Fraction Of Polycyclic Aromatic Hydrocarbons Research Articles

Increasing PAH (bio)accessibility in historically PAH‐contaminated soils: waste versus food‐grade oils

AbstractBACKGROUND: Vegetable oils are used as environmentally friendly and cost‐efficient amendments for the treatment of contaminated soils, primarily as solvents for the mobilization of polycyclic aromatic hydrocarbons (PAH). In the present study, the efficacies of food‐grade and of waste oils, i.e. thermally ‘abused’ cooking oils, in increasing physical and potential microbial accessibility of soil‐sorbed PAH were evaluated.RESULTS: Abused oils were found to be slightly less efficient for PAH mobilization than their unheated counterparts. After 168 h of extraction, residual concentrations amounted to between 5% and 20% of initial PAH (16 EPA‐compounds). The non‐bioaccessible PAH fraction was reduced by up to 84% using canola or sunflower oil in a bioaccessibility‐limited soil. For all oils, removal efficacy increased with PAH hydrophobicity, including the carcinogenic Benzo(a)pyrene. Simple octanol‐, soil organic carbon–and triolein–water partitioning coefficients did not serve to explain these observations. Increased oil viscosity induced by heating appears to be the priming factor in decreasing extraction efficacy rather than a profound change in the oil constituents' molecular properties, as expressed by Hildebrand solubility parameters.CONCLUSION: The present results show that waste vegetable oils can be used efficiently for the extractive or biological treatment of PAH‐contaminated soils, offering a cost‐efficient and sensible alternative for the use of foodstuff. Copyright © 2012 Society of Chemical Industry

Urban fractionation of polycyclic aromatic hydrocarbons from Dalian soils

This report evidences the fractionation of polycyclic aromatic hydrocarbons (PAHs) from urban to rural areas, and a higher contribution of coal and wood combustion in rural areas. PAHs are persistent semi-volatile organic pollutants in the environment. PAHs originate from the incompleted combustion of fossil fuel and biomass. Cities are usually considered as primary sources of PAHs. Due to different types and loads of fuel consumption in various functional areas of a city, the levels and composition profiles of PAHs are expected to be different. We, therefore, studied the mechanisms ruling PAH distributions in soils from a major Chinese city. Seventeen soil samples were collected in urban traffic areas, residential and park areas, suburban areas and rural areas of Dalian, northeastern China. PAHs were analyzed using a high-performance liquid chromatography. The composition profiles and seasonal variation of PAHs were investigated. Results show that the proportions of low-weight molecular PAHs to total PAHs increased with urban-suburban-rural gradient. This trend is explained by the “urban fractionation” of PAHs. Furthermore, the spring/autumn ratios of PAH concentrations were higher than 1. Specifically, the spring/autumn ratio was 1.79 for two ring PAHs, 1.42 for three ring PAHs, and lower than 1.20 for five and six ring PAHs. The spring/autumn ratios of phenanthrene were higher than 1 and increased with increasing distance from the urban areas. The results imply that the contribution of coal and wood combustion PAHs increases with the urban-suburban-rural gradient.

Compositional fractionation of polyaromatic hydrocarbons in the karst soils, South China

This study aims to explore the condensation and fractionation trends of persistent organic pollutants (POPs) in the karst soils. The tiankeng is a karst surface expression that can act as a focal point for introduction of contaminants to a karst aquifer, which may serve both as condenser for vapor phase POPs and as barrier/sink for particulate associated less volatile POPs. The fractionation of POPs in soils from the upper rim and floor of tiankeng is of interest in understanding the role of tiankeng in the long-distance transport of POPs. In the present study, polycyclic aromatic hydrocarbons (PAHs) in the surface soils from the upper rim and floor of Dashiwei tiankeng in Southern China were analyzed. The total PAH concentrations in soils were 23.40–190 ng g−1, with phenanthrene being the most abundant. The distribution patterns of PAH compounds in the soil samples matched well with their properties. It indicated the heavy PAHs were susceptible to retention by the floor soils of tiankeng than light PAHs. A plot of Cfloor/Crim against PAH molecular weight gave a good positive relationship in the molecular weight range of 152–276. It is suggested that the floor soils can be focal points of more concentrated PAH and deserve attention. The concentrations of total PAHs in the floor soils (43.40–190 ng g−1, mean 87.76 ng g−1) were higher than those in the upper rim (23.40–88.94 ng g−1, mean 57.74 ng g−1). In addition, there was a shift in compound pattern with an increase in the proportion of light PAHs (2–3 rings), a decrease in heavy PAHs (5–6 rings) and a relatively stable content of 4-ring PAHs. A combination of particulate scavenging and cold condensation is proposed as the major mechanism for the compositional fractionation of PAHs in the soils from the upper rim and floor of tiankeng.

