Polycyclic Aromatic Hydrocarbons Concentrations In Soil Research Articles

Effects of Chinese “double carbon strategy” on soil polycyclic aromatic hydrocarbons pollution

Polycyclic aromatic hydrocarbons (PAHs) and carbon dioxide primarily originate from the combustion of fossil fuels and biomass. The implementation of the Chinese “double carbon strategy” is expected to impact the distribution of PAH emissions, consequently influencing the spatial distribution trend of PAHs in surface soil. Therefore, it is crucial to quantitatively evaluate the effectiveness of the Chinese “double carbon strategy” on soil PAH pollution for the purpose of “the reduction of pollution and carbon emissions”. This study utilized 15,088 individual PAH concentration data from 943 soil samples collected between 2003 and 2020 in China, in conjunction with PAH emissions at a 10 km resolution, for meta-analysis. The calculated PAH emissions in this study are in line with the global PAH emission inventory (PKU-PAH-2007), with a relative standard deviation at the provincial level of less than 25 %. Subsequently, a novel method was developed using emission density and Kow of PAHs to predict PAH concentrations in surface soil based on a least-squares regression model. Compared to other environmental models, the method established in this study significantly reduced the percent sample deviation to less than 70 %. Furthermore, energy consumption data for China were simulated based on the implementation plan of the “double carbon strategy” to project PAH emissions and soil PAH levels for the years 2030 and 2060. The predicted PAH emissions in China were estimated to decrease to 41,300 t in 2030 and 10,406.5 t in 2060 from 78,815 t in 2020. Moreover, the heavily contaminated areas of soil PAHs (i.e., total PAH concentrations in soil exceeding 1000 μg kg−1) were projected to decrease by 45 % and 82 % in 2030 and 2060, respectively, compared to levels in 2020. These findings suggest that the implementation of the “double carbon strategy” can fundamentally reduce the pollution of PAHs in surface soil of China.

Lagging pollution of polycyclic aromatic hydrocarbons in the rebuilt e-waste site: From the perspective of characteristics, sources, and risk assessment

Little information is known regarding how the lagged pollution of polycyclic aromatic hydrocarbon (PAH) influenced the environment and human health after an e-waste dismantling site was rebuilt. This study investigated the characteristics, sources, and risk assessment of PAHs in a rebuilt e-waste site and its surrounding farmland by analyzing the samples of soil, dust, water, and vegetable. Concentrations of PAHs in soil, vegetable and water in the rebuilt site were relatively higher than in its surrounding farmland. The concentrations in surface soils, soil columns, dust, vegetables, and water varied from 55.4 to 3990 ng g−1, 1.65 to 5060 ng g−1, 2190 to 2420 ng g−1, 2670 to 10,300 ng g−1, and 46.8 to 110 μg L−1 in the e-waste site, respectively. On the farmland, PAH concentrations in surface soils, vegetables, and water ranged from 41.5 to 2760 ng g−1, 506 to 7640 ng g−1, and 56.6 to 89.2 μg L−1, respectively. A higher proportion of high-molecular-weight PAHs (HMW-PAHs) appeared in all multimedia compared with low-molecular-weight PAHs (LMW-PAHs). Diagnostic ratio together with positive matrix factorization (PMF) revealed that vehicle emission was the primary source in this area, and the activity of e-waste disposal was another important source in the rebuilt e-waste site. Based on the deterministic health risks, people working in the reconstructed e-waste site were exposed to low risks, whereas the residents living near the surrounding farmland were exposed to low risk. Sensitivity analyses indicated that exposure frequency and PAH concentrations were the main factors that influenced exposure risk. This study provides valuable insight into the comprehension of the lagging pollution effects of PAH on the environment and human health after the e-waste site was rebuilt.

