Oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) in urban soils of Bratislava, Slovakia: patterns, relation to PAHs and vertical distribution

Impact of land-use on PAH transfer in sub-surface water as recorded by CaCO3 concretions in urban underground structures (Paris, France)

In densely populated urban areas, the pressure on water resources is considerable and will tend to intensify over the next decades. Preserving water resources therefore seems fundamental, but many questions remain as to the transfer of contaminants to subsurface waters in these largely sealed areas. Because of their toxicity and persistence in the environment, this work focused on the study of polycyclic aromatic hydrocarbons (PAHs), ubiquitous pollutants mainly produced by human activities. To better understand the main factors leading to the retention or transport of these pollutants in urban environments, vertical transects, from the surface to several meters down, were established on three study sites in or near Paris (France), selected according to an urbanization gradient. Soil samples collected at the surface and urban secondary carbonate deposits (USCD), similar to cave speleothems, sampled underground in quarries and aqueducts were analyzed. As the hydrophobic properties of PAHs favor their sorption onto organic matter, the latter was also studied using organic carbon analysis and UV fluorescence spectroscopy. The USCD located closest to the urbanized surface contained high concentrations of PAHs (76.8 ± 5.3 ng g-1), while the USCD located at greater depth with organic soil on the surface contained the lowest amount of PAHs (2.9 ± 0.4 ng g-1), and no PAHs with log KOC > 5. The results highlight the predominant role played by the presence of organic topsoil at the surface in retaining and storing large amounts of PAHs (1914-2595 ng. gsoil-1), particularly the most hydrophobic ones (i.e. 60% of the 15 PAHs are characterized by a Log KOC >5), which are also the most toxic. The lithology and thickness of the bedrock (between the surface and the USCD) also play an important role in the retention of PAHs, particularly those adsorbed on the particulate phase.

Toxicity source apportionment of fugitive dust PM2.5-bound polycyclic aromatic hydrocarbons using multilayer perceptron neural network analysis in Guanzhong Plain urban agglomeration, China

Polycyclic aromatic hydrocarbons (PAHs) in urban fugitive dust, known for their toxicity and ability to generate reactive oxygen species (ROS), are a major public health concern. This study assessed the spatial distribution and health risks of 15 PAHs in construction dust (CD) and road dust (RD) samples collected from June to November 2021 over the cities of Tongchuan (TC), Baoji (BJ), Xianyang (XY), and Xi'an (XA) in the Guanzhong Plain, China. The average concentration of ΣPAHs in RD was 39.5 ± 20.0 μg g-1, approximately twice as much as in CD. Four-ring PAHs from fossil fuels combustion accounted for the highest proportion of ΣPAHs in fugitive dust over all four cities. Health-related indicators including benzo(a)pyrene toxic equivalency factors (BAPTEQ), oxidative potential (OP), and incremental lifetime cancer risk (ILCR) all presented higher risk in RD than those in CD. The multilayer perceptron neural network algorithm quantified that vehicular and industrial emissions contributed 86 % and 61 % to RD and CD BAPTEQ, respectively. For OP, the sources of biomass and coal combustion were the key generator which accounted for 31-54 %. These findings provide scientific evidence for the direct efforts toward decreasing the health risks of fugitive dust in Guanzhong Plain urban agglomeration, China.

The occurrence and sources of PAHs, oxygenated PAHs (OPAHs), and nitrated PAHs (NPAHs) in soil and vegetation from the Antarctic, Arctic, and Tibetan Plateau

Although the fate of PAHs in the three polar regions (Antarctic, Arctic, and Tibetan Plateau) has been investigated, the occurrence and contamination profiles of PAH derivatives such as oxygenated PAHs (OPAHs) and nitrated PAHs (NPAHs) remain unclear. Some of them are more toxic and can be transformed from PAHs in environment. This study explored and compared the concentrations composition profiles and potential sources of PAHs, OPAHs, and NPAHs in soil and vegetation samples from the three polar regions. The total PAH, OPAH, and NPAH concentrations were 3.55-519, n.d.-101, and n.d.-1.10 ng/g dry weight (dw), respectively. The compounds were dominated by three-ring PAHs, and the most abundant individual PAH and OPAH were phenanthrene (PHE) and 9-fluorenone (9-FO), respectively. The sources of PAHs and their derivatives were qualitatively analyzed by the diagnostic ratios and quantified using the positive matrix factorization (PMF) model. The ratios of PAH derivatives to parent PAHs (9-FO/fluorene and 9,10-anthraquinone/anthracene) were significantly higher in the Antarctic samples than in the Arctic and TP samples, implying a higher occurrence of secondary OPAH and NPAH formation in the Antarctic region. To our knowledge, this is the first comparative study that simultaneously investigated the contamination profiles of PAHs and their derivatives in the three polar regions. The findings of this study provide a scientific basis for the development of risk assessment and pollution control strategies in these fragile regions.

Emission factors of oxygenated polycyclic aromatic hydrocarbons from ships in China

The rapid growth of maritime traffic, transportation, and fishery activities has increased shipping emissions and degraded the air quality in coastal areas. As a result, controlling ocean-based pollution sources have become increasingly important. This study investigated the real-world emission characteristics of oxygenated polycyclic aromatic hydrocarbons (OPAHs, a group of highly toxic semi-volatile organic compounds) from five types of offshore ships using diesel oil: small and medium fishing ships, tug boats, ferry, and engineering ships, under various driving mode. Both gaseous and particle emission factors (EF) of four specific OPAHs were determined in our study. Among the OPAHs species emitted from ships, 9-fluorenone (9FO; 72%) and anthrathrace-9,10-quinone (ATQ; 25%) were the most abundant. The arithmetic mean of the sum of gaseous OPAHs EFs for all ships in this study was 2.5 ± 4.4 mg/kg fuel burned, and the mean particulate OPAHs EF was 4.7 ± 7.9 mg/kg. Small fishing ships had the highest total OPAHs EFs (31.0 ± 17.0 mg/kg). Apart from small fishing ships, there was no significant difference in the total EF of OPAHs for the other four types of ships. The emissions of the four OPAHs are predominantly in the particulate phase. There were no significant differences in the emissions of the four OPAHs under different driving mode. According to estimates, the annual OPAH emissions from the four types of ships in Hainan in 2017 were approximately 4.2 (range: 2.7-7.0) tons, dwarfing the OPAH emissions from diesel-powered on-road vehicles in China (23.5 kg).

Atmospheric occurrences and health risk assessment of polycyclic aromatic hydrocarbons and their derivatives in a typical coking facility and surrounding areas

Coking facilities release large quantities of polycyclic aromatic hydrocarbons (PAHs) and their derivatives into the ambient air. Here we examined the profiles, spatial distributions, and potential sources of atmospheric PAHs and their derivatives in an industrial coking plant and its surrounding environment (gaseous and particulate). The mean concentrations of PAHs, nitrated PAHs (NPAHs), chlorinated PAHs (ClPAHs), and brominated PAHs (BrPAHs) in the air of the coking facility were 923, 23.8, 16.7 and 4.25 ng m-³, respectively, 1-2 orders of magnitude higher than those in the surrounding area and the control area. Linear regressions between contaminant concentrations and distance from the coking facility suggested that the concentrations of PAHs (r2 = 0.82, p < 0.05), NPAHs (r2 = 0.77, p < 0.01), and BrPAHs (r2 = 0.62, p < 0.01) were negatively correlated with distance. Additionally, the particle-bound fractions of PAHs and their derivatives were significantly correlated with their molecular weights (p < 0.01). Based on the calculation of the gas/particle partitioning coefficients (log KP) for PAHs and their derivatives and the corresponding subcooled liquid vapor pressures (log PL), the slope values for PAHs, NPAHs, ClPAHs, and BrPAHs ranged from -1 to -0.6, indicating that deposition of PAHs and their derivatives occurred through both adsorption and absorption. Five emissions sources were identified by positive matrix factorization (PMF), including coking emissions, oil pollution, industrial and combustion sources, secondary formation, and traffic emissions, with coking emissions accounting for more than 50% of total emissions. Furthermore, the results of the health risks assessment suggested that atmospheric PAHs and their derivatives in the coke plant and surrounding area negatively impacted human health.

