Polycyclic Aromatic Hydrocarbons Concentrations In Soil Research Articles

Nitrogen input leads to the differential accumulation of polycyclic aromatic hydrocarbons in the low- and high-density fractions in sewage-irrigated farmland soil

Because of a shortage of water resources, sewage irrigation has become a popular management tool for farmland soil in arid areas of China; however, this has led to the accumulation of polycyclic aromatic hydrocarbons (PAHs) in soil. Soil is an important component of ecosystems, and nitrogen is an important nutrient required for plant growth. Nitrogen input can alter the physical, chemical, and biological processes in soil and thus lead to changes in soil organic matter and organic pollutants. However, whether these changes affect the accumulation of PAHs and whether such accumulation differs in the low-density fraction (LF) and high-density fraction (HF) of soil remains unclear. In this study, the response of PAHs in soil to nitrogen input (0, 100, 200, and 300 kg N ha−1 yr−1, respectively), including differences in LF and HF, were investigated through field experiments in a typical sewage-irrigated area. The results showed that nitrogen input could increase the concentrations of PAHs in soil from (7.6 ± 1.1) × 103 to (10.4 ± 0.6) × 103 μg kg−1 and lead to striking differences between the LF ((5.06 ± 0.75) × 103 to (1.89 ± 0.18) × 103 μg kg−1) and HF ((2.54 ± 0.36) × 103 to (8.54 ± 0.44) × 103 μg kg−1). Given the significant increase in global nitrogen input, our findings have implications for the optimization and management of agricultural activities in sewage irrigation areas, such as soil investigation before fertilization, the use of soil improvers, and the improvement of soil planting measures.

Profiling and assessing soil-air exchange of polycyclic aromatic hydrocarbons (PAHs) in playground dust and soil using ex situ equilibrium passive sampling

Cancer risk can be associated with exposure to polycyclic aromatic hydrocarbons (PAHs) in playground dust and soil. This study investigated the profiles and sources of PAHs from poured rubber-surfaced playground dust and uncovered playground surface soil, by applying an ex-situ equilibrium passive sampling technique. Surface dust and soil samples were collected from 15 different playgrounds in Seoul, Republic of Korea. The total 16 EPA PAHs concentrations in surface dust and soil varied from 198 to 919 μg kg−1 dw and 68–169 μg kg−1 dw, respectively. 4- to 6-ring PAHs were dominant, accounting for approximately 53.8%–94.5% of the total PAHs in surface dust and soil. The diagnostic ratios and principal component analysis suggested that a mixed coal combustion and vehicular emission was likely the main source of PAHs in the surface dust and soil. The higher total organic carbon content can explain the higher PAH accumulation and lower fugacities of PAHs. The fugacity comparison of phenanthrene and pyrene in dust, soil, air, and playground surface material indicated that atmospheric deposition is the main source of PAHs in the dust and soil on rubber-surfaced and uncovered surfaced playgrounds. This study contributes to the understanding of PAHs sources in dust and soil samples in children's playground and helps policymaker determine the right contamination sources for risk management.

Sixteen priority polycyclic aromatic hydrocarbons in roadside soils at traffic light intersections (Bratislava, Slovakia): concentrations, sources and influencing factors.

