Ring Polycyclic Aromatic Hydrocarbons Research Articles

Health risk evaluation of toxic polycyclic aromatic hydrocarbons (PAHs) in the street dust of Basra, Iraq

Dust particles on the surface of urban streets considered among the greatest important sources for contamination of urban atmospheres in the form of fine aerosols. This study aimed at determining the concentration of polycyclic aromatic hydrocarbons (PAHs) in the dust samples collected from Basra city streets to evaluate their potential risks to ecosystem, especially, the risk of cancer from dermal contact, inhalation and ingestion. PAHs in street dust samples from Al- Shafi, Al-Qurna, Al Seeba, Abu Kaseeb, Al- Fao and Al Burjessya were measured using gas chromatography/mass spectrometry (GC/MS) in Basra. The important PAHs contaminants classified by US EPA detected in the samples, the main was the 3 fused aromatic rings PAHs (79.82%), followed by 5 rings PAHs (7.9%), 4 rings PAHs (6.6%), 6 rings PAHs (5.4%) and 2 rings PAHs (0.5%). Exposure doses ranged from 6.47E-07 to 1.24E-06 ug/g day for child non-carcinogen and 3.65E-07 to 7.02E-07 ug/g day for adult non-carcinogen. Exposed daily doses less than EPA suggested safe daily doses. HQ values lower than one in all sites, revealed no hazard on health from non-carcinogens. The cancer risk from inhalation was 5.55E-08 to 1.07E-07 for child Carcinogen and 1.25E-07 to 2.41E-07 for adult Carcinogen; it is less than 10-4 within the harmless levels. Carcinogenic risk from inhalation two times less than that of dermal and ingestion.

Effects of Adding Laccase to Bacterial Consortia Degrading Heavy Oil

High-efficiency bioremediation technology for heavy oil pollution has been a popular research topic in recent years. Laccase is very promising for the remediation of heavy oil pollution because it can not only convert bio-refractory hydrocarbons into less toxic or completely harmless compounds, but also accelerate the biodegradation efficiency of heavy oil. However, there are few reports on the use of laccase to enhance the biodegradation of heavy oil. In this study, we investigated the effect of laccase on the bacterial consortia degradation of heavy oil. The degradation efficiencies of bacterial consortia and the laccase-bacterial consortia were 60.6 ± 0.1% and 68.2 ± 0.6%, respectively, and the corresponding heavy oil degradation rate constants were 0.112 day−1 and 0.198 day−1, respectively. The addition of laccase increased the heavy oil biodegradation efficiency (p < 0.05) and biodegradation rate of the bacterial consortia. Moreover, gas chromatography–mass spectrometry analysis showed that the biodegradation efficiencies of the laccase-bacterial consortia for saturated hydrocarbons and aromatic hydrocarbons were 82.5 ± 0.7% and 76.2 ± 0.9%, respectively, which were 16.0 ± 0.3% and 13.0 ± 1.8% higher than those of the bacterial consortia, respectively. In addition, the degradation rate constants of the laccase-bacterial consortia for saturated hydrocarbons and aromatic hydrocarbons were 0.267 day−1 and 0.226 day−1, respectively, which were 1.07 and 1.15 times higher than those of the bacterial consortia, respectively. The degradation of C15 to C35 n-alkanes and 2 to 5-ring polycyclic aromatic hydrocarbons by laccase-bacterial consortia was higher than individual bacterial consortia. It is further seen that the addition of laccase significantly improved the biodegradation of long-chain n-alkanes of C22–C35 (p < 0.05). Overall, this study shows that the combination of laccase and bacterial consortia is an effective remediation technology for heavy oil pollution. Adding laccase can significantly improve the heavy oil biodegradation efficiency and biodegradation rate of the bacterial consortia.

A 110 Year Sediment Record of Polycyclic Aromatic Hydrocarbons Related to Economic Development and Energy Consumption in Dongping Lake, North China.

