EPA Priority Polycyclic Aromatic Hydrocarbons Research Articles

Characteristics of typical intermediate and semi volatile organic compounds in Shanghai during China International Import Expo event

To ensure good air quality during the China International Import Expo (CIIE) event, stringent emission-reduction measures were implemented in Shanghai. To assess the efficacy of these measures, this study measured typical categories of intermediate/semi volatile organic compounds (I/SVOCs), including alkanes (C10–C26 n-alkanes and pristane), EPA-priority polycyclic aromatic hydrocarbons (PAHs), alkylnaphthalenes, benzothiazole (BTH) and chlorobenzenes (CBs), at an urban site of Shanghai before and during two CIIE events (2019 and 2020; non-CIIE versus CIIE). The average concentrations of alkanes and PAHs during both 2019 and 2020 CIIE events decreased by approximately 41% and 17%, respectively, compared to non-CIIE periods. However, the decline in BTH and CBs was only observed during CIIE-2019. Secondary organic aerosol (SOA) formation from alkanes, PAHs and BTH was evaluated under atmospheric conditions, revealing considerable SOA contributions from dimethylnaphthalenes and BTH. Positive matrix factorization (PMF) analysis further revealed that life-related sources, such as cooking and residential emissions, make a noticeable contribution (21.6%) in addition to the commonly concerned gasoline-vehicle sources (31.5%), diesel-related emissions (20.8%), industrial emissions (18.6%) and ship emissions (7.5%). These findings provide valuable insights into the efficacy of the implemented measures in reducing atmospheric I/SVOCs levels. Moreover, our results highlight the significance of exploring additional individual species of I/SVOCs and life-related sources for further research and policy development.

Evaluation of Appropriate Conditions for Efficient Simultaneous Determination of US EPA and EU Priority Polycyclic Aromatic Hydrocarbons in Various Food Categories and Assessment of Their Consumption Risk.

The QuEChERS (quick, easy, cheap, effective, rugged and safe) conditions were optimized for efficient determination of the U.S. Environmental Protection Agency (US EPA) and European Union (EU) priority polycyclic aromatic hydrocarbons (PAHs) for the categories of grains, tuber & starchy vegetables, soy beans and products, fish & seafood, and poultry & meat, including raw materials and their corresponding products. The PAHs were analyzed using ultrahigh-performance liquid chromatography with temperature-controlled fluorescence detection and gas chromatography with tandem mass spectrometry. The established conditions had good accuracy, repeatability, and precision. Environmental pollution and processing methods influence the level of PAHs in samples. The low molecular weight PAHs were present in all raw materials, and processing increased high and low molecular weight PAHs in the products. The excess cancer risk for consumption of PAHs in cooked samples was mostly acceptable; a small number of samples might be of slight concern in certain age groups.

Characterization of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particles (PM2.5) in the North China Plain using positive-ion atmospheric pressure photoionization (APPI) coupled with fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)

Many aromatic compounds, including 16 types of U.S. EPA priority PAHs, exist in substituted or unsubstituted forms and have high toxicities. Aromatic compounds in aerosols collected in the North China Plain (NCP) were characterized by GC-MS and atmospheric pressure photoionization (APPI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). The concentrations of the 16 types of PAHs in the collected samples ranged from 277.0 to 876.8 ng/m3, which were higher than those collected in other regions and countries. Previous studies reported that only 27 wt% of aromatic compounds could be eluted using the GC system and demonstrated that APPI FT-ICR MS is a useful method for identifying large-molecular aromatics. In this study, two samples collected from the NCP were successfully characterized by APPI FT-ICR MS. In the APPI + mode, 231 and 228 CH formulas (containing only C and H and having a double bond equivalent (DBE) of 4 or greater) were identified, accounting for 10% of the numerical fraction and more than 40% of the intensity fraction. The FT-ICR data revealed that condensed PAHs with 6–8 aromatic rings had relatively high abundances and that a series of PAH homologs (alkylated PAHs) with identical DBE values ranging from 4 to 30 were present. Furthermore, heteroatom groups were also identified as significant components of the aromatic fractions. The O1, O2, N1, NO2, and S1 class species with DBE values of 3–34 and carbon numbers of 11–42 were identified by APPI FT-ICR MS. The heteroatom PAHs had DBE values and carbon number distributions similar to regular PAHs. The aromatic fractions determined in this work provide useful data for future quantitative analyses of aromatic compounds with high toxicities and our findings will help improve the current understanding of PAH compositions in the northern China. However, further research is needed to determine the abundances and toxicities of various apparent or substituted PAHs outside of the 16 types identified by the U.S. EPA as priority PAH compounds, which have been extensively researched.

