Polycyclic Aromatic Hydrocarbons Concentrations In Soil Research Articles

Distribution and risks of polycyclic aromatic hydrocarbons in suburban and rural soils of Beijing with various land uses.

We investigated the sources, distribution, and health risks of polycyclic aromatic hydrocarbons (PAHs) in soils of peri-urban Beijing. The mean concentrations of total 16 PAHs in suburban and rural soils of Beijing were 321.8 ± 408.2 and 219.2 ± 233.5ng/g, respectively. The PAH concentrations decreased along the urban-suburban-rural gradient and varied with land use categories. The industrial areas had the highest soil PAH concentrations followed by the living areas, roadsides, green areas, and agricultural areas. The major sources of PAHs in these soils were coal and biomass combustion. Traffic emission was not the dominant source of PAHs in peri-urban Beijing. At a few sites, high soil PAH contents were caused by point sources such as iron and steel plants and a wood preservative factory. The incremental lifetime cancer risks (ILCRs) of adults and children exposed to PAHs in the soils were acceptable. However, cautions should be paid to the abandoned industrial sites, which might be converted to residential area during the urbanization process.

Assessment of polycyclic aromatic hydrocarbons (PAHs) contamination in surface soil of coal stockpile sites in South Kalimantan, Indonesia.

Concentrations, spatial distribution, and sources of 16 polycyclic aromatic hydrocarbons (PAHs), listed as priority pollutants by the United States Environmental Protection Agency (USEPA), were investigated in surface soils of three different coal stockpile, agricultural, and residential sites in South Kalimantan Province, Indonesia. Total PAHs concentration ranged from 4.69 to 22.67 mg kg(-1)-dw. PAHs concentrations in soil of coal stockpile sites were higher than those in agricultural and residential soil. A complex of petrogenic origin and pyrolytic sources was found within the study area, as suggested by the isomeric ratios of PAHs. The results of principal component analysis and multiple linear regressions (PCA/MLR) showed that three sources contributed to the PAHs in the study area, including biomass and coal combustion (48.46%), raw coal (35.49%), and vehicular emission (16.05%). The high value of total benzo[a]pyrene equivalent concentration (B[a]Peq) suggests that local residents are exposed to a high carcinogenic potential.

Photodegradation of polycyclic aromatic hydrocarbons in soils under a climate change base scenario

The photodegradation of polycyclic aromatic hydrocarbons (PAHs) in two typical Mediterranean soils, either coarse- or fine-textured, was here investigated. Soil samples, spiked with the 16 US EPA priority PAHs, were incubated in a climate chamber at stable conditions of temperature (20 °C) and light (9.6 W m−2) for 28 days, simulating a climate change base scenario. PAH concentrations in soils were analyzed throughout the experiment, and correlated with data obtained by means of Microtox® ecotoxicity test. Photodegradation was found to be dependent on exposure time, molecular weight of each hydrocarbon, and soil texture. Fine-textured soil was able to enhance sorption, being PAHs more photodegraded than in coarse-textured soil. According to the EC50 values reported by Microtox®, a higher detoxification was observed in fine-textured soil, being correlated with the outcomes of the analytical study. Significant photodegradation rates were detected for a number of PAHs, namely phenanthrene, anthracene, benzo(a)pyrene, and indeno(123-cd)pyrene. Benzo(a)pyrene, commonly used as an indicator for PAH pollution, was completely removed after 7 days of light exposure. In addition to the PAH chemical analysis and the ecotoxicity tests, a hydrogen isotope analysis of benzo(a)pyrene was also carried out. The degradation of this specific compound was associated to a high enrichment in 2H, obtaining a maximum δ2H isotopic shift of +232‰. This strong isotopic effect observed in benzo(a)pyrene suggests that compound-specific isotope analysis (CSIA) may be a powerful tool to monitor in situ degradation of PAHs. Moreover, hydrogen isotopes of benzo(a)pyrene evidenced a degradation process of unknown origin occurring in the darkness.

