High Molecular Weight Polycyclic Aromatic Hydrocarbons Research Articles

Parent and alkylated PAHs profiles in 11 petroleum fuels and lubricants: Application for oil spill accidents in the environment

Eleven types of petroleum fuels and lubricants including regular gasoline, premium gasoline, jet fuel, kerosene, light oil, bunker A, bunker A–white, bunker A–low sulfur, bunker C, quench oil and lubricant samples were analyzed for parent and alkylated polycyclic aromatic hydrocarbons (PAHs). Naphthalene was the predominant compound in gasolines, jet fuel and kerosene, constituting > 95% of the parent PAHs, whereas dibenzothiophene and other high molecular weight PAHs were predominant in bunker A and bunker C. PAH compositions in petroleum fuels differ because of differences in their refining temperatures and the boiling points of individual PAHs. Principal component analysis classified into four groups of petroleum fuels. Further, oil samples were clearly separated into five groups based on their ratios of select alkyl homologs (C0/(C0+C1) and C4/(C2+C4) naphthalenes): ‘gasolines’ ‘light oil’ ‘bunker oils’ ‘kerosene’ and ‘quench oil’. A wide variety and detailed profiles of PAHs in petroleum fuels and lubricants in this study can be used for baseline data in oil fingerprinting analyses to identify the potential source of oil spill accidents in the environment.

Source analysis and influencing factors of historical changes in PAHs in the sediment core of Fuxian Lake, China

In this study, the influencing factors and sources of historical changes in polycyclic aromatic hydrocarbons (PAHs) in the sediment core of Fuxian Lake were analyzed. Before 1970, the Σ16PAH concentration fluctuated widely, with one or more maximum values. During 1971–2004, the Σ16PAH concentration showed a slow growth trend, while during 2005–2017, the concentration increased sharply, reaching a peak value of 821 ng g−1. dw in 2017. The results of a positive matrix factorization (PMF) model demonstrated that before 1970, PAHs were mainly derived from biomass burning in the Fuxian Lake sediment core, with an overall contribution of 40 %. During 1971–2004, the source of PAHs was mainly coal combustion, with an overall contribution of 34 %. During 2005–2017, PAHs primarily originated from traffic, with an overall contribution of 33 %. Population, coal, GDP, motor, and petroleum had a significant influence on low molecular weight (LMW) PAHs in 1980–2004 and 2005–2017. Motor, coal, population, and GDP had a greater impact on high molecular weight (HMW) PAHs. Before 1970 and in 1971–2004, meteorological factors had little effect on PAHs in the sediment core in Fuxian Lake. During 2005–2017, day and rainfall were significantly negatively correlated with HMW PAHs, while temperature and wind were not correlated with PAH concentrations. During 2005–2017, total organic carbon (TOC) and total nitrogen (TN) had greater adsorption effects on HMW PAHs than on LMW PAHs. Before 1970 and in 1971–2004, the adsorption effects of TOC and TN on 3–4-ring PAHs were greater than those of 2-ring and 5–6-ring PAHs. Total phosphorus (TP) had no adsorption effect on PAHs in the entire sedimentary column.

Identification of pyrene degraders via DNA-SIP in oilfield soil during natural attenuation, bioaugmentation and biostimulation

Pyrene is a model contaminant of high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs), which are compounds that have potential carcinogenic effects and pose a serious threat to human health. Finding effective pyrene-degrading bacteria is crucial for removing PAHs from soil. In this study, DNA-based stable isotope probing (DNA-SIP) technology was used to investigate pyrene degraders in PAH-contaminated oilfield soil during natural attenuation (NA), bioaugmentation (BA) and biostimulation (BS). The results show that BA played an important role in pyrene degradation with the highest pyrene removal rate (~95%) after 12 days incubation, followed by removal rates of ~90% for NA and ~30% for BS. In addition, 6 novel pyrene degraders were identified, while 12 well-known PAH degraders were demonstrated to participate in the biodegradation of pyrene. Additionally, the external homologous strains introduced during BA promoted the degradation of pyrene, but not by directly participating in the metabolism of the target compound. Rhamnolipid supplementation during BS promoted the involvement of more microorganisms in the degradation of pyrene, which was beneficial to identifying more pyrene degraders via DNA-SIP. These findings provide new insight into the effects of external homologous strains and supplementary rhamnolipids on pyrene degradation.

