Polycyclic Aromatic Hydrocarbons In Soil Samples Research Articles

Polycyclic Aromatic Hydrocarbons Pollution Characteristics in Agricultural Soils of the Pearl River Delta Region, China.

In order to investigate the pollution status of polycyclic aromatic hydrocarbons (PAHs) in the agricultural soil, 240 agricultural soil topsoil samples were collected from nine Pearl River Delta cities from June to September 2019. In addition, 72 samples were collected for vertical soil profiles, which soil profiles were excavated to a depth of 80 cm. After sample preparation, GC-MS was used for the separation of compounds on a HP-5MS quartz capillary column. ArcGIS software was used to map the spatial distribution. Health risk assessment was conducted using USEPA standard. The results showed that the total concentration of 16 PAHs ranged from 43.4 to 5630 ng/g, with an average of 219 ng/g. The spatial distribution showed that most of the seriously polluted areas were in the coastal area, near the port, and there was point source pollution in the Gaoming of Foshan. Vertically distributed display Zhuhai, Jiangmen, Zhaoqing, Shenzhen and Dongguan increased and then decreased from bottom to bottom, showing a low-high-low pattern, the concentration of PAHs in Zhongshan and Foshan decreased with the soil depth, while the concentration of PAHs in Guangzhou and Huizhou was enriched with human activities. The PAHs components in soil samples were mainly medium and high rings (4−6 rings). The analysis of the origin of PAH in soil samples showed that the mixture of incomplete combustion sources of fossil fuels such as coal and biomass and traffic emission sources were the main sources of soil PAHs. A small amount can be attributed to oil sources such as oil spills. The human health risk assessment showed no cancer risk for children, while for adults, may cause a potential risk of cancer, which needs to be noticed. Spearman correlation analysis showed that PAH content was significantly correlated with SOC (p < 0.01) and pH (p < 0.05). Port transport, road emissions and industrial production make the area a pollution hot topic, and supervision should be strengthened to protect the environment and food safety.

The Influence of Crops on the Content of Polycyclic Aromatic Hydrocarbons in Soil Fertilized with Manure and Mineral Fertilizers.

Polycyclic aromatic hydrocarbons (PAHs) are mainly accumulated in soil. Plants secrete enzymes that transform or biodegrade PAHs in soil. Some plant species are more effective in stimulating the biodegradation of these pollutants than other species. This study was undertaken to evaluate the influence of crop rotation on PAH concentrations in soil. Four crops were grown in rotation: sugar beets, spring barley, maize, and spring wheat. Soil samples for the study were obtained from a long-term field experiment established in 1986 in Bałcyny, Poland. The concentrations of PAHs were analyzed in soil samples gathered over a period of 12 years (1998–2009). An attempt was made to evaluate the effect of crop rotation (sugar beets, spring barley, maize, and spring wheat) on PAH concentrations in soil. The content of PAHs in soil samples was measured by gas chromatography with flame ionization detection. Data were processed statistically by repeated measures ANOVA. The concentrations of ∑16 PAHs were lowest in soil after sugar beet cultivation, and highest in soil after maize cultivation. It can be concluded that maize was the plant with the greatest adverse effect on the content of heavy PAH in the soil, a completely different effect can be attributed to spring wheat, which has always been shown to reduce the content of heavy PAH in the soil. Weather conditions affected PAHs levels in soil, and PAH content was highest in soil samples collected in a year with the driest growing season. This arrangement suggests a greater influence of weather conditions than of the cultivated plant.

Levels, source apportionment, and risk assessment of polycyclic aromatic hydrocarbons in vegetable bases of northwest China.

