Behavior of PAHs during cold storage of historically contaminated soil samples

Comprehensive methodology for semi-volatile organic compound determination in ambient air with emphasis on polycyclic aromatic hydrocarbons analysis by GC-MS/MS

Polycyclic aromatic hydrocarbons are air pollutants that affect the human health and the environment, and their accurate determination in outdoor and indoor environments is important. This study presents a methodology for sampling and analysis of semi-volatile compounds in ambient air with emphasis on the polycyclic aromatic hydrocarbons, collected with low-volume pumps (4.8 m3) in unconditioned solid phase extraction cartridges (Isolute ENV+). Sampling in SPE cartridges with low-volume pumps allows the collection of both gas and particulate phase compounds in indoor as well as outdoor environments, and reduces the number of extraction steps required as well as the solvent volume used for extraction. Analysis of the 16 US-EPA priority PAHs after extraction was conducted by GC-MS/MS with recoveries of the PAHs 40-118 %. No breakthrough was detected during sampling. Moreover, the methodology includes storage test to assess the conservation of PAHs in the SPE cartridges in heat-sealable Kapac bags; simulating transport from sampling sites to laboratory, and storage under room, cold and frozen conditions at different time-intervals, up to 3 months after sampling. The results showed that concentration levels remained constant across various storage time intervals and temperatures, with naphthalene and acenaphthylene being the only exceptions, showing high blank levels for the first and losses at room temperature for the later. The method quantification limits, including sampling, storage and GC-MS/MS analysis ranged from 2000 pg m-3 for naphthalene and 300 pg m-3 for phenanthrene to less than 20.0 pg m-3 for higher molecular and less volatile PAHs, such as benzo[a]pyrene (LOQ = 8.0 pg m-3). The feasibility of the method was tested by sampling indoors under urban background air conditions, showing individual PAH concentrations 4 to 10 times higher than their method quantification limits.

First report on BTEX leaching from waterpipe tobacco wastes (WTWs) into aquatic environment

Waterpipe tobacco wastes (WTWs) may contain considerable levels of hazardous contaminants such as BTEX (benzene, toluene, ethylbenzene, o-xylene, and m/p-xylene). However, no research has been carried out on BTEX levels in WTWs and the release of these pollutants into the water environment. This research examined the levels of BTEX in WTWs of flavored/local tobacco and also the release rate of these toxins into three kinds of water, including seawater (SW), tap water (TW), and distilled water (DW) with different leaching times (15, 30 min, 1.2, 4, 8 h, and 1, 2, and 4 days). The mean contents of BTEX in WTW samples of Al-Mahmoud, Al-Fakher, Mazaya, Al-Ayan brands, and local tobacco samples were 17.0 ± 4.14, 19.1 ± 4.65, 19.6 ± 4.19, 18.8 ± 4.14, and 3.16 ± 0.63 μg/kg, respectively. The mean BTEX levels in flavored tobacco samples were considerably greater than that of local tobacco (p < 0.05). The WTWs leaching experiments showed that the levels of BTEX ranged from 5.26 to 6.12, 5.02-5.60, and 3.83-5.46 μg/L in DW, TW, and SW, respectively. All target compounds were found for all exposure times in DW, TW, and SW samples. After adding sodium azide as an antibacterial agent to water samples (simulating biodegradation processes), higher levels of BTEX compounds were detected in SW. Further research is needed to address the potential environmental hazards due to WTWs leaching into aquatic environments.

Polycyclic aromatic hydrocarbon (PAH) leachates from post-consumption waterpipe tobacco waste (PWTW) into aquatic environment- a primary study

