Polycyclic Aromatic Hydrocarbons In Marine Sediments Research Articles

Effects of electron acceptors and donors on anaerobic biodegradation of PAHs in marine sediments

Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants accumulated in the environment. PAHs' bioremediation in sediments can be promoted by adding electron acceptor (EA) and electron donor (ED). Bicarbonate and sulfate were chosen as two EAs, and acetate and lactate were selected as two EDs. Six groups of amendments were added into the sediments to access their role in the anaerobic biodegradation of five PAHs, containing phenanthrene, anthracene, fluoranthene, pyrene, and benzo[a]pyrene. The concentrations of PAHs, EAs and EDs, electron transport system activity, and microbial diversity were analyzed during 126-day biodegradation in serum bottles. The HA group (bicarbonate and acetate) achieved the maximum PAH degradation efficiency of 89.67 %, followed by the SL group (sulfate and lactate) with 87.10 %. As the main PAHs degrading bacteria, the abundance of Marinobacter in H group was 8.62 %, and the addition of acetate significantly increased the abundance of Marinobacter in the HA group by 75.65 %.

Effect of terminal electron acceptors on the anaerobic biodegradation of PAHs in marine sediments

The existing polycyclic aromatic hydrocarbons (PAHs) in marine sediment has become a critical threat to biological security. Terminal electron acceptor (TEA) amendment has been applied as a potential strategy to accelerate bioremediation in sediment. HCO3-, NO3-, and SO42- were separately added to anaerobic sediment system containing five kinds of PAH, namely, phenanthrene, anthracene, fluoranthene, pyrene and benzo(a)pyrene. PAH concentration, PAH metabolites, TEA concentration, and electron transport system (ETS) activity were investigated. The HCO3- amendment group achieved the max PAH degradation efficiency of 84.98 %. SO42- group led to the highest benzo(a)pyrene removal rate of 69.26 %. NO3- had the lowest PAH degradation rate of 76.16 %. ETS activity test showed that NO3- significantly inhibited electron transport activity in the sediment. The identified PAH metabolites were the same in each group, including 4,5-dimethylphenanthrene, 3-acetylphenanthrene, 9,10-anthracenedione, pyrene-7-hydroxy-8-carboxylic acid, anthrone, and dibenzothiophene. After 126 d's anaerobic degradation at 25 °C, the utilization of HCO3- and SO42- as selected TEAs promoted the PAH biodegradation performance better than the utilization of NO3-.

Hydrodynamic cavitation activation of persulfate for the degradation of polycyclic aromatic hydrocarbons in marine sediments

Hydrodynamic cavitation (HC) coupled with persulfate (PS)-based that resulted in the synergistic degradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated marine sediments. The effects of HC injection pressure and Σ[PAH]: [PS] on the rate and extent of PAH degradation were studied in the pressure range of 0.5–2.0 bar, PS concentration rage of 2 × 10−4 to 2 × 10−2 M or Σ[PAH]: [PS] of 1:10–1000, and reaction time of 20–60 min. A pseudo-first-order rate law fitted PAHs removal kinetics well. The degradation rate constant increased with injection pressure, reaching the maximum level at 0.5 bar, then decreased at injection pressure became greater than 0.5 bar. The results showed that PAH removal was 84% by the combined HC and PS process, whereas, HC alone only achieved a 43% removal of PAHs in marine sediments under the optimal inlet pressure of 0.5 bar at PS concentration of 2 × 10−2 M in 60 min. The HC‒PS system effectively removed PH, PY, FLU, BaA, and CH at 91, 99, 91, 84, and 90%, respectively. The maximum removal of 6-, 5-, 4-, 3-, and 2-ring PAHs was 89, 87, 84, 76, and 34%, respectively. Major reactive oxygen species (ROSs), namely, SO4−• and HO•, were responsible for PAHs degradation. Results clearly highlighted the feasibility of HC−PS system for the clean-up of PAHs-laden sediments in particular and other recalcitrant organic contaminants in general.

