Polycyclic aromatic hydrocarbons in soils from Urumqi, China: distribution, source contributions, and potential health risks

Biodiversity of multi-trophic biological communities within riverine sediments impacted by PAHs contamination and land use changes

River ecosystems currently face a significant threat of degradation and loss of biodiversity resulting from continuous emissions of persistent organic pollutants and human activities. In this study, multi-trophic communities were assessed using DNA metabarcoding in a relatively stable riverine sediment compartment to investigate the biodiversity dynamics in the Beiluo River, followed by an evaluation of their response to polycyclic aromatic hydrocarbons (PAHs) and land use changes. A total of 48 bacterial phyla, 4 fungal phyla, 4 protist phyla, 9 algal phyla, 31 metazoan phyla, and 12 orders of fish were identified. The total concentration of PAHs in the Beiluo River sediments ranged from 25.95 to 1141.35 ng/g, with low molecular weight PAHs constituting the highest proportion (68.67%), followed by medium (22.19%) and high (9.14%) molecular weight PAHs. Notably, in contrast to lower trophic level aquatic communities such as bacteria, algae, and metazoans, PAHs exhibited a significant inhibitory effect on fish. Furthermore, the diversity of aquatic communities displayed obvious heterogeneity across distinct land use groups. A high proportion of cultivated land reduced the biodiversity of fish communities but increased that of metazoans. Conversely, an elevated proportion of built-up land reduced metazoan biodiversity, while simultaneously enhancing that of fungi and bacteria. Generally, land use changes exert both indirect and direct effects on aquatic communities. The direct effects primarily influence the abundance of aquatic communities rather than their diversity. Nevertheless, PAHs pollution may have limited potential to disrupt community structures through complex species interactions, as the hub species identified in the co-occurrence network did not align with those significantly affected by PAHs. This study indicates the potential of PAHs and land use changes to cause biodiversity losses. However, it also highlights the possibility of mitigating these negative effects in riverine sediments through optimal land use management and the promotion of enhanced species interactions.

Seasonal variation and concentration of PAHs in Lake Balaton sediment: A study on molecular weight distribution and sources of pollution

The temporal and spatial variations of 16 Polycyclic Aromatic Hydrocarbons (PAHs) were examined at multiple sites around Lake Balaton from February 2023 to January 2024. The results indicated that the concentrations of PAHs in sediment were high during the winter months, 448.35 to 619.77 ng/g dry weight, and low during the summer months, 257.21 to 465.49 ng/g dry weight. The concentration of high molecular weight PAHs (HMWPAHs), consisting of 5-6 rings, was greater than that of low molecular weight PAHs (LMWPAHs), which had 2-3 rings. The total incremental lifetime cancer risk (ILCR) for both dermal and ingestion pathways was high for both adults and children during the four seasons, with the highest records as the following: winter > spring > summer > autumn. The ecological effects of the 16 PAHs were negligible except for acenaphthylene (Acy) and fluorene (Fl), which displayed slightly higher concentrations during the autumn and spring, respectively.

Temporal and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in the Danube River in Hungary

The Danube is a significant transboundary river on a global scale, with several tributaries. The effluents from industrial operations and wastewater treatment plants have an impact on the river's aquatic ecosystem. These discharges provide a significant threat to aquatic life by deteriorating the quality of water and sediment. Hence, a total of 16 Polycyclic Aromatic Hydrocarbons (PAHs) compounds were analyzed at six locations along the river, covering a period of 12 months. The objective was to explore the temporal and spatial fluctuations of these chemicals in both water and sediment. The study revealed a significant fluctuation in the concentration of PAHs in water throughout the year, with levels ranging from 224.8 ng/L during the summer to 365.8 ng/L during the winter. Similarly, the concentration of PAHs in sediment samples varied from 316.7 ng/g in dry weight during the summer to 422.9 ng/g in dry weight during the winter. According to the Europe Drinking Water Directive, the levels of PAHs exceeded the permitted limit of 100 ng/L, resulting in a 124.8% rise in summer and a 265.8% increase in winter. The results suggest that the potential human-caused sources of PAHs were mostly derived from pyrolytic and pyrogenic processes, with pyrogenic sources being more dominant. Assessment of sediment quality standards (SQGs) showed that the levels of PAHs in sediments were below the Effect Range Low (ERL), except for acenaphthylene (Acy) and fluorene (Fl) concentrations. This suggests that there could be occasional biological consequences. The cumulative Individual Lifetime Cancer Risk (ILCR) exceeds 1/104 for both adults and children in all sites.

Characteristics, sources, bio-accessibility, and health risks of organophosphate esters in urban surface dust, soil, and dustfall in the arid city of Urumqi in China

Sixty-eight paired samples of urban surface dust and soil as well as four samples of atmospheric dustfall were collected from the arid city of Urumqi in Northwest China. Thirteen organophosphate esters (OPEs) in these samples were analyzed for the characteristics, sources, bio-accessibility, and health risks of OPEs. The studied OPEs were widely detected in the urban surface dust, soil, and dustfall, with Σ13OPEs (total concentration of 13 OPEs) of 1362, 164.0, and 1367 ng/g, respectively, dominated by tris(2-chloroethyle) phosphate (TCEP), tri(2-chloroisopropyl) phosphate (TCiPP), tri(1, 3-dichloroisopropyl) phosphate (TDCiPP) and tris(2-butoxyethyl) phosphate (TBOEP), TBOEP and tri(2-ethylhexyl) phosphate (TEHP), and TCEP, TCiPP, TBOEP, triphenyl phosphate and TEHP, respectively. The low and high frequency magnetic susceptibility of surface dust and urban soil might indicate the pollution of OPEs in them. Elevated levels of the Σ13OPEs in the surface dust and urban soil were found in the west, south, and northeast of Urumqi city. The total deposition flux of dustfall-bound 13 OPEs ranged from 86.5 to 143 ng/m2/day, with a mean of 105 ng/m2/day. OPEs in the surface dust and urban soil were associated with the emissions of indoor and outdoor products containing OPEs, the dry and wet deposition of atmosphere, and the emissions of traffic. Trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tri-isobutyl phosphate, TCEP, TCiPP, TDCiPP, and TBOEP in surface dust and urban soil had relatively high bio-accessibility. The bio-accessibility of OPEs was mainly affected by the physio-chemical properties of OPEs. The non-cancer and cancer risks of human exposure to OPEs in surface dust and urban soil were relatively low or negligible. The current research results may provide scientific supports for prevention and control of pollution and risks of OPEs.

Distribution and source identification of polycyclic aromatic hydrocarbons (PAHs) with PCA-MLR and PMF methods in the topsoil of Chengdu at SW, China

In spite of extensive studies on the features of polycyclic aromatic hydrocarbons (PAHs) as typical persistent organic pollutants (POPs) in cities, lack of understanding on the distribution and source characteristics of PAHs in big city with basin climate that can easily accelerate the pollution. Therefore, we sampled and analyzed PAHs from forty-five topsoil samples evenly distributed in Chengdu and the data shows that: (1) concentrations of ∑16PAHs in the study area ranged from 88.56 to 4448.34 ng/g, with a mean value of 739.07 ng/g, which is a lower level compared to similar cities, the distribution and proportion of LMW-PAHs show that the migration of pollution is blocked by the topography of the basin; (2) principal component analysis-multiple linear regression (PCA-MLR) and positive matrix factorization (PMF) indicated that combustion of fossil fuels and biomass is the most important source of PAHs in Chengdu; (3) the toxic equivalency factors of benzo[a]pyrene indicated a low risk of ∑16PAHs in all areas in Chengdu; (4) the inherited lifetime carcinogenic risk (ILCR) showed a relatively low level of potential risk in the region, while female inhabitants in several regions seem to suffer from higher health risks. Overall, our case study of PAHs in the topsoil at Chengdu city at SW China indicates that the PCA-MLR analysis is useful to identify the source of PAHs in the urban region with complicated pollution source.

Spatial modeling and source identification of PAHs in soils and roadside dusts from Hangzhou, a new first-tier megcity of China

Soil (n = 100) and roadside dust (n = 97) samples across a new first-tier megacity (Hangzhou, East China) were collected to systematically survey the spatial patterns and sources of 16 priority Polycyclic aromatic hydrocarbons (PAHs). The total PAH (Σ16PAH) concentrations in the surface soils exhibited an average of 329 ± 168 ng/g with a range of 67.7-2950 ng/g. 45 % of soils suffered from the weak - heavy PAH contaminations. By contrast, the average concentration of Σ16PAHs in roadside dusts was approximately three times higher than that found in the soils. Within both soil and dust samples, PAHs with a high molecular weight (HMW, 4-6 rings) were the dominant homologs. Spatial lag models revealed that industrial and traffic-related variables significantly influenced the spatial distribution of PAHs in dusts. Furthermore, a positive matrix factorization model indicated that Σ16PAHs in soils and dusts mainly derived from coal-related production/combustion and automobile exhaust emission (65.0 % and 77.9 %, respectively). The isotopic composition analysis conducted on heavily polluted samples further demonstrated that HMW PAHs in these soils and dusts predominantly originated from coal processing and liquid fossil fuel combustion. Overall, the findings of this study suggest that the intensive urban construction and human activities strongly stimulated PAH accumulations in soils and dusts during the rapid urbanization of Hangzhou.