Quantification of Gaseous and Particulate Emission Factors from a Cargo Ship on the Huangpu River

Exhaust emissions from ships have garnered significant attention because of their impact on global climate change, deterioration of air quality, and potential risks to human health. Consequently, it is necessary and urgent to quantify the gaseous and particulate emission factors (EFs) of ships in a local area. In order to supplement native EF profile data, an inland cargo ship in China was selected for measuring gaseous and particle pollutants under real-world operation modes. The fuel-based EFs of carbon dioxide, carbon monoxide (CO), nitrogen oxides, and hydrocarbons (THC) were 2965–3144 g/kg, 8.04–83.53 g/kg, 64.51–126.20 g/kg, and 3.90–23.35 g/kg, respectively. The maximum values of CO EF and THC EF were achieved under idling mode, which were 10.4 and 5.3 times those observed under cruising (500 rpm) mode, as extremely poor engine loads under idling mode can result in low temperature, low pressure, and uneven mixture of air and fuel. Organic carbon and element carbon were identified as the most abundant compositions of particulate matter (PM). Ions and elements were primarily dominated by SO42− and S, which can be attributed to the utilization of fuels with high sulfur content. Additionally, hopanes (dominated by 17α(H),21β(H)-Hopane and 17α(H),21β(H)-29-Norhopane) and fatty acids (dominated by n-Hexadecanoic acid and n-Octadecanoic acid) have the potential to serve as tracers for ship exhaust emissions. Pyrene and fluoranthene, two EPA priority polycyclic aromatic hydrocarbons (PAHs), were identified as the major constituents of PAHs and accounted for 50% of total PAHs. This finding also provides an explanation for the significant contribution of four-ring PAHs to the total PAHs mass.

Physicochemical and Polycyclic Aromatic Hydrocarbons (PAHs) Analysis in Soil and Sediment from Vicinity of Ikot Akpaden, Akwa Ibom State, Nigeria

The study was undertaken to determine the levels of 16 priority PAHs in soil and sediments from some vicinities of Ikot Akpaden, Mkpat Enin. The soils were prepared using standard procedure in the laboratory and analyzed for 16 US EPA priority PAHs using Gas Chromatography-Mass Spectrophotometer (GC-MS). The soil samples were obtained from two sampling sites at Ikot Akpaden (Site A and C). Site C showed minimal PAHs concentration while site A recorded PAHs levels ranging from 0.01 to 4.25 mg/kg. According to European commission, the PAHs concentrations in soil samples of this study are moderate, but deleterious over time. The soils were negatively affected more with low molecular weight PAHs than High Molecular Weight PAHs.This study revealed that the sampling sites had low carcinogenic burden, hence would exhibit moderate adverse health effects to plants and animals. It was concluded that automobile repair activities in site A contributed to the soil contamination with PAHs; hence it should be properly sited.