Combustion of fossil fuels is the most important source of polycyclic aromatic hydrocarbons (PAHs) in the environment. Cities are typical of many human activities which are dependent on fossil fuels (road and railway transport, heat generation, waste incineration and industry) on a small area, leading to high concentrations of PAHs in urban air, dust and soil. The aim of this study was to determine the possible influence of urban traffic on the accumulation of sixteen priority PAHs in soils (n = 132 at two soil depths of 0-10cm and 10-20cm) taken at intersections (n = 37) with different traffic volumes and road ages. Variable concentrations of the sum of PAHs (∑16PAH) ranging from 188 to 21,950μg/kg with a mean and median of 3021μg/kg and 1930μg/kg were recorded, respectively. Concentrations of PAHs positively correlated with soil organic carbon content (TOC) (rSpearman = 0.518; p <0.001). Statistically significant positive correlations between ∑16PAH concentrations and traffic volume/road age were found in this study (rSpearman = 0.689/0.619; p <0.001), while ∑16PAH concentration decreased with increasing distance from the road edge and was statistically lower at a soil depth of 10-20cm than at 0-10cm (p <0.05). Multivariate statistical methods (principal component analysis and cluster analysis) applied to log-ratio transformed data (clr) to decrease the constant sum constraint coupled with positive matrix factorisation (PMF) modelling pointed to the dominance of pyrogenic emission sources, with 62.1% traffic-related (petrol and diesel emissions, liquid fuel and motor oil spills, and tyre wear) according to PMF results.

Spatial and seasonal variations of PAHs in soil, air, and atmospheric bulk deposition along the plain to mountain transect in Hubei province, central China: Air-soil exchange and long-range atmospheric transport

Polycyclic aromatic hydrocarbons (PAHs) are a long-term environmental problem faced by human society. The sources of involuntary PAHs are complex, moreover, secondary emissions of fixed PAHs in the environment occur due to global change and disturbance of human activities. Samples of three environmental media including soil, air, and atmospheric bulk deposition were collected to observe the spatial distribution and seasonal variation, to discuss the source or sink of PAHs and their association with the air mass transport along the plain (Jianghan Plain, JHP) to mountain transect, and explore the geographic scope of the atmospheric transport influence. The results obtained showed that 16 individual PAHs generally existed in all environmental multimedia being studied, and the PAHs concentration in air, soil and deposition flux of atmospheric bulk was higher in JPH than in “Western Hubei Mountains” (WHMs). Considerably high PAHs concentrations were obtained from the soil, air and atmospheric bulk deposition in winter, summer, and both summer and winter, respectively. The air-soil fugacity fraction of PAHs indicated that the soil of Dajiuhu (DJH) is likely to be a sink. Backward air trajectory simulation confirmed that most of the air mass passes over the JHP before reaching DJH, combined with the (transport and persistence level III) TaPL3 model results JHP are acting as sources. However, seasonal changes lead to a shift in the roles of soil sources and sinks. The TaPL3 model calculated that PAHs are transported through water for a wider range of effects and a longer persistence, even up to 10 years.

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

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

Incorporating Oil / Water Partitioning in Risk Calculations for PAHs in Petroleum Impacted Soils and Sediments

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) may drive remediation at impacted soil or sediment sites. Current equations for calculating the PAH concentrations in soil that are protective of underlying groundwater (i.e., soil screening levels, or SSLs) generally assume a three-phase partitioning model, wherein PAHs partition among the soil matrix, porewater, and pore air. This simplified model does not consider the oil phase, and therefore overestimates the dissolved PAH concentration, and consequently, overpredicts the mobility and toxicity of PAHs to receptors especially when the source of PAHs is oil. This results in unnecessarily stringent cleanup goals and adds to the cost of treatment and management of impacted soils. Complicating factors leading to the overestimation of dissolved PAH are that oil weathering (1) decreases to the effective solubility of the lower molecular weight PAHs, and (2) the presence of the oil itself increases PAH retention in the oil phase, thereby reducing aqueous/dissolved PAH concentrations. This is particularly important when oil is both the source and the factor controlling its solubility. In this paper, we have incorporated additional partitioning factors into existing SSL equations to capture the impact of oil weathering on PAH partitioning: The oil-water partitioning coefficient (KOIL ) for crude oils was measured at different stages of weathering using a passive sampling device (PSD). Results confirm that current methods for deriving SSLs are highly conservative and that the aqueous concentrations and mobility of PAHs are lower in soils and sediments that contain weathered oils. Thus, the mobility of PAHs in historically impacted soils is much lower than what is assumed when calculating SSLs for soil-leaching-to-groundwater scenarios.