Drivers distinguishing of PAHs heterogeneity in surface soil of China using deep learning coupled with geo-statistical approach

Although numerous studies have reported the influencing factors of polycyclic aromatic hydrocarbons (PAHs) in surface soil from source, process or soil perspectives, the mechanism of PAHs heterogeneity in surface soil are still not well understood. In this study, the effects of 16 PAHs in surface soil of China sampled between 2003 and 2020 with their 17 “source-process-sink” factors at 1 km resolution (N = 660)) were explored using deep learning (eXtreme Gradient Boosting) to mine key information from complex dataset under the optimized parameters (i.e., learning rate = 0.05, maximum depth = 5, sub-sample = 0.8). It was observed that top five factors of 16 PAH had the largest cumulative contribution (i.e., from 84.8% to 98.1%) on their soil concentrations. PAH emission was the predominant driver, and its effect on soil PAH increases with increasing logKow. Soil was the second driver, in which clay can promote the partition of PAHs with low or middle logKow. However, sand can accumulate those congeners with high logKow. Moreover, the deep learning plus geo-statistical models (with low deviation for testing dataset (N = 283)) were capable of predicting soil PAH concentrations using their drivers with high accuracy. This study improved the understanding of the environmental fate and spatial variability of soil PAHs, as well as provided a novel technique (i.e., deep learning coupled with geo-statistics) for accurate prediction of soil pollutants.

Toxicological Risk Evaluation of Polycyclic Aromatic Hydrocarbons in Soils from a Petroleum Spillage Site at Kokori in the Niger Delta Region of Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants that are produced by the incomplete combustion of organic sources and are widely found in soils. This present research was carried out to evaluate the concentrations and toxicological risk assessment of the United States Environmental Protection Agency's sixteen priority polycyclic aromatic hydrocarbons (16 priority PAHs) in soils from the vicinity of an oil spillage site in Delta State of Nigeria. The level of pollution and potential toxicological health hazards of the PAHs were assessed in surface soil samples using soxhlet extraction of and Gas Chromatography-Mass Spectrometry (GC-MS). Thirteen out of the sixteen USEPA priority PAHs were detected in the soil sample. The concentrations of PAHs in the petroleum-contaminated soils in this investigation ranged from 0.01181 ppm to 1.16054 ppm, with the total estimated concentration of the 16 priority PAHs being 5.6713 ppm. Furthermore, the distribution of the PAHs in the study area was predominated by LMW PAHs (62%) over HMW PAHs (38%). Additionally, the total toxicity equivalency quotients TEQ (B[a]Peq) result of the carcinogenic potency of the USEPA priority PAHs was calculated as 0.08689 ppm (8.689%) and was discovered to be within the Canadian TEQ (B[a]Peq) threshold of 0.6 ppm. This suggests that the soil in the study area is safe based on the Canadian TEQ (B[a]Peq) standard and does not constitute a carcinogenic risk. However, the long-term bioaccumulation of these low quantities of PAHs in human has been found to constitute a potential health concern due to bioaccumulation in living systems.

Distribution and transfer rules of polycyclic aromatic hydrocarbons in soil-wheat ecosystems in China.

The translocation and accumulation patterns of polycyclic aromatic hydrocarbons (PAHs) in the soil-crop system have important implications for the fate of PAHs and human health. This study summarized the concentrations of 16 priority PAHs in the soils and various parts of mature winter wheat in China, sourced from a screening of previous literature in English and Chinese databases. The study analyzes the distribution characteristics, transfer patterns, and human health risks of PAHs in sites studied in Shaanxi, Henan, and Shandong provinces. The results showed that the concentrations of Σ16 PAHs in the rhizosphere soil of wheat ranged from 10.30 to 893.68 ng/g, in descending order of Shaanxi > Henan > average > Shandong. In sites with mild to moderate contamination (200 < Σ16 PAHs < 600 ng/g; i.e., Henan and Shaanxi), the concentration of Σ16 PAHs in the roots was higher than that in the stems or the grains, while in contamination-free sites (Σ16 PAHs < 200 ng/g; i.e., Shandong), the highest concentration of Σ16 PAHs was found in the stems. Generally, the concentrations of PAHs increased in the order of roots-stems-grains. The predominant PAHs in each part of wheat were 2- or 3-ring compounds, with five- or six-ring PAHs being more prevalent in wheat from Shanghe, Shandong. The bioaccumulation factors of different wheat parts from Shaanxi and Henan were consistently smaller than 1, and low- and medium-ring (2-4 rings) PAHs had bigger bioconcentration factors than high-ring (5-6 rings) PAHs. However, the accumulation of PAHs in the aboveground parts of wheat was larger than that in the underground parts of the Shandong sites. The linear regression relationship between the octanol-water partition coefficient and root concentration factor (RCF) of PAHs reflected that low and medium-ring PAHs were more easily absorbed by wheat roots than high-ring PAHs in Shaanxi and Henan. Our assessment of the health risks of oral wheat intake in adults and children by the incremental lifetime cancer risk (ILCR) model found a potential carcinogenic risk for both age groups in each province, with higher risks in adults than in children.

