Polycyclic Aromatic Hydrocarbons In Surface Soils 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.

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.

Preferential association of polycyclic aromatic hydrocarbons (PAHs) with soil colloids at an e-waste recycling site: Implications for risk of PAH migration to subsurface environment

Polycyclic aromatic hydrocarbon (PAH) contamination at e-waste recycling sites poses high ecological and human-health risks. Of note, PAHs in surface soils can be mobilized through colloid-facilitated transport, and may migrate into the subsurface and pollute groundwater. Here, we show that the colloids released from the soil samples at an e-waste recycling site in Tianjin, China contain high concentrations of PAHs, with total concentrations of 16 PAHs as high as 1520 ng/g dw. Preferential association of the PAHs with the colloids is observed, with the distribution coefficients of PAHs between colloids and bulk soil often above 10. Source diagnostic ratios show that soot-like particles are the main source of PAHs at the site, due to the incomplete combustion of fossil fuels, biomass, and electronic wastes during the e-waste dismantling practices. Due to their small sizes, a large fraction of these soot-like particles can be remobilized as colloids, and this explains the preferential association of PAHs with colloids. Moreover, the colloids-soil distribution coefficients are higher for the low-molecular-weight PAHs than for the high-molecular-weight ones, possibly attributable to the different binding routes/modes of these two groups of PAHs to the particles during combustion. Notably, the preferential association of PAHs with colloids is even more pronounced for the subsurface soils, corroborating that the presence of PAHs in the deeper soils is primarily the results of downward migration of PAH-bearing colloids. The findings highlight the important role of colloids as a vector for the subsurface transport of PAHs at e-waste recycling sites, and call for further understanding of colloid-facilitated transport of PAHs at e-waste recycling sites.

Source identification and health risk assessment of PAHs in surface soils from the vicinity of Arad-Kouh processing and disposal complex, Tehran, Iran

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) as ubiquitous pollutants can pose potential environmental and also human health risks. Therefore, this study was conducted for detecting, identifying the sources and evaluating the health risks of PAHs in topsoils in vicinity of Arad-Kouh processing and disposal complex, Tehran, Iran in 2020. In so doing, a total of 30 surface soil samples were collected from 10 sampling sites adjacent to Arad-kouh complex. After extraction of analytes, the gas chromatography/mass spectrometry (GC–MS) method was used to determine the rates of PAH compounds in surface soil samples. Based on the results obtained, the total concentrations (µg kg−1) of 16 PAHs ranged from 863 to 1384 with a mean of 1123. PAHs with 4–6 rings in their molecules with 65.3% of ∑16PAH mass dominated the PAH profiles. Molecular diagnostic ratios (MDRs) indicated that most of PAH compounds could originate from pyrogenic sources. The total incremental lifetime cancer risks (ILCRs) of PAH compounds with an average value of 4.20E-05 (ranging from 3.02E-05 to 5.23E-05), indicating a low potential carcinogenic risk of PAH compounds in the study area, especially through dermal contact. Although, the ILCRs values showed negligible adverse health effects from direct ingestion and inhalation of PAH compounds in the study area, regular and periodic monitoring of content and sources identification of PAHs in different environments and efforts to mitigate of their pollution for human health maintenance are recommended.

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 < 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.

A Preliminary Study on Pollution of Polycyclic Aromatic Hydrocarbons in Soil around a Thermal Power Plant of Xi'an City

To understand the status and risk of polycyclic aromatic hydrocarbons (PAHs) pollution in industrial areas in China. The total of 4 surface soil samples were collected from a thermal power plant of Xi’an. The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were analyzed by high performance liquid chromatography (HPLC). In addition, the composition, source, pollution level and risk assessment of PAHs in surface soil of thermal power plant were studied. The results showed that the total concentrations of 16 PAHs ranged from 3.28 to 8.88 μg•g-1, with a mean of 5.52 μg•g-1. The concentration of 7 carcinogenic PAHs (Σ7CPAHs) ranged from 1.52 to 4.82 μg•g-1, with a mean of 2.60 μg•g-1. The ∑PAHs in around thermal power plant surface soils of Xi’an belonged to serious pollution level. The PAHs in present study were mainly composed of medium molecular weight PAHs and high molecular weight PAHs, which have strong three effects. The results of source analysis showed that the PAHs in surface soil were mainly originated from the combustion of fossil oil, coal, wood and other biomass. The results of ecological risks of PAHs in the surface soil showed that all samples were polluted generally. The potential ecological risk of PAHs belonged to the serious level in individual PAHs and samples. There are two samples value of TEQBap exceed the security value 0.600 μg•g-1. Therefore, the environment of industrial areas should be attention and controlled.

