Release Of Polycyclic Aromatic Hydrocarbons Research Articles

Investigation of the release of PAHs from artificially contaminated sediments using cyclolipopeptidic biosurfactants

Polycyclic aromatic hydrocarbons (PAHs) can be preponderant in contaminated sediments and understanding how they are sorbed in the different mineral and organic fractions of the sediment is critical for effective removal strategies. For this purpose, a mixture of seven PAHs was studied at the sediment/water interface and sorption isotherms were obtained. The influence of various factors on the sorption behavior of PAHs was evaluated, such as the nature of minerals, pH, ionic strength and amount of organic matter. Afterwards, the release of PAHs from the sediment by surfactants was investigated. The effectiveness of sodium dodecyl sulfate (SDS) was compared to natural biosurfactants, of cyclolipopeptidic type (amphisin and viscosin-like mixture), produced by two Pseudomonas fluorescens strains. The desorption of PAHs (from naphthalene to pyrene), from the highly retentive kaolinite fraction, could be favored by adding SDS or amphisin, but viscosin-like biosurfactants were only effective for 2–3 ring PAHs desorption (naphthalene to phenanthrene). Moreover, while SDS favors the release of all the target PAHs from a model sediment containing organic matter, the two biosurfactants tested were only effective to desorb the lowest molecular weight PAHs (naphthalene to fluorene).

Ionic Liquid Assisted Dissolution of Dissolved Organic Matter and PAHs from Soil Below the Critical Micelle Concentration

Increased use and production of ionic liquids (ILs) may result in emissions into the environment. Particularly vulnerable are industrial areas and landfills where ILs are utilized and ultimately disposed of. This study investigates how IL contamination can affect soil properties and the sorption of pre-existing contaminants. The commonly used IL 1-methyl-3-octyl imidazolium chloride ([OMIM][Cl]) was added at various quantities to a landfill soil contaminated with polycyclic aromatic hydrocarbons (PAHs). Subsequently, the release of PAHs and dissolved organic matter (DOM) from this soil was thoroughly investigated. Two fractions of PAH release into the porewater were measured, the freely dissolved fraction (measured using a passive sampler) and the total PAH concentration (which includes the freely dissolved molecules as well as those associated with colloids, micelles and DOM). As expected the highest levels of total PAH porewater concentration occurred when the critical micelle concentration (CMC) of the IL was exceeded. However, as we report here for the first time, enhanced amounts of freely dissolved PAHs were released by sub-CMC concentrations of IL. Additionally, enhanced levels of DOM, due to dissolution of soil organic matter by IL, were also observed upon addition of sub-CMC IL concentrations. Based on this, enhanced release of pre-existing contaminants and DOM is suggested as a potential risk from IL emissions at trace concentrations well below the CMC. Potential mechanisms of this sub-CMC release are discussed.

Kinetic control of contaminant release from NAPLs – Experimental evidence

Mass transfer processes of pollutants from non-aqueous phase liquids (NAPL) may control groundwater pollution at abandoned industrial sites. We studied release kinetics of polycyclic aromatic hydrocarbons (PAHs) from fresh and aged tar phases using a dialysis tubing technique. Time for equilibration ranged from several days to more than three years. For fresh tar materials the release seems to be limited by retarded pore diffusion, while for two of three aged tars diffusion limited release influenced by dissolved organic matter (DOM) was assumed. The equilibration process was driven by solubilization thermodynamics expressed by Raoult's law. Yet, solubility enhancement was observed potentially due to the presence of organic mobile sorbents. The results show that the release of PAHs from tar phases is generally rate limited and partitioning according to Raoult's law is the driving mechanism of the exchanges process.

Health implications of PAH release from coated cast iron drinking water distribution systems in The Netherlands.