Treatment of PAHs contaminated soil in abandoned industrial site using combined method of improved in situ capping and electrokinetic enhanced-bioremediation

In situ capping and bioremediation are common technologies for treating contaminated soil at industrial sites. However, these two technologies have some shortcomings for treating soil heavily contaminated with organic matter, such as the limited adsorption in capping layer and the low biodegradation efficiency. This study proposed the method of an improved in situ capping combined with electrokinetic enhanced-bioremediation, and investigated its feasibility for treating heavily polycyclic aromatic hydrocarbons (PAHs) contaminated soil at an abandoned industrial site. By analyzing the changes in soil properties, PAHs concentration, and microbial community in experiments with voltages of 0, 0.8, 1.2, and 1.6 V cm−1, it was found that improved in situ capping could effectively sequester PAHs migration by adsorption and biodegradation, and electric field could enhance PAHs removal from contaminated soil and bio-barrier. In the experiments with electric field, soil environment under the voltage of 1.2 V cm−1 was more favorable for the growth and metabolism of microorganisms, and the residual PAHs concentrations (19.47 ± 0.76 mg kg−1 and 619.38 ± 20.05 mg kg−1) in the bio-barrier and contaminated soil of experiment with 1.2 V cm−1 were the lowest, which indicated that optimization of the electric field conditions could lead to better effects.

Status assessment and probabilistic health risk modeling of polycyclic aromatic hydrocarbons (PAHs) in surface soil across China

Polycyclic aromatic hydrocarbon (PAH) accumulation in topsoil is getting particular concern with the rapid development of urbanization and industrialization, while the overall pollution status and related risk posed by PAHs received limited attentions at the national scale. This study conducted an overview of published data on 16 priority control PAHs by USEPA on the related peer-reviewed 207 research papers between 2000 and 2020 in 30 provinces of China. Based on that, the pollution levels, composition status, spatial distribution pattern, ecological risk, and human health risk posed by soil PAHs were evaluated. Monte Carlo simulation was adopted to model the probabilistic health risk and identify the contributor of such risks. Results demonstrated the concentrations of ∑16PAHs in soil varied from “undetected” to 261 μg g−1 with a mean value of 0.63 μg g−1, indicating the obvious accumulation of PAHs in topsoil of most provinces in China compared with the guideline value (0.2 μg g−1). The concentrations of ∑16PAHs in surface soil of China has obvious regional characteristics. Higher concentrations of soil PAHs are mainly distributed in north, northwest, and eastern regions, especially in Xinjiang, Shandong, Jiangsu, Sichuan, and Guangxi Province. Risk assessment indicates potential ecological and human health risk were posed by soil PAHs, therefore, reducing soil PAHs concentration and exposure frequency are the most effective pathways to protect human health. Despite the fact that risks posed by soil PAHs are generally low, concentrations of PAHs in some sites are relatively high. It is necessary to take effective measures to remediate soil PAHs pollution in certain areas to reduce concentration and associated risks.

