High Molecular Weight Polycyclic Aromatic Hydrocarbons Research Articles

Transformation mechanism of polycyclic aromatic hydrocarbons and hydrogen production during the gasification of coking sludge in supercritical water

In this study, the characteristic of hydrogen production and polycyclic aromatic hydrocarbons (PAHs) transformation during supercritical water gasification (SCWG) of coking sludge (400 °C - 450 °C, 1 min–30 min) were explored. The total gas yield was between 0.62 mol/kg OM and 1.05 mol/kg OM (on dry basis), and the proportion of CH4 and H2 was only between 5.41% and 6.44%. PAH content were increased from 194.92 mg/kg to 326.04 mg/kg, and mainly high molecular weight PAHs, which were formed from the Diels-Adler reaction of single aromatic hydrocarbon and the addition reaction of low molecular weight PAHs. High reaction temperature favored more active PAH formation than reaction time. The possible control methods for PAH formation during SCWG of coking sludge was proposed. H2O2 and KOH addition effectively reduce PAHs amount in solid residues by 46.67% and 38.33%, and KOH performed positive effect on hydrogen production. The work revealed that the inhibition of PAHs and hydrogen production were achieved from SCWG of coking sludge with KOH addition.

Occurrence of polycyclic aromatic compounds and interdomain microbial communities in oilfield soils

Soil polycyclic aromatic compound (PAC) pollution as a result of petroleum exploitation has caused serious environmental problems. The unclear assembly and functional patterns of microorganisms in oilfield soils limits the understanding of microbial mechanisms for PAC elimination and health risk reduction. This study investigated the polycyclic aromatic hydrocarbons (PAHs) and substituted PAHs (SPAHs) occurrence, and their impact on the bacteria-archaea-fungi community diversity, co-occurrence network and functionality in the soil of an abandoned oilfield. The results showed that the PAC content in the oilfield ranged from 3429.03 μg kg−1 to 6070.89 μg kg−1, and risk assessment results suggested a potential cancer risk to children and adults. High molecular weight PAHs (98.9%) and SPAHs (1.0%) contributed to 99.9% of the toxic equivalent concentration. For microbial analysis, the abundantly detected degraders and unigenes indicated the microbial potential to mitigate pollutants and reduce health risks. Microbial abundance and diversity were found to be negatively correlated with health risk. The co-occurrence network analysis revealed nonrandom assembly patterns of the interdomain microbial communities, and species in the network exhibited strong positive connections (59%). The network demonstrated strong ecological linkages and was divided into five smaller coherent modules, in which the functional microbes were mainly involved in organic substance and mineral component degradation, biological electron transfer and nutrient cycle processes. The keystone species for maintaining microbial ecological functions included Marinobacter of bacteria and Neocosmospora of fungi. Additionally, benzo [g,h,i]pyrene, dibenz [a,h]anthracene, indeno [1,2,3-cd]perylene and total phosphorus were the key environmental factors driving the assembly and functional patterns of microbial communities under pollution stress. This work improves the knowledge of the functional pattern and environmental adaptation mechanisms of interdomain microbes, and provides valuable guidance for the further bioremediation of PAC-contaminated soils in oilfields.

Polycyclic aromatic hydrocarbons in selected rivers in southwestern Nigeria: Seasonal distribution, source apportionment and potential risk assessment

The river sediment has been identified as major potential threats to ecosystem and human health due to its repository ability towards pollutants including polycyclic aromatic hydrocarbons (PAHs). A total of 72 surface sediment samples from six major rivers within south-western Nigeria were collected during both wet and dry seasons. Sixteen USEPA priority PAHs were analyzed using GC–MS for profile composition, potential sources, and ecological and human health risks on seasonal basis. PAHs were detected in all analyzed sediments at varying concentrations: ∑16 PAHs ranging from 1226 to 13,093 μg/kg (mean: 1356–12,850 μg/kg) and 1495 to 13,845 μg/kg (mean: 1536–13,671 μg/kg) across all locations during the dry and wet seasons respectively. However, the spread of PAH differs from each location. The carcinogenic PAHs (∑PAH7C) dominated the high molecular weight (HMW) PAH profile (≥ 97%) and accounting for 28 to 45% of the Σ16PAHs, presenting a high carcinogenic potential. Elevated Σ PAHs and ΣPAH7C were observed during the wet season. The study observed varied benzo(a) pyrene (BaP eq) equivalent concentrations across the rivers, suggesting variability in carcinogenic potency. Six-ring PAHs constituted the least composition in all the rivers (< 0.08–0.53 μg/kg) while three and four-ringed PAHs dominated the composition profile. Carbonaceous materials such as black carbon and particulate organic carbon notably influenced PAHs distribution (R2≥0.733, p < 0.05 ). Results of diagnostic ratios suggested the predominance contributions of coal and biomass combustion to PAHs distributions over petrogenic sources by positive matrix factorization (PMF). Further studies on the levels of PAHs in edible seafood transportation processes of PAHs is recommended for developing appropriate risk analysis approaches.

