hydrocarbons (PAHs) In Bursa-Turkey

The present study aimed to determine the pollution levels derived from polycyclic aromatic hydrocarbons (PAHs) in air, plant and soil samples and to reveal the PAH exchange at the soil-air, soil-plant and plant-air interfaces. In this context, air and soil samples were collected in approximately 10-day periods between June 2021 and February 2022 from a semi-urban area in Bursa, an industrial city with a dense population. Also, plant branch samples were collected for the last three months. Total PAH concentrations in the atmosphere (∑₁₆PAH) and soil (∑₁₄PAH) ranged from 4.03 to 64.6 ng/m³ and 13-189.4 ng/g DM, respectively. PAH levels in the tree branches varied between 256.6 and 419.75 ng/g DM. In all air and soil samples, PAH levels were low in the summer and reached higher values in the winter. 3-ring PAHs were the dominant compounds, and their distribution in air and soil samples varied between 28.9%-71.9% and 22.8%-57.7%, respectively. According to the results of diagnostic ratios (DRs) and principal component analysis (PCA), both pyrolytic and petrogenic sources were found to be effective in PAH pollution in the sampling region. The fugacity fraction (ff) ratio and net flux (F_net) values indicated that the direction of movement of PAHs was from soil to air. In order to better understand the PAH movement in the environment, soil-plant exchange calculations were also achieved. The ratio of ∑₁₄PAH values measured to modeled concentrations (1.19<ratio<1.52) revealed that the model worked well for the sampling region and produced reasonable results. The ff and F_net levels showed that branches were saturated with PAHs and the direction of PAH movement was from plant to soil. The plant-air exchange results indicated that the direction of movement of PAHs was from plant to air for low molecular weight PAHs and the opposite was true for compounds with high molecular weight ones.

Effects of biodegradable and non-biodegradable microplastics on bacterial community and PAHs natural attenuation in agricultural soils

Anthropogenic activities such as in situ straw incineration and the widespread use of agricultural film led to the accumulation of polycyclic aromatic hydrocarbons (PAHs) and microplastics (MPs) in agricultural soils. In this study, four biodegradable MPs (BPs), including polylactic acid (PLA), polybutylene succinate (PBS), poly-β-hydroxybutyric acid (PHB) and poly (butylene adipate-co-terephthalate) (PBAT) and non-biodegradable low-density polyethylene (LDPE) were selected as representative MPs. The soil microcosm incubation experiment was conducted to analyze MPs effects on PAHs decay. MPs did not influence PAHs decay significantly on day 15 but showed different effects on day 30. BPs reduced PAHs decay rate from 82.4% to 75.0%- 80.2% with the order of PLA < PHB < PBS < PBAT while LDPE increased it to 87.2%. MPs altered beta diversity and impacted the functions to different extents, interfering in PAHs biodegradation. The abundance of most PAHs-degrading genes was increased by LDPE and decreased by BPs. Meanwhile, PAHs speciation was influenced with bioavailable fraction elevated by LDPE, PLA and PBAT. The facilitating effect of LDPE on 30-d PAHs decay can be attributed to the enhancement of PAHs-degrading genes and PAHs bioavailability, while the inhibitory effects of BPs were mainly due to the response of the soil bacterial community.

Spatial Distribution, Potential Sources, and Health Risk of Polycyclic Aromatic Hydrocarbons (PAHs) in the Surface Soils under Different Land-Use Covers of Shanxi Province, North China

Polycyclic aromatic hydrocarbons (PAHs) are widespread in the environment and pose a serious threat to the soil ecosystem. In order to better understand the health risks for residents exposed to PAH-contaminated soil, 173 surface soil samples were collected in Shanxi Province, China, to detect the levels of 16 priority PAHs. The spatial distribution patterns of PAHs were explored using interpolation and spatial clustering analysis, and the probable sources of soil PAHs were identified for different land-use covers. The results indicate that the soil Σ16 PAH concentration ranged from 22.12 to 1337.82 ng g^-1, with a mean of 224.21 ng g^-1. The soils were weakly to moderately contaminated by high molecular weight PAHs (3-5 ring) and the Taiyuan-Linfen Basin was the most polluted areas. In addition, the concentration of soil PAHs on construction land was higher than that on other land-use covers. Key sources of soil PAHs were related to industrial activities dominated by coal burning, coking, and heavy traffic. Based on the exposure risk assessment of PAHs, more than 10% of the area was revealed to be likely to suffer from high carcinogenic risks for children. The study maps the high-risk distribution of soil PAHs in Shanxi Province and provides PAH pollution reduction strategies for policy makers to prevent adverse health risks to residents.