A sedimentary record of the 16 polycyclic aromatic hydrocarbon (PAH) pollutants from Dongping Lake, north China, is presented in this study. The influence of regional energy structure changes for 2–6-ring PAHs was investigated, in order to assess their sources and the impact of socioeconomic developments on the observed changes in concentration over time. The concentration of the ΣPAH16 ranged from 77.6 to 628.0 ng/g. Prior to the 1970s, the relatively low concentration of ΣPAH16 and the average presence of 44.4% 2,3-ring PAHs indicated that pyrogenic combustion from grass, wood, and coal was the main source of PAHs. The rapid increase in the concentration of 2,3-ring PAHs between the 1970s and 2006 was attributed to the growth of the urban population and the coal consumption, following the implementation of the Reform and Open Policy in 1978. The source apportionment, which was assessed using a positive matrix factorization model, revealed that coal combustion was the most important regional source of PAHs pollution (>51.0%). The PAHs were mainly transported to the site from the surrounding regions by atmospheric deposition rather than direct discharge.

Pollution Characteristics and Risk Assessment of Polycyclic Aromatic Hydrocarbons in a Suburban Farmland Soil

In order to assess the pollution of polycyclic aromatic hydrocarbons(PAHs) in a suburban farmland soil, 29 sampling sites were collected around Nanjing according to the grid method, and the contents of 15 different PAHs were determined. Acenaphthene(Ace) was not detected in any of the samples. The total content of PAHs in farmland soil ranged from 24.49 to 750.04 μg·kg-1, with an average of 226.64 μg·kg-1. The spatial distribution of high-ring PAHs, the main PAHs in the farmland soil, was similar to that of total PAHs. There was no significant correlation between PAHs and soil organic matter(SOM), pH, cation exchange capacity(CEC), and total nitrogen(TN), whereas bulk density and low ring PAHs were significantly correlated. The results of source apportionment show that the main source of PAHs in the farmland soil is a mixture of combustion and petroleum. The contamination severity index(CSI) index shows that the PAHs does not pose an ecological risk. The results of the health risk assessment show that there is no potential carcinogenic risk to children or adults, and the main sequence of exposure is skin contact>ingestion>inhalation.

Levels of polycyclic aromatic hydrocarbons in leachates from unlined dumpsite of Agu-Awka Anambra state

ABSTRACT Disposal of solid wastes in an unlined dumpsite is the most common waste disposal practice in Nigeria. Percolations of leachates containing polycyclic aromatic hydrocarbons (PAHs) from unlined dumpsites are known to cause environmental hazards which pose significant health risks to human lives. The collection of the leachates were done during the wet season for 4 months. The levels of PAHs concentration in the leachates were determined using gas chromatography. The health-related risks were determined using toxicity and mutagenic health risk assessment. Isomeric ratios were used to deduce possible origins of PAHs in the leachates. The mean values of the PAH levels ranged from 0.1 − 14.9 µg/L. The benzo (g,h,i) pyrene reported the maximum level of PAHs (14.9 µg/L) followed by anthracene (12.7 µg/L). The 3 – ring PAHs recorded the highest PAHs, while the 2- ring was the least dominant PAHs. The isomeric profile indicated mixed sources (pyrolytic and petrogenic) with a dominant petrogenic source observed. The benzo(a)pyrene toxicity and mutagenic quotients disclosed its ability to trigger cancer and non–cancer-related risks to a living organism.