Background: Coal tar and bitumen have been historically used to coat the insides of cast iron drinking water mains. Polycyclic aromatic hydrocarbons (PAHs) may leach from these coatings into the drinking water and form a potential health risk for humans.Objective: We estimated the potential human cancer risk from PAHs in coated cast iron water mains.Method: In a Dutch nationwide study, we collected drinking water samples at 120 locations over a period of 17 days under various operational conditions, such as undisturbed operation, during flushing of pipes, and after a mains repair, and analyzed these samples for PAHs. We then estimated the health risk associated with an exposure scenario over a lifetime.Results: During flushing, PAH levels frequently exceeded drinking water quality standards; after flushing, these levels dropped rapidly. After the repair of cast iron water mains, PAH levels exceeded the drinking water standards for up to 40 days in some locations.Conclusions: The estimated margin of exposure for PAH exposure through drinking water was > 10,000 for all 120 measurement locations, which suggests that PAH exposure through drinking water is of low concern for consumer health. However, factors that differ among water systems, such as the use of chlorination for disinfection, may influence PAH levels in other locations.

Deposition fluxes and fate of polycyclic aromatic hydrocarbons in the Yangtze River estuarine‐inner shelf in the East China Sea

Surface sediments were obtained from a matrix of 76 sample sites in the inner shelf mud belts of the East China Sea (ECS) for a comprehensive study of the distribution, composition, deposition flux, and fate of polycyclic aromatic hydrocarbons (PAHs). The sampling sites covered an area of ~80,000 km2 extending ~1000 km from the mouth of the Yangtze River to the Min River in the inner shelf. The total deposition flux of the 16 USEPA priority PAHs (16 PAHs) of the Yangtze estuarine‐inner shelf was estimated to be 152 t/yr, accounting for ~38% of the total annual input of the 16 PAHs into the ECS. This indicates that the Yangtze estuarine‐inner shelf is one of the largest sinks of land‐based PAHs in the world. Principal component analysis indicated that the 16 PAHs in the northern Yangtze estuarine mud area were mostly phenanthrene while shifting to high‐molecular‐weight PAHs in the southern Min‐Zhe coastal mud area. The positive matrix factorization model revealed that the deposition flux of low‐molecular‐weight (LMW) PAHs decreased from north to south, most likely due to the mass transfer between the resuspended sediments triggered by the East Asian monsoon and the water columns, as the resuspended sediments are transported southward. This release of LMW PAHs from the sediments to the water columns could become an important secondary PAH source in ECS.

Impact assessment of anthropogenic activities on air quality, using lichen Remototrachyna awasthii as biomonitor

The study was carried out with an aim to assess the heavy metal (HM) and polycyclic aromatic hydrocarbons (PAHs) in the air of a biodiversity as well as tourist-rich area of Western Ghats by applying a most frequent growing lichen Remototrachyna awasthii (Hale and Patw.) Divakar and A. Crespo, as biomonitor. Thalli of R. awasthii were collected from eight sites of Mahabaleshwar area located in Western Ghats. Samples were prepared for HM and PAHs quantification by ICP-MS and HPLC, respectively. Total metal concentration (HM) ranged from 644 to 2,277.5 μg g−1 while PAHs concentration between 0.193 and 54.78 μg g−1. HM and PAHs concentrations were the highest at Bus Stand while control site (Lingmala Fall) exhibited the lowest concentration of HM as well as PAHs followed by samples from Wilson point (both these sites are having trekking route). It was also evident from this study that vehicular emission played a significant role in the release of HM and PAHs as pollutants in the environment. The effectiveness of R. awasthii as biomonitor could be further investigated by comparing this species with other biomonitors.

