Comparing the desorption and biodegradation of low concentrations of phenanthrene sorbed to activated carbon,biochar and compost

Carbonaceous soil amendments are applied to contaminated soils and sediments to strongly sorb hydrophobic organic contaminants (HOCs) and reduce their freely dissolved concentrations. This limits biouptake and toxicity, but also biodegradation. To investigate whether HOCs sorbed to such amendments can be degraded at all, the desorption and biodegradation of low concentrations of ¹⁴C-labelled phenanthrene (?5 μg L^?1) freshly sorbed to suspensions of the pure soil amendments activated carbon (AC), biochar (charcoal) and compost were compared. Firstly, the maximum abiotic desorption of phenanthrene from soil amendment suspensions in water, minimal salts medium (MSM) or tryptic soy broth (TSB) into a dominating silicone sink were measured. Highest fractions remained sorbed to AC (84 ± 2.3%, 87 ± 4.1%, and 53 ± 1.2% for water, MSM and TSB, respectively), followed by charcoal (35 ± 2.2%, 32 ± 1.7%, and 12 ± 0.3%, respectively) and compost (1.3 ± 0.21%, similar for all media). Secondly, the mineralization of phenanthrene sorbed to AC, charcoal and compost by Sphingomonas sp. 10-1 (DSM 12247) was determined. In contrast to the amounts desorbed, phenanthrene mineralization was similar for all the soil amendments at about 56 ± 11% of the initially applied radioactivity. Furthermore, HPLC analyses showed only minor amounts (<5%) of residual phenanthrene remaining in the suspensions, indicating almost complete biodegradation. Fitting the data to a coupled desorption and biodegradation model revealed that desorption did not limit biodegradation for any of the amendments, and that degradation could proceed due to the high numbers of bacteria and/or the production of biosurfactants or biofilms. Therefore, reduced desorption of phenanthrene from AC or charcoal did not inhibit its biodegradation, which implies that under the experimental conditions these amendments can reduce freely dissolved concentration without hindering biodegradation. In contrast, phenanthrene sorbed to compost was fully desorbed and biodegraded.     

Air–water exchange fluxes of polycyclic aromatic hydrocarbons in the tropical coast,Taiwan

Air–water exchange fluxes of polycyclic aromatic hydrocarbons (PAHs) were simultaneously measured in air and water samples from two sites on the Kenting coast, located at the southern tip of Taiwan, from January to December 2010. There was no significant difference in the total PAH (t-PAH) concentrations in both gas and dissolved phases between these two sites due to the less local input which also coincided to the low levels of t-PAH concentration; the gas and dissolved phases averaged 1.29 ± 0.59 ng m^?3 and 2.17 ± 1.19 ng L^?1 respectively. The direction and magnitude of the daily flux of PAHs were significantly influenced by wind speed and dissolved PAH concentrations. Individual PAH flux ranged from 627 ng m^?2 d^?1 volatilization of phenanthrene during the rainy season with storm–water discharges raising dissolved phase concentration, to 67 ng m^?2 d^?1 absorption of fluoranthene during high wind speed periods. Due to PAH annual fluxes through air–water exchange, Kenting seawater is a source of low molecular weight PAHs and a reservoir of high molecular weight PAHs. Estimated annual volatilization fluxes ranged from 7.3 μg m^?2 yr^?1 for pyrene to 50 μg m^?2 yr^?1 for phenanthrene and the absorption fluxes ranged from ?2.6 μg m^?2 yr^?1 for chrysene to ?3.5 μg m^?2 yr^?1 for fluoranthene.     