Toxicity evaluation of polycyclic aromatic hydrocarbons (PAHs) in soils of coal chemical industry areas, North China

Objectives of this study were to investigate the concentrations, distributions, toxicities, and risk assessment of 16 polycyclic aromatic hydrocarbons in surface soils surrounding a coal chemical industrial zone in the southeast of Shanxi province, China. A total of 52 topsoil samples were collected from different land-use areas: cereal agriculture, roadsides, and parkland. Results show that the total PAHs (∑₁₆PAHs) ranged from 3.87 × 10³ to 116 × 10³ µg kg^-1 and that the total carcinogenicity PAHs (∑BPAHs) ranged from 3.11 × 10³ to 94.2 × 10³ µg kg^-1, with the highest concentration of ∑₁₆PAHs noted in the RS samples, followed by PS and AS. The entire risk quotient of all PAH maximum permissible concentrations (RQ∑PAH_MPCi) was greater than 1.0, and the minimum concentration entire risk quotient (RQ∑PAH_NCi) of 84.3% of all samples was higher than 800. The value of the total toxicity equivalent concentration of PAH (PAHBapeq) for areas surrounding the coal chemical industrial zone was higher than the value of the standard level, and the incremental lifetime cancer risk (ILCR) far exceeds the U.S. EPA's risk standard. The toxic properties of PAHs indicated that the soils in the survey areas have a high risk to human health and the environment.

Bioaccessibility and bioavailability of NPAHs in soils using in vitro-in vivo assays: Comparison of laboratory and outdoor environmental aging effect

Aging process is one of the most important factors that markedly reduces bioaccessibility and bioavailability (bioac-bioav) of organic contaminants. However, only few data on comparison of the effects of laboratory artificial aging (LAA) and outdoor environmental aging (OEA) processes on nitrated polycyclic aromatic hydrocarbons (NPAHs) bioac-bioav are available. In the current study, oral bioac-bioav of NPAHs in LAA and OEA soils (aging time intervals: 0, 45, 90, 120 and 150 d) were measured by in vitro traditional Fed ORganic Estimation human Simulation Test (FOREhST) and Tenax improved FOREhST (TI-FOREhST) methods, and in vivo mouse model. Tenax significantly increased the bioaccessibility of NPAHs in freshly spiked and aging soils from 0.3-40.9 % to 15.6-95.3 %, and 0.3-40.9 % to 1.0-84.5 %, respectively. Aging significantly reduced the NPAHs bioaccessibility (from 36.5 % to 10.7 %, and 12.1 % to 5.1 % as measured by FOREhST and TI-FOREhST, respectively) and bioavailability (from 27.7 % to 9.9 %, as measured by mouse model). The changes in bioac-bioav were mainly observed within the first 120 d of aging. The statistical analyses of NPAHs bioac-bioav showed no significant difference (p > 0.05) among the aging time intervals in LAA and OEA soils, which demonstrated that the LAA can relatively represent the OEA. Determination of TOC content in LAA and OEA soil can intuitively reflect whether the difference of NPAHs bioac-bioav between two aging treatment groups is significant. The mean bioaccessibility of NPAHs in soil measured by TI-FOREhST (mean 20.6 %) is closer to the bioavailability measured by mouse model (mean 19.4 %), indicating that Tenax improved in vitro method is more reliable than traditional methods, to predict the bioavailability of NPAHs.

Co-occurrence of polycyclic aromatic hydrocarbons and their oxygenated derivatives in indoor dust from various microenvironments in Guangzhou, China: levels, sources, and potential human health risk

For decades, the presence and potential health risk of polycyclic aromatic hydrocarbons (PAHs) in indoor dust have been extensively investigated while with limited attention to oxygenated PAHs (OPAHs). In this study, we collected 45 indoor dust from four microenvironments in Guangzhou City, China, and then focused on the co-occurrence of 16 PAHs and 8 OPAHs and their potential carcinogenic risk to humans. The ΣPAHs concentrations, dominated by 4-6 ring PAHs, ranged from 1761 to 14,290 ng/g (mean of 6058 ng/g) without significant difference in the different microenvironments (Tukey, p > 0.05). The OPAHs were observed with concentrations from 250 to 5160 ng/g (mean of 1646 ng/g), and anthraquinone (AQ) was identified as the main OPAHs with significantly high levels in the residential environment than in instrumental rooms. Notably, AQ dominated over the other target analytes in dust in this study. Our results indicated that PAHs and OPAHs in indoor dust were from outdoor environments, which mainly originated from vehicular exhaust and biomass/coal combustion. A potential cancer risk of PAHs and OPAHs to local adults and children was observed via inhalation, ingestion, and dermal absorption, with the main contribution from benzo[a]pyrene and dibenz[a,h]anthracene.

An evaluation of the impact of traffic on the distribution of PAHs and oxygenated PAHs in the soils and moss of the southeast Tibetan Plateau

Contaminants in high-altitude mountains such as the Tibetan Plateau (TP) have attracted extensive attention due to their potential impact on fragile ecosystems. Rapid development of the economy and society has promoted pollution caused by local traffic emissions in the TP. Among the pollutants emitted by traffic, polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) are of particular concern due to their high toxicity. The TP provides an environment to explore the degree and range of contribution for traffic-induced PAHs and OPAHs. In this study, soils and moss were collected at different altitudes and distances from the G318 highway in the southeast TP. The total concentrations of PAHs (∑₁₆PAHs) and OPAHs (∑₆OPAHs) in soils were in the range of 3.29-119 ng/g dry weight (dw) and 0.54-9.65 ng/g dw, respectively. ∑₁₆PAH and ∑₆OPAH concentrations decreased logarithmically with increasing distance from traffic. A significantly positive correlation between ∑₁₆PAHs and altitude was found at sampling points closest to traffic. Dominant PAHs constituents in soil and moss included chrysene (CHR), benzo[g,h,i]perylene (BghiP), and benzo[b]fluoranthene (BbF); prevalent OPAH compounds were 9-fluorenone (9-FO) and 9,10-anthraquinone (ATQ). These compounds were related to characteristics of traffic emissions. The multiple diagnosis ratio and correlation analysis showed that exhaust emissions were the main source of the PAHs and OPAHs in the studied environment. PMF modeling quantification of the relative contribution of traffic emissions to PAHs in roadside soils was 45 % on average. The present study characterized the extent and range of traffic-induced PAH and OPAH emissions, providing valuable information for understanding the environmental behaviors and potential risks of traffic-related contaminants in high-altitude areas.

A comparative study of the sorption of O-PAHs and PAHs onto soils to understand their transport in soils and groundwater

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivates (O-PAHs) are identified in soils and groundwater of industrialized sites and contribute to the risk for Humans and the Environment. Nevertheless, data are scarce in literature concerning their retention and transfer in soils and no soil - water partition coefficients are available for these compounds. Sorption of two PAHs, fluorene and acenaphthene and two O-PAHs, 9H-fluorenone and dibenzofuran onto two soils with different organic carbon contents was evaluated and compared by determining their sorption isotherms. Effect of ionic strength and liquid to solid ratio, on fluorene and fluorenone sorption was also evaluated. Sorption equilibrium is achieved within less than 24 hr of mixing and linear sorption models best fit the isotherm data. Acenaphthene and dibenzofuran are similarly sorbed onto the soil. K_D of fluorene is higher than the one of fluorenone, showing a smaller affinity of fluorenone towards the solid phase. This means that O-PAH could form larger contamination plumes in groundwater than PAHs. Decreasing the L/S ratio from 100 to 50 and 30, increases the sorption of fluorenone onto the soil by 56% and 67% respectively, while the sorption of fluorene is slightly increased. Increasing the ionic strength of the aqueous phase also modifies the sorption of fluorenone, contrary to the sorption of fluorene which is slightly affected.

Oxygenated and Nitrated Polycyclic Aromatic Hydrocarbons: Sources, Quantification, Incidence, Toxicity, and Fate in Soil—A Review Study

The genotoxicity, mutagenesis, and carcinogenic effects of polycyclic aromatic hydrocarbon (PAH) derivatives may exceed the parent PAHs. However, their influence on the soil environment has not been explored to a large extent. Oxygenated polycyclic aromatic hydrocarbons (OPAHs) and nitrated polycyclic aromatic hydrocarbons (NPAHs) are typical polar substituted compounds. We offer a review of the literature on the sources, quantification, incidence, toxicity, and transport of these compounds in soil. Although their environmental concentrations are lower than those of their parent compounds, they exert higher toxicity. Both types of substances are basically related to carcinogenesis. OPAHs are not enzymatically activated and can generate reactive oxygen species in biological cells, while NPAHs have been shown to be mutagenic, genotoxic, and cytotoxic. These compounds are largely derived from the transformation of PAHs, but they behave differently in soil because of their higher molecular weight and dissimilar adsorption mechanisms. Therefore, specialized knowledge of model derivatives is required. We also made recommendations for future directions based on existing research. It is expected that the review will trigger scientific discussions and provide a research basis for further study on PAH derivatives in the soil environment.