Integrative assessment of urban dust polycyclic aromatic hydrocarbons using ground and satellite data in Iran

Recently, for quick urbanization and industrialization, pollutants, especially urban dust, have posed many threats to the human environment. Polycyclic aromatic hydrocarbons (PAHs) are regarded as the main dangerous pollutants that are widespread, persistent, and carcinogenic. The present work aimed to investigate the contamination and sources of PAHs, as well as to assess the risk of cancer for 16 priority PAHs, in urban dust samples in Ahvaz, Isfahan, and Shiraz cities in Iran. We measured PAH concentrations by gas chromatography-mass spectrometry (GC-MS). The average concentrations of the 16 PAHs in Ahvaz, Isfahan, and Shiraz were 6215.11, 7611.03, and 7810.37 μg kg-1, respectively. The domination of low-molecular-weight (LMW) PAHs was observed in Ahvaz, while maximum contribution was observed for high-molecular-weight (HMW) PAHs in Esfahan and Shiraz. For PAHs' source identification, diagnostic ratio, correlation analysis, clustering, and positive matrix factorization (PMF) model were used. PAHs had a combustion (coal and wood, oil, fossil fuels) and gasoline/diesel engine emissions in all cities. Comparative studies suggest that the PAH compounds' level is higher in the research area than in other countries, except for China and India. Also, the pollution of urban dust PAHs has increased over time compared to previous studies in the same cities. The cancer risk from exposure to dust contaminated with PAHs was assessed using the Incremental Lifetime Cancer Risk (ILCR) model. According to the findings, a high risk of exposure to cancer was observed in Ahvaz, Isfahan, and Shiraz. However, compared to adults, children are at higher risk of cancer in their daily lives via dermal contact and unconscious ingestion. Based on the ILCR values, the risk of cancer is in the order of Shiraz > Isfahan > Ahvaz. To assess air pollutants and their effects on urban dust, TROPOMI onboard the Sentinel-5P data were used in the studied cities during 2018-2021. The results show that Ahvaz has different high levels of CO compared to the other 2 cities. Also, Isfahan has different high levels of NO2 compared to the other 2 cities, but Shiraz has different low levels of O3. According to satellite time series data, the trend of the Aerosol Absorbing Index (AAI) has been increasing, while there was a decreasing trend in AAI from the beginning of the COVID-19 pandemic until 12 months later. Therefore, the natural and anthropogenic sources of urban dust PAHs have been increasing in all studied cities. Our findings show that PAH compounds in urban dust pose a significant threat to human health. Therefore, strategic management and planning are vital in reducing urban dust pollution.

Associations between prenatal exposure to polycyclic aromatic hydrocarbons and thyroid hormones in umbilical cord blood

We explored the association between maternal urinary polycyclic aromatic hydrocarbon (PAH) metabolites and thyroid hormones in umbilical cord blood in 120 pairs of pregnant women and newborns. Maternal urinary PAH metabolites were measured using high-performance liquid chromatography with tandem mass spectrometry. Thyroid hormones were measured using a flow fluorescence assay. The dose-response relationship between PAH metabolites and thyroid hormones was analyzed using the generalized linear model and restricted cubic spline model. Results showed that ƩOH PAHs in maternal urine had a negative effect on triiodothyronine (T3). Associations between maternal urinary PAH metabolites and thyroid hormones in umbilical cord blood plasma were observed. Prenatal exposure to PAHs could affect neonatal thyroid hormones, thereby disrupting neonatal thyroid function.

Mechanistic insights into phenanthrene-triggered oxidative stress-associated neurotoxicity, genotoxicity, and behavioral disturbances toward the brandling worm (Eisenia fetida) brain: The need for an ecotoxicological evaluation

In this study, earthworm (Eisenia fetida) brain was chosen as targeted receptors to probe the mechanisms of oxidative stress-related neurotoxicity, genotoxicity, and behavioral disturbances triggered by PHE. Results showed that PHE stress can initiate significant amounts of ROS, thus triggering oxidative stress in E. fetida brain. These effects were accompanied by a significant increase of damage to macromolecules DNA and lipids, resulting in severe oxidative effects. PHE exposure can induce AChE inhibition by ROS-induced injury and the accumulation of excess ACh at the nicotinic post-synaptic membrane, thus inducing aggravated neurological dysfunction and neurotoxicity of E. fetida through an oxidative stress pathway. Moreover, the burrowing behavior of earthworms was disturbed by oxidative stress-induced neurotoxicity after exposure to PHE. Furthermore, the abnormal mRNA expression profiles of oxidative stress- and neurotoxicity-related genes in worm brain were induced by PHE stress. The IBR results suggested that E. fetida brain was suffered more serious damage caused by PHE under higher doses and long-term exposure. Taken together, PHE exposure can trigger oxidative stress-mediated neurotoxicity and genotoxicity in worm brain and behavioral disorder through ROS-induced damage. This study is of great significance to evaluate the harmful effects of PHE and its mechanisms on soil ecological health.

Ecotoxicological evaluation of oxidative stress-mediated neurotoxic effects, genetic toxicity, behavioral disorders, and the corresponding mechanisms induced by fluorene-contaminated soil targeted to earthworm (Eisenia fetida) brain

Fluorene is a commonly identified PAH pollutant in soil and exhibits various worrisome hazardous effects to soil organisms. Currently, the toxicity profiles of fluorene on earthworm brain are rare, and the mechanisms and their corresponding pathways involved in fluorene-triggered neurotoxicity, genotoxicity, and behavior changes have not been reported hitherto. Herein, earthworm (Eisenia fetida) brain was chosen as targeted receptor to explore the neurotoxic effects, genetic toxicity, behavioral disorders, and related mechanisms caused by fluorene-induced oxidative stress pathways. The results showed excess fluorene initiated the release of excessive quantities of ROS in earthworm brain, which have caused oxidative stress and accompanied by serious oxidative effects, including LPO (lipid peroxidation) and DNA injury. To minimize the damage effects, the antioxidant defense mechanisms (antioxidant enzymes and non-enzymatic antioxidants) were activated, and entailed a decrease of the antioxidant capacity in E. fetida brain, which, in turn, causes further ROS-induced ROS release. Exposure of fluorene induced the abnormal mRNA expression of genes relevant to oxidative stress (e.g., GST, SOD, CAT, GPx, MT, and Hsp70) and neurotoxicity (e.g., H02, C04, D06, and E08) in E. fetida brain. Specifically, fluorene can bind directly to AChE, destroying the conformation of this protein, and even affecting its physiological functions. This occurrence caused the inhibition of AChE activity and excess ACh accumulation at the nicotinic post-synaptic membrane, finally triggering neurotoxicity by activation of pathways related to oxidative stress. Moreover, the avoidance responses and burrowing behavior were obviously disturbed by oxidative stress-induced neurotoxicity after exposure to fluorene. The results form IBR suggested more severe poisoning effects to E. fetida brain initiated by high-dose and long-term exposure of fluorene. Among, oxidative stress injury and genotoxic potential are more sensitive endpoint than others. Collectively, fluorene stress can provoke potential neurotoxicity, genotoxicity, and behavioral disturbances targeted to E. fetida brain through the ROS-mediated pathways involving oxidative stress. These findings are of great significance to estimate the detrimental effects of fluorene and the corresponding mechanisms on soil eco-safety.

Polycyclic aromatic hydrocarbons in the surface water and sediment along Euphrates River system: Occurrence, sources, ecological and health risk assessment

This study presented for the first time a comprehensive measurement campaign of 16 PAHs along the Euphrates River for five months, in both water and sediment samples. Our study revealed that the PAHs contamination increased along the flow direction due to the increasing non-point pollution and the return flows of agriculture. The 5-6 rings PAHs were dominant in water and sediment samples with an average of 42 % and 50 %, respectively. The diagnostic ratios of PAHs suggest that the pollution of these compounds originated mainly from petroleum product combustions. The carcinogenic PAHs formed 46 % and 55 % of the total measured compounds in water and sediment samples, respectively, which highlights potential ecological and human health risks. Based on sediment quality guidelines (SQGs), most sites exhibit an effect range between low and medium. The calculated incremental lifetime cancer risk (ILCR) for adult and children were in the 10^-2-10^-3 range, which is 3-6-fold higher than what was reported in the literature. These observations call for urgent attention from environmental authorities of countries sharing this key water source in Western Asia.

Integrated Insights into Source Apportionment and Source-Specific Health Risks of Potential Pollutants in Urban Park Soils on the Karst Plateau, SW China

Polycyclic aromatic hydrocarbons (PAHs) and heavy metal(loid)s (HMs) pose risks to environmental and human health. Identification of priority control contaminants is important in guiding the management and control of these synchronous pollutants. A total of 247 soil samples were collected from 64 urban parks in the karst plateau city of Guiyang in SW China to determine the concentrations, spatial distributions, and health risks of PAHs and HMs. The results indicate that dibenz(ah)anthracene and benzo(a)pyrene are the main PAHs species of high ecological risk, and Cr, Mn, and Ni pose elevated ecological risk among the HMs. Four sources were identified for PAHs (biomass burning, coke oven, traffic sources, and coal burning) and HMs (traffic sources, coal burning, industrial sources, and natural sources). The non-carcinogenic risk (NCR) and total carcinogenic risk (TCR) of PAHs were all determined to be negligible and at acceptable levels, several orders of magnitude below those of HMs. The NCR and TCR values of HMs were relatively high, especially for children (11.9% of NCR > 1; 79.1% of TCR > 10-4). Coal burning and natural sources make the greatest contributions to the NCR and TCR values from karst park soils in Guiyang. Considering HMs bioavailability, NCR and TCR values were rather low, due to the high residual HM fractions. Integrated insights into source specific ecological and human health risk indicate future directions for management and control of synchronous PAH and HM pollution, particularly for karst plateau areas.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12403-023-00534-3.