Biochar reduces uptake and accumulation of polycyclic aromatic hydrocarbons (PAHs) in winter wheat on a PAH-contaminated soil

Biochar has been used previously for remediation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils for years, which has achieved remarkable results in improving removal of soil PAHs and reducing PAHs uptake in crops. However, the underlying mechanism of biochar application in reducing the uptake and accumulation of PAHs in winter wheat remains unclear. Pot trials using PAHs-contaminated soils were conducted for whole plant growth period of winter wheat, which were amended with 2% (w/w) bamboo biochar (BB), coconut shell biochar (CB) and maize straw biochar (MSB) or not (CK). Compared with CK, application of the three types of biochar significantly (p < 0.01) reduced grain PAHs concentration, the total equivalent concentration (TEC) values and the incremental lifetime cancer risk (ILCR) of grain PAHs, indicating that application of biochar reduced the exposure risk of PAHs in wheat grain, especially for MSB. Consistently, application of the three types of biochar significantly (p < 0.05) reduced uptake and accumulation of PAHs in root and stem of wheat, which may be due to that application of biochar enhanced the degradation of PAHs in the rhizosphere soil. Compared with CK, application of the three types of biochar significantly (p < 0.05) reduced the concentration of PAHs in the rhizosphere soil by 15.9%, 26.1% and 33.7%, respectively. It was found that the degradation rate of HMW PAHs (high molecular weight PAHs, 5-6 ring PAHs) was significantly (p < 0.05) higher than that of LMW PAHs (low molecular weight PAHs, 2-4 ring PAHs) regardless of types of biochar used. Additionally, application of the three types of biochar significantly increased the relative abundance of dominant bacterial phyla and genera in soil. Redundancy analysis and correlation analysis results also showed that there was a strong correlation between the removal rate of PAHs and dominant bacteria in the rhizosphere soil. The present study indicated that biochar could reduce dietary risk of PAHs in wheat grains mainly by increasing the abundance of bacteria related to PAHs degradation, promoting the biodegradation of PAHs in the rhizosphere soil and consequently reducing PAHs uptake in wheat.

Spatial distribution of polycyclic aromatic hydrocarbons in dust and soils from informal trade sites in southern Nigeria: Implications for risk and source analysis

Polycyclic aromatic hydrocarbons (PAHs) are a group of semi-volatile and persistent organic compounds considered priority pollutants because of their pervasive nature and high toxicity to the ecosystem and humans. Therefore, this study aimed to evaluate the PAH concentrations in dust and soils around informal trade sites (ITS) in Nigeria to determine the level of risk, sources, and significance of these activities to the PAH load of the environment. The 16 US EPA PAHs in dust and soils from ITS were determined by gas chromatography-mass spectrometry (GC-MS). The PAH concentrations in dust from these informal trade sites varied from 120 to 8790, 56 to 4780, and 102–1090 μg kg−1 for automobile mechanic workshops (AMW), car dismantling (CDS), and material recovery sites (MRS), respectively, whereas those of soils ranged from 3000 to 95,500, 554 to 14,700, and 966–25,200 μg kg−1 for AMW, CDS, and MRS respectively. The PAH profiles indicated that 3- to 5-ring PAHs were prominent in dust and soils around the ITS. The concentrations of the US EPA 16 PAHs in dust and soils from these ITS showed no correlation with organic matter, while the concentrations of PAH homologues in soils of these ITS showed no correlation with those of dust. Incremental lifetime cancer risk (ILCR) values in the magnitude of 10−4 to 101 were obtained for adult and childhood exposure to PAHs in dust and soils from these ITS. Exposure to PAHs in dust from these ITS gives rise to less risk than for soils. The results indicated that automobile mechanic workshops contribute more PAHs to the environment than car dismantling and material recovery activities. The source analysis showed that the PAH contamination of these sites arises from burning of biomass, plastic materials, and oils, and emissions from vehicles.

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.

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

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

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.

Effects of Comamonas testosteroni on dissipation of polycyclic aromatic hydrocarbons and the response of endogenous bacteria for soil bioremediation.