Nitro- and oxy-PAHs in grassland soils from decade-long sampling in central Europe

Long-term exposure to polycyclic aromatic hydrocarbons (PAHs) and their nitrated (NPAHs) and oxygenated (OPAHs) derivatives can cause adverse health effects due to their carcinogenicity, mutagenicity and oxidative potential. The distribution of PAH derivatives in the terrestrial environment has hardly been studied, although several PAH derivatives are ubiquitous in air and long-lived in soil and water. We report the multi-annual variations in the concentrations of NPAHs, OPAHs and PAHs in soils sampled at a semi-urban (Mokrá, Czech Republic) and a regional background site (Košetice, Czech Republic) in central Europe. The concentrations of the Σ₁₈NPAHs and the Σ₁₁₊₂OPAHs and O-heterocycles were 0.31 ± 0.23 ng g^-1 and 4.03 ± 3.03 ng g^-1, respectively, in Košetice, while slightly higher concentrations of 0.54 ± 0.45 ng g^-1 and 5.91 ± 0.45 ng g^-1, respectively, were found in soil from Mokrá. Among the 5 NPAHs found in the soils, 1-nitropyrene and less so 6-nitrobenzo(a)pyrene were most abundant. The OPAHs were more evenly distributed. The ratios of the PAH derivatives to their parent PAHs in Košetice indicate that they were long-range transported to the background site. Our results show that several NPAHs and OPAHs are abundant in soil and that gas-particle partitioning is a major factor influencing the concentration of several semi-volatile NPAHs and OPAHs in the soils. Complete understanding of the long-term variations of NPAH and OPAH concentrations in soil is limited by the lack of kinetic data describing their formation and degradation.

Prediction of •OH-Initiated and •NO3-Initiated Transformation Products of Polycyclic Aromatic Hydrocarbons by Electronic Structure Approaches

The abiotic reaction products of polycyclic aromatic hydrocarbons (PAHs) with hydroxyl radicals (^•OH) and nitrate radicals (^•NO₃) are nitro-, oxygen-, and hydroxyl-containing PAHs (NPAHs, OPAHs, and OHPAHs). Four methods of the highest occupied molecular orbital (HOMO), Fukui function (FF), dual descriptor (DD), and population of π electrons (PP-π) are selected to predict the chemical reactivity of PAHs attacked by ^•OH and ^•NO₃ in this study. The predicted ^•OH-initiated and ^•NO₃-initiated transformation products are compared with the main PAH transformation products (PAH-TPs) observed in the laboratory. The results indicate that PP-π and DD approaches fail to predict the transformation products of fused PAHs containing five-membered rings. By predicting the PAH-TPs of 13-14 out of the 15 parent PAHs accurately, HOMO and FF methods were shown to be suitable for predicting the transformation products formed from the abiotic reactions of fused PAHs with ^•OH and ^•NO₃.

Optimization of PAHs oxidation from contaminated soil using modified nanoscale zero-valent iron combined with potassium permanganate

A novel synergistic oxidation technology based on modified nanoscale zero-valent iron (nZVI) and potassium permanganate (KMnO₄) was developed for polycyclic aromatic hydrocarbons (PAHs) remediation in actual contaminated soil. In this study, three surfactants were used as dispersants to modify nZVI, including poly acrylic (PAA), sorbitan monolaurate (SPAN-20) and sugar esters (SE). The following parameters were studied to optimize the coupling oxidation process: dispersants/nZVI ratio, dosage of oxidant based on soil oxidation demand (SOD), amount of modified nanomaterials added in the coupling system. By using zeta potential, XRD, SEM, BET characterization methods, the results show that nZVI successfully coated with 5% PAA, 20% SE and 10% SPAN-20 have the best stability and mobility to effectively reduce the agglomeration effect. The conditions for treating PAH contaminated soil with the three best modified nanocomposites combined with KMnO₄ were studied. The optimal conditions were defined as [SE-nZVI] = 10% and [KMnO₄] = 40% SOD_max for 24 h at 25 °C. The synergistic oxidation process under these optimal conditions and the two unoptimized processes of KMnO₄ and nZVI-KMnO₄ degraded 85%, 58.9% and 62% of PAHs, respectively. This showed that the treatment effect of the optimized oxidation process was improved by 1.3-1.5 times. Further, by using gas chromatography-mass spectrometry (GC-MS), adsorption and electrophilic substitution reaction were speculated as the oxidation mechanism of PAHs treated by the coupling system of SE-nZVI-KMnO₄. PAHs could finally be decomposed into 9-methylene-9H-fluorene, fluoranthene and 1,5-diphenyl-1,4-pentadiyn-3-one and reached a safer status in the soil.

Reducing Phenanthrene Contamination in Trifolium repens L. With Root-Associated Phenanthrene-Degrading Bacterium Diaphorobacter sp. Phe15

Some root-associated bacteria could degrade polycyclic aromatic hydrocarbons (PAHs) in contaminated soil; however, their dynamic distribution and performance on root surface and in inner plant tissues are still unclear. In this study, greenhouse container experiments were conducted by inoculating the phenanthrene-degrading bacterium Diaphorobacter sp. Phe15, which was isolated from root surfaces of healthy plants contaminated with PAHs, with the white clover (Trifolium repens L.) via root irrigation or seed soaking. The dynamic colonization, distribution, and performance of Phe15 in white clover were investigated. Strain Phe15 could efficiently degrade phenanthrene in shaking flasks and produce IAA and siderophore. After cultivation for 30, 40, and 50 days, it could colonize the root surface of white clover by forming aggregates and enter its inner tissues via root irrigation or seed soaking. The number of strain Phe15 colonized on the white clover root surfaces was the highest, reaching 6.03 Log CFU⋅g^–1 FW, followed by that in the roots and the least in the shoots. Colonization of Phe15 significantly reduced the contents of phenanthrene in white clover; the contents of phenanthrene in Phe15-inoculated plants roots and shoots were reduced by 29.92–43.16 and 41.36–51.29%, respectively, compared with the Phe15-free treatment. The Phe15 colonization also significantly enhanced the phenanthrene removal from rhizosphere soil. The colonization and performance of strain Phe15 in white clove inoculated via root inoculation were better than seed soaking. This study provides the technical support and the resource of strains for reducing the plant PAH pollution in PAH-contaminated areas.

Characterization of polycyclic aromatic compounds in historically contaminated soil by targeted and non-targeted chemical analysis combined with in vitro bioassay

Soil samples from a contaminated site in Sweden were analyzed to identify the presence of 78 polycyclic aromatic compounds (PACs) using gas chromatography coupled with mass spectrometry (GC-MS). The target analysis revealed large contributions not only from polycyclic aromatic hydrocarbons (PAHs), but also from alkylated- and oxygenated-PAHs (alkyl- and oxy-PAHs, respectively), and N-heterocyclics (NPACs). PAC profiles indicated primarily pyrogenic sources, although contribution of petrogenic sources was also observed in one sample as indicated by a high ratio of alkylated naphthalene compared to naphthalene. The aryl hydrocarbon receptor (AhR)-activity of the soil extracts was assessed using the H4IIe-pGudluc 1.1 cells bioassay. When compared with the calculated total AhR-activity of the PACs in the target list, 35-97% of the observed bioassay activity could be explained by 62 PACs with relative potency factors (REPs). The samples were further screened using GC coupled with Orbitrap™ high resolution MS (GC-HRMS) to investigate the presence of other PACs that could potentially contribute to the AhR-activity of the extracts. 114 unique candidate compounds were tentatively identified and divided into four groups based on their AhR-activity and environmental occurrence. Twelve substances satisfied all the criteria, and these compounds are suggested to be included in regular screening in future studies, although their identities were not confirmed by standards in this study. High unexplained bio-TEQ fractions in three of the samples may be explained by tentatively identified compounds (n = 35) with high potential of being toxic. This study demonstrates the benefit of combining targeted and non-targeted chemical analysis with bioassay analysis to assess the diversity and effects of PACs at contaminated sites. The applied prioritization strategy revealed a number of tentatively identified compounds, which likely contributed to the overall bioactivity of the soil extracts.