Characteristics and Influencing Factors of Polycyclic Aromatic Hydrocarbons in Surface Soils from Typical Industrial Areas of Chengdu

To improve the pollution signature database for polycyclic aromatic hydrocarbons (PAHs) in typical industrial areas in China, surface soil samples were collected from four typical petroleum-processing industrial areas of Chengdu. The concentration and composition of 16 PAHs listed for prior control by the United States Environmental Protection Agency (US EPA) were determined using high-performance liquid chromatography (HPLC). The result showed that the concentration of PAHs in surface soils of the four industrial areas ranged from 191.2 to 1604.2 μg·kg-1, with an average of (583.6±365.6) μg·kg-1. The PAHs in the present study were mainly composed of medium-molecular-weight PAHs and high-molecular-weight PAHs. Among the PAHs detected in the study soils, phenanthrene (PHE), pyrene (PYR), fluoranthene (FLT), and benzo[b]fluoranthene (BbF) were the major pollutants presenting a potential pollution risk. Selected mathematical statistical methods were used to analyze the relationship between soil organic matter (SOM), soil particle diameter and PAH content, and to simultaneously identify the factors influencing PAHs in the soils. SOM was shown to be a favorable absorbent, predicting the migration and transformation behavior of PAHs in surface soil and soil ecological risk (i.e., PAH carcinogenicity) to some extent. Compared with SOM, the correlation between PAHs and soil particle size was relatively low, showing a weak positive correlation with silt, a weakly negatively correlation with clay, and no significant correlation with sand. These results provide a basis for soil remediation practices and further research in such industrial areas.

Evaluation of Urban Soil Pollution: A Combined Approach of Toxic Metals and Polycyclic Aromatic Hydrocarbons (PAHs)

Overcrowded urban areas are exposed to quotidian loads of toxic metals and PAHs. Simultaneous analysis of mentioned pollutants in surface soil samples of a crowded urban area in Tehran City is considered in this study. A total number of 112 samples were collected from pollution hotspots including gas stations, construction sites, bus terminal and waste recovery centers in summer 2016. Total, anthropogenic and bioavailable concentrations of metals, cadmium, cobalt, chromium, copper, manganese, nickel, lead and zinc, as well as ecological risk index (RI) values were calculated. Rather than Cd, the concentration of other metals was not remarkably different from reference values. The descending order of anthropogenic and bioavailable fractions in metals was proved to be as follows: Cd (87.87%) > Cr (40.14%) > Ni (38.64%) > Pb (37.40%) > Co (8.42%) > Cu (7.98%) > Zn (5.57%) > Mn (3.94%) and Cu (6.84%) > Zn (6.47%) > Pb (3.98%) > Ni (3.97%) > Cr (1.99%) > Cd (1.98%) > Mn (1.45%) > Co (1.39%), respectively. The results of the RI values also indicated that around 80% of total samples lie within a considerable ecological risk level. The total concentration of 16 EPA-approved PAHs was detected to be within the range of 0.62 and 3.51 mg/kg. The majority of PAHs detected in all samples was those with relatively higher molecular weights (higher number of aromatic rings). Accordingly, the major source of PAHs in surface soils was determined to be petroleum/gas combustion due to traffic loads and heating systems. The synergy observed in spatial distribution of toxic metals and PAHs confirms relatively identical pollution sources and at the same time exacerbates the adverse effects on human and ecological health.

