Spatial distribution of PAHs in a contaminated valley in Southeast China

A survey was conducted on the accumulation and spatial distribution of PAHs in surface soils under different land use patterns in a valley in the Yangtze Delta region with an area of 10 km² containing 15 small copper- and zinc-smelting furnaces. Sixty-five topsoil (0–20 cm) samples were collected and 16 PAHs were determined. The average amount of all the 16 PAHs ranged from 0 to 530 μg kg⁻¹ (oven dry basis), with a mean concentration of 33.2 μg kg⁻¹. Benzo[a]pyrene and indeno[1, 2, 3, -cd]pyrene were the two main PAHs present at high concentrations, while pyrene and fluorene had very low concentrations. PAH concentrations were higher in uncultivated than in cultivated soils, and areas of woods and shrubbery had the␣lowest soil PAH contents. The average PAH-homologue concentrations ranked as follows: 5-rings >> 3-rings, 4-rings > 6-rings >2-rings. Much higher concentrations of PAHs were found in the southern part of the sampling area, perhaps due to deposition of airborne particles by the southeasterly winds in winter and spring. We conclude that the small smelting furnaces were the dominant source of PAHs that accumulated in the soils and the southeasterly winds led to the spatial distribution of PAHs in the topsoils. Land vegetation cover and soil utilization patterns also affected the accumulation and distribution of soil PAHs.     

Polycyclic aromatic hydrocarbons in soils around Guanting Reservoir,Beijing, China

The concentrations of 16 polycyclic aromatic hydrocarbons (∑ 16PAHs) were measured by gas chromatography equipped with a mass spectrometry detector (GC-MS) in 56 topsoil samples around Guanting Reservior (GTR), which is an important water source for Beijing. Low to medium levels of PAH contamination (mean=394.2±580.7 ng g^?1 dry weight (d.w.)) was evident throughout the region. In addition, localised areas of high PAH contamination near steel and cement factories were identified, with ∑ 16PAHs concentrations as high as 4110 ng/g, dry weight (d.w.). There was a significant positive correlation (r²=0.570, p<0.01) between total organic carbon content and ∑ 16PAHs concentrations. Phenanthrene was the predominant compound, accounting for 27.2% of the ∑ PAH concentration, followed by chrysene>pyrene>benzo[a]anthracene≈ benzo[b]fluoranthene≈ benzo[a]pyrene. Four-ring PAH homologues (39%) were dominant. The higher proportion of 4–6 ring homologues, molecular indices, and the spatial distribution of PAH indicated that industrial discharges, incineration of wastes and traffic discharges were the major sources of soil PAHs around the water reservoir.     

Lichens to distinguish urban from industrial PAHs

This paper shows that lichens can be used as biomonitors to distinguish urban from industrial polycyclic aromatic hydrocarbons (PAHs). PAHs are atmospheric pollutants originating mainly from incomplete combustion of fuels in vehicles and industry. The occurrence of PAHs in air is a serious health issue in urban areas and industrial areas because some PAHs are carcinogenic. Biomonitoring PAHs with lichens is generally applied for quantification of PAHs. However, the precise sources of PAHs are not well known. Here we use lichen to trace the source of PAHs. PAHs were analyzed in Pyxine subcinerea Stirton, a lichen species collected from twelve sites which vary from urban and industrial to periurban forest area of Haridwar, in the foothills of the Indian Himalayas. Total PAH concentration ranged between 1.25 and 187.3 μg g⁻¹. Results indicate a clear distinction between urban and industrial PAHs profile, using principal component analysis. Lichen sampled from industrial sites exhibited higher concentrations of two-, five-, and six-ringed PAHs, up to 60% of total PAHs, while samples from urban sites were dominated by four-ringed PAHs, predominantly fluoranthene and acenaphthylene. Molecular ratios indicate that combustion was the dominant source of origin of PAHs in industrial area, while urban sites showed mixed origin of PAHs, both pyro- and petrogenic.     