PAH bioaccumulation in two polluted sites along the eastern coast of the Red Sea, Saudi Arabia

Significant amounts of polycyclic aromatic hydrocarbons (PAHs) accumulate in specific habitats and organisms, such as mangroves and benthic organisms, due to the PAHs’ direct attachment to sediments in the environment or the feeding activity of the organisms, especially in contaminated coastal areas. The present study investigates the effect of sewage effluents on the bioaccumulation of PAHs in two polluted sites along the coastal area of Jeddah city. PAH levels in the mangrove sediments, roots, and leaves ranged between 230.09 and 17.94, 32.79 and 409.86, and 111.14 and 795.2 ng/g, respectively, following the general trend of sediments < roots < leaves. Though all mangrove roots showed bioaccumulation factors (BAFroots) higher than 1, the leaves bioaccumulation factors (BAFleaves) exceeded 26, clearly indicating PAHs accumulated not only via a translocation pathway but also from the surrounding atmosphere. These results suggest that mangroves could serve as an in situ eco-friendly resource for the dissipation of PAHs in marine sediments and the atmosphere. Although higher levels of PAHs were detected in Al-Arbaeen Lagoon sediments (ranging between 89.18 and 1056.46 ng/g), lower levels of PAHs were observed in the gastropod Littorina Littorea (range 113.21–265.96 ng/g) in this area, with biota-sediment accumulation factors (BSAF) ranging from 0.23 to 2.10. Only one Al-Arbaeen site presented sediments with a petrogenic origin, with a BSAF value higher than 1 in the gastropod. Based on sediment quality guidelines, adverse biological effects should rarely occur at the studied sites under the present PAH levels.

The removal of polycyclic aromatic hydrocarbons (PAHs) from marine sediments using persulfate over a nano-sized iron composite of magnetite and carbon black activator

The presence of polycyclic aromatic hydrocarbons (PAHs) in sediments is a potential eco-environmental health risk. Fe3O4-carbon black (FCB) nanocomposite was synthesized by a simplified precipitation method and used to activate persulfate (PS) for the degradation of PAHs in contaminated marine sediments. The carbon black was formed by amorphous non-graphite and the Fe3O4 composed of magnetite of cubic crystal structures. FCB exhibited typical ferromagnetic characteristics and high degradation of PAHs in marine sediments via PS oxidation. The pseudo‒first‒order rate constant of PAHs degradation significantly increased with PS dosage but decreased with increase in pH from 3 to 9. Langmuir-Hinshelwood model described the kinetics of PAHs degradation well. The observed rate constant, kobs (1.8 × 10−2 h−1), at Σ[PAH]: [PS] = 1:104 (the optimal condition) was almost 2.7 times that of 1:1 (kobs = 6.6 × 10−3 h−1). At the PS concentration of 2 × 10−4 M (or a Σ[PAH]: [PS] = 1:10), pH 3, and 3 g/L of FCB, the FCB/PS system exhibited 94, 97, 94, 98, and 93% degradation of total PAH (Σ[PAH]), PY, FLU, CH, and PH, respectively, while the highest PAH degradation was 99, 98, 97, and 97%, respectively, for 6‒, 5‒, 4‒ and 3‒ring PAHs. The presence of Fe2+/Fe3+ redox pairs greatly enhanced the catalytic capacity of FCB leading to an increase in PAH degradation. Electron paramagnetic resonance (EPR) spectroscopy revealed SO4–• and HO• radicals as major reactive species for PAHs degradation in FCB/PS system. Results clearly indicated the great potential of FCB for remediation of PAHs contaminated marine sediments.

Distribution and Human Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyls (PCBs) in Marine Sediments and Seafood from Gunsan Coast of Korea

Distributions of 16 PAHs and 82 PCBs (including dioxin-like PCBs, DL-PCBs, and non-dioxin-like PCBs, NDL-PCBs) were investigated in sediment and seafood samples collected from the Gunsan coast, Korea. Total PAH (Σ16PAH) concentrations in sediments were in a range of 0.09~108 (mean: 57.9) ng/g-dry and gradually decreased outwardly. PAHs in marine sediments were originated from both combustion processes and petroleum sources. The total PCB (Σ82PCB) concentrations in sediments were in a range of nd (not detected)-0.64 (mean: 0.27) ng/g-dry, and DL-PCB (Σ12 dioxin-like PCB) were in a range of nd-0.293 (mean 0.054) pg-TEQ/g-dry. DL-PCB concentrations were correlated with NDL-PCB concentrations. In this study, the concentrations of PAHs and PCBs in marine sediments did not exceed the ecotoxicological values. Total PAH concentrations ranged from nd to 24.3 (mean: 5.35) ng/g-wet, benzo[a]pyrene (BaP) was not detected in seafood samples and the concentrations of Σ4PAH (BaP, chrysene, benzo[a]anthracene, and benzo[b]fluoranthene; nd-18.5 ng/g-wet) were lower than the maximum level (30 ng/g-wet) set by EU. The concentrations of NDL-PCBs in seafood samples were in a range of nd-0.19 (mean: 0.08) ng/g-wet less than 1% of the EU-set maximum level. The DL-PCB concentrations were below 0.1 pg-TEQ/g-wet, less than 1% of the EU-set maximum level. Human risk assessment of PAHs and PCBs via seafood consumption was carried out, and both lifetime cancer risk and non-cancer risk were low. Key Words: PAHs, Dioxin-like PCBs, Sediment, Seafood, Human risk assessment