Emerging polycyclic aromatic hydrocarbon (PAH) and trace metal leachability from reclaimed asphalt pavement (RAP)

The environmental risks associated with the storage, reuse, and disposal of unencapsulated reclaimed asphalt pavement (RAP) has been previously examined, but because of a lack of standardized column testing protocols and recent interest on emerging constituents with higher toxicity, questions surrounding leaching risks from RAP continue. To address these concerns, RAP from six, discrete stockpiles in Florida was collected and leach tested following the most up-to-date, standard column leaching protocol – United States Environmental Protection Agency (US EPA) Leaching Environmental Assessment Framework (LEAF) Method 1314. Sixteen EPA priority polycyclic aromatic hydrocarbons (PAHs), 23 emerging PAHs, identified through relevance in literature, and heavy metals were investigated. Column testing showed minimal leaching of PAHs; only eight compounds, three priority PAHs and five emerging PAHs, were released at quantifiable concentrations, and where applicable, were below US EPA Regional Screening Levels (RSL). Though emerging PAHs were identified more frequently, in most cases, priority compounds dominated contributions to overall PAH concentration and benzo(a)pyrene (BaP) equivalent toxicity. Except for arsenic, molybdenum, and vanadium in two samples, metals were found below limits of detection (LOD) or below risk thresholds. Arsenic and molybdenum concentrations diminished over time with increased exposure to liquid, but elevated vanadium concentrations persisted in one sample. Further batch testing linked vanadium to the aggregate component of the sample, unlikely to be encountered in typical RAP sources. As demonstrated by generally low constituent mobility observed during testing, the leaching risks associated with the beneficial reuse of RAP are limited, and under typical reuse conditions, factors of dilution and attenuation would likely reduce leached concentrations below relevant risk-based thresholds at a point of compliance. When considering emerging PAHs with higher toxicities, analyses indicated minimal impact to overall leachate toxicity, further suggesting that with proper management, this heavily recycled waste stream is unlikely to pose leaching risk.

Characterization, risk assessment, and source estimation of PM10-bound polycyclic aromatic hydrocarbons during wintertime in the ambient air of Basrah City, Iraq

In this study, the concentration and structure of polycyclic aromatic hydrocarbons (PAHs) associated with the ambient PM10 in Basrah City, Iraq have been investigated for the first time. From December 2021 to February 2022, PM10 samples were collected on quartz fiber filters, extracted using an optimized extraction protocol, and analyzed for the sixteen US EPA priority PAHs. The results indicated that 4- and 5-ring PAHs represent 52% of the total detected PAHs. The most abundant PAHs over the study period were chrysene (1.2 ± 1.5 ng m−3), fluorene (0.9 ± 1.4 ng m−3), and benzo[b]fluoranthene (0.7 ± 0.9 ng m−3). Source identification suggested that PM10-bound PAHs primarily originated from pyrogenic and petrogenic activities in Basrah City. In addition, the cancer risk associated to PAH exposure was assessed based on benzo[a]pyrene equivalent concentration and was found ranging from 0.07 to 6.32 ng m-3; hence, it exceeded the threshold limit of 1.0 ng m−3 established by the European legislation (EU, 2014). Benzo[a]pyrene was determined to be main contributor to total carcinogenic power of the detected PAHs, accounting for 50.3%, followed by dibenz[a,h]anthracene (22.3%). Similarly, benzo[a]pyrene represented a major contributor to PAH associated mutagenicity, accounting for 43.5% of the total.

In situ investigation of N deposit effects on polycyclic aromatic hydrocarbons (PAHs) photolysis in snow