Desorption and bioavailability of polycyclic aromatic hydrocarbons in contaminated soil subjected to long‐term in situ biostimulation

The distribution and potential bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soil from a former manufactured-gas plant (MGP) site were examined before and after long-term biostimulation under simulated in situ conditions. Treated soil was collected from the oxygenated zones of two continuous-flow columns, one subjected to biostimulation and the other serving as a control, and separated into low- and high-density fractions. In the original soil, over 50% of the total PAH mass was associated with lower density particles, which made up <2% of the total soil mass. However, desorbable fractions of PAHs were much lower in the low-density material than in the high-density material. After more than 500 d of biostimulation, significant removal of total PAHs occurred in both the high- and low-density materials (77 and 53%, respectively), with three- and four-ring PAHs accounting for the majority of the observed mass loss. Total PAHs that desorbed over a 28-d period were substantially lower in treated soil from the biostimulated column than in the original soil for both the high-density material (23 vs. 63%) and the low-density material (5 vs. 20%). The fast-desorbing fractions quantified by a two-site desorption model ranged from 0.1 to 0.5 for most PAHs in the original soil but were essentially zero in the biostimulated soil. The fast-desorbing fractions in the original soil underestimated the extent of PAH biodegradation observed in the biostimulated column and thus was not a good predictor of PAH bioavailability after long-term, simulated in situ biostimulation.

Integrated assessment of trace pollutants associated with the Korean coastal environment: Exampled from the sediment TIE and triad approaches

Here we present our triad approach followed by major findings based on sediment pollution studies that determined the chemical concentration, biological effect, and community structure associated with trace pollutants in the Korean coastal environment. Since the late-1990s, over several hundred sites along the Korean coast have been surveyed including sediment (including pore-water), water, and biological samples and analyzed for instrumental quantification, in vitro and in vivo bioassays, and benthic community indices. The instrumental data of persistent heavy metals and organic pollutants in Korean sediments generally suggest that concentrations of target pollutants are relatively low to moderate but their distribution is widespread across the coasts. The compositional pattern and spatial distribution suggests that their sources are independent of each other. However, there are local zones with extremely high concentrations of certain pollutants indicating point sources. In order to search for the relationship between chemical concentrations and biological responses, some selected data (n=123) were further analyzed in terms of mass balance analysis (sediment-TIE towards TEQ approach). Most of the dioxin-like activities were observed in the fractions containing dioxins, furans, and certain polycyclic aromatic hydrocarbons (PAHs) and about half of the samples showed significant estrogenic activities in the fractions of PAHs and alkylphenols. Direct relationship(s) between chemical and ecotoxicological data could not be fully addressed between component(s). However, a positive relationship between them became apparent in some cases, indicating a general good agreement between chemical stresses and biological responses. Overall, we found that a sediment triad approach for an integrated assessment of trace pollutants in the coastal environment was extremely useful. It would be much more powerful when all the components are fully and simultaneously analyzed and interpreted.