Magnetic susceptibility as a proxy for detection of total petroleum hydrocarbons in contaminated wetlands

Soil petroleum hydrocarbon contamination in the wetlands could cause ecological risk, especially through leakage into water reservoirs. So, the detection of the spatial variability of total petroleum hydrocarbons (TPH) in these soils is very crucial. The variability of TPH and its associations with magnetic susceptibility (χ_lf) in contaminated soils around the Shadegan pond in southern Iran was investigated. TPH varied from 2.1 to 18.1% (w/w), by the variation of χ_lf from 14.08 to 713.93 × 10^-8 m³ kg^-1. The highest variability (coefficient of variation, CV = 107.12%) was obtained for χ_lf indicating significant impacts of magnetic minerals induced by crude oil contamination. High positive correlations were detected among TPH, χ_lf, and different forms of iron (Fe_d: extracted by CBD, Fe_o: extracted by oxalate, and Fe_t: total iron). The results of mineralogy by powdery XRD and scanning electron microscopy (SEM), also revealed the formation of ferrimagnetic minerals (magnetite, maghemite) during the biodegradation of petroleum hydrocarbons. The stepwise multiple regression analysis showed that χ_lf and Fe_d made a great contribution and could explain about 74% of TPH variability in the studied sites. For the extension of this cost-effective and rapid technique, further work is needed to assay saturation isothermal remnant magnetization and isothermal remanet magnetization in contaminated sites.

Polycyclic aromatic hydrocarbons (PAHs) in soils around oil refineries; Case study: Erbil and Kirkuk refineries, Iraq- A modelling approach

Purpose

Political tensions in Iraq have made attention to environmental issues not a priority for the authorities. Therefore, the influence of Kirkuk and Erbil refineries on contamination of the surrounding soil by polycyclic aromatic hydrocarbons (PAHs), were studied.

Methods

25 soil samples were collected and analyzed using high-performance liquid chromatography (HPLC), and their fate and health risk were investigated using Exposure Model for Soil-Organic Fate and Transport (EMSOFT) and the Monte Carlo Simulation (MCS) model.

Results

High ∑PAHs contamination (raged from 212.8 to 12,790.4 ppb), the dominance of pyrogenic sources, and high ecological risk were observed. The mean hazard index values for children (0.043) are higher than those for adults (0.02), while the incremental lifetime carcinogenic risk values for adults (8.50E-4) are greater than those for children (5.27E-4). Pyrene is the significant soil PAH from the depth of 3 cm downwards, while phenanthrene and fluorene are the major constituents of PAHs between the depth of 3 and 10 cm. Also, low molecular weight PAHs significantly decrease in soil layers over the time frame, and maximum PAHs concentrations belong to high molecular weight PAHs over 20 years.

Conclusion

Using an appropriate monitoring system, as well as sound management decisions to reduce the emission of environmental pollution are needed. Also, it seems that the use of constant values for soil physicochemical parameters such as moisture and porosity, despite seasonal variations, may result in uncertainty for fate and transport modelling. Therefore, seasonal sampling and analysis of soil parameters, would be helpful.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40201-022-00809-y.

Polycyclic Aromatic Hydrocarbons in the Snow Cover in the City of Tyumen (Western Siberia, Russia)

Some of Russia's large industrial cities are sources of hazardous contamination in the environment. Tyumen is one of the most rapidly developing cities in Siberia due to oil and gas extraction in the northern Tyumen Region. Concentrations of 14 polycyclic aromatic hydrocarbons (PAH)s deposited with the particulate matter (PM) of snow in the city of Tyumen were determined by liquid chromatography. In the background area, the rate of atmospheric particulate deposition was shown to be low, and the mean total content of 14 PAHs had a value of 6.2 ng L^-1, which is lower than many unpolluted areas on Earth. In the city of Tyumen, the mean content of PM was five times higher and the mean total content of 14 PAHs was twenty times higher as compared to the background. The contents of chrysene, benzo(k)fluoranthene, and benzo(a)pyrene were increased by multiples of 78, 77, and 32, respectively. The rates of ∑14 PAH deposition with airborne PM over the winter ranged from 1.1 to 65.5 μg m^-2. Calculations of BaP toxic equivalent showed maximal toxicity within the transport zone. Both analysis of spatial distribution and diagnostic ratios showed that the PAHs were mainly from coal combustion and vehicle emissions.

Temporal and spatial pattern of dust storms, their polycyclic aromatic hydrocarbons, and human health risk assessment in the dustiest region of the world

This study evaluated the concentration and health risks of polycyclic aromatic hydrocarbons (PAHs) in Abadan City under 4 different climatic conditions: normal days, dusty days, dust with northwesterly winds, and dust with southeasterly winds. It also determined the sources of aromatics and discussed the relationship between meteorological parameters and PAH concentrations. The spatiotemporal distribution of dust in the area was determined using the HYSPLIT (hybrid single-particle Lagrangian integrated trajectory) back trajectory model, moderate resolution imaging spectroradiometer (MODIS) images. For this purpose, sampling was performed for 70 days using an Omni device. The concentrations of 16 PAHs (USEPA) ranged from 46.22 to 90.96 ng/m³. The highest concentration of high molecular weight (HMW) PAHs was 4-6 rings, of which 4 rings were predominant in all samples. PAH sources were identified using diagnostic ratios and principal component analysis (PCA), and it was shown that PAHs mainly originate from a mixture of sources, including vehicular emissions, petrol emissions, and traffic. Wind speed was negatively correlated with dust, except on dusty days. This result indicates a decrease in PAH concentrations when wind speed increases. On the other hand, the dust correlation with PAH was positive on normal days, but a negative correlation was observed on dusty days. This result was due to the lower concentration of PAHs from natural resources (such as dust source areas) vs. human resources (such as traffic and industry). PAH health risk assessment in Abadan City showed that the risk of carcinogenesis was higher on normal days and through skin contact. The probability of incremental lifetime cancer risk (ILCR) in all sampling conditions was potential in terms of carcinogenic risk (10^-4-10^-6). As a critical risk factor, relevant authorities should prevent, control, and reduce it.

Polycyclic aromatic hydrocarbons in soils of Central Plains Urban Agglomeration, China: The bidirectional effects of urbanization and anthropogenic activities

To investigate the variations in environmental behavior (levels, distribution, sources, and soil toxicity) of polycyclic aromatic hydrocarbons (PAHs) under the impact of anthropogenic activities during the urbanization process, we collected soil samples from 195 sites in the Central Plains Urban Agglomeration (CPUA), North China, and analyzed 16 U.S. Environmental Protection Agency (EPA) PAH priority pollutants. We divided the sampling sites into three groups (urban area, industrial area, and farmland) and collected soil samples (0-20 cm surface layer). ∑₁₆PAHs concentrations in the soils of the urban area, industrial area, and farmland ranged from 24.2 to 4400 ng/g, 12.3-8780 ng/g, and 20.9-852 ng/g (the average value of 349, 634, and 186 ng/g), respectively. The 4 to 5 ring PAHs were dominant compounds in three soil types, accounting for 65-80% of the ∑₁₆PAHs. The results of the source analysis showed that the PAHs in the soils of CPUA were mainly from energy consumption. PAH levels in urban and industrial soils had a potential low cancer risk. The impact of urbanization on PAHs in the soil was bidirectional. On the one hand, the level of PAHs in the farmland soil might increase due to burning coal and agricultural machinery, which releases diesel or petrol fumes. On the other hand, in the urbanization process, the PAH content in urban soil and industrial soil showed a downward trend due to the implementation of environmental protection policies in China, which have reduced the atmospheric input of PAHs into the soil.

Health risks of heavy metal contamination in road surface dusts from selected major roads in East London, South Africa

The study assessed the concentration and health hazards of Cd, Mn, Pb, Ni and Zn in 54 road surface dust samples. Heavy metal concentrations descended as follows: Mn > Zn > Pb > Ni > Cd and the concentrations were 316.22, 161.24, 88.76, 22.69 and 0.21. Health hazard assessment showed that the modes of exposure descended in the sequence of ingestion > dermal contact > inhalation for children and dermal contact > ingestion > inhalation for adults. The hazard index for both populations was >1 suggesting susceptibility to non-cancer risks. The carcinogenic risk for Ni and Cd was below 1 × 10^-4 suggesting a negligible risk of cancer for both populations. The study suggests that more research studies on HM contamination in road dusts are to be undertaken in the country to develop HM pollution threshold values in road dusts and to account for pollution in city centers.

Estimating accumulation rates and health risks of PAHs in residential soils of metropolitan cities

Predicting temporal changes in PAH concentrations in urban soils and their corresponding health risk is essential for developing appropriate management measures to prevent those risks. Concentrations of PAHs in soils of residential areas with different building ages in three metropolitan cities were determined to estimate the accumulation rates of PAHs in soil. The mean concentrations of total PAHs (∑PAHs) were 1297 ng/g in Shanghai, 865 ng/g in Beijing, and 228 ng/g in Shenzhen. The primary sources of the PAHs were traffic and coal combustion for industrial activity and space heating. The high PAH concentrations in Shanghai were attributed to the relatively high average building age of the sampled residential areas and the low annual temperature in the city. The overall annual accumulation rates of PAHs in the soils were estimated from linear regressions between the PAH concentrations and building age of the residential areas. The annual accumulation rate of PAHs in the soils was 64.7 ng/g in Beijing, 24.2 ng/g in Shanghai, and 3.3 ng/g in Shenzhen. The higher rate in Beijing was due to the higher intensity of PAH emissions and the lower temperature. The regression estimations suggest that health risks posed by PAHs in residential soils of the metropolitan cities increase considerably with time.