Enhanced bioremediation of sediment contaminated with polycyclic aromatic hydrocarbons by combined stimulation with sodium acetate/phthalic acid

In this study, four groups of laboratory scale experiments were performed by adding sodium acetate (SA), phthalic acid (PA), and SA-PA to river sediment to observe the microbial response and biodegradation efficiency of polycyclic aromatic hydrocarbons (PAHs). The results showed that the amount of total organic carbon consumed and the amount of sulfate reduction were both positively correlated (p < 0.01) with the biodegradation efficiency of the sum (∑) PAHs (∼40.5%). The lower the number of rings, the more PAHs were biodegraded, with an efficiency of 63.0% for ∑ (2 + 3) ring PAHs. Based on high-throughput sequencing and molecular ecological network analysis, it was found that the combined stimulation of SA and PA not only increased the relative abundance of PAHs-degrading bacterial (eg., Proteobacteria, Desulfobacterota, Campilobacterota and Firmicutes), but also had a strengthening effect on microbes in sediments. The altered microbial structure caused a variation in metabolic functions, which increased the amino acid metabolism to 12.2%, thus increasing the positive correlations among genera and improving the connectivity of the microbial network (p < 0.01). These changes may be responsible for the enhanced biodegradation of PAHs under SA-PA dosing in comparison to SA or PA dosing alone. This study revealed that the microbial community was stimulated by the combined addition of SA and PA, and indicated its role in enhancing biodegradation of PAHs in contaminated river sediments.

Seasonal and Temporal Influence on Polycyclic Aromatic Hydrocarbons in the Red Sea Coastal Water, Egypt

This study investigated seasonal variation, spatial distribution, sources, composition and potential ecological risks of 16 polycyclic aromatic hydrocarbons (PAHs) in Red Sea coastal water. Surface seawater samples were collected at fourteen different locations. The sum of 16 PAHs concentrations in Red Sea showed clear variation between seasons, ranged from 1.08–6.10, 0.79–50.86, 1.37–54.47 and 0.21–7.18 μg/L in summer, autumn, winter, and spring respectively. PAHs levels in Red Sea coastal waters were relatively high at certain sites during autumn and winter seasons. They could be classified as highly polluted by PAHs contaminants (&gt;10 μg/L). According to the diagnostic ratios measured, the majority of PAHs in this study originated from pyrogenic sources, while minor amounts originated from petrogenic sources. Four rings PAHs accounted for more than 64% of the total PAHs studied. PAHs pose a high ecological risk along the period of study, according to the ecological risk assessment by Risk quotients (RQNCs and RQMPCs).

Release characteristics of polycyclic aromatic hydrocarbons (PAHs) leaching from oil-based drilling cuttings

Drilling cuttings, the primary byproduct from the exploration and mining of shale gas, are potentially hazardous wastes that are associated with the serious depletion of land resources and environmental safety problems. In this work, the distribution of polycyclic aromatic hydrocarbons (PAHs) in oil-based residues of shale gas drilling cuttings was studied. Furthermore, a column leaching test was carried out to investigate the leaching behaviour of PAHs. The results showed that (1) the concentrations of 4-ring PAHs were highest among the PAH concentrations detected from the oil-based residues, and the concentration of PAHs decreased with increasing particle size of the residues. (2) The PAH concentration in leachates from all the tested residues differed during the leaching process, and the cumulative amount of each leached PAH accounted for 1.50–3.20% of the total PAHs. (3) The first-order diffusion model (FRDM) was the most applicable model for describing the leaching characteristics of the PAHs, and the leaching rate was initially controlled by surface wash-off and then by diffusion.

Spatial distribution of polycyclic aromatic hydrocarbons in the Philippine Sea, Western Pacific and the impact factors analysis

Knowing the polycyclic aromatic hydrocarbons (PAHs) pollution properties in ocean is highly needed to protect the open sea. In July to August of 2020, twenty surface water samples were obtained from the East China Sea to the Philippine Sea. The ranges of Σ15PAHs concentrations were 3.188–5.29 ng L−1 in dissolved phase, 0.455–1.305 ng L−1 in particulate phase in the Philippine Sea. 3, 4-Ring PAHs were the most abundant PAHs. Their spatial differences in dissolved phase were mainly caused by human activities, the summer monsoon from the Philippine Islands and the Northern Equatorial Current, and the Kuroshio Current and Subtropical Countercurrent. The source analysis showed that PAHs in surface water in the Philippine Sea may come from coal combustion. It is the first time to analyze the occurrence and distribution of PAHs in the Philippine Sea.