Source Apportionment of Soil PAHs in Lanzhou Based on GIS and APCS-MLR Model

To evaluate the pollution by polycyclic aromatic hydrocarbons (PAHs) in the surface soil of the core urban area of Lanzhou, 62 topsoil samples were collected from the area. The soil samples were analyzed for the content of 16 priority PAHs, using gas chromatography-mass spectrometry. Descriptive statistical methods were used to characterize contamination by PAHs. An absolute principal component analysis-multiple linear regression (APCS-MLR) model was applied to determine the sources of PAHs in the soil samples, and the accuracy of the model results was verified. Finally, the main influence regions of each source were determined with a geo-statistical method. The results showed that the contents of Σ16 PAHs in the surface soils of Lanzhou ranged from 1069 to 7377 μg ·kg-1, with an average of 2423 μg ·kg-1. High molecular weight PAHs (4-6 rings) were dominant, accounting for 72.81% of the Σ16 PAHs. Verification results of the APCS-MLR model showed that the measured values were in good correspondence with the predicted values, which indicated that the model had good applicability for source apportionment of soil PAHs in the study area. The main sources of PAHs in Lanzhou were traffic emissions (35.42%), petroleum emissions (29.88%), and a mixture of coal and biomass combustion (33.91%). The sources were greatly affected by human activities, and high values were mainly distributed in traffic-intensive and industrial areas. The results indicated that the sources of soil PAHs were complex and influenced by anthropogenic activities in the study area. Stringent control measures should be placed on the sources and areas of influence that contribute to soil PAHs to reduce the emissions and the level of soil pollution resulting from PAHs.

Size−resolved source apportionment of particulate matter from a megacity in northern China based on one-year measurement of inorganic and organic components

This research apportioned size-resolved particulate matter (PM) contributions in a megacity in northern China based on a full year of measurements of both inorganic and organic markers. Ions, elements, carbon fractions, n-alkanes, polycyclic aromatic hydrocarbons (PAHs), hopanes and steranes in 9 p.m. size fractions were analyzed. High molecular weight PAHs concentrated in fine PM, while most other organic compounds showed two peaks. Both two-way and three-way receptor models were used for source apportionment of PM in different size ranges. The three-way receptor model gave a clearer separation of factors than the two-way model, because it uses a combination of chemical composition and size distributions, so that factors with similar composition but distinct size distributions (like more mature and less mature coal combustion) can be resolved. The three-way model resolved six primary and three secondary factors. Gasoline vehicles and coal and biomass combustion, nitrate and high relative humidity related secondary aerosol, and resuspended dust and diesel vehicles (exhaust and non-exhaust) are the top two contributors to pseudo-ultrafine (<0.43 μm), fine (0.43–2.1 μm) and coarse mode (>2.1 μm) PM, respectively. Mass concentration of PM from coal and biomass combustion, industrial emissions, and diesel vehicle sources showed a bimodal size distribution, but gasoline vehicles and resuspended dust exhibited a peak in the fine and coarse mode, separately. Mass concentration of sulphate, nitrate and secondary organic aerosol exhibited a bimodal distribution and were correlated with temperature, indicating strong photochemical processing and repartitioning. High relative humidity related secondary aerosol was strongly associated with size shifts of PM, NO3− and SO42− from the usual 0.43–0.65 μm to 1.1–2.1 μm. Our results demonstrated the dominance of primary combustion sources in the <0.43 μm particle mass, in contrast to that of secondary aerosol in fine particle mass, and dust in coarse particle mass in the Northern China megacity.

Influence of the products of biomass combustion processes on air quality and cancer risk assessment in rural environmental (Spain).

Polycyclic aromatic hydrocarbons (PAHs) associated with atmospheric particles represent a significant risk to human health. This issue is even more relevant in environments where biomass combustion processes are considered as the major potential emission sources, such as the rural ecosystem. This study aimed to assess the levels of PM10-bound PAHs in several rural locations, their distribution along a year and how weather variables could influence them. Also, we focused on the emission sources and the comparison of the PAH mixtures to assess similitude among the sampling points. PM10-bound PAHs levels were monitored at three rural locations (north, center, and south) of Spain between April 2017 and February 2018. The study revealed that there were substantial differences regarding the levels of ΣPAHs, being higher in the central zone (IS; 65.4mg/m3), then in the south (VA; 35.8ng/m3) and finally in the north (NA; 20.9ng/m3). IS and VA showed a similar distribution of emission sources, and temperature and wind speed seemed to influence negatively over the levels of PAHs likely. At both locations, PAH levels ran parallel throughout the year, with maximum levels during cold seasons and a greater presence of high molecular weight PAHs; however, the levels of PAHs and the most representative PAHs differed. On the other hand, NA was characterized for having another distribution of emission sources, which determined other representative PAHs, higher levels during spring, and a similar presence of high/medium/low molecular weight. Finally, the levels of ambient air PAHs represented an acceptable risk to people.