Determination of 16 polycyclic aromatic hydrocarbons in marine sediments by gas chromatography-tandem mass spectrometry with accelerated solvent extraction

A method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) with accelerated solvent extraction (ASE) was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in marine sediments. The sediment samples were extracted with hexane-acetone (1:1, v/v). The extracts were dehydrated with anhydrous sodium sulfate, and concentrated with a termovap sample concentrator. The concentrated solutions were further cleaned up with Si SPE columns. The purified solutions were then isolated by HP-5MS column (30 m×0.25 mm×0.25 μm). The analytes were detected using electron impact source under multiple reaction monitoring (MRM) mode. The results showed that the 16 PAHs had good linearities in the range of 0.01-1.00 mg/L with the correlation coefficients (R) greater than 0.997. The spiked recoveries of the 16 PAHs were in the range of 75.8%-97.8%, and the relative standard deviations (RSDs) were less than 10%. The method detection limits (MDLs) of the 16 PAHs ranged from 0.048-0.234 μg/kg with 20.0 g sampling weight. This method is suitable for the determination of trace PAHs in marine sediments.

The occurrence of PAHs and faecal sterols in Dublin Bay and their influence on sedimentary microbial communities

The source, concentration, and potential impact of sewage discharge and incomplete organic matter (OM) combustion on sedimentary microbial populations were assessed in Dublin Bay, Ireland. Polycyclic aromatic hydrocarbons (PAHs) and faecal steroids were investigated in 30 surface sediment stations in the bay. Phospholipid fatty acid (PLFA) content at each station was used to identify and quantify the broad microbial groups present and the impact of particle size, total organic carbon (%TOC), total hydrogen (%H) and total nitrogen (%N) was also considered. Faecal sterols were found to be highest in areas with historical point sources of sewage discharge. PAH distribution was more strongly associated with areas of deposition containing high %silt and %clay content, suggesting that PAHs are from diffuse sources such as rainwater run-off and atmospheric deposition. The PAHs ranged from 12 to 3072ng/g, with 10 stations exceeding the suggested effect range low (ERL) for PAHs in marine sediments. PAH isomer pair ratios and sterol ratios were used to determine the source and extent of pollution. PLFAs were not impacted by sediment type or water depth but were strongly correlated to, and influenced by PAH and sewage levels. Certain biomarkers such as 10Me16:0, i17:0 and a17:0 were closely associated with PAH polluted sediments, while 16:1ω9, 16:1ω7c, Cy17:0, 18:1ω6, i16:0 and 15:0 all have strong positive correlations with faecal sterols. Overall, the results show that sedimentary microbial communities are impacted by anthropogenic pollution.

Determination of PAHs in marine sediments: analytical methods and environmental concerns

Polycyclic Aromatic Hydrocarbons (PAHs) are one of the major categories of pollutants entering the marine environment and finally accumulating in the sediments. Their occurrence raises major concerns for human health, especially during coastal activities (bathing waters, aquaculture, etc), having combined adverse effects still largely unknown when they are present as mixtures. Moreover, during their remobilization (e.g. dredging activities), their bioavailability can increase resulting in a risk for marine environment. Several of them are known to be potential human carcinogens including benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[a]pyrene and benzo[ghi]perylene. Therefore they have been included in the priority list of the Water Framework Directive 2000/60/EC and also sixteen of them have been regulated by the US EPA as priority pollutants, and their distributions in the environment and potential human health risks have become the focus of much attention. The determination of PAHs in environmental matrices has been subject of great scientific attention during the latest years, as the accuracy and sensitivity of analytical methods need to be improved in order to be able to detect the compounds of interest in a complex matrix such as sediments. Therefore, significant research is being devoted to the optimization of analytical methodologies. A great number of studies have been performed on PAHs analysis in marine sediments. Various analytical procedures based on gas chromatographic analyses are reviewed and comparatively discussed in this paper.

