Assessing biodegradation potential of PAHs in complex multi-contaminant matrices

Applicability of non-exhaustive extraction procedures with Tenax and HPCD

Present paper describes optimization of the method of quantitative determination of total petroleum hydrocarbons in soil samples using headspace solid - phase microextraction (SPME) in combination with gas chromatography - mass spectrometry (GC-MS). Effects of moisture content and solvent additives were studied. It was established that an increase of the moisture content in soil leads to an increase of the response of petroleum hydrocarbons reaching its maximum at 15-20% depending on the soil type and concentration of total petroleum hydrocarbons followed by its gradual decrease. For the same concentration of petroleum hydrocarbons, an increase of moisture content in soil from 0 to 20% may lead to a 15x increase of total petroleum hydrocarbons response by solid - phase microextraction. Determination of total petroleum hydrocarbons in soils by SPME -GC-MS without moisture control of samples may lead to large errors, especially at low concentrations. It was established that addition of the solvent to a soil-water mixture allows dissolution of an oil film on the water surface and provides better extraction of hydrocarbons from soil to water phase. To avoid effect of moisture content on the extraction efficiency and more precise analysis of the real samples, addition of the excess distilled water must be done. Addition of the polar organic solvent to a soil-water mixture (10% isopropanol) allows dissolution of an oil film on the water surface and provides linear dependence of extraction efficiency vs total petroleum hydrocarbons content in soil. Testing of the optimized method on model soil samples provided quantitative data, results being in 30-120% range from the real values.

Commercially available solid phase extraction (SPE) cartridges were combined with GC–MS for fast cleanup and fractionation of biodiesel/diesel samples in oil fingerprinting analysis. Several commercially available SPE cartridges (e.g., silica gel/cyanopropyl (SiO2/C3–CN) and extractable petroleum hydrocarbons (EPH) fractionation cartridges), were employed for the fractionation of biodiesel/diesel blends into aliphatic, aromatic hydrocarbons, and fatty acid methyl esters (FAMEs). The SiO2/C3–CN (1 g/0.5 g) SPE cartridge could not separate biodiesel from petroleum hydrocarbons effectively, however, the 5 g EPH SPE cartridge successfully separated blended samples into aliphatic, aromatic and FAME fractions by eluting with 15 mL of hexane, 15 mL of dichloromethylene (DCM)/hexane (1:1, v/v), and 18 mL of DCM, respectively. No cross-elution was observed among aliphatic, aromatic and FAME fractions when the loading mass of blends was less than 8 mg. The relative standard deviations (RSD) for five replicate SPE–GC–MS analyses of 5 mg of diesel blended with 20% biodiesel (volume/volume) and soybean oil ranged from 3.4% to 33.2%, 4.3% to 18.7% and 5.4% to 29.2% for selected alkane, polycyclic aromatic hydrocarbons (PAHs) and FAMEs, respectively. The final recovery rates of surrogates for aliphatic, aromatic and FAME fractions ranged from 82.5 to 91.1%. This developed method was successfully used for the fingerprinting analysis of three simulated blend samples. The concentration profiles of target compounds and the blended level are both comparable to those obtained by the conventional silica gel column–GC–MS method.

Over the last several decades, considerable contamination by hexavalent chromium has resulted from the land disposal of Chromite Ore Processing Residue (COPR). COPR contains a number of hexavalent chromium-bearing compounds that were produced in high temperature industrial processes. Concern over the carcinogenic potential of this chromium species, and its environmental mobility, has resulted in efforts to remediate these waste sites. To provide support to analytical measurements of hexavalent chromium, a candidate National Institute of Standards and Technology (NIST) Standard Reference Material® (SRM 2701), having a hexavalent chromium content of approximately 500 mg kg−1, has been developed using material collected from a waste site in Hudson County, New Jersey, USA. The collection, processing, preparation and preliminary physico–chemical characterization of the material are discussed. A two-phase multi-laboratory testing study was carried out to provide data on material homogeneity and to assess the stability of the material over the duration of the study. The study was designed to incorporate several United States Environmental Protection Agency (USEPA) determinative methods for hexavalent chromium, including Method 6800 which is based on speciated isotope dilution mass spectrometry (SIDMS), an approach which can account for chromium species inter-conversion during the extraction and measurement sequence.