Polycyclic Aromatic Hydrocarbons in Road-Deposited Sediments and Roadside Soil in Tijuana, Mexico

ABSTRACTRoad-deposited sediment and roadside soil in the urban area of the city of Tijuana were collected and analyzed for 16 polycyclic aromatic hydrocarbons (PAHs). The ΣPAH concentration for road-deposited sediment (RDS) ranged between 460 and 2027 µg/kg with an average of 933 µg/kg. The ΣPAH concentration in roadside soil was lower than in RDS, with a range between 54 and 1863 µg/kg and a mean value of 308 µg/kg. The diagnostic ratios showed that the PAHs originated mostly from pyrogenic sources such as gasoline and diesel combustion. The results show that PAH concentration in RDS and roadside soils is low when compared with other published studies. The low PAH levels found in this study are possibly related to differences in climate, urban features, and anthropogenic activities conducted in the studied areas. The toxicity equivalent concentrations (TEQ) of PAH calculated were also low in comparison with other studies. This is probably due to the lower concentration of total PAHs and the highly toxic high-molecular-weight PAHs.

Are physico-chemical soil characteristics key factors to select the polycyclic aromatic hydrocarbons extraction procedure?

ABSTRACTThe aim of this work was to assess the impact of soil characteristics and constituents in the total extraction of hydrophobic organic pollutants, such as polycyclic aromatic hydrocarbons (PAH), in real polluted soil samples from different sources. Soil samples were obtained from a wood creosote treatment plant, in the vicinity of a metallurgy industry and coal thermal power stations. Soils showed a wide diversity of textures, organic matter (OM) and CaCO3 content, pH and electrical conductivity to assure representativeness of multiple situations. Two extraction procedures with soft (solid–liquid extraction, SLE) and intense (pressurised liquid extraction, PLE) extraction power were used to determine the total concentration of PAH in soils. Results obtained showed that soil properties affect the effectiveness of the extraction procedures tested. The validation of PAH extraction procedure with a reference soil did not confirm that the procedure was adequate for all kinds of soil. Results showed that OM content and clay were the main soil characteristics that should be taken into account to select the most adequate PAH extraction procedure for any given polluted soil.

Bioremediation of creosote contaminated soil in both laboratory and field scale: Investigating the ability of methyl-β-cyclodextrin to enhance biostimulation

We investigated the bioremediation of 16 polycyclic aromatic hydrocarbons (PAH) in historically creosote contaminated soil using both laboratory and field scale experiments. We found that nutrient amendments and circulation of methyl-β-cyclodextrin (CD) solution enhanced soil microbial degradation capacity. In the laboratory experiment, the degradation of lower molecular weight, 2–3 ringed PAHs was achieved already by circulating nutrient solution and the use of CD mainly increased the desorption and removal of larger, 4–5 aromatic ringed PAH compounds. The 1% CD concentration was most feasible for bioremediation as most of the extracted PAH compounds were degraded. In the 5% CD treatment, the PAH desorption from soil was too fast compared to the degradation capacity and 25% of the total PAH amount remained in the circulated solution. Similar lab-scale results have been generated earlier, but very little has been done in full field scale, and none in freezing conditions. Although freezing stopped circulation and degradation completely during the winter, PAH degradation returned during the warm period in the field test. Circulation effectiveness was lower than in the laboratory but the improved nutrient and moisture content seemed to be the main reason for decreasing soil PAH concentrations. It also appeared that PAH extraction yield in chemical analysis was increased by the CD treatment in field conditions and the results of CD-treated and non-treated soil may therefore not be directly comparable. Therefore, a positive effect of CD on PAH degradation velocity could not be statistically confirmed in the field test. Based on our results, we recommend initiating the bioremediation of PAH contaminated soil by enhancing the microbial degradation with nutrient amendments. The CD seems to be useful only at the later stage when it increases the solubilisation of strongly absorbed contaminants to some extent. More investigation is also needed of the CD effect on the PAH yield in the chemical analysis.