Polycyclic aromatic hydrocarbons (PAHs) in soils of an industrial area in semi-arid Uzbekistan: spatial distribution, relationship with trace metals and risk assessment

The concentrations, composition patterns, transport and fate of PAHs in semi-arid and arid soils such as in Central Asia are not well known. Such knowledge is required to manage the risk posed by these toxic chemicals to humans and ecosystems in these regions. To fill this knowledge gap, we determined the concentrations of 21 parent PAHs, 4,5-methylenephenanthrene, 6 alkylated PAHs, and biphenyl in soils from 11 sampling locations (0-10, 10-20 cm soil depths) along a 20-km transect downwind from the Almalyk metal mining and metallurgical industrial complex (Almalyk MMC), Uzbekistan. The concentrations of Σ29 PAHs and Σ16 US-EPA PAHs were 41-2670 ng g^-1 and 29-1940 ng g^-1, respectively. The highest concentration of Σ29 PAHs occurred in the immediate vicinity of the copper smelting factory of the Almalyk MMC. The concentrations in topsoil decreased substantially to a value of ≤ 200 ng g^-1 (considered as background concentration) at ≥ 2 km away from the factory. Low molecular weight PAHs dominated the PAH mixtures at less contaminated sites and high molecular weight PAHs at the most contaminated site. The concentration of Σ16 US-EPA PAHs did not exceed the precautionary values set by the soil quality guidelines of, e.g., Switzerland and Germany. Similarly, the benzo[a]pyrene equivalent concentration in soils near the Almalyk MMC did not exceed the value set by the Canadian guidelines for the protection of humans from carcinogenic PAHs in soils. Consequently, the cancer risk due to exposure to PAHs in these soils can be considered as low.

Remediation of polycyclic aromatic hydrocarbons by sulfate radical advanced oxidation: Evaluation of efficiency and ecological impact

Remediation of polycyclic aromatic hydrocarbon (PAH) contamination in soil remains expensive and difficult. Sulfate radical advanced oxidation processes (SR-AOPs) can be used for in situ PAH oxidation but their efficiency and ecological impacts require evaluation. Here, we tested the remediation efficiency and ecological impacts of an SR-AOP combining sodium persulfate and ferrous sulfate (FS), the FS SR-AOP with the chelating agent citric acid (FS+CA), and the FS SR-AOP with chelating agent and the surfactant IGEPALCA-720 (FS+CA+IG) compared with natural attenuation (control, CK). We measured PAH, soil physicochemical properties (pH, soil organic matter [SOM]), and soil biological properties (polyphenol oxidase [PPO] activity, peroxidase [POD] activity, soil microbes) in contaminated soil samples after incubation with FS, FS+CA, FA+CA+IG, or CK for 1, 15, and 30 d. Compared with CK, all SR-AOPs significantly decreased PAH after 1 d, with FS+CA+IG showing the highest efficiency (80.8%) and PAH removal peaking at 15 d. FS+CA+IG treatment reduced SOM the least and soil pH the most; after 30 d, SOM recovered to ~80% of the level observed in CK, but soil pH decreased further. PPO and POD activities were highest after 15 and 30 d of FS+CA+IG treatment. Real-time quantitative PCR demonstrated that SR-AOPs significantly decreased quantities of PAH-degrading bacteria, soil bacteria, fungi, and actinobacteria at 1 d, but after 30 d, the microbes recovered to levels similar to those observed in CK, with no significant differences among SR-AOPs. SR-AOPs reduced bacterial diversity and changed the dominant phylum from Acidobacteria to Firmicutes. In summary, SR-AOP treatment with both the chelating agent and the surfactant produced the best PAH removal and least SOM destruction but the largest pH decrease, although some factors recovered with longer incubation. This study provides key information for improving PAH remediation and evaluating its ecological impact.

Toxicity evaluation of the metabolites derived from the degradation of phenanthrene by one of a soil ubiquitous PAHs-degrading strain Rhodococcus qingshengii FF

Rhodococcus qingshengii strain FF is a soil ubiquitous strain that has a high polycyclic aromatic hydrocarbons (PAHs) biodegradation capability. In this work, phenanthrene was used as a PAH model compound. The accumulated pattern of the metabolites of phenanthrene by strain FF was investigated, and their toxicity to Vibrio fischeri, effect on microbiota diversity of farmland soil and influence on seed of wheat were evaluated. Total of 29 main intermediates were observed for the phenanthrene degradation process. Pyrogallol was the predominant accumulated metabolite, and 59% of the accumulated metabolites were oxygen-containing PAHs that have only one benzene ring. The acute toxicity assessment showed the accumulated metabolites in later phase were more toxic to Vibrio fischeri. Microbe and wheat seed response to the different stages of phenanthrene metabolites indicated pollution significantly decreased microbial richness and evenness of farmland soil and lower germinal length, root length or root number of wheat seed. These results indicated that not only the elimination of PAHs, but also the easily accumulated metabolites produced during the PAHs degradation process should be paid enough attention. The comprehensive evaluation of toxicity during the degradation process would provide useful information for the use of microbe-orientated strategies in PAHs bioremediation.

Global distribution of oxygenated polycyclic aromatic hydrocarbons in mineral topsoils

Hazardous oxygenated polycyclic aromatic hydrocarbons (OPAHs) originate from combustion (primary sources) or postemission conversion of polycyclic aromatic hydrocarbons (PAHs) (secondary sources). We evaluated the global distribution of up to 15 OPAHs in 195 mineral topsoils from 33 study sites (covering 52° N-47° S, 71° W-118 °E) to identify indications of primary or secondary sources of OPAHs. The sums of the (frequently measured 7 and 15) OPAH concentrations correlated with those of the Σ16EPA-PAHs. The relationship of the Σ16EPA-PAH concentrations with the Σ7OPAH/Σ16EPA-PAH concentration ratios (a measure of the variable OPAH sources) could be described by a power function with a negative exponent <1, leveling off at a Σ16EPA-PAH concentration of approximately 400 ng g^-1 . We suggest that below this value, secondary sources contributed more to the OPAH burden in soil than above this value, where primary sources dominated the OPAH mixture. This was supported by a negative correlation of the Σ16EPA-PAH concentrations with the contribution of the more readily biologically produced highly polar OPAHs (log octanol-water partition coefficient <3) to the Σ7OPAH concentrations. We identified mean annual precipitation (Spearman ρ = .33, p < .001, n = 143) and clay concentrations (ρ = .55, p < .001, n = 33) as important drivers of the Σ7OPAH/Σ16EPA-PAH concentration ratios. Our results indicate that at low PAH contamination levels, secondary sources contribute considerably and to a variable extent to total OPAH concentrations, whereas at Σ16EPA-PAH contamination levels >400 ng g^-1 , there was a nearly constant Σ7OPAH/Σ16EPA-PAH ratio (0.08 ± 0.005 [SE], n = 80) determined by their combustion sources.

Nitrated- and oxygenated-polycyclic aromatic hydrocarbon in urban soil from Nepal: Source assessment, air-soil exchange, and soil-air partitioning

In contrast to more frequently investigated priority pollutants, such as polycyclic aromatic hydrocarbons (PAHs), only little is known about the fate and distribution of nitrated- and oxygenated-PAHs (NPAHs and OPAHs) in urban soils, particularly in Indian sub-continent. Moreover, experimental data on air-soil exchange and soil-air partitioning are also lacking, which is critical in assessing the partitioning, fugacity coefficient, and secondary emission of PAH-derivatives. Hence, this article provides an insight into the fate, sources, air-soil exchange, and soil-air partitioning of PAH-derivatives on a molecular basis. Prospective health risk due to their exposure has also been discussed. The result showed that PAH-derivatives had significantly polluted all four Nepalese cities. Ʃ₁₅NPAHs and Ʃ₂OPAHs in soil were 4 and 20 times lower than their parent-PAHs, and ranged 396-2530 ng/g (median 458 ng/g) and 91.9-199 ng/g (median 94.9 ng/g), respectively. Ʃ₁₅NPAHs was higher than a few global studies, while Ʃ₂OPAHs was lower than some of the less urbanized/remote areas worldwide. The 6-Nitobenzo[a]pyrene (6-NBaP) was most abundant in soil, and accounted for 10-12% of Ʃ₁₅NPAHs, while Benzanthrone (BZONE) exceeded among OPAHs, and represented 71-76% of Ʃ₂OPAHs, respectively. Source identification study indicated that direct emissions from domestic/residential cooking and heating and secondary formations are the essential sources of derivative chemicals in soil. Fugacity fraction ratio (f_ratio) indicated volatilization from the soil. The soil-air partitioning study showed sorption by soil organic matter/black carbon has little role in soil-air partitioning of PAH-derivatives in Nepal's urban soil. The toxicity equivalency quotients (TEQs) of NPAHs (314 ± 102 ng/g) was estimated slightly higher than their parent-PAHs (294 ± 121 ng/g) suggesting a relatively higher risk of soil toxicity in Nepal.