Dynamics and Mass Balance of Polycyclic Aromatic Hydrocarbons in and Around the Seto Inland Sea, Japan

Polycyclic aromatic hydrocarbons (PAHs) were analyzed to elucidate the distribution, ecological risk, pathways, and fluxes of these pollutants in and around the Seto Inland Sea, an industrialized coastal region of Japan. High molecular weight PAHs (5-6 rings) were primarily found in regions close to the bay estuaries, and their proportions decreased at distances further from the estuaries (offshore areas), where low molecular weight PAHs (2-4 rings) were more ubiquitous. Screening-level risk assessments revealed that the PAHs found in the sediments should have no adverse effects on benthic communities. A mass balance for PAHs in the Seto Inland Sea, calculated based on data collected in the field and published literature findings, showed the PAH flux into the Seto Inland Sea from atmospheric deposition were ca. 6 times higher than that from riverine inflows. Comparison of the amount of the PAH mass flux between the Seto Inland Sea and the sea of the Europe and Asian countries indicated that the Seto Inland Sea is less polluted than the Gulf of Lion, the Mediterranean Sea, and the Bohai Sea, China and more polluted than the Yellow Sea. This paper is the first to determine the fluxes of PAHs in the coastal region of Japan.

Accumulation of high-molecular-weight polycyclic aromatic hydrocarbon impacted the performance and microbial ecology of bioretention systems

Bioretention has been considered as an effective management practice for urban stormwater in the removal of pollutants including polycyclic aromatic hydrocarbons (PAHs). However, the accumulation of high-molecular-weight (HMW) PAHs in bioretention systems and their potential impact on the pollutants removal performance and microbial ecology are still not fully understood. In this study, comparisons of treatment effectiveness, enzyme activity and microbial community in bioretention systems with different types of media amendments were carried out at different spiking levels of pyrene (PYR). The results showed that the removal efficiencies of chemical oxygen demand (COD) and total nitrogen in the bioretention systems were negatively impacted by the PYR levels. The relative activities of soil dehydrogenase and urease were increasingly inhibited by the elevated PYR level, indicating the declining microbial activity regarding organic matter decomposition. The spiking of PYR negatively affected microbial diversity, and distinct time- and influent-dependent changes in microbial communities were observed. The relative abundance of PAH-degrading microorganisms increased in PYR-spiked systems, while the abundance of nitrifiers decreased. The addition of media amendments was beneficial for the enrichment of microorganisms that are more resistant to PYR-related stress, therefore elevating the COD concentration removal rate by ∼50%. This study gives new insight into the multifaceted impacts of HMW PAH accumulation on microbial fingerprinting and enzyme activities, which may provide guidance on better stormwater management practices via bioretention in terms of improved system longevity and performance.

Seasonal distribution of PM2.5-bound polycyclic aromatic hydrocarbons as a critical indicator of air quality and health impact in a coastal-urban region of Poland