Background.Polycyclic aromatic hydrocarbons (PAHs) are toxic contaminants and pose health risks to humans and the ecosystem due to their persistence in the environment.Objectives.This study determined the concentrations of PAHs in sediment, two species of fish (Drepane africana and Pomadasys jubelini), crabs (Callinectes amnicola) and shrimps (Penaeus notialis) around the Atlas Cove jetty, Lagos, Nigeria.Methods.Polycyclic aromatic hydrocarbons were extracted from fish, shrimp, and crabs that were purchased from local fishermen. Sediments were collected at five locations impacted by ship movement and cargo offloading around the Atlas Cove jetty during the period of June to August 2016, using standard methods. Potential toxicity of PAHs in the sediments on the surrounding aquatic organisms was assessed. The PAHs were analyzed using gas chromatography-mass spectrometry. Human health risk assessment was calculated from biota using dietary daily intake and carcinogenic potencies of individual PAH concentrations.Results.A total of 17 PAH congeners were detected in sediment samples and ten were detected in biota samples. Concentrations of total PAHs obtained in sediment and fish samples ranged from 2.15 - 36.46 mg/kg and 11.89 - 71.06 mg/kg, respectively. The total PAHs concentration pattern follow the order of P. notialis > C. amnicola > P. jubelini (whole) > D. africana (whole) > D. africana (fillet) > P. jubelini (fillet) > sediment. Concentrations of total PAHs were higher in whole fish than in fillet samples (muscle) in both fish species. High values of PAHs were recorded in the dietary intake (0.10 - 2.33 mg/kg body weight/day) of the organisms. Toxic equivalent quotient values (0.01 to 0.10 mg/kg) were observed to be higher than the screening values (0.0014 to 0.0599 mg/kg). In the muscle of Drepane africana and Pomadasys jubelini, splitting and atrophy of the muscle bundles were observed.Conclusions.The concentrations of PAHs in analyzed sediment and organisms were higher than the maximum permissible limit of the United State Environmental Protection Agency (USEPA). Most of the detected PAHs were of petrogenic origin, which is an indication that anthropogenic activities were influencing PAH concentrations.Competing Interests.The authors declare no competing financial interests.

Network-based investigation of petroleum hydrocarbons-induced ecotoxicological effects and their risk assessment

The US Environmental Protection Agency (USEPA) modified its guidance on determining “method detection limits” (MDL) in 2017. The recommended procedures have not yet been applied to the analyses routinely done on filter samples for USEPA’s Chemical Speciation Network (CSN). This paper applies the new USEPA procedure for estimating MDL to Energy Dispersive X-Ray Fluorescence (EDXRF) analysis of atmospheric aerosol samples collected on filters. The procedure involves estimating MDL by two approaches – statistical distributions of unloaded blank sample measurements and lightly loaded, spiked samples – and sets the MDL as the maximum of these two approaches. Spiked samples at low concentrations were developed using an aerosol deposition chamber to follow this approach. The MDL procedure was initially conducted on one EDXRF instrument, and the spike-based MDL was found to be higher than blank-based MDL for 28 of the 31 elements. The blank-based MDL was higher than the spike-based MDL for Si, K and Fe, which are common contaminants present in filter raw media or arising from EDXRF hardware. The annual verification performed using five EDXRF analyzers demonstrated that the MDL estimated following the USEPA procedure was stable over time and analyzers for all elements except K, which yielded a higher MDL. Implications: Lightly loaded reference materials (RM) were developed for Energy Dispersive X-ray Fluorescence (EDXRF) measurements of elemental concentrations in filter-based particulate matter samples using a novel aerosol generation chamber. These RM were then used to estimate method detection limits (MDL) following U.S. Environmental Protection Agency guidance. These new MDL estimates were compared to alternative estimates and, for most elements, are higher. Our work provides EDXRF users with MDL estimates for each element and an assessment of different MDL estimation approaches.