Comparing the sorption of pyrene and its derivatives onto polystyrene microplastics: Insights from experimental and computational studies

In this study, the sorption behaviors and mechanisms between polystyrene microplastics (micro-PS) and 4-rings polycyclic aromatic hydrocarbons (PAHs) pyrene (Pyr) and its derivatives (S-Pyr), including 1-methylpyrene (P-CH3), 1-hydroxypyrene (P-OH), 1-aminopyrene (P-NH2), 1-pyrenecarboxylic acid (P-COOH) were investigated at neutrality. The results revealed that the sorption rates of micro-PS for S-Pyr were higher than those for parent Pyr. Meanwhile, -CH3 could slightly facilitate the sorption, whereas -OH, P-NH2, and P-COOH intensively inhibit the sorption of S-Pyr onto micro-PS. The sorption capacities of Pyr/S-Pyr increased with decreasing size of micro-PS. Besides, the effects of salinity and temperature on the sorption characteristics of micro-PS for Pyr/S-Pyr depended on their substituents. Combined with experimental and computational methods, it could be concluded that the main sorption mechanisms were possibly hydrophobic interaction, π-π interaction and pore-filling. The observations reported here could improve predictions of environmental behaviors and bioavailability of PAHs and micro-PS.

Characteristics of PM and PAHs emitted from a coal-fired boiler and the efficiencies of its air pollution control devices

ABSTRACT Sampling and analysis of filterable particulate matter (FPM), FPM2.5, condensable particulate matter (CPM), polycyclic aromatic hydrocarbons (PAHs), sulfur oxides (SOx) and nitrogen oxides (NOx) emitted from a coal-fired boiler equipped with selective catalytic reduction (SCR)+ electrostatic precipitator (ESP) + wet flue gas desulfurization (WFGD) + wet electrostatic precipitator (WESP) as air pollution control devices (APCDs) are conducted. The results show that NOx concentration emitted from the coal-fired boiler is 56 ± 2.17 ppm (with the NOx removal efficiency of 47.2%), which does not meet the best available control technology (BACT) emission standard (≤ 30 ppm). On the other hand, the WFGD adopted has a good removal efficiency for SOx and HCl. Both SOx and HCl emission concentrations are <1 ppm, and removal efficiencies are >99%. The FPM and FPM2.5 emitted from the coal-fired boiler are 0.9 ± 0.06 mg/Nm3 and <0.09 ± 0.006 mg/Nm3, respectively. The overall removal efficiency of FPM achieved with ESP+WFGD+WESP+MGGH is 99.98%. However, high concentration of CPM (37.4 ± 6.3 mg/Nm3) is measured, which is significantly higher than FPM and FPM2.5. The concentrations of 27 PAHs at the WESP inlet and stack are measured as 667 ng/Nm3 and 547 ng/Nm3, respectively while the removal efficiencies of gas- and solid-phase PAHs are 9% and 58%, respectively. The results show that APCDs adopted are not effective in removing PAHs (only 18%), and gas-phase PAHs contribute the most in the total PAH emission. In addition, the benzo(a)pyrene equivalent (BaPeq) concentration emitted from the stack is 28.8 ng-BaPeq/Nm3, and most of it is contributed by 4-6 ring PAHs with high toxic equivalent factors (TEFs). Furthermore, the emission factors of air pollutant emitted from coal-fired boilers equipped with different combinations of APCDs are compiled and compared. The results show that except for CPM and NOx, the emission factors of air pollutant calculated for this coal-fired boiler are lower if compared with other studies.

