Determination of coal tar and creosote constituents in the aquatic environment

Neural network establishes co-occurrence links between transformation products of the contaminant and the soil microbiome

It remains challenging to establish reliable links between transformation products (TPs) of contaminants and corresponding microbes. This challenge arises due to the sophisticated experimental regime required for TP discovery and the compositional nature of 16S rRNA gene amplicon sequencing and mass spectrometry datasets, which can potentially confound statistical inference. In this study, we present a new strategy by combining the use of 2H-labeled Stable Isotope-Assisted Metabolomics (2H-SIAM) with a neural network-based algorithm (i.e., MMvec) to explore links between TPs of pyrene and the soil microbiome. The links established by this novel strategy were further validated using different approaches. Briefly, a metagenomic study provided indirect evidence for the established links, while the identification of pyrene degraders from soils, and a DNA-based stable isotope probing (DNA-SIP) study offered direct evidence. The comparison among different approaches, including Pearson's and Spearman's correlations, further confirmed the superior performance of our strategy. In conclusion, we summarize the unique features of the combined use of 2H-SIAM and MMvec. This study not only addresses the challenges in linking TPs to microbes but also introduces an innovative and effective approach for such investigations. Environmental Implication: Taxonomically diverse bacteria performing successive metabolic steps of the contaminant were firstly depicted in the environmental matrix.

Zebrafish CYP1A expression in transgenic Caenorhabditis elegans protects from exposures to benzo[a]pyrene and a complex polycyclic aromatic hydrocarbon mixture

Polycyclic aromatic hydrocarbons (PAHs) are environmental toxicants primarily produced during incomplete combustion; some are carcinogens. PAHs can be safely metabolized or, paradoxically, bioactivated via specific cytochrome P450 (CYP) enzymes to more reactive metabolites, some of which can damage DNA and proteins. Among the CYP isoforms implicated in PAH metabolism, CYP1A enzymes have been reported to both sensitize and protect from PAH toxicity. To clarify the role of CYP1A in PAH toxicity, we generated transgenic Caenorhabditis elegans that express CYP1A at a basal (but not inducible) level. Because this species does not normally express any CYP1 family enzyme, this approach permitted a test of the role of basally expressed CYP1A in PAH toxicity. We exposed C. elegans at different life stages to either the PAH benzo[a]pyrene (BaP) alone, or a real-world mixture dominated by PAHs extracted from the sediment of a highly contaminated site on the Elizabeth River (VA, USA). This site, the former Atlantic Wood Industries, was declared a Superfund site due to coal tar creosote contamination that caused very high levels (in the [mg/mL] range) of high molecular weight PAHs within the sediments. We demonstrate that CYP1A protects against BaP-induced growth delay, reproductive toxicity, and reduction of steady state ATP levels. Lack of sensitivity of a DNA repair (Nucleotide Excision Repair)-deficient strain suggested that CYP1A did not produce significant levels of DNA-reactive metabolites from BaP. The protective effects of CYP1A in Elizabeth River sediment extract (ERSE)-exposed nematodes were less pronounced than those seen in BaP-exposed nematodes; CYP1A expression protected against ERSE-induced reduction of steady-state ATP levels, but not other outcomes of exposure to sediment extracts. Overall, we find that in C. elegans, a basal level of CYP1A activity is protective against the examined PAH exposures.

Acute hazard of biocides for the aquatic environmental compartment from a life-cycle perspective