Physicochemical Characterization of Particulate Emissions from a Compression Ignition Engine Employing Two Injection Technologies and Three Fuels

Alternative fuels and injection technologies are a necessary component of particulate emission reduction strategies for compression ignition engines. Consequently, this study undertakes a physicochemical characterization of diesel particulate matter (DPM) for engines equipped with alternative injection technologies (direct injection and common rail) and alternative fuels (ultra low sulfur diesel, a 20% biodiesel blend, and a synthetic diesel). Particle physical properties were addressed by measuring particle number size distributions, and particle chemical properties were addressed by measuring polycyclic aromatic hydrocarbons (PAHs) and reactive oxygen species (ROS). Particle volatility was determined by passing the polydisperse size distribution through a thermodenuder set to 300 °C. The results from this study, conducted over a four point test cycle, showed that both fuel type and injection technology have an impact on particle emissions, but injection technology was the more important factor. Significant particle number emission (54%-84%) reductions were achieved at half load operation (1% increase-43% decrease at full load) with the common rail injection system; however, the particles had a significantly higher PAH fraction (by a factor of 2 to 4) and ROS concentrations (by a factor of 6 to 16) both expressed on a test-cycle averaged basis. The results of this study have significant implications for the health effects of DPM emissions from both direct injection and common rail engines utilizing various alternative fuels.

Cell absorption induced desorption of hydrophobic organic contaminants from digested soil residue

Oral ingestion of contaminated soil is an important pathway of human exposure to hydrophobic organic contaminants (HOCs), particularly for children in developing countries. The mobilization potential of various contaminants from ingested soil is often characterized using an in vitro gastrointestinal model, based on the quantities of contaminants remaining in digestive fluid after digestion and separation. Recently, it was experimentally demonstrated that a large fraction of mobilized contaminants sorbed on the digested residue could be released if the dissolved fraction was removed by intestinal absorption. This hypothesis was further tested in this study. Soil spiked with dichlorodiphenyltrichloroethane and its metabolites (DDXs) and polycyclic aromatic hydrocarbons (PAHs) was digested using an in vitro gastrointestinal model. A human colon carcinoma cell line (Caco-2) was cultured in digestive fluid with or without soil residue (pre-equilibrated with the soil) for 2 h. A large proportion of the contaminants (37–68%) was sorbed on the digested residue. Without this residue, 66 ± 13% of DDXs and 73 ± 14% of PAHs dissolved in the fluid, as means and standard deviations, were absorbed by the cell monolayer after exposure. With both digestive fluid and residue, the sorbed fraction of PAHs and DDXs decreased by 38–92%, while the ratios of the cellular to the dissolved concentrations were 2.7–2.8 times higher than those without the residue. This supported the hypothesis that the cell absorption of dissolved HOCs induces desorption of the sorbed fraction from digestive residue, and the desorbed HOCs can be absorbed as well.

Using deuterated PAH amendments to validate chemical extraction methods to predict PAH bioavailability in soils

Validating chemical methods to predict bioavailable fractions of polycyclic aromatic hydrocarbons (PAHs) by comparison with accumulation bioassays is problematic. Concentrations accumulated in soil organisms not only depend on the bioavailable fraction but also on contaminant properties. A historically contaminated soil was freshly spiked with deuterated PAHs (dPAHs). dPAHs have a similar fate to their respective undeuterated analogues, so chemical methods that give good indications of bioavailability should extract the fresh more readily available dPAHs and historic more recalcitrant PAHs in similar proportions to those in which they are accumulated in the tissues of test organisms. Cyclodextrin and butanol extractions predicted the bioavailable fraction for earthworms ( Eisenia fetida) and plants ( Lolium multiflorum) better than the exhaustive extraction. The PAHs accumulated by earthworms had a larger dPAH:PAH ratio than that predicted by chemical methods. The isotope ratio method described here provides an effective way of evaluating other chemical methods to predict bioavailability.