This study focuses on the inter-seasonal distribution and variability of thirteen native PAHs adsorbed onto respirable PM2.5 fraction collected in a coastal-urban region of northern Poland, in 2019. The backward trajectory analysis and several diagnostic ratios were applied to determine seasonal profiles of PAH congeners and their major sources in airborne samples. The annual cumulative mean value of total PAHs in PM2.5 was 6.92 ± 10.1 ng m−3, varying in the following range: 0.32 ng m−3 (May) – 68.57 ng m−3 (January). Seasonal mass concentrations of total particulate PAHs were ranked as follows: summer (1.27 ng m−3) < spring (4.83 ng m−3) < autumn (6.16 ng m−3) < winter (18.5 ng m−3). Clear seasonal differences in PAH concentrations can be explained by direct impact of local and regional urban/industrial activities, with priority winter contribution of coal combustion in residential and commercial sectors. In addition, for summer measurements the diagnostic ratios indicated that high molecular weight PAHs were mainly derived from vehicle emission and petrochemical industry, while relatively low mass contribution of 4-ring congeners to the total sum of PAHs was attributed to photochemical processing. The analysis of meteorological parameters (temperature, relative humidity) and gaseous precursors (SO2, NO2, NOx, O3 and CO) exhibits their statistically significant correlations with PAHs, indicating local/regional primary emission. The incremental lifetime cancer risk was 1.23 × 10−5, suggesting potential toxicity and carcinogenicity for adult females and males. This study highlights the importance of the implementation of health risk assessment model in urbanized coastal zones.

Current and Future Trends of Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons in Surface Water and Sediments of China: Insights from Their Long-Term Relationships between Concentrations and Emissions.

In this study, we analyzed the temporal trend of polycyclic aromatic hydrocarbons (PAHs) in China using data reported over the past 20 years. We found that the total concentrations of low molecular weight PAHs (CΣLPAHs) in surface water and sediments were positively correlated with their total emissions (EΣLPAHs), which increased between 2000 and 2008, then decreased until 2017. Additionally, the total concentrations of high molecular weight PAHs (C∑HPAHs) in surface water and sediments were positively correlated with their total emissions (EΣHPAHs), which increased significantly from 2000 to 2014 and then plateaued. Two future scenarios were assessed to explore C∑LPAHs and C∑HPAHs in surface water and sediments. PAH emissions were reduced by technological improvement in 2030 for coal consumption in Scenario 1 and for control of biomass burning in Scenario 2. Scenario 1 was more efficient than Scenario 2 in reducing C∑HPAHs in the surface water and sediments of China for the areas where CΣHPAHs in surface water exceeded the annual average standard (i.e., 30 ng L-1), with reductions of 38 and 24% in Scenarios 1 and 2, respectively. The observed relationships in this study can provide tools for emission reduction policies in the future.

Bioremediation of HMW-PAHs-contaminated soils by rhizosphere microbial community of Fire Phoenix plants

• Fire Phoenix plants were able to grow in soils containing low or high Σ4PAHs. • Fungi from four genera were highly enriched in Fire Phoenix rhizosphere. • Aspergillus , Mortierella , Geomyces and Humicola might be main PAHs degraders. • PAHs were removed by 75.2% or 78.8% from the low or high Σ4PAH soil. • Degradation was likely via cytochrome P450 monooxygenase and ligninases. Soil contamination by high-molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) is a challenging problem worldwide. Bioremediation is a safe and cost-effective way of abating HMW-PAHs. The present study was designed to investigate the potential of microbes in the rhizosphere of Fire Phoenix plants in biodegradation of HMW-PAHs in a pot-culture experiment. Plant growth, removal rates of PAHs, phospholipid fatty acids, and fungal community composition were determined in soils devoid of PAHs or containing a low or a high level of PAHs after 0, 60, 120, and 150 days of experiment initiation. Results showed that plants were able to continuously grow in the contaminated soils during a 150-day experiment. The biodegradation rates in low and high ∑4PAH (four compounds: pyrene, chrysene, benzo(b)fluoranthene, and benzo(k)fluoranthene) soils with plants were 75.2% and 78.8%, which were 21.8% and 28.0% higher than the control soils without plants, respectively. The soil microbial analysis showed that the growth of Fire Phoenix led to the shift of soil microbial community structure by promoting the growth of fungi in four dominant genera: Aspergillus , Mortierella , Geomyces , and Humicola , which could play an important role in PAHs degradation. Based on the results from this study and other relevant reports, schematic metabolic pathways for microbe-mediated degradation of PAHs in the Fire Phoenix rhizosphere soils were proposed, which include cytochrome P450 monooxygenase pathway, ligninolytic pathway, and dioxygenase pathway. Our study showed that the beneficial interactions between Fire Phoenix and soil microbes, fungi in particular, represent a viable way of reducing HMW-PAHs from contaminated soils.