Oral and Dermal Bioavailability Studies of Polycyclic Aromatic Hydrocarbons from Soils Containing Weathered Fragments of Clay Shooting Targets.

The relative oral bioavailability and dermal absorption of chemical substances from environmental media are key factors that are needed to accurately estimate site-specific risks and manage human exposures. This study evaluated the in vivo relative oral bioavailability and in vitro dermal absorption of several polycyclic aromatic hydrocarbons (PAHs) found in soils collected from two formerly used Department of Defense sites impacted by weathered fragments of clay shooting targets. Concentrations of individual carcinogenic PAHs in the ≤250 μm fraction of soil ranged from approximately 0.1 to 100 mg/kg. A novel sample preparation method was developed to produce accurate and precise test diets for oral studies. The resulting test diets showed consistent concentrations of PAHs in soil- and soil-extract-amended diets and a consistent PAH concentration profile. Mean oral relative bioavailability factors (RBAFs) and dermal absorption fractions (ABSd) for benzo(a)pyrene ranged from 8 to 14% and 0.58 to 1.3%, respectively. Using the RBAF and ABSd values, measured here, for benzo(a)pyrene in USEPA's regional screening level equations yields concentrations for residential soils that are approximately eight times higher than those when default values are used (e.g., 9.6 vs 1.2 mg/kg at a target excess risk of 1 × 10-5).

Spatial distributions and sources of PAHs in soil in chemical industry parks in the Yangtze River Delta, China

The Yangtze River Delta (YRD) is one of the fastest developing areas in eastern China and contains many chemical industry parks. The profiles and sources of polycyclic aromatic hydrocarbons (PAHs) in soil in chemical industry parks and surrounding areas in the YRD were investigated by analyzing soil samples (n = 64) were collected in the YRD and Rudong chemical park (RD), a typical chemical park in the Yangtze River Delta. The total concentrations of 19 PAHs in the YRD soil samples were 16.3–4694 ng g−1 (mean 688 ng g−1), and the total concentrations of PAHs in RD were 21.6–246 ng g−1 (mean 75.4 ng g−1). The PAHs in soil in YRD were dominated by four-ring and five-ring PAHs, and the PAHs in RD were dominated by two-ring and three-ring PAHs. It suggested that PAHs may have been supplied to soil in YRD predominantly through coal combustion and vehicle emissions, PAHs in the soil of RD may be due to the volatilization and leakage of chemical raw material. According to the different distribution characteristics of PAHs, the ratio (1.5) of (2 + 3) rings/4 rings was proposed to identify the chemical source of PAHs. The PAH isomer ratios and principal component analysis/multiple linear regression (PCA/MLRA) results indicated that PAHs concentrations in soil in the YRD and RD are mainly supplied by industrial and traffic emissions. Incremental lifetime cancer risks (ILCRs) indicated that PAHs in soil pose negligible cancer risks to children and adults, but much stronger risks to children than adults.

Concentration, distribution, source apportionment, and risk assessment of surrounding soil PAHs in industrial and rural areas: A comparative study

Polycyclic aromatic hydrocarbons (PAHs) are one of the important environmental pollutants that are mainly originated from industrial activities, vehicle emissions, biomass combustion, etc. Nowadays, the surrounding environment of the abandoned industrial area may still have potential health effects on the population, but current researches have paid less attention to this issue. Therefore, we report a comparative investigation focusing on the concentration, distribution, source identification, and risk assessment of PAHs in soils from surrounding areas of an abandoned industrial district and an ecological village in Zhejiang Province, China. Our findings are as follows: the levels of ∑16PAHs ranged from 150.2 to 83096 ng·g−1 with an average concentration of 7680.4 ng·g−1 in industrial area, whereas 49.4 to 778.2 ng·g−1 with an average concentration of 213.5 ng·g−1 in rural area. Although high molecular weight PAHs were both dominant contaminants in study areas, the composition profiles of 16 priority PAHs in soils from the two sampling sites had large differences. Source identification analysis verified that fossil fuel burning and vehicle emissions were the main sources of PAHs in industrial area, while the primary sources were biomass burning and vehicle emission in rural area. The incremental lifetime cancer risk results demonstrated that dermal contact was the most influential factor for all groups, and adults might face higher potential health risk than children in both industrial and rural areas. Moreover, the overall ecological risk of soil PAH pollution was low in rural area, but some individual samples were still high in the abandoned industrial area. Our research is of great significance for the management of the surrounding environment of abandoned industrial areas.