Bioavailability of polycyclic aromatic hydrocarbons (PAHs) to short-neck clam (<Emphasis Type="Italic">Paphia undulata</Emphasis>) from sediment matrices in mudflat ecosystem of the west coast of Peninsular Malaysia

The bioaccumulation and bioavailability of polycyclic aromatic hydrocarbons (PAHs) were characterized in sediment and Paphia undulata (short-neck clam) from six mudflat areas in the west coasts of Peninsular Malaysia. The concentrations of total PAHs varied from 357.1 to 6257.1 and 179.9 ± 7.6 to 1657.5 ± 53.9 ng g ^?1 dry weight in sediment and short-neck clam samples, respectively. PAHs can be classified as moderate to very high level of pollution in sediments and moderate to high level of pollution in short-neck clams. The diagnostic ratios of individual PAHs and principal component analysis indicate both petrogenic and pyrogenic sources with significant dominance of pyrogenic source. The first PAHs biota-sediment accumulation factors and relative biota-sediment accumulation factors data for short-neck clam were obtained in this study, indicating a preferential accumulation of lower molecular weight PAHs. Evaluation of PAH levels in sediments and short-neck clams indicates that short-neck clam could be introduced as a good biomonitor in mudflats. The results also demonstrated that under environmental conditions, the sedimentary load of hydrocarbons appears to be one of the factors controlling their bioavailability to biota.     

Sources and spatial distribution of polycyclic aromatic hydrocarbons in coastal sediments of the Basque Country (Bay of Biscay)

This contribution characterises the sources and distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Basque coast (Bay of Biscay). Different source characterisation approaches (i.e. GIS assisted-chemometrics, PAH diagnostic ratios and analyses of composition profiles) were used in combination to successfully identify the factors determining the origin and distribution of PAHs. Urban/industrial combustion processes were identified as the main PAH source. However, the analysis of PAH composition patterns and diagnostic ratios identified secondary natural and petrogenic PAH sources on small spatial scales. The median ∑18PAH concentration ranged from 66 μg kg^?1 (d.w.) to 7021 μg kg^?1 (d.w.). The Ibaizabal estuary, which supports most of the anthropogenic pressure in the region (i.e. urban development, industrialisation, commercial and recreational harbours), also showed the highest PAH concentrations. On the shelf, human activities, hydrodynamic conditions and geomorphological features led to spatial differences in the PAH concentrations among sectors: the offshore and west sectors were characterised by higher concentrations, while the lowest values were found in the mid and east sectors. The results enhance the knowledge on PAH-related contamination processes and could be used to support the environmental assessment process required under current European marine legislation.     

Assessment of PAHs in water and fish tissues from Great Bitter and El Temsah lakes,Suez Canal,as chemical markers of pollution sources

Sea water and fish tissue samples were collected from nine sampling stations from the Great Bitter and El Temsah lakes in the Suez Canal and analysed for polycyclic aromatic hydrocarbon (PAH). The compositions of PAH determined in the dissolved fraction of sea water were measured in order to use them as chemical markers for identifying different sources of PAH pollution in this region. PAHs determined in fish tissues were measured for comparison with human health standards as consumption. The total mean PAHs concentrations in the sea water samples ranged from 0.28 to 39.57 μg l^?1 with an overall mean of 10.78 and 12.38 μg l^?1 for El Temsah and Bitter Lakes water, respectively. Total PAHs fractions recorded in muscle tissues of all different Osteicthyes fishes collected from Great Bitter lakes ranged from 5.8 to 218.5 μg g^?1 with an overall mean of 57.98 μg g^?1 during all seasons. However, they ranged from 68 to 623 μg g^?1 with an overall mean of 87.69 μg g^?1 recorded in El Temsah lake during four seasons (2003–2004). Benzo(a)pyrene was the most dominant PAHs found in the sea water samples from both lakes with an average concentration of 3.8 μ g l^?1. Dibenzo(a,h)anthracene (DBA) was the most dominant PAHs recorded in fish samples. A maximum of 533 μg g^?1 of DBA was recorded in Dahbana sp. collected from Bitter lakes during January 2004. However, a maximum of 68.7 μ g g^?1 was recorded in Liza carinata species collected from El Temsah lake during July, 2004. The simultaneous occurrence of isomer ratios PHE/ANT<10 for all stations indicated that the major PAH input to water was from combustion of fossil fuel (pyrolytic source). The average ratios were 1.21 and 12.9 during winter (January 2004) and 4.3 and 8.63 during spring (April 2004) for all water samples of Great Bitter lakes and El Temsah lake, respectively. In addition, the present data demonstrate that PAHs from fossil fuel sources (MW<178) were the least significant source of PAHs in this region.     