Contamination, spatial distribution, and source contribution of persistent organic pollutants in the soil of Guiyang city, China: a case study

The contamination of persistent organic pollutants (POPs), including dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexane (HCH), and polycyclic aromatic hydrocarbon (PAH), is the most studied environmental issue. In 2020, a total of sixty soil samples collected from ten locations in Guiyang were analyzed to assess the presence of four DDTs and HCHs and sixteen PAHs. The concentrations of total DDTs, total HCHs and Σ₁₆PAHs in the soil were between 0.26 and 12.76, 0.23 and 51.80 μg/kg, and 10.02 and 1708.86 μg/kg, respectively. The mean and median concentrations of total DDTs, total HCHs and Σ₁₆PAHs in the soil were 1.04 and 0.26 μg/kg, 4.32 and 0.23 μg/kg, 139.14 and 98.98 μg/kg, respectively. p,p'-DDT, p,p'-DDD and γ-HCH the dominant organochloride pollutants in the soil, while 4-ring PAHs were the dominant PAHs, occupying 41.1-53.6% of the total PAHs in the soil. The highest levels of PAHs in the soil were observed in areas of Guiyang with relatively larger population densities and more developed heave industries. Various diagnostic tools were used to identify the potential sources of the POPs in the soil. The data indicated that DDTs and HCHs were from past and recent common inputs and that mixtures of several combustion activities (biomass, coal and petroleum combustion, diesel, gasoline, and vehicular emissions) were the major sources of PAHs in the Guiyang soil. The results provide information for the assessment of the extent of POP pollution in the Guiyang soil and can help authorities establish environmental protection regulations and soil remediation techniques.

Sixteen priority polycyclic aromatic hydrocarbons in roadside soils at traffic light intersections (Bratislava, Slovakia): concentrations, sources and influencing factors

Combustion of fossil fuels is the most important source of polycyclic aromatic hydrocarbons (PAHs) in the environment. Cities are typical of many human activities which are dependent on fossil fuels (road and railway transport, heat generation, waste incineration and industry) on a small area, leading to high concentrations of PAHs in urban air, dust and soil. The aim of this study was to determine the possible influence of urban traffic on the accumulation of sixteen priority PAHs in soils (n = 132 at two soil depths of 0-10 cm and 10-20 cm) taken at intersections (n = 37) with different traffic volumes and road ages. Variable concentrations of the sum of PAHs (∑₁₆PAH) ranging from 188 to 21,950 μg/kg with a mean and median of 3021 μg/kg and 1930 μg/kg were recorded, respectively. Concentrations of PAHs positively correlated with soil organic carbon content (TOC) (r_Spearman = 0.518; p < 0.001). Statistically significant positive correlations between ∑₁₆PAH concentrations and traffic volume/road age were found in this study (r_Spearman = 0.689/0.619; p < 0.001), while ∑₁₆PAH concentration decreased with increasing distance from the road edge and was statistically lower at a soil depth of 10-20 cm than at 0-10 cm (p < 0.05). Multivariate statistical methods (principal component analysis and cluster analysis) applied to log-ratio transformed data (clr) to decrease the constant sum constraint coupled with positive matrix factorisation (PMF) modelling pointed to the dominance of pyrogenic emission sources, with 62.1% traffic-related (petrol and diesel emissions, liquid fuel and motor oil spills, and tyre wear) according to PMF results.

Behavioral, histopathological, genetic, and organism-wide responses to phenanthrene-induced oxidative stress in Eisenia fetida earthworms in natural soil microcosms

Phenanthrene (PHE) contamination not only changes the quality of soil environment but also threatens to the soil organisms. There is lack of focus on the eco-toxicity potential of this contaminant in real soil in the current investigation. Here, we assessed the toxic effects of PHE on earthworms (Eisenia fetida) in natural soil matrix. PHE exhibited a relatively high toxicity to E. fetida in natural soil, with the LC₅₀ determined to be 56.68 mg kg^-1 after a 14-day exposure. Excessive ROS induced by PHE, leading to oxidative damage to biomacromolecules in E. fetida, including lipid peroxidation, protein carbonylation, and DNA damage. The antioxidant defense system (total antioxidant capacity, glutathione S-transferase, peroxidase, catalase, carboxylesterase, and superoxide dismutase) in E. fetida responded quickly to scavenge excess ROS and free radicals. Exposure to PHE resulted in earthworm avoidance responses (2.5 mg kg^-1) and habitat function loss (10 mg kg^-1). Histological observations indicated that the intestine, body wall, and seminal vesicle in E. fetida were severely damaged after exposure to high-dose PHE. Moreover, earthworm growth (weight change) and reproduction (cocoon production and the number of juvenile) were also inhibited after exposure to this pollutant. Furthermore, the integrated toxicity of PHE toward E. fetida at different doses and exposure times was assessed by the integrated biomarker response (IBR), which confirmed that PHE is more toxic to earthworms in the high-dose and long-term exposure groups. Our results showed that PHE exposure induced oxidative stress, disturbed antioxidant defense system, and caused oxidative damage in E. fetida. These effects can trigger behavior changes and damage histological structure, finally cause growth inhibition, genotoxicity, and reproductive toxicity in earthworms. The strength of this study is the comprehensive toxicity evaluation of PHE to earthworms and highlights the need to investigate the eco-toxicity potential of exogenous environmental pollutants in a real soil environment.

Pollution status and human health risk assessment of potentially toxic elements and polycyclic aromatic hydrocarbons in urban street dust of Tyumen city, Russia

This study investigated levels and sources of pollution and potential health risks associated with potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in urban street dust collected from Tyumen city, a large transport centre with one of the highest motorization rates in Russia. Twenty street dust samples were collected from four grades of roads in five different land use areas. Research methods included measurements of physical and chemical properties of street dust, concentrations of 18 PTEs using inductively coupled plasma mass spectrometry, 12 PAHs using high-performance liquid chromatography, and statistical analysis of the data. Concentrations of Ni, Cr, Sb, and Mo, as well as medium and high molecular weight PAHs in urban street dust, were notably higher than in soils within the city, which indicates that transport is the main source of these elements. Concentrations of Cu, Cd, Pb, Zn, Mn, and As in street dust of Tyumen were lower compared to many large cities, while Cr, Ni, and Co were higher. Concentrations of PAH were comparable to other large nonindustrial cities. Total contamination of street dust by both PTEs and PAHs showed more robust relationships with the number of roadway lanes rather than land use. The estimated carcinogenic risks were low in 70% of samples and medium in 30% of samples. Noncarcinogenic risks were attributed to exposure to Co, Ni, V, and As. The total noncarcinogenic risk for adults was found to be negligible, while the risk was found to be moderate for children.

Relationship between Urban Green Spaces and Cancer: A Scoping Review

This scoping study aims to explore the relationships between urban green spaces (UGSs) and the onset, remission and recovery of cancer. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for scoping reviews (protocol published in 2018). Eligibility criteria for papers were: (1) to be concerned with UGSs, (2) reporting effects of UGSs on cancer-related outcomes including direct or indirect measures, (3) reporting randomized controlled trials, prospective cohort studies, case studies, observational studies, non-comparative studies, (4) in English or French. The search covered primary studies in the published and unpublished (grey) literatures searching by hand and electronic databases (MEDLINE, Green File, Cumulative Index to Nursing and Allied Health Literature and ScienceDirect). Among 1703 records screened by two reviewers independently, 29 were included for qualitative synthesis. We classify the cancers concerned and the effects reported i.e., protective effect, risk or without association. The most investigated cancers are bladder, breast and lung cancer. Our study also identified contributing factors and their mediating effects between UGSs and cancer. Even though the strength of the evidence of the associations between UGSs and cancer is still weak due to the low number of studies and their design, results highlight the wide variety of possible mediating factors between the use of green spaces and cancer occurrence, remission and/or prevention. Knowledge gaps and future research perspectives should be oriented to qualitative research on protective factors with an attention to equity in UGS access and use.

Elucidating the distribution and sources of street dust bound PAHs in Durgapur, India: A probabilistic health risk assessment study by Monte-Carlo simulation

Spatial and seasonal distribution of PAHs, source identification, and their associated carcinogenic health risk was investigated in street dust of Durgapur, India. Street dust is an important indicator to detect the quality of the environment as well as the sources of pollutants. The obtained results showed fluctuation in PAHs concentrations from 2317 ± 402 ng/g to 5491 ± 2379 ng/g along with the sampling sites. Seasonal variation revealed higher PAHs concentrations in the winter season (5401 ± 993 ng/g) with the maximum presence of 4-ring PAHs. Two-way analysis of variance (ANOVA) exposed that the sites, seasons and site-season interactions were vividly affected by dissimilar PAHs. The PAHs source identification was investigated by principal component analysis (PCA), positive matrix factorization (PMF), diagnostic ratios, and they revealed pyrogenic, diesel, gasoline, wood and coal combustion to be the key sources of the PAHs in street dust. Obtained results from incremental lifetime cancer risk (ILCR) model exhibited the carcinogenic risk for children ranged from 2.4E-06 to 3.8E-06 while 2.1E-06 to 3.4E-06 for adults which were above the baseline value 1.0E-06. The Monte Carlo simulation model identified cumulative cancer risk of sixteen PAHs in 50th percentile were 2.8 and 1.7 times more while in 95th percentile, the values were 8.8 and 7.8 times higher than the acceptable value of 1E-06 for child and adult respectively.