Multicompartmental analysis of POPs and PAHs in Concepciόn Bay, central Chile: Part I - Levels and patterns after the 2010 tsunami

Persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) were determined in abiotic samples from Concepción Bay in Central Chile. Samples were soxhlet extracted and injected in gas chromatography-mass spectrometry (GCMS). Polybrominated diphenyl ethers (PBDEs) showed the highest levels in air (3-1100 pg m^-3), in water (2-64 pg L^-1), in sediment, and soil (1-78 ng g^-1 (dw)). PAHs were also high in the air (1-6 ng m^-3), in water (1-7 ng L^-1), in sediment (90-300 ng g^-1 (dw)), and in soil (15-2300 ng g^-1 (dw)). The polychlorinated biphenyls (PCBs) and chlorinated pesticides were generally low and did not show clear trends along the water column, with exception of PAHs. New data are presented in this work to assess the health status of a relevant coastal area in central Chile.

Cancer risk assessment of soils contaminated by polycyclic aromatic hydrocarbons in Shanxi, China

To assess the human cancer risk exposed to soil contaminated by polycyclic aromatic hydrocarbons (PAHs) in Shanxi province, China, the total 33 samples in the surface soil were collected from 11 cities, and the priority 15 PAHs were analyzed using gas chromatography-mass spectrometry after the soxhlet extraction and silica-alumina column purification. As a result, the levels of ∑₁₅PAH in soil varied from 66.2 to 2633 ng/g dry weight (dw) with a mean of 732 ng/g dw, and seven carcinogenic PAHs made up 42-69% of the total priority PAHs and had an average value of 367 (in the range of 33.2 to 1181) ng/g dw. Accordingly, the total concentrations of benzo[a]pyrene equivalents (BaP_eq) for 15 PAHs ranged from 10.3 to 358 (average 98.3) ng/g dw, and the seven carcinogenic BaP_eq accounted for above 90%. Subsequently, the possible sources of PAHs in soil were identified by isomer ratios, demonstrating that the combustion contributed to the main source. Finally, the incremental lifetime cancer risks (ILCR) of soil contaminated by 15 priority PAHs were estimated using the targeted chemical-specific approach. ILCR values were considered to be greater than 1 × 10^-6 in 16 of 33 sites and followed a decreasing trend of adulthood > childhood > adolescence. Subsequently, the analysis of variance was performed by average ILCR value among the 11 cities (n = 3, p < 0.01), which indicated that the potential low cancer risk significantly increased for nearby residents in two areas, including Datong and Xinzhou, with the ILCR values of 4.61 ± 1.93 and 3.92 ± 2.54 per million, respectively. Therefore, the consumption of traditional coal should be controlled and partially replaced with the alternative energy sources. And the rigorous monitoring should be termly warranted to avoid the cancer risk for human being in agricultural area of Shanxi, China.

Polycyclic aromatic hydrocarbon (PAHs) geographical distribution in China and their source, risk assessment analysis

In China, the huge amounts of energy consumption caused severe carcinogenic polycyclic aromatic hydrocarbon (PAHs) concentration in the soil and ambient air. This paper summarized that the references published in 2008-2018 and suggested that biomass, coal and vehicular emissions were categorized as major sources of PAHs in China. In 2016, the emitted PAHs in China due to the incomplete combustion of fuel was about 32720 tonnes, and the contribution of the emission sources was the sequence: biomass combustion > residential coal combustion > vehicle > coke production > refine oil > power plant > natural gas combustion. The total amount of PAHs emission in China at 2016 was significantly decreased due to the decrease of the proportion of crop resides burning (indoor and open burning). The geographical distribution of PAHs concentration demonstrated that PAHs concentration in the urban soil is 0.092-4.733 μg/g. At 2008-2012, the serious PAHs concentration in the urban soil occurred in the eastern China, which was shifted to western China after 2012. The concentration of particulate and gaseous PAHs in China is 1-151 ng/m3 and 1.08-217 ng/m3, respectively. The concentration of particle-bound PAHs in the southwest and eastern region are lower than that in north and central region of China. The incremental lifetime cancer risk (ILCR) analysis demonstrates that ILCR in the soil and ambient air in China is below the acceptable cancer risk level of 10-6 recommended by US Environmental Protection Agency (EPA), which mean that there is a low potential PAHs carcinogenic risk for the soil and ambient air in China.