Bioaccessibility-Based Risk Assessment of PAHs in Soils from Sites of Different Anthropogenic Activities in Lagos, Nigeria Using the Fed Organic Estimation Human Simulation Test Method

ABSTRACTThe aim of this study was to carry out a bioaccessibility-based risk assessment of polycyclic aromatic hydrocarbons (PAHs) in soils from sites of different anthropogenic activities in Lagos, Nigeria. Using an in vitro gastrointestinal model—Fed Organic Estimation Human Simulation Test method (FOREShT), the concentration of bioaccessible 16 priority US Environmental Protection Agency (USEPA) PAHs in soils were determined. Total concentration of 16 priority USEPA PAHs was also determined. The concentration range was 702–253,922 ng g−1 and 92–760 ng g−1 for total and bioaccessible PAHs, respectively. For persons involved with activities at these sites no health risks were observed, based on bioaccessibility values of PAHs. Mean daily intake of PAHs from these soils were below the oral mean daily intake threshold for PAHs in food. Also, overall estimated theoretical cancer risk (2.5 × 10−09, 6.5 × 10−07, 5.5 × 10−10, 2.7 × 10−09, 6.5 × 10−10, 9.5 × 10−10, 2.0 × 10−09, and 4.1 × 10−07 for the eight sites based on their bioaccessible concentration) for exposure to PAHs in surface soils were below the health guidelines for extreme (1 × 10−04) and normal (1 × 10−06) exposures.

Structural equation modeling of PAHs in ambient air, dust fall, soil, and cabbage in vegetable bases of Northern China

A series of field samples including ambient air (gaseous and particulate phases), dust fall, surface soil, rhizosphere soil and cabbage tissues (leaf, root and core), were collected in vegetable bases near a large coking manufacturer in Shanxi Province, Northern China, during a harvest season. A factor analysis was employed to apportion the emission sources of polycyclic aromatic hydrocarbons (PAHs), and the statistical results indicated coal combustion was the dominant emission source that accounted for different environmental media and cabbage tissues, while road traffic, biomass burning and the coking industry contributed to a lesser extent. A structural equation model was first developed to quantitatively explore the transport pathways of PAHs from surrounding media to cabbage tissues. The modeling results showed that PAHs in ambient air were positively associated with those in dust fall, and a close relationship was also true for PAHs in dust fall and in surface soil due to air-soil exchange process. Furthermore, PAHs in surface soil were correlated with those in rhizosphere soil and in the cabbage leaf with the path coefficients of 0.83 and 0.39, respectively. PAHs in the cabbage leaf may dominantly contribute to the accumulation of PAHs in the edible part of cabbages.

Temporal and spatial variations of polycyclic aromatic hydrocarbons (PAHs) in soils from a typical organic sewage irrigation area

In the water shortage countries and areas, untreated sewage irrigation led to the extensive organic pollution of farmland soil, which seriously threatened environmental security. In this study, we selected Shenfu irrigation area (SIA) as the study area, and it was the first and largest organic sewage irrigation area in China. We analyzed the temporal and spatial variations in concentrations, risk and sources of polycyclic aromatic hydrocarbons (PAHs) in soil of the SIA. The results show that the PAH concentrations decreased slowly and environmental risk fluctuated after stopping sewage irrigation. However, the correlation and divergence analysis indicate that PAHs in surface soils might be derived from traffic emissions besides sewage irrigation. Based on factor analysis with non-negative constraints, the contribution of irrigation decreased from 92.9% to 59.4%, and contribution of traffic increased from 7.1% to 40.6%. Thus, the superposition of the residual PAHs from sewage irrigation and the new input PAHs from traffic emission should be considered for the pollution control.

Contamination and health risk assessment of PAHs in soils and crops in industrial areas of the Yangtze River Delta region, China