Mobile sources of atmospheric polycyclic aromatic hydrocarbons in a roadway tunnel

Amounts of polycyclic aromatic hydrocarbons (PAHs) and oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) in samples collected from the air, from the dust on a guardrail, and from the soils on a tunnel roadway at five sampling sites in a regular roadway tunnel were chemically analyzed in order to determine their sources. Among the 23 PAHs found in the air samples, pyrene was found in the highest concentration (43±7.2 ng/m³), followed by fluoranthene (26±4.3 ng/m³). Among 20 oxy-PAHs found in the air samples, anthraquinone was found in the greatest amount (56±3.9 ng/m³). The average concentration of the major PAHs found in the guardrail dust samples were 6.9±0.77 μg/g for pyrene, 5.5±0.76 μg/g for fluoranthene, and 2.6±0.30 μg/g for phenanthrene. The average concentration of the major oxy-PAHs found in the guardrail dust samples were 9.2±3.5 μg/g for anthraquinone and 1.4±0.50 μg/g for 2-methylanthraquinone. The average concentration of the major PAHs found in the soil samples were 1.1±0.31 μg/g for fluoranthene, 0.92±0.21 μg/g for pyrene, and 0.72±0.16 μg/g for phenanthrene. The average concentration of the major oxy-PAHs found in the soil samples were 1.2±0.88 μg/g for anthraquinone, 0.18±0.04 μg/g for 4-biphenylcarboxaldehyde, and 0.13±0.08 μg/g for 2-methylanthraquinone. The BeP ratios calculated from the results suggest that most PAHs found in the samples collected from the roadway tunnel were from automobile exhaust gases.     

Influence of a large steel complex on the spatial distribution of volatile polycyclic aromatic hydrocarbons (PAHs) determined by passive air sampling using membrane-enclosed copolymer (MECOP)

Membrane-enclosed copolymer (MECOPs) samplers containing crystalline copolymers of ethylvinylbenzene-divinylbenzene in polyethylene membranes were used to assess the influence of a steel complex on the level and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in ambient air. MECOPs were deployed at six sites in Pohang, Korea for 37 days (August 9, 2005–September 14, 2005). Fluorene, phenanthrene, anthracene, and fluoranthene were dominant PAHs with the highest contribution of phenanthrene (59%) to the total amount of vapor-phase PAHs. The spatial distribution of total PAHs in the vapor phase ranging from 76 to 1077 ng MECOP⁻¹ and air dispersion modeling suggested that the steel complex was the major PAH source in Pohang. It was revealed that the major wind directions rather than the distance from the steel complex were a significant factor affecting the levels of PAHs at the sampling sites. Finally, we tried to convert MECOP concentrations (ng MECOP⁻¹) to air concentrations (ng m⁻³) with the modified sampling rates (m³ day⁻¹). This study demonstrates again that passive air samplers are useful tools for spatially resolved and time-integrated monitoring of semivolatile organic compounds (SOCs) in ambient air.     

Influence of fuel composition on polycyclic aromatic hydrocarbon emissions from a fleet of in-service passenger cars

The composition of exhaust emissions from eight in-service passenger cars powered by liquefied petroleum gas (LPG) and unleaded petrol (ULP) were measured on a chassis dynamometer at two driving speeds (60 and 80 km h⁻¹) with the aims of evaluating their polycyclic aromatic hydrocarbon (PAH) contents and investigating the effects of the type of fuel on vehicle performance, ambient air quality and associated health risks. Naphthalene, fluorene, phenanthrene, anthracene, pyrene, chrysene, benzo(a)anthracene and benzo(b)fluoranthene were the most prominent PAHs emitted by both ULP and LPG powered cars. The total emission factors of PAHs from LPG cars were generally lower than (but statistically comparable with) those of ULP cars. Similarly, the total BAP_eq of the PAHs emitted by LPG cars were lower than those from ULP cars. Multi-criteria decision making (MCDM) methods showed that cars powered by LPG fuel performed better than those powered by ULP fuel in term of PAH levels. The implications of these observations on the advantages and disadvantages of using ULP and LPG fuels are discussed.     

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 short-chain organic acids and pH on the behaviors of pyrene in soil–water system

The effects of five short-chain organic acids (SCOAs) on the behaviors of pyrene in soil–water system were investigated. The influences of the quantity and species of organic acids, pH, and soil dissolved organic matter were considered. The results showed the presence of SCOAs inhibited the adsorption and promoted the desorption of pyrene in the following order: citric acid > oxalic acid > tartaric acid > lactic acid > acetic acid. The decreased extents of pyrene adsorption performance enhanced with increasing SCOA concentrations, while the decreasing rate became less pronounced at high SCOA concentrations. In the presence of organic acids, the adsorption ability of pyrene decreased with increasing pH. However, there was a slight increase of pyrene adsorption with the addition of oxalic acid, tartaric acid and citric acid above pH 8. The capacity for pyrene retention differentiated significantly between the soils with and without dissolved organic matter. The presence of SCOAs was also favorable for the decrease of pyrene adsorption on soil without dissolved organic matter. The results of this study have important implications for the remediation of persistent organic pollutants in soil and groundwater.     