As snow is an ideal scavenger of polycyclic aromatic hydrocarbons (PAHs) for both particulate- and gas-phase PAHs, a large amount of PAHs are accumulated in snowpacks. These PAHs could be released from seasonal snowpacks into environment over a short time during the snow melting period, causing a flush of contaminants. Understanding the fate of PAHs in snow therefore is important to evaluate the contaminant flush during snow melting. However, as an important natural process, PAH photolysis in snow is still unclear, especially in the context of global climate change. Therefore, photolysis of the 16 PAHs, which are listed as priority controlled pollutants by United States Environmental Protection Agency (US EPA), was investigated with N deposit in field in snow in this study. A mixture of the 16 US EPA priority PAHs and nitrate/ammonia were spiked into sealed quartzose bottles containing snow samples in field. The bottles were then exposed to solar radiation in field for 6 h. Experimental results showed that >50% of PAHs were lost during 6 h photolysis, mostly occurred in the first hour. Generally, HMW PAHs were photolyzed faster than LMW PAHs, though the photolysis rate did not strictly increase with molecular weight. Low concentrations of nitrate can enhance photolysis of Ant and Pyr, while photolysis of investigated PAHs was inhibited with nitrate concentration increasing. In contrast, both low and high concentration of ammonium can inhibit PAH photolysis. The inhibiting effect of both nitrate and ammonia on photolysis of HMW PAH is stronger than that of LMW PAHs, indicating direct photolysis of PAHs is the main pathway of PAH degradation in snow in situ. This study firstly showed the effect of N deposition on PAH photolysis in snow. Under current increasing N deposition in northeast China, this study implied that more PAHs in snow could be preserved during winter and released shortly during snowmelt, resulting in high ecological risk in spring.

Determination of Polycyclic Aromatic Hydrocarbons (PAHs) in Leaf and Bark Samples of Sambucus nigra Using High-Performance Liquid Chromatography (HPLC)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic compounds coming from natural or anthropogenic activities. Tree organs such as leaves and barks have been used to monitor urban air quality and have achieved remarkable ecological importance. However, the potential of many tree species as biomonitors is still unknown and efforts should be focused on conducting studies that analyze their capabilities with a viable analytical method. In this work, an analytical method for quantification of the 16 EPA priority PAHs from the leaves and bark of Sambucus nigra was validated. In general, the method showed good linearity, detection limits, precision, and recoveries, demonstrating that it is suitable for analyzing PAHs in both the leaves and bark of the Sambucus nigra species for which no analytical method for PAHs is yet available. The high prevalence of fluoranthene in the samples, which is a PAH related to coal combustion and biomass burning, and benzo[a]pyrene, which has a carcinogenic effect, was identified.

Emission factors for polycyclic aromatic hydrocarbons from laboratory biomass-burning and their chemical transformations during aging in an oxidation flow reactor

Atmospheric polycyclic aromatic hydrocarbons (PAHs) can be emitted from different combustion sources including domestic biomass burning, internal combustion engines, and biomass burning (BB) in wild, prescribed, and agricultural fires. With climate warming and consequent global increases in frequency and severity of wildfires, BB is a dominant source of PAHs emitted into the atmosphere.In this study, six globally and regionally important and representative fuels (Alaskan peat, Moscow peat, Pskov peat, eucalyptus, Malaysian peat, and Malaysian agricultural peat) were burned under controlled conditions in the combustion chamber facility at the Desert Research Institute (DRI, Reno, NV, USA). Gas- and particle-phase BB emissions were aged in an oxidation flow reactor (OFR) to mimic five to sevendays of atmospheric aging. To sample gas- and particle-phase BB emissions, fresh and OFR-aged biomass-burning aerosols were collected on Teflon-impregnated glass fiber filters (TIGF) in tandem with XAD resin media for organic carbon speciation. The objectives of this study were to i) quantify the emission factors for 113 PAHs emitted from the combustion of the six selected fuels, ii) characterize the distribution of PAH compounds between gas and particle phases for these fuels, iii) identify the changes in PAHs during OFR-aging, and iv) evaluate toxicity potential with characterized compounds.We found that combustion emissions of gas-phase PAHs were more abundant (>80 % by mass) than particle-phase PAHs, for emissions from all combusted fuels. The mass fraction of substituted napthalenes in Moscow peat and Malaysian peat emissions were ∼70 % & 84 %, respectively, whereas in Eucalyptus the same fraction was <50 %, which indicates that these substituted compounds can be used as tracers for peat emissions. Mass concentrations of gas- and particle-phase PAHs were reduced by ∼70 % after OFR oxidation. However, the understanding of the fate of PAHs during OFR oxidation requires further investigations. Our results also indicate that the PAH toxicity of BB samples would be underestimated by 10–100 times if only the BaPeq for the 16 US EPA priority PAHs in the particle phase are included.

