Influence of temperature and origin of dissolved organic matter on the partitioning behavior of polycyclic aromatic hydrocarbons

Background, aim, and scope  

The behavior of polycyclic aromatic hydrocarbons (PAHs) is affected by dissolved organic matter (DOM) present in pore water of soils and sediments. Since partitioning to DOM reduces the bioavailable or freely dissolved PAH concentration in pore water, it is important to assess the effect of environmental variables on the magnitude of dissolved organic matter to water partition coefficients (K _DOC). The objective of this study was to apply passive samplers to measure freely dissolved PAHs allowing depletion from the aqueous phase. The method was applied to determine K _DOC at different temperatures for a selection of PAHs with natural DOM of very different origin.     

Source apportionment and source/sink relationships of PAHs in the coastal atmosphere of Chicago and Lake Michigan

Multivariate statistical techniques were used to investigate source apportionment and source/sink relationships for polycyclic aromatic hydrocarbons (PAHs) in the urban and adjacent coastal atmosphere of Chicago/Lake Michigan in 1994–1995. The PAH signatures for the atmospheric particle phase, surface water particle phase and sediments indicate that atmospheric deposition is the major source of PAHs to the sediments and water column particulate phase of Lake Michigan. The PAH signature for the atmospheric gas phase and water dissolved phase indicate an intimate linkage between the lake and its overlying atmosphere. A modified factor analysis-multiple regression model was successfully applied to the source apportionment of atmospheric PAHs (gas+particle). Coal combustion accounted for 48±5% of the ΣPAH concentration in both the urban and adjacent coastal atmosphere, natural gas combustion accounted for 26±2%, coke ovens accounted for 14±3%, and vehicle emissions (gas+diesel) accounted for 9±4%. Each is an identified source category for the region. These results are consistent with the mix of fossil fuel combustion sources and ratios of indicator PAHs.     

Atmospheric distribution of polycyclic aromatic hydrocarbons and deposition to Galveston Bay,Texas, USA

Estimates of the atmospheric deposition to Galveston Bay of polycyclic aromatic hydrocarbons (PAHs) are made using precipitation and meteorological data that were collected continuously from 2 February 1995 to 6 August 1996 at Seabrook, TX, USA. Particulate and vapor phase PAHs in ambient air and particulate and dissolved phases in rain samples were collected and analyzed. More than 95% of atmospheric PAHs were in the vapor phase and about 73% of PAHs in the rain were in the dissolved phase. Phenanthrene and napthalene were the dominant compounds in air vapor and rain dissolved phases, respectively, while 5 and 6 ring PAH were predominant in the particulate phase of both air and rain samples. Total PAH concentrations ranged from 4 to 161 ng m⁻³ in air samples and from 50 to 312 ng l⁻¹ in rain samples. Temporal variability in total PAH air concentrations were observed, with lower concentrations in the spring and fall (4–34 ng m ⁻³) compared to the summer and winter (37–161 ng m⁻³). PAHs in the air near Galveston Bay are derived from both combustion and petroleum vaporization. Gas exchange from the atmosphere to the surface water is estimated to be the major deposition process for PAHs (1211 μg m^{− 2} yr^{− 1}), relative to wet deposition (130 μg m⁻² yr^{− 1}) and dry deposition (99 μg m⁻² yr^{− 1}). Annual deposition of PAHs directly to Galveston Bay from the atmosphere is estimated as 2  t yr⁻¹.     

Effect of oxic/anoxic switches on bacterial communities and PAH biodegradation in an oil-contaminated sludge

Purpose  

We studied the effect of alternations of aeration on both the autochthonous bacterial communities from an oily sludge to the endogenous polycyclic aromatic hydrocarbons (PAH) biodegradation compared to a permanent oxic condition.     

Identification and removal of polycyclic aromatic hydrocarbons in wastewater treatment processes from coke production plants

Identification and removal of polycyclic aromatic hydrocarbons (PAHs) were investigated at two coke plants located in Shaoguan, Guangdong Province of China. Samples of raw coking wastewaters and wastewaters from subunits of a coke production plant were analyzed using gas chromatography–mass spectrometry (GC/MS) to provide a detailed chemical characterization of PAHs. The identification and characterization of PAH isomers was based on a positive match of mass spectral data of sample peaks with those for PAH isomers in mass spectra databases with electron impact ionization mass spectra and retention times of internal reference compounds. In total, 270 PAH compounds including numerous nitrogen, oxygen, and sulfur heteroatomic derivatives were positively identified for the first time. Quantitative analysis of target PAHs revealed that total PAH concentrations in coking wastewaters were in the range of 98.5?±?8.9 to 216?±?20.2 μg/L, with 3-4-ring PAHs as dominant compounds. Calculation of daily PAH output from four plant subunits indicated that PAHs in the coking wastewater came mainly from ammonia stripping wastewater. Coking wastewater treatment processes played an important role in removing PAHs in coking wastewater, successfully removing 92 % of the target compounds. However, 69 weakly polar compounds, including PAH isomers, were still discharged in the final effluent, producing 8.8?±?2.7 to 31.9?±?6.8 g/day of PAHs with potential toxicity to environmental waters. The study of coking wastewater herein proposed can be used to better predict improvement of coke production facilities and treatment conditions according to the identification and removal of PAHs in the coke plant as well as to assess risks associated with continuous discharge of these contaminants to receiving waters.     