Dietary consumption of contaminated vegetables is the main route of human exposure to polycyclic aromatic hydrocarbons (PAHs). However, there is a lack of research on PAHs in vegetables from northwest China. In this study, the concentrations, sources, and risk assessment of PAHs in the soil and vegetables of Urumqi, an urbanized city in Xinjiang, China, were investigated. The total concentrations of 16 PAHs in soil and vegetable samples ranged 10.58-77.20 and 93.7-1071.8ng/g, with average values of 2.86 and 242.76ng/g, respectively. Among vegetable samples, the concentrations were in the order: leafy vegetables (299.08ng/g) > fruits (192.65ng/g) > vegetable roots (152.05ng/g). The source apportionment of PAHs was identified using positive matrix factorization. The primary sources of PAHs in soil samples are oil spills, traffic emissions, coal combustion, and coke combustion. The main sources of PAHs in vegetable samples are oil spills and burning of grass, wood, coal, and coke. In soil samples, the ecological risk caused by PAHs is at a safe level, and the incremental lifetime cancer risks (ILCRs) of ingestion exposure exceed 1.0 × 10-6, which will pose potential risks to human body. The ILCRs of vegetable samples revealed that all groups had potential risks from onion and cabbage consumption (ILCRs > 1.0 × 10-6). In particular, adult women had a higher risk of cancer (ILCRs > 1.0 × 10-4). These results emphasize the importance of combating PAHs pollution in vegetable bases.

The accumulation of polycyclic aromatic hydrocarbons in snails and soil in Igbekebo, Ondo State, Nigeria

Polycyclic Aromatic Hydrocarbons (PAHs) are harmful to human health and can cause cancer. The PAHs concentration in soil and snail samples collected from the Igbekebo region of Ondo state was measured in this study. Using metal spoons, soil samples were taken from five separate sites and placed in foil paper bags at a depth of 10 cm. For each type of snail under study, eight (8) samples were randomly taken from five distinct locations. Gas chromatography flame ionization detector (GC-FID) was used to analyze the samples. The estimated daily intake (EDI) and bioaccumulation factor (BAF) in the snail samples, as well as the toxic equivalence quotient (TEQ) and mutagenicity equivalence quotient (MEQ) in the soil samples, were calculated. This study showed that concentration levels of PAHs in soil, freshwater snail (Bulinus globosus), and land snail (Achatina marginata) samples were within the range of 0.1894–48.8063 μgkg−1, 0.15–40.14 μgkg−1, and 0.56–60.79 μgkg−1 respectively. Dibenzo(a,h)anthracene, anthracene, and Dibenzo(a,h)anthracene, respectively, were the most common PAHs found in soil, freshwater snails, and land snails. The total PAHs concentration in freshwater snail sample was lower when compared to other studies. The toxicity of each PAH in the soil sample was determined using Toxic Equivalent Factor (TEF) and Mutagenic Equivalent Factor (MEF) values, and the results were compared to the National Institute for Public Health and the Environment’s (Dutch: Rijksinstuut voor Volksgezondheid en Milieu (RIVM)) toxicity limits. It is advised to restrict crop and land snail consumption in Igbekebo since the soil samples from Igbekebo had a higher PAH toxicity value than the RIVM toxicity limit.

Polycyclic Aromatic Hydrocarbons: Evaluation of concentrations in environmental media in Bayelsa State