The recalcitrance and potential toxicity of polycyclic aromatic hydrocarbons within crude oil residues in beach sediments at the BIOS site, nearly forty years later

The Arctic is a unique environment characterized by extreme conditions, including daylight patterns, sea ice cover, and some of the lowest temperatures on Earth. Such characteristics in tandem present challenges when extrapolating information from oil spill research within warmer, more temperate regions. Consequently, oil spill studies must be conducted within the Arctic to yield accurate and reliable results. Sites of the Baffin Island Oil Spill (BIOS) project (Cape Hatt, Baffin Island, Canadian Arctic) were revisited nearly 40 years after the original oil application to provide long-term monitoring data for Arctic oil spill research. Surface and subsurface sediment samples were collected from the intertidal zone of the 1981 nearshore oil spill experiment (Bay 11), from 1980 supratidal control plots (Crude Oil Point) and 1982 supratidal treatment plots (Bay 106). Samples were analyzed for Polycyclic Aromatic Hydrocarbons (PAHs) and alkylated homologues via Gas Chromatography – Mass Spectrometry (GC-MS). Our results suggest that total mean concentrations of all measured PAHs range from 0.049 to 14 mg/kg, whereas total mean concentrations of the 16 US EPA priority PAHs range from 0.02 to 2.1 mg/kg. The relative proportions of individual PAHs were compared between sampling sites and with the original technical mixture. Where available, percent loss of individual PAHs was compared with data from samples collected at the BIOS site, in 2001. All three sites featured samples where concentrations of various priority PAHs exceeded the established Interim Marine Sediment Quality Guidelines. All supratidal samples contained potentially toxic levels of PAHs. Even after nearly four decades of weathering, the recalcitrant crude oil residues remain a potential hazard for the native organisms. Continued monitoring of this unique study site is crucial for establishing a timeline for oil degradation, and to observe a reduction in toxicity over time.

A Long-Term Study on the Content of Polycyclic Aromatic Hydrocarbons in Rubber from End-of-Life Tires of Passenger Cars and Trucks.

At the European level, limits have been set (REACH) for the content of polycyclic aromatic hydrocarbons (PAH) in products with rubber and plastic components that come into contact with human skin or the oral cavity. These limit values reported in Commission Regulation (EU) 1272/2013 are of particular importance for the utilization of end-of-life tires (ELT) as recycled rubber materials for consumer applications, but a suitable analytical method has not yet been specified. On the other hand, comprehensive measurement series of the PAH content of ELT materials are scarce in the context of compliance testing against this regulation and general published PAH levels in ELT materials are often based on very different analytical methods. In the present work, the PAH content of three different rubber granulates from ELT (obtained from whole truck and passenger car tires and truck tire treads) were investigated over a period of two years. The Grimmer method was used for PAH profile analysis, which in terms of extraction intensity and sample preparation not only meets the requirements for a reliable determination of the EU priority PAH, but in addition covers a more comprehensive PAH profile. A total of 26 different PAH compounds, including the 8 EU priority PAH (REACH) and the 16 U.S. EPA priority PAH, were analyzed and their variations over time were examined to obtain reliable current data for PAH content in rubber granulates produced from ELT.