One of the aims of the European project LIFE-COMBASE is to build a computational tool to predict the acute toxicity for aquatic organisms of biocidal active substances and its environmental degradation products. A database was implemented compiling toxicity data for these substances in organisms of the freshwater/marine and sewage treatment plant compartments. The goal of this study is to analyze the compiled data to identify the possible hazard of these compounds for the aquatic compartments. Several official and scientific databases were consulted. Data from 196 biocidal substances and 206 environmental metabolites were collected for the taxonomic groups, including fish, invertebrates, algae and sewage treatment plant (STP) microorganisms. Substances were categorized for their toxicity in four groups, considering values of L(E)C₅₀, according to EU Regulation (EC) No 1272/2008. >50% of the parent were located in category 1 (L(E)C₅₀ ≤ 1 mg/L) for fish, invertebrates and algae, indicating a high toxicity for the freshwater/marine compartments. However >60% were not toxic for STP microorganisms. Metabolites were mainly less toxic than the parent compounds, but 22-36% presented the same toxicity and ~6% were more toxic. No toxicological information was found for ~50% of the metabolites for fish, invertebrates and algae, reaching the 96% for the microorganisms. In addition, information on toxicity to the STP microorganisms was only found for 40% of the parent compounds. The high percentage of toxic metabolites and the scarcity of data for these compounds indicate the need to further study their impact in the aquatic compartments.

A new way to discriminate polluted wood by vibrational spectroscopies

In this work, two sets of samples were considered: field samples collected from local waste wood and synthetic samples made by mixing clean wood (including oak, beech, poplar) with typical organic pollutants: creosote, polychlorinated byphenils (PCBs), pentachlorophenol (PCP), cypermethrin, dodecyl dimethyl ammonium chloride (DDAC). Vibrational spectroscopy techniques were tested to detect organic pollutants in wood items. Raman and infrared spectroscopies were showed as fast, non-destructive and non-invasive fingerprint techniques for detection of organic molecules. Associated with principal component analysis, we have shown the evidence of quick detection of and discrimination of polluted wood items by kinds and versus concentration.

In vitro mammalian mutagenicity of complex polycyclic aromatic hydrocarbon mixtures in contaminated soils

This study employed an in vitro version of the lacZ transgenic rodent mutation assay to assess the mutagenicity of nonpolar neutral and semipolar aromatic soil fractions from 10 PAH-contaminated sites, and evaluated the assumption of dose additivity that is routinely employed to calculate the risk posed by PAH mixtures. Significant mutagenic activity was detected in all nonpolar neutral fractions, and 8 of 10 semipolar aromatic fractions (nonpolar > semipolar). Mutagenic activity of synthetic PAH mixtures that mimic the PAH content of the soils (i.e., 5-PAH or 16-PAH mix) were greater than that of the PAH-containing soil fractions, with 5-PAH mix >16-PAH-mix. Predictions of mutagenic activity, calculated as the sum of the contributions from the mutagenic mixture components, were all within 2-fold of the observed activity of the nonpolar neutral fractions, with one exception. Observed differences in mutagenic activity are likely the result of dynamic metabolic processes, involving a complex interplay of AhR agonsim and saturation of metabolic machinery by competitive inhibition of mixture components. The presence of hitherto unidentified polar compounds present in PAH-contaminated soils may also contribute to overall hazard; however, these compounds are generally not included in current contaminated site risk assessment protocols.

Kinetics of extraction of coal-tar pitch components with supercritical carbon dioxide

The extraction of a coal-tar pitch with supercritical carbon dioxide was performed under optimal pressure, flow rate, and three different constant temperatures. The extraction kinetics was examined for each temperature and it was surprisingly found that the extraction rate of most components was governed by the first-order kinetics. It was assumed that this deviation from typical models of supercritical fluid extraction kinetics was caused by high pitch concentrations and low solubilities of the components.