The Spitzer Surveys of the Small Magellanic Cloud: Insights into the Life-Cycle of Polycyclic Aromatic Hydrocarbons

We present the results of modeling dust spectral energy distributions (SEDs) across the Small Magellanic Cloud (SMC) with the aim of mapping the distribution of polycyclic aromatic hydrocarbons (PAHs) in a low-metallicity environment. Using Spitzer Survey of the SMC (S 3 MC) photometry from 3.6 to 160 µm over the main star-forming regions of the Wing and Bar of the SMC along with spectral mapping observations from 5 to 38 µm from the Spitzer Spectroscopic Survey of the Small Magellanic Cloud (S 4 MC) in selected regions, we model the dust spectral energy distribution and emission spectrum to determine the fraction of dust in PAHs across the SMC. We use the regions of overlaping photometry and spectroscopy to test the reliability of the PAH fraction as determined from SED fits alone. The PAH fraction in the SMC is low compared to the Milky Way and variable– with relatively high fractions (qPAH� 1 − 2%) in molecular clouds and low fractions in the diffuse ISM (average hqPAHi = 0.6%). We use the map of PAH fraction across the SMC to test a number of ideas regarding the production, destruction and processing of PAHs in the ISM. We find weak or no correlation between the PAH fraction and the distribution of carbon AGB stars, the location of supergiant H I shells and young supernova remnants, and the turbulent Mach number. We find that the PAH fraction is correlated with CO intensity, peaks in the dust surface density and the molecular gas surface density as determined from 160 µm emission. The PAH fraction is high in regions of active star-formation, as predicted by its correlation with molecular gas, but is supressed in H II regions. Because the PAH fraction in the diffuse ISM is generally very low–in accordance with previous work on modeling the integrated SED of the SMC–and the PAH fraction is relatively high in molecular regions, we suggest that PAHs are destroyed in the diffuse ISM of the SMC and/or PAHs are forming in molecular clouds. We discuss the implications of these observations for our understanding of the PAH life cycle, particularly in low-metallicity and/or primordial galaxies. Subject headings: dust, extinction — infrared: ISM — Magellanic Clouds

Gas–particle partitioning of polycyclic aromatic hydrocarbons (PAHs) in an urban traffic site in Eskisehir, Turkey

Gas and particle-phase ambient air samples were collected at a traffic site in Eskisehir over a six-month period between January and October 2006. Gas/particle concentrations of 15 PAHs were determined by analyzing integrated glass fiber and polyurethane foam samples. On average, 66% of the total concentrations of PAHs were found in the gas-phase in heating and 69% in the non-heating period samples. Heating period PAH concentrations were found to be 7 to 8 times greater than concentrations in non-heating period samples. Multiple linear regression analysis was carried out to determine the effect of meteorological parameters on measured individual PAH concentrations. Temperature, wind speed and wind direction explained 43% (dibenzo[ a,h]anthracene and benzo[ a]pyrene) to 78% (phenanthrene) of the variability in atmospheric PAH concentrations. Results of the multiple linear regression analysis indicated that temperature and wind speed were statistically significant factors for the measured concentrations of PAHs. Gas–particle partitioning coefficients, (K p) and particle-phase fractions (Φ) of PAHs, were correlated with supercooled vapor pressures ( P L o ). Application of non-linear fitting for Φ versus log P L o plots was found to be more robust than linear logarithmic regressions of log K p versus log P L o plots. Particle-phase fractions (Φ) for each PAH were also calculated using octanol–air and soot–air partitioning models. Soot model resulted better predictions of Φ for fluorene, phenanthrene, anthracene, fluoranthene and pyrene. Both two models yielded very similar particle-phase fractions having very close results to experimentally obtained Φ values for the rest of PAHs measured.

&lt;b&gt;Aliphatic and polycyclic aromatic hydrocarbons profiles of photomodified natural bitumen of Agbabu, Southwestern Nigeria&lt;/b&gt;

The impact of sunlight on aliphatic and polycyclic aromatic hydrocarbons profiles of Agbabu natural bitumen in Nigeria was investigated. The raw flow type of the bitumen was purified and exposed to sunlight for six consecutive months. Different portions of the bitumen were withdrawn at an interval of one month and were separated into aliphatic and polycyclic aromatic hydrocarbon fractions by column chromatography, followed by the GC analyses of various fractions. The total aliphatic hydrocarbon content was found to be 485, 424, 416 and 392 g/kg for control, one, three and six months solar-irradiated bitumen samples, respectively; while the total polycyclic aromatic hydrocarbons content found in the control, one, three and six months solar-irradiated bitumen samples were 708, 733, 609 and 638 µg/g, respectively. The effects of sunlight on the compositional patterns of bitumen were discussed. KEY WORDS: Agbabu, Bitumen, Sunlight, GC, Aliphatic hydrocarbon, Polycyclic aromatic hydrocarbon Bull. Chem. Soc. Ethiop. 2010 , 24(3), 461-466.