Oxidative status of planarians is differently affected by PAHs: 3-5 Benzene ring compounds

Planarians are promising model animals and are increasing in importance for ecotoxicological studies. However, there is scarce to no information regarding polycyclic aromatic hydrocarbons (PAHs) specific toxicity towards planarians at the biochemical level. We aimed to uncover how vital physiological functions, such as, neurophysiology, detoxification and oxidative stress status, and cellular energy allocation are affected on the freshwater planarian Girardia tigrina by low and high molecular weight PAHs – phenanthrene, pyrene and benzo[a]pyrene (B[a]P). Phenanthrene affected planarian antioxidant defences and detoxification, increasing glutathione levels and activity of glutathione-S-transferase (GST), the latter in a dose-dependent way (from 75 to 300 µg L−1). Phenanthrene also decreased carbohydrates in planarians exposed to 150 and 300 µg L−1. Pyrene caused higher oxygen consumption and decreased energy budget in planarians exposed to 75 and 150 µg L−1. B[a]P exposure decreased G. tigrina GST activity in a dose-dependent way. Lower lipid peroxidation levels were measured in planarians exposed to 2.5 and 75 µg L−1 of pyrene and at 37.5, 75 and 150 µg L−1 of B[a]P. The present data indicate that each of these PAHs seems to elicit distinct biochemical responses in planarians, possibly pointing to different biochemical interactions and/or metabolisation of each compound, with B[a]P causing the most severe effects.

Sediment Remediation Using Activated Carbon: Effects of Sorbent Particle Size and Resuspension on Sequestration of Metals and Organic Contaminants.

Thin‐layer capping using activated carbon has been described as a cost‐effective in situ sediment remediation method for organic contaminants. We compared the capping efficiency of powdered activated carbon (PAC) against granular activated carbon (GAC) using contaminated sediment from Oskarshamn harbor, Sweden. The effects of resuspension on contaminant retention and cap integrity were also studied. Intact sediment cores were collected from the outer harbor and brought to the laboratory. Three thin‐layer caps, consisting of PAC or GAC mixed with clay or clay only, were added to the sediment surface. Resuspension was created using a motor‐driven paddle to simulate propeller wash from ship traffic. Passive samplers were placed in the sediment and in the water column to measure the sediment‐to‐water release of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and metals. Our results show that a thin‐layer cap with PAC reduced sediment‐to‐water fluxes of PCBs by 57% under static conditions and 91% under resuspension. Thin‐layer capping with GAC was less effective than PAC but reduced fluxes of high–molecular weight PAHs. Thin‐layer capping with activated carbon was less effective at retaining metals, except for Cd, the release of which was significantly reduced by PAC. Resuspension generally decreased water concentrations of dissolved cationic metals, perhaps because of sorption to suspended sediment particles. Sediment resuspension in treatments without capping increased fluxes of PCBs with log octanol–water partitioning coefficient (K OW) > 7 and PAHs with log K OW of 5–6, but resuspension reduced PCB and PAH fluxes through the PAC thin‐layer cap. Overall, PAC performed better than GAC, but adverse effects on the benthic community and transport of PAC to nontarget areas are drawbacks that favor the use of GAC. Environ Toxicol Chem 2022;41:1096–1110. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

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

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

North-south geographic heterogeneity and control strategies for polycyclic aromatic hydrocarbons (PAHs) in Chinese lake sediments illustrated by forward and backward source apportionments

As universal and supervirulent pollutants, understanding the potential sources of polycyclic aromatic hydrocarbons (PAHs) in lakes is critical for formulating pollutant control policies that will ensure the ecological safety of aquatic environments. Geographic heterogeneity of PAHs in lake sediments from China nationwide was investigated to indicate north-south dissimilarities in PAH levels and sources and propose specific PAH control strategies. Geographic PAH patterns showed that higher concentrations were found in the south compared to the north due to higher energy consumption and more intense industrial activities. Furthermore, the primary contributors in the south were high molecular weight (HMW) PAHs, whereas low molecular weight (LMW) PAHs were dominant in the north. The results of forward source apportionment based on the PAH emission method (EM) were consistent with the backward method using the positive matrix factorization (PMF) model, which verified the feasibility of the combined methods. Petroleum from transport was the dominant PAH source in the south, and purifying gasoline and diesel, promoting new energy vehicles and direct injection engines might effectively reduce PAH emission. Domestic coal was the main PAH source in the north, thereby adding active substance in coal and using cleaner energy could reduce PAH release.