Distribution, sources, risks, and vitro DNA oxidative damage of PM2.5-bound atmospheric polycyclic aromatic hydrocarbons in Urumqi, NW China

Research has focused on the impacts of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere due to their potential carcinogenicity. In this study, we investigated the seasonal variation, sources, incremental lifetime cancer risks (ILCR_S), and vitro DNA oxidative damage of PAHs in Urumqi in NW China. A total of 72 atmospheric samples from Urumqi were collected over a year (September 2017-September 2018) and were analyzed for 16 PAHs that are specifically prioritized by the U.S Environmental Protection Agency (U·S EPA). The highest PAHs concentrations were in winter (1032.66 ng m^-3) and lowest in spring (146.00 ng m^-3). Middle molecular weight PAHs with four rings were the most abundant species (45.28-61.19% of the total). The results of the diagnostic ratio and positive matrix factorization inferred that the major sources of atmospheric PAHs in Urumqi were biomass burning, coking, and petrogenic sources (52.9%), traffic (30.1%), coal combustion (8.9%), and the plastics recycling industry (8.1%). ILCR_S assessment and Monte Carlo simulations suggested that for all age groups PAHs cancer risks were mainly associated with ingestion and dermal contact and inhalation was negligible. The plasmid scission assay results showed a positive dose-response relationship between PAHs concentrations and DNA damage rates, demonstrating that toxic PAHs was the primary cause for PM_2.5-induced DNA damage in the air of Urumqi.

Occurrence, sources and ecological and human health risks of polycyclic aromatic hydrocarbons in soils from some functional areas of the Nigerian megacity, Lagos

The study investigated the levels of the USEPA 16 PAHs in soils collected from selected functional areas (cemetery, commercial, industrial and residential areas) of the Nigerian megacity, Lagos. The soil samples were subjected to ultrasonic-assisted extraction in a 1:1 (v/v) mixture of dichloromethane/hexane, and the PAHs in the resulting extracts were determined by gas chromatography-mass spectrometry. The Σ16 PAHs in soils of these functional areas varied between 890-4675, 485-4513, 111-15,577 and 509-2047 μg kg^-1 for cemetery, industrial, commercial and residential areas, respectively. The benzo(a)pyrene carcinogenic (BaP_TEQ) and mutagenic equivalency (BaP_MEQ) values of PAHs in these soils spanned from 523 to 1046 and 446 to 1129 µg kg^-1, respectively. The hazard index values suggested that there are adverse (non-carcinogenic) health effects for a child's exposure to PAHs in soils of commercial areas. The cancer risk values resulting from an adult's and a child's exposure to PAHs in these urban soils via dermal contact and oral ingestion surpassed the target value of 10^-6 which suggested that there is a considerable cancer risk relating to human exposure to PAHs in these urban soils. An ecological risk assessment making use of soil quality guidelines and risk quotients suggested a low ecological risk to organisms in soils of these functional areas except for those from commercial areas. PAH isomeric ratios and principal component analysis indicated that PAHs in these soils arise from petrogenic inputs, such as occasional spills of liquid petroleum fuels and discharges from automobile workshops and generator houses, as well as pyrogenic processes including traffic emissions and combustion of fossil fuels and biomass.

Spatiotemporal toxicity assessment of suspended particulate matter (SPM)-bound polycyclic aromatic hydrocarbons (PAHs) in Lake Chaohu, China: Application of a source-based quantitative method

The spatiotemporal associations between the emissions and environmental toxicities of polycyclic aromatic hydrocarbons (PAHs) in lake still remain an issue. Here, we focused on the suspended particulate matter (SPM)-bound PAHs in Lake Chaohu, China to quantitatively estimate their spatiotemporal toxicities from different sources. A source-based quantitative method, positive matrix factorization (PMF)-benzo[a]pyrene-based toxic equivalency (TEQ_BaP) model, was applied. Firstly, we investigated the spatiotemporal characteristics of SPM-bound PAHs. The concentrations of Σ₂₁ PAHs ranged from 1646 to 19267 ng·g^-1. Low-ring PAHs were found to have the highest fractions. T-distributed stochastic neighbor embedding (t-SNE)-partitioning around medoid (PAM) technic revealed significantly spatiotemporal variation characteristics of SPM-bound PAHs in Lake Chaohu. Season, location (west or east lake zone), and sample classification (estuary or lake) together governed the patterns. Then, their potential sources were apportioned. Our results found that diagnostic ratios did not work perfectly. However, 3 factors were separated by PMF model. Unburned petroleum (F1), biomass, coal and gasoline combustion (F2), and diesel, straw combustion (F3) were the main sources of PAHs, accounting for 36.16%, 48.96% and 14.88%, respectively. The patterns of the source profiles were season-dependent. Finally, the toxicity of SPM-bound PAHs from different sources were predicted by PMF-TEQ_BaP model, and the model predictions were satisfactorily acceptable. Overall, predicted Σ₁₉ TEQ_BaP of SPM-bound PAHs in Lake Chaohu ranged from 20.8 to 947.9 ng·g^-1. Benzo[e]pyrene (BeP), benzo[a]pyrene (BaP) and benzo[b]fluoranthene (BbF) were the main toxic species. Temporally, PAH toxicity posed significantly seasonal differences. F3 had primary contributions to Σ₁₉ TEQ_BaP. Cutting the diesel consumption and using cleaner energy substitutes were suggested to reduce the PAH toxicity in Lake Chaohu. Overall, we expected this study could give new insights into the spatiotemporal associations between the sources and toxicities of SPM-bound PAHs in lake ecosystem.

Post relocation of industrial sites for decades: Ascertain sources and human risk assessment of soil polycyclic aromatic hydrocarbons

As a persistent organic pollutant, polycyclic aromatic hydrocarbons (PAHs) may still residually pollute industrial sites after relocation. This study investigated the contamination status of PAHs in the topsoils of three industrial legacy sites (the Shougang industrial ruins, the original Beijing coking plant area, and an abandoned gas station) that relocated more than 10 years ago from downtown Beijing. The sources of PAHs in the soil were qualitatively and quantitatively analyzed, and health risks were evaluated for different groups of people. The total concentration of 16 PAHs in the study area ranged from 371.1 ng g^-1 to 4073.9 ng g^-1. The pollution levels of the three study areas were abandoned gas station > Beijing coking plant > Shougang ruins. In terms of composition, low-ring aromatics accounted for the majority of the detected PAHs, and in the dry season, low-ring aromatics accounted for a higher proportion in the three areas than in the wet season. The comparison of the PAH diagnostic ratio and PMF model verification showed that the sources of PAHs in the Shougang ruins and the Beijing coking plant area were mainly those of biomass and coal combustion, accounting for 66.3% and 56.1% of the total detected PAHs, respectively; the PAH sources of the abandoned gas station storage tank area were largely that of petrol (33.9%) and diesel combustion (23.8%). Since these industrial sites were located in urban centers, this study also conducted a health risk assessment of the topsoil. The total carcinogenic risk range of the three contaminated sites was 1.41E-06 to 2.47E-05. Abandoned industrial sites have potential carcinogenic risks to human health. The government needs to conduct comprehensive risk assessments and remedial measures on soils of industrial legacy sites to achieve land reuse.

Characteristics, Sources, and Risks of Polycyclic Aromatic Hydrocarbons in Topsoil and Surface Water from the Liuxi River Basin, South China

The concentrations, composition, sources, and risks of polycyclic aromatic hydrocarbons (PAHs) in topsoil and surface water of the Liuxi River basin, south China were analyzed in this study. The total concentrations of 16 PAHs ranged from 296.26 to 888.14 ng/g in topsoil and from 156.73 to 422.03 ng/L in surface water, indicating mild pollution. The PAHs in topsoil exhibited an even spatial distribution, suggesting that they originated primarily from dry and wet deposition of transported pollutants. The concentration of PAHs in surface water did not differ significantly geographically, but the concentrations of total, three-, and four-ring PAHs were significantly lower in the Liuxi River than in its tributaries. Three- and two-ring PAHs predominated in topsoil and surface water, respectively. A correlation analysis suggested that the total organic carbon content and pH exerted a negligible effect on the spatial distribution of PAHs in topsoil, and they may have common sources. Fossil fuel combustion (particularly vehicle emissions) and coking production were the dominant sources of PAHs in topsoil, whereas those in surface water were derived from a variety of sources. The total toxic equivalent concentrations of 16 PAHs in topsoil ranged from 3.73 to 105.66 ng/g (mean, 30.93 ng/g), suggesting that exposure to the basin's topsoil does not pose a risk to the environment or public health according to the Canadian soil quality guidelines. A risk assessment revealed that the total PAH concentrations in surface water posed a low ecological risk.