Presence, distribution, and origins of polycyclic aromatic hydrocarbons (PAHs) in sediments from Bahía Blanca estuary, Argentina

This paper is the first comprehensive survey of polycyclic aromatic hydrocarbons (PAHs) in coastal sediments in Bahia Blanca, Argentina, and provides useful information on their levels of concentration, composition, and sources of these pollutants. The total concentrations of PAHs ranged from 15 to 10,260 ng g(-1). The highest contents (mean 3,315 ng g(-1)) of total PAHs in marine sediments were found in the inner channels of the estuary, while the lower ones (204 ng g(-1)) belong to samples collected far away from contamination sources. The global average recorded in this study (1,500 ng g(-1)) indicates that the studied area lies within the referenced category of industrialized coastal zones under chronic pollution. The diagenetic PAH contribution was found to be negligible at all sampled locations; however, the calculation of molecular ratios determined an overimposition of pyrolitic PAHs over the petrogenic input. Further, the use of principal components analysis (PCA) clearly separated ring group compounds and enabled the determination of pyrolitic/combustion PAHs dominancy.

Persistent Organic Pollutants in Singapore's Coastal Marine Environment: Part II, Sediments

Polycyclic aromatic hydrocarbons (PAHs) can enter the marine environment from a variety of anthropogenic sources. As some PAHs are known or suspected carcinogens and mutagens, their potential hazard to human health and the natural environment warrants investigation. This is the first reported study on the prevalence and concentration of PAHs in marine sediments from Singapore's coastal environment, and accompanies the report by Basheer et al. (2003) on the measurement of persistent organic pollutants (POPs) in seawater. The concentration of 16 PAH, classified as USEPA priority pollutants were analysed in sediments from 22 sample stations located within the northeastern and southwestern regions of Singapore's marine waters. The total PAH concentration varied between 15.22 μg g-1 and 82.41 μg g-1 in the northeastern region and between 13.63 μg g-1 and 84.92 μg g-1in the southwestern region. The highest concentration of total PAH i.e. 84.92 μg g-1 was recorded at a site adjacent to a petrochemical refinery. Among the sixteen individual PAHs, chrysene, indeno[1,2,3-cd]pyrene and benzo[a]anthracene were most prevalent in the sediments. The relatively low kinetic/thermodynamic isomer ratios for PAHs suggest that PAHs of pyrogenic origin are predominant in Singapore's coastal environment. The distribution of higher molecular weight i.e. (4–5 ring) individual PAHs corresponded to mixture profiles typical of those originating from high temperature combustion processes subjected to photolytic degradation during long-range atmospheric transportation. A comparison of total PAH concentration data for sediments collected from Singapore relative to those reported for other countries indicates a moderate level of PAH contamination in Singapore's coastal marine sediments.

Routine analysis of hydrocarbons, PCB and PAH in marine sediments using supercritical CO 2 extraction

Automated Supercritical Fluid Extraction (SFE), using CO 2, was tested and optimised for routine analysis of hydrocarbons (THC), polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) in marine sediments. The aim of the exercise was to reduce the amount of solvents used and to reduce the manual handling time for each sample. The sediments contained elemental sulphur, which was removed during the extraction step using activated Cu. Similar recoveries and reproducibility where found for THC when conventional solvent extractions and SFE where compared. Modifying the CO 2 with methanol was necessary to obtain extraction recoveries similar to conventional extraction methods for PCB and PAH.

Optimization of microwave-assisted solvent extraction of polycyclic aromatic hydrocarbons in marine sediments using a microwave extraction system with high-performance liquid chromatography-fluorescence detection and gas chromatography-mass spectrometry

In the present study, a microwave-assisted solvent extraction (MASE) technique using a microwave extraction system (MES) has been developed for the extraction of polycyclic aromatic hydrocarbons (PAHs) from marine sediment. The optimum MASE conditions can be obtained by performing the mixed-level orthogonal array design (OAD) procedure. A comparison between the Soxhlet extraction method and the MASE technique showed that although both techniques gave comparable results on certified reference materials (CRM) HS-4 and HS-6, the MASE technique allows the use of less solvent and is also time-saving and cost-effective without affecting its extraction efficiency. The optimum MASE technique was coupled to two analytical techniques: high-performance liquid chromatography (HPLC) with both ultraviolet (UV) and fluorescence detectors and gas chromatography-mass spectrometry (GC-MS) for the qualitative and quantitative screening of PAHs in CRM and “real world” samples. Recoveries of PAHs from two CRMs were all above 73.3%. The concentration of PAHs in marine sediment collected from primary industrial areas was between 0.03 and 0.35 μg/g on a dry weight basis.