Heavy Polycyclic Aromatic Hydrocarbons Research Articles

Microbial electrochemical enhanced composting of sludge and kitchen waste: Electricity generation, composting efficiency and health risk assessment for land use

To realize the energy and resource utilization from organic solid waste, a two-phase microbial desalination cell (TPMDC) was constructed using dewatered sludge and kitchen waste as the anode substrate. The performance of electricity generation and composting efficacy was investigated, along with a comprehensive assessment of the potential health risks associated with the land use of the resulting mixed compost products. Experimental outcomes revealed a maximum open-circuit voltage of 0.893 ± 0.005 V and a maximum volumetric power density of 0.797 ± 0.009 W/m³. After 90 days of composting enhanced by microbial electrochemistry, a significant organic matter removal rate of 31.13 ± 0.44 % was obtained, and the anode substrate electric conductivity was reduced by 30.02 ± 0.04 % based on the anode desalination. Simultaneously, there was an increase in the content of available nitrogen, phosphorus, and potassium, as well as an improvement in the seed germination index. The forms of heavy metals shifted from bioavailable to stable residual states. The non-carcinogenic hazard index (HI) values for heavy metals and polycyclic aromatic hydrocarbons (PAHs) during the land use of compost products were less than 1, and the total carcinogenic risk (TCR) values for heavy metals and PAHs were below the acceptable threshold of 10−4. The occupational population risk of infection from five pathogens was higher than that of the general public, with all risk values ranging from 8.67 × 10−8 to 1, where the highest risk was attributed to occupational exposure to Legionella. These outcomes demonstrated that the mixture of dewatered sludge and kitchen waste was an appropriate anode substrate to enhance TPMDC stability for electricity generation, and its compost products have promising land use suitability and acceptable land use risk, which will provide important guidance for the safe treatment and disposal of organic solid waste.

Diffusion coefficients of polycyclic aromatic hydrocarbons in supercritical carbon dioxide: A molecular dynamics simulation study

Supercritical carbon dioxide (SC-CO2) extraction technology is an effective way to deal with soil contamination problems. Among them, polycyclic aromatic hydrocarbons (PAHs) are one of the main pollutants in soil. Studying the diffusion coefficients of PAHs in SC-CO2 can help us better understand the mass transfer characteristics during the SC-CO2 extraction process. Molecular dynamics simulation was applied in this work to study the diffusion behavior of PAHs in the SC-CO2 environment. Under different SC-CO2 thermodynamic states (temperature: 313–373 K, pressure: 10–30 MPa) and molecule sizes, the diffusion coefficients of PAHs were calculated. The trend of the interaction energy between PAHs and SC-CO2 molecules as temperature, pressure, and molecule size changed was also investigated. The findings demonstrated that compared to heavy PAHs, light PAHs had a higher diffusion coefficient in SC-CO2. Changes in the system’s temperature and pressure have an important effect on the diffusion coefficients of PAHs in SC-CO2. The high-temperature and low-pressure conditions had a promoting effect on the diffusion behavior of PAHs molecules. The van der Waals energy accounts for the largest proportion of the intermolecular interaction energy, which was about 80 %. It can be concluded that the van der Waals interaction energy played an important impact on the diffusion process of PAHs molecules in SC-CO2.

Polycyclic aromatic hydrocarbon (PAH) phytoaccumulation in urban areas by Platanus × acerifolia, Celtis australis, and Tilia grandifolia leaves and branches.