Background and aim Artisanal refining of crude oil is an illegal refining process that contributes to environmental pollution through the release of Polycyclic Aromatic Hydrocarbons (PAHs). PAHs compounds are known for their destructive effects on the environment as well as their harmful effects on human health. This study thus assessed the concentrations of PAHs in water, soil, and fish in communities where artisanal refining of crude oil is practiced in Bayelsa State. Materials and methods This descriptive, comparative study was conducted in Sampou (mildly exposed community), Gbarain, and Nembe (severely exposed communities) in Bayelsa State. Water, fish, and soil samples were collected using pre-existing environmental media collection guidelines and sent to the laboratory for GC-FID determination of the PAH concentrations. The data obtained were analyzed using the Statistical Package for Social Sciences (SPSS) software. Results Mean and (total) PAHs concentration in water samples obtained from Sampou was 3.50 ± 4.51 (59.59) μg/L; Gbarain 1.76 ± 4.35 (29.87) μg/L and Nembe 1.90 ± 4.20 (32.25) μg/L. A significant difference in the concentrations was also identified p-value: of 0.021. The mean concentration of PAHs in soil samples obtained from Sampou was 10.73 ± 15.53 (183.38) μg/kg; Gbarain 12.00 ± 19.57 (204.32) μg/kg and Nembe was 8.49 ± 10.07 (144.48) μg/kg. Finally, the mean concentration in fish samples obtained from Sampou was 5.62 ± 5.92 (95.43) μg/kg; Gbarain 3.81 ± 5.57 (64.75) μg/kg and Nembe 4.61 ± 5.33 (78.35) μg/kg. The difference in these concentrations was however not significant. Source diagnostic ratios of the PAHs in the water included Flt/(Flt + Pyr) ratio of 0.23, 0.16, and 0.21; Ant/(Ant + Phe) ratio of 0.87, 0.76, and 0.87 as well as BaA/(BaA + Chr) ratio of 0.43, 0.51 and 0.66 in Sampou, Gbarain and Nembe respectively. Conclusion Concentrations of total PAHs in water and fish samples obtained from the three communities exceeded the acceptable limits for ƩPAHs of 2.0 μg/L and 2 μg/kg in water and fish respectively stipulated by the United States Environmental Protection Agency and the Nigerian Petroleum Regulatory Authority. ƩPAHs concentrations from the samples obtained from Sampou were also higher than the other two communities. There is a need for regular environmental monitoring of PAH concentrations, especially in oil-producing communities, and a shift of focus toward the elimination of pyrolytic sources of PAH pollution.

Covalent organic framework derived porous carbon as effective coating for solid phase microextraction of polycyclic aromatic hydrocarbons prior to gas-chromatography mass spectrometry analysis

In this work, covalent organic frameworks (COF) derived porous carbon was prepared through employing TpPa-1 as self-sacrificed template and used as solid phase microextraction (SPME) fiber coating. Owing to the high specific surface area and uniform pore size distribution, the resulting porous carbon exhibited excellent extraction ability toward PAHs. Coupled with gas-chromatography mass spectrometry (GC–MS), direct immersion SPME based on the resulting porous carbon was applied for analyzing eight polycyclic aromatic hydrocarbons (PAHs). Under the optimal conditions, the developed method exhibited a wide linear range for PAHs (30–30,000 μg kg−1) along with low limits of detection (LODs, 3.12–8.55 μg kg−1) and limits of quantification (LOQs, 10.4–28.5 μg kg−1). Moreover, the proposed method exhibited high reliability in its application on the determination of PAHs in soil samples, highlighting the application potential of COF derived porous carbons in monitoring aromatic pollutants in the environmental samples.

Pollution and Risk Assessment of Polycyclic Aromatic Hydrocarbons (Pahs) in Agricultural Soil along a Highway of Jilin Province, China

ABSTRACT The agricultural area adjacent to highways experienced high threat ofpersistent organic pollutants (POPs), which are fromvehicle exhaust, asphalt, and tyre wear.To analyze the presence, distribution patterns, ecological risk and sources of polycyclic aromatic hydrocarbons (PAHs), soil samples were collected in farmland along a highway in Jilin province, China and analyzed for 16 PAHs. The concentration of ∑16PAHs in soil at traffic sites ranged from 781.83-3659.21 ng/g dry weight with the mean value of 2263.78 ng/g, respectively.The PAHs patterns were generally dominated by the high molecular weight (HMW) PAHs, which represented about 65.82% of the total PAHs in traffic sites and 53.52% in control sites of the total 16 PAHs in soil samples. The sources of PAHs in soilwere mainly contaminated by mixed petroleum and combustion. Ecological risk assessment indicated that there were18.33% of the soil samples belong to Moderate-risk 2, and 81.67% of soil samples belong to High-risk. Through the diagnostic ratio analysis, some clean-up measures should be consideredto mitigate local food production risks.

Ingestion and Dermal Cancer Risk via Exposure to Polycyclic Aromatic Hydrocarbon-Contaminated Soils in an Oil-Producing Community, Niger Delta, Nigeria.