Ecological risks of polycyclic aromatic hydrocarbons found in coastal sediments along the northern shores of the Bohai Sea (China)

The total concentrations of 16 United States Environmental Protection Agency (US EPA)-listed polycyclic aromatic hydrocarbons (PAHs) found in coastal and estuarine sediments along the northern shores of the Bohai and Yellow Seas, China, at any study location varied from 0.236 to 8.34 nM g^?1 dry weight (dw). For a given PAH, concentrations varied by one to two orders of magnitude. Ecological risk assessments based on biota–sediment accumulation factors (BSAFs) indicated that the potential ecological hazard of PAHs in the sediments was limited. The average total sediment PAH concentrations were less than the effects range low, indicating that PAHs currently present in the sediments were not harmful to aquatic organisms. The estimated PAH concentration in the aquatic organisms was 0.223 nM g^?1 and posed a limited threat to human health via biological concentration from sediment to harvest of the sea. Assuming no additional PAH inputs, 99% of the 16 PAH molecules currently present in the sediments would be degraded in 40 years.     

Microbial functional genes reveal selection of microbial community by PAHs in polluted soils

This report shows an increase of PAH-related microbial functional genes with PAH concentration in soils. Adaptation of microbial communities to organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) is a crucial issue. However, there is little knowledge on mechanisms ruling microbial community selection. Here, we studied microbial functional genes in soils contaminated by PAHs. We used GeoChip, an advanced functional gene array for gene analysis. Soil PAH concentrations were measured and microbial functional genes were categorized. PAH-related microbial functional genes, bph, nah, nidA, phd, dfb, and qor, were quantitatively expressed. Total microbial functional genes and PAH-related microbial functional genes were compared with PAH concentration by cluster analysis and curve-fitting analysis. We found that the average abundance of PAH-related microbial functional genes increased from 0.13 to 0.33, whereas that of total microbial functional genes decreased from 0.22 to 0.10 when PAHs concentration increased from 1.01 to 164.28 mg kg^?1. It was also found that the classification of microbial community structure characteristics based on PAH-related microbial functional genes was closely similar to the classification based on PAHs concentration. Findings reveal that PAH stress promotes the dominance of PAH-related microbial communities.     

Distribution,source apportionment and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in intertidal sediment of Asaluyeh,Persian Gulf

Surface sediment samples were collected from intertidal zone of Asaluyeh, Persian Gulf, to investigate distribution, sources and health risk of sixteen polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations ranged from 1.8 to 81.2 μg kg^?1 dry weight, which can be categorized as low level of pollution. Qualitative and quantitative assessments showed that PAHs originated from both petrogenic and pyrogenic sources with slight pyrogenic dominance. Source apportionment using principal component analysis indicated that the main sources of PAHs were fossil fuel combustion (33.59%), traffic-related PAHs (32.77%), biomass and coal combustion (18.54%) and petrogenic PAHs (9.31%). According to the results from the sediment quality guidelines, mean effects range-median quotient (M-ERM-Q) and benzo[a]pyrene toxic equivalents (BaP_eq), low negative ecological risks related to PAH compounds would occur in the intertidal zone of Asaluyeh. The total benzo[a]pyrene (BaP) toxic equivalent quotient (TEQ^carc) for carcinogenic compounds ranged from 0.01 to 7 μg kg^?1-BaP_eq, indicating low carcinogenic risk. The human health risk assessment of PAH compounds via ingestion and dermal pathways suggests low and moderate potential risk to human health, respectively.     