Polycyclic aromatic hydrocarbon (PAH) concentrations in the leaves and 1-year-old branches of three common tree species growing in a middle-sized city located in a moderate climate zone were estimated. For this purpose, PAH phytoaccumulation in Platanus × acerifolia, Celtis australis, and Tilia grandifolia species from highly urbanized, traffic congested, and highly PAH-contaminated streets was compared with trees from non-contaminated parks in the same urban core. The gathered data was used to define 17 PAH profiles, identify the main PAH pollution emission sources, and determine the organ and species specificity of PAHs accumulation. Due to the direct absorption of polluted air via stomata, the leaves accumulated up to 30% more PAHs compared to the 1-year-old branches. As expected, PAH concentrations were much higher in street trees, while heavy weight PAHs (with five and six rings) were accumulated in the highest concentrations. The highest foliar Σ17 PAH concentrations were detected in street-grown C. australis, followed by P. acerifolia and T. grandifolia (502.68, 488.45, and 339.47ngg-1 dry weight (DW), respectively). The same pattern was noted for Σ17 PAHs in branches (414.89, 327.58, and 342.99ngg-1 DW, respectively). Thus, T. grandifolia emerged as the least effective PAH sink as it accumulated up to ~ 40% less PAHs than P. acerifolia and C. australis leaves/branches. Among the 17 tracked PAHs, benzo[a]anthracene, benzo[a]pyrene, dibenzo[a,h]anthracene, and pyrene were found to have accumulated in the highest concentrations in all analyzed species irrespective of the site, and accounted for more than 50% of the total detected PAHs. Finally, a "black box" about species and organ specificity, as well as specific drivers that limit PAHs uptake capacity by trees, was opened, while this work provides insights into further PAH phytoremediation strategies.

The Stabilizing Effect of Chitosan‐Modified Biochar (β‐CD/C‐BC) on Agricultural Soil Contaminated by the Cd‐Pyr Complex

AbstractThe composite pollution of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in agricultural soil is increasingly severe. HMs can undergo surface adsorption, complexation, or chemical reactions to transform from bioavailable species to residual species, achieving chemical morphological stability. However, these processes have no effect on PAHs. Biochar (BC), due to its inherent characteristics, can significantly enhance the stability of PAHs and is recommended as a potential co‐stabilizing material for both heavy metals and PAHs. In this study, rice husk biochar modified with β‐cyclodextrin and chitosan (β‐CD/C‐BC) was utilized to stabilize agricultural soil contaminated by Cd and Pyrene (Pyr). One‐way tests were conducted on the dosage and curing time of biochar after a complete cycle of treatment. The results demonstrated that the optimal effect was achieved when the dosage of β‐CD/C‐BC was 7.5 % or the curing time was 21 days. The removal efficiencies for Cd and Pyr were found to be 84.62 %, 64.22 % or 85.90 %, 65.78 %, respectively. Additionally, BCR testing revealed that β‐CD/C‐BC could convert HMs in soil into a residual state (from 32 % to 82 %) with the highest stabilization rate, thereby reducing their migration ability and ecological risk.

Molecular dynamics simulation of polycyclic aromatic hydrocarbons solvation behavior in supercritical carbon dioxide under different pressure and temperature

In this work, the solvation behavior of polycyclic aromatic hydrocarbons (PAHs) in supercritical carbon dioxide (sCO2) was investigated by molecular dynamics simulation. The effects of changing temperature and pressure on the solvation behavior were studied. In addition, the value of the interaction binding energy of PAHs-sCO2 and the radial distribution function at various conditions was calculated to study the solvation mechanism. The simulation results showed that high pressure and low temperature can promote the solvation of PAHs in sCO2. However, the effect of pressure change on the solvation behavior was considerably less noticeable than that of temperature change. Furthermore, the solvation of heavy PAHs appeared to be harder than light PAHs. The interaction energy between sCO2 and PAHs decreased as temperature increased, while increased as pressure increased. Moreover, the interaction mechanism analysis found that the van der Waals interaction force dominated the interaction force between sCO2 and PAHs molecules.