Elution of Polycyclic Aromatic Hydrocarbons in Soil Columns Using Low‐Molecular‐Weight Organic Acids

The impacts of low‐molecular‐weight organic acids (LMWOAs) on the release, distribution, and availability of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils were investigated using soil column experiments. Citric and malic acids, as representative LMWOAs, significantly promoted the release and enhanced the availability of phenanthrene and pyrene in three soil columns. Both the mobilized amounts and availabilities of test PAHs increased with increasing concentrations of citric or malic acid. When the concentration of citric acid was 80 mmol L−1, the mobilized amounts of phenanthrene and pyrene in a yellow‐brown soil column increased by approximately three times compared with the control. The simultaneous decreases in phenanthrene and pyrene not extractable by n‐butanol relative to their initial amounts were 63.17 and 73.38%, respectively, which indicated that a large amount of initially nonextractable PAHs in soils were transformed into n‐butanol‐extractable PAHs. After elution, the PAH residual concentrations in the soil layers followed the order bottom layer > middle layer > top layer. Similar results were observed for experiments using malic acid. Results obtained showed that LMWOAs could dissolve a portion of soil organic matter into solution and disrupt the organic–metal ion–mineral linkages in soils, resulting in PAH release and dissolution of metal ions; however, the mechanism of elution of the PAHs in the soil column by LMWOAs was not in accord with the mechanism by which metal ions were dissolved. The findings of this work may be instructive for remediation strategies in contaminated soils.

Field Measurements and Modeling of Ebullition-Facilitated Flux of Heavy Metals and Polycyclic Aromatic Hydrocarbons from Sediments to the Water Column

Gas ebullition-facilitated transport of metals and polycyclic aromatic hydrocarbons (PAHs) from sediment was investigated in 14 urban waterway locations. Gas ebullition varied widely over four seasons (range 2-450 mmol m(-2) d(-1), mean 140 ± 90 mmol m(-2) d(-1)) and was highly temperature dependent. Ebullition-facilitated metal fluxes were large: 50 ± 13 mg m(-2) d(-1) (Fe), 2.6 ± 0.71 mg m(-2) d(-1) (Zn), 1.5 ± 0.28 mg m(-2) d(-1) (Pb), and 0.19 ± 0.06 mg m(-2) d(-1) (Cr). Ebullition-facilitated PAH fluxes were also large: 0.61 ± 0.27 mg m(-2) d(-1) for anthracene, 0.65 ± 0.28 mg m(-2) d(-1) for benzo[a]pyrene, 0.72 ± 0.28 mg m(-2) d(-1) for chrysene, 3.51 ± 1.23 mg m(-2) d(-1) for fluoranthene, 0.23 ± 0.08 mg m(-2) d(-1) for naphthalene, 3.84 ± 1.47 mg m(-2) d(-1) for phenanthrene, and 2.46 ± 0.86 mg m(-2) d(-1) for pyrene. The magnitude of these fluxes indicates that gas ebullition is an important pathway for release of both PAHs and heavy metals from buried sediments. Multivariate regression analysis of the in situ gas ebullition flux and ebullition-facilitated contaminant flux suggests that metal transport likely is due to sediment particle resuspension, whereas PAH transport is due to both contaminant partitioning to gas bubbles and to sediment resuspension. These results indicate that assumptions regarding the natural recovery potential of ebullition-active sediments should be made with caution.

Influence of bioturbation on bioavailability and toxicity of PAHs in sediment from an electronic waste recycling site in South China

The present study examined the effects of bioturbation by the oligochaete Lumbriculus variegatus on bioavailability and toxicity of sediment-associated polycyclic aromatic hydrocarbons (PAHs) to the oligochaete and the epi-benthic amphipod Hyalella azteca. Various densities of L. variegatus in sediment were used to represent different levels of bioturbation. Total sediment concentration declined with increasing worm density, but bioavailability of PAHs estimated using the biomimetic extractions showed no significant difference among treatments with different worm densities. Alternatively, PAH bioaccumulation by L. variegatus decreased and the growth of the worms was reduced at the highest worm density, which was probably due to overcrowding of organisms, food competition and increasing release of PAHs by bioturbation. Additionally, co-exposure with high density of L. variegatus to contaminated sediment significantly increased PAH accumulation and mortality of H. azteca. The increased toxicity was probably because of the transport of sediment-associated contaminants to sediment surface and water column by the bioturbation by L. variegatus. Overall, the present study showed that bioturbation may alter the toxicity of contaminants in sediment to other organisms, thus the presence of benthic invertebrates and their interactions with the sediment should be considered in future sediment risk assessment.