Bioremediation is a promising method of treating polycyclic aromatic hydrocarbons (PAHs) in contaminated soil; however, the understanding of the efficiency and the way of microbial inoculants work in complex soil environments is limited. Comamonas testosteroni (Ct) strains could efficiently degrade PAHs, especially naphthalene (Nap) and phenanthrene (Phe). This study aimed to explore the functional role of Ct in soil indigenous microorganisms and analyze the effect of Ct addition on PAHs concentration in PAH-contaminated soil. The results showed that inoculation with Ct degraded naphthalene (Nap), phenanthrene (Phe), and benzo [α] pyrene (BaP) significantly; the degradation rates were 63.38%, 81.18%, and 37.98% on day 25, respectively, suggesting that the low molecular weights of Nap and Phe were more easily degraded by microorganisms than those of BaP. We speculated that BaP and Phe might be converted into Nap for further degradation, which is the main reason for the low degradation rate of Nap detected after 10-25days. Network analysis showed that inoculation with Ct significantly increased bacteria community abundance closely related to PAHs. Structural equation models confirmed that Steroidobacter, as functional bacteria, could affect the degradation of Nap and BaP. Inoculated Ct effectively enhanced the synergy among indigenous bacteria to degrade PAHs. This finding will help understand the function of inoculated Ct strains in PAH-contaminated soil at the laboratory level.

Polycyclic aromatic hydrocarbons (PAHs) in riparian soils of the middle reach of Huaihe River: A typical coal mining area in China

ABSTRACT In the present research work, the concentration, distribution, composition, sources, potential toxicity, and ecological risk of PAHs in riparian soils of the middle reach of Huaihe River (along a 430-kilometer stream gradient) were studied. The total concentrations of PAHs varied from 210 to 39000 ng g−1, with a mean concentration of 3400 ± 8400 ng g−1 and a median value of 760 ng g−1. The middle section (Huainan-Bengbu section) with frequent coal mining and utilization activities was found to be the most contaminated region. High molecular weight (5- and 6- ring PAHs) and medium molecular weight (4- ring PAHs) PAHs were predominant. Based on the diagnostic ratios method and positive matrix factorization (PMF) model, PAHs in riparian soils were mainly originated from pyrogenic sources including vehicle emissions, and biomass and coal combustion. The calculation of total TEQBaP concentrations and risk quotient (RQ) indicated a low to moderate risk level of PAHs in most regions of the study area, but some specific sites showing high toxicity and ecological risk should be caused alarm and attention.

Elevated urbanization-driven plant accumulation and human intake risks of polycyclic aromatic hydrocarbons in crops of peri-urban farmlands.

As an ubiquitous carcinogen, polycyclic aromatic hydrocarbons (PAHs) are closely related to anthropogenic activities. The process of urbanization leads to the spatial interlacing of farmlands and urbanized zones. However, field evidence on the influence of urbanization on the accumulation of PAHs in crops of peri-urban farmlands is lacking. This study comparatively investigated the urbanization-driven levels, compositions, and sources of PAHs in 120 paired plant and soil samples collected from the Yangtze River Delta in China and their species-specific human intake risks. The concentrations of PAHs in crops and soils in the peri-urban areas were 2407.92ngg-1 and 546.64ngg-1, respectively, which are significantly higher than those in the rural areas. The PAHs in the root were highly relevant to those in the soils (R2 = 0.63, p < 0.01), and the root bioconcentration factors were higher than 1.0, implying the contributions of root uptake to plant accumulations. However, the translocation factors in the peri-urban areas (1.57 ± 0.33) were higher than those in the rural areas (1.19 ± 0.14), indicating the enhanced influence through gaseous absorption. For the congeners, the 2- to 3-ring PAHs showed a higher plant accumulation potential than the 4- to 6-ring PAHs. Principal component analysis show that the PAHs in the peri-urban plants predominantly resulted from urbanization parameters, such as coal combustion, vehicle emissions, and biomass burning. The mean values of estimated dietary intake of PAHs from the consumption of peri-urban and rural crops were 9116ngday-1 and 6601.83ngday-1, respectively. The intake risks of different crops followed the order rice > cabbage > carrot > pea. Given the significant input of PAHs from urban to farmland, the influence of many anthropogenic pollutants arising from rapid urbanization should be considered when assessing the agricultural food safety.