Rice husk and its derived biochar assist phytoremediation of heavy metals and PAHs co-contaminated soils but differently affect bacterial community

In order to evaluate the feasibility of rice husk and rice husk biochar on assisting phytoremediation of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) co-contaminated soils, a 150-day pot experiment planted with alfalfa was designed. Rice husk and its derived biochar were applied to remediate a PAHs, Zn, and Cr co-contaminated soil. The effects of rice husk and biochar on the removal and bioavailability of PAHs and HMs, PAH-ring hydroxylating dioxygenase gene abundance and bacterial community structure in rhizosphere soils were investigated. Results suggested that rice husk biochar had better performance on the removal of PAHs and immobilization of HMs than those of rice husk in co-contaminated rhizosphere soil. The abundance of PAH-degraders, which increased with the culture time, was positively correlated with PAHs removal. Rice husk biochar decreased the richness and diversity of bacterial community, enhanced the growth of Steroidobacter, Bacillus, and Sphingomonas in rhizosphere soils. However, Steroidobacter, Dongia and Acidibacter were stimulated in rice husk amended soils. According to the correlation analysis, Steroidobacter and Mycobacterium may play an important role in PAHs removal and HMs absorption. The combination of rice husk biochar and alfalfa would be a promising method to remediate PAHs and HMs co-contaminated soil.

Human health risk assessment of PM10-bound heavy metals and PAHs around the Latin America’s Largest opencast coal mine

Air pollution in opencast coal mine areas is a critical issue, resulting in harmful severe effects on human health. Therefore, it is essential to understand the air pollution factors and to assess the risks to humans. This study evaluated the potential risks (carcinogen and non-carcinogen) of inhalation exposure to PM10-bound heavy metals and Polycyclic Aromatic Hydrocarbons (PAHs) in an open pit mine in northern Colombia. During February-May 2022, PM10 samples were collected at eight sites. Heavy metals (i.e., Al, Cr(VI), Mn, Cu, Zn, As, Pb) and PAHs (thirteen priority PAHs, and one non-priority PAH) levels linked to PM10 were analyzed by X-ray fluorescence and gas chromatography–mass spectrometry, respectively. PM10 concentrations were found to range between 4.70 and 59.90 µg m−3. Out of the three different zones of the study area (i.e., North Zone, South Zone, and Populated Zone), the North Zone recorded the highest daily average concentrations of Cr(VI) (104.16 ng m−3), Mn (28.39 ng m−3), Cu (33.75 ng m−3), Zn (57.99 ng m−3), As (44.92 ng m−3), and Pb (27.13 ng m−3). The fraction of the analyzed heavy metals at all monitoring sites was 82%–89% for Al, followed by Cr(VI) with 3%–6%. Cr(VI) was the major contributor to the carcinogenic risk values, while Cu, Cr(VI), and As were the main drivers for the non-carcinogenic risk. The average cancer risk range for heavy metals was 3.30 × 10–04 –5.47 × 10–04. On the other hand, the cancer risk for PAHs exposure was acceptable. The average incremental lifetime cancer risk (ILCR) values varied between 2.87 × 10–07 and 4.21 × 10–07. Benzo[a]pyrene contributed to 54%–56% of the total risk from inhalation of PM10-bound PAHs, while Indeno[1,2,3-cd]pyrene contributed to 16%–19%. Based on the Monte Carlo sensitivity analysis, exposure to Cr(VI) was the main factor affecting cancer risk in the North, South, and Populated Zones. A suitable risk assessment and management plan requires understanding PM10-bound heavy metals and PAHs concentration levels as well as their potential health risks, mainly in open-cast coal mine zones. Our study found that people living near open-pit mines face potential health risks, so it is crucial to establish policies and regulations to control emission sources.

Research on the presence of cigarette butts and their leaching of chemical pollutants and microparticles: the case of Dalian, China