Drinking water treatment residue recycled to synchronously control the pollution of polycyclic aromatic hydrocarbons and phosphorus in sediment from aquatic ecosystems

Great efforts have long been made to control sediment pollution from persistent organic pollutants and phosphorus for aquatic ecosystem restoration. This study proposed a novel recycling of drinking water treatment residue (DWTR) to synchronously control sediment polycyclic aromatic hydrocarbons (PAHs) and phosphorus pollution based on a 350-day incubation test. The results suggested that DWTR addition reduced approximately 88%− 96% of potential bioavailable PAHs and 76% of mobile phosphorus in sediment. The dominant mechanisms for both reductions by DWTR were immobilization, mainly through increasing sediment amorphous aluminum and iron. The tendency of enhanced PAHs degradation by DWTR was also observed, especially for high molecular weight PAHs (e.g., chrysene, indeno(1, 2, 3-cd)pyrene, and benzo(g, hi)perylene), which decreased by approximately 21.1%− 22.0% of the total. Additionally, accompanying a clear increase in the connections of microbial cooccurrence networks, the variations in bioavailable PAHs, amorphous aluminum and iron, and other properties (e.g., pH, nitrogen, and organic matter) significantly (p < 0.01) enhanced Flavobacterium enrichment, although the enrichment of many other microbes potentially related to PAHs degradation (e.g., C1-B045) decreased after DWTR addition. Therefore, DWTR could promote the construction of a “PAHs immobilization with microbial augmentation” system while immobilizing phosphorus in sediment, indicating the high feasibility of controlling multiple sediment pollution.

Distribution and Source Apportionment of Polycyclic Aromatic Hydrocarbons in Soils at Different Distances and Depths around Three Power Plants in Bijie, Guizhou Province

In this study, 16 polycyclic aromatic hydrocarbons (PAHs) optimally controlled by the U.S. Environmental Protection Agency (EPA) were investigated. Three representative coal-fired power plants were selected as the research areas in Bijie, Guizhou Province, and 24 soil samples were collected totally from power plants at different depths and at different distances from the point pollution sources (plants). The physicochemical properties and microbial characteristics of the soil from the three power plants were also studied. The results showed that 16 PAHs were detected in all soils of the three power plants, with total concentrations ranging from 0.2 to 12.2 mg kg−1, and that PAHs in the soils were mainly 2, 3 rings with percentages ranging from 42% to 82%. The proportions of low molecular weight (LMW) PAHs were higher near the contaminated plants. Moreover, since they were easily dispersed further away with atmospheric transfer, the proportions of lighter LMW PAHs were also higher far from the point source, while the proportions of heavier high molecular weight (HMW) PAHs were higher at some distance from the point source. In addition, the distribution patterns of PAHs in the soil at different depths were slightly different because the microbial activity in the surface soil at each sampling site was greater than that in the deeper soil, and the leaching behavior of each compound was different. Finally, based on the principal component analysis (PCA) method, coal combustion is not the only source of PAHs in soils from power plants, and vehicle emissions cannot be negligible.

Structural Selectivity of PAH Removal Processes in Soil, and the Effect of Metal Co-Contaminants

Polycyclic aromatic hydrocarbons (PAHs) form a convenient structural series of molecules with which to examine the selectivity exerted on their removal by soil microbiota. It is known that there is an inverse relationship between PAH molecular size and degradation rates in soil. In this paper, we look at how the magnitude of the slope for this relationship, m, can be used as an indicator of the effect of metal co-contaminants on degradation rates across a range of PAH molecular weights. The analysis utilises data collected from our previous microcosm study (Deary, M.E.; Ekumankama, C.C.; Cummings, S.P. Development of a novel kinetic model for the analysis of PAH biodegradation in the presence of lead and cadmium co-contaminants. Journal of Hazard Materials 2016, 307, 240–252) in which we followed the degradation of the 16 US EPA PAHs over 40 weeks in soil microcosms taken from a high organic matter content woodland soil. The soil was amended with a PAH mixture (total concentration of 2166 mg kg−1) and with a range of metal co-contaminant concentrations (lead, up to 782 mg kg−1; cadmium up to 620 mg kg−1; and mercury up to 1150 mg kg−1). It was found that the magnitude of m increases in relation to the applied concentration of metal co-contaminant, indicating a more adverse effect on microbial communities that participate in the removal of higher molecular weight PAHs. We conclude that m is a useful parameter by which we might measure the differential effects of environmental contaminants on the PAH removal. Such information will be useful in planning and implementing remediation strategies.