Determination of Polycyclic Aromatic Hydrocarbons (PAHs) on Selected Dumpsites in Abeokuta Metropolis, SW, Nigeria

Knowledge of the concentration of polycyclic aromatic hydrocarbon (PAHs) in urban soils remains insufficient in developing countries like Nigeria despite their toxic effects and suspected human carcinogens, mutagens and endocrine disruption. This study aimed to determine the concentration of PAHs in soil of three dumpsites in Abeokuta metropolis, Ogun State, Nigeria. Concentrations of individual PAHs were determined using Gas Chromatography Flame Ioni-zation Detector (GC-FID). The total PAHs concentrations at 0-15 cm depth were 29.0 mg kg-1, 41.6 mg kg-1 and 11.9 mg kg-1 for Igbore, Saje and Alogi dumpsites respectively while the corres-ponding total PAHs concentrations at 15-30 cm depth were 9.3 mg kg-1, 28.3 mg kg-1 and 11.0 mgkg-1respectively. These concentrations were slightly lower than the Dutch guideline limits of 40 mg kg-1 except for that of Saje at 0-15 cm depth. The amounts of fluoranthene at Igbore dumpsite in the two depths were 23.64 mg kg-1 and 8.02 mg kg-1, with a total sum of 10 PAHs compounds of 19.12 mg kg-1. The results showed that the highest concentration of a single PAHs compound was at Saje dump-site with fluoranthene value of 33.75 mg kg-1 and 22.74 mg kg-1 at the depths of 0-15 and 15-30 cm respectively. Isomer ratio for fluoranthene/pyrene was 2.69 at Alogi dumpsite, which suggested that the PAHs were from pyrogenic sources. Carcinogenic PAHs constituted about 1.29-15.69 % of the total PAHs detected in the dumpsite raising concerns of human exposure through the food chain.

Plant responses to a phytomanaged urban technosol contaminated by trace elements and polycyclic aromatic hydrocarbons.

Medicago sativa was cultivated at a former harbor facility near Bordeaux (France) to phytomanage a soil contaminated by trace elements (TE) and polycyclic aromatic hydrocarbons (PAH). In parallel, a biotest with Phaseolus vulgaris was carried out on potted soils from 18 sub-sites to assess their phytotoxicity. Total soil TE and PAH concentrations, TE concentrations in the soil pore water, the foliar ionome of M. sativa (at the end of the first growth season) and of Populus nigra growing in situ, the root and shoot biomass and the foliar ionome of P. vulgaris were determined. Despite high total soil TE, soluble TE concentrations were generally low, mainly due to alkaline soil pH (7.8-8.6). Shoot dry weight (DW) yield and foliar ionome of P. vulgaris did not reflect the soil contamination, but its root DW yield decreased at highest soil TE and/or PAH concentrations. Foliar ionomes of M. sativa and P. nigra growing in situ were generally similar to the ones at uncontaminated sites. M. sativa contributed to bioavailable TE stripping by shoot removal (in g ha(-1) harvest(-1)): As 0.9, Cd 0.3, Cr 0.4, Cu 16.1, Ni 2.6, Pb 4, and Zn 134. After 1 year, 72 plant species were identified in the plant community across three subsets: (I) plant community developed on bare soil sowed with M. sativa; (II) plant community developed in unharvested plots dominated by grasses; and (III) plant community developed on unsowed bare soil. The shoot DW yield (in mg ha(-1) harvest(-1)) varied from 1.1 (subset I) to 6.9 (subset II). For subset III, the specific richness was the lowest in plots with the highest phytotoxicity for P. vulgaris.

The influence of various biochars on the bioaccessibility and bioaccumulation of PAHs and potentially toxic elements to turnips (Brassica rapa L.)

The influence of amending a contaminated soil with different dry-pyrolyzed biochars on the bioaccessibility and biouptake of polycyclic aromatic hydrocarbons (PAH) and potentially toxic elements (PTE) in turnip (Brassica rapa L.,) was investigated. This is the first study to examine the influence of biochar amendments on turnips grown in a contaminated soil. The biochars came from different local feedstocks, including sewage sludge biochar (SSBC), soybean straw biochar (SBBC), rice straw biochar (RSBC) and peanut shell biochar (PNBC). The biochars were applied to soil at 2% and 5% amendments, and the resulting influence on various soil and porewater properties were quantified. The bioaccessible concentrations of PAHs in soil and their bioaccumulation in B. rapa L. significantly (P<0.05) decreased in the biochar amended soils. Biochar additions significantly (P≤0.05) reduced the bioaccumulation of PTEs (As, Cd, Cu, Pb and Zn) in B. rapa L, though not as much as for PAHs. The most effective biochar at reducing both PAHs and PTEs was PNBC (P≤0.05). Amendments of 5% biochar were more effective at reducing contaminant bioaccessibility than amendments at 2% (P<0.05). Crop yield, however, increased the most for the 2% biochar amendments, in particular for SSBC (with a 49% increase in crop yield compared to the non-amended soil). Therefore, which biochar would be the most advantageous in this system would require a cost-benefit analysis between increasing crop yield (best achieved with 2% SSBC amendments) and decreasing the PAH and PTE uptake (best achieved with 5% PNBC amendments).