Polycyclic aromatic compounds in urban soils of Stockholm City: Occurrence, sources and human health risk assessment

Polycyclic aromatic compounds (PACs) are ubiquitous pollutants that are found everywhere in our environment, including air, soil and water. The aim of this study was to determine concentrations, distribution, sources and potential health risk of 43 PACs in soils collected from 25 urban parks in Stockholm City, Sweden. These PACs included 21 PAHs, 11 oxygenated PAHs, 7 methylated PAHs, and 4 azaarenes whose concentrations ranged between 190 and 54 500, 30.5-5 300, 14.9-680, and 4.17-590 ng/g soil, respectively. Fluoranthene was found at the highest levels ranging between 17.7 and 9800 ng/g, benzo[a]pyrene between 9.64 and 4600 ng/g, and the highly potent carcinogen dibenzo[a,l]pyrene up to 740 ng/g. The most abundant oxy-PAH was 6H-benzo[cd]pyren-6-one (2.09-2300 ng/g). Primary sources of PAHs were identified by use of diagnostic ratios and Positive Matrix Factorization modelling and found to be pyrogenic including vehicle emissions and combustion of biomass. Estimating the incremental lifetime cancer risks (ILCRS) associated with exposure to PAHs in these soils indicated that the PAH levels in some parks constitute a considerable increased risk level for adults and children (total ILCR > 1 × 10^-4). Compared to worldwide urban parks contamination, we conclude that the PAC soil levels in parks of Stockholm City in general are low, but that some parks are more heavily contaminated and should be considered for clean-up actions to limit human health risks.

Positive matrix factorization on source apportionment for typical pollutants in different environmental media: a review

A bibliometric analysis of published papers with the key words "positive matrix factorization" and "source apportionment" in 'Web of Science', reveals that more than 1000 papers are associated with this research and that approximately 50% of these were produced in Asia. As a receptor-based model, positive matrix factorization (PMF) has been widely used for source apportionment of various environmental pollutants, such as persistent organic pollutants (POPs), heavy metals, volatile organic compounds (VOCs) as well as inorganic cations and anions in the last decade. In this review, based on the papers mainly from 2008 to 2018 that focused on source apportionment of pollutants in different environmental media, we provide a comparison and summary of the source categories of typical environmental pollutants, with a special focus on polycyclic aromatic hydrocarbons (PAHs), apportioned using PMF. Based on the statistical average, coal combustion and vehicular emission, are shown to be the two most common sources of PAHs, and contribute much more to emissions than other sources, such as biomass burning, biogenic sources and waste incineration. Heavy metals were mainly from agricultural activities, industrial and vehicular emissions and mining activities. Quantitative source apportionment on pollutants such as VOCs and particulate matter were also apportioned, showing a prominent contribution from fossil-fuel combustion. We conclude that, aside from natural sources, abatement strategies should be focused on changes in energy structure and industrial activities, especially in China. Source apportionment of typical POPs including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), halogenated flame retardants (HFRs) and perfluorinated compounds (PFCs) is less comprehensive and further study is required.

Distribution, Origins and Hazardous Effects of Polycyclic Aromatic Hydrocarbons in Topsoil Surrounding Oil Fields: A Case Study on the Loess Plateau, China

The Loess Plateau has one of the most vulnerable ecological environments in the world, but it also contains abundant oil and gas resources that are regularly exploited, which has resulted in serious environmental problems. Therefore, it is important to analyze the polycyclic aromatic hydrocarbons (PAHs) present in the topsoil of this region. The ∑16PAHs concentrations between 1980–1999 and 2000–2019 ranged from 1134.20–15871.04 and 1010.67–18,068.80 µg kg⁻¹, with average values of 5021.30 and 5662.82 µg kg⁻¹. All samples displayed heavy pollution levels according to European soil quality standards. In addition, among the measured physicochemical properties, the soil organic carbon (SOC) had the greatest influence on PAHs, while soil particle size distribution had the smallest effect. Source apportionment indicated that the two main sources were petroleum source (37.57%) and vehicular traffic source (25.88%). Lastly, an assessment of the carcinogenic risks illustrated that more focus should be placed on the dermal pathway in which the human body is exposed to soil PAHs. Overall, the carcinogenic risks in different populations did not exceed 10⁻⁴, but there was still a potential carcinogenic risk in some age groups, especially in adult women.

Levels, sources, and toxicity assessment of polycyclic aromatic hydrocarbons in urban topsoils of an intensively developing Western Siberian city

This study investigates the levels, sources, spatial distribution, and toxicity of polycyclic aromatic hydrocarbons (PAHs) in urban soils of Tyumen, Russia. Observations of PAHs in cities of Western Siberia accomplished by a representative set of samples are very rare, even though it is one of the most urbanized parts of Russia. Therefore, it is important to estimate the status of PAHs in soils of urban environments representing vast Siberian regions. Tyumen, as one of the most intensively developing cities of Western Siberia, is a good object for such studies. Topsoil samples (0-10 cm) were collected from 241 sampling sites on a regular grid within Tyumen city limits. It was found that total concentration of 12 priority PAHs ranged from 33.4 to 2147.9 μg kg^-1, with a median value of 280.3 μg kg^-1. High-molecular-weight (HMW) PAHs were dominant, accounting for the majority (62%) of the total PAHs. Among the PAHs in soils, 4-ring compounds were predominant in all studied samples, followed by 5- and 6-ring PAHs. Phenanthrene, pyrene, fluoranthene, and benzo(ghi)perylene had values of 28%, 19%, 15%, and 10% of total PAHs, respectively. Results showed that large high-contrast anomalies of HMW PAHs were related to low-residential and transport areas. The diagnostic ratios, as well as hierarchical cluster analysis (HCA) and principal component analysis (PCA), confirmed that sources associated with the transport were the most significant, while biomass combustion played an important role as a source of PAHs in agricultural, low-residential, and recreational areas. Levels of individual PAHs, as well as total PAHs in urban soils of Tyumen, were comparable with those in non-industrial cities with similar populations but were significantly lower than those in large industrial centers. Assessment of soil toxicity using toxic equivalent quantity (TEQ_BaP) showed that the TEQ_BaP values varied from 2.0 to 388.2 μg kg^-1, with a mean value of 34.9 μg kg^-1 and median of 19.8 μg kg^-1, and were lower than those in heavy industrialized cities, but higher than those in soils of cities specializing in consumer and service industries.

Polycyclic aromatic hydrocarbons in urban soils of China: Distribution, influencing factors, health risk and regression prediction

Polycyclic aromatic hydrocarbons (PAHs) in urban soils are a risk to the health of residents. To predict those risks, the distribution and the factors influencing the concentration of PAHs were studied by collecting 1120 records of soil PAHs published during 2006-2017 from 26 cities. The mean concentrations of 16 PAHs (∑PAHs) in soil varied from 123 μg/kg to 5568 μg/kg, with a mean value of 1083 μg/kg, suggesting that a few cities were polluted. The distribution of ∑PAHs in the cities followed two gradients, namely from northern China through eastern China to southern China and from industrial cities through developed cities to cities that are main tourist attractions. The concentrations were significantly correlated to annual temperature, the efficiency of energy use, and to such measures of air quality as PM₁₀ and NO₂ concentrations. A regression equation developed to predict the concentration of ∑PAHs in soil and the corresponding health risks to residents of 35 major Chinese cities of China showed that the risks to adults and children were slight in most cities but those in a few industrial cities were of concern, and field investigations are recommended to assess the risk in greater detail. The method offers a useful tool for predicting such risks in other cities even when data on soils PAHs are not available.

The application of a handheld mid-infrared spectrometry for rapid measurement of oil contamination in agricultural sites

Rapid analysis of oil-contaminated soils is important to facilitate risk assessment and remediation decision-making process. This study reports on the potential of a handheld mid-infrared (MIR) spectrometer for the prediction of total petroleum hydrocarbons (TPH), including aliphatic (alkanes) and polycyclic aromatic hydrocarbons (PAH) in limited number of fresh soil samples. Partial least squares regression (PLSR) and random forest (RF) modelling techniques were compared for the prediction of alkanes, PAH, and TPH concentrations in soil samples (n = 85) collected from three contaminated sites located in the Niger Delta, Southern Nigeria. Results revealed that prediction of RF models outperformed the PLSR with coefficient of determination (R²) values of 0.80, 0.79 and 0.72, residual prediction deviation (RPD) values of 2.35, 1.96, and 2.72, and root mean square error of prediction (RMSEP) values of 63.80, 83.0 and 65.88 mg kg^-1 for TPH, alkanes, and PAH, respectively. Considering the limited dataset used in the independent validation (18 samples), accurate predictions were achieved with RF for PAH and TPH, while the prediction for alkanes was less accurate. Therefore, results suggest that RF calibration models can be used successfully to predict TPH and PAH using handheld MIR spectrophotometer under field measurement conditions.