Lichens reveal air PAH fractionation in the Himalaya

This paper shows that gas/particulate phase partitioning of polycyclic aromatic hydrocarbons (PAHs) can be monitored using lichens. Anthropogenic sources are responsible for the release of PAHs, which are bioaccumulated in plants at various spatial scales based on their physicochemical properties. Atmospheric PAHs are distributed both in the gaseous and particulate states. Here, a lichen species, Dermatocarpon vellereum Zschacke, has been collected at different altitudes in and around the Rudraprayag valley, located in Central Himalayan region of India, in order to study the spatial distribution of PAHs in the valley. Results show that PAH concentration ranged from 0.136 to 4.96 μg g−1. Findings reveal that the bioaccumulation of 2- and 3-ringed PAHs was higher in high-altitude samples, whereas bioaccumulation of fluoranthene, a 4-ringed PAH, showed higher concentration in samples from localities away from town centre. 5- and 6-ring PAHs were then confined to the lower altitude at the base of the valley, thus justifying their particulate-bound nature. This is the first report showing the utility of lichen to biomonitor PAHs in the Himalayan ecosystem.

Formation and distribution of polycyclic aromatic hydrocarbons (PAHs) derived from coal seam combustion: A case study of the Ulanqab lignite from Inner Mongolia, northern China

Abstract Coalfield fires are hazardous to the environment and human health as a result of the release of polycyclic aromatic hydrocarbons (PAHs). The incomplete combustion processes of the Ulanqab lignite from Inner Mongolia of northern China during coalfield fires were simulated in a tubular furnace, and 16 US Environmental Protection Agency priority pollutant PAHs in the flue gas were absorbed and analyzed. The results indicate that incomplete combustion results in a clear increase in PAH emission compared with other combustion methods; this is attributed to the formation of species with two and three benzene rings, such as naphthalene, acenaphthylene, and acenaphthene. Benzo[ a ]pyrene, dibenz[ a , h ]anthracene, and benz[ a ]anthracene make a large contribution to the toxicity equivalent value (TEQ), although they make up a small proportion of the PAHs. With temperature increasing, the total PAH yield peak occurs at 800 °C with a yield of 923.41 mg/kg at an air/coal ratio of 1 m 3 /kg. As the air/coal ratio increases, the amount of PAHs varies with the addition of oxygen. At a ratio of 2 m 3 /kg, the minimum PAH yield of 486.07 mg/kg occurs at 800 °C and the maximum concentrations of the most toxic species, benzo[ a ]pyrene, and dibenz[ a , h ]anthracene, are found. Increasing the coal particle size from 0.25 to 20 mm results in a significant growth of both the yields and TEQs of the PAH species.

Characteristics of Polycyclic Aromatic Hydrocarbon Emissions of Particles of Various Sizes from Smoldering Incense

Release of polycyclic aromatic hydrocarbons (PAHs) in particles of various sizes from smoldering incenses was determined. Among the three types of incense investigated, yielding the total PAH emission rate and factor ranges for PM0.25 were 2,139.7-6,595.6 ng/h and 1,762.2-8,094.9 ng/g, respectively. The PM0.25/PM2.5 ratio of total PAH emission factors and rates from smoldering three incenses was greater than 0.92. This study shows that total particle PAH emission rates and factors were mainly <0.25 μm. Furthermore, the total toxic equivalency emission rates and factors of PAHs for PM0.25 were 241.3-469.7 and 198.8-576.2 ng/g from the three smoldering incenses. The benzo[a]pyrene accounted for 65.2%-68.0% of the total toxic equivalency emission factor of PM2.5 for the three incenses. Experimental results clearly indicate that the PAH emission rates and factors were influenced significantly by incense composition, including carbon and hydrogen content. The study concludes that smoldering incense with low atomic hydrogen/carbon ratios minimized the production of total polycyclic aromatic hydrocarbons of both PM2.5 and PM0.25.