GC-MS determination of the content of polycyclic aromatic hydrocarbons in bread and potato Tahdig prepared with the common edible oil.

The polycyclic aromatic hydrocarbon (PAH) content of the Tahdig of the breads and potatoes prepared with edible oil was determined by GC-MS. The Tahdigs of bread and potato were baked under the same condition (volume of any oil 40cc, temperature 180°C, time 30min). Polycyclic aromatic hydrocarbon determination was performed by an Agilent 6890N Gas chromatography with mass selective detector, equipped with a capillary column. The highest contents of PAHs in Tahdig of bread and Tahdig of potato were observed in canola with 550 ± 3.9ng/kg and sesame with 408.3 ± 41ng/kg. The mean of PAH content was significantly higher in the Tahdig of bread compared to the Tahdig of potato (p < 0.05). Among the 16 PAHs examined by GC/MS, 10 PAHs were detected. The amount of high molecular weight (HMW) PAHs were significantly more than low molecular weight (LMW) PAHs (p < 0.05). Benzo [b]fluoranthene and benz[a]anthracene concentrations were significantly more than the other detected compounds (p < 0.05). Due to high PAH contamination of both Tahdig groups, the consumption of Tahdig (any type) was not recommended.

Aerobic and Anaerobic Bacterial and Fungal Degradation of Pyrene: Mechanism Pathway Including Biochemical Reaction and Catabolic Genes.

Microbial biodegradation is one of the acceptable technologies to remediate and control the pollution by polycyclic aromatic hydrocarbon (PAH). Several bacteria, fungi, and cyanobacteria strains have been isolated and used for bioremediation purpose. This review paper is intended to provide key information on the various steps and actors involved in the bacterial and fungal aerobic and anaerobic degradation of pyrene, a high molecular weight PAH, including catabolic genes and enzymes, in order to expand our understanding on pyrene degradation. The aerobic degradation pathway by Mycobacterium vanbaalenii PRY-1 and Mycobactetrium sp. KMS and the anaerobic one, by the facultative bacteria anaerobe Pseudomonas sp. JP1 and Klebsiella sp. LZ6 are reviewed and presented, to describe the complete and integrated degradation mechanism pathway of pyrene. The different microbial strains with the ability to degrade pyrene are listed, and the degradation of pyrene by consortium is also discussed. The future studies on the anaerobic degradation of pyrene would be a great initiative to understand and address the degradation mechanism pathway, since, although some strains are identified to degrade pyrene in reduced or total absence of oxygen, the degradation pathway of more than 90% remains unclear and incomplete. Additionally, the present review recommends the use of the combination of various strains of anaerobic fungi and a fungi consortium and anaerobic bacteria to achieve maximum efficiency of the pyrene biodegradation mechanism.

Baseline distributions and sources of polycyclic aromatic hydrocarbons (PAHs) in reef-associated sediments of Vembar group of Islands, Gulf of Mannar, India

The study aims to investigate the source and concentration of PAH fractions in the reef sediments of the Vembar group of Islands, Gulf of Mannar, India. The concentration of PAHs ranged from 0.36 to 15.98 ng/g. The reef environment was less contaminated with low-molecular-weight PAH fractions. The accumulation of the LMW-PAH fraction was very less, whereas the HMW fraction was derived from pyrolytic sources. The level of low and high molecular weight PAHs was lower than the level of Effective Range Median (ERM) and Effective Range Low (ERL).The calculated total TEQ value ranged from ND to 10.24 ng/g in the reef sediments.