Post-consumption waterpipe tobacco waste (PWTW) is an unrecognized type of hazardous waste that is produced and released in large quantities into the aquatic environment. It may contain high amounts of various pollutants including PAH, and to date, there has been no research on the potential for contamination by PAH from PWTW leaching into aquatic environments. In this study, the concentrations of PAH via PWTW of fruit-flavored and traditional tobacco leachate into three water types, including distilled water (DW), tap water (TW) and sea water (SW) at different contact times were evaluated. There were significantly higher concentration levels of ƩPAH in waters with leachates from fruit-flavored PWTW than traditional tobacco (P-value<0.05). The concentration levels of ƩPAH in DW, TW and SW at a total contact time of two months ranged from 0.13 to 3.51, 0.12 to 3.63 and 0.11-3.64 μg/L, respectively. Lower molecular weight PAH such as naphthalene (Naph), acenaphthylene (Acen) and fluorine (Flu) were detected in leachates immediately after a short contact time of 15 min. Higher molecular weight PAH including benzo [a]anthracene (BaA), benzo [b]fluoranthene (BbF), benzo [k]fluoranthene (BkF), chrysene (Chr), and benzo [a]pyrene (BaP) were detected after one month contact time, while indeno [1,2,3-cd] pyrene (Indp), benzo [ghi]perylene (BghiP) and dibenz [a,h]anthracene (DahA) were only observed at the contact time measurement of two months. By adding sodium azide as an antimicrobial agent and chemical preservative to SW samples, higher concentrations of PAH including IP, DahA and BghiP were observed. The concentration levels of PAH in water samples after two months contact time were higher than water quality standards provided by the World Health Organization (WHO) and other international organizations.

Polycyclic aromatic hydrocarbons (PAHs) leachates from cigarette butts into water

Cigarette butts (CBs) are the most common littered items in the environment and may contain high amounts of polycyclic aromatic hydrocarbons (PAHs) from incomplete tobacco leave burning. The potential relevance of PAHs stemming from CBs for aquatic systems remain unclear since to date there is no systematic study on PAHs leaching from CBs. Therefore, in this study the leaching concentrations of 16 EPA-PAHs (except benzo(ghi)perylene) in 3 different types of water were measured. The concentrations of ΣPAHs leachates from 4 h to 21 days ranged from 3.9 to 5.7, 3.3-5.5, and 3.0-5.0 μg L^-1 for deionized, tap, and river waters, respectively. For all contact times, there were no substantial differences of the leachate concentrations of PAHs among different water types. Lighter PAHs had the highest concentrations among the detected PAHs and they were detected in the leachates already after 4 h. Concentrations of indeno(1,2,3-cd)pyrene, and dibenz(a,h)anthracene were below the limit of detection in all water samples at different contact times. At all contact times naphthalene and fluorene had the highest concentrations among the studied PAHs. Tap and river water samples with addition of sodium azide as chemical preservative contained significantly higher concentration of ΣPAHs. Our leaching data showed that leached concentrations of PAHs exceeded the Water Framework Directive (WFD) standards and considering the number of CBs annually littered this may pose a risk to aquatic organisms and potentially also humans.

Atmospheric carbonation reduces bioaccessibility of PAHs in industrially contaminated soil

Sorptive Bioaccessibility Extraction (SBE) was used to monitor changes in accessibility of polycyclic aromatic hydrocarbons (PAHs) during storage of historically contaminated alkaline soil (Σ US EPA 16 + 2 further PAHs: 2452 ± 69 mg kg^-1, n = 3). While total concentrations of PAHs were rather stable during storage for 561 days at 4 °C, PAH accessibility declined by 95% due to atmospheric carbonation. The formation of carbonates was evidenced by an increase of inorganic soil carbon and by carbonate coatings on black soil particles (SEM-EDX) that could be dissolved by providing neutral to acidic soil conditions. Subjecting soil (252 days of storage) to biodegradation at pH 7 resulted in a degraded fraction of PAHs equivalent to the accessible PAH fraction of soil as received (PAHs with log K_ow <5). The present study addresses important interactions and relationships between carbonation of soil, aging of PAHs in soil and related changes in PAH accessibility. A main finding was the reversibility of this retention mechanism, a changing environment (e.g. reduction of pH below 8) can result in a rise of accessible PAHs and consequently in an increase of exposure and associated risk.