Polycyclic aromatic hydrocarbons, antibiotic resistance genes, toxicity in the exposed to anthropogenic pressure soils of the Southern Russia

The influence of anthropogenic pollution, particularly with polycyclic aromatic hydrocarbons (PAHs) on soil toxicity and spread of antibiotic resistance genes (ARGs) is extremely important nowadays. We studied 20 soil samples from a technogenically polluted site, municipal solid wastes (MSW) landfills, and rural settlements in the southwestern part of the Rostov Region of Russia. A close correlation was established between the results of biosensor testing for integral toxicity, the content of genes for the biodegradation of hydrocarbons, and the concentration of PAHs in soils. The relation between the quantitative content of ARGs and the qualitative and quantitative composition of PAHs has not been registered. Soils subjected to different types of the anthropogenic pressure differed in PAHs composition. The technogenic soils are the most polluted ones. These soils are enriched with 5 ring PAHs and carry the maximum variety of assayed ARGs, despite the fact that they do not receive household or medical waste.

Polycyclic aromatic hydrocarbons in soil-turfgrass systems in urban Shanghai: Contamination profiles, in situ bioconcentration and potential health risks

Abstract Previous studies on the distribution patterns and health risks of polycyclic aromatic hydrocarbons (PAHs) from cities were focused on soils, leaving the soil-plant system less investigated. In this study, PAHs in the soil-turfgrass system in the urban area of the megacity Shanghai were investigated. The results indicated that total PAH concentrations in soils and turfgrasses ranged from 163.02 to 14,289.30 ng g−1 and 45.15 to 1076.98 ng g−1, respectively. On average, four- and three-ring PAHs such as fluoranthene (14.4%) and pyrene (12.4%) were dominant in soils and naphthalene (37.1%) was especially enriched in turfgrasses. The significant differences in compositional profiles of PAHs between soils and turfgrasses implied selective uptake and translocation of PAHs by turfgrasses from soils. The in situ bioconcentration factors (BCFs) of ∑ 16 PAHs in turfgrasses ranged 0.004–1.3, with ryegrass the highest. BCFs decreased significantly with increasing PAH concentrations in soils, suggesting that turfgrass-assisted PAH removal vial root uptake may be more efficient in slightly contaminated soils. Source appointment results indicated that PAHs in Shanghai were majorly derived from fossil fuel/biomass combustion, vehicular emissions and coking. The incremental lifetime cancer risk (ILCR) analysis generally showed a potential cancer risk for adults (total ILCRs > 1 × 10−6 for all sites) and children (total ILCRs > 1 × 10−6 for most sites) especially through dermal contact with soil. Some sites showed total ILCR values above 1 × 10−4, indicating high health risks for both. The results are informative for contamination prevention and control in urban soils from Shanghai and will provide guidance for further exploration of the phytoremediation potential of turfgrasses.