Polycyclic aromatic hydrocarbons (PAHs) in burning and non-burning coal waste piles

The coal waste material that results from Douro Coalfield exploitation was analyzed by gas chromatography with mass spectrometry (GC–MS) for the identification and quantification of the 16 polycyclic aromatic hydrocarbons (PAHs), defined as priority pollutants. It is expected that the organic fraction of the coal waste material contains PAHs from petrogenic origin, and also from pyrolytic origin in burning coal waste piles. The results demonstrate some similarity in the studied samples, being phenanthrene the most abundant PAH followed by fluoranthene and pyrene. A petrogenic contribution of PAHs in unburned samples and a mixture of PAHs from petrogenic and pyrolytic sources in the burning/burnt samples were identified. The lowest values of the sum of the 16 priority PAHs found in burning/burnt samples and the depletion LMW PAHs and greater abundance of HMW PAHs from the unburned coal waste material relatively to the burning/burnt material demonstrate the thermal transformation attributed to the burning process. The potential environmental impact associated with the coal waste piles are related with the release of petrogenic and pyrolytic PAHs in particulate and gaseous forms to soils, sediments, groundwater, surface water, and biodiversity.

Human Exposure Assessment: A Case Study of 8 PAH Contaminated Soils Using in Vitro Digestors and the Juvenile Swine Model

In vitro digestors can be used to provide bioaccessibility values to help assess the risk from incidental human ingestion of contaminated soils. It has been suggested that these digestors may need to include a lipid sink to mimic human uptake processes. We compare the correspondence between in vivo polycyclic aromatic hydrocarbon (PAH) uptake for eight different PAH contaminated soils with PAH release in in vitro digestors in the presence and absence of a lipid sink. Lipid sinks were essential to the success of the in vitro digestors in predicting juvenile swine PAH uptake. In the presence of the lipid sink, results of the In Vitro Digestion model (IVD) closely corresponded with a slope of 0.85 (r(2) = 0.45, P < 0.07) to the in vivo results. The Relative Bioaccessibility Leaching Procedure (RBALP) results did not correspond to the in vivo study but did tightly reflect total soil PAH concentration. We conclude that the basis of this difference between digestors is that the RBALP used an aggressive extraction technique that maximized PAH release from soil. Systemic uptake in juvenile swine was not linked to soil PAH concentration but rather to the thermodynamic properties of the soil.

Leaching experiments on the release of heavy metals and PAH from soil and waste materials

Leaching tests are fundamental tools for the assessment of long-term impact of contaminated waste materials on the soil-groundwater pathway. Experiments were carried out in the framework of standardization and validation of column percolation and batch test procedures, in particular concerning the stipulation of the experimental setup. The colloid release of column and batch experiments was compared and the influence of different column filling heights (12.5–50cm) on the release of polycyclic aromatic hydrocarbons (PAH) from soil was studied, as well as the effect of varying contact times (2.5–16h) on the release of chromium from construction and demolition (C&D) waste and municipal solid waste incineration (MSWI) bottom ash. The results indicate that filtration of the eluate, which is required for batch tests, does not always allow the simulation of the actual colloid amount in soil pore water. Medium column heights four times the inner diameter of the column seemed to provide reasonable equilibrium adjustment conditions and avoid major biodegradation. The release of chromium was only marginally affected by the contact time, varied between 0.115 and 0.150mg/kg for demolition waste eluate at a liquid-to-solid ratio of approximately 5L/kg.