A Critical Review about the Health Risk Assessment of PAHs and Their Metabolites in Foods

Polycyclic aromatic hydrocarbons (PAHs) are a family of toxicants that are ubiquitous in the environment. These contaminants generate considerable interest, because some of them are highly carcinogenic in laboratory animals and have been implicated in breast, lung, and colon cancers in humans. Dietary intake of PAHs constitutes a major source of exposure in humans. Factors affecting the accumulation of PAHs in the diet, their absorption following ingestion, and strategies to assess risk from exposure to these hydrocarbons following ingestion have received very little attention. This review, therefore, focuses on concentrations of PAHs in widely consumed dietary ingredients along with gastrointestinal absorption rates in humans. Metabolism and bioavailability of PAHs in animal models and the processes, which influence the disposition of these chemicals, are discussed. Finally, based on intake, disposition, and tumorigenesis data, the exposure risk to PAHs from diet is presented. This information is expected to provide a framework for refinements in risk assessment of PAHs.

Accumulation and risks of polycyclic aromatic hydrocarbons and trace metals in tropical urban soils

The study deals with the combined contribution of polycyclic aromatic hydrocarbons (PAHs) and metals to health risk in Delhi soils. Surface soils (0-5 cm) collected from three different land-use regions (industrial, flood-plain and a reference site) in Delhi, India over a period of 1 year were characterized with respect to 16 US Environmental Protection Agency priority PAHs and five trace metals (Zn, Fe, Ni, Cr and Cd). Mean annual ∑16PAH concentrations at the industrial and flood-plain sites (10,893.2 ± 2826.4 and 3075.4 ± 948.7 μg/kg, respectively) were ~15 and ~4 times, respectively, higher than reference levels. Significant spatial and seasonal variations were observed for PAHs. Toxicity potentials of industrial and flood-plain soils were ~88 and ~8 times higher than reference levels. Trace metal concentrations in soils also showed marked dependencies on nearness to sources and seasonal effects. Correlation analysis, PAH diagnostic ratios and principal component analysis (PCA) led to the identification of sources such as coal and wood combustion, vehicular and industrial emissions, and atmospheric transport. Metal enrichment in soil and the degree of soil contamination were investigated using enrichment factors and index of geoaccumulation, respectively. Health risk assessment (incremental lifetime cancer risk and hazard index) showed that floodplain soils have potential high risk due to PAHs while industrial soils have potential risks due to both PAHs and Cr.

Composition and Integrity of PAHs, Nitro-PAHs, Hopanes and Steranes In Diesel Exhaust Particulate Matter

Diesel exhaust particulate matter contains many semivolatile organic compounds (SVOCs) of environmental and health significance. This study investigates the composition, emission rates, and integrity of 25 SVOCs, including polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and diesel biomarkers hopanes and steranes. Diesel engine particulate matter (PM), generated using an engine test bench, three engine conditions, and ultra-low sulfur diesel (ULSD), was collected on borosilicate glass fiber filters. Under high engine load, the PM emission rate was 0.102 g/kWh, and emission rate of ΣPAHs (10 compounds), ΣNPAHs (6 compounds), Σhopanes (2 compounds), and Σsteranes (2 compounds) were 2.52, 0.351, 0.02 ~ 2 and 1μg/kWh, respectively. Storage losses were evaluated for three cases: conditioning filters in clean air at 25 °C and 33% relative humidity (RH) for 24 h; storing filter samples (without extraction) wrapped in aluminum foil at 4 °C for up to one month; and storing filter extracts in glass vials capped with Teflon crimp seals at 4 °C for up to six months. After conditioning filters for 24 h, 30% of the more volatile PAHs were lost, but lower volatility NPAHs, hopanes and steranes showed negligible changes. Storing wrapped filters and extracts at 4 °C for up to one month did not lead to significant losses, but storing extracts for five months led to significant losses of PAHs and NPAHs; hopanes and steranes demonstrated greater integrity. These results suggest that even relatively brief filter conditioning periods, needed for gravimetric measurements of PM mass, and extended storage of filter extracts can lead to underestimates of SVOC concentrations. Thus, SVOC sampling and analysis protocols should utilize stringent criteria and performance checks to identify and limit possible biases occurring during filter and extract processing.