Polycyclic aromatic hydrocarbons in diverse agricultural soils of central India: occurrence, sources, and potential risks

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds found ubiquitously in the environment and pose serious threat to the environment and humans. PAHs have received considerable attention due to their carcinogenic properties. In this study, the 16 EPA priority PAHs were determined in agricultural surface soils (0–5 cm) from diverse agricultural land use systems in central India. ∑16 PAHs of different agricultural soil samples ranged from ND–122.52 µg/kg. Total concentration of 7 carcinogenic PAHs ranged between ND and 101.64 µg/kg. The levels of PAHs in different agricultural soil samples varied widely. In general, we observed that ∑16 PAHs concentrations in agricultural soils have followed the order: sewage irrigated soil ≥ fly ash treated agricultural soil samples > horticulture land use soil > conservation agriculture soil > organic farming soil. PAH levels in fly ash-treated soils were 2–5 times higher than that in sewage-irrigated soils. PAHs containing four to five rings were the most common. Soil organic carbon (SOC) was positively correlated with ∑16 PAHs (p < 0.05). The principal sources of PAHs in these samples according to diagnostic ratios were biomass burning (grass, wood, crop residue) and coal combustion. In addition, it was found that agricultural soils treated with fly ash and sewage irrigated soils showed higher carcinogenic potential based on B[a]Peq TEQs. PAHs with higher carcinogenic potency in these contaminated soils indicate a higher level of health risk for humans.

Real-world characterization of carbonaceous substances from industrial stationary and process source emissions

Carbonaceous substances in industrial emissions are harmful to human health, air quality, and climate change. Owing to the existence of various fuel types and different technological processes, the characterization of carbonaceous substances from industrial emissions varies significantly, which causes a large uncertainty in source apportionment. Therefore, nine typical industrial sources were selected and separated into two types: stationary combustion and industrial process sources. The emission factors based on different units and profiles of carbonaceous substances, including organic carbon (OC), elemental carbon (EC), subgroups of OC and EC, EPA priority polycyclic aromatic hydrocarbons (PPAHs), methyl PAHs (MPAHs), and n-alkanes emitted from nine industrial sources were obtained. The results showed that the difference in dust removal efficiency or emission of other auxiliary materials in the industrial process could cause different emission factors for carbonaceous substances. Furthermore, the emission factors of fine particulate matter (PM2.5), OC, and EC for coal-fired plant were significantly lower than those of residential coal combustion. For profiles of carbonaceous substances in different industrial sources, the relative fractions of OC subgroups emitted from stationary combustion sources were lower than those from industrial process sources, whereas the proportions of EC were higher. The source profiles of nonpolar organic matter emitted from industrial process sources were clearly different from those of industrial stationary source emissions. For the four industrial process sources, the proportion of n-alkanes was significantly higher than that of PAHs, whereas the source profiles for different industrial stationary sources were extremely different. Finally, the concentrations of carbonaceous substances obtained in this study were lower than those reported in previous studies, indicating that marked reduction results were achieved by implementing reduction measures.

Characterization of carbonaceous substances emitted from residential solid fuel combustion using real-world data from the Beijing-Tianjin-Hebei region.

Residential solid fuel emissions are among the most important sources of carbonaceous substances that exert harmful effects on air quality, human health and climate change. Considering the constantly updated emission reduction policies for residential solid fuel combustion in the Beijing-Tianjin-Hebei (BTH) region, the emission data for the source should updated in a timely manner. Testing was performed on residential solid fuel emissions in the BTH region, China. The emission factors and profiles of carbonaceous substances (including organic carbon (OC), elemental carbon (EC), EPA priority polycyclic aromatic hydrocarbons (EPAHs), methyl PAHs (MPAHs), and n-alkanes) emitted from residential solid fuels were obtained. The results showed the ranges of emission factors of PM2.5, OC, EC, EPAHs, MPAHs and n-alkanes from residential solid fuel emissions were 1.92-17.6, 0.312-6.85, 0.066-2.33, 0.004-0.58, 0.003-0.87 and 0.009-0.39 g/kg fuel, respectively. The carbon fraction profiles showed that OC1, OC2, and EC1 were the major products of residential solid fuel combustion, and the non-polar organic matter profiles showed that Fluo and MFluo were dominant. The effects of combustion modes, types of stove and types of the fuel on emission characteristics of carbonaceous substances were discussed in detail. The emission factors of carbonaceous substances from the smoldering phase and traditional stove were higher than those from the flaming phase and improved stove, respectively, which was mainly controlled by the modified combustion efficiency (MCE). It was found that the emission factors of pollutants with decreasing MCE values sharply increased, especially when the MCE values were below 90%. Finally, some diagnostic ratios were discussed, and it was determined that residential coal combustion is considered to occur at MPAHs/PAHs higher than 1.5 and MFluo/Fluo higher than 5.