Quantitative biomonitoring of polycyclic aromatic compounds (PACs) using the Sydney rock oyster (Saccostrea glomerata)

Increasing our understanding of the bioavailable fractions of polycyclic aromatic compounds (PACs) in an aquatic environment is important for the assessment of the environmental and human health risks posed by PACs. More importantly, the behaviour of polar polycyclic aromatic hydrocarbons (polar PAHs), which are metabolites of legacy PAHs, are yet to be understood. We, therefore, carried out a study involving Sydney rock oysters (Saccostrea glomerata) sourced from two locations, that had been exposed to PAH contamination, within an Australian south-east estuary. Biomonitoring of these oysters, following relocation from the estuary to a relatively isolated waterway, was done at 24 and 72 h after deployment and subsequently at 7, 14, 28, 52 and 86 days. Control samples from Camden Haven River were sampled for PAC analyses just before deployment, after 28 days and at the end of the study (day 86). Lipid-normalised concentrations in oyster tissues across the 86-day sampling duration, elimination rate constants (k₂), biological half-lives (t_1/2) and time required to reach 95% of steady-state (t₉₅) were reported for parent PAHs and the less-monitored polar PAHs including nitrated/oxygenated/heterocyclic PAHs (NPAHs, oxyPAHs and HPAHs) for the three differently sourced oyster types. Most of the depurating PAHs and NPAHs, as well as 9-FLO (oxyPAH), had k₂ values significantly different from zero (p < 0.05). All other oxyPAHs and HPAHs showed no clear depuration, with their concentrations remaining similar. The non-depuration of polar PAHs from oyster tissues could imply greater human health risk compared to their parent analogues.

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.

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.

Hydroxylated polycyclic aromatic hydrocarbons in surface soil in an emerging urban conurbation in South China

To investigate the effects of human activity on contaminants in regional soil, hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) were measured in 187 surface soil samples of different land-use types collected from the Pearl River Delta (PRD), South China. The concentrations of Σ₉OH-PAH (sum of nine target analytes) ranged from 0.36 to 252ng/g (median: 5.98ng/g), with phenanthrene derivatives as the dominant components, accounting for ~70%. Among different land-use types, residency soil contained the highest levels of Σ₉OH-PAH (median: 11.3ng/g), followed by landfill soil (9.28ng/g), industry soil (7.51ng/g), agriculture soil (6.04ng/g), forestry soil (4.28ng/g) and drinking water source soil (4.20ng/g). A higher value was also observed in soil from the central PRD (6.94ng/g) than the surrounding areas (5.94ng/g), which indicated a significant impact of human activity on OH-PAH contamination in soil. Correlation and principal component analysis indicated that OH-PAHs in PRD soil are likely derived from the degradation of their parent PAHs in the atmosphere and/or soil and not directly from the same source as the parent PAHs. The ratios of OH-PAHs to their parent PAHs also varied among different land-use types, which may be partly attributed to the different populations of microorganisms in different soil types or the different chemical properties of PAHs and their metabolites.

Polycyclic aromatic compounds (PAHs, oxygenated PAHs, nitrated PAHs and azaarenes) in soils from China and their relationship with geographic location, land use and soil carbon fractions

The assessment of risks arising from polycyclic aromatic compounds (PACs), particularly from the polar PACs [azaarenes (AZAs), oxygenated PAHs (OPAHs), nitrated PAHs (NPAHs)] requires us to understand the drivers of their spatial distribution. We determined the concentrations of 29 PAHs, 4 AZAs, 15 OPAHs and 11 NPAHs and their relationships with land use (urban vs. rural and forest vs. agriculture), climate (Qinghai-Tibetan plateau, temperate, sub tropical and tropical) and three C fractions (soil organic C, char, soot) in 36 mineral topsoils (0-5 cm) of China. The average concentrations±standard deviation of the Σ29PAHs, Σ16PAHs, Σ4AZAs, Σ15OPAHs and Σ11NPAHs were 352 ± 283, 206 ± 215, 5.7 ± 3.7, 108 ± 66.8 and 3.2 ± 3.4 ng g^-1, respectively. PAH, OPAH, NPAH and AZA concentrations were frequently not correlated within or across the regions reflecting different sources and turnover of PAHs and their derivatives. Temperate urban soils showed the highest and tropical rural soils the lowest concentrations of PACs. Forest soils had higher PACs concentrations than agricultural soils. Longitude correlated positively with the ∑29PAHs concentrations, because of increasing emissions of PAHs from East to West. The tropical and plateau regions with the lowest PAH concentrations, were dominated by low molecular weight PAHs (LMW-PAHs) with LMW/high molecular weight (HMW)-PAHs ratios >1, while the other two climatic regions with more industrial sites showed the opposite. Latitude correlated with NPAHs likely because of enhanced formation by photochemical reactions during transport in the atmosphere. The concentrations of the ∑29PAHs, ∑4AZAs, ∑15OPAHs, ∑11NPAHs and their individual components were only occasionally correlated with those of carbon fractions (soil organic C, soot and char) suggesting a small role of soil C pool properties in driving PACs concentrations. Our results demonstrate that the strongest drivers of PACs concentrations are land use and distance to PAC emission sources followed by climate and size and properties of the soil organic C pool.

Vertical migration from surface soils to groundwater and source appointment of polycyclic aromatic hydrocarbons in epikarst spring systems, southwest China

Understanding the transfer process of polycyclic aromatic hydrocarbons (PAHs) in the karst terrain is of great importance to their ecological risk assessments, however, the impact of the vertical transfer of the soil PAHs on the underground water is largely unknown in the karst system. Here, the vertical distribution and the seasonal variation of 16 PAHs in the soils and the water of 4 epikarst spring catchments in Southwest China were investigated. The total concentration of the PAHs ranged within 61-3285 ng g^-1 in the soils, and 341-4969 ng L^-1 in the spring water. The vertical distribution of the PAHs in soils varied with ring numbers and altitude of the catchment. PAHs concentrations were linearly related with the total organic carbon (TOC) at different depths in the catchments 563-783 m above the sea level (A.S.L.). However, no correlation with TOC was observed in the catchment of a high altitude (2090 m A.S.L.), because the large water flux led to the fast migration of the 2-3 rings PAHs in soils. The PAHs in soils and springs were mainly derived from the combustion of grass/wood/coal, closely related with the primary fossil fuels used in this area. This study demonstrate that the groundwater was heavily polluted by PAHs in the karst terrains of Southwest China, due to the vertical transfer of PAHs from the surface soils, and effective protection was urgently needed.

Emission behaviors of nitro- and oxy-polycyclic aromatic hydrocarbons during pyrolytic disposal of electronic wastes

Emission factors (EFs) of polycyclic aromatic hydrocarbon (PAH) derivatives (12 nitro-PAHs and 4 oxy-PAHs) during the pyrolysis of two types of electronic waste (E-waste) were measured. Compositional profile, particle size distribution, gas-particle partitioning, correlations with precursor species and influences of pyrolytic temperature were investigated. The derivative products were dominated by oxy-PAHs. The averaged EFs of oxy-PAHs were 3.37 ± 4.10 μg/g and 32.6 ± 18.1 μg/g for PWBs and plastic casings, respectively, and those of nitro-PAHs were 85.7 ± 92.4 ng/g and 83.3 ± 69.7 ng/g, respectively. Most EFs of derivative species significantly correlated with their corresponding parent PAHs (p < 0.05), except a few cases, indicating formation of derivatives via related reactions of parent species. Most nitro-PAHs occurred in fine particles with the size < 2.1 μm, and oxy-PAHs were prevailing in fine particles with the size between 0.4 μm and 2.1 μm. Proportions of oxy-PAHs in particulate phase, especially those with higher molecular weight, were noticeably greater than those of the corresponding parent species. Below 480 °C, there was no evident difference in the EFs of PAH derivatives, while the EFs noticeably increased from 520 °C. With the increasing temperature, the majority of oxy-PAHs still occurred on finer particles, while the contribution of coarser particles tended to increase.