Toxicity of waste gasification bottom ash leachate

Toxicity of waste gasification bottom ash leachate from landfill lysimeters (112 m(3)) was studied over three years. The leachate of grate incineration bottom ash from a parallel setup was used as reference material. Three aquatic organisms (bioluminescent bacteria, green algae and water flea) were used to study acute toxicity. In addition, an ethoxyresorufin-O-deethylase (EROD) assay was performed with mouse hepatoma cells to indicate the presence of organic contaminants. Concentrations of 14 elements and 15 PAH compounds were determined to characterise leachate. Gasification ash leachate had a high pH (9.2-12.4) and assays with and without pH adjustment to neutral were used. Gasification ash leachate was acutely toxic (EC(50) 0.09-62 vol-%) in all assays except in the algae assay with pH adjustment. The gasification ash toxicity lasted the entire study period and was at maximum after two years of disposal both in water flea (EC(50) 0.09 vol-%) and in algae assays (EC(50) 7.5 vol-%). The grate ash leachate showed decreasing toxicity during the first two years of disposal in water flea and algae assays, which then tapered off. Both in the grate ash and in the gasification ash leachates EROD-activity increased during the first two years of disposal and then tapered off, the highest inductions were observed with the gasification ash leachate. The higher toxicity of the gasification ash leachate was probably related to direct and indirect effects of high pH and to lower levels of TOC and DOC compared to the grate ash leachate. The grate ash leachate toxicity was similar to that previously reported in literature, therefore, confirming that used setup was both comparable and reliable.

Pyrosequence analysis of bacterial communities in aerobic bioreactors treating polycyclic aromatic hydrocarbon-contaminated soil

Two aerobic, lab-scale, slurry-phase bioreactors were used to examine the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil and the associated bacterial communities. The two bioreactors were operated under semi-continuous (draw-and-fill) conditions at a residence time of 35 days, but one was fed weekly and the other monthly. Most of the quantified PAHs, including high-molecular-weight compounds, were removed to a greater extent in the weekly-fed bioreactor, which achieved total PAH removal of 76%. Molecular analyses, including pyrosequencing of 16S rRNA genes, revealed significant shifts in the soil bacterial communities after introduction to the bioreactors and differences in the abundance and types of bacteria in each of the bioreactors. The weekly-fed bioreactor displayed a more stable bacterial community with gradual changes over time, whereas the monthly-fed bioreactor community was less consistent and may have been more strongly influenced by the influx of untreated soil during feeding. Phylogenetic groups containing known PAH-degrading bacteria previously identified through stable-isotope probing of the untreated soil were differentially affected by bioreactor conditions. Sequences from members of the Acidovorax and Sphingomonas genera, as well as the uncultivated "Pyrene Group 2" were abundant in the bioreactors. However, the relative abundances of sequences from the Pseudomonas, Sphingobium, and Pseudoxanthomonas genera, as well as from a group of unclassified anthracene degraders, were much lower in the bioreactors compared to the untreated soil.

Comparative studies on lignin and polycyclic aromatic hydrocarbons degradation by basidiomycetes fungi

A total of 130 wild basidiomycetes fungi were collected and identified. The polycyclic aromatic hydrocarbons (PAHs) degradation by the potential Phellinus sp., Polyporus sulphureus (in liquid state fermentation (LSF), solid state fermentation (SSF), in soil) and lignin biodegradation were compared with those of a bacterial isolate and their corresponding cocultures. The PAHs degradation was higher in LSF and the efficiency of the organisms declined in SSF and in soil treatment. Phellinus sp. showed better degradation in SSF and in soil. Bacillus pumilus showed higher degradation in LSF. B. pumilus was seen to have lower lignin degradation than the fungal cultures and the cocultures could not enhance the degradation. Phellinus sp. which had higher PAHs and lignin degradation showed higher biosurfactant production than other organism. Manganese peroxidase (MnP) was the predominant enzyme in Phellinus sp. while lignin peroxidase (Lip) was predominant in P. sulphureus.