Study on the variations of extractable polycyclic aromatic hydrocarbons in lignite and semi-coke

Low-temperature pyrolysis is one of the most important technologies for the clean and efficient utilization of lignite. Semi-coke, the solid product of this process, has been widely used as both an industrial and household clean fuel. In this study, three lignites from China (EE), Indonesia (YN), and Mongolia (WM) and their semi-cokes obtained through pyrolysis at 550 °C were treated with dichloromethane, and the extracted polycyclic aromatic hydrocarbons (PAHs) were analyzed using a gas chromatograph/mass spectrometer. The results showed that the total concentrations of PAHs in EE, YN, and WM were 125000, 4400, and 5800 ng/g, respectively, and those in their semi-cokes were 4700, 10000, and 5500 ng/g, respectively. The concentrations of alkylated PAHs (aPAHs) were higher than those of parent 16 US EPA priority PAHs (16 PAHs) in lignites, while parent 16 PAHs were more abundant in semi-cokes. Both lignites and semi-cokes were dominated by 2-ring PAHs (naphthalene and alkylated naphthalenes), followed by 3- and 4-ring PAHs. The proportion of 2-ring PAHs in the semi-cokes increased with respect to that in the lignites, and the degree of alkylation of the PAHs decreased. This suggested that the extractable PAHs changed to smaller parent PAHs during the low-temperature pyrolysis. The concentration and composition of PAHs in the mobile phase of the semi-coke are an important part of its structural characteristics and are closely related to the macromolecular structure of raw coal. Thus, this study on PAHs in semi-coke provides relevant information on the structural evolution of coal during pyrolysis and further improves our understanding of clean fuel.

Combining eDNA and morphological approaches to reveal the impacts of long-term discharges of shale gas wastewaters on receiving waters

The potential threats of shale gas wastewater discharges to receiving waters is of great concern. In this study, chemical analyses and biomonitoring were performed three times in a small river that received treated wastewater over a two-year period. The results of chemical analyses showed that the concentrations of chloride, conductivity, barium, and strontium increased at the discharge site, but their concentrations decreased considerably farther downstream (≥500 m). The concentrations of toxic organic compounds (16 US EPA priority polycyclic aromatic hydrocarbons and 6 priority phthalates), trace metals (strontium, arsenic, zinc, copper, chromium, lead, cadmium, nickel, and neodymium), and natural radionuclides (40K, 238U, 226Ra, and 232Th) were comparable to the corresponding background values or did not exhibit obvious accumulation in sediments with continued discharge. Morphological and environmental DNA approaches were used to reveal the potential effects of wastewater discharges on aquatic ecosystems. The results showed that the community structure of benthic invertebrates was not altered by the long-term discharges of shale gas wastewaters. However, the biodiversity indices (richness and Shannon) from the two approaches showed inconsistencies, which were caused by multiple reasons, and that substrates had a strong influence on the morphological biodiversity indices. A multimetric index was proposed to further analyze morphological and environmental DNA data, and the results showed no significant difference between the upstream and downstream sites. Generally, the chemical and biological results both demonstrated that the discharges of shale gas wastewaters had limited impacts on river ecosystems within two years.