Polycyclic aromatic hydrocarbons in Syrian olive oils and their likely daily intakes

The levels of 16 US Environmental Protection Agency polycyclic aromatic hydrocarbons (16 EPA PAHs) in Syrian olive oils have been determined. Forty-two samples including commercial extra virgin and virgin olive oils, and virgin olive oils from olive mills were analyzed. Only naphthalene (NAP) was detected in all olive oil samples under investigation. Among the studied 16 EPA PAHs, the highest maximum concentration was also observed for NAP (120 μg kg^?1). Moreover, three samples exceeded the European Union (EU) maximum level of 2 μg kg^?1 for benzo[a]pyrene (BaP) in oils and fats, and only one sample exceeded the EU maximum level of 10 μg kg^?1 for the sum of benz[a]anthracene, chrysene, BaP, and benzo[b]fluoranthene (PAH4). The likely daily intakes of the total sum of 16 EPA PAHs, the sum of eight genotoxic PAHs, the sum of PAH4, the BaP, and the BaP equivalent through consumption of Syrian olive oils were estimated.     

Spatial distribution and temporal trends of polycyclic aromatic hydrocarbons (PAHs) in water and sediment from Songhua River, China

The spatial and temporal distributions of polycyclic aromatic hydrocarbons (PAHs) in the Songhua River, Harbin, China, were investigated. Seventy-seven samples, 42 water and 35 sediment samples, were collected in April and October of 2007 and January of 2008. The concentrations of total PAHs in water ranged from 163.54 to 2,746.25 ng/L with the average value of 934.62 ng/L, which were predominated by 2- and 3-ring PAHs. The concentrations of total 16 PAHs in sediment ranged from 68.25 to 654.15 ng/g dw with the average value of 234.15 ng/g dw, which were predominated by 4-, 5- and 6-ring PAHs. Statistical analysis of the PAH concentrations shown that the highest concentrations of the total PAHs were found during rainy season (October of 2007) and the lowest during snowy season (January of 2008). Ratios of specific PAH compounds, including fluoranthene/(fluoranthene + pyrene) (Flu/(Flu + Pyr)) and phenanthrene/(phenanthrene + anthracene) (An/(Ant + PhA)), were calculated to evaluate the possible sources of PAH contaminations. These ratios reflected pyrolytic inputs of PAHs in Songhua River water and a mixed pattern of pyrolytic and petrogenic inputs of PAHs in the Songhua River sediments. Ecotoxicological risk levels calculated for PAHs suggested that there were individual PAHs, which can less frequently cause biological impairment in some samples, but no samples had constituents that may frequently cause biological impairment. Total toxic benzo[a]pyrene equivalent of ΣcPAHs varied from 10.03 to 29.7 ng/g dw and from 0.36 to 1.92 ng/g dw for total toxic tetrachlorodibenzo-p-dioxin equivalent. The level of PAHs indicated a low toxicological risk to this area.     

Polycyclic aromatic hydrocarbon derivatives in airborne particulate matter: sources,analysis and toxicity