Cigarette butts (CBs) can contain high amounts of toxic substances such as heavy metals, polycyclic aromatic hydrocarbons (PAHs) and microplastics, all of them can result from the incomplete decomposition of CBs. However, limited research exists on the pollution caused by littered CBs in China and the emissions of toxic substances from different Chinese cigarette brands.Therefore, the main objective of this study was to assess the quantity of CBs littered in Dalian city, China, and to evaluate the emissions of heavy metals, PAHs, and microplastics from different cigarette brands. During the survey, a total of 10,591 CBs items and 35 cigarette brands were collected. ICP-MS analysis confirmed the presence of 17 types of heavy metals in the highest abundance brand of CBs, with concentrations ranging from 0.02 μg/L (U and La) to 395 μg/L (Mn). In the lowest abundance brand of CBs, 15 types of heavy metals were detected, with concentrations ranging from 0.08 μg/L (U) to 297 μg/L (Mn). Additionally, a total of 9 PAHs, including compounds such as naphthalene and acenaphthylene, were detected in both the highest and lowest abundance brands of CBs using HPLC-MS/MS, with concentrations ranging from 0.40 ng/L (Anthracene) to 92.12 ng/L (Naphthalence). Microplastics and particles were also identified by light microscopy and SEM. Based on cigarette consumption data in China, it is estimated that annually 360,000 tons of plastic waste are generated by CBs in the environment. Considering the presence of CBs in urban and beach environments, the release of these toxic substances poses a threat to water resources.

Pollution Status of Inland Waterways Serving as Receptacles to Plastic Waste in Rivers State, Nigeria

This study aimed at ascertaining the physicochemical characteristics of selected water bodies receiving solid plastic waste in Rivers State, Nigeria. Surface water and sediment samples were analysed for physicochemical parameters. Water, sediment and fish samples were monitored for presence of polychlorinated bisphenols (PCBs) and polycyclic aromatic hydrocarbons (PAHs). All physicochemical parameters monitored in Bonny River water and sediment samples were within WHO acceptable. However, the concentrations of nitrate and phosphate (62.675 and 1.28 ppm) in New Calabar River water samples were above WHO limits of 10 and 1 ppm respectively. The Cd values (0.045-8.27 mg/l) at both locations exceeded WHO 0.003 mg/l limit. Likewise, Mn concentrations (6.02-15.5 mg/l) exceeded WHO 5.5 mg/l. Mercury (0.075-1.39 mg/l) was the lowest occurring heavy metal in the water samples but the concentration was still high enough for concern, as the possibility for bioaccumulation in fish species in the river was high. Chloride levels (318.375-423.045 mg/l) in the water samples exceeded WHO limit of 250 mg/l for drinking water. The samples also had high iron content (0.635-16.19 mg/l). PAHs concentrations (252.0155-3533.14 ppm) in the water samples far exceeded the safe level of 10 mg/l for drinking water standard. PCBs levels in all fish samples (21.56-83.08 ppm) exceeded WHO maximum limit of 0.2 mg/kg Surface water, sediment and fish sampled contained objectionable concentrations of heavy metals, PCBs and PAHs. Users of these rivers for domestic purposes are at high risk of chemical poisoning from heavy metals, PCBs and PAHs.

The effect of biotransformation of sewage sludge- and willow-derived biochars by horseradish peroxidase on total and freely dissolved polycyclic aromatic hydrocarbon content

This study analyzed the effect of enzymatic aging (horseradish peroxidase) of biochars on their content of solvent extractable (Ctot) and freely dissolved (Cfree) polycyclic aromatic hydrocarbons (PAHs). Physicochemical properties and phytotoxicity of pristine and aged biochars were also compared. The study used biochars obtained at 500 or 700 °C from sewage sludges (SSLs) or willow. Compared to SSL-derived biochars, willow-derived biochars were more susceptible to enzymatic oxidation. Aging increased the specific surface area and pore volume of most SSL-derived biochars. An opposite direction, however, was found in the willow-derived biochars. Low-temperature biochars, regardless of their feedstock, underwent physical changes, such as removal of labile ash components or degradation of aromatic structures. The enzyme caused an increase in the content of Ctot light PAHs in biochars (by 34–3402 %) and heavy PAHs (≥4 rings) in the low-temperature SSL-derived biochars (by 46–713 %). In turn, the content of Cfree PAHs decreased in aged SSL-derived biochars (by 32–100 %). In the willow-derived biochars the bioavailability of acenaphthene increased (by 337–669 %), while the immobilization degree of some PAHs was lower (25–70 %) compared to the SSL-derived biochars (32–83 %). Nevertheless, aging positively affected the ecotoxicological properties of all biochars by increasing their stimulation effects or removing their phytotoxic effects on both Lepidium sativum seed germination and root growth. Significant relationships between the changes in Cfree PAH content, pH and salinity of SSL-derived biochars and seed germination/root growth inhibition were found. The study demonstrates that the risk associated with application of SSL-derived biochars, regardless of the type of SSL and pyrolysis temperature, can be lower in terms of Cfree PAHs than in the case of willow-derived biochars. Regarding to Ctot PAHs, high-temperature SSL-derived biochars are safer than low-temperature ones. In the case of application of high-temperature SSL-derived biochars, these with moderate alkalinity and salinity will not bring risks for plants.