Polycyclic aromatic hydrocarbons (PAHs) in agricultural soils from Ningde, China: levels, sources, and human health risk assessment

Soil-bound polycyclic aromatic hydrocarbons (PAHs) in farmland are critical to human health. The level, composition, source, and cancer risk of sixteen PAHs in agricultural soil from Ningde, China, were investigated. The results indicated that the total concentrations of 16 PAHs ranged from 77.3 to 1188 ng g^-1, with a mean value of 406 ng g^-1. Five-ring PAHs were found to have the highest concentrations (148 ± 133 ng g^-1), followed by four-ring (120 ± 101 ng g^-1), three-ring (61.9 ± 54.2 ng g^-1), six-ring (44.6 ± 61.0 ng g^-1), and two-ring (31.3 ± 31.0 ng g^-1). Employing positive matrix factorization (PMF), four PAH sources including biomass burning (36.3%), coal combustion (35.5%), traffic emissions (16.4%), and coke source (11.8%) were identified. Incremental lifetime cancer risk (ILCR) results showed that ILCR values ranged from 7.1 × 10^-4 to 1.1 × 10^-3, which will cause moderate-to-high cancer risk to human health mainly via the soil ingestion and dermal contact exposure pathways. The source-oriented results indicated that coal combustion (32.7%), traffic emission (34.3%), and biomass burning (32.4%) had similar contributions to the total cancer risk. Therefore, more attention should be paid to these pyrolysis-originated sources to protect humanity from the health risk of PAHs.

Biomass burning contributed most to the human cancer risk exposed to the soil-bound PAHs from Chengdu Economic Region, western China

The purpose of this study was to assess the human cancer risk due to the exposure to the soil-bound polycyclic aromatic hydrocarbons (PAHs) from Chengdu Economic Region (CER), western China with the main concern on cancer risk source apportionment. The total concentrations of sixteen PAHs ranged from 12.5 to 75431 ng g^-1, with a mean value of 3106 ng g^-1, which suggested that the most areas of CER were contaminated. Source apportionment of PAHs was conducted by the positive matrix factorization (PMF) model and the biomass burning contributed most (63.6%) to the total PAHs, followed by petroleum combustion (16.0%), coke source (11.3%), and petrogenic source (9.2%). Results from incremental lifetime cancer risk (ILCR) calculation showed that soil ingestion exerted the highest cancer risk (accounted for 98.1 - 99.3% of the total cancer risk) on human health among three different exposure pathways, followed by dermal contact (0.66 - 1.83%) and inhalation (0.03 - 0.04%). Among different age groups, adult suffered the highest cancer risk via any exposure pathways. Based on PMF and ILCR methods, the cancer risk source apportionment was conducted and the biomass burning showed moderate cancer risk. The petrogenic, coke, and petroleum sources showed low cancer risks to human. To analyze the sensitivity of the parameters used in ILCR calculation, Monte Carlo simulation was employed. The results indicated that the contribution of each source and exposure duration (ED) were the influential parameters on human health associated with soil-bound PAHs. Therefore, much attentions should be paid to biomass burning to avoid cumulative cancer risk.

Status, sources, and risk assessment of polycyclic aromatic hydrocarbons in urban soils of Xi'an, China

To identify status, source of polycyclic aromatic hydrocarbons (PAHs) in urban soils and to assess soil environmental quality in Xi'an City, China, total 45 soil samples were collected from surface layer (0-10 cm) in different functional areas. Total concentrations of 16 US EPA priority PAHs ranged from 149.9 to 5770 μg kg^-1, with a mean of 1246 μg kg^-1. High molecular weight (HMW) PAHs accounted for the majority (42.4-72.2%) of the total PAHs in the urban soils, and phenanthrene (Phe), fluorene (Flo), pyrene (Pyr), benzo(b)fluoranthene (BbF), and chrysene (Chr) were the major compounds. Concentrations of PAHs varied among different functional areas. High level of PAHs was particularly apparent in industrial zones and city road overpass, while low level was recorded in scenic spots and campus. The integration of isomer ratios, principal component analysis (PCA), and positive matrix factor (PMF) indicated that the sources of PAHs in Xi'an urban soils were mainly derived from vehicle emissions and coal combustion. Based on incremental lifetime cancer risks (ILCR) model, the urban soils from the three functional areas (industrial zone, urban road, and city road overpass) posed potential cancer risk, and the cancer risks of direct ingestion for children were apparently higher than that for adolescence and for adult, respectively. Therefore, attention should be paid to the health risk for children exposed to PAHs in the urban soils.

Assessment of Polycyclic Aromatic Hydrocarbons in School Playground Soils in Urban Gwangju, South Korea

Soil samples from school playground of Gwangju City were analyzed for 16 polycyclic aromatic hydrocarbons (PAHs), and the soil contamination status and the potential cancer risk for students and adults were investigated. Soil samples were collected from 57 sites from 5 districts of Gwangju City in the summer of 2013. Regardless of the sampling site, the ∑PAHs concentrations ranged from 13.2 to 145.5 ng/g (mean 51.2 ng/g). Four and five-ring PAHs were predominant in the soil samples while the fraction of two-ring PAHs was the lowest. Seven carcinogenic PAHs contributed ~ 55% of ∑PAHs in school playground soils. The benzo[a]pyrene (46.4%) and dibenz[a,h]anthracene (41.2%) were the major contributors to toxic equivalent quantity. The strong correlation between carcinogenic PAHs suggested that they originated from the same source either vehicular emission or coal combustion, because they are markers of these pollution sources. The mean cancer risk for students (3.61 × 10^-7) and adults (8.41 × 10^-6) was in the U.S. EPA safety range (< 10^-6).

Organic contamination and remediation in the agricultural soils of China: A critical review

Soil pollution is a global problem in both developed and developing countries. Countries with rapidly developing economies such as China are faced with significant soil pollution problems due to accelerated industrialization and urbanization over the last decades. This paper provides an overview of published scientific data on soil pollution across China with particular focus on organic contamination in agricultural soils. Based on the related peer-reviewed papers published since 2000 (n=203), we evaluated the priority organic contaminants across China, revealed their spatial and temporal distributions at the national scale, identified their possible sources and fates in soil, assessed their potential environmental risks, and presented the challenges in current remediation technologies regarding the combined organic pollution of agricultural soils. The primary pollutants in Northeast China were polycyclic aromatic hydrocarbons (PAHs) due to intensive fossil fuel combustion. The concentrations of organochlorine pesticides (OCPs) and phthalic acid esters (PAEs) were higher in North and Central China owing to concentrated agricultural activities. The levels of polychlorinated biphenyls (PCBs) were higher in East and South China primarily because of past industrial operations and improper electronic waste processing. The co-existence of organic contaminants was severe in the Yangtze River Delta, Pearl River Delta, and Beijing-Tianjin-Hebei Region, which are the most populated and industrialized regions in China. Integrated biological-chemical remediation technologies, such as surfactant-enhanced bioremediation, have potential uses in the remediation of soil contaminated by multiple contaminants. This critical review highlighted several future research directions including combined pollution, interfacial interactions, food safety, bioavailability, ecological effects, and integrated remediation methods for combined organic pollution in soil.

Human health risks of polycyclic aromatic hydrocarbons in the urban soils of Nanjing, China

Polycyclic aromatic hydrocarbons (PAHs) are a major group of toxic pollutants in urban areas. We calculated the critical concentrations of PAHs in the urban soils of Nanjing, China based on a human health risk assessment. In the study area, the risk was divided into four levels and toxic equivalent values of benzo[a]pyrene (BaP_eq) corresponded to <70ngg^-1, 70-700ngg^-1, 700-7000ngg^-1, and >7000ngg^-1. By this standard, most urban areas in Nanjing fall under level II (potentially low risk), while older urban districts, commercial centers, and transportation centers exceed the critical concentration (level III) at present. Additionally, the correlations between PAH concentrations, factors associated with urbanization, and soil properties were analyzed. Population density and black carbon content were determined to be the key factors involved. Multiple linear regression models and the scenario simulation method were used to predict PAH levels in urban soils through 2030. The results indicated that the future distribution characteristics of soil BaP_eq under various scenarios were different than at present, but PAH concentrations remained stable only under the low‑carbon scenario. Therefore, the consumption of traditional fossil fuels should be controlled and replaced with alternative energy sources. In addition, the growth of traffic land use should be controlled in the southern and southwestern parts of the urban area.

Polycyclic aromatic hydrocarbons contamination in surface soil of China: A review

This paper reviews the concentration, distribution, source, and potential risk of polycyclic aromatic hydrocarbons (PAHs) in surface soils of China through analysis of data from >6000 surface soil samples in nearly 100 references. The mean value of total 16 PAHs was 730ng·g^-1 in surface soil in China, a relatively lower or moderate level than other countries. Based on the Maliszewska-Kordybach classification criteria, the proportions of heavily contaminated, contaminated, weakly contaminated, and non-contaminated soil samples were 21.4%, 11.9%, 49.5%, and 17.2%, respectively. There was a clear geographical distribution, with concentrations of the total 16 PAHs descending in the following order: Northeast China (1467ng·g^-1)>North China (911ng·g^-1)>East China (737ng·g^-1)>South China (349ng·g^-1)>West China (209ng·g^-1). Moreover, it was found that the PAH concentrations in surface soil in China descended along the urban-suburban-rural gradient. The concentration and distribution of PAHs were mainly related to the degree of economic development, population density, climatic conditions, and soil organic matter, and the divergence of regional economic patterns and climatic conditions was the main reason for the observed PAH distribution in the soils. Traffic emissions, coal and biomass combustion mainly contributed to the PAH contamination of surface soil in China during the process of urbanization and industrialization, and the average Benzo(a)pyrene equivalent concentration of ∑PAH_7c (seven carcinogenic PAHs) was 99ng·g^-1, which indicated the soil samples had a small potential carcinogenic risk. Despite soil pollution being generally low, PAH concentrations in some areas were relatively high, therefore it is necessary to produce strategies, such as establishing effective guidelines and developing environmental-friendly technology to reduce PAH emissions, and prevent further contamination.