Increasing polybrominated diphenyl ether (PBDE) contamination in sediment cores from the inner Clyde Estuary, UK

The concentrations of 16 polybrominated diphenyl ether (PBDE) congeners in six short sediment cores from the Clyde Estuary were determined by gas-chromatography mass-spectrometry. Total PBDE concentrations ranged from 1 to 2,645 mug/kg and the average concentration was 287 mug/kg. BDE-209 was the main congener and varied from 1 to 2,337 mug/kg. Elevated total PBDE concentrations were observed close to the sediment surface in the uppermost 10 cm of four of the six sediment cores. Comparison of the down core PBDE profiles revealed that the increase was driven by the accumulation of deca-BDE. Although the deca-BDE mix was dominant, the presence of lower molecular weight congeners BDE-47, BDE-99, BDE-183 and BDE-153 at most sediment intervals suggested additional sources of penta-BDE and octa-BDE pollution. Changing PBDE source input was the major factor in influencing the proportion of nona-brominated congeners, although other explanations such as post burial photo-debromination of BDE-209 cannot be entirely discounted. A clear cascading to lower hepta-, hexa-, and penta-homologues was not found. The increase in total PBDE concentrations and particularly the deca-BDE may possibly be ascribed to the use and subsequent disposal of electrical appliances such as televisions and computers. In the Clyde sediments, the proportion of nona-brominated congeners was higher than that reported for commercial mixtures. This might be due to changing sources of PBDEs or post burial photo-debromination of BDE-209.

Bioavailability of polycyclic aromatic hydrocarbons (PAHs) from soil and hay matrices in lactating goats

This experiment was aimed at determining the bioavailability of three polycyclic aromatic hydrocarbons (PAHs) in goats: phenanthrene, pyrene, and benzo[a]pyrene. A Latin square design procedure was carried out involving three alpine lactating goats and three PAH-contaminated matrices (soil, hay, and oil as a control). Milk and urine samples were collected to assess PAH and hydroxy-PAH excretion kinetics and to compare the carry-over rates for the different matrices. PAHs were found to be excreted mainly in urine; metabolite concentrations were about 20 times higher in urine than in milk. 1-Hydroxypyrene was the major metabolite in both body fluids (8000 ng/mL urine and 450 ng/mL milk); it may be considered as a valuable indicator of the ruminant exposure to PAHs. Apparent absorption of PAHs estimated by the metabolite excretion in urine and milk reached 34% for pyrene from soil, and the bioavailability of soil-bound PAHs was found to be similar to the bioavailability of PAHs from the other matrices.

Mutagenic potency in Salmonella typhimurium of organic extracts of soil samples originating from urban, suburban, agricultural, forest and natural areas

The purpose of the present work was to assess the mutagenic potency of soil samples presumably not contaminated by industrial wastes and discharges. A set of 51 soil samples was collected from areas considered as not contaminated by a known industrial activity: 11 urban samples (collected in cities), 15 suburban samples (collected in villages), 7 agricultural samples, and 18 forest or natural samples. Each soil sample was collected at the surface (0-5cm deep), dried, sieved (2mm), homogenized before organic extraction (dichloromethane/acetone 1/1 (v/v), 37 degrees C, 4h, soil/solvent ratio 1/2, m/v), solvent exchange to DMSO and sterilizing filtration. The micro-method adaptation of the standard bacterial mutagenicity test on Salmonella typhimurium strain TA98 was performed with and without a metabolic activation system (rat-liver homogenate S9), and thus detected the effect of pro-mutagens and direct mutagens, respectively. The use of a pre-incubation method increased the sensitivity of the assay. The results obtained showed a wide range of effect levels, from no effect to clear mutagenicity. In particular, the extract of all 11 urban soil samples demonstrated mutagenic activity, while the extracts of 10 of the 15 suburban samples showed mutagenicity. On the other hand, the extract of only one of the 7 agricultural samples studied induced mutations, and none of the 18 natural or forest-soil samples investigated produced mutagenic extracts. These findings seem to indicate the crucial influence of the diffuse pollution originating from different human activities on the mutagenic potency of urban soil samples. These findings make it possible to classify the soils according to their mutagenic potency. No clear correlation was found between the mutagenicity detected in soil extracts and the measured polycyclic aromatic hydrocarbon (PAH) content of the soils investigated.