There is an intrinsic link between polycyclic aromatic hydrocarbons (PAHs) accumulated in soils and increased health risk to humans after exposure to contaminated soil via ingestion, inhalation of particulates carrying PAHs, and direct contact with polluted soils. However, the assessment of PAH contamination in most developing countries fails to consider health risk assessment. Therefore, a comprehensive study was conducted to determine the concentration, source, toxicity, and human health risks of 16 PAHs in an urban area in Warri, Delta State, in the Niger Delta region of Nigeria. The results showed varying contamination levels for PAH in soil samples from all sampling points, with benzo[a]anthracene (BaP; at 338.81 μg/kg) being the most abundant at all 9 sampling stations. The highest total concentration of PAH was observed at station 5 (1230.98 μg/kg), which was closest to a flow station. Further comparison with PAH contamination standards showed that soils from stations 1 and 2 were weakly contaminated (<600 μg/kg), and soil samples from stations 3, 4, 6, 7, and 9 were moderately contaminated (<1000 μg/kg). Soil samples from stations 5 and 8 were observed to be heavily contaminated (>1000 μg/kg). The BaP estimates for soil samples obtained for stations 3 to 9 were higher than the BaP soil screening value (15 μg/kg), indicating a carcinogenic potential of soil samples. The results also showed that the incremental lifetime cancer risk estimates for PAH in the soil for adults and children were above the recommended threshold (10-4 ) for ingestion and dermal contact, implying that exposure to contaminated soil could lead to cancers in adults and children. Currently, there are no regional or national standards for PAHs in soil that would indicate an increased likelihood for human exposure and subsequent health issues. Environ Toxicol Chem 2021;40:261-271. © 2020 SETAC.

Assessment of Polycyclic Aromatic Hydrocarbons in Agricultural Soils of Teskelewu Community and Environs Impacted By Gas Flaring in Delta State, Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are emerging ubiquitous environmental pollutants with reported carcinogenic, mutagenic and teratogenic potentials on living organisms and humans. The objective of this study was to assess the concentrations of PAHs in agricultural soils of Tsekelewu Community and environs (Egbema Kingdom) in Warri North Local Government Area of Delta State, Nigeria impacted by gas flaring using gas chromatograph system Agilent 5890 Series 11 gas chromatograph equipped with Flame ionization detector (GC-FID). The results revealed that station 1 and 2 were fairly contaminated; with mean total PAH concentration of 236.40 μg/kg and 279.75 μg/kg respectively. Stations 3, 4, 6, 7 and 9 having mean total PAH concentration of 692.45μg/kg, 726.22 μg/kg, 739.82 μg/kg, 609.38 μg/kg, and 772.99 μg/kg were moderately contaminated. Heavy contamination was recorded in station 5 and station 8 with mean PAH concentrations of 1231.08μg/kg and 1224.33 μg/kg. The dominant PAHs in soil samples were benzo(a)anthracene, phananthrene and chrysene with benzo(a)anthracene having the highest concentration across all sample stations. The PAH concentration observed in this study is thus a serious cause for concern since soil contamination from gas flaring will likely continue. Measures that will attenuate PAHs concentrations in soil should be adopted as farmers are likely exposed by largely inhalation.Keywords: Hydrocarbons; Contamination; Agricultural soils; Gas flaring

Distribution of selected polycyclic aromatic hydrocarbons in urban soils of Delhi, India

Abstract Selected polycyclic aromatic hydrocarbons (PAHs) including naphthalene, fluorene, phenanthrene, anthracene (low molecular weight) and fluoranthene, pyrene, benzo[a]pyrene (high molecular weight) were analysed in urban soil samples. Benzo[a]pyrene is considered as an environmental toxicity indicator. The samples were collected from different locations of megacity Delhi during pre- and post-winter seasons. Qualitative and quantitative determination of PAHs in soil samples was performed using high performance liquid chromatography with UV detection (HPLC-UV). The sum of selected PAHs ( ∑ 7 PAHs) in soils of polluted sites ranged from 956 μ g kg − 1 to 2348 μ g kg−1 (average 1714 μ g kg−1) in pre-winter season and 1230 μ g kg−1 to 2714 μ g kg−1 (average 1909 μ g kg−1) in post-winter season. The PAHs content in the post-winter samples was higher than the pre-winter samples. Organic carbon content does not show significant correlation with ∑ 7 PAHs. Sites with high potential environmental risk were identified using hierarchical cluster analysis.