Environmental occurrence, spatial distribution, and source identification of PAHs in surface and groundwater samples of Abou Ali River-North Lebanon

This paper assesses the concentrations, spatial distribution, compositional patterns, and sources of polycyclic aromatic hydrocarbons (PAHs) in the dissolved aqueous phase along the Abou Ali River course. The 16 priority PAHs, listed by the USEPA, were investigated in surface- and groundwater samples for 2years starting August 2015 and ending in March 2017. Statistical analysis was done by using the ANOVA test at p < 0.05. The spatial distribution analysis and illustration were done using the ARC GIS software. The total PAHs concentration in surface and groundwater samples varied between not detected to 15.162ngmL-1 and not detected to 0.635ngmL-1, respectively. The highest concentration of PAHs in surface water was observed at site S16, downstream of the river. However, the absence of PAHs was noticed at sites S1 and S2 of the upstream. The contamination levels of PAHs were found to be high in surface water samples, and low in groundwater samples. The 5- and 6-ring PAHs were the most abundant species among others in surface water samples, whereas the 3-ring PAHs were the most abundant in groundwater. Pyrogenic inputs deriving from fuel combustion, incineration, and miscellaneous burning were found to be the main PAH sources in surface and groundwater without ignoring the contribution of petrogenic inputs in some areas.

The potential risks and exposure of Qinling giant pandas to polycyclic aromatic hydrocarbon (PAH) pollution

Rapid industrialization and urbanization have created a substantial urban-rural gradient for various pollutants. The Qinling Mountains are highly important in terms of biodiversity, providing habitat for giant pandas, which are endemic to China and are a widely recognized symbol for conservation. Whether polycyclic aromatic hydrocarbon (PAH) exposure risks regarding in situ animal conservation zones are affected by environmental pollution or even enhanced by the mountain-trapping effect requires further research. Our group carried out a large-scale investigation on the area ranging from Xi'an to Hanzhong across the giant panda habitat in the Qinling Mountains by collecting atmosphere, soil, bamboo, and fecal samples from different sites over a two-year period. The total toxicity of atmospheric PAHs and the frequencies of soil PAHs above effect range low (ERL) values showed a decreasing trend from urban areas to the central mountains, suggesting a distance effect from the city. The proportions of total 5- and 6-ring PAHs in the atmosphere were higher in the central mountainous areas than in the urban areas, while this difference was reversed in the soil. Health risk assessments showed that the incremental lifetime carcinogenic risks (ILCR) of PAH exposure by bamboo ingestion ranged from 2.16 × 10−4 to 3.11 × 10−4, above the critical level of 10−4. Bamboo ingestion was the main driver of the PAH exposure risks. The concentration difference between bamboo and fecal samples provided a reference for the level of PAHs absorbed by the panda digestive system. Since the Qinling Mountains possess the highest density of giant pandas and provide habitats to many other endangered animal and plant species, we should not ignore the probability of health risks posed by PAHs. Monitoring the pollution level and reducing the atmospheric emissions of toxic pollutants are recommended actions. Further detailed research should also be implemented on pandas' health effects of contaminant exposure.

Seasonal occurrence, source apportionment, and cancer risk assessment of PAHs in the second largest international holy metropolitan: Mashhad, Iran.

Street dust resuspension is one of the main sources of particulate matter with impacts on air quality, health, and climate. This research was aimed to determine the concentration, source, and health risk of polycyclic aromatic hydrocarbons (PAHs) in street dust of Mashhad city. To this end, USEPA-regulated 16 PAHs were measured in 84 dust samples using gas chromatography coupled to mass spectrometry (GC-MS). The source of Σ16PAHs was identified using diagnostic ratios (DRs), positive matrix factorization (PMF), and principal component analysis (PCA). The measured Σ16PAHs demonstrated different spatial concentrations (from 1,005 to 9,138.96 μg kg-1) and showed higher levels in summer (1,206.21-9,138.96 μg kg-1), although 4-ring PAHs exhibited maximum levels in both summer and winter. The findings revealed that the dust-deposited PAHs are predominantly emitted through combustion of fossil fuels (such as diesel and gasoline) and natural gas. The total incremental lifetime cancer risk (ILCR) was assessed by considering three possible exposure routes separately for children and adults and calculated carcinogenic risk values of 2.24E-06 and 2.14E-06, respectively. ILCR is above the baseline value (1.0E-06) for children and adults in both seasons.