Risk assessment of polycyclic aromatic hydrocarbons and organochlorine pesticides in olive oil in Jordan

Many organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) pose risks to human health; so, their levels in foods should be constantly monitored. In the present work, the potential health risks of 21 OCPs residues and 16 carcinogenic PAHs in Jordanian olive oil were evaluated. A total of 27 olive oil samples were obtained from nine olive mills in Jordan. The levels of PAHs and OCPs were evaluated by gas chromatography coupled with mass spectrometry detector. Among the studied pesticides, only 4,4-Dichlorodiphenyldichloroethylen (4,4-DDE) was found in the tested samples. The estimated average dietary intake (EADI) and hazard risk index (HRI) were then assessed for the 4,4-DDE. The estimated HRI value of 4,4-DDE was less than 1, thus indicating no health risk to consumers. Regarding PAHs, the average concentration of 16 PAHs in the tested olive oil was 36.5 µg/kg. Health risks due to PAH contamination were estimated by determining the dietary daily intake (DDI) and toxic equivalent quotient (TEQ). The values ranged from 0.139 × 10-2 to 7.70 × 10-2 and 0.01 to 0.57 µg/kg for DDI and TEQ, respectively. Light PAHs were predominant in the samples, while no heavy PAHs were detected. The incremental lifetime cancer risk (ILCR) was estimated, and the values ranged from 0.1 × 10-7 to 5.62 × 10-7, and none of the olive oil samples exceeded the limit value of 10-6, thus indicating insignificant potential risk.

Synergistic cancer risk assessment from PM1 bound metals and PAHs in the Indo-Gangetic Region

The atmospheric particulate matter (PM) contains a significant amount of human carcinogens such as metals and Polycyclic Aromatic Hydrocarbons (PAHs). Previous studies have clearly shown that these carcinogens pose serious health issues due to the inhalation of particulate matter. Since the synergistic roles of these carcinogens are rarely considered, these studies frequently underestimate the health risk to humans. The current research aims to bridge this information gap by estimating the synergistic carcinogenic risk assessment owing to PM1 bound metals and PAHs across the densely populated Indo-Gangetic Plain (IGP). The carcinogenic risk assessment was conducted in accordance with the USEPA guidelines on these various PM1 bound components. The Incremental Lifetime Cancer Risk (ILCR) due to heavy metals, such as Lead (Pb) and Chromium (Cr), was found beyond the acceptable limit (> 10−4). The risk due to PM1 bound USEPA PAHs was also significantly higher (> 10−5). This study further estimated the potential toxicity from broad domain of environmental PAHs present in ambient air by considering relevant estimation factors from existing literature. The projected risk from these diverse environmental PAHs was of the order 10−4. Further, source identification of PAHs based on diagnostic isomer ratios revealed that diesel exhaust, biomass burning, and coal combustion are the dominant PAHs sources. Moreover, the exposure to these pollutants is higher in winter and post-monsoon periods. Overall, the synergistic carcinogenic risk found from metals and PAHs was of the order 10−3. In a nutshell, inhalation of PM1 bound heavy metals and PAHs at IGP can result in the development of 1000 cancer cases per million population, which is the highest value compared to other parts of the world. The present study demands immediate policy interventions not only for the reduction of particulate pollution, but also for the reduction of carcinogenic species from the ambient air in order to improve human health.