The concentrations of polycyclic aromatic hydrocarbons in fish: A systematic review

Perchlorate, an inorganic anion, has recently been recognized as an environmental contaminant by the US Environmental Protection Agency. Urine is the preferred matrix for assessment of human exposure to perchlorate. Although the measurement technique for perchlorate in urine was developed in 2005, the calibration and quality assurance aspects of the metrology infrastructure for perchlorate are still lacking in that there is no certified reference material (CRM) traceable to the International System of Units. To meet the quality assurance needs in biomonitoring measurements of perchlorate and the related anions that affect thyroid health, the National Institute of Standards and Technology (NIST), in collaboration with the Centers for Disease Control and Prevention (CDC), developed Standard Reference Material (SRM) 3668 Mercury, Perchlorate, and Iodide in Frozen Human Urine. SRM 3668 consists of perchlorate, nitrate, thiocyanate, iodine, and mercury in urine at two levels that represent the 50th and 95th percentiles, respectively, of the concentrations (with some adjustments) in the US population. It is the first CRM being certified for perchlorate. Measurements leading to the certification of perchlorate were made collaboratively at NIST and CDC using three methods based on liquid or ion chromatography tandem mass spectrometry. Potential sources of bias were analyzed, and results were compared for the three methods. Perchlorate in SRM 3668 Level I urine was certified to be 2.70 ± 0.21 μg L(-1), and for SRM 3668 Level II urine, the certified value is 13.47 ± 0.96 μg L(-1).

Froth treatment tailings (FTT) are a byproduct of bitumen extraction in Alberta’s oil sands and, while the smallest tailings stream by volume, they present disproportionate challenges for closure and reclamation. Produced during froth treatment, where diluent such as naphtha is added to separate bitumen from water and solids, FTT contain residual hydrocarbons and sulfide minerals like pyrite. These constituents can influence redox conditions, microbial activity, and hydrocarbon degradation processes, ultimately affecting long-term deposit behavior. Despite their importance, FTT remain understudied compared with other tailings types, especially in the context of terrestrial beach deposits targeted for reclamation.This study investigated the spatial and vertical distribution of hydrocarbons and microbial communities across a 1.4 km transect of a naphtha-based FTT beach deposit at Syncrude’s Mildred Lake Settling Basin. Samples were collected from six locations spanning the pond edge to a reclamation dyke, with depths ranging from 0.15 to 46 m. Chemical analysis revealed that petroleum hydrocarbon (PHC) and residual naphtha concentrations reflected deposition history, with higher concentrations found in deeper, older FTT near the dyke and at shallower depths adjacent to the pond. Naphtha concentrations were most strongly correlated with heavier PHC fractions (F2–F4), while toluene and ethylbenzene emerged as key indicators of microbial variation.Distinct microbial communities were observed in FTT relative to the underlying coarse tailings, with reduced diversity at depths greater than ~30 m. FTT were enriched in hydrocarbon degraders (e.g., Pseudomonas), sulfur-cycling taxa (Thiobacillus, Desulfovibrio, Desulfotomaculales), and methanogens (Methanosaeta). Community composition varied with depth, distance from the pond, and presence of FTT, with the strongest drivers being PHC concentrations and pyrite content. These findings suggest that residual hydrocarbons act both as substrates and stressors, shaping microbial ecology while interacting with geochemical processes such as sulfur reduction and oxidation as well as methanogenesis.Together, this work provides one of the first spatially resolved assessments of FTT deposits illustrating how residual diluent, hydrocarbons, and microbial processes interact to influence subsurface conditions. Accurate characterization of FTT is essential for predicting long-term behavior, guiding the design of closure landforms, and informing reclamation monitoring programs.