Analysis of polycyclic aromatic hydrocarbons (PAHs) and their polar derivatives in soils of an industrial heritage city of Australia

Knowledge about polar derivatives of polycyclic aromatic hydrocarbons (PAHs) in soils is limited despite the extensive study of the environmental presence and persistence of non-polar parent PAHs. Polar PAHs have greater potential to be more toxic at low environmental concentrations compared to their homocyclic analogues. For both polar and non-polar PAHs, combustion of fossil fuels is often the main source especially in industrialised environments. This study investigated the concentration profiles of PAHs and its associated polar PAHs such as nitrated PAHs (NPAHs), oxygenated PAHs (oxy-PAHs) and nitrogen, sulphur and oxygen heterocyclic PAHs (N/S/O-heterocyclic PAHs) in a well-known industrial heritage city of Australia. The most abundant polar PAHs were 9-fluorenone (oxy-PAHs), 2-nitrofluorene (NPAHs) and carbazole (heterocyclic-PAHs). A positive correlation (r = 0.5, p < 0.01) between ∑13PAHs and ∑19 polar PAHs was observed, implying a possible spatial association between parent and polar PAHs. The concentrations of polar PAHs in soil samples, across various landuse patterns, were used to calculate the excess lifetime cancer risk (ELCR) from incidental ingestion of soils. The computed ELCR values ranged from 8.2*10−7 (industrial soils) to 2.3*10−6 (residential soils), indicating negligible cancer risks. This is the first known study on the occurrence and concentrations of polar and non-polar PAHs in any Australian city, and the results may serve a baseline purpose for improved risk assessment of contaminated sites.

Characteristics, sources, and in situ phytoremediation of polycyclic aromatic hydrocarbon in rural dumpsites

Without precaution to deal with gas emissions and leachate generation, dumpsites have become a severe environmental problem in many developing countries. The objectives of this study were to investigate the pollution status of polycyclic aromatic hydrocarbons (PAHs) in dumpsite soil in rural areas of China and to verify phytoremediation effectiveness with Sedum alfredii Hance and alfalfa (Medicago sativa L.) under complex pollution conditions in PAH-contaminated soil. In this study, we collected soil cores from four dumpsites in rural areas of North China (Hebei Province) for analysis, and correspondingly conducted an in situ phytoremediation experiment using Sedum alfredii Hance and alfalfa (Medicago sativa L.) at one of these sites, monitoring the total PAH concentration in soil. Results showed generally moderate pollution by PAHs in soil samples from dumpsites with pockets of heavy pollution. PAH concentrations in dumpsite soil ranged from 827 to 1101 ng/g (dry weight). High-molecular-weight PAHs were present in higher proportions at oldest dumpsite in operation. Certain molecular ratios of PAHs can be used to diagnose the source of PAHs in soil, and it indicated that the main sources were combustion of domestic coal and biomass, as well as the automobile exhaust and kitchen exhaust. A 17-month in situ phytoremediation experiment resulted in the effective removal of PAHs in the Sedum alfredii and alfalfa plots, with total PAH concentrations decreasing by 82.4% and 81.3%, respectively. Furthermore, PAH concentrations in plants correlated to plant growth conditions. This study indicated that the soils of the dumpsites were generally moderately polluted by PAHs, and some parts of the area were heavily polluted. Both Sedum alfredii and alfalfa absorbed PAHs from soil, and PAH concentrations in these two plants correlated to the growth conditions of the plants. Phytoremediation can effectively be used for PAH removal in open dumpsites.