The partitioning behavior of PAHs between settled dust and its extracted water phase: Coefficients and effects of the fluorescent organic matter

The occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) in a city of Central China were determined in the settled dust and its extracted water phase from different land use types and bus stops in Nanchang City. The physicochemical properties of its water extracted dissolved organic matter (WEOM) were characterized to investigate the effect of fluorescence organic matter on the dust-water partitioning coefficients (Kd) using three-dimensional excitation-emission matrix fluorescence spectroscopy combined parallel factor analysis. Results showed that the range of ∑PAHs in settled dust and the extracted water phase was 0.05–15.92 μg·g−1 and 2–211 ng·L−1, respectively. These PAHs mostly came from the combustion of biomass. The risk assessment showed that PAHs in dust had no obvious health risk (less than the magnitude of 10−6). Additionally, the high molecular weight (HMW) PAHs and the low molecular weight (LMW) PAHs were preferentially adsorbed by dust and the dissolved portion, respectively. It was confirmed by the relatively high logKd values of 4.23 for the HMW-PAHs. Pearson correlation analysis suggested that the higher concentration of dissolved organic carbon and humic-like substance were in favor of PAHs in dust released into waters. This study can provide information on pollution control when considering the impact of fluorescent organic matter on the fate and transport of PAHs.

Single-site source apportionment modeling of PM2.5-bound PAHs in the Tehran metropolitan area, Iran: Implications for source-specific multi-pathway cancer risk assessment

This study was designed to assess the occurrence, relationships, sources, spatiotemporal variations, and source-specific multi-pathway cancer risk of PM2.5-bound PAHs at three urban environments in Tehran, Iran during a one-year campaign (2018–2019). The mean concentrations of PM2.5-bound ∑16PAHs were 24.6, 26.7, and 38.9 ng m−3 in HFT, AZD, and SHR sites, respectively. High molecular weight (HMW) PAHs were the main PAHs in the fine particle phase (76–83.4%) compare to low molecular weight (LMW) PAHs (16.6–24%). Redundancy analysis (RDA) showed that relative humidity (RH) and temperature (T) along with O3, NO2, and PM2.5 were critical driving factors affecting PAHs concentrations. Positive matrix factorization (PMF) extracted five PAHs emission sources: heavy-duty vehicles, light-duty vehicles, petrogenic, natural gas and coal/biomass combustion, industrial emissions, with different source contributions for each sampling site. The principal component analysis-multilinear regressions (PCA-MLR) and diagnostic ratios (DRs) methods indicated that the pyrogenic sources were the major sources of PM2.5-bound PAHs. The coefficient of divergence (COD) and Pearson correlation coefficient (R) of PAHs compounds and PMF derived source contributions (ng m−3) at paired sites indicated a relatively divergent spatiotemporal distribution. Based on incremental lifetime cancer risk (ILCR) levels of ∑PAHs source contributions, adults showed a more significant risk (1.33E-2.28E-05) than children (5.40E-9.22E-06). Source-specific-ILCR indicated that heavy-duty vehicles and natural gas-coal/biomass combustion emissions had the highest cancer risk contributions than the other apportioned sources.

Soil bacterial diversity and functionality are driven by plant species for enhancing polycyclic aromatic hydrocarbons dissipation in soils

Plant-microorganisms symbiosis has been widely used in developing strategies for the rhizoremediation of polycyclic aromatic hydrocarbon (PAHs) contaminated agricultural soils. However, understanding the potential mechanisms for using complex plant-microbe interactions to enhance rhizoremediation in contaminated soils is still limited. In this study, rhizosphere microbiomes were established by cultivating four types of cover crops for 15 months in a PAHs-contaminated field. The results showed that the PAHs removal rates were significantly higher in rhizosphere soils (55.2–82.3%) than the bare soils (20.5%). Of the four cover crops, the rhizosphere soils associated with the alfalfa and clover had higher removal rates for high molecular weight (HMW) PAHs (78.5–87.1%) than the grasses (39.0–46.2%). High-throughput sequencing analysis showed that bacterial community structure between the planted and bare soils, and among four cover crops rhizosphere soils were significantly different. The rhizosphere soils associated with the alfalfa and clover had more abundant degradation-related taxa. Correlation network analysis showed that bacterial communities with high removal rates have stronger interactions. Metagenome analysis indicated that the relative abundance of the key functional genes involved in PAHs degradation and nutrient metabolisms were significantly higher in rhizosphere soils, especially for alfalfa and clover. Overall, this study provides new insights for us to understand the mechanisms by different plants enhancing PAHs dissipation from the viewpoint of microbiology.