Degradation profile and dioxygenase activity of Carnobacterium gallinarum (mt350233) and Enterococcus faecalis (mt345788) isolated from landfill soil in Benin City

Landfill is a potential microbial hub of hydrocarbon (HC) degrading bacterial population owing to nutrient availability and continuous enrichment by organic materials. The degradation and dioxygenase activity of Carnobacterium gallinarum and Enterococcus faecalis isolated from landfill soil in Benin City was investigated. Soil samples were collected from a Government approved landfill in Benin City at a depth of 0 to 10 cm. Standard microbiological and molecular methods were followed for the isolation and characterization of bacterial population. Bacterial isolates were standardized for degradation using spectrophotometer optical density (OD) 0.08 at 600 nm (equivalent to 1×108cfu/ml). The gas chromatography with flame ionization detector (GC-FID) method was used to determine the total petroleum hydrocarbon (TPH) of waste engine oil (WEO) containing samples. The spectrophotometric methods were used for the assay of catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) activity. The result of the 16S rRNA analyses of the bacterial isolates confirmed the identity of Carnobacterium gallinarum as 98.71 % and Enterococcus faecalis as 100 %. The degradation profile of Carnobacterium gallinarum and Enterococcus faecalis at varied concentrations (20, 40, 60, 80 and 100 mg/L) of WEO showed significant decline in optical density (OD) values from day 1 to day 7. The decline in OD is an indication of utilization of Polycyclic Aromatic Hydrocarbons (PAHs) present in the WEO. The result of the gas Chromatography with Flame Ionization Detector (GC-FID analyses) of degraded WEO containing samples revealed the absence of low molecular weight and high molecular weight PAHs after the 7-days degradation study. The presence of HC degrading enzyme in the bacterial isolates was confirmed by the production of C12O and C23O as a result of the formation of cis, cis muconic acid and 2-hydroxymuconic semi-aldehyde respectively. This study revealed that the landfill soil is a potential natural microcosm for WEO degrading bacteria and possesses biologically active HC degrading bacteria population such as Carnobacterium gallinarum and Enterococcus faecalis.

Non-equilibrium influence on G/P partitioning of PAHs: Evidence from the diurnal and nocturnal variation

Gas/particle (G/P) partitioning is an important behavior for the atmospheric transport of polycyclic aromatic hydrocarbons (PAHs). In this study, paired daytime and nighttime air samples were collected for one year in order to study the diurnal and nocturnal variations of concentration and G/P partitioning of PAHs. Higher PAHs concentrations in total phase were observed in nighttime. The geomean (GM) concentrations of Σ15PAHs in total phase were 69.6 and 52.8 ng/m3 in nighttime and daytime, respectively. More obviously diurnal and nocturnal variations were observed in non-heating season, with the GM ratios of Σ15PAHs in nighttime to daytime of 1.65 and 1.06 in non-heating season and heating season, respectively. The results could be attributed to emission sources and meteorological conditions. The values of particulate phase fraction (ϕP) and G/P partitioning quotient (log KP) were used to quantify the phase distribution of PAHs. For most high molecular weight PAHs, the values of ϕP and log KP in nighttime were higher than those in daytime, which could be mainly attributed to the lower temperature in nighttime. However, for the three light molecular weight PAHs (Acy, Ace and Flu), higher values of ϕP and log KP were observed in daytime. The regression of log KP against log KOA for the three PAHs in daytime differed from those in nighttime. The chemical losses of PAHs in different phases might be responsible for the result. These findings suggested that the chemical loss of PAHs in gas phase should be considered for the G/P partitioning process.