Polycyclic aromatic hydrocarbons (PAHs) are worldwide pollutants produced mainly during incomplete combustion and pyrolysis of organic substances. PAH derivatives are components with hydrogen on the aromatic ring substituted by carbonyl-, nitro- and hydroxyl-functional groups (N-PAH, O-PAH or OH-PAH), or a group of heterocyclic PAHs containing one sulfur atom in place of a carbon atom in the aromatic ring. PAHs and their derivatives can be either introduced in the atmosphere directly in this form as primary pollutants, or formed by homogenous and heterogeneous oxidation reactions. During the last decades, interest on studying PAH derivatives has increased because derivatives may be more harmful than parent compounds. PAH derivatives have been detected in the atmospheric particulate matter in numerous cities worldwide. PAH derivatives enter living organisms by inhalation, oral ingestion and dermal contact. In vivo and in vitro experiments together with epidemiological studies have shown the toxic effects of PAH derivatives, notably for compounds present in airborne and diesel exhaust particles. Here we review the sources, the mechanisms of formation, the physicochemical properties, the analytical methods, and the toxicological effects of PAHs and their derivatives in airborne particulate matter.     

Historical record of anthropogenic polycyclic aromatic hydrocarbons in a lake sediment from the southern Tibetan Plateau

High-altitude lake sediments can be used as natural archives to reconstruct the history of pollutants. In this work, the temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was determined in a sediment core collected from the southern Tibetan Plateau (TP), which was dated by using the ²¹⁰Pb dating method and validated with the ¹³⁷Cs fallout peak. The concentrations of the anthropogenic PAHs (Σ₈PAH) in the sediment core ranged from 0.83 to 12 ng/g dw, and the fluxes of the Σ₈PAH were in the range of 2.1–27 g/cm²/year. The temporal variations in the concentration and input flux of anthropogenic PAHs were low with little variability before the 1950s, and then gradually increased from the 1950s to the 1980s, and an accelerated increase was observed after the early 1980s. The content of total organic carbon played an insignificant role in affecting the time trends of PAHs in the sediment core. Diagnostic concentration fractions of PAH components indicate PAHs in the lake sediment of the southern TP which are mainly from biomass burning and/or from long-range atmospheric transport.     

Dependency of polycyclic aromatic hydrocarbon concentrations on particle size distribution in Tehran atmosphere

In this work, the airborne particulate matter with an aerodynamic diameter less than 10 µm (PM₁₀) was fractionated in a six-stage high-volume cascade impactor to identify particulate size distribution in Tehran atmosphere. The study was conducted at 15 sites located in the north, south, east, west, and central parts of Tehran in 2005. Air samples were analyzed for 16 polycyclic aromatic hydrocarbons (PAHs) by HPLC. The daily PM₁₀ concentrations at the peak of traffic in roadside areas were found to be 106–560 µg m^?3. The cumulated concentration sum of PAHs, based on 16 species, was found to have an average concentration of 380 ng m^?3. Furthermore, it was found that more than 60% of PAHs belonged to the small particulate size range, having sizes of less than 0.49 µm, some containing benzo(ghi)perylene and indeno(123cd)pyrene (high molecular weight) with average concentrations of 8 and 6 ng m^?3 and fluorene, phenanthrene, and fluoranthene (low molecular weight) with average concentrations of 14, 13, and 19 ng m^?3, respectively. In addition, the results revealed that the lighter three- and four-ring PAH compounds were the most abundant pollutants in the air collected at all the sampling sites.     

Distribution pattern of polycyclic aromatic hydrocarbons in particle-size fractions of coking plant soils from different depth

The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) in four size fractions (<2, 2–20, 20–200, >200 μm) in soils at different depth from a heavily contaminated crude benzol production facility of a coking plant were determined using GC–MS. Vertically, elevated total PAHs concentrations were observed in the soils at 3.0–4.5 m (layer B) and 6.0–7.5 m (layer C), relatively lower at 1.5–3.0 m (layer A) and 10.5–12.0 m (layer D). At all sampling sites, the silt (2–20 μm) contained the highest PAHs concentration (ranged from 726 to 2,711 mg/kg). Despite the substantial change in PAHs concentrations in soils with different particle sizes and lithologies, PAHs composition was similarly dominated by 2–3 ring species (86.5–98.3 %), including acenaphthene, fluorene, and phenanthrene. For the contribution of PAHs mass in each fraction to the bulk soil, the 20–200 μm size fraction had the greatest accumulation of PAHs in loamy sand layers at 1.0–7.5 m, increasing with depth; while in deeper sand layer at 10.5–12.0 m, the >200 μm size fraction showed highest percentages and contributed 81 % of total PAHs mass. For individual PAH distribution, the 2–3 ring PAHs were highly concentrated in the small size fraction (<2 and 2–20 μm); the 4–6 ring PAHs showed the highest concentrations in the 2–20 μm size fraction, increasing with depth. The distribution of PAHs was primarily determined by the sorption on soil organic matter and the characteristics of PAHs. This research should have significant contribution to PAH migration study and remediation design for PAHs-contaminated sites.     