Comparison of PAH content, potential risk in vegetation, and bare soil near Daqing oil well and evaluating the effects of soil properties on PAHs

As the largest oil field in China, Daqing oil field has been developed in the past six decades. The objectives of this study were to measure the levels of polycyclic aromatic hydrocarbons (PAHs) and assess their ecological risk of PAHs in vegetation soil and bare soil near oil well in Daqing and surrounding soil. Ten sites were selected from two types of soil in grassland: vegetation soil (VS, n = 5) and bare soil (BS, n = 5). The mean concentration of 16 PAHs (∑₁₆ PAHs) was 2240.2 μg/kg. The mean concentrations of eight carcinogenic PAHs (∑_8c PAHs) was 1312.3 μg/kg which accounts for 59% of ∑₁₆ PAHs. The sampling sites had higher proportions of high weight molecular ringed PAHs with higher proportions of benzo (a) pyren (BaP) and benzo (k) fluoranthene (BkF). The main source of PAHs was petroleum, coal/biomass combustion, and vehicular emission in these sampling sites. According to Canadian soil quality guidelines, 60% sites had a significant risk to human health. Moreover, 50% sites had high ecological risk and 30% sites were close to this critical value. Notably, PAH levels were significantly higher in VS than BS; moreover, VS had higher organic matter (OM) content, soil dehydrogenase (sDHA) activity, and lower pH and salt content. A structural equation model was established to explore the effects of soil properties on PAH concentration in VS. The result revealed that OM and sDHA were meaningful to enhance the adsorption and biological fixation of PAHs. This study will provide basic information on PAH level and potential application for phytoremediation.

Polycyclic aromatic hydrocarbons in urban road dust, Afghanistan: Implications for human health

Polycyclic aromatic hydrocarbons (PAHs) were analyzed in road and aerial dust to assess their concentration, composition profile, distribution, emission sources, and potential human health risks. Sixteen priority PAHs and Benzo [e]pyrene (BeP) were analyzed in 13 aerial dust samples from Jalalabad, and 78 road dust samples from Kabul and Jalalabad cities, Afghanistan. The mean concentration of ∑17PAHs in road dust from Kabul and Jalalabad were 427  μg kg^-1 and 288  μg kg^-1, respectively whereas ∑17PAHs in aerial dust from Jalalabad averaged 200  μg kg^-1. Fluoranthene (Flu), Chrysene (Chr), Benzo [b]fluoranthene (BbF), Benzo [k]fluoranthene (BkF) and BeP were major individual PAH species. The composition patterns of the PAHs were dominated by 5-6-ring PAHs (51% in road dust from Kabul; 44% in road dust from Jalalabad; and 44% in aerial dust) followed by 4-ring and 2-3-ring PAHs. Source apportionment of the road dust PAHs by the molecular diagnostic ratios (MDR) and principal component analysis (PCA), indicated signatures of PAHs sources (including vehicular exhaust, coal/wood combustion and oil spill). The Benzo [a]pyrene (BaP) toxicity equivalent values (BaP_eq17PAHs) for road dust were 75  μg kg^-1 (Kabul) and 36 μg kg^-1 (Jalalabad); and 35 μg kg^-1 for aerial dust (Jalalabad). BaP and Dibenz [a,h]anthracene (DahA) together contributed > 50% of the BaP_eq associated cancer risk. All incremental lifetime cancer risk (ILCR) due to human exposure to road and aerial dust PAHs were in the order of 10^-7, which is one-fold lower than the threshold (10^-6). The noncancerous risk (Hazard Index < 1) on exposure to dust was also negligible for both subpopulations.