This is the first investigation into both soil and crop contamination and associated health risks by polycyclic aromatic hydrocarbons (PAHs) in industrial areas of the Yangtze River Delta region (YRDR). Soil and crop samples were collected from farmland surrounded by three typical industries (a steelworks [SW], a petrochemical facility [PF] and a power plant [PP]), and the concentrations and health risks of PAHs in soils and crops were evaluated. The average concentrations of 16 USEPA priority PAHs in surface soil and subsoil were 471.30 μg kg−1 and 341.40 μg kg−1, respectively. The respective average concentrations of 16 PAHs in amaranth, spinach, Chinese chive, and rice tissues were 1710.49, 1176.96, 1218.36 and 352.12 μg kg−1. Based on both the results of a principal component analysis (PCA) and the PAH ratios, the main sources of the PAHs in soils were determined to be the combustion of coal and petroleum. The total values of incremental lifetime cancer risk (ILCR) for males induced by both soils and crops were 2.19 × 10−4, 2.53 × 10−4, and 9.17 × 10−4, and for females were 2.21 × 10−4, 2.50 × 10−4, and 9.68 × 10−4 for childhood, adolescence, and adulthood, respectively. Soils contaminated with PAHs posed a lower risk than crops, but the ILCR values, 4.40 × 10−5 and 3.82 × 10−5 for males and females, was still much higher than the baseline value. The results of this investigation provide novel information for contamination evaluation and human health risk assessment in PAH-contaminated sites.

Concentration and sources of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in surface soil near a municipal solid waste (MSW) landfill

Due to a continuous demand of land for infrastructural and residential development there is a public concern about the condition of surface soil near municipal solid waste landfills. A total of 12 surface (0–20cm) soil samples from a territory near a landfill were collected and the concentration of 16 PAHs and 7 PCB congeners were investigated in these samples. Limits of detection were in the range of 0.038–1.2μg/kg for PAHs and 0.025–0.041μg/kg for PCBs. The total concentration of ∑PAHs ranged from 892 to 3514μg/kg with a mean of 1974μg/kg. The total concentration of ∑PCBs ranged from 2.5 to 12μg/kg with a mean of 4.5μg/kg. Data analyses allowed to state that the PAHs in surface soils near a landfill were principally from pyrogenic sources. Due to air transport, PAHs forming at the landfill are transported outside the landfill. PCB origin is not connected with the landfill. Aroclor 1242 can be the source of PCBs in several samples.

Polycyclic aromatic hydrocarbons associated with total suspended particles and surface soils in Kunming, China: distribution, possible sources, and cancer risks.

The concentrations, distribution, possible sources, and cancer risks of polycyclic aromatic hydrocarbons (PAHs) in total suspended particles (TSPs) and surface soils collected from the same sampling spots were compared in Kunming, China. The total PAH concentrations were 9.35-75.01 ng/m(3) and 101.64-693.30 ng/g dry weight (d.w.), respectively, in TSPs and surface soils. Fluoranthene (FLA), pyrene (PYR), chrysene (CHR), and phenanthrene (PHE) were the abundant compounds in TSP samples, and phenanthrene (PHE), fluorene (FLO), fluoranthene (FLA), benzo[b]fluoranthene (BbF), and benzo[g,h,i]perylene (BghiP) were the abundant compounds in surface soil samples. The spatial distribution of PAHs in TSPs is closely related to the surrounding environment, which varied significantly as a result of variations in source emission and changes in meteorology. However, the spatial distribution of PAHs in surface soils is supposed to correlate with a city's urbanization history, and high levels of PAHs were always observed in industry district, or central or old district of city. Based on the diagnostic ratios and principal component analysis (PCA), vehicle emissions (especially diesel-powered vehicles) and coal and wood combustion were the main sources of PAHs in TSPs, and the combustion of wood and coal, and spills of unburnt petroleum were the main sources of PAHs in the surface soils. The benzo[a]pyrene equivalent concentration (BaPeq) for the TSPs and surface soil samples were 0.16-2.57 ng/m(3) and 11.44-116.03 ng/g d.w., respectively. The incremental lifetime cancer risk (ILCR) exposed to particulate PAHs ranged from 10(-4) to 10(-3) indicating high potential of carcinogenic risk, and the ILCR exposed to soil PAHs was from 10(-7) to 10(-6) indicating virtual safety. These presented results showed that particle-bound PAHs had higher potential carcinogenic ability for human than soil PAHs. And, the values of cancer risk for children were always higher than for adults, which demonstrated that children were sensitive to carcinogenic effects of PAHs.