Activation of peroxymonosulfate by nitrogen-doped carbocatalysts derived from brown algal (Sargassum duplicatum) for the degradation of polycyclic aromatic hydrocarbons in marine sediments

A novel nitrogen-enrich biochar carbocatalyst (BAB) was derived from brown algal (Sargassum duplicatum) as precursor by direct pyrolyzation at 300–900 °C. Heteroatom nitrogen doping and the nitrogen functionality of the metal free carbocatalyst activated PMS and produced abundant reactive species (ROSs). BAB and melamine pyrolysis product (N-BAB) effectively activated peroxymonosulfate (PMS) that resulted in the radical and nonradical-based oxidation of 2- to 6-ring polycyclic aromatic hydrocarbons (PAHs). The catalyst N-BAB enabled 86% of PAHs removal in 12 h under optimal conditions ([PMS] = 1 × 10-4 M, [N-BAB] = 3.3 g/L, and pH 3.0), and 56%, 72%, 76%, 82%, and 70% removal of 2-, 3-, 4-, 5-, and 6-ring PAHs, respectively. The graphitization and nitrogen functionalization of biochar matrixes brought about rich defects and edges as radical/singlet oxygen-mediated oxidation sites, which resulted in enhancing the catalytic efficiency during PMS activation for PAHs degradation. The PAHs degradation were faster in N-BAB/PMS (observed rate constant, kobs, rate of 9.8 × 10-2 h-1) than in the BAB/PMS (6.6 × 10-2 h-1) system. Results of electron paramagnetic resonance (EPR) analysis revealed that both radical (SO4•- and HO•) and nonradical (1O2) pathways on the N-functionalized carbocatalyst facilitated PAHs degradation. The results showed also that N-doped biochar exhibited great potential in the remediation of sediment matrices and that the carbocatalyst-PMS process developed in the present study was highly efficient, simple to implement, and cost-effective for providing added value to natural biomass by using advanced biochar activation of PMS.

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

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

Impact of polycyclic aromatic hydrocarbons in mangroves from the Colombian pacific coast: Evaluation in sediments and bivalves

Bivalves and sediments were sampled from mangroves in the Pacific Coast of Colombia to evaluate the concentrations of the 16 polycyclic aromatic hydrocarbons (PAHs) prioritized by U.S.EPA. Mangroves are highly vulnerable to anthropogenic activities, such as oil spills, which affect sediments and the organisms that depend on that ecosystem. Twelve samples of mangrove and non-mangrove (sandy) sediments and 20 samples of Anadara tuberculosa from mangrove were collected in marine and estuarine areas. In sediments and A. tuberculosa, the highest concentration of Ʃ16PAHs was found in estuarine mangroves close to the Rosario River mouth, ranging from 171.4 to 564.0 ng g−1 and 31.0 to 169.0 ng g−1, respectively. For the bivalve, the concentrations showed less variability than sediment, with 25% and 20% of bivalve samples exceeding the limits established by the European Regulatory Commission and Ministry of Health and Social Protection of Colombia, respectively, which can cause effects on people's health. The PAHs isomeric ratios determined in sediments indicated that these compounds were originated mainly from petrogenic sources. The PAHs profile reveals the dominance of 3 and 4 rings PAHs in sediments and dominance of 4 rings PAHs in bivalves.