Polycyclic aromatic hydrocarbons in soils from urban to rural areas in Nanjing: Concentration, source, spatial distribution, and potential human health risk

Polycyclic aromatic hydrocarbons (PAHs) have become a major type of pollutant in urban areas and their degree of pollution and characteristics of spatial distribution differ between various regions. We conducted a comprehensive study about the concentration, source, spatial distribution, and health risk of 16 PAHs from urban to rural soils in Nanjing. The mean total concentrations of 16 PAHs (∑16PAHs) were 3330ngg−1 for urban soils, 1680ngg−1 for suburban soils, and 1060ngg−1 for rural soils. Five sources in urban, suburban, and rural areas of Nanjing were identified by positive matrix factorization. Their relative contributions of sources to the total soil PAH burden in descending order was coal combustion, vehicle emissions, biomass burning, coke tar, and oil in urban areas; in suburban areas the main sources of soil PAHs were gasoline engine and diesel engine, whereas in rural areas the main sources were creosote and biomass burning. The spatial distribution of soil PAH concentrations shows that old urban districts and commercial centers were the most contaminated of all areas in Nanjing. The distribution pattern of heavier PAHs was in accordance with ∑16PAHs, whereas lighter PAHs show some special characteristics. Health risk assessment based on toxic equivalency factors of benzo[a]pyrene indicated a low concentration of PAHs in most areas in Nanjing, but some sensitive sites should draw considerable attention. We conclude that urbanization has accelerated the accumulation of soil PAHs and increased the environmental risk for urban residents.

Potential bioavailability of lead, arsenic, and polycyclic aromatic hydrocarbons in compost-amended urban soils.

Urban soils may contain harmful concentrations of contaminants, such as lead (Pb), arsenic (As), and polycyclic aromatic hydrocarbons (PAHs), that can transfer from soil to humans via soil ingestion and consumption of food crops grown in such soils. The objective of this research was to assess the effectiveness of adding different compost types to reduce both direct (soil-human) and indirect (soil-plant-human) exposure of Pb, As, and PAHs to humans. A field experiment was conducted in 2011 and 2012 at an urban garden site with elevated concentrations of Pb (475 mg kg), As (95 mg kg), and PAHs (23-50 mg kg). Soil amendments were composted biosolids, noncomposted biosolids, mushroom compost, leaf compost, and a nonamended control. Collard greens, tomatoes, and carrots were then grown in the amended and nonamended soils and nonamended soils that received urea in 2011. At the beginning of the second season, N-P-K fertilizer was added to all plots. The potential for direct and indirect exposure was evaluated. Soil Pb bioaccessibility was 1 to 4.3%, and As bioaccessibility was 7.3 to 12.3%. Composted biosolids reduced the bioaccessibility of soil Pb by ∼17% compared with the control but temporarily increased the bioaccessibility of As by ∼ 69% compared with the control when soluble inorganic P concentration in soil was elevated by P fertilizer application in 2012. The bioaccessibility of soil Pb decreased by ∼38% in all treatments when soluble inorganic P concentration in soil was elevated by P fertilizer. Compost amendments reduced the concentrations of low molecular weight PAHs in soil. Regardless of the treatments, the concentrations of Pb, As, and PAHs measured in the vegetables were low or nondetectable, except for Pb in carrots. Consumption of vegetables grown at this site will cause insignificant transfer of Pb, As, and PAHs to humans.