Biodegradation performance and diversity of enriched bacterial consortia capable of degrading high-molecular-weight polycyclic aromatic hydrocarbons

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are key organic pollutants in the environment that pose threats to the ecosystem and human health. The degradation of high molecular weight (HMW) PAHs by enriched bacterial consortia has been previously studied, while the involved metabolisms and microbial communities are still unclear and warrant further investigations. In this study, five bacterial consortia capable of utilizing different PAHs (naphthalene, anthracene, and pyrene) as the sole carbon and energy sources were enriched from PAH-contaminated soil samples. Among the five consortia, consortium TC exhibited the highest pyrene degradation efficiency (91%) after 19 d of incubation. The degradation efficiency was further enhanced up to 99% by supplementing yeast extract. Besides, consortium TC showed tolerances to high concentrations of pyrene (up to 1000 mg/L) and different heavy metal stresses (including Zn2+, Cd2+, and Pb2+). The dominant genus in consortium TC, GS, and PL showing relatively higher degradation efficiency for anthracene and pyrene was Pseudomonas, whereas consortium PG and GD were predominated by genus Achromobacter and class Enterobacteriaceae, respectively. Consortium TC, as a highly efficient HMW PAH-degrading consortium, could be applied for synergistic biodegradation of HMW PAHs and in situ bioremediation of the sites contaminated with both PAHs and heavy metals.

Using a hybrid approach to apportion potential source locations contributing to excess cancer risk of PM2.5-bound PAHs during heating and non-heating periods in a megacity in the Middle East

Polycyclic aromatic hydrocarbons (PAHs) represent one of the major toxic pollutants associated with PM2.5 with significant human health and climate effects. Because of local and long-range transport of atmospheric PAHs to receptor sites, higher global attentions have been focused to improve PAHs pollution emission management. In this study, PM2.5 samples were collected at three urban sites located in the capital of Iran, Tehran, during the heating and non-heating periods (H-period and NH-period). The US EPA 16 priority PAHs were analyzed and the data were processed to the following detailed aims: (i) investigate the H-period and NH-period variations of PM2.5 and PM2.5-bound PAHs concentrations; (ii) identify the PAHs sources and the source locations during the two periods; (iii) carry out a source-specific excess cancer risk (ECR) assessment highlighting the potential source locations contributing to the ECR using a hybrid approach.Total PAHs (TPAHs) showed significantly higher concentrations (1.56–1.89 times) during the H-period. Among the identified PAHs compounds, statistically significant periodical differences (p-value < 0.05) were observed only between eight PAHs species (Nap, BaA, Chr, BbF, BkF, BaP, IcdP, and DahA) at all three sampling sites which can be due to the significant differences of PAHs emission sources during H and NH-periods. High molecular weight (HMW) PAHs accounted for 52.7% and 46.8% on average of TPAHs during the H-period and NH-period, respectively. Positive matrix factorization (PMF) led to identifying four main PAHs sources including industrial emissions, petrogenic emissions, biomass burning and natural gas emissions, and vehicle exhaust emissions. Industrial and petrogenic emissions exhibited the highest contribution (19.8%, 27.2%, respectively) during the NH-period, while vehicle exhaust and biomass burning-natural gas emissions showed the largest contribution (40.7%, 29.6%, respectively) during the H-period. Concentration weighted trajectory (CWT) on factor contributions was used for tracking the potential locations of the identified sources. In addition to local sources, long-range transport contributed to a significant fraction of TPHAs in Tehran both during the H- and NH-periods. Source-specific carcinogenic risks assessment apportioned vehicle exhaust (44.2%, 2.52 × 10−4) and biomass burning-natural gas emissions (33.9%, 8.31 × 10−5) as the main cancer risk contributors during the H-period and NH-period, respectively. CWT maps pointed out the different distribution patterns associated with the cancer risk from the identified sources. This will allow better risk management through the identification of priority PAHs sources.