Microbial communities to mitigate contamination of PAHs in soil—possibilities and challenges: a review

Background, aim, and scope  

Although highly diverse and specialized prokaryotic and eukaryotic microbial communities in soil degrade polycyclic aromatic hydrocarbons (PAHs), most of these are removed slowly. This review will discuss the biotechnological possibilities to increase the microbial dissipation of PAHs from soil as well as the main biological and biotechnological challenges.     

Polycyclic aromatic hydrocarbons in rainwater and surface waters of Lake Maggiore, a subalpine lake in Northern Italy

Fourteen polycyclic aromatic hydrocarbons (PAHs) were measured in surface waters and precipitation inputs to Lake Maggiore, a subalpine lake in Northern Italy, from July 2003 to January 2004. Particulate and dissolved phases in surface water and rain samples were determined. Analyses of PAHs were performed using XAD-2 resin to isolate the dissolved PAHs and subsequent extraction by accelerated solvent extraction (ASE). Both the dissolved and particulate phase PAH patterns in surface water and rainwater samples were dominated by the low molecular weight compounds (e.g., phenanthrene, fluoranthene and pyrene). More than 85% of PAHs in surface waters and 72% of PAHs in rainwater were associated to the dissolved phase. The SigmaPAH concentrations in surface waters (particulate and dissolved phases) were 0.584 +/- 0.033 ng l(-1), 2.9 +/- 0.312 ng l(-1) and in rainwater (particulate and dissolved phases) 27.5 +/- 2 ng l(-1), 75.4 +/- 9 ng l(-1), respectively. Temporal variability of PAH concentrations in rain and surface water samples were observed, with higher concentrations in November and December, coinciding with the largest precipitation amounts. The comparison of PAH signatures in rainwater and surface waters seems to indicate that wet deposition (2.5-41 microg m(-2) month(-1)) is the main source of PAH contamination into surface waters of Lake Maggiore.     

Induction of the P450 reporter gene system bioassay by polycyclic aromatic hydrocarbons in Ulsan Bay (South Korea) sediments

Polycyclic aromatic hydrocarbons (PAHs) and induction of the P450 reporter gene system (RGS) for 6- and 16-h exposure periods were determined in organic extracts of Ulsan Bay (South Korea) sediments to assess the utility of this bioassay as a screening tool for PAH contamination. The sum of the concentrations of 23 individual PAHs in 30 sediment samples (sigma PAH) based on GC-MS analysis ranged from 0.05 to 6.1 micrograms/g dry wt. P450 RGS fold induction ranged from 4.0 to 320 micrograms/g based on benzo[a]pyrene toxic equivalents (BaPEq). P450 RGS BaPEq and the 'chemical BaPEq', defined as the sum of the products of individual PAH concentrations and pre-determined toxic equivalency factors, exhibited very strong positive correlations with sigma PAH (r2 > 0.90; P < 0.001). Fold induction did not increase (and in some cases decreased) after the optimal incubation period (6 h) for PAHs, indicating that other compounds known to induce the P450 RGS (e.g. chlorinated organics) were not present at levels effecting significant induction. This was supported by GC-ECD analysis where non-ortho and mono-ortho polychlorinated biphenyls (PCBs) known to be strong P450 RGS inducers were found to be at very low or non-detectable levels in samples with the highest P450 RGS responses. The profound difference in PAH profiles for the two most contaminated sites suggested that this assay is especially sensitive for selected PAHs with greater than four rings. Combined with previous results, the P450 RGS shows promise as a useful screening tool for predicting deleterious biological effects resulting from CYP1A1-inducing, sediment-associated chemicals, particularly high molecular weight PAHs.     