Occurrence and particle-size distributions of polycyclic aromatic hydrocarbons in the ambient air of coking plant

The purpose of this study was to characterize the occurrence and size distributions of ten species of polycyclic aromatic hydrocarbons (PAHs) in the ambient air of coking plants. Particulate-matter samples of four size fractions, including ≤2.1, 2.1–4.2, 4.2–10.2, and ≥10.2 μm, were collected using a Staplex234 cascade impactor during August 2009 at two coking plants in Shanxi, China. The PAHs were analyzed by a gas chromatograph equipped with a mass-selective detector. The concentrations of total particulate-matter PAHs were 1,412.7 and 2,241.1 ng/m³ for plants I and II, and the distributions showed a peak within the 0.1–2.1 μm size range for plant I and the 0.1–4.2 μm for plant II. The size distributions of individual PAHs (except fluoranthene) exhibited a considerable peak within the 0.1–2.1 μm size range in coking plant I, which can be explained by the gas–particle partition mechanism. The ambient air of the coking plant was heavily polluted by PAHs associated with fine particles (≤2.1 μm), and benzo[b]fluoranthene made the largest contribution to total PAHs. The exposure levels of coking-plant workers to PAHs associated with fine particles were higher than to PAHs associated with coarse particles. Benzo[b]fluoranthene, benzo[a]pyrene, and dibenzo[a,h]anthracene should be the primary pollutants monitored in the coking plant. This research constitutes a significant contribution to assessing the exposure risk of coking-plant workers and providing basic data for PAH standards for ambient air in coking plants.     

Promoting the use of BaP as a marker for PAH exposure in UK soils

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants that frequently accumulate in soils. There is therefore a requirement to determine their levels in contaminated environments for the purposes of determining impacts on human health. PAHs are a suite of individual chemicals, and there is an ongoing debate as to the most appropriate method for assessing the risk to humans from them. Two methods predominate: the surrogate marker approach and the toxic equivalency factor. The former assumes that all chemicals in a mixture have an equivalent toxicity. The toxic equivalency approach estimates the potency of individual chemicals relative to the usually most toxic Benzo(a)pyrene. The surrogate marker approach is believed to overestimate risk and the toxic equivalency factor to underestimate risk. When analysing the risks from soils, the surrogate marker approach is preferred due to its simplicity, but there are concerns because of the potential diversity of the PAH profile across the range of impacted soils. Using two independent data sets containing soils from 274 sites across a diverse range of locations, statistical analysis was undertaken to determine the differences in the composition of carcinogenic PAH between site locations, for example, rural versus industrial. Following principal components analysis, distinct population differences were not seen between site locations in spite of large differences in the total PAH burden between individual sites. Using all data, highly significant correlations were seen between BaP and other carcinogenic PAH with the majority of r ² values > 0.8. Correlations with the European Food Standards Agency (EFSA) summed groups, that is, EFSA2, EFSA4 and EFSA8 had even higher correlations (r ² > 0.95). We therefore conclude that BaP is a suitable surrogate marker to represent mixtures of PAH in soil during risk assessments.     