Embryonic exposure to oxy-polycyclic aromatic hydrocarbon interfere with pancreatic β-cell development in zebrafish via altering DNA methylation and gene expression

Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are a class of anthropogenic, persistent and very toxic PAH contaminant associated with developmental toxicity. Abnormal glucose metabolism disturbs energy balances that impair the early development of vertebrates, but the mechanisms by which maternal OPAH exposure alters glucose homeostasis in offspring are not well understood. Studies have suggested that epigenetic changes, particularly in DNA methylation, provide a memory of plastic developmental responses to the environment, leading to the generation of novel offspring phenotypes. The objective of this study is to test the hypothesis that embryonic exposure to low-dose OPAH can impair early β-cell differentiation in zebrafish (Danio rerio) by altering DNA methylation and gene expression. The zebrafish embryos were exposed to 0, 0.03, 0.1, 0.3, 1 and 3 μM 9‑fluorenone (9-FLO) at 3 h postfertilization (hpf) until 120 hpf to assess pancreatic organogenesis. 9-FLO exposure reduced total body length, eye length and heart rate, decreased insulin generation, interfered with glucose metabolism, and altered the expression of pancreatic organogenesis-related genes pdx-1, foxa2, isl1 and ptf1a. In particular, low-dose embryonic 9-FLO exposure significantly decreased β-cell differentiation marker gene pdx-1 mRNA levels, indicating that pancreatic endocrine is a more sensitive target response to embryonic low-dose OPAH exposure. Additionally, we found that DNA methyltransferases dnmt1 and dnmt3 were elevated and the DNA methylation at promoter regions of pdx-1 was increased at an early stage of development. These data demonstrated that the low-dose OPAH embryonic exposure can impair pancreatic endocrine development by increasing DNA methylation at the promoter regions of pdx-1 that are essential for β-cell differentiation.

Beyond the obvious: Environmental health implications of polar polycyclic aromatic hydrocarbons

The genotoxic, mutagenic and carcinogenic effects of polar polycyclic aromatic hydrocarbons (polar PAHs) are believed to surpass those of their parent PAHs; however, their environmental and human health implications have been largely unexplored. Oxygenated PAHs (oxy-PAHs) is a critical class of polar PAHs associated with carcinogenic effects without enzymatic activation. They also cause an upsurge in reactive oxygen species (ROS) in living cells. This results in oxidative stress and other consequences, such as abnormal gene expressions, altered protein activities, mutagenesis, and carcinogenesis. Similarly, some nitrated PAHs (N-PAHs) are probable human carcinogens as classified by the International Agency for Research on Cancer (IARC). Heterocyclic PAHs (polar PAHs containing nitrogen, sulphur and oxygen atoms within the aromatic rings) have been shown to be potent endocrine disruptors, primarily through their estrogenic activities. Despite the high toxicity and enhanced environmental mobility of many polar PAHs, they have attracted only a little attention in risk assessment of contaminated sites. This may lead to underestimation of potential risks, and remediation end points. In this review, the toxicity of polar PAHs and their associated mechanisms of action, including their role in mutagenic, carcinogenic, developmental and teratogenic effects are critically discussed. This review suggests that polar PAHs could have serious toxicological effects on human health and should be considered during risk assessment of PAH-contaminated sites. The implications of not doing so were argued and critical knowledge gaps and future research requirements discussed.

The combined effects of surfactant solubilization and chemical oxidation on the removal of polycyclic aromatic hydrocarbon from soil

A method for the remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated soils was proposed involving a combination of surfactant-aided soil washing and chemical oxidation by activated persulfate (SP). In this study, Triton X-100 (TX-100) and SP was applied to the soil, either concurrently or sequentially. Results indicated that surfactant followed by amendment with a solution of SP, TX-100 + SP(l), was most effective in decreasing PAHs concentrations in a sandy loam soil (SS) and a silty clay soil (NS) from 1220 mg/kg and 2730 mg·kg^-1 to 414 mg·kg^-1 and 180 mg·kg^-1, respectively. Compared with extraction alone and oxidation alone, TX-100 + SP(l) increased the removal of PAHs by 10-20%. TX-100 improved the degradation of 3-4 ring PAHs (M-PAHs) and 5-6 ring PAHs (H-PAHs) in SS, by approximately 8%-11%. The oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) including furans and xanthene exhibited greater reductions in soil when amended with the TX-100 and SP, than under TX-100 extraction or SP oxidation alone. Overall, increased removal of PAHs in contaminated soil can occur through simultaneous application of TX-100 and SP, relative to the sole use of TX-100 or SP. The sequential combination of surfactant and oxidant was most effective for the elimination of PAHs, especially for M-PAHs and H-PAHs in sandy loam contaminated soil.

Sources and fate of polycyclic aromatic compounds (PAHs, oxygenated PAHs and azaarenes) in forest soil profiles opposite of an aluminium plant

Little is known about oxygenated polycyclic aromatic hydrocarbons (OPAHs) and azaarenes (AZAs) in forest soils. We sampled all horizons of forest soils from five locations at increasing distances from an Al plant in Slovakia, and determined their polycyclic aromatic compound (PACs) concentrations. The ∑29PAHs concentrations were highest in the Oa and lowest in the Oi horizon, while the ∑14OPAHs and ∑4AZAs concentrations did not show a consistent vertical distribution among the organic horizons. The concentration ratios of PAHs and OPAHs between deeper O horizons and their overlying horizon (enrichment factors) were positively correlated with the octanol-water partition coefficients (K_OW) at several locations. This is attributed to the slower degradation of the more hydrophobic PACs during organic matter decomposition. PACs concentrations decreased from the organic layer to the mineral horizons. The concentrations of ∑29PAHs (2400-17,000 ng g^-1), ∑14OPAHs (430-2900 ng g^-1) and ∑4AZAs (27-280 ng g^-1) in the mineral A horizon generally decreased with increasing distance from the Al plant. In the A horizons, the concentrations of ∑29PAHs were correlated with those of ∑14OPAHs (r = 0.95, p = 0.02) and ∑4AZAs (r = 0.93, p = 0.02) suggesting that bioturbation was the main transport process of PACs from the organic layer into the mineral soil. At each location, the concentrations of PACs generally decreased with increasing depth of the mineral soil. Enrichment factors of PAHs in the mineral horizons were not correlated with K_OW, pointing at colloid-assisted transport and bioturbation. The enrichment factors of OPAHs (in mineral horizons) at a site were negatively correlated with their K_OW values indicating that these compounds were leached in dissolved form. Compared to a study 13 years before, the concentrations of PAHs had decreased in the O horizons but increased in the A and B horizons because of soil-internal redistribution after emissions had been reduced.

Occurrence and leachability of polycyclic aromatic compounds in contaminated soils: Chemical and bioanalytical characterization

An important concern regarding sites contaminated with polycyclic aromatic compounds (PACs) is the risk of groundwater contamination by release of the compounds from soils. The goal of this study was to investigate the occurrence and leachability of 77 PACs including polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic compounds (NSO-PACs) among total aryl hydrocarbon receptor (AhR) agonists in soils from historical contaminated sites. A novel approach combining chemical and bioanalytical methods in combination with characterization of leachability by use of a column leaching test was used. Similar profiles of relative concentrations of PACs were observed in all soils, with parent PAHs accounting for 71 to 90% of total concentrations in soils. Contribution of oxy-PAHs, alkyl-PAHs and N-PACs ranged from 2 to 9%, 3 to 9% and 1 to 14%, respectively. Although the contributions of groups of PACs were small, some compounds were found in similar or greater concentrations than parent PAHs. Leachable fractions of 77 PACs from soils were small and ranged from 0.002 to 0.54%. Polar PACs were shown to be more leachable than parent PAHs. The contribution of analyzed PACS to overall AhR-mediated activities in soils and leachates suggests presence of other AhR agonists in soils, and a potential risk. Only a small fraction of AhR agonists was available in soils, indicating an overestimation of the risk if only total initial concentrations in soils would be considered in risk assessment. The results of the study strongly support that focus on 16US EPA PAHs may result in inadequate assessment of risk and hazard of PACs in complex environmental samples.

A 150-year record of polycyclic aromatic compound (PAC) deposition from high Andean Cajas National Park, southern Ecuador

The temporal profiles of polycyclic aromatic compounds (PACs) in lake sediments reflect past changes in emissions, transport and deposition of these pollutants and, thus, record natural and anthropogenic processes. We document fluxes of PACs [(polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs (OPAHs) and azaarenes (AZAs)] deposited in two tropical high-altitude lakes in the Cajas National Park (Ecuadorian Andes, 2°50'S, 79°10'W). In remote and high elevation Laguna Fondococha (4130m a.s.l.), the temporal fluxes of OPAHs and AZAs were similar to those of PAHs suggesting similar sources. A significant increase of PAC deposition after the 1950s reflects Ecuador's economic development. PAH fluxes were relatively low (∑27PAHs (without retene and perylene): 0.86-11.21ngcm^-2yr^-1) with a composition pattern typical for long-range atmospheric transport (high 9-fluorenone/fluorene ratios) and biomass burning (30% low molecular weight PAHs). PAHs diagnostic of high temperature combustion (industry, traffic) make up 20-25% of total PAHs. Perylene concentrations increase linearly with increasing sediment depth suggesting diagenetic in-situ production. At lower elevations (Laguna Llaviucu, 3140m a.s.l.) and closer to urban areas, PAC fluxes in the past decades were 4-5 times higher than in the remote high-elevation lake. Laguna Llaviucu also showed higher concentrations of high molecular weight pyrogenic PAHs and a greater diversity of AZAs. Individual OPAHs and AZAs reflect mainly combustion activities. In Laguna Llaviucu, which is at a lower elevation (3140m a.s.l.) and closer to the city, molecular ratios suggest short-range atmospheric transport and deposition of PACs. A very foggy climate (170 rainy days per year) with the precipitation maximum at 3500m removes PACs very efficiently (by wet deposition) from the atmosphere at very short distances from emission sources. This partly explains why L. Llaviucu shows higher fluxes of PACs than the higher elevation L. Fondococha. This study presents the first historical record of organic pollutants from environmental archives in Ecuador.