Spatial distributions and risk assessment of heavy metals and PAH in the southwestern Nigeria coastal water and estuaries, Gulf of Guinea

Spatial distributions and risk assessment of heavy metals (HM) and polycyclic aromatic hydrocarbon (PAH) in water and sediments of two southwestern Nigeria estuaries (Awoye A1-A6 and Abereke: AB1-AB7 and the adjoining coastal waters: I1–I12, C1–C7) were investigated. The physicochemical characteristics were measured in situ, while the HM and PAH were determined using atomic absorption spectrophotometer and gas chromatography coupled with flame ionization detection. The physicochemical characteristics of the water body were within the World Health Organization and United State Environmental Protection Agency stipulated limits for coastal water, except for pH (<6) and dissolved oxygen (<5 mg/l) attributed to a high level of human activities at the impacted stations (I1–I12). The HM in the water samples were within the permissible limits for coastal water bodies except for high Pb values (>1 mg/l) at the Awoye estuary linked to point source effluents of petroleum spills from downstream petroleum transportation. The calculated sediment contamination factor (CF) for HM indicated a considerable (3 < CF < 6) contamination of Cu (CF–Cu) at the sampling stations. Whereas the CF-Cr were within the moderate contamination range (1< CF < 3). The pollution load index (PLI) and ecological risk index (RI) suggest low-risk pollution of heavy metals to the aquatic ecosystems. The assessment of PAH revealed a dominant high molecular weight PAH composition in both surface water and sediments, mainly dominated by 4–6 rings PAH. The PAH diagnostic ratio BaA/(Ba + Chry) and IP/(IP + BghiP) points to the mixed (pyrogenic and petrogenic) origin of PAH across the two tropical estuaries and the coastal waters.

Comparison of indoor and outdoor polycyclic aromatic hydrocarbons from multiple urban residences in Northern China: Coastal versus inland area

Passive air and dust samples were simultaneously collected from urban residences in three functional areas at a coastal site (Weihai) and an inland site (Heze) in Northern China. Samples were concurrently collected in bedrooms, kitchens, and an adjacent outdoor area for each home during the non-heating and heating seasons. Nineteen polycyclic aromatic hydrocarbons (PAHs) were studied by gas chromatography-mass spectrometry (GC-MS). The higher concentrations of PAHs occurred in inland than coastal and industrial area than other districts. The PAHs were more concentrated in outdoor air samples in both cities, but the opposite trend was observed in the dust samples. Compared with bedrooms, higher concentrations of gas-phase PAHs occurred in kitchen. PHE (36.4%) and FLU (18.0%) were the dominant PAHs measured in air samples, whereas middle molecular weight PAHs (34.0%) and high molecular weight PAHs (44.3%) were greater in dust bound PAHs. The I/O ratios of 2–3 rings PAHs in the air were greater than 4–7 rings in both cites indicating that indoor sources had a greater impact on low molecular weight PAHs. The positive matrix factorization (PMF) model identified vehicle exhaust and biomass/coal combustion as the main PAH sources in both outdoor air and dust samples while cooking and solvent use contributed more to indoor samples. Dermal contact with dust accounted for 79.1–85.1% of the total incremental lifetime cancer risk (ILCR) in the study area. Children's ingestion risk was 1.34 and 1.37 times that of adults for both indoor and outdoor sampling areas, respectively.

One-century sedimentary record, sources, and ecological risk of polycyclic aromatic hydrocarbons in Dianchi Lake, China.

In this study, the sedimentary records, sources, and ecological risks of polycyclic aromatic hydrocarbons (PAHs) in Dianchi Lake were analyzed. The concentrations of ΣPAH16 in the sediments of Dianchi Lake ranged from 368 to 990ng/g, with an average value of 572ng/g, peaking in 1988. Economic development, rapid population growth, and rapid growth of coal consumption have a greater impact on the HMW (high molecular weight) PAHs than on the LMW (low molecular weight) PAHs in the sedimentary environment. The results of the diagnostic ratios and PCA (principal component analysis) model show that the main sources of PAHs were coal and biomass combustion, as well as the fossil fuel combustion in individual years. The risk assessment results showed that the PAH concentrations in the sediment were within a safe range. In the past 100years of sediment pore water, other 2-3 ring LMW PAHs were within a safe range (except for Phe, which reached chronic toxic pollution levels in some years). With an increase in industrialization and urbanization, the burning of fossil fuels such as coal and petroleum has increased, and some of the 4-6 ring HMW PAHs have reached chronic toxicity or even acute toxicity in the sediment pore water.