Potential of barn swallow feces as a non-destructive biomonitoring tool for anthropogenic pollutants: Site and chemical specificities and an evaluation of soil contaminants

ABSTRACT In this study, we investigated the potential of swallow feces as a bioindicator to evaluate soil pollution from anthropogenic sources. This biomonitoring was performed with trace elements, polycyclic aromatic hydrocarbons (PAHs), and their chlorinated derivatives (ClPAHs) as pollutants. The concentration of total trace elements targeted was reasonably consistent in both soil and fecal samples. The composition of individual trace elements also showed a similar profile across the sampling sites. The concentration of total PAHs varied in both soil and fecal samples among the sites, whereas their composition showed a similar profile. There were no significant correlations between total PAH or total ClPAH concentrations in either soil or fecal samples. This suggests that the sources and metabolic pathways in swallows may differ between PAHs and ClPAHs. Predictions of individual contaminant levels in soil samples were made from corresponding datasets of the feces using partial least squares analysis, and showed significant correlations based on the magnitude order. It permitted to roughly complement the levels of contaminants in the soils by the estimated equation.

Source apportionment of PAHs in roadside agricultural soils of a megacity using positive matrix factorization receptor model and compound-specific carbon isotope analysis

Polycyclic aromatic hydrocarbon (PAH) contamination in agricultural soils (n = 41) along Shanghai road net was systematically investigated to characterize pollution distribution and to apportion sources. Total PAH (Σ16PAH) concentrations in roadside agricultural soils varied from 17.2 to 3775 ng/g with an average of 339 ± 594 ng/g, 43.9 % of which corresponded to weakly - heavily contaminated levels. The spatial distribution of pollution hotspots depended on heavy traffic volume and intensive industrial activities in adjacent areas. A positive matrix factorization receptor model identified that vehicle emission and combustion of coal, biomass and natural gas were the predominant sources, accounting for 66.0 % and 23.7 % of Σ16PAH loadings, respectively. Stable carbon isotope analysis was applied for the first time in seven sites with high Σ16PAH concentrations for tracing their unique sources. It was concluded that PAHs in the heavily contaminated soil site G18 predominantly came from vehicle emission sources, different from the six other sites controlled by coal-processing and biomass combustion sources. Future studies should focus on quantifying the source contribution of PAHs in roadside agricultural soils based on the combination of multi-isotope approaches due to the data overlap of δ13C in certain sources.

Determination of Polycyclic Aromatic Hydrocarbons in Soil and Bottom Sediments by Gas Chromatography–Mass Spectrometry Using Dispersive Liquid–Liquid Microextraction

The problems and advantages of chromatographic methods for the determination of polycyclic aromatic hydrocarbons (PAHs) in model and real samples of black soil (chernozem), sand, and bottom sediments of the Sea of Azov and the Kurchansky estuary are discussed. We substantiated and implemented sample preparation for analysis using dispersion liquid–liquid microextraction. PAH concentrations in soils of various types and bottom sediments were determined by gas chromatography–mass spectrometry. The specific features of sample preparation of soil and bottom sediments are studied aimed at achieving the maximum recovery of PAHs into the organic phase; the composition of the extraction system and the conditions for the extraction of analytes are optimized; the optimal sample weight is selected. We proposed a gas chromatographic system with mass spectrometric detection (GC–MS) for determining 20 PAHs in soil (bottom sediments). The limits of quantification for the studied PAHs in soils and bottom sediments were 0.2–0.5 µg/kg. The optimized procedure for the GC–MS determination of PAHs was tested on real samples of bottom sediments of the Temryuk Bay of the Sea of Azov.

Mechanism of biochar as a biostimulation strategy to remove polycyclic aromatic hydrocarbons from heavily contaminated soil in a coking plant