The effect of ryegrass (Lolium perenne) on decrease of PAH content in long term contaminated soil

The biodegradation of polycyclic aromatic hydrocarbons in microecosystems containing long-term contaminated soil was investigated. Soil was contaminated by different chemicals, including PAHs since World War II. Aging of the soil was expected to act as a principal factor limiting biodegradation. Half of the microecosystems contained ryegrass (Lolium perenne) and long-term selected natural soil microflora originally present in contaminated soil. The others contained contaminated soil with natural microflora only. Half of the microecosystems in each parallel experiment was fertilised with N-P-K fertiliser. Cultivation was carried out at 12 and 18 months in a greenhouse with a natural photoperiod and the ability to degrade 15 chosen PAH was investigated. For analysis, the soil from each pot was divided into three horizontal layers for mutual comparison among layers and each layer was further divided into four equal samples. Soil extracts were analysed using HPLC. After a one-year-cultivation period the content of the monitored PAHs declined to 50%. Mostly, there were no significant differences between the microecosystems. Best degraded were fluoranthene and pyrene, which were the major contaminants present in original soil. Also, other compounds were successfully degraded, even benzo[a]pyrene and benzo[ghi]perylene. Dibenz[a,h]anthracene and indeno[1,2,3-cd]pyrene were the only PAHs, examined that showed no significant degradation. Although some differences between the soil layers were detected, no conclusive trends could be found. However, significantly lower concentrations of PAHs were determined mostly in the bottom layer of the analysed profiles. In vegetated microecosystems the decline of PAHs concentrations was more remarkable after 18 months cultivation.

Fungal inoculum properties: extracellular enzyme expression and pentachlorophenol removal in highly contaminated field soils

This study was conducted to improve the pentachlorophenol (PCP) bioremediation ability of white-rot fungi in highly contaminated field soils by manipulating bioaugmentation variables. These were the dry weight percentage of fungal inoculum addition (31-175 g kg(-1)), PCP concentration (100-2137 mg kg(-1) PCP), fungal inoculum formulation, and time (1-7 wk). Five fungal isolates were used: the New Zealand isolates Trametes versicolor (L.: Fr.) HR131 and Trametes sp. HR577; the North American isolates Phanerochaete chrysosporium Burds. (two isolates) and Phanerochaete sordida (Karst.) Erikss. & Ryv. Pentachlorophenol removal, manganese peroxidase, and laccase activity, and the formation of chloroanisoles in the contaminated field soils were measured. The majority of PCP removed by the Trametes isolates was in the first week after bioaugmentation. The maximum PCP removal by the fungi varied from 50 to 65% from a 1065 mg kg(-1) PCP contaminated field soil. Pentachlorophenol was preferentially converted to pentachloroanisole (PCA) by the Phanerochaete isolates (>60%), while 2 to 9% of the PCP removed by two Trametes isolates was converted to PCA. A pH increase was measured following bioaugmentation that was dependent on PCP concentration, fungal inoculum addition, and formulation. This, together with rapid initial PCP removal, possibly changed the bioavailability of the remaining PCP to the fungi and significantly decreased the sequestering of PCP in the contaminated field soils. The research supports the conclusion that New Zealand Trametes spp. can rapidly remove PCP in contaminated field soils. Bioavailability and extractability of PCP in the contaminated field soil may significantly increase after bioaugmentation.

Influence of laboratory storage on the organic contaminant content and water-extractable ecotoxicological potential of soil samples

At present there is a high level of uncertainty about whether or not soil samples, which are required to be toxicologically characterized, could be preserved without affecting their toxicological characteristics. In the existing DIN/ISO standards for soil investigations, there is no documentation on the storage of soil samples after collection for (eco-)toxicological investigations. Furthermore, procedures for receiving justifiable and verifiable results from soil samples are quite vague. Therefore, the stability and changes in the biological effects of different soil contaminants were investigated by varying the storage conditions and the storage times of the soil. The limitations of storing soils could therefore be subsequently outlined. Recommendations for the optimization of storage conditions for back-up soil samples were made. These recommendations have the capability of finding entrance into DIN/ISO standards.