Investigation of potentially bioavailable and sequestrated forms of polycyclic aromatic hydrocarbons during sewage sludge composting

The present study focuses on the influence of the composting process on the formation of potentially bioavailable and sequestrated PAH fractions. The potentially bioavailable fraction was determined by means of a mild-solvent extraction (with n-butanol). The total and potentially bioavailable PAH content was evaluated in the consecutive composting stages, i.e. at the onset of the experiment, after the stabilization phase (on the 35th day), and after the maturation phase (on the 76th day). Four municipal sewage sludges with differentiated PAH content were selected for the present experiment. Eleven PAHs from the US EPA list (with exception of naphthalene, acenaphthylene, acenaphtene, fluorene and benz[ah]anthracene) were determined for the purpose of this experiment. The content of the total PAHs ranged from 3052 to 10352microg kg(-1). The share of the potentially bioavailable fraction was at a similar level in the sludge samples tested and ranged from 75% to 81%. Greater differences were noted in the share of the bioavailable fraction in the case of individual PAH groups. The influence of the composting process on the contribution of the potentially bioavailable fraction of the PAH clearly depended on the stage of the experiment and sewage sludge type. However, in the case of all sludges, a lowering of the bioavailable fraction by 19-52% as compared to the level at the outset of the experiment was observed. During the first phase (stabilization) of the sewage sludge composting process, a reduction of the PAH content took place mainly at the expense of potentially bioavailable fraction, whereas in the second phase (maturation), sequestration processes predominated. The above phenomenon was most clearly visible for the 6-rings PAHs.     

Photochemistry of phenanthrene,pyrene, and fluoranthene in ice and snow

Although polycyclic aromatic hydrocarbons (PAHs) are common pollutants in snow, there is little quantitative data about their rates of photodegradation in this environment. To begin to address this gap, we have measured the degradation kinetics of phenanthrene, pyrene, and fluoranthene on ice, as these are the most abundant PAHs in arctic snow. Frozen aqueous solutions of individual PAHs, with and without added hydrogen peroxide (HOOH) as a source of hydroxyl radical (OH), were illuminated with simulated sunlight. For all three PAHs, direct photodecay is the main mechanism of degradation, while OH-initiated indirect photodegradation is a minor sink. Rate constants (±1 SE) for direct photodegradation extrapolated to midday, surface snow conditions at Summit, Greenland on the summer solstice are 3.8 (±0.8) × 10^?5, 28 (±3) × 10^?5, and 1.4 (±0.7) × 10^?5 s^?1 for phenanthrene, pyrene, and fluoranthene, respectively. Apparent quantum efficiencies for photodegradation with simulated sunlight were 3.8 (±0.8) × 10^?3, 4.3 (±0.5) × 10^?4, and 2 (±1) × 10^?5, respectively. Calculated PAH lifetimes in surface snow under Summit conditions are 1–19 h during mid-summer, but increase to >100 days in the dark winter. While the short photodegradation lifetimes in the summer suggest that there should be no appreciable PAH levels in this season, past measurements at Summit sometimes show significant levels of these PAHs in summer surface snow. This discrepancy is likely due to differences in PAH location between lab samples (where the PAHs are probably in quasi-liquid layers) and real snow (where PAHs are likely primarily associated with particulate matter).     

Principles of microbial PAH-degradation in soil

Interest in the biodegradation mechanisms and environmental fate of polycyclic aromatic hydrocarbons (PAHs) is motivated by their ubiquitous distribution, their low bioavailability and high persistence in soil, and their potentially deleterious effect on human health. Due to high hydrophobicity and solid-water distribution ratios, PAHs tend to interact with non-aqueous phases and soil organic matter and, as a consequence, become potentially unavailable for microbial degradation since bacteria are known to degrade chemicals only when they are dissolved in water. As the aqueous solubility of PAHs decreases almost logarithmically with increasing molecular mass, high-molecular weight PAHs ranging in size from five to seven rings are of special environmental concern. Whereas several reviews have focussed on metabolic and ecological aspects of PAH degradation, this review discusses the microbial PAH-degradation with special emphasis on both biological and physico-chemical factors influencing the biodegradation of poorly available PAHs.     

AhR agonist and genotoxicant bioavailability in a PAH-contaminated soil undergoing biological treatment