Characterization and classification of complex PAH samples using GC-qMS and GC-TOFMS

The aim of this study was to compare the polycyclic aromatic hydrocarbon (PAH) contents in a number of complex samples, including soil samples from industrial sites, anti-skid sand, urban dust and ash samples from municipal solid waste incinerators. The samples were characterized by routine analysis of PAHs (gas chromatography-quadrupole mass spectrometry) and gas chromatography-time of flight mass spectrometry (GC-TOFMS). Classification of the samples by principal component analysis (PCA) according to their composition of PAHs revealed that samples associated with traffic and the municipal incinerator formed homogeneous clusters, while the PAH-contaminated soils clustered in separate groups. Using spectral data to resolve co-eluting chromatographic peaks, 962 peaks could be identified in the GC-TOFMS analysis of a pooled sample and 123-527 peaks in the individual samples. Many of the studied extracts included a unique set of chemicals, indicating that they had a much more diverse contamination profile than their PAH contents suggested. Compared to routine analysis, GC-TOFMS provided more detailed information about each sample and in this study a large number of alkylated PAHs were found to be associated with the corresponding unsubstituted PAHs. The possibility to filter peaks according to different criteria (e.g. to include only peaks that were detected in the analysis of another sample) was explored and used to identify unique as well as common compounds within samples. This procedure could prove to be valuable for obtaining relevant chemical data for use in conjunction with results from various biological test systems.

Matrix-immobilized organoclay for the sorption of polycyclic aromatic hydrocarbons and pentachlorophenol from groundwater

Sorbent materials consisting of organoclay immobilized onto the surface of a solid support were evaluated for use in pentachlorophenol (PCP) and polycyclic aromatic hydrocarbon (PAH) remediation of groundwater at a creosote-contaminated Superfund site. Cetylpyridinium-exchanged low pH montmorillonite clay (CP-LPHM) was bonded to either sand (CP-LPHM/sand) or granular activated carbon (GAC) (CP-LPHM/GAC) using the free acid form of carboxymethylcellulose as an adhesive. Effluent from an oil-water separator was eluted through equal bed volumes of composite (4 g 3:2 CP-LPHM/GAC or 13 g CP-LPHM/sand), affinity-extracted, and quantitatively analyzed by GC/MS. PCP, naphthalene, fluorene, phenanthrene, pyrene, and total PAHs were initially reduced by both CP-LPHM/GAC (> or =99%, 61%, 99%, > or =99%, 97%, and 94%, respectively) and CP-LPHM/sand (90%, 70%, 94%, 95%, 93%, and 86%, respectively). Complete breakthrough of naphthalene occurred after approximately 15 h of elution through 3:2 CP-LPHM/GAC and 22 h through CP-LPHM/sand. PCP showed complete breakthrough following 18 h of elution through 3:2 CP-LPHM/GAC and 26 h through CP-LPHM/sand. However, 50% breakthrough was not attained for higher molecular weight PAHs, as fluoranthene, pyrene, benzo[a]anthracene, and chrysene continued to be greatly reduced with both 3:2 CP-LPHM/GAC (98%, 95%, 94%, and 95%, respectively) and CP-LPHM/sand (75%, 73%, 76%, and 78%, respectively) after 48 h of continuous elution. Results confirm prior studies, indicating that these organoclay-containing composites have a high capacity for contaminants found in wood preserving waste. Further, results suggest that the inclusion of CP-LPHM may be useful as part of an effective strategy for groundwater remediation of high concentrations of PCP and PAHs, in particular high molecular weight and carcinogenic PAHs.

Potential for anaerobic conversion of xenobiotics

This review covers the latest research on the anaerobic biodegradation of aromatic xenobiotic compounds, with emphasis on surfactants, polycyclic aromatic hydrocarbons, phthalate esters, polychlorinated biphenyls, halogenated phenols, and pesticides. The versatility of anaerobic reactor systems regarding the treatment of xenobiotics is shown with the focus on the UASB reactor, but the applicability of other reactor designs for treatment of hazardous waste is also included. Bioaugmentation has proved to be a viable technique to enhance a specific activity in anaerobic reactors and recent research on reactor and in situ bioaugmentation is reported.