Vertical distribution and environmental significance of PAHs in soil profiles in Beijing,China

Vertical distribution of both the concentration and composition of polycyclic aromatic hydrocarbons (PAHs) in ten profiles in Beijing has been investigated. The results showed that PAH concentrations and compositions in topsoil from different sampling sites were different. PAH concentrations were much higher in topsoil of the investigated urban area, industrial region, and paddy field with wastewater irrigation than in other areas. Moreover, PAH concentrations in topsoil were much higher than those at greater depth, where the concentrations were relatively consistent in most soil profiles. The fingerprints of PAHs in the samples from topsoil (0–30 cm) in the same profiles were similar and were obviously different from those at greater depth, suggesting that PAH sources were consistent in topsoil samples and were discriminating between topsoil and deeper soils. PAHs in topsoil mainly arose from mixed sources of combustion of liquid fuel, coal, and/or wood, as well as wastewater irrigation, while those at greater depth were derived from soil genesis and the process of soil formation.     

Characterization and sources of PAHs in an urban river system in Beijing,China

Water samples from 20 locations on rivers in the Tongzhou District of Beijing were collected four times from July 2005 to March 2006. In addition, sediment samples were collected in July 2005. All samples were analyzed for 16 US Environmental Protection Agency (EPA) priority pollutants polycyclic aromatic hydrocarbons (PAHs). The concentration, distribution, seasonal variation, and sources of the 16 PAH compounds identified in the water samples, suspended particles, and surface sediments were then evaluated. The concentrations of PAHs in the water and suspended particle and surface sediment samples ranged from 87.3 to 1,890 ng l⁻¹, 1,330 to 27,700 ng g⁻¹, and 156 to 8,650 ng g⁻¹, respectively. These results demonstrated that rivers in the Tongzhou District of Beijing had a high level of PAH pollution, especially in the suspended particles. The highest and lowest concentrations of PAHs in the water samples were observed in summer and spring. However, the seasonal variations in the concentration of PAHs in the suspended particles were more complicated. The dominant compounds in the water, suspended particle, and surface sediment samples were two-, three- and four-ring PAH compounds, respectively. Ratio analysis illustrated that fuel-burning was the primary source of PAHs in the study area. Gasoline, diesel, coal, and coke oven sources were identified and the contributions of the different fuel-burning sources were then calculated using factor analysis and multiple linear regression. These analyses revealed that coal combustion, gasoline combustion plus coke oven emission, and diesel combustion accounted for 38.8%, 38.5%, and 22.7% of the PAHs in suspended particles, respectively.     

Hydrocarbons contamination and microbial degradation in mangrove sediments of the Niger Delta region (Nigeria)

The distribution of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), and their degradability by bacteria in epipelic and benthic sediments from Qua Iboe Estuary mangrove ecosystem and associated creeks were investigated. The research findings revealed that total aliphatic hydrocarbons in sediments ranged from 16.82 mg·kg ^?1 to 210 mg kg ^?1, wheras total PAHs ranged from 6.30 to 35.55 mg·kg ^?1 dry weight of sediment. Low molecular mass (i.e. the 2–3-ring) PAHs were predominant in almost all the sampling points, whereas the higher molecular masses (4-, 5- and 6-ring PAHs) had the lowest concentrations. In general, the sediment samples ES ₂ (39.7%), ES ₃ (24.8%), BS ₁ (46.7%), BS ₂ (49.9%) and BS ₃ (44.2%) showed<50% contributions of Σ combustion–derived PAH (COMP-PAH) concentration to the Σ PAH concentrations, whereas ES ₁ (57%) contained>50% of COMP-PAHs. Our results have also shown that many mangrove bacteria have strong capacity to utilise Qua Iboe Light (QL) crude oil as the sole source of carbon and energy, while lower number of bacterial species including Bacillus sp., Micrococcus sp., Pseudomonas aeruginosa, Alcaligenes sp. and Flavobacterium sp. exhibited detectable PAHs degradability; and as such may serve as efficient degraders of QL crude oil contamination of mangrove ecosystem.