Health Impacts of Air Pollution in Tianjin

Ambient air pollution is a dominant determinant of health. The health effects and economic losses due to air pollution are very important for decision-making. Since the implementation of the "Air Pollution Prevention and Control Action Plan" and "blue sky defense war" policies, the air quality of Tianjin has changed significantly. Here, the health effects and economic losses attributable to ambient air pollution in Tianjin from 2013 to 2020 wereestimated. For the particulate matter which has complex components, we assessed the inhalation health risks of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in PM2.5. The variation in the concentration of the main components of PM2.5 was also analyzed. The results showed that improved air quality had positive health benefits. The health benefits from SO2 were the highest among the six air pollutants, and 3786 deaths were avoided in 2020 compared to in 2013 due to lower SO2 concentration. The economic losses caused by air pollutants ranged from several billion to ten billion yuan. Among the six air pollutants, particulate matter and ozone had higher health losses in recent years. The health risks of heavy metals and PAHs in PM2.5 showed a decreasing trend. However, Cr(Ⅵ), As, Cd, and Ni in PM2.5in the winter of 2020 still had respiratorysystem carcinogenic risk, whereas there was no health risk of PAHs in PM2.5in 2019-2020. The concentrations of main components of PM2.5 have decreased significantly. In the future, the reduction of health loss caused by air pollution depends on synergy governance of particulate matter and ozone and further research on health effects.

Comparison of generic Tenax and specialized PAH tubes for monitoring polycyclic aromatic hydrocarbons in the ambient air

The thermal desorption (TD) technique has potential advantages for monitoring polycyclic aromatic hydrocarbons (PAHs) in the air, e.g., no need for sample preparation. This study aims to compare the performance of two types of TD tubes: the generic Tenax TA tube and a proprietary PAH tube specifically designed for PAH sampling. Full calibrations were performed on a TD-gas chromatography/mass spectrometry (GC/MS) system for 16 priority PAHs. Co-located field samples were collected with two tubes at a flow rate of 200 mL/min for 24 h in eight rounds. In the laboratory, blank Tenax and PAH tubes had trace-level PAHs ranging from 0 to 0.35 ng/tube and 0−0.83 ng/tube, respectively, after 2-hr conditioning at 330 °C. The calibration with Tenax tubes showed an average precision of 7.5%, R2 from 0.9959 to 1.0000, and method detection limits (MDLs) from 0.056 to 3.64 ng/m3. The calibration of PAH tubes showed an average precision of 7.5%, R2 from 0.9945 to 1.0000, and MDLs from 0.065 to 5.91 ng/m3. In the field, blank Tenax and PAH tubes had trace PAH levels of 0.01–0.34 ng/tube and 0.01−0.42 ng/tube, respectively. Both tubes had negligible breakthroughs (<4%) and good precisions (<20%). Co-located Tenax and PAH tubes displayed a good agreement for light PAHs (differences mostly <30%) but high uncertainty for heavy PAHs (difference 35−70%). Both tubes are applicable for PAH monitoring, but the proprietary PAH tube does not outperform the generic Tenax TA tube. More work is still needed to improve the sensitivity of TD methods for heavy PAHs, e.g., selecting appropriate sorbents and adopting advanced instruments.

Influence of Fuel Oxygenation on Regulated Pollutants and Unregulated Aromatic Compounds with Biodiesel and n-Pentanol Blends