Background, aim, and scope  Degradation of the 16 US EPA priority PAHs in soil subjected to bioremediation is often achieved. However, the PAH loss is not always followed by a reduction in soil toxicity. For instance, bioanalytical testing of such soil using the chemical-activated luciferase gene expression (CALUX) assay, measuring the combined effect of all Ah receptor (AhR) activating compounds, occasionally indicates that the loss of PAHs does not correlate with the loss of Ah receptor-active compounds in the soil. In addition, standard PAH analysis does not address the issue of total toxicant bioavailability in bioremediated soil. Materials and methods  To address these questions, we have used the CALUX AhR agonist bioassay and the Comet genotoxicity bioassay with RTL-W1 cells to evaluate the toxic potential of different extracts from a PAH-contaminated soil undergoing large-scale bioremediation. The extracts were also chemically analyzed for PAH16 and PCDD/PCDF. Soil sampled on five occasions between day 0 and day 274 of biological treatment was shaken with n-butanol with vortex mixing at room temperature to determine the bioavailable fraction of contaminants. To establish total concentrations, parts of the same samples were extracted using an accelerated solvent extractor (ASE) with toluene at 100°C. The extracts were tested as inducers of AhR-dependent luciferase activity in the CALUX assay and for DNA breakage potential in the Comet bioassay. Results  The chemical analysis of the toluene extracts indicated slow degradation rates and the CALUX assay indicated high levels of AhR agonists in the same extracts. Compared to day 0, the bioavailable fractions showed no decrease in AhR agonist activity during the treatment but rather an up-going trend, which was supported by increasing levels of PAHs and an increased effect in the Comet bioassay after 274 days. The bio-TEQs calculated using the CALUX assay were higher than the TEQs calculated from chemical analysis in both extracts, indicating that there are additional toxic PAHs in both extracts that are not included in the chemically derived TEQ. Discussion  The response in the CALUX and the Comet bioassays as well as the chemical analysis indicate that the soil might be more toxic to organisms living in soil after 274 days of treatment than in the untreated soil, due to the release of previously sorbed PAHs and possibly also metabolic formation of novel toxicants. Conclusions  Our results put focus on the issue of slow degradation rates and bioavailability of PAHs during large-scale bioremediation treatments. The release of sorbed PAHs at the investigated PAH-contaminated site seemed to be faster than the degradation rate, which demonstrates the importance of considering the bioavailable fraction of contaminants during a bioremediation process. Recommendations and perspectives  It has to be ensured that soft remediation methods like biodegradation or the natural remediation approach do not result in the mobilization of toxic compounds including more mobile degradation products. For PAH-contaminated sites this cannot be assured merely by monitoring the 16 target PAHs. The combined use of a battery of biotests for different types of PAH effects such as the CALUX and the Comet assay together with bioavailability extraction methods may be a useful screening tool of bioremediation processes of PAH-contaminated soil and contribute to a more accurate risk assessment. If the bioremediation causes a release of bound PAHs that are left undegraded in an easily extracted fraction, the soil may be more toxic to organisms living in the soil as a result of the treatment. A prolonged treatment time may be one way to reduce the risk of remaining mobile PAHs. In critical cases, the remediation concept might have to be changed to ex situ remediation methods.     

Particle size distributions of polycyclic aromatic hydrocarbons in rural and urban atmosphere of Tianjin, China

The size distributions of 16 polycyclic aromatic hydrocarbons (PAHs) and particle mass less than 10 microm in aerodynamic diameter (Dp) were measured using a nine-stage low-volume cascade impactor at rural and urban sites in Tianjin, China in the winter of 2003-2004. The particles exhibited the trimodal distribution with the major peaks occurring at 0.43-2.1 and 9.0-10.0 microm for both urban and rural sites. The concentrations of the total PAH (sum of 16 PAH compound) at rural site were generally less than those of urban site. Mean fraction of 76.5% and 63.9% of the total PAH were associated with particles of 0.43-2.1 microm at rural and urban sites, respectively. Precipitation, temperature, wind speed and direction were the important meteorological factors influencing the concentration of PAHs in rural and urban sites. The distributions of PAHs concentration with respect to particle size were similar for rural and urban samples. The PAHs concentrations at the height of 40 m were higher than both of 20 and 60 m at urban site, but the mass median diameter (MMD) of total PAH increased with the increasing height. The mid-high molecular weight (278 >or= MW >or= 202) PAHs were mainly associated with fine particles (Dp or=MW >or=178) PAHs were distributed in both of fine and coarse particle. The fraction of PAHs associated with coarse particles (Dp>2.1 microm) decreased with increasing molecular weight. The relatively consistent distribution of PAHs seemed to indicate the similar combustion source of PAHs at both of rural and urban sites. The fine differences of concentration and distribution of PAHs at different levels at urban site suggested that the different source and transportation path of particulate PAHs.     

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

Background and aim  

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.     