Dissolved black carbon in grassland streams: Is there an effect of recent fire history?

While the existence of black carbon as part of dissolved organic matter (DOM) has been confirmed, quantitative determinations of dissolved black carbon (DBC) in freshwater ecosystem and information on factors controlling its concentration are scarce. In this study, stream surface water samples from a series of watersheds subject to different burn frequencies in Konza Prairie (Kansas, USA) were collected in order to determine if recent fire history has a noticeable effect on DBC concentration. The DBC levels detected ranged from 0.04 to 0.11 mg L^?1, accounting for ca. 3.32 ± 0.51% of dissolved organic carbon (DOC). No correlation was found between DBC concentration and neither fire frequency nor time since last burn. We suggest that limited DBC flux is related to high burning efficiency, possibly greater export during periods of high discharge and/or the continuous export of DBC over long time scales. A linear correlation between DOC and DBC concentrations was observed, suggesting the export mechanisms determining DOC and DBC concentrations are likely coupled. The potential influence of fire history was less than the influence of other factors controlling the DOC and DBC dynamics in this ecosystem. Assuming similar conditions and processes apply in grasslands elsewhere, extrapolation to a global scale would suggest a global grasslands flux of DBC on the order of 0.14 Mt carbon year^?1.     

Atmospheric polycyclic aromatic hydrocarbons observed over the North Pacific Ocean and the Arctic area: Spatial distribution and source identification

During the 2003 Chinese Arctic Research Expedition from the Bohai Sea to the high Arctic (37–80°N) aboard the icebreaker Xuelong (Snow Dragon), air samples were collected using a modified high-volume sampler that pulls air through a quartz filter and a polyurethane foam plug (PUF). These filters and PUFs were analyzed for particulate phase and gas phase polycyclic aromatic hydrocarbons (PAHs), respectively, in the North Pacific Ocean and adjacent Arctic region. The ∑PAHs (where ∑=15 compounds) ranged from undetectable level to 4380 pg m⁻³ in the particulate phase and 928–92 600 pg m⁻³ in the gas phase, respectively. A decreasing latitudinal trend was observed for gas-phase PAHs, probably resulting from temperature effects, dilution and decomposition processes; particulate-phase PAHs, however, showed poor latitudinal trends, because the effects of temperature, dilution and photochemistry played different roles in different regions from middle-latitude source areas to the high latitudes. The ratios of PAH isomer pairs, either conservative or sensitive to degradation during long-range transport, were employed to interpret sources and chemical aging of PAHs in ocean air. In this present study the fluoranthene/pyrene and indeno[123-cd]pyrene/benzo[ghi]pyrene isomer pairs, whose ratios are conservative to photo-degradation, implies that biomass or coal burning might be the major sources of PAHs observed over the North Pacific Ocean and the Arctic region in the summer. The isomer ratios of 1,7/(1,7+2,6)-DMP (dimethylphenanthrene) and anthracene/phenanthrene, which are sensitive to aging of air masses, not only imply chemical evolving of PAHs over the North Pacific Ocean were different from those over the Arctic, but reveal that PAHs over the Arctic were mainly related to coal burning, and biomass burning might have a larger contribution to the PAHs over the North pacific ocean.     