Distribution, sources and potential toxicological significance of polycyclic aromatic hydrocarbons (PAHs) in surface soils of the Yellow River Delta, China

PAH concentrations of 61 surface soil samples collected from the Yellow River Delta (YRD), China were measured to determine occurrence levels, sources, and potential toxicological significance of PAHs. The total concentrations of ∑PAHs ranged from 27 to 753ng/g d.w., with a mean of 118±132ng/g. The highest concentrations was found in the mid-southern part of the YRD (753ng/g), which was associated with the oil exploration. The ratios indicated that the PAHs throughout the YRD were mostly of pyrogenic origin; while various sites in mid-southern part in the region were derived mainly from the petrogenic sources. Multivariate statistical analyses supported that the PAHs in surface soils of the YRD were principally from the coal and biomass combustion, petroleum spills, and/or vehicular emissions. The toxic assessment suggested that the PAHs in soils were at low potential of ecotoxicological contamination level for the YRD.

Polycyclic Aromatic Hydrocarbons in Surface Soils of Kunming, China: Concentrations, Distribution, Sources, and Potential Risk

The concentrations, distribution, possible sources, and potential risk of polycyclic aromatic hydrocarbons (PAHs) in surface soils were studied in Kunming, which is situated in a lake basin of the Yunnan-Guizhou plateau. 15 PAHs were analyzed in 40 surface soil samples (0–5 cm layer) collected from six types of land uses in the Kunming urban area. Meanwhile, the potential sources of PAHs in surface soils of Kunming were investigated by PAH composition ratios, isomer ratios, and principal component analysis (PCA). The total concentrations of 15 PAHs ranged from 101.64 to 6,208.25 ng/g (dry weight basis). The concentrations in different land uses increased in an order as: green space (541.43 ng/g) < education area (756.49 ng/g) < business area (810.17 ng/g) < residential area (1,034.36 ng/g) < industrial area (1,166.79 ng/g) < roadside greens (2,146.76 ng/g). The results of sources identification suggested that PAHs in surface soils of the Kunming urban area were greatly affected by combustion activities which came mainly from coal combustion and vehicular traffic. In addition, the toxic equivalency factors (TEFs) were used to estimate benzo[a]pyrene-equivalent concentration in surface soils of Kunming, and the risk level of PAHs in Kunming's urban surface soils was low as a whole.

Polycyclic Aromatic Hydrocarbons in Urban Street Dust and Surface Soil: Comparisons of Concentration, Profile, and Source

Street dust and surface soil samples in urban areas of Dalian, a coastal city in Liaoning Province, China, were collected and analyzed for 25 polycyclic aromatic hydrocarbons (PAHs). The concentrations, distribution, and sources of PAHs in dust and soil were determined. The concentrations of total PAHs in street dust ranged between 1890 and 17,070 ng/g (dry weight), with an average of 7460 ng/g, whereas the concentrations of total PAHs in surface soil varied greatly, from 650 to 28,900 ng/g, with a mean value of 6440 ng/g. Statistical paired t-test confirmed that total PAH concentrations have no significant difference between street dust and surface soil. Mean PAH concentrations in two type samples were much higher at industrial sites than at business/residential or garden sites. PAHs were dominated by higher molecular weight PAH (4- to 6-ring) homologues, which accounted for about 73% and 72% of total PAHs in street dust and surface soil, respectively. Principal component analysis was used in source apportionment of PAHs in dust and soil. Pyrogenic and petrogenic sources contributed 70% and 22.4% of total PAHs in street dusts, and fossil fuel (coal and petroleum) and biomass combustion accounted for 64.4% and 5.6% of total PAHs in pyrogenic sources, respectively. In surface soil, total PAHs were dominated by pyrogenic sources. The diagnostic ratios of benz[a]anthracene/chrysene confirmed that PAHs in street dust and surface soil of a Dalian urban zone might come mostly from the emission of local sources.