Foliar Uptake and Accumulation of Polycyclic Aromatic Hydrocarbons from Diesel Emissions

Air pollution in settlements has become a continuously growing problem. Traffic, especially emission of diesel-powered vehicles, poses an important health risk. Emitted particles carry a wide range to potentially toxic chemicals, of them polycyclic aromatic hydrocarbons (PAHs) are the most important group of concern. Despite the risk of air pollution, rural gardens are very popular both for food production and for environmental benefit. On the other hand, several mutagenic and/or carcinogenic PAHs have been detected in leafy vegetables grown in impacted areas. In our study, the No. 227 OECD GUIDELINE FOR THE TESTING OF CHEMICALS: Terrestrial Plant Test: Vegetative Vigor Test was followed to assess foliar uptake of PAHs from aqueous extract of diesel aerosol sample. Significant differences were found in the bioaccumulation capacity of the tested vegetables as well as in their bioaccumulation pattern. In general, most vegetables showed good even strong correlation with individual PAHs of the diesel extract. In consistency with other studies, prevalence of 3- and 4-ring PAHs was experienced.

Bioremediation of polycyclic aromatic hydrocarbons from an aged contaminated agricultural soil using degrading bacteria and soil amendments

The combined effects of degrading bacteria (Paracoccus sp. LXC), humic acid (HA), and soil amendments, including chicken manure, biochar, and wormcast, were investigated through 84 d of incubation in order to improve the remediation of polycyclic aromatic hydrocarbon (PAH) in aged contaminated agricultural soil. PAH concentrations and dissipation kinetics were analyzed, and the biomass and communities of microorganisms and soil enzyme activities were examined to clarify the possible mechanism. The highest removal efficiency of PAHs was 42.1% when treated with Paracoccus sp. LXC combined with biochar and HA. PAH dissipation was consistent with the first-order kinetics model and the half-life of PAHs decreased from 2323.3 d in the natural attenuation to 103–277 d in the amended microcosms. Soil amendments and HA promoted the development of PAH-degrading bacteria and diversity of bacterial communities in soil but not that of fungi. The removal efficiency of PAHs was positively correlated with the density of PAH-degrading bacteria and soil urease (Ure), dehydrogenase (Deh), and manganese-dependent peroxidase (Mnp) activities (r = 0.824–0.941, p < .01). The Paracoccus sp. LXC apparently removed 2–4-ring PAHs, and biochar and wormcast were effective in removing 2–4-ring and 5–6-ring PAHs, respectively. The combined bioremediation strategy using degrading bacteria with soil amendments and HA has high potential for PAH removal in aged contaminated agricultural soil and the possible mechanism was the combination of bioaugmentation with Paracoccus sp. LXC and biostimulation with HA and soil amendments.

Thermal desorption gas chromatography-mass spectrometric analysis of polycyclic aromatic hydrocarbons in atmospheric fine particulate matter

Thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) is used to analyze polycyclic aromatic hydrocarbons (PAHs) in atmospheric fine particulate matter. However, despite the high sensitivity of TD-GC-MS, the recovery rate of PAHs is greatly influenced by active sites in the equipment. PAHs are decomposed or adsorbed at active sites, decreasing quantitative accuracy. Also, the thermal extraction of PAHs is easily affected by the matrix in PM2.5 samples, decreasing the thermal extraction efficiency. Herein, the analytical sensitivities of PAHs were improved by adding analyte protectant (AP) and thermal desorption aid (TDA) as an auxiliary agent. The combination of 2 µL of 0.5 w/v% D-sorbitol (as AP) and 2 µL of 10 w/v% Tween®20 (as TDA) was found to be most effective in improving the analytical sensitivity of PAHs. The sensitivities of 5–6-ring PAHs with high boiling points increased most when analyzing blank filter papers added with PAHs standard sample or real samples of PM2.5 compared with the samples without the auxiliary agent. When analyzing real samples of PM2.5, the peak areas of 5-ring and 6-ring PAHs in the PM2.5 sample added with the optimized auxiliary agent were 1.40 and 1.96 times that without the auxiliary agent. It is considered that AP in the auxiliary agent covered active sites and protected PAHs undergoing decomposition or adsorption. TDA improved the thermal extraction rate of high boiling point PAHs. When using alternative heat sampling equipment to analyze low concentrations of high boiling point components, the auxiliary agent proposed herein can increase the analytical sensitivity toward the target compounds.