Impact of Lebanese practices in industry, agriculture and urbanization on soil toxicity. Evaluation of the Polycyclic Aromatic Hydrocarbons (PAHs) levels in soil

This study was carried out in order to investigate the toxicity on Lebanese soil and to show the impact of the anthropogenic activities, industrialization and urbanization, on the release of Polycyclic Aromatic Hydrocarbons (PAHs) in Lebanese soils. Hundred soil samples of different land use were screened for 17 PAHs using a UAE/GC-MS method. Detection frequency varied between 76 and 100% for most of the PAHs, where the ΣPAHs ranged from 33.5 to 4062.9 ng g−1. Moreover, BaPeq values varied between 0.93 and 332.4 ng g−1. BaPeq values in industrial and urban soils were 777 and 256 times higher than those in rural soil, respectively. None of the soil samples showed concentrations above the safe BaPeq value of 600 ng g−1. Significant decrease in concentration levels of ΣPAHs was obtained in the following order: Industrial, urban, traffic and agricultural. Furthermore, the relative high contribution of Chrysene, Benzo(a)Anthracene and Benzo(k)Fluoranthene in agricultural soils indicates that open burning remains an adopted way in Lebanon for disposal of agricultural residues, while the predominance of Benzo(ghi)Perylene and Benzo(b)Fluoranthene in industrial soils suggests the broad use of diesel powered engines in the Lebanese industrial sector. The ratios of Low Molecular Weight/High Molecular Weight and fluoranthene/fluoranthene+pyrene (Fln/Fln+Pyr) showed that PAHs in soil samples are mainly pyrogenic and created during combustion of petrol, coal, wood and other biomasses.

Characterization, source apportionment, and risk assessment of polycyclic aromatic hydrocarbons in urban soil of Nanjing, China

Polycyclic aromatic hydrocarbons (PAHs) are widespread in the urban environment, particularly in urban soil, which are affected by intensive human activities. The purpose of this study was to determine the levels of PAHs in urban areas of Nanjing, China, apportion their sources, and evaluate their health risk. One hundred eighty topsoil samples (0–10 cm) were collected from 180 grids of 1 km × 1 km in the main urban area of Nanjing, China, which was divided into four different land use classes. All the soil samples were analyzed for 16 US Environmental Protection Agency (US EPA) priority PAHs by HPLC. Source of PAHs was explained by isomer ratios and principal component analysis, and health risk of PAHs was assessed by benzo[a]pyrene (BaP) toxic equivalency factors. The average concentration of PAHs ranged from 41.19 to 7016.65 μg kg−1, with an average of 979.59 μg kg−1. PAHs in soil characterized by different land uses, in decreasing order, were as follows: university (UN) > traffic area (TA) > forest park (FP) > residential area (RA). PAHs in FP soils were mainly attributed to biomass combustion, while TA soils exhibited clear traffic emission characteristics. PAHs for UN and RA came from mixed sources. A principle component analysis (PCA) and ordinary kriging map indicated coal combustion and vehicle emissions as the major contributors to PAHs in Nanjing urban soils, respectively. A health risk assessment based on the BaP toxic equivalency approach indicated a potential risk level of PAHs. The mean value of PAH concentrations in UN was the highest. However, the maximum was detected in TA. The PAHs in soil samples originated mainly from coal combustion and petroleum combustion sources. There was a potential health risk level of PAHs in Nanjing urban areas.

Study of polycyclic aromatic hydrocarbons (PAHs) in soil samples from Al-Ahdab oil field in Waset Region, Iraq

Levels of thirteen polycyclic aromatic hydrocarbons (PAHs) were studied in 24 soil samples collected from the Ahdab oil field in Waset region, Iraq. The whole analysis was carried out using the gas chromatography with mass spectrometry (GC/MS) in the single ion monitoring (SIM)-mode. The total PAHs concentrations were ranged between 19 μg/kg (Site 15) and 855 μg/kg (Site of 16). The results of these samples were compared among each other according to their toxicity equivalence in μg TEQ/g concentrations and with the results of other studies. The total estimated cancer risks of exposure to PAHs in soil samples were ranged from 1.02 × 10−7 to 4.59 × 10−6. By multiplying the estimated cancer risk values by 106, then the estimated theoretical cancer cases per million is between 0.0 and 5. The total estimated cancer risks in this study were within the acceptable range of excess cancer risk specified by the Environmental Protection Agency in the United States.