The maximum growth rate of Nitzschia closterium at various concentrations of petroleum hydrocarbon was studied. The influence of petroleum hydrocarbon on cell size as a function of concentration was discussed. The relationship between maximum growth rate of Nitzschia closterium and cell median equivalent spherical diameter (MESD) was also carefully studied. The experimental results showed that the growth rate of Nitzschia closterium was generally suppressed by petroleum hydrocarbon, which had greater effects at both low and high concentrations than at intermediate concentrations. No significant changes in cell size distribution were observed during the growth period of Nitzschia closterium. The Gaussian function could give a clear description of the cell size distribution of Nitzschia closterium, and the MESD value ranged from 2.71 to 6.82 μm. The MESD decreased when the cell was exposed to petroleum hydrocarbon, and the reduction of cell MESD was much more significant at both relatively high and low hydrocarbon concentrations. The presence of petroleum hydrocarbon changed the relationship between μmax and MESD from an allometric function to a U-shaped curve. When the MESD was below 5.07 μm, μmax decreased along with increased MESD, whereas when MESD was above 5.07 μm, μmax increased along with MESD, which deviated from the allometric model.

In this study, the effect of process parameters (incubation period, temperature, initial pH-value, concentration of PAHs in the medium, and bacterial inoculum size) on the biodegradation of PAHs using Mycobacteria confluentis was studied using One-Factor-At-a-Time (OFAT) method. From the results of the study, it was observed that the studied parameters had significant effects on the degradation process. The capability of Mycobacteria confluentis on the degradation of PAHs was found to be maximum when the initial pH of the PAH was 7, temperature 40 °, PAH concentration of 50 μL, bacterial concentration of 7.5 mL, and incubated for 3 to 5 days. This condition gave a PAH degradation percentage of 40 to 50 %, showing a similarity to most previous studies where the maximum percentage of degradation has been around 40 to 50 %. This study, therefore, concludes that Mycobacteria confluentis is a good PAHs degrader which can be of significant important in the management of oil polluted fields and environments.

Hydrocarbon distributions in sediments of the open area of the Arabian Gulf following the 1991 Gulf War oil spill

Physico-chemical methods for removing low concentration dispersed Total Petroleum Hydrocarbons (TPH) from water are not cost-effective. The aim of this study was to remove TPH from water by combined cultivation of Azolla and bacteria. Concentrations of petroleum hydrocarbon in culture medium were 100,500 and 1000 mgL-1. Study was conducted over 14 days in three modes by cultivation of Azolla, bacteria and combined Azolla-bacteria culture. Concentration of Petroleum hydrocarbon (TPH) in the water samples was measured using gas chromatography. For cultivation of Azolla, the TPH removal from water after 14 days of contact was 76%, 70%, and 62% for initial TPH concentrations of 100, 500, and 1000 mgL-1 respectively. For bacterial cultivation, for an initial TPH concentration of 1000 mgL-1, Pseudomonas aeruginosa exhibited the lowest removal efficiency of 35%, while Alcaligenes faecalis showed the highest removal efficiency of 60%. In the combined cultivation of Azolla and bacteria, for an initial TPH concentration of 1000 mgL-1, Pseudomonas aeruginosa and Azolla exhibited the lowest removal efficiency of 80%, while Alcaligenes faecalis and Azolla showed the highest removal efficiency of 100%. Combined cultivation Azolla and bacteria was effective to improve removal of petroleum hydrocarbon from water.

The concentration of total polycyclic aromatic hydrocarbons (∑PAHs) and the 16 US EPA priority individual PAH compounds were analyzed in surface sediments from the Mai Po Inner Deep Bay, Ramsar Site of Hong Kong from December 2001 to Jun 2005, to investigate the spatial variability of anthropogenic pollutants. ∑PAHs concentrations ranged from 36.5 to 256.3 ng g(-1) dry weight with an average of 148.9 ng g(-1), comparable to other urbanized areas of the world, and there was little difference among different sampling times from December 2001 to June 2005. Based on comparison to the results from earlier study, it appears that a decrease of total PAHs concentration has occurred since 1992. Meanwhile, the concentrations of ∑PAHs were positive correlated with total organic carbon contents except sites F and G, suggesting the characteristics of the sediment influences the distribution and concentration of PAHs. There was relatively a good relationship among the individual PAHs and the compounds of fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]pyrene and indeno[cd]pyrene yielded a good correlation (r(2) > 0.5) with total PAHs. Principal component analysis and specific PAHs compound ratios (Phe/Ant vs. Flt/Pyr) indicate the pyrogenic origins, especially traffic exhausts, are the dominant sources of PAHs in the Mai Po Inner Deep Bay Nature Reserve.