Emission factors and particulate matter size distribution of polycyclic aromatic hydrocarbons from residential coal combustions in rural Northern China

Coal consumption is one important contributor to energy production, and is regarded as one of the most important sources of air pollutants that have considerable impacts on human health and climate change. Emissions of polycyclic aromatic hydrocarbons (PAHs) from coal combustion were studied in a typical stove. Emission factors (EFs) of 16 EPA priority PAHs from tested coals ranged from 6.25 ± 1.16 mg kg −1 (anthracite) to 253 ± 170 mg kg −1 (bituminous), with NAP and PHE dominated in gaseous and particulate phases, respectively. Size distributions of particulate phase PAHs from tested coals showed that they were mostly associated with particulate matter (PM) with size either between 0.7 and 2.1 μm or less than 0.4 μm (PM 0.4). In the latter category, not only were more PAHs present in PM 0.4, but also contained higher fractions of high molecular weight PAHs. Generally, there were more than 89% of total particulate phase PAHs associated with PM 2.5. Gas-particle partitioning of freshly emitted PAHs from residential coal combustions were thought to be mainly controlled by absorption rather than adsorption, which is similar to those from other sources. Besides, the influence of fuel properties and combustion conditions was further investigated by using stepwise regression analysis, which indicated that almost 57 ± 10% of total variations in PAH EFs can be accounted for by moisture and volatile matter content of coal in residential combustion.

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.

Polycyclic aromatic hydrocarbons in air on small spatial and temporal scales – I. Levels and variabilities

Polycyclic aromatic hydrocarbons (PAHs) were measured together with inorganic air pollutants at two urban sites and one rural background site in the Banja Luka area, Bosnia and Hercegovina, during 72 h in July 2008 using a high time resolution (5 samples per day) with the aim to study the spatial and temporal variabilities and to explore the significance of averaging effects inherent to 24 h-sampling. Measurement uncertainty was quantified on basis of three independent side-by-side samplers, deployed at one of the sites. PAH abundances in the urban and rural environments differed largely. Levels at the urban sites exceeded the levels at the rural site by >100%. The discrepancy was largely dominated by emission of 3–4 ring PAHs in the city, while 5–6 ring PAHs were more evenly distributed between city sites and the hill site. During the night a higher fraction of the semivolatile PAHs might have been stored in the soil or sorbed to surfaces. PAH patterns were undistinguishable across the three sites. However, concentrations of more particle-associated substances differed significantly between the urban sites than between one of the urban sites and the rural site (3 σ uncertainty). Time-averaging (on a 24 h-basis) would have masked the significant inter-site differences of half of the substances which were found at different levels (on a 4 h-basis).

Mobility of Polycyclic Aromatic Hydrocarbons in the Gastrointestinal Tract Assessed Using an in Vitro Digestion Model with Sorption Rectification