Twelve types of biochars were applied in a heavily contaminated soil from a coking plant to gain insights into the mechanism responsible for the microbial response to the addition of different biochar types into soil and biodegradation removal of polycyclic aromatic hydrocarbons (PAHs). The biochars primarily influenced the bacterial community at the genus level, while they strongly affected the fungal community not only at the genus level but also at the class and phylum levels. Principal component analysis (PCA) indicated that the inorganic minerals in biochars played a key role in stimulating microbial abundance (bacteria) and diversity (bacteria and fungi) in soil from the coking plant, and significantly negative correlations between the residual concentrations of PAHs in biochar-treated soils and the ash contents in biochars (generally, p < 0.05 for PAHs with 3–6 rings) were observed. These findings further suggested a positive effect of the inorganic minerals of biochars on stimulating changes in microorganisms, which could contribute to the biodegradation of PAHs in soil from the coking plant. Generally, the addition of biochars to the soils increased the biodegradation percentages of individual PAHs by 3.0–60.3% compared to those of the control. Among these biochars, rice straw-derived biochar pyrolyzed at 600 °C (RS6) effectively degraded PAHs from soil, with increasing biodegradation percentages of individual PAHs from 40.00% to 58.84%. This result was likely attributed to that the substantially specific Acidobacteria-related genera in RS6-treated soil were detected, which contributed to the effective biodegradation of PAHs. Accordingly, biochars pyrolyzed at a relatively high heating temperature with rice straw feedstock containing relatively high mineral nutrients are recommended for application to heavily PAH-contaminated soils.

Contamination of toxic metals and polycyclic aromatic hydrocarbons (PAHs) in rooftop vegetables and human health risks in Bangladesh

Rooftop cultivation of vegetables is considered as a potential food source for urban population. However, rooftop products in the urban area can be contaminated by different types of pollutants like toxic metals and polycyclic aromatic hydrocarbons (PAHs). The present study is the first that investigated the concentrations of toxic metals and PAHs in rooftop soils and vegetables grown in the urban and peri-urban areas of Bangladesh. Red amaranth and Spinach were selected for rooftop cultivation, and both soil and vegetable samples were collected and analyzed for determining the concentrations of cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) as toxic metals, while naphthalene, fluorene, phenanthrene, anthracene, pyrene, benzo(a)anthracene, and chrysene as PAHs. The study observed that urban rooftop soil and vegetables were highly contaminated with toxic metals and PAHs as compared to peri-urban rooftop samples. The metal concentrations were found in order of Zn > Cu > Pb > Cd, however, Pb and Cd concentrations in urban vegetables exceeded the safe limit. On contrary, negligible concentrations of PAHs were detected in both urban and peri-urban rooftop vegetables. The values of health risk indices revealed that the concentrations of toxic metals and PAHs in urban rooftop vegetables would not pose any carcinogenic and non-carcinogenic health risks for adults and children and thus are considered to be safe for consumption. The findings of this study will provide scientific evidence to the policy makers and public administrations for urban agriculture based policy formulation as well as will encourage the city dwellers towards urban rooftop agricultural practices.

Polycyclic aromatic hydrocarbons in fishes and some environmental samples on the coast of Ghana

Abstract. Osei-Yeboah E, Appiah-Opong R, Ofosuhene M. 2020. Polycyclic aromatic hydrocarbons in fishes and some environmental samples on the coast of Ghana. Ocean Life 4: 4-16. The shift in industrialization in our society, including mining of coal and minerals, drilling for oil has led to the accumulation of xenobiotic products and natural chemical substances. The activities from mining and drilling have continuously contributed to the release of polycyclic aromatic hydrocarbons (PAHs) and lead to their deposition in coastal environments. The process ultimately leads to bioaccumulation in plants and animals, creating dangerous pollutants. PAHs is a well-known cause of cancer, mutation, and embryonic pathologies. In Jubilee oil fields, Ghana, oil drilling is ongoing. However, onshore baseline environmental assessment of PAHs has not yet been performed. In this study, we performed an environmental assessment of some communities bordering the oil drilling fields to establish (i) levels of fish DNA adduct formation of fishes, (ii) levels of PHA in soil, plants, water, and fish. Several fishes from three study areas showed the presence of micronuclei as evidence in the examination of blood smears, although their mean micronucleated frequencies were below the threshold frequency of 15%. There was no statistical difference between their mean frequencies using one-way ANOVA analysis with a p-value &lt; 0.05 except that of the data from one species, Chloroscombrus chrysurus (Linnaeus, 1766). Reverse-phase HPLC analysis of fish, water, plant and soil samples collected from six study sites was performed. Two fish species Pomadasys incisus (Bowdich, 1825) at Aboadze and Thunnus alalunga (Bonnaterre, 1788) from Dixcove recorded four and one PAH compound, respectively with concentrations above the maximum contaminant levels of 30 ?g/kg set by the USEPA. The mean concentration of PAHs in water samples from two of the four study areas ranged from 1.4 to 1255 ?g/L. All samples recorded concentrations above the threshold limit value of 50 ng/L set by the World Health Organization. Sixty plant samples were collected across the six study areas, and only Erythrina senegalensis DC. and Ficus umbellata Vahl recorded the presence of PAHs with concentrations in the range of 0.15-4.70 mg/kg. Soil samples were collected from two different depths of 0-15 cm and 15-30 cm. The mean concentration of PAHs in surface soils (0-15cm) ranged from 0.1 to 95 mg/Kg, with that at 15-30 cm ranging from 0.12 to 105 mg/kg. The PAH composition profile in all the samples was similar, with 2- 3 ring PAHs being dominant, which is suggestive of a petrogenic source.