Polycyclic aromatic hydrocarbons (PAHs) concentrations and related carcinogenic potencies in soil at a semi-arid region of India

A study of polycyclic aromatic hydrocarbons in surface soil was conducted at selected locations in Agra (semi-arid region of India) for a span of one year in order to ascertain the contamination levels. The concentrations of PAH were measured at four locations in the city of Agra, which covers industrial, residential, roadside and agricultural areas. The samples were extracted with hexane by ultrasonic agitation. The extracts were then fractioned on a silica-gel column and the aromatic fraction was subjected to HPLC. The average concentration of total PAH in all samples was 12.1 microg g(-1) and the range was from 3.1 microg g(-1) to 28.5 microg g(-1). The maximum concentrations of PAHs were found to be in winter season. The concentration of PAH decreased in the order chrysene > benzo(b)fluoranthene > fluoranthene. Factor analysis suggests that the mixed signature of all the sources are intermediate between vehicular and combustion activities.

Freezing To Preserve Groundwater Samples and Improve Headspace Quantification Limits of Water-Soluble Organic Contaminants for Carbon Isotope Analysis

Few systematic investigations have addressed the use of freezing for applications in analytical chemistry. Here, we tested its potential to preserve groundwater samples and to improve headspace quantification limits for compound-specific isotope analysis. Analysis of compound concentrations, as well as stable carbon isotope ratios, confirmed that trichloroethene was preserved in frozen suspensions of nanoscale zerovalent iron. In contrast, storage at 7 degrees C was ineffective, and complete degradation of TCE occurred in 4 weeks. Hence, freezing may stop even abiotic chemical reactions that would not be prevented by cooling or traditional preservation agents. In the absence of iron, we found that headspace concentrations of 14 organic contaminants were considerably higher over frozen solutions than at 25 degrees C, likely reflecting a freezing-out effect governed by Raoult's law. The observed enhancement depended on the salinity of the samples and was strongest for water-soluble, volatile compounds (values in brackets indicate the minimum observed effect out of six replicates): tert-butyl alcohol (TBA, 35-fold), methyl tert-butyl ether (MTBE, 14-fold), 1,2-dichloroethane (10-fold), or benzene (7-fold). In contrast, little enhancement was observed for less water-soluble compounds, such as tetrachloroethene. Although standard deviations of the measurements were too high for the method to be used for quantitative analysis of total compound concentrations, since we found that freezing introduces no measurable carbon isotope effect for TBA, MTBE, 1,2-dichloroethane, and benzene, the method is an effective way of increasing the sensitivity of compound-specific isotope analysis, particularly of water-soluble organic contaminants.

Accumulation of weathered polycyclic aromatic hydrocarbons (PAHs) by plant and earthworm species

Experiments were conducted to assess the bioavailability of polyclycic aromatic hydrocarbons (PAHs) in soil from a Manufactured Gas Plant site. Three plant species were cultivated for four consecutive growing cycles (28 days each) in soil contaminated with 36.3 microg/g total PAH. During the first growth period, Cucurbita pepo ssp. pepo (zucchini) tissues contained significantly greater quantities of PAHs than did Cucumis sativus (cucumber) and Cucurbita pepo ssp. ovifera (squash). During the first growth cycle, zucchini plants accumulated up to 5.47 times more total PAH than did the other plants, including up to three orders of magnitude greater levels of the six ring PAHs. Over growth cycles 2-4, PAH accumulation by zucchini decreased by 85%, whereas the uptake of the contaminants by cucumber and squash remained relatively constant. Over all four growth cycles, the removal of PAHs by zucchini was still twice that of the other species. Two earthworm species accumulated significantly different amounts of PAH from the soil; Eisenia foetida and Lumbricus terrestris contained 0.204 and 0.084 microg/g total PAH, respectively, but neither species accumulated measurable quantities 5 or 6 ring PAHs. Lastly, in abiotic desorption experiments with an aqueous phase of synthetically prepared organic acid solutions, the release of 3 and 4 ring PAHs from soil was unaffected by the treatments but the desorption of 5-6 ring constituents was increased by up to two orders of magnitude. The data show that not only is the accumulation of weathered PAHs species-specific but also that the bioavailability of individual PAH constituents is highly variable.