In a previous study, it was demonstrated that mobilization of organochlorine pesticides would be underestimated by an in vitro gastrointestinal model if the sorption of the mobilized pollutants on the digestive residue was not taken into consideration. A multiple fluid/solid ratio procedure was developed to characterize the sorption. In this study, the sorption hypothesis was further tested for polycyclic aromatic hydrocarbons (PAHs), and the sorption of the mobilized PAHs on digestive residue was directly characterized by spiking the gastrointestinal digest with several deuterated PAHs. It was demonstrated that 10-41% of the spiked deuterated PAHs were sorbed on the assimilated residue, which would remain in the solid phase after separation. It appears that the mobility of PAHs would be underestimated if only those dissolved in the fluid is measured. The total mobilized fraction of a PAH compound was defined as a sum of that dissolved in the fluid and that sorbed on the residue. The average mobilized PAH fractions in the studied soils was 70 +/- 24% which was significantly higher than 47 +/- 19% in the fluid. It was also found that the sorption of the mobilized PAHs on the digestive residue was positively correlated with both soil organic carbon (SOC) and molecular weight (MW(t)) of PAHs, and a regression model was developed so that the sorption of different PAHs on soils with different SOCs could be estimated.

Determination of polycyclic aromatic hydrocarbons in aquatic products by HPLC-fluorescence

This paper analyzed 12 polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene, fluoranthene, anthracene, benzo[a]anthracene, chrysene, fluorene, phenanthrene and pyrene, in aquatic products by using a fluorimetric-detection RP-HPLC method. The preliminary treatment procedure was based on microwave-assisted extraction and neutral Al 2O 3 solid phase purification, and a selective isolation of PAHs from aquatic samples was carried out. The isolated fractions of PAHs were determined by HPLC with fluorescence detection. The test results suggest that the detection limits for the PAHs were from 0.0048 ng/mL to 0.075 ng/mL based on a signal-to-noise ratio of 3:1. The recoveries were from 85.26 ± 5.12% to 104.63 ± 0.95%. This proposed method was successfully applied to 35 aquatic samples, in which variable levels of summed PAHs were detected, ranging from 0.0 to 57.76 μg/kg.

Effect-directed analysis of contaminated sediment from the wastewater canal in Pancevo industrial area, Serbia

Wastewater canal (WWC) in Pancevo industrial area in Serbia, whose main environmental receptor is the River Danube, is a well known hot-spot of contamination. WWC sediments have been assessed by UNEP based on chemical target analysis. However, integrative biological data on exposure to hazardous compounds are only provided by the present study which aims at evaluating whether the monitored compounds sufficiently reflect potential hazards and to suggest additional compounds to include in monitoring and hazard assessment by applying effect-directed analysis (EDA) based on arylhydrocarbon receptor-mediated activity and cytotoxicity. Multistep NP-HPLC fractionation provided 18 fractions co-eluting with polychlorinated biphenyls (PCBs), polychlorinated dibenzo- p-dioxins (PCDDs), polycyclic aromatic hydrocarbons (PAHs) and more polar compounds. PAHs fractions exhibited great potencies to induce ethoxyresorufin- o-deethylase (EROD) in H4IIE rat hepatoma cell line expressed as 2,3,7,8-tetrachlorodibenzo- p-dioxin equivalents (TCDD-EQ) (0.1–34.6 × 10 3 pg g −1 dry weight). Chemical analysis of the most active fractions revealed great concentrations of PAHs (up to 292 × 10 2 ng g −1 sediment equivalents (SEQ)), methylated PAHs (up to 900 × 10 2 ng g −1 SEQ), and other alkyl-substituted PAHs. Only minor portions of biologically derived TCDD-EQs could be attributed to monitored PAHs with known relative potencies (REPs). We hypothesize that a major part of the activity is due to non-monitored alkylated and heterocyclic PAHs. Results of the cell cytotoxicity/proliferation assay on H4IIE cell line suggest the presence of sediment pollutants with pronounced potency to disturb cell growth.

Relative contribution of DNA strand breaks and DNA adducts to the genotoxicity of benzo[a]pyrene as a pure compound and in complex mixtures