Impacts of heavy duty truck emissions on the vertical distributions of soil polycyclic aromatic hydrocarbons at a big haulage vehicle park

Nigeria relies heavily on heavy duty haulage vehicles to convey commodities from one end of the nation to the other, owing to the decades-long collapse of the rail transportation infrastructure. This is resulting in settings with very high concentrations of the trucks on the country's key roads. Diesel engine exhausts have long been recognized to be detrimental to human health. The concentrations of polycyclic aromatic hydrocarbons (PAHs) in the top and bottom soil samples from an extensive haulage vehicle stop located at Ogere, a roadside town along the ever busy Lagos-Ibadan highway were investigated. Soil samples taken at depths of 0–15 cm and 15–30 cm were subjected gas-chromatographic/mass spectrometer analysis. The Ʃ priority PAHs in the top and bottom soils at four sampling locations ranged between 16.4 and 32.0 mg/kg and 18.6–26.6 mg/kg respectively. The corresponding Ʃ carcinogenic PAHs for top and bottom soils ranged between 9.2 and 17.4 mg/kg and 8.7–12.0 mg/kg respectively. The concentrations of PAHs obtained in this study clearly exceeded the permissible limits set for soil PAHs in most developed nations of the world. The diagnostic ratio attributed the observed PAHs to diesel emissions. The study concluded that the emissions from the trucks at the haulage vehicle stop have tremendous impact on the soil PAH concentrations.

Distribution, risk assessment, and source apportionment of polycyclic aromatic hydrocarbons (PAHs) using positive matrix factorization (PMF) in urban soils of East India.

This study investigated 16 United States environmental protection agency priority PAHs profiles and their sources in 40 urban soils collected from two industrialised cities, Jamshedpur and Bokaro, in east India and assessed their health risk to humans. The results showed the predominance of high molecular weight (HMW) PAHs (4-5 rings). The total PAHs concentration in surface soils ranged from 2223 to 11,266ng/g and 729 to 5359ng/g (dw), respectively, for Jamshedpur and Bokaro. Higher concentrations of PAHs were recorded at the selected industrial areas and heavy traffic zones of both cities. In JSR city 4-ring PAHs contributed 43% of total PAHs trailed by 5-ring PAHs 27.2%. Similarly, in BKR city 4-ring PAHs contributed 34% of the total PAHs, followed by 3-ring PAHs 28.9% and 5-ring PAHs 22.9%. Total organic carbon in surface soils exhibited moderate correlation with the low molecular weight (ΣLMW) PAHs (R2 = 0.69) and a comparatively strong correlation with the ΣHMW PAHs (R2 = 0.89), suggesting strong adsorption of HMW PAHs to urban soils. The Diagnostic and PMF modelling analysis indicated that the major sources of PAHs contamination in soils were petroleum combustion, vehicular emissions, biomass, and coal combustion. The health risk assessment shows that the cumulative probability of carcinogenic risks was under the acceptable limits of 10-4 to 10-6. At some sampling areas in both cities, the maximum value of total exposure cancer risk slightly exceeded the acceptable limits indicating some carcinogenic risk for adults.

Dilution of concentrations of PAHs from atmospheric particles, bulk deposition to soil: a review.

Polycyclic aromatic hydrocarbons (PAHs) are emitted to the atmosphere by various anthropogenic activities as well as natural sources, they undergo long-range transport, are degraded (e.g., by photolysis) and finally they are deposited onto the surface and potentially accumulate in topsoil. The dry deposition of particle-bound PAHs dominates the accumulation of PAHs in soil and their further fate in soil is governed by sorption/desorption from these airborne particles. This paper offers an overview on concentrations of particle-bound PAHs, the dry deposition fluxes and finally concentrations of PAHs in soil. In addition, spatial and temporal variations of PAHs are considered. The results show that concentrations of particle-bound PAHs typically range from 1mgg-1 up to 10mgg-1 in cities with coal-based heating in winter and in countries with coal-based industry incl. electrical power production. These values are very high and exceed the legal limits set in soils by orders of magnitude. Atmospheric deposition rates typically reach several mgm-2a-1, but in winter, especially in countries with heating, deposition rates are up to 10 times higher. PAHs concentrations in soils show a very wide variation from less than 1µgg-1 in rural areas up to 10µgg-1 in urban space, which is about 1000 times lower than the concentration of PAHs on particles in the atmosphere. This demonstrates the relevance of high concentrations of PAHs on airborne particles deposited on soils, which also highlights the importance of considering incremental lifetime cancer risk models for both air and soil and assessing the total health risk of PAHs to humans.

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.

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.