It is very important to determine the polycyclic aromatic hydrocarbon (PAH) emissions caused by the use of renewable fuels in diesel engines and to know the possible damages. This study investigates the emissions (regulated and unregulated) of biodiesel/n-pentanol mixtures, which are free of aromatic content, with emphasis on PAH formation and an examination of toxicity to public health and the environment. Engine failures caused by wetstacking are also discussed. Biodiesel/n-pentanol fuel mixtures with alcohol concentrations of 5%, 20%, and 35% by volume (v/v) served as test fuels in a compression ignition engine. A five-gas analyzer was used to measure hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) emissions. Polycyclic aromatic hydrocarbons were detected and measured using gas chromatography-mass spectrometry (GC-MS). Against the baseline diesel fuel, the biodiesel/n-pentanol fuel blends and neat biodiesel reduced NOx emissions and produced significantly fewer PAHs and toxicity, confirming the significance of the aromatic content of the fuel. Biodiesel reduced total PAHs by 48.02% and the addition of 5% n-pentanol to biodiesel further decreased total PAHs by 21.26%. The total toxicity (BaPeq (benzo[a]pyrene equivalent)) as a result of biodiesel was 83.49% less than diesel. The addition of n-pentanol to biodiesel further reduced toxicity by 59.15%, 57.89%, and 48.33% for BPen5, BPen20, and BPen35 blends, respectively. In addition, n-pentanol was shown to be effective for reducing total PAH emissions, as well as heavier PAHs, which have greater carcinogenicity and pose a greater likelihood of engine damage from wetstacking when running in low-load conditions at cold temperatures.

Decoupling effects of C3H3/C4H5/i-C4H5/CN radicals on the formation and growth of aromatics: A ReaxFF molecular dynamics study

This paper demonstrates the effects of C3H3/C4H5/i-C4H5/CN radicals on the formation and growth of aromatic hydrocarbons, particular types of polycyclic aromatic hydrocarbons (PAHs) such as heavier-PAHs, cyclopentafused PAHs (CP-PAHs), through reactive force field molecular dynamics simulations under 2250K and 2500K. Adding non-acetylene radicals enhanced the early-stage mass growth of aromatics to varying degrees. However, the later-stage mass growth and aromaticity degree were weakened by adding radicals except for the C3H3 radical. The reactivity of acetylene and additional radicals showed that the additional C3H3 radicals accelerated the consumption of radical pools, and the interaction reaction between C3H3 was responsible for the consumption of radical pools for the C3H3 additive case. The consumption of i-C4H5 was significantly faster than that of C4H5, whereas the consumption of acetylene in the two simulation cases was essentially the same. Thus, the i-C4H5 simulation case formed more intermediate species C6H7 than C4H5 radical. As for the formation of less-studied PAHs, i-C4H5 radicals generated more heavier PAHs and CP-PAHs than straight butyl C4H5 isomers. Finally, the effect of nitrogen-containing radical CN, which normally resides in ammonia fuel, was analyzed. Several factors explained the stronger enhancement in aromatic mass growth, but the relatively lowest aromatization degree resulted from the additional CN radicals. The reactions between CN and acetylene formed carbon–nitrogen species that participated less in the formation and growth of aromatics. The potential reactions between CN radical and aromatics led to ring-opening reactions and the formation of nitrogen-membered rings, which accelerated the mass growth of carbon clusters but inhibited the development of aromaticity degree. The least amount of CP-PAHs was found in CN cases compared with hydrocarbon radical cases.

Polycyclic Aromatic Hydrocarbons in Popcorn Corn Varieties and Popcorns

Popping corn is a widespread activity and popcorns are one of the most consumed snacks in the world. As popcorn corn is exposed to environmental conditions and agrotechnical measures in the field, polycyclic aromatic hydrocarbons (PAHs) can end up in corn kernels. Since popcorns are popped at higher temperatures, ca. 180 °C, it is reasonable to assume that PAHs can be found in popcorns. The objective of this paper was to preliminarily determine and quantify the incidence of various PAHs in different popcorn varieties and popcorns popped from them, during two consecutive years. PAHs were determined by using GC-MS. Popcorn corn contained only light PAHs, naphthalene (Nap), acenaphthene (Ane), and fluorene (Fln). However, popped popcorns contained heavier PAHs, such as benz[a]anthracene (BaA), chrysene (Chry), and benzo[a]pyrene (BaP) whose ∑PAH4 was 8.39 µg/kg in sample 1 in 2020. The results indicate that popcorns can be a significant source of PAHs and further studies should be conducted. This is concerning since popcorns are favored snacks in all age groups, including children.