Polycyclic aromatic hydrocarbons (PAH) produced upon incomplete combustion of organic matter are suspected to be carcinogenic to humans. In the present work, we especially studied the genotoxicity of benzo[a]pyrene (B[a]P), pure or in mixtures, with emphasis placed on the contribution of oxidative stress and alkylation. A comparison was made between the extent of DNA strand breaks as determined by the Comet assay and the number of DNA adducts to the diol epoxide metabolite of B[a]P measured by HPLC–mass spectrometry. HepG2 cultured human hepatocytes were treated with either pure B[a]P or particulate matter extracted from air samples collected in an urban peri-industrial site or in a metallurgic plant. Treatment with pure B[a]P did not induce increase in Comet measurements below a concentration of 1 μM whereas adducts were observed for concentrations as low as 0.025 μM. Very different results were obtained with environmental samples. Increase in the Comet score was observed with both urban and industrial mixtures containing 0.16 μM of B[a]P, especially for samples of urban origin. Comparison with the effect of the reconstituted PAH fraction of the mixtures allowed us to conclude that the induction of strand breaks results from the action of other components of the samples. In addition, a 30% potentialization and a 90% inhibition in the level of DNA adducts with respect to exposure to 0.16 μM pure B[a]P were observed for cells exposed to industrial and urban mixtures, respectively. These results contrast with the 6-fold enhancement in the yield of BPDE adducts in cells exposed to the reconstituted PAH fraction with respect to pure BaP. Altogether, our data emphasize that (i) a combination of analytical approaches is required to assess the genotoxicity of complex mixtures and (ii) risk assessment based on additivity consideration such as toxic equivalent factors may be misleading.

Effect-Directed Analysis of Contaminated Sediments with Partition-Based Dosing Using Green Algae Cell Multiplication Inhibition

Effect-directed analysis (EDA) has been frequently and successfully used to identify key toxicants in sediment extracts. However, by disregarding bioavailability this approach may lead to a biased prioritisation of fractions and toxicants with respect to hazards and risks. To overcome this problem the present EDA of sediment components from the Bílina river (Most Czech Republic), that inhibit growth of the green algae Scenedesmus vacuolatus, applies a novel partition-based dosing technique to prioritize and identify major toxic fractions and compounds in comparison to conventional solvent dosing. The novel dosing technique is based on partitioning from loaded silicone rods to the aqueous phase similar to partition processes that determine exposure in native sediment-water systems. In the present study the application of partition-based dosing had a big influence suggesting polar compounds such as triclosan as key toxicants while polycyclic aromatic hydrocarbon (PAH) fractions did not exhibit significant effects. In contrast, conventional dosing prioritized mainly PAHs in agreement with previous studies. For both approaches individual toxicants could be confirmed quantitatively based on the index of confirmation quality (ICQ), which compares the effect of fractions and artificial mixtures of identified and quantified toxicants over the full range of effect levels.

Characterization of PM 2.5-bound polycyclic aromatic hydrocarbons in Atlanta—Seasonal variations at urban, suburban, and rural ambient air monitoring sites

Twenty-eight polycyclic aromatic hydrocarbons (PAH) and methylated PAHs (Me-PAH) were measured in daily PM 2.5 samples collected at an urban site, a suburban site, and a rural site in and near Atlanta during 2004 (5 samples/month/site). The suburban site, located near a major highway, had higher PM 2.5-bound PAH concentrations than did the urban site, and the rural site had the lowest PAH levels. Monthly variations are described for concentrations of total PAHs (∑PAHs) and individual PAHs. PAH concentrations were much higher in cold months than in warm months, with average monthly ∑PAH concentrations at the urban and suburban-highway monitoring sites ranging from 2.12 to 6.85 ng m −3 during January–February and November–December 2004, compared to 0.38–0.98 ng m −3 during May–September 2004. ∑PAH concentrations were found to be well correlated with PM 2.5 and organic carbon (OC) within seasons, and the fractions of PAHs in PM 2.5 and OC were higher in winter than in summer. Methyl phenanthrenes were present at higher levels than their un-substituted homologue (phenanthrene), suggesting a petrogenic (unburned petroleum products) input. Retene, a proposed tracer for biomass burning, peaked in March, the month with the highest acreage and frequency of prescribed burning and unplanned fires, and in December, during the high residential wood-burning season, indicating that retene might be a good marker for burning of all biomass materials. In contrast, potassium peaked only in December, indicating that it might be a more specific tracer for wood-burning.