Contamination, source identification, and risk assessment of polycyclic aromatic hydrocarbons in the soils of vegetable greenhouses in Shandong, China

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed in soil (n=196) and vegetable (n=30) collected from greenhouses, and also in the soil (n=27) collected from agriculture fields close to the greenhouses in Shandong Province, China. The total PAH concentration (∑₁₆PAH) ranged from 152.2µg/kg to 1317.7µg/kg, within the moderate range in agricultural soils of China. Three-ring PAHs were the dominant species, with Phe (16.3%), Ace (13.1%), and Fl (10.5%) as the major compounds. The concentrations of low molecular weight (LMW ≤3 rings) PAHs were high in the east and north of Shandong, while the concentrations of high molecular weight (HMW ≥4 rings) PAHs were high in the south and west of the study area. The PAH level in soils in industrial areas (IN) was higher than those in transport areas (TR) and rural areas (RR). No significant difference in concentration of ∑₁₆PAH and composition was observed in soils of vegetable greenhouses and field soils. PAH concentration exhibited a weakly positive correlation with alkaline nitrogen, available phosphorus in soil, but a weakly negative correlation with soil pH. However, no obvious correlation was observed between PAH concentration and organic matter of soil, or ages of vegetable greenhouses. ∑₁₆PAH in vegetables ranged from 89.9µg/kg to 489.4µg/kg, and LMW PAHs in vegetables positively correlated with those in soils. The sources of PAHs were identified and quantitatively assessed through positive matrix factorization. The main source of PAHs in RR was coal combustion, while the source was traffic in TR and IN. Moreover, petroleum source, coke source, biomass combustion, or mixed sources also contributed to PAH pollution. According to Canadian soil quality guidelines, exposure to greenhouse soils in Shandong posed no risk to human health.

Polycyclic Aromatic Hydrocarbons (PAHs) in Exposed-Lawn Soils from 28 Urban Parks in the Megacity Guangzhou: Occurrence, Sources, and Human Health Implications

Polycyclic aromatic hydrocarbons (PAHs) in urban soils may pose a serious threat to human health via oral ingestion, dermal absorption, and particulate inhalation, especially in public parks and playgrounds, with children and senior citizens showing the highest susceptibility. Several studies have been undertaken identifying PAHs in urban soils, but no studies to date have assessed PAHs in urban parks, in particular in exposed-lawn soils. In recent decades, unprecedented rates of urbanization and industrialization in China have resulted in significant levels of urban environmental pollution. However, concentrations, sources, and the health risk associated with PAH exposure via urban park lawn soils in China remain unknown. The concentrations, sources, and health risk of exposure to 16 PAHs in surface-exposed lawn soils were studied in 28 urban parks in Guangzhou. Concentrations of Σ16PAHs ranged from 76.44 to 890.85 ng/g with a mean of 286.11 ng/g. PAH composition was mostly characterized by 2- and 4-ring PAHs in most sampling parks; Nap, Flua, Pyr, Phe, and Chr were the dominant constituents. Principle component analysis coupled with multivariate linear regression indicated that vehicular and coal combustion emissions contributed to 50.53 and 49.46% of PAHs in Guangzhou's urban park soils, respectively. Total cancer risk (TCR) analysis found that 22 parks (accounting for 78.57% total parks) designed for children's use and general-use park areas presented a potentially high risk (>1 × 10^-4) for all users.

Bioaccumulation and cancer risk of polycyclic aromatic hydrocarbons in leafy vegetables grown in soils within automobile repair complex and environ in Uyo, Nigeria

Using gas chromatography-mass spectrometry and an incremental lifetime cancer risks (ILCRs) assessment model, the bioaccumulation and cancer risk of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) in leafy vegetables (Vernonia amygdalina and Lasianthera africanum) grown in soils within an automobile repair complex environment in Uyo, Nigeria was studied. The total PAHs concentrations recorded for soils ranged from 0.02 to 1.77 mg/kg. The highest level of 1.77 mg/kg was recorded for soils from the main automobile repair complex (site 1). Low molecular weight (LMW) PAHs were predominant although some high molecular weight (HMW) PAHs suites (0.04 mg/kg of chrysene and 0.04 of benzo[k]fluoranthene) were also found in site 1. The leafy vegetables accumulated PAHs were mostly LMW. Accumulation levels were similar but the extent of PAH uptake in vegetables was species dependent as V. amygdalina accumulated more (0.81 mg/kg). The bioaccumulation factors (BaFs) calculated ranged from 0.22 to 0.63 for L. africanum, and 0.18 to 0.55 for V. amygdalina in site 1 where high PAH levels were recorded in soil. Pearson correlation coefficient analysis revealed a strong positive relation between the PAH content of soil and the amount accumulated by L. africanum (r = 0.5) and V. amygdalina (r = 0.8) at p = 0.05. The vegetable's potential to bioaccumulate PAHs is indicative of their use as good bioindicators for PAH contamination in soil. Only two of the USEPA possible human carcinogenic PAHs were detected, and carcinogenic risk assessment based on occupational exposures to soil particles by adults revealed that the total risk level (7.17 × 10^-5) contribution from incidental soil ingestion, dermal contact, and soil particle dust inhalation slightly exceed the USEPA acceptable limits (< 1.00 × 10^-5). There is a need for public education on consumption of vegetables grown in and around automobile repair complexes across Nigeria.

Polycyclic aromatic hydrocarbons in urban green spaces of Beijing: concentration, spatial distribution and risk assessment

A comprehensive investigation of the levels, spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in urban green space soils of Beijing, China, was conducted, and the potential human health risks associated with the levels observed were addressed. The objective of this study was to determine concentration, spatial distribution, and health risk of 15 PAHs in 121 surface soil (0-5 cm) samples collected from four types of green space, such as park green space (PGS), roadside green space (RDS), residential green space (RGS), and attached green space (AGS). Results showed that the highest concentrations of 15 PAHs was in soils of RDS, followed by RGS, PGS, and AGS. The level of PAHs pollution was seriously and mainly distributed in the central and southwest of the city. Incremental lifetime cancer risks (ILCRs) associated with exposures to PAHs in soil was calculated separately for children and adults under normal and extreme conditions. The results showed that ILCRs for urban green space soil of Beijing were low under normal conditions. But individual samples are seriously polluted, and its potential health risks cannot be ignored.

Distribution, compositional pattern and sources of polycyclic aromatic hydrocarbons in urban soils of an industrial city, Lanzhou, China

The level, distribution, compositional pattern and possible sources of polycyclic aromatic hydrocarbons (PAHs) in Lanzhou urban soil of Northwest China were investigated in this study. The total level of 22 PAHs ranged from 115 to 12,100 µg kg(-1) and that of 16 priority PAHs from 82.4 to 10,900 µg kg(-1). Seven carcinogenic PAHs generally accounted for 6.18-57.4% of total 22 PAHs. Compared with data from those reported about urban areas, PAH contamination in Lanzhou urban soils was moderate. Among different functional areas, higher level of PAHs was found along roadsides and in the industrial district (p<0.01), while lower levels were detected in the commercial, park and residential districts. The composition of PAHs was characterized by high molecular weight PAHs (≥4 rings), among which fluoranthene, benz[a]anthracene and phenanthrene were the most dominant components. Correlation analysis suggested that low molecular weight PAHs and high molecular weight PAHs originated from different sources and further corroborated that TOC was an important factor in the accumulation of PAHs in soil. Isomer ratios and principal component analysis indicated that PAHs in urban soil derived primarily from emissions resulting from the combustion of biomass, coal and petroleum products. Toxic equivalent concentrations (BaP(eq)) of soil PAHs ranged from 6.12 to 1302 µg BaP(eq) kg(-1), with a mean of 138 µg BaP(eq) kg(-1). The results suggested that human exposure to those soils which polluted by high concentrations of PAHs through direct ingestion or inhalation of suspended soil particles probably poses a significant risk to human health from the carcinogenic effects of PAHs.

Polycyclic aromatic hydrocarbons in soils from urban to rural areas in Nanjing: Concentration, source, spatial distribution, and potential human health risk

Polycyclic aromatic hydrocarbons (PAHs) have become a major type of pollutant in urban areas and their degree of pollution and characteristics of spatial distribution differ between various regions. We conducted a comprehensive study about the concentration, source, spatial distribution, and health risk of 16 PAHs from urban to rural soils in Nanjing. The mean total concentrations of 16 PAHs (∑16PAHs) were 3330 ng g(-1) for urban soils, 1680 ng g(-1) for suburban soils, and 1060 ng g(-1) for rural soils. Five sources in urban, suburban, and rural areas of Nanjing were identified by positive matrix factorization. Their relative contributions of sources to the total soil PAH burden in descending order was coal combustion, vehicle emissions, biomass burning, coke tar, and oil in urban areas; in suburban areas the main sources of soil PAHs were gasoline engine and diesel engine, whereas in rural areas the main sources were creosote and biomass burning. The spatial distribution of soil PAH concentrations shows that old urban districts and commercial centers were the most contaminated of all areas in Nanjing. The distribution pattern of heavier PAHs was in accordance with ∑16PAHs, whereas lighter PAHs show some special characteristics. Health risk assessment based on toxic equivalency factors of benzo[a]pyrene indicated a low concentration of PAHs in most areas in Nanjing, but some sensitive sites should draw considerable attention. We conclude that urbanization has accelerated the accumulation of soil PAHs and increased the environmental risk for urban residents.