Polycyclic aromatic hydrocarbons and polychlorinated biphenyls in urban soils from Kathmandu, Nepal

Kathmandu, the capital of Nepal, faces increasing environmental problems such as heavy air pollution and lack of proper waste management. The aim of this study was to examine if the soils are also affected by pollution, with the focus on polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). The sum of 20 PAHs in surface soils ranged between 184 and 10279 μg kg −1. The most abundant PAHs were perylene (14.6%), benzo( b+ j+ k)flouranthene (10.7%), naphthalene (10.7%) and phenanthrene (9.8%), with perylene concentrations varying strongly. The significantly more positive δ 13C values of perylene in samples with elevated concentrations indicate biological production, possibly by anaerobic degradation of perylene quinones. PAH ratios also indicate the influence of petrogenic PAH sources, especially at petrol stations and some street samples. The sum of 12 PCBs ranged from 356 to 44710 ng kg −1. The most abundant were congeners 52 (19.4%), 101 (14.3%), 118 (13.4%) and 138 (11.7%). The low PCB concentrations and pattern were interpreted as a diffuse background contamination being the main PCB source in the urban soils. Indications for recent contamination were found in river sediments from the inner city, as well as in industrial and street samples. Classified by land use, the samples taken from the gutter contained the highest PAH and PCB concentrations as a result of accumulation. The lowest values were found in surface soils from Swayambunath (a park) and a garden area. A gradual decrease in concentration with depth was present for both compound classes in the profiles sampled at Swayambunath. No trend was visible in the garden profiles as a result of soil disturbance of the soil by agricultural treatment. Enhanced microbial degradation and volatilization in the warm/humid monsoon climate is probably the main cause for low pollutant concentrations. Increased photodegradation and the short accumulation period might be other important factors. Concerning its state of soil pollution, Kathmandu fits rather well into a global distribution pattern of persistent organic pollutants, with high concentrations in temperate (higher latitude) regions and very low ones in the tropics (lower latitude regions) due to global distillation.

Distribution of PAHs in Surface Soils from Petroleum Handling Facilities in Calabar

The level of concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface soils from petroleum handling facilities (kerosene tank, generating plant, petrol stations, mechanic workshops, leaking pipeline and air port fuel dump) from Calabar metropolis southeastern Nigeria was determined by gas chromatography/ mass spectrometry. The results show that total polycyclic aromatic hydrocarbons (PAHs) varied from 1.80 to 334.43 mg/kg with a mean of 50.31 mg/kg. The lowest value of 1.80 mg/kg was obtained from petrol station while the highest value of 334.43 mg/kg was obtained from facility characterised by petrol stations and mechanic workshops. The ratio of phenanthrene/anthracene and fluoranthene/pyrene, varied from 0.43 to 27.72 and from 0.14 to 17.76 respectively. These ratios indicate various sources for the PAH. The two to three ring PAHs are the most abundant. Based on the PAH ratios and content alone it is not possible to distinguish between contribution from motor vehicle exhaust, gasoline spillage, used engine oil or petroleum production. However, considering the area of the study, it is very likely that the major source of soil contamination is originating from petroleum product.

Survey of the distribution and sources of PAHs in urban surface soils

It has long been recognized that urban surface soils contain various amounts of polycyclic aromatic hydrocarbons (PAHs). Several studies in the US and Europe have indicated that the concentrations of PAHs in surface soils can range from the low parts per billion to hundreds of parts per million depending on the proximity to and contribution from PAH sources. This paper presents the results of a study of PAHs in urban surface soil in the United States. The study was a collaborative effort between EPRI, seven electric utilities, META Environmental, Inc., the state environmental agencies in New York, Illinois, and Pennsylvania, and many municipalities. Surface soil samples from 319 sites in 29 population centres in three states were collected and analysed for PAHs. Site selection was conducted using a pseudo-random sampling scheme. The samples were collected from 0 to 15.2 cm (0 to 6 inches). At some locations, samples were collected from two depths, 0 to 2.54 cm and 2.54 to 15.2 cm. The samples were analysed for 43 PAHs and alkylated PAHs by GC/MS. The concentrations of total PAHs ranged from 84 µg/kg to 147 000 µg/kg with an average concentration of 7330 µg/kg total PAHs and a median concentration of 1960 µg/kg. All 43 PAHs were detectable in most samples above a detection limit of 5 µg/kg; however, PAH concentrations were dominated by a few high molecular weight parent compounds. EPA residential risk based concentrations (RBCs) were exceeded for one or more compounds in more than 60% of the samples tested.