Source of polycyclic aromatic hydrocarbon in roadway and stormwater system maintenance residues

Soil and sediments adjacent to roadways often contain elevated concentrations of polycyclic aromatic hydrocarbons (PAHs). The sources of these PAH compounds include atmospheric deposition from automobile emissions and abraded bituminous asphalt particles from paved roads. Research was conducted to evaluate the relative contribution of each source on PAH concentrations in roadway-impacted soil and sediments by examining size fractionation and associated PAH content in roadway and stormwater system residuals. Analysis of five fractions ( 425 μm) of roadway and storm system residuals yielded varied results among the samples. The total PAH concentrations in the fractions ranged from 45 to 24,800 μg/kg with PAHs being most often encountered in the fine ( 425 μm size fractions were 1070–21,100, 609–24,800, 185–22,500, 110–16,900, and 45–7730 μg/kg, respectively. The highest concentration of individual PAH detected in the size fractions was benzo(g,h,i)perylene (6050 μg/kg) in one catch basin sediment sample. Although abraded asphalt particles from roadways were likely a source of PAHs in the coarse fractions, the predominance of PAH in the fine or median coarse size fractions suggests that other pathways such as atmospheric deposition from vehicle emissions are the major contributor. Additionally, calculated ratios between selected PAH analogs with molecular masses 178, 202, 228 and 276 also support the inference that atmospheric deposition from combustion is a major source of PAHs.

Polycyclic aromatic hydrocarbons (PAHs): contamination level and risk assessment in urban areas, Kuala Lumpur, Malaysia

We are reporting the distribution of 15 polycyclic aromatic hydrocarbons (PAHs) in roadside soils and road dusts of five industrial areas around Kuala Lumpur city, namely Chan Saw Lin, Kuchai, Segambut, Kepong-1, and Kepong-2 using GC-MS and assessing their toxicological risk. The total PAH concentrations of PAHs in roadside soils of the industrial areas ranged from 2804 ± 2645 μg/kg (Kepong-2) to 18384 ± 12324 μg/kg (Chan Saw Lin), while for the road dusts, it ranged from 3056 ± 1929 μg/kg (Kepong-2) to 13581 ± 5295 μg/kg (Segambut). High molecular weight PAHs dominated the distribution of PAHs in all sampling locations for roadside soils and in road dust except for road dust of the Segambut industrial areas. Result of isomeric pair ratios and PCA used for the identification of the PAHs sources, suggested that the contribution of petrogenic sources is greater than the pyrogenic sources in almost all studied locations. Total B[a]Peq for roadside soils and road dusts of studied areas, recorded highest in Chan Saw Lin and lowest in Kepong-2. Cancer risks caused by a long-period exposure to the PAHs in roadside soils of studied areas are still considered very low.

Effect of input pathways and altitudes on spatial distribution of polycyclic aromatic hydrocarbons in background soils, the Tibetan Plateau.

Limited data on the spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in Tibetan soils have been reported. This study measured the concentrations of PAHs in background soils across Tibet including 44 surface soils (0-10 cm) and 14 subsurface soils (10-20 cm) and assessed the effect of input pathways and altitudes on spatial distribution of PAHs. The concentrations of 15 US EPA priority PAHs (∑15-PAHs, naphthalene excluded) in all surface soils ranged from 1.50 to 29.88 ng/g dry weight with a mean concentration of 6.09 ng/g. The levels of PAHs in soils from southeast of Tibet were higher than those from northwest, which might be attributed to both more local emission as a result of relative higher population density and contributions of long-range atmosphere transport (LRAT) processes from Indian subcontinent in the south and Sichuan in the east. For the northwest Tibet, the westerly wind originated from the western boundaries between India and Nepal but not local emission might play an important role in input of PAHs, since there were slight anthropogenic activities. A general decrease of ∑15-PAHs with depth suggested their atmospheric input, while surface runoff might also play an important role in input of PAHs to soils from canyon and valley. The abundances of more volatile three-ring PAHs positively correlated with altitudes while less volatile ones unrelated (four rings) or inversely correlated (five and six rings) with altitudes, indicating cold condensation effect. The results of PAH isomer ratios suggested mixed sources of petroleum evaporation and combustion of petroleum and biomass.

Biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) by Trichoderma reesei FS10-C and Effect of Bioaugmentation on an Aged PAH-Contaminated Soil

ABSTRACT The co-metabolism of benzo[a]pyrene (B[a]P) and the capacity of the fungus Trichoderma reesei FS10-C to bioremediate an aged polycyclic aromatic hydrocarbon (PAH)-contaminated soil were investigated. The fungal isolate removed about 54% of B[a]P (20 mg L−1) after 12 days of incubation with glucose (10 g L−1) supplementation as a co-metabolic substrate. Bioaugmented microcosms showed a 25% decrease in total PAH concentrations in soil after 28 days, and the degradation percentages of 3-, 4-, and 5(+6)-ring PAHs were 36%, 35%, and 25%, respectively. In addition, bioaugmented microcosms exhibited higher dehydrogenase (DHA) and fluorescein diacetate hydrolysis (FDAH) activities and increased average well-color development (AWCD), Shannon-Weaver index (H), and Simpson index (D) significantly. Principal component analysis (PCA) also distinguished clear differentiation between treatments, indicating that bioaugmentation restored the microbiological function of the PAH-contaminated soil. The results suggest that bioaugmentation by T. reesei FS10-C might be a promising bioremediation strategy for aged PAH-contaminated soils.

Biodegradation of Polycyclic Aromatic Hydrocarbons in Agricultural Soil Contaminated with Crude Oil from Nigeria Refinery using leurotus sajor-caju

Contamination by petroleum hydrocarbons has rendered soil from oil exploring areas in Nigeria unwholesome for agricultural practices. Because of the carcinogenic properties of the contaminant, its removal from soil is therefore an absolute necessity to promote a sustainable development for society and sound human health. Thus, a rapid cost effective method of biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) using Pleurotus sajor-caju was employed. Soil samples were collected from agricultural sites in Akpan town near Nigerian refineries and were analysed for sixteen PAHs by Gas Chromatography (GC). The total PAHs concentrations ranged from 56.8 to 112 mg kg-1. Using the ratios of phenanthrene to anthracene (Phe/Ant) and fluoranthene to pyrene (Flu/Pyr) to identify sources of contamination, PAHs concentrations in Akpan soils possibly had pyrogenic and petrogenic sources. These sources included crude oil petroleum combustion and spills. Pleurotus Sajor-Cajor offered significant reduction in PAHs concentrations after 6 weeks of incubation.

국내 토지이용도별 토양 중 다환방향족탄화수소류(PAHs)의 농도 수준 및 분포 특성

We investigated soil contamination depending on the land use by examining the contamination levels and distribution characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in the national soil. Total PAHs (the sum of 16 PAH concentrations) and carcinogenic PAHs (the sum of seven carcinogenic PAH concentrations) were 8.50~3,437.16 µg/kg and 2.94~2,136.96 µg/kg, respectively. The concentration of benzo(a)pyrene, one of the contaminants regulated by the soil quality standard in the nation, was ND~924.73 µg/kg. Its maximum value of 924.73 µg/kg was detected in railroad (Region 3) and is approximately 13% of the standard value for Region 3 (i.e., 7 mg/kg). We also investigated the characteristics of contamination sources of PAHs in soil of the upland, forests, roads, and railroads, examining the fraction distribution of PAHs concentration by the number of benzene rings against the total PAHs concentration. The results demonstrate that the mean fraction of 4~6-ring PAHs against total PAHs concentration in soil was in the range of 51.8~80.7% with relative abundance of high-molecular PAHs, showing that the origin of contamination is under the category of combustion sources. When the molecular indices (Flu/(Flu/Pyr), Ant/(Ant+Phe), InP/(InP+BP), and BaA/ (BaA+Chr)) were applied, they were also categorized as petroleum-based combustion sources. The individual PAH concentrations in soil by the land use were grouped into Regions 1, 2, and 3, which are statistically treated and are the parts of the national category system of soil quality standard. As a result, the concentration level of 16 PAHs was 0.02~2.63 µg/kg in Region 1, 0.05~4.26 µg/kg in Region 2, and 2.36~178.27 µg/kg in Region 3. The concentration level of 6 carcinogenic PAHs was 14.2~320.4% against that of benzo(a)pyrene in Region 3 and sites of recycling waste sleepers. Considering that there were similarities among PAHs in terms of structures and toxicities, it would be recommended to review other types of carcinogenic PAHs together with benzo(a)pyrene when developing the soil quality standards in the nation.