Spatio-temporal variations and influencing factors of polycyclic aromatic hydrocarbons in atmospheric bulk deposition along a plain-mountain transect in western China

Ten atmospheric bulk deposition (the sum of wet and dry deposition) samplers for polycyclic aromatic hydrocarbons (PAHs) were deployed at a plain-mountain transect (namely PMT transect, from Daying to Qingping) in Chengdu Plain, West China from June 2007 to June 2008 in four consecutive seasons (about every three months). The bulk deposition fluxes of ∑15-PAHs ranged from 169.19 μg m−2 yr−1 to 978.58 μg m−2 yr−1 with geometric mean of 354.22 μg m−2 yr−1. The most prevalent PAHs were 4-ring (39.65%) and 3-ring (35.56%) PAHs. The flux values were comparable to those in rural areas. Higher fluxes of total PAHs were observed in the middle of PMT transect (SL, YX and JY, which were more urbanized than other sites). The seasonal deposition fluxes in the sampling profile indicated seasonality of the contaminant source was an important factor in controlling deposition fluxes. PAHs bulk deposition was negatively correlated with meteorological parameters (temperature, wind speed, humidity, and precipitation). No significant correlations between soil concentrations and atmospheric deposition were found along this transect. PAHs in soil samples had combined sources of coal, wood and petroleum combustion, while a simple source of coal, wood and grass combustion for bulk deposition. There were significant positive correlation relationship (p < 0.05) between annual atmospheric bulk deposition and local PAHs emission, with biomass burning as the major contribution to the total emission of PAHs. This transect acts as an important PAHs source rather than being a sink according to the ratio of deposition/emission. Mountain cold trap effect existed in this transect where the altitude was higher than 1000 m. Long-range transport had an impact on the bulk deposition in summer. And this transect was a source to Tibetan only in summer. The forward trajectory analysis showed most air masses did not undergo long-range transport due to the blocking effect of surrounding mountains. Only a few air masses (<10%) arrived at the eastern and northern region of China or farther regions via long-range transport.

A quantitative PCR approach for quantification of functional genes involved in the degradation of polycyclic aromatic hydrocarbons in contaminated soils

Polycyclic aromatic hydrocarbons (PAHs) are major pollutants globally and due to their carcinogenic and mutagenic properties their clean-up is paramount. Bioremediation or using PAH degrading microorganisms (mainly bacteria) to degrade the pollutants represents cheap, effective methods. These PAH degraders harbor functional genes which help microorganisms use PAHs as source of food and energy. Most probable number (MPN) and plate counting methods are widely used for counting PAHs degraders; however, as culture based methods only count a small fraction (<1%) of microorganisms capable of carrying out PAH degradation, the use of culture-independent methodologies is desirable.•This protocol presents a robust, rapid and sensitive qPCR method for the quantification of the functional genes involved in the degradation of PAHs in soil samples.•This protocol enables us to screen a vast number of PAH contaminated soil samples in few hours.•This protocol provides valuable information about the natural attenuation potential of contaminated soil and can be used to monitor the bioremediation process.

Optimization of a large-volume injection method for compound-specific isotope analysis of polycyclic aromatic compounds at trace concentrations.

Compound-specific isotope analysis (CSIA) of persistent organic contaminants can be used for source apportioning in the environment if appropriate sensitivity can be achieved. This paper describes the optimization and validation of a sensitive analytical approach for the determination of the carbon isotope composition of semi-volatile organic compounds, such as polycyclic aromatic hydrocarbons (PAHs). Analyses are based on the introduction of up to 150 μL of organic extracts by means of programmed temperature vaporization-large-volume injection combined with gas chromatography coupled to isotope ratio mass spectrometry (PTV-LVI-GC/IRMS). To allow for the analysis of more volatile, low-molecular-weight PAHs, the PTV injector was equipped with a sub-ambient/cryogenic cooling. Accuracy, precision, linearity and determination limits for application in isotope analysis were evaluated for a set of individual PAHs ranging from two- to five-ring molecular structures. The method was exemplified by determining the δ(13) C values of individual PAHs in soil samples in a source apportionment study at a contaminated site. The choice of PTV injection parameters is crucial to prevent isotope fractionation during injection and largely depends on the analytes to be determined. The observed isotope fractionation effect on semi-volatiles depends on the applied solvent and injection temperature and demonstrates the importance of performing appropriate tests with given PTV parameters for each of the compounds of interest. The proposed PTV-LVI-GC/IRMS method allows the carbon isotope ratio (δ(13) C value) of individual PAHs to be determined accurately and precisely at concentrations of 0.04-0.1 ng μL(-1) even for volatile PAHs such as naphthalene or acenaphthene. LVI with PTV injector cooling allows for the isotopic analysis of volatile and semi-volatile PAHs at trace concentrations, thus considerably expanding the applicability of CSIA in environmental studies.