Porous organoclay composite for the sorption of polycyclic aromatic hydrocarbons and pentachlorophenol from groundwater

Complex mixtures of hazardous chemicals such as polycyclic aromatic hydrocarbons (PAHs) in contaminated soil and groundwater can have severe and long-lasting effects on health. The evidence that these contaminants can cause adverse health effects in animals and humans is rapidly expanding. The frequent and wide-spread occurrence of PAHs in groundwater makes appropriate intervention strategies for their remediation highly desirable. The core objective of this research was to assess the ability of a clay-based composite to sorb and remove toxic contaminants from groundwater at a wood-preserving chemical waste site. Treatment efficiencies were evaluated using either effluent from an oil-water separator (OWS) or a bioreactor (B2). The effluent water from these units was passed through fixed bed columns containing either an organoclay composite or granular activated carbon. The sorbent columns were placed in-line using existing sampling ports at the effluent of the OWS or B2. Individual one-liter samples of treated and untreated effluent were collected in Kimax bottles over the course of 78 h (total of 50 samples). Subsequently each sample was extracted by solid phase extraction methodology, and pentachlorophenol (PCP) and PAH concentrations were quantitated via GC/MS. Columns containing porous organoclay composite, i.e. sand-immobilized cetylpyridinium-exchanged low-pH montmorillonite clay (CP/LPHM), were shown to reduce the contaminant load from the OWS effluent stream by 97%. The concentrations of benzo[a]pyrene (BaP) and PCP were considerably reduced (i.e. >99%). An effluent stream from the bioreactor was also filtered through columns packed with composite or an equivalent amount of GAC. Although the composite reduced the majority of contaminants (including BaP and PCP), it was less effective in diminishing the levels of lower ring versus higher ring PAHs. Conversely, GAC was more effective in removing the lower ring PAHs, except for naphthalene and PCP. The effectiveness of sorption of PCP from the OWS effluent by the composite was confirmed using a PCP-sensitive adult hydra bioassay previously described in our laboratory. The findings of this initial study have delineated differences between CP/LPHM and GAC for groundwater remediation, and suggest that GAC (instead of sand) as the solid support for organoclay may be more effective for the treatment of contaminated groundwater under field conditions than GAC or CP/LPHM alone. Further work is ongoing to confirm this conclusion.

Determination of hydrocarbons in old creosote contaminated soil using headspace solid phase microextraction and GC-MS

Headspace solid phase microextraction (HS-SPME) has been used together with GC-MS to analyze organic substances directly in a soil, heavily contaminated with PAHs/creosote (approximately 300 mg/kg soil), from an old gaswork site in Stockholm, Sweden. The HS-SPME results, both qualitative and quantitative, were compared with traditional liquid extraction using ethyl acetate/hexane (20:80). It was shown that the concentrations determined with HS-SPME at 60 degrees C correlated well, for compounds containing up to two and three aromatic rings (naphthalenes, acenaphthene, acenaphthylene and fluorenes, while a lower concentration was obtained for phenanthrene, anthracene, fluoranthene and pyrene. The total concentrations for each compound determined with HS-SPME ranged from 2 to 25 microg/g soil. Quantification was done using standard addition of compounds directly to the soil samples. The bioavailable fraction of the compounds in the contaminated soil at 20 degrees C was analyzed using external calibration by spiking sterile uncontaminated sand (same texture and particle size as the contaminated soil but without a heavily sorbed organic fraction) with hydrocarbon standards in different concentrations. Storage of exposed fibers at 20 degrees C showed that analysis should be done within two days to make qualitative measurements and earlier (as soon as possible) for quantitative determinations.

Synergistic approaches based on nonchromatographic continuous separation techniques (solid-phase extraction and pervaporation) and chromatography couplings

Approaches based on continuous separation units coupled to either liquid or gas chromatography for improving the features of analytical methods are proposed. Examples of solid-phase separation-liquid chromatography for the determination of fat-soluble vitamins and their metabolites in clinical samples, and pervaporation-gas chromatography for the determination of volatile compounds in solid environmental samples are described. The clean-up and preconcentration effect achieved by the former coupling and the easy and effective solid-sample pretreatment in the latter clearly show their utility. The use of pervaporation as an advantageous alternative to headspace is demonstrated.