Identification of polycyclic aromatic hydrocarbons in soils in Taizhou, East China.

Polycyclic aromatic hydrocarbons (PAHs) and their hazards in surface soil (n=92) were investigated in Taizhou, China, which is an area in East China famous for production and exporting of rice. Total concentrations of PAHs in soils ranged from 2.3×10(1) to 7.6×10(2) with a mean of 1.8×10(2)μg/kg (dry mass; dm). Concentrations of 16 PAHs reported here were less than those observed in most previous studies in China and other countries. Concentrations of individual PAH in fluvo-aquic soils were greater than those in paddy soils except naphthalene. Fluoranthene and pyrene were dominant PAHs, which accounted for 19.7 and 13.3% of the total mass of PAHs, respectively. Based on ratios of low molecular weight PAHs to high molecular weight PAHs, diagnostic ratios and principal component analysis, the predominant source of PAHs was combustion and pyrolysis, especially coal, natural gas, gasoline and diesel emissions from traffic, as well as burning of straw. Carcinogenic potencies of 13 samples were 1.1- to 2.9-fold greater than the target values promulgated by the Netherlands, indicating increased carcinogenic risks of soils from these sites. However, risks of cancer via accidental ingestion, dermal absorption and inhalation to humans posed by PAHs in soil were relatively small.

Occurrence, distribution, sources and toxic potential of polycyclic aromatic hydrocarbons (PAHs) in surface soils from the Kumasi Metropolis, Ghana

As a developing country, the economic and population growth rates in Ghana over the past few years have seen a tremendous increase. The growing rate of industrialization is gradually leading to contamination and deterioration of the environment and pollution is likely to reach disturbing levels. Surface soil samples were collected randomly from 36 communities in the Kumasi Metropolis, Ghana, to determine the concentrations, distribution, sources and toxic potential of emission of polycyclic aromatic hydrocarbons (PAHs) since no such comprehensive study had been conducted. The mean concentration of total PAHs in the surface soils in each community ranged from 14.78 at Ahinsan to 2084ng/g dry weight at Adum with an average of 442.5±527.2ng/g dry weight. Diagnostic ratios and chemical mass balance models of the results showed that PAHs in surface soil samples from the study area were mainly from fuel combustion. Carcinogenic potency of PAH load from the city centre was approximately 150 times higher as compared to a pristine site, Kwame Nkrumah University of Science and Technology's Botanical Garden. BaP, a human carcinogen, contributed 70% of the total PAHs toxicity level from the city centre of Kumasi.

Occurrence, sources, and potential human health risks of polycyclic aromatic hydrocarbons in agricultural soils of the coal production area surrounding Xinzhou, China

A comprehensive investigation of the levels, distribution patterns, and sources of polycyclic aromatic hydrocarbons (PAHs) in agricultural soils of the coal production area surrounding Xinzhou, China, was conducted, and the potential human health risks associated with the levels observed were addressed. A total of 247 samples collected from agricultural soils from the area were analyzed for sixteen PAHs, including highly carcinogenic isomers. The PAH concentrations had a range of n.d. to 782ngg−1, with a mean value of 202ngg−1. The two–three ring PAHs were the dominant species, making up 60 percent of total PAHs. Compared with the pollution levels and carcinogenic potential risks reported in other studies, the soil PAH concentrations in the study area were in the low to intermediate range. A positive matrix factorization model indicates that coal/biomass combustion, coal and oil combustion, and coke ovens are the primary PAH sources, accounting for 33 percent, 26 percent, and 24 percent of total PAHs, respectively. The benzo[a]pyrene equivalent (BaPeq) concentrations had a range of n.d. to 476ngg−1 for PAH7c, with a mean value of 34ngg−1. The BaPeq concentrations of PAH7c accounted for more than 99 percent of the ∑PAH16, which suggests that seven PAHs were major carcinogenic contributors of ∑PAH16. According to the Canadian Soil Quality Guidelines, only six of the soil samples had concentrations above the safe BaPeq value of 600ngg−1; the elevated concentrations observed at these sites can be attributed to coal combustion and industrial activities. Exposure to these soils through direct contact probably poses a significant risk to human health as a result of the carcinogenic effects of PAHs.