GC/MS Monitoring of Selected PAHs in Soil Samples Using Ultrasound-assisted QuEChERS in Tandem with Dispersive Liquid-Liquid Microextraction

Herein, a method consisting of ultrasound-assisted QuEChERS in tandem with dispersive liquid-liquid microextraction (DLLME) was developed for monitoring of selected polycyclic aromatic hydrocarbons (PAHs) in various soil samples using gas chromatography coupled to a single quadrupole mass spectrometry (GC/MS). Ultrasound-assisted QuEChERS was employed to extract the PAHs from 2.0 g of soil using 7 ml of initial extraction solvent (acetonitrile: water (5:2 v/v)) and the salt mixture. The resulting supernatant extract was cleaned through the addition of C18, PSA and the mix salt followed by centrifugation, decantation and filtration. Of the clean organic phase, 1.0 ml was withdrawn and added with12 µl of C2Cl4 (disperser solvent). The resulting mixture was then injected rapidly into an aqueous sample (5.0 ml) by a syringe for further preconcentration. As a result, the cloudy solution consisting of fine particles of the extraction solvent dispersed into the aqueous phase was formed. After centrifuging, the fine particles were sedimented at the bottom of the conical test tube (5.0 ± 0.5µl). Of which, 1.0 µl was injected to the GC/MS for monitoring of the PAHs. Several influential parameters including ultrasound extraction time, initial extraction and disperser solvent and their respective volumes were all evaluated to achieve the optimal conditions. Under the optimal conditions, limits of quantification (2.5-4.0 ng/g) and linear ranges (r2≥ 0.98) were obtained for the PAHs. The method was then successfully applied for the extraction and monitoring of the PAHs in the real soil samples. Accuracy of the method was evaluated by the relative recovery experiments on spiked samples with the results ranging from 81 to 92%. In the mean time, the relative standard deviations (RSDs) were found to be in the range of 4.8–15.9%.

Modification of sol-gel hybrid monolith and its application in determination of polycyclic aromatic hydrocarbons

A C6-silica hybrid monolithic column was prepared by click reaction with capillary silica monolith. Firstly, an azide-functionalized silica monolithic column was synthesized via sol-gel reaction with tetramethoxysilane (TMOS) and 3-azidopropyltrimethoxysilane (N3PTMS). Then 1-hexyne was covalently immobilized on the capillary monolith by the "azide-alkyne" click reaction to form C6-silica hybrid monolithic column. As an extraction media of polycyclic aromatic hydrocarbons (PAHs), the conditions for the preparation and modification of the monolith were carefully investigated according to the extraction efficiency. The enrichment factors for typical PAHs: naphthalene, phenanthrene, pyrene and benzo a pyrene finally reached 95.9, 14.2, 103.2 and 57.8, respectively. The relative standard deviations (RSDs) for the extraction were lower than 5.5% (intra-day, t = 8) and 7.3% (inter-day, n = 10). Based on the in-tube solid phase microextraction (in-tube SPME), a new determination method for 16 PAHs was developed with high performance liquid chromatography (HPLC). The limits of detection (LODs, SN = 3) were 0.08-3.72 µg/L and the limits of quantification (LOQs, S/N = 10) were 0.26-12.40 µg/L for the PAHs. The spiked recoveries for the PAHs in soil samples were between 82.4% and 110.6% with the RSDs (n = 3) of 2.6%-7.9%. Comparison with the method of United States Environmental Protection Agency (U. S. EPA) for the PAIs determination in soil samples, the results showed good accuracy and high consistency. And the high extraction efficiency with high sensitivity and convenience was also demonstrated in the applications of the new approach.