Biodegradation of phenanthrene, spatial distribution of bacterial populations and dioxygenase expression in the mycorrhizosphere of Lolium perenne inoculated with Glomus mosseae

Interactions between the plant and its microbial communities in the rhizosphere control microbial polycyclic aromatic hydrocarbons (PAH) biodegradation processes. Arbuscular mycorrhizal (AM) fungi can influence plant survival and PAH degradation in polluted soil. This work was aimed at studying the contribution of the mycorrhizosphere to PAH biodegradation in the presence of ryegrass (Lolium perenne L., cv. Barclay) inoculated with Glomus mosseae (BEG 69) by taking into account the structure and activity of bacterial communities, PAH degrading culturable bacteria as a function of the distance from roots. Ryegrass was grown in compartmentalized systems designed to harvest successive sections of rhizosphere in lateral compartments polluted or not with phenanthrene (PHE). Colonization of roots by G. mosseae (BEG 69) modified the structure and density of bacterial populations in the mycorrhizosphere, compared to the rhizosphere of non-mycorrhizal plants. G. mosseae increased the density of culturable heterotrophic and PAH degrading bacteria beyond the immediate rhizosphere in the presence of PHE, and increased the density of PAH degraders in the absence of the pollutant. Biodegradation was not significantly increased in the mycorrhizosphere, compared to control non-mycorrhizal plants, where PHE biodegradation already reached 92% after 6 weeks. However, dioxygenase transcriptional activity was found to be higher in the immediate mycorrhizosphere in the presence of G. mosseae (BEG 69).

Comparison of selected non-exhaustive extraction techniques to assess PAH availability in dissimilar soils

Recently, it has become apparent that the use of total contaminant concentrations as a measure of potential contaminant exposure to plants or soil organisms is inappropriate and that bioavailability of contaminants is a better measure of potential exposure. In light of this, non-exhaustive extraction techniques are being investigated to assess their appropriateness in determining bioavailability. In this study, phenanthrene extractability using hydroxypropyl-beta-cyclodextrin (HPCD) and desorption kinetics using butan-1-ol (BuOH) were determined in three dissimilar spiked soils. The soils were extracted after 1 d, 40 d and 80 d of soil-compound contact time. The amount of phenanthrene extracted by HPCD was compared to the rapidly desorbed fraction removed by BuOH. Further experiments using the same soils and extraction methods to assess the relative extractability of phenanthrene, pyrene and benzo(a)pyrene were conducted. Overall, the extraction methods used in this study had different extraction efficiencies. Results suggest that as compound hydrophobicity increased, BuOH became a more exhaustive extractant with respect to HPCD, especially for soils with high clay and organic matter content. These results are important as they highlight differences between two contrasting non-exhaustive extraction techniques both of which have been suggested to be appropriate in the assessment of bioavailability.

Influence of extraction parameters on the mutagenicity of soil samples

The aim of this study was to investigate the influence of four extraction parameters (type of solvent, temperature, duration of extraction, and soil mass/solvent volume ratio) on the mutagenicity of soil extracts. Four urban soil samples were submitted to the micro-method adaptation of the Ames test on Salmonella typhimurium according to the following sequence: identification of the most sensitive strain (TA98 or TA100), the best solvent(s), the optimum extraction temperature and extraction time, and finally the optimal soil/solvent ratio. Extraction was thus performed using eight different solvents (distilled water, dichloromethane, acetonitrile, acetone, cyclohexane, methanol, hexane, or ethanol), two temperatures (room temperature or 37 degrees C), two durations (4 or 24 h), and two soil mass/solvent volume ratios (1:2 or 1:10). The results show that strain TA98 was more sensitive than strain TA100, and the observed mutagenicity was expressed as number of TA98 revertants per mg of soil equivalent. No mutagenicity was induced by the distilled water extracts, whereas most of the organic solvent extracts induced a significant mutagenic response. A dichloromethane/acetone mixture appeared to be the best compromise for extraction of mutagens from the urban soils tested. Moreover, the present study showed that a higher mutagenic activity was generally obtained with a temperature of 37 degrees C (compared to room temperature), with an extraction time of 24 h (compared to 4 h), and with a soil mass/solvent volume ratio of 1:10 (compared to 1:2).