Spatial distribution, emission source and health risk of parent PAHs and derivatives in surface soils from the Yangtze River Delta, eastern China

243 surface soil samples were collected from the Yangtze River Delta (YRD) region, and the concentration distributions and compositional profiles of 27 parent PAHs (PPAHs), nitro- and oxy-derivatives (NPAHs and OPAHs), respectively, and health risk of 16 PPAHs were determined. Atmospheric samples were collected at two sites with high topsoil concentrations of PAHs to assist in identifying the emission sources of PPAHs. The total concentrations of PPAHs, NPAHs and OPAHs fell in the ranges of 21.0-3563.2 ng/g, 0.4-4.6 ng/g and 2.1-834.1 ng/g, respectively. PPAHs in topsoil were dominated by low and medium molecular weight species. The main components of OPAHs were 9FO and ANQ. For NPAHs, only 1N-NAP was frequently detected. Overall, the northern parts of the YRD region were more heavily contaminated by PPAHs and their corresponding derivatives. The soil TOC fraction and GDP per capita were significantly correlated with the spatial distribution of PPAHs. Specific ratios of isomeric species and principal component analysis (PCA) designated combustion of industrial coal and biomass, and traffic exhaust as the main mixed emission sources of PPAHs in surface soils in this region. The detected NPAHs and OPAHs were significantly associated with the corresponding PPAHs. The estimated incremental lifetime cancer risk attributed to 16 PPAHs in surface soil was greater than 10^-6, indicating a potential risk of contracting cancer by exposure to topsoil from the YRD region. The cumulative probability of cancer risk for both adults and children via three exposure pathways followed the sequence of dermal contact > ingestion > inhalation.

Cancer risk from polycyclic aromatic compounds in fine particulate matter generated from household coal combustion in Xuanwei, China

Polycyclic aromatic hydrocarbons (PAHs) and their polar derivatives (oxygenated PAHs: OPAHs and azaarenes: AZAs) were characterized in fine particulates (PM_2.5) emitted from indoor coal combustion. Samples were collected in Xuanwei (Yunnan Province), a region in China with a high rate of lung cancer. A sample from the community with the highest mortality contained the highest total concentration of PAHs, OPAHs and AZAs and posed the highest excess cancer risk from a lifetime of inhaling fine particulates. Positive correlations between total carbonyl-OPAHs, total AZAs and total PAHs implied that the emissions were dependent on similar factors, regardless of sample location and type. The calculated cancer risk ranged from 5.23-10.7 × 10^-3, which is higher than the national average. The risk in each sample was ∼1-2 orders of magnitude higher than that deemed high risk, suggesting that the safety of these households is in jeopardy. The lack of potency equivalency factors for the PAH derivatives could possibly have underestimated the overall cancer risk.

Azaarenes in fine particulate matter from the atmosphere of a Chinese megacity

Azaarenes (AZAs) are toxicologically relevant organic compounds with physicochemical properties that are significantly different from the well-studied polycyclic aromatic hydrocarbons (PAHs). However, little is known about their concentrations, seasonal variations, fate, and relationship with PAHs in air. This paper reports the temporal variations in the concentrations and composition patterns of AZAs in PM2.5 that was sampled once per 6 days from outdoor air of Xi'an, China from July 2008 to August 2009. The concentrations of the ∑AZAs, quinoline (QUI), benzo[h]quinoline (BQI), and acridine (ACR) in PM2.5 were 213-6441, 185-520, 69-2483, and 10-3544 pg m(-3), respectively. These concentrations were higher than those measured in urban areas of Western Europe. AZA compositional patterns were dominated by BQI and ACR. The high concentration of AZAs, high AZA/related PAH ratio, and the dominance of three-ring AZAs (BQI and ACR) in PM2.5 of Xi'an are all in contrast to observations from Western European and North American cities. This contrast likely reflects differences in coal type and the more intense use of coal in China. The PM2.5-bound concentration of AZA in winter season (W) was higher than during the summer season (S) with W/S ratios of 5.7, 1.4, 4.1, and 13, for ∑AZAs, QUI, BQI, and ACR, respectively. Despite their significantly different physicochemical properties, AZAs were significantly (p < 0.05) positively correlated with their related PAHs and pyrogenic elemental carbon. The changes in AZA concentrations were positively correlated with ambient pressure but negatively correlated with ambient temperature, wind speed, and relative humidity. This trend is similar to that observed for the related PAHs. We conclude that Xi'an and possibly other Chinese cities have higher emission of AZAs into their atmosphere because of the more pronounced use of coal. We also conclude that in spite of differences in physicochemical properties between AZAs and related PAHs, the atmospheric dynamics and relationships with meteorological factors of both compound groups are similar.

Characterization of chemical components and bioreactivity of fine particulate matter (PM2.5) during incense burning

The chemical and bioreactivity properties of fine particulate matter (PM2.5) emitted during controlled burning of different brands of incense were characterized. Incenses marketed as being environmentally friendly emitted lower mass of PM2.5 particulates than did traditional incenses. However, the environmentally friendly incenses produced higher total concentrations of non-volatile polycyclic aromatic hydrocarbons (PAHs) and some oxygenated polycyclic aromatic hydrocarbons (OPAHs). Human alveolar epithelial A549 cells were exposed to the collected PM2.5, followed by determining oxidative stress and inflammation. There was moderate to strong positive correlation (R > 0.60, p < 0.05) between selected PAHs and OPAHs against oxidative-inflammatory responses. Strong positive correlation was observed between interleukin 6 (IL-6) and summation of total Group B2 PAHs/OPAHs (∑7PAHs/ΣOPAHs). The experimental data indicate that emissions from the environmentally friendly incenses contained higher concentrations of several PAH and OPAH compounds than did traditional incense. Moreover, these PAHs and OPAHs were strongly correlated with inflammatory responses. The findings suggest a need to revise existing regulation of such products.

Occurrence, distribution and health risk from polycyclic aromatic compounds (PAHs, oxygenated-PAHs and azaarenes) in street dust from a major West African Metropolis

Scientific evidence suggests that the burden of disease on urban residents of sub-Saharan African Countries is increasing, partly as a result of exposure to elevated concentrations of toxic environmental chemicals. However, characterization of the levels, composition pattern and sources of polycyclic aromatic compounds (PACs) in environmental samples from African cities is still lacking. This study measured the PAHs, oxygenated-PAHs (OPAHs) and azaarene (AZAs) content of street dusts collected from Kumasi, Ghana (a major metropolis located in the tropical forest zone of West Africa). The ∑Alkyl+parent-PAHs, ∑OPAHs and ∑AZAs concentration in street dust averaged 2570 ng g(-1) (range: 181-7600 ng g(-1)), 833 ng g(-1) (57-4200 ng g(-1)) and 73 ng g(-1) (3.3-240 ng g(-1)), respectively. The concentrations of ∑Alkyl+parent-PAHs were strongly correlated (n=25) with ∑OPAHs (r=0.96, p<0.01) and ∑AZAs (r=0.94, p<0.01). The ∑OPAHs concentrations were also strongly correlated with ∑AZAs (r=0.91, p<0.01). Concentrations of individual PAHs in these street dusts were enriched at between 12 and 836 compared to their average concentrations in background soils from same city, demonstrating the high influence of traffic emissions. Several individual OPAHs and AZAs had higher concentrations than their related and often monitored parent-PAHs. The estimated incremental lifetime cancer risks due to the parent-PAHs in street dusts was >10(-6) indicating high risk of contracting cancer from exposure to street dust from Kumasi. The contribution of OPAHs, AZAs, and alkyl-PAHs in street dust to cancer risk could not be quantified because of lack of toxicity equivalency factors for these compounds; however this could be significant because of their high concentration and known higher toxicity of some polar PACs and alkyl-PAHs than their related parent-PAHs.