Polycyclic Aromatic Hydrocarbons in Stormwater Runoff from Sealcoated Pavements

Coal-tar based sealcoat has been identified as a source of polycyclic aromatic hydrocarbons (PAHs) in the environment. This study measured the long-term release of PAHs in parking lot runoff and found that the presence of coal tar sealant increased the mass of PAHs released in runoff by over an order of magnitude. PAH concentrations in stormwater from two coal tar sealed parking lots and one unsealed parking lot (control) were monitored over a two-year period. The measured flow volume and concentrations were used to calculate a mass of 9.8-10.8 kg total Σ16 PAHs per hectare exported in stormwater runoff from the two sealed parking lots and 0.34 kg total Σ16 PAHs per hectare from the unsealed control. The study also measured sediment PAH concentration changes in a receiving drainage and found that even partial coverage of a drainage area by coal tar sealant resulted in measurable increases in PAH sediment concentrations; PAH concentrations in sediment in a stormwater swale receiving runoff from both sealed and unsealed lots increased near the outfall from less than 4 mg/kg prior to sealing to 95.7 mg/kg after sealing. Compound ratio plots and principal components analysis were examined and were able to clearly differentiate between pre- and postsealant samples.

PAH desorption from sediments with different contents of organic carbon from wastewater receiving rivers

Many rivers have to receive treated or untreated wastewater as the main water sources in the world, especially in the countries facing with water shortage. For instance, the Haihe and Huaihe River Basin, which are among areas facing crises for water resources in China, receive 33,400 million tons of wastewater per year. As the sediment has large capacity for sorbing hydrophobic organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), it can act as a natural repository for the contaminants. This means pollutants can release into water phase again under some conditions, such as resuspension, sediment dredging, etc. The objective of this research was to study the trends of PAH release from sediments in rivers receiving much wastewater, such as Yongding New River (YD), Northsewer (NS), and Southsewer (SS) from Haihe River Basin. These rivers received most of the wastewater from Tianjin, China and merge into Bohai Bay finally. Sediments (namely YD, NS, and SS) were collected from Yongding New River, Northsewer, and Southsewer, respectively. The physical and chemical properties of the sediments, including particle size distribution, total organic carbon (TOC) and black carbon (BC) contents, elemental compositions, organic functional groups analyzed from Fourier transformed infrared (FTIR), and nuclear magnetic resonance (NMR) spectra, were characterized. PAH desorption from the sediments was measured with the Tenax shaken slurry desorption method. The NS sediment had a greatly higher TOC and BC contents, while lower BC-to-TOC ratio than YD and SS sediments. NMR and FTIR analysis showed that aliphatic carbons were more abundant in NS sediment than SS sediment. The desorption experiments showed that PAHs desorbed more rapidly from YD and NS sediments than from SS sediment. PAH fraction desorbed after each interval during the experiment except 0.8day was significantly correlated with PAH properties among all the three sediments. The higher BC-to-TOC ratio in SS sediment corresponded to slower desorption rate and less desorption extent of PAHs from SS sediment among the three sediments. This probably could be explained by the extremely strong sorption ability of BC. It also proved that the sequestration of PAHs in sediment was not simply the result of higher organic carbon content. Considering the physical and chemical characterization of the sediments and PAH desorption properties comprehensively, BC-to-TOC ratio was a more important factor controlling the behavior of PAHs in sediments than absolute TOC or BC content.

Determination of polycyclic aromatic hydrocarbons in food samples by automated on-line in-tube solid-phase microextraction coupled with high-performance liquid chromatography-fluorescence detection

A simple and sensitive automated method, consisting of in-tube solid-phase microextraction (SPME) coupled with high-performance liquid chromatography-fluorescence detection (HPLC-FLD), was developed for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in food samples. PAHs were separated within 15 min by HPLC using a Zorbax Eclipse PAH column with a water/acetonitrile gradient elution program as the mobile phase. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a CP-Sil 19CB capillary column as an extraction device. Low- and high-molecular weight PAHs were extracted effectively onto the capillary coating from 5% and 30% methanol solutions, respectively. The extracted PAHs were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME HPLC-FLD method, good linearity of the calibration curve ( r > 0.9972) was obtained in the concentration range of 0.05–2.0 ng/mL, and the detection limits ( S/ N = 3) of PAHs were 0.32–4.63 pg/mL. The in-tube SPME method showed 18–47 fold higher sensitivity than the direct injection method. The intra-day and inter-day precision (relative standard deviations) for a 1 ng/mL PAH mixture were below 5.1% and 7.6% ( n = 5), respectively. This method was applied successfully to the analysis of tea products and dried food samples without interference peaks, and the recoveries of PAHs spiked into the tea samples were >70%. Low-molecular weight PAHs such as naphthalene and pyrene were detected in many foods, and carcinogenic benzo[ a]pyrene, at relatively high concentrations, was also detected in some black tea samples. This method was also utilized to assess the release of PAHs from tea leaves into the liquor.