The remediation potential for PAHs of Verbascum sinuatum L. combined with an enhanced rhizosphere landscape: A full-scale mesocosm experiment

A full-scale mesocosm study was conducted to depict how integrated biological systems interact to adapt to contaminant stress and improve remediation of polycyclic aromatic hydrocarbons (PAHs)contaminated soils. The combination of Verbascum sinuatum L. and microbial consortium (fungi and bacteria) was employed along with three differently contaminated soils. After 240 days the highest PAHs removal (up to 68 %) and 6-rings compounds decrease was found in soil with lower pollution and cation exchange capacity. V. sinuatum showed a significant adaptability over time in terms of redox biology. Soil enzyme activities and microscopic evidences proved a rising plant-microorganisms association and a successful mycorrhization, arising from the inoculation of our consortia. In addition, an enhanced richness of PAHs degrading genes was achieved. Microbial co-metabolism, helped by the establishment of complex relationships with hosting plant, demonstrated to be suitable for the degradation of high molecular weight PAHs and represents a biotechnology with great prospects.

Fate of four Different Classes of Chemicals Under Aerobic and Anaerobic Conditions in Biological Wastewater Treatment

The removal mechanisms and extent of degradation of 28 chemicals (triclosan, fifteen polycyclic aromatic hydrocarbons, four estrogens, and eight polybrominated diphenyl ether congeners) in different biological treatment systems [activated sludge, up-flow anaerobic sludge blanket reactor (UASB) and waste stabilization pond (WSP)] was investigated to provide insights into the limits of engineered biological treatment systems. This was done through degradation experiments with inhibition and abiotic controls in static reactors under aerobic and anaerobic conditions. Estrogens showed higher first order degradation rates (0.1129 h−1) under aerobic conditions with activated sludge inocula followed by low molecular weight (LMW) PAHs (0.0171 h−1), triclosan (0.0072 h−1), middle (MMW) (0.0054 h−1) and high molecular weight PAHs (HMW) (0.0033 h−1). The same trend was observed under aerobic conditions with a facultative inoculum from a WSP, although at a much slower rate. Biodegradation was the major removal mechanism for these chemicals in the activated sludge and WSP WWTPs surveyed. Photodegradation of these chemicals was also observed and varied across the group of chemicals (estrogens (light rate = 0.4296 d−1; dark = 0.3900 d−1) degraded faster under light conditions while reverse was the case for triclosan (light rate = 0.0566 d−1; dark = 0.1752 d−1). Additionally, all the chemicals were resistant to anaerobic degradation with UASB sludge, which implies that their removal in the UASB of the surveyed WWTP was most likely via sorption onto solids. Importantly, the first order degradation rate determined in this study was used to estimate predicted effluent concentrations (PECs). The PECs showed good agreement with the measured effluent concentrations from a previous study for these treatment systems.

Effects of polycyclic aromatic hydrocarbon structure on PAH mineralization and toxicity to soil microorganisms after oxidative bioremediation by laccase

While bioremediation using soil microorganisms is considered an energy-efficient and eco-friendly approach to treat polycyclic aromatic hydrocarbon (PAH)-contaminated soils, a variety of polar PAH metabolites, particularly oxygenated ones, could increase the toxicity of the soil after biodegradation. In this study, a typical bio-oxidative transformation of PAH into quinones was investigated in soil amended with laccase using three PAHs with different structures (anthracene, benzo[a]anthracene, and benzo[a]pyrene) to assess the toxicity after oxidative bioremediation. The results show that during a 2-month incubation period the oxidation process promoted the formation of non-extractable residues (NERs) of PAHs, and different effects on mineralization were observed among the three PAHs. Oxidation enhanced the mineralization of the high-molecular-weight (HMW) PAHs (benzo[a]anthracene and benzo[a]pyrene) but inhibited the mineralization of the low-molecular-weight (LMW) PAH (anthracene). The inhibition of anthracene suggests increased toxicity after oxidative bioremediation, which coincided with a decrease in soil nitrification activity, bacterial diversity and PAH-ring hydroxylating dioxygenase gene copies. The analysis of PAH metabolites in soil extract indicated that oxidation by laccase was competitive with the natural transformation processes of PAHs and revealed that intermediates other than quinone metabolites increased the toxicity of soil during subsequent degradation. The different metabolic profiles of the three PAHs indicated that the toxicity of soil after PAH oxidation by laccase was strongly affected by the PAH structure. Despite the potential increase in toxicity, the results suggest that oxidative bioremediation is still an eco-friendly method for the treatment of HMW PAHs since the intermediates from HMW PAHs are more easily detoxified via NER formation than LMW PAHs.