Electrochemistry-enhanced peroxymonosulfate activation by CoAl-LDH@biochar for simultaneous treatment of heavy metals and PAHs

An EC/CoAl-LDH@biochar/PMS system is proposed in this study for activation of PMS and removal of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs). In this system, over 90% of HMs and PAHs could be effectively removed after 40 min. Compared to other systems, the synergy between CoAl-LDH@biocahr and electrochemistry (EC)-peroxymonosulfate (PMS) had an excellent ability to eliminate the combined pollutants. The precise effect of the experimental parameters, including pH, CoAl-LDH@biochar dose, current density, and PMS concentration, on HMs-PAHs removal was determined, and the system was found to have a broad working pH range. The presence of EC can overcome the inhibition of anions in the degradation of PAHs due to the direct oxidation of PMS and PAHs on the cathode. The scavenging tests confirmed that the free radical and non-radical processes contributed to the degradation of PAHs. It is also revealed that EC can promote the continuous circulation of transition metals, which enhances the activation of PMS. The adsorption on the surface of CoAl-LDH@biochar and electrochemical deposition were the two main mechanisms for HMs removal. Furthermore, the electrode and CoAl-LDH@biochar possessed favorable recyclability in five consecutive cycles. This study has provided a promising and cost-effective approach for treatment of HM-PAH co-contaminated wastewater.

Combined pollution of heavy metals and polycyclic aromatic hydrocarbons in the soil in Shenfu Region, China: a case of three different cities.

It is a challenging issue to investigate the combined pollution of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in urban soils. The purpose of this study was to determine the concentrations of these two pollutants in soils in Shenyang, Fushun, and Fushun New District, to analyze their distribution, their interaction, and co-contamination levels. The concentrations of heavy metals were measured by inductively coupled plasma mass spectrometry (ICP-MS), while the concentrations of 21 kinds of PAH were analyzed by gas chromatography-mass spectrometry (GC-MS). Based on the analysis of pollution concentrations and distribution patterns, the intrinsic links between heavy metals and PAHs in three different cities were assessed using a variety of multivariate analysis methods. Compared to Shenfu New District, the concentration of pollutants in Shenyang and Fushun shows a higher level. Moreover, the results of redundancy analysis (RDA) of samples may quantify the possibility of combined pollution of different heavy metal elements and PAHs. This study also affirms the important role of multivariate analysis in being used to reveal the complex interactions and spatial distribution of different pollutants.

Microbiological status of natural and anthropogenic soils of the Taganrog Bay coast at different levels of combined pollution with heavy metals and PAHs.

The effect of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) pollution on the microbiological status of soils on the coast of the Taganrog Bay and adjacent areas was studied. The content of total and exchangeable forms of HMs, the content of 16 priority PAHs and the abundance of several groups of culturable microorganisms was determined, namely copiotrophic, prototrophic, aerobic spore-forming bacteria, actinomycetes, molds and yeasts. The content of total and exchangeable forms of HMs in urban coastal soils in industrial zone significantly exceeded that in non-urban soils. The maximum concentrations of total forms of Mn, Cr, Ni, Cu, Zn, Pb and Cd are 1821, 871, 143, 89, 1390, 317 and 10mg/kg, respectively. The median value of the total content of 16 PAHs in urban soils is 3 times higher than in the soils of natural areas and reached 4309ng/g. The lowest numbers of copiotrophic bacteria, prototrophic bacteria and aerobic spore-forming bacteria were found in the soils of industrial zone: 6.8, 13.8 and 0.63million CFUg-1 dry soil, respectively. The largest numbers of copiotrophic bacteria, prototrophic bacteria and aerobic spore-forming bacteria were recorded in the soils of natural areas-72.5, 136 and 5.73million CFUg-1 dry soil, respectively. It was found that the abundance of copiotrophs, prototrophs, and aerobic spore-forming bacteria is more affected by the urbanization of coastal soils including the pollution of HMs and PAHs. Other groups of microorganisms (actinomycetes, molds and yeasts) turned out to be more resistant to anthropogenic factors.