Passive Dosing for Producing Defined and Constant Exposure of Hydrophobic Organic Compounds during in Vitro Toxicity Tests

Toxicity testing of hydrophobic organic compounds (HOCs) in plastic cell culture plates is problematic due to compound losses through volatilization and sorption to the wells and culture medium constituents. This leads to poorly defined exposure and reduced test sensitivity. Passive dosing can overcome these problems by the continual partitioning of HOCs from a dominating reservoir loaded in a biologically inert polymer such as silicone, providing defined and constant freely dissolved concentrations and also eliminating spiking with cosolvents. This study aimed to select a suitable passive dosing format for in vitro tests in multiwell plates and characterize its performance at 37 degrees C. Silicone O-rings were the most suitable format; they were both practical and demonstrated excellent passive dosing performance. (1) The rings were loaded by partitioning from a methanol solution containing polycyclic aromatic hydrocarbons (PAHs) (log K(OW), 3.33-6.43) that served as model compounds, followed by removal of the methanol with water. This resulted in highly reproducible HOC concentrations in the silicone O-rings. (2) The release of PAHs into aqueous solutions was rapid and reproducible, with equilibrium partitioning being reached within hours. (3) The buffering capacity of the O-rings was sufficient to maintain stable concentrations over more than 72 h. The O-rings were then applied to test a range of PAHs at their aqueous solubility in an array of established in vitro cell culture assays with human cells and cell lines. These included the formation of reactive oxygen species, induction of the IL-8 cytokine promoter, and secretion of MCP-1 by the cells. The biological responses depended on the melting point of the individual PAHs and their maximum chemical activities (a(max)). Only those PAHs with the highest a(max) stimulated the formation of reactive oxygen species and MCP-1 secretion, while they inhibited the induction of the IL-8 cytokine promoter.

Enhancing the release and plant uptake of PAHs with a water-soluble purine alkaloid

The effect of a common plant alkaloid, caffeine, on the release and plant uptake of some polycyclic aromatic hydrocarbons (PAHs) in soils was investigated. Cucurbita pepo (ssp. pepo cv. Gold Rush) was grown in PAH-spiked media in the presence and absence of caffeine. Solubility tests initially confirmed the ability of caffeine to dissolve PAHs mixtures of anthracene, phenanthrene, pyrene, benzo[ a]pyrene and benzo[ ghi]perylene. Extraction experiments also highlighted its potential as a PAH-releasing agent from an aged soil. Phytoextraction from a low organic sand medium ( f OC = 0.056 ± 0.03%) indicated a significant enhancement of pyrene uptake with three weeks daily watering with 500 mg L −1 caffeine solution. The average pyrene content of roots was 35.3 and 16.0 μg g −1, in caffeine and non-caffeine set-ups, respectively. In the shoots, the corresponding values were 3.60 and 1.67 μg g −1. Both showed more than twofold increase with caffeine. Caffeine also accumulated mainly in the leaves of the treated samples at 2800 mg kg −1 dry weight. Further tests with a 1-year aged soil ( f OC = 5.2 ± 1%) containing a mixture of phenanthrene and pyrene yielded parallel results. However, lower PAH content in these samples were observed due to the stronger PAHs partitioning in aged-soil matrix. After four weeks of caffeine, phenanthrene in shoots and roots increased by one and a half and four times, respectively. The corresponding enhancements for pyrene were two and a half and three and a half times.