Polycyclic aromatic hydrocarbons (PAHs) in surface soils of tropical reef islands in China under external plant and soil introduction: Occurrence, sources, risks, and relationships with soil properties, vegetation cover, and soil source

This study explored the levels, sources, and risks of PAHs in soils from Yongle Atoll (YLA) and Xuande Atoll (XDA) of the Xisha Islands (XSIs) in the South China Sea, China, under different vegetation cover types and soil sources. The results clearly showed that the levels of 16 US EPA priority PAHs (Σ16PAHs) are relatively low in XDA and YLA, with concentrations ranging from not detected (ND) to 151 ng/g (average 15.7 ng/g) and ND to 5.8 ng/g (average 2.1 ng/g), respectively. Three- and four-ring PAHs (62.3% and 53.8%) were widely distributed in YLA and XDA. The average concentration of Σ16PAHs in soils with shrub cover was 1.4, 1.8, 4.8, and 5.0 times higher than that in soils with herbaceous cover, vegetable cover, arbor cover, and no plant cover, respectively. Source analysis using binary diagnostic ratios and the positive matrix factorization (PMF) model suggested that PAHs have similar sources (gasoline/coal combustion, coke production, and biomass combustion), but different contributions in native soil and introduced soil. Moreover, diesel-related vehicular emission was identified to be an additional source of PAHs in native soil. Pearson's correlations revealed strong relationships between PAHs and organic matter or total organic carbon. The cancer risk of PAHs varied among different vegetation cover types and soil sources, following the orders herbaceous cover > vegetable cover > shrub cover > arbor cover > no plant cover and introduced soil > mixed soil > native soil. Nevertheless, the risk remained lower than the risk threshold (10−6), suggesting low carcinogenesis risk in the two atolls. Our findings provide new evidence for the introduction of external vegetation/soil acting as a driver of changes in the characteristics of PAHs in islands, and also underline the negligibility of the PAH increase in soils in the South China Sea, China, from the perspective of health hazards.

New insight into human health risk from polycyclic aromatic hydrocarbons on surfaces of buildings and facilities for industrial legacy regeneration

Although many industrial heritage sites have been repurposed into attractive landscapes, the contamination and health risks from polycyclic aromatic hydrocarbons (PAHs) on industrial legacy surfaces remain unexplored. We collected 441wiping surface samples from 95 buildings and facilities at Beijing coking plant in China and found that the concentrations of 16 US EPA priority PAHs (∑16PAHs) ranged from ND-982.16 and ND-4262.20 mg/m2 on the surfaces of buildings and facilities, respectively. The main source of PAHs was the coking process, and spatial distribution of PAHs was consistent with ∑16PAHs in the soil. The carcinogenic risks of BaP, DBA, BbF, BaA, Ind of the facilities remained as industrial heritage relics, and those of Bap, DBA and BbF in the buildings with commercial uses exceeded the acceptable level (10−6). The hazard quotient of 9 PAHs was below the acceptable level (1.0). The remedial goals for BaP and DBA (0.11 mg/m2) and BbF, BaA and Ind (1.14 mg/m2) at the facility heritage relics were derived. Similarly, the RGs for the buildings with commercial uses of BaP, DBA and BbF were 0.16, 0.16, and 1.64 mg/m2, respectively. Overall, we determined that carcinogenic PAHs on the surfaces of industrial legacy should be regulated for regeneration.

Concentrations, sources, and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in black, green and fruit flavored tea in Turkey

This study was performed to identify the levels and possible sources of EPA priority PAHs in different types of commercially sold and consumed tea samples in Turkey. Health risk related to PAHs exposure due to tea consumption was also estimated. The average total PAH concentrations were measured as 317.0, 352.3, and 452.3 μg/kg for 25 black, three green, and 12 flavored Turkish tea samples. The results showed that 3- and 4-ring PAHs were the predominant groups for all tea samples. Factor analysis was utilized to identify the source characteristics of PAHs in tea samples. The results indicated that emissions from direct contact during transport and storage of tea leaves have significant impacts in addition to those from thermal processing during production. The estimated lifetime cancer risks ranged from 4.4 × 10−5 to 2.0 × 10−4 for all tea samples, indicating low-to-moderate risks for consumers of these tea products. All the estimated cancer risk values for PAHs in this study were higher than permissible risk levels, while three flavored tea samples were higher than the acceptable risk levels specified by US EPA.