Contamination and health risk assessment of PAHs in farmland soils of the Yinma River Basin, China

The concentration, composition, sources and incremental lifetime cancer risk of farmland soil polycyclic aromatic hydrocarbons (PAHs) of the Yinma River Basin were analyzed. In 2016, the total concentration of 16 PAHs ranged from 491.65 to 1007.73 ng/g in May, from 427.31 to 781.38 ng/g in August and from 580.40 to 999.40 ng/g in November, respectively. Levels of seven potentially carcinogenic PAHs generally accounted for 33-36.7% of total 16 PAHs in three seasons, and the PAHs contained two to six rings, mainly Fla, Pyr, and Chr. The correlation analysis suggested that the soil organic matter (SOM) was no correlation with PAHs except for August, and there were no significant relationship between the pH and total PAHs. Isomer ratios indicated that the soil PAHs in the farmland of the Yinma River Basin was determined to be the combustion of coal, biomass, and petroleum. The toxic equivalent (BaP_eq) concentrations ranged from 15.2 to 133 ng BaP_eq g^-1 in three seasons. The 95th percentiles of incremental lifetime cancer risk (ILCR) due to human exposure to farmland soil PAHs of the Yinma River Basin was (1.36 × 10^-6) in May, (1.00 × 10^-6) in August, and (1.18 × 10^-6) in November for children, (1.10 × 10^-6) in May, (8.15 × 10^-7) in August, and (9.58 × 10^-7) in November for adolescence and (1.61 × 10^-6) in May, (4.22 × 10^-6) in August and (1.40 × 10^-6) in November for adulthood. The result indicated a moderate carcinogenic risk and the risk of exposure to farmland soil PAHs was pervasive for residents. This investigation might provide useful information on human exposure to PAHs in soil of the Yinma River Basin, and is valuable for policy makers and scientists.

Polycyclic aromatic hydrocarbons in house dust and surface soil in major urban regions of Nepal: Implication on source apportionment and toxicological effect

Urban centers have turned to be the provincial store for resource consumptions and source releases of different types of semi-volatile organic compounds (SVOCs) including polycyclic aromatic hydrocarbons (PAHs), bringing about boundless environmental pollutions, among different issues. Human prosperity inside urban communities is unambiguously dependent on the status of urban soils and house dusts. However, environmental occurrence and sources of release of these SVOCs are challenging in Nepalese cities, as exceptionally very limited data are accessible. This motivated us to explore the environmental fate, their source/sink susceptibilities and health risk associated with PAHs. In this study, we investigated the contamination level, environmental fate and sources/sink of 16 EPA's priority pollutants in surface soil and house dusts from four major cities of Nepal. Additionally, the toxicological effect of individual PAH was studied to assess the health risk of PAHs. Generally, the concentrations of ∑₁₆PAHs in surface soil were 1.5 times higher than house dust, and ranged 767-6770ng/g dry weight (dw) (median 1810ng/g dw), and 747-4910 dw (median 1320ng/g dw), respectively. High molecular weight-PAHs both in soil and dust were more abundant than low molecular weight-PAHs, suggesting the dominance of pyrogenic source. Moderate to weak correlation of TOC and BC with PAHs in soil and dust suggested little or no role of soil organic carbon in sorption of PAHs. Source diagnostic ratio and principal component analysis indicated fossil fuel combustion, traffic/vehicular emissions and combustion of biomass are the principal sources of PAHs contamination in Nepalese urban environment. The high average TEQ value of PAHs in soil than dust suggested high risk of soil carcinogenicity compared to dust.

Distribution, sources, and toxicity assessment of polycyclic aromatic hydrocarbons in surface soils of a heavy industrial city, Liuzhou, China

As a heavy industrial city, Liuzhou has been facing a serious pollution problem. It is necessary to take steps to control and prevent environmental pollution wherever possible. Surface soil samples were collected from four communities in Liuzhou City, to determine the concentrations, distributions, sources, and toxicity potential of polycyclic aromatic hydrocarbons (PAHs) present. The mean concentrations of total PAHs in the surface soil are 756.43 ng/g for the heavy industrial area, 605.06 ng/g for the industrial area, 481.24 ng/g for the commercial-cum-residential area, and 49.93 ng/g for the rural area. Both the isomer ratio and principal component analyses for the PAHs prove that these pollutants originate mainly from coal, diesel, gasoline, and natural gas combustion. The pollution hierarchies and toxic equivalency factor of BaP prove that the city is subject to heavy pollution caused by industry, transportation, and daily human activities.