Risk assessment of urban soils contamination: The particular case of polycyclic aromatic hydrocarbons

The assessment of soil quality and characterization of potential risks to the environment and human health can be a very difficult task due to the heterogeneity and complexity of the matrix, the poor understanding about the fate of contaminants in the soil matrix, scarcity of toxicological/ecotoxicological data and variability of guidelines. In urban soils these difficulties are enhanced by the patchy nature of urban areas and the presence of complex mixtures of organic and inorganic contaminants resulting from diffuse pollution caused by urban activities (e.g. traffic, industrial activity, and burning of carbon sources for heating). Yet, several tools are available which may help to assess the risks of soil contamination in a simpler, cost effective and reliable way. Within these tools, a tiered risk assessment (RA) approach, first based on a chemical screening in combination with geostatistical tools, may be very useful in urban areas. However, there is still much to improve and a long way to go in order to obtain a reliable RA, especially in the case of hydrophobic organic compounds such as polycyclic aromatic hydrocarbons (PAHs). This paper aims at proposing a RA framework to assess the environmental and human health risks of PAHs present in urban soils, based on existing models. In addition, a review on ecotoxicological, toxicological, and exposure assessment data was made, as well as of the existing soil quality guidelines for PAHs that can be used in the RA process.

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.

Reconstruction of atmospheric soot history in inland regions from lake sediments over the past 150 years

Historical reconstruction of atmospheric black carbon (BC, in the form of char and soot) is still constrained for inland areas. Here we determined and compared the past 150-yr records of BC and polycyclic aromatic compounds (PACs) in sediments from two representative lakes, Huguangyan (HGY) and Chaohu (CH), in eastern China. HGY only receives atmospheric deposition while CH is influenced by riverine input. BC, char, and soot have similar vertical concentration profiles as PACs in both lakes. Abrupt increases in concentrations and mass accumulation rates (MARs) of soot have mainly occurred since ~1950, the establishment of the People’s Republic of China, when energy usage changed to more fossil fuel contributions reflected by the variations in the concentration ratios of char/soot and individual PACs. In HGY, soot MARs increased by ~7.7 times in the period 1980–2012 relative to the period 1850–1950. Similar increases (~6.7 times) were observed in CH. The increase in soot MARs is also in line with the emission inventory records in the literature and the fact that the submicrometer-sized soot particles can be dispersed regionally. The study provides an alternative method to reconstruct the atmospheric soot history in populated inland areas.

Characterizing the parent and oxygenated polycyclic aromatic hydrocarbons in mangrove sediments of Hong Kong

Parent and oxygenated polycyclic aromatic hydrocarbons (PAHs) were investigated in mangrove sediments of Hong Kong. Most of the analytes were detected, and the dominant carbonylic and hydroxylated PAHs in mangrove sediments were 9-fluorenone and 2-hydroxy fluorene, respectively. The concentration of 9-fluorenone and 9,10-anthraquinone was higher than their parent PAHs. Moreover, the concentration of total organic matter (TOM) related with those of the parent PAHs and carbonylic PAHs, except for hydroxylated PAHs, which indicated that TOM was not the only factor regulating the distribution of oxygenated PAHs. Nevertheless, the parent PAHs in mangrove sediments was correlated positively with carbonylic PAHs which demostrated not only the similar source but also the fate of these two compound class. However, hydroxylated PAHs had different source by comparing with parent PAHs and carbonylic PAHs, they were probably originated from biodegradation and accumulated in mangrove sediments.

Polycyclic aromatic hydrocarbons (PAHs) and their derivatives (alkyl-PAHs, oxygenated-PAHs, nitrated-PAHs and azaarenes) in urban road dusts from Xi'an, Central China

Urban road dusts are carriers of polycyclic aromatic compounds (PACs) and are therefore considered to be a major source of contamination of other environmental compartments and a source of exposure to PACs for urban populations. We determined the occurrence, composition pattern and sources of several PACs (29 alkyl- and parent-PAHs, 15 oxygenated-PAHs (OPAHs), 4 azaarenes (AZAs), and 11 nitrated-PAHs (NPAHs)) in twenty urban road dusts and six suburban surface soils (0-5cm) from Xi'an, central China. The average concentrations of ∑29PAHs, ∑4AZAs, ∑15OPAHs, and ∑11NPAHs were 15767, 673, 4754, and 885 n gg(-1) in road dusts and 2067, 784, 854, and 118 ng g(-1) in surface soils, respectively. The concentrations of most individual PACs were higher in street dusts than suburban soils, particularly for PACs with molecular weight>192 g mol(-1). The enrichment factors of individual PACs were significantly positively correlated with log KOA and log KOW, indicating an increasing deposition and co-sorption of the PACs in urban dusts with decreasing volatility and increasing hydrophobicity. Significant correlations between the concentrations of individual and sum of PACs, carbon fractions (soot and char), and source-characteristic PACs (combustion-derived PAHs and retene, etc.), indicated that PAHs, OPAHs and AZAs were mostly directly emitted from combustion activities and had similar post-emission fates, but NPAHs were possibly more intensely photolyzed after deposition as well as being emitted from vehicle exhaust sources. The incremental lifetime cancer risk (ILCR) resulting from exposure to urban dust bound-PACs was higher than 10(-6), indicating a non-negligible cancer risk to residents of Xi'an.

Metabolomic analysis to define and compare the effects of PAHs and oxygenated PAHs in developing zebrafish

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives are ubiquitously present in diesel exhaust, atmospheric particulate matter and soils sampled in urban areas. Therefore, inhalation or non-dietary ingestion of both PAHs and oxy-PAHs are major routes of exposure for people; especially young children living in these localities. While there has been extensive research on the parent PAHs, limited studies exist on the biological effects of oxy-PAHs which have been shown to be more soluble and more mobile in the environment. Additionally, investigations comparing the metabolic responses resulting from parent PAHs and oxy-PAHs exposures have not been reported. To address these current gaps, an untargeted metabolomics approach was conducted to examine the in vivo metabolomic profiles of developing zebrafish (Danio rerio) exposed to 4 µM of benz[a]anthracene (BAA) or benz[a]anthracene-7,12-dione (BAQ). By integrating multivariate, univariate and pathway analyses, a total of 63 metabolites were significantly altered after 5 days of exposure. The marked perturbations revealed that both BAA and BAQ affect protein biosynthesis, mitochondrial function, neural development, vascular development and cardiac function. Our previous transcriptomic and genomic data were incorporated in this metabolomics study to provide a more comprehensive view of the relationship between PAH and oxy-PAH exposures on vertebrate development.

Elemental carbon and polycyclic aromatic compounds in a 150-year sediment core from Lake Qinghai, Tibetan Plateau, China: influence of regional and local sources and transport pathways

Elemental carbon (EC) and polycyclic aromatic compounds (PACs) are potential proxies for the reconstruction of change in human activities and the origin of air masses in historic times. In this study, the historic deposition of char and soot (the two subtypes of EC) and PACs in a 150-year sediment core from different topographic subbasins of Lake Qinghai on the Qinghai Tibetan Plateau (QTP) were reconstructed. The objective was to explore how the variations in the concentrations of EC and PACs, in the ratios of char to soot and of oxygenated polycyclic aromatic hydrocarbons (OPAHs) to parent PAHs, and in the composition of the PAC mixtures reflect historical changes in climate and human activity and the origin of air masses arriving at the QTP. The deposition fluxes of soot in the different subbasins were similar, averaging 0.18 (range of 0.15-0.25) and 0.16 (0.13-0.23) g m(-2) year(-1), respectively, but they varied for char (averaging 0.11 and 0.22 g m(-2) year(-1), respectively), suggesting ubiquitous atmospheric deposition of soot and local river inputs of char. The different vertical distributions of the char/soot ratios in the different subbasins can be interpreted in terms of the different transport mechanisms of char and soot. An abrupt increase in soot concentrations since 1980 coincides with results from the QTP ice cores that were interpreted to be indicative of soot transport from South Asia. Similar concentration patterns of PAHs with soot and 9,10-anthraquinone/anthracene (9,10-AQ/ANT) ratios all >2.0 suggest regional PAC sources. Increasing PAH/soot ratios and decreasing 9,10-AQ/ANT ratios since the beginning of the 1970s indicate increasing local emissions. The historical trends of these diagnostic ratios indicate an increase in the fossil-fuel contribution since the beginning of the 1970s. The increase of perylene concentrations with increasing core depth and the ratio of perylene to its penta-aromatic isomers indicate that perylene originates mainly from in situ biogenic diagenesis. We demonstrate that the concentrations of EC, char, soot, and PACs in sediments can be used to reconstruct local, regional, and remote sources and transport pathways of pollutants to the QTP.