Formation mechanism of soil PAH distribution: High and low urbanization

Urbanization is an important driving force for the distribution of polycyclic aromatic hydrocarbons (PAHs) in urban soils. Research on factors affecting PAH distribution in urban soils has focused on analyses of statistical relationships, and quantitative models are not available in the literature. Accordingly, we chose the urban area of Nanjing (high urbanization), and Dingshu (low urbanization), and then comprehensively utilized soil sample test analyses, multivariate statistics, and other technical means to (1) study the concentration and sources of PAHs in urban soils, and (2) identify the main controlling factors that affect urban soil PAH distribution. We found that the population density and black carbon (BC) components were the critical factors of soil PAH distribution in Nanjing, yet BC components and leaf area index in Dingshu. We then constructed a quantitative relationship model of urban soil PAH distribution in different levels of urbanization. Using this model, we conducted a preliminary analysis of the formation mechanism of urban soil PAHs under different urbanization levels. This research provides a basis for finely controlling regional urban soil PAH pollution.

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

Facile synthesis of polydivinylbenzene coated magnetic polydopamine coupled with pressurized liquid extraction for the extraction and cleanup of polycyclic aromatic hydrocarbons in soils

Due to the trace levels of polycyclic aromatic hydrocarbons (PAHs) in soil and the complexity of soil matrices, effective sample pretreatment methods are of great significance to obtain accurate analytical results. In this paper, polydopamine (PDA) encapsulated Fe3O4 particles were used as seeds for in situ polymerization of divinylbenzene (DVB) to derive magnetic hybrid material Fe3O4@PDA@PDVB. Coupled with pressurized liquid extraction, Fe3O4@PDA@PDVB was investigated as a selective adsorbent for the extraction and cleanup of PAHs in soil. The prepared magnetic material was characterized and demonstrated to possess strong hydrophobicity and superparamagnetism. Under optimal conditions, Fe3O4@PDA@PDVB can effectively extract 15 PAHs from a 30% methanol solution within 2 min, and it is more selective for PAHs than for n-alkane in soil extracts. The matrix effect significantly decreased after extraction by the prepared material, which showed superiority to a silica gel column method (EPA 3630C Method). The developed method was linear (5–1000 ng g−1) with coefficient of determination (R2) ranging from 0.9986–0.9998, and the limits of detection were 0.13–0.54 ng g−1. Additionally, repetitive experiments indicated that the prepared material was reproducible and reusable with relative standard deviations below 8.4% and 8.6%, respectively. Finally, the new method was successfully employed to determine the concentrations of PAHs in genuine soil and standard reference material, and the results were comparable to those of widely utilized EPA methodology.