Partitioning and source diagnostics of polycyclic aromatic hydrocarbons in rivers in Tianjin, China

Water, suspended particulate matter (SPM), and sediment samples were collected from ten rivers in Tianjin and analyzed for 16 polycyclic aromatic hydrocarbons (PAHs), dissolved organic carbon (DOC), particulate organic carbon (POC) in SPM and total organic carbon (TOC) in sediment. The behavior and fate of PAHs influenced by these parameters were examined. Generally, organic carbon was the primary factor controlling the behavior of the 16 PAH species. Partitioning of PAHs between SPM and water phase was studied, and K(OC) for some PAH species were found to be significantly higher than the predicted values. The source of PAHs contamination was diagnosed by using PAH isomer ratios. Coal combustion was identified to be a long-term and prevailing contamination source for sediment, while sewage/wastewater source could reasonably explain a short-term PAHs contamination of SPM.     

煤矸石堆积下多环芳烃的淋溶污染特征

淋溶是使有害物质析出的主要途径之一。为查明煤矸石堆放淋溶造成的有机污染效应,对不同风化强度煤矸石进行了动态淋溶模拟实验,系统研究了煤矸石中US EPA优先控制的16种多环芳烃（PAH16）的析出规律和迁移方式。获得煤矸石中多环芳烃（PAHs）淋溶特征如下：煤矸石堆积期遭受短期降雨（500~1 600 mm）作用后,煤矸石溶出的PAH16总质量浓度达125.6~451.2 ng/L。PAH16溶出量初期较高,在一定降雨期后又达到峰值,酸雨条件下,煤矸石山淋溶出的PAH16可由线性累加转为指数快速累加的趋势。淋溶液中优势组分为萘、二氢苊、芴和菲,4种组分之和占所测PAHs总量的80%~90%。煤矸石溶出的PAHs环数分布为2环〉3环〉4环〉5环、6环。迁移方式上,2环PAHs多以溶解相迁移,3环PAHs主要以颗粒态迁移,存在少量溶解形式,而4环以上PAHs则以颗粒相形式迁移。     

The fate of the aqueous phase polycyclic aromatic hydrocarbon fraction in a detention pond system

The concentration of dissolved polycyclic aromatic hydrocarbons (PAH) in influent, effluent, and within a detention pond system was measured. The "soluble fraction" was operationally defined as the PAHs in solution that passed through a 1.2 μm filter. The results show that influent and effluent PAH concentrations were similar, indicating that dissolved PAH moved essentially unhindered through the detention pond system. In general, low molecular weight PAH were present at the highest concentrations and the highest PAH concentrations were measured in Summer. Also, year-to-year variations in PAH concentration were observed. At the end of sufficiently large storms, the pond was comparably unpolluted. During dry periods, the dissolved PAH concentration rose, possibly due to evapoconcentration and by partitioning of PAH from trapped contaminated sediment in the detention pond system. This study provides evidence that aqueous-phase PAH concentrations in runoff water were relatively unaffected by the passage through a conventional detention pond system.     

Passive samplers versus surfactant extraction for the evaluation of PAH availability in sediments with variable levels of contamination

The purpose of this study was to test the efficiency of passive solid samplers, polyoxymethylene (POM) strips and polydimethylsiloxane (PDMS) silicon tubing, to predict the bioavailability of native PAHs in contaminated sediments. Results were compared with worm bioaccumulation data and solid/liquid extraction using the surfactant Brij((R)) 700 (B700). The two passive samplers were found to act differently. The PDMS sampler overestimated the availability of PAHs in all studied sediments. The POM method provided results in accordance with those obtained with the B700 extraction. However, POM and B700 methods underestimated PAH availability in low contaminated sediments where biological factors (digestible organic matter) become important. Bioavailability of total PAHs was correctly predicted by POM and B700 in highly contaminated aluminum smelter sediments. A closer examination of individual PAH results indicated that both techniques overestimated the availability of large molecules with logK(ow)>6 suggesting a biological mechanism limiting uptake of larger PAHs which seems to be related to the molecular size of compounds.     

Distribution of polycyclic aromatic hydrocarbons in urban stormwater in Queensland, Australia

This paper reports the distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in wash-off in urban stormwater in Gold Coast, Australia. Runoff samples collected from residential, industrial and commercial sites were separated into a dissolved fraction (<0.45 μm), and three particulate fractions (0.45-75 μm, 75-150 μm and >150 μm). Patterns in the distribution of PAHs in the fractions were investigated using Principal Component Analysis. Regardless of the land use and particle size fraction characteristics, the presence of organic carbon plays a dominant role in the distribution of PAHs. The PAHs concentrations were also found to decrease with rainfall duration. Generally, the 1- and 2-year average recurrence interval rainfall events were associated with the majority of the PAHs and the wash-off was a source limiting process. In the context of stormwater quality mitigation, targeting the initial part of the rainfall event is the most effective treatment strategy. The implications of the study results for urban stormwater quality management are also discussed.