Ecotoxicological risk and health risk characterization of polycyclic aromatic hydrocarbons (PAHs) in terrestrial soils of King George Island, Antarctica

We studied the concentrations, characteristics, ecological risk, and health risk of 12 probably carcinogenic polycyclic aromatic hydrocarbons (PAHs) in KGI soils of Antarctica. Measured concentrations of 12 PAHs ranged from 1.83 to 32.9 ng g−1 with an average of 11.9 ± 8.13 ng g−1. The assessment of ecological risks used methods that were based on total toxicity equivalency concentrations (TEQs) and a risk quotient (RQ), which can be used to sensitively and accurately assess ΣPAHs. The results indicated that PAHs in the soils of KGI presented a low risk level to living organisms in the soil and to plants. The low molecular weight PAHs presented a much greater ecological risk than high molecular weight PAHs in KGI soils, and the levels of these ecological risks were classified as low compared to those of previous studies in other areas. The total values of incremental lifetime cancer risk (ILCR) for children and adults were 2.34 × 10−8 and 1.73 × 10−8, respectively. Soil samples from KGI that were contaminated with PAHs still exhibited risks that were much lower than that of the baseline value. The results of this investigation provide a database for contamination evaluation, risk assessment of ecological and human health in PAH-contaminated sites.

Isolation, characterization and optimization of chrysene degradation using bacteria isolated from oil-contaminated water.

Polyaromatic hydrocarbons (PAHs) are uncharged, non-polar molecules generated from natural and anthropogenic activities, where the emissions from anthropogenic activities predominate. Chrysene is a high molecular weight PAH, which is found to be highly recalcitrant and mutagenic in nature. The aim of this study was to isolate chrysene-degrading microorganisms from oil-contaminated water and to enhance their degradative conditions using design expert. From the various samples collected, 19 bacterial strains were obtained through enrichment culture and the one which showed highest activity was identified by 16S rRNA sequencing as Bacillus halotolerans. Under optimum conditions of 100 mg/L chrysene concentration, 1,000 mg/L nitrogen source, and pH 6, B. halotolerans exhibited 90% chrysene degradation on sixth day. Positive results for the enzymes laccase and catechol 1,2 dioxygenase confirmed the ability for chrysene degradation by the isolated strain. Major metabolic intermediate determined in gas chromatography-mass spectrometry (GCMS) analysis was diisooctyl phthalate. Hence it can be concluded that B. halotolerans can be a promising candidate for the removal of high molecular weight (HMW) hydrocarbons from contaminated environments.

Deciphering Historical Water-Quality Changes Recorded in Sediments Using eDNA

Reservoir sediments harbor abundant bacterial communities that are sensitive to substances transferred from the water column and might record historic water quality in environmental DNA (eDNA). The unique bacterial community along the sediment profile were retrieved based on eDNA in a reservoir to investigate potential links between water quality and the microbial population on a long-time scale. Bacterial communities in sediment samples gathered into three clusters along the depth (depths of 18–38, 8–18, and 1–7 cm). These three sections accumulated during three periods in which water quality was recorded in history (the pristine stage, degraded stage and remediated stage). Sediment samples from the degraded stage had lower microbial community evenness and diversity and higher microgAMBI indices than the other two sections, suggesting that poor water quality during that period was recorded in sedimental eDNA. After decades of biogeochemical cycles, statistical analysis revealed that the main factors affecting the microbial community were bromine, chlorine, and high molecular-weight PAHs in sediments from the degraded stage. The relevant functional groups Dehalococcoidia, Gemmatimonadales, Sva0485, Burkholderiales and Xanthomonadales might be indicators of the historical loading of these pollutants. Amending the microgAMBI index with our functional group of pollution can better illustrate the significant long-term environmental changes caused by historic anthropogenic activities. In sediments from the pristine stage with less pollution input, DIC (dissolved inorganic carbon) from the karst landform was the dominant factor controlling microbial communities. Whereas, the surface sediments, which accumulated during the remediated stage, had more correlation with chemistry, such as sulfate and heavy metals, in the overlying water. Our research revealed that historical changes in the water condition, that can be affected by anthropogenic activities, can be depicted by changes in the bacterial communities stored in the sediment using sedimental eDNA. Assessments of the bacterial communities in the sediments, either by describing their biodiversity or using particular species as indicators, would be potential proxies to describe historical environmental development of microbial communities.