Dissolved organic carbon in rainwater: Glassware decontamination and sample preservation and volatile organic carbon

The efficiency of different methods for the decontamination of glassware used for the analysis of dissolved organic carbon (DOC) was tested using reported procedures as well as new ones proposed in this work. A Fenton solution bath (1.0 mmol L⁻¹ Fe²⁺ and 100 mmol L⁻¹ H₂O₂) for 1 h or for 30 min employing UV irradiation showed to combine simplicity, low cost and high efficiency. Using the optimized cleaning procedure, the DOC for stored UV-irradiated ultra-pure water reached concentrations below the limit of detection (0.19 μmol C L⁻¹). Filtered (0.7 μm) rain samples maintained the DOC integrity for at least 7 days when stored at 4 °C. The volatile organic carbon (VOC) fraction in the rain samples collected at two sites in São Paulo state (Brazil) ranged from 0% to 56% of their total DOC content. Although these high-VOC concentrations may be derived from the large use of ethanol fuel in Brazil, our results showed that when using the high-temperature catalytic oxidation technique, it is essential to measure DOC rather than non-purgeble organic carbon to estimate organic carbon, since rainwater composition can be quite variable, both geographically and temporally.     

Processes driving the short-term variability of polycyclic aromatic hydrocarbons in the Baltimore and northern Chesapeake Bay atmosphere,USA

Polycyclic aromatic hydrocarbons (PAHs) were measured in the Baltimore and adjacent Chesapeake Bay in July 1997. Time series of 4- and 12-h samples were taken at two sites 15 km apart in order to evaluate the influence of a number of processes on the short-term variability of PAH in the Baltimore and northern Chesapeake Bay atmospheres. PAH concentrations were 2–3-fold higher in the Baltimore atmosphere than in the adjacent Chesapeake Bay atmosphere. For example, gas-phase phenanthrene and pyrene concentrations were 12.5 and 2.14 ng m⁻³ in the Baltimore site and 5.57 and 0.548 ng m⁻³ in the Chesapeake Bay, respectively. The influence of wind direction, wind speed and temperature was evaluated by multiple linear regressions which indicated that atmospheric gas-phase PAH concentrations over the Chesapeake Bay were significantly higher when the air mass was from the urban/industrial Baltimore area. Furthermore, the increase of gas-phase low-MW PAH concentrations with temperature and wind speed suggests that volatilization from the bay is an important source of pollutants to the atmosphere, at least when air masses are not influenced by the Baltimore urban and industrial area. Indeed, while on the long-term, the Chesapeake Bay is a receptor of atmospherically deposited PAHs, on the short-term and during appropriate meteorological conditions, the bay acts as a source of pollutants to the atmosphere. Aerosol-phase PAH concentrations and temporal trends showed a strong dependence on aerosol soot content due to the high affinity of PAHs to the graphitic structure of soot. These results confirm the important influence of urban areas as a source of pollution to adjacent aquatic environments and as a driving factor of the short-term variability, either directly by transport of urban-generated pollutants or by volatilization of previously deposited pollutants. Conversely, the complex diurnal trends of gas-phase PAHs at the Baltimore site suggests that degradation processes dominate the diurnal trends of PAHs in urban atmospheres. This conclusion is supported by estimated rate constants for PAH reaction with OH radicals which show good agreement with reported values within a factor of two.     

Distribution characteristics of polycyclic aromatic hydrocarbons with particle size in urban aerosols at the roadside in Ho Chi Minh City,Vietnam

The purpose of this study was to characterize size distributions of atmospheric polycyclic aromatic hydrocarbons (PAHs) with 4–6 rings at the roadside in Ho Chi Minh City, Vietnam. Ten PAHs (fluoranthene, pyrene, triphenylene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghi]perylene and indeno[1,2,3-cd]pyrene) in atmospheric particulate matters (PM) at the roadside were measured in the dry and rainy seasons in 2005 at Ho Chi Minh City, using a low-pressure cascade impactor. The PM were separated into nine fractions by their aerodynamic diameter, i.e. >9.0, 9.0–5.8, 5.8–4.7, 4.7–3.3, 3.3–2.1, 2.1–1.1, 1.1–0.7, 0.7–0.4 and <0.4 μm (a final filter). PAHs were analyzed by high-performance liquid chromatography with fluorescence detection. Total PAHs measured were higher in the rainy season than in the dry season. The mass of coarse particles occupied a higher fraction than that of fine particles in both seasons. Total PAHs were mainly concentrated in particles with aerodynamic diameter smaller than 0.4 μm. The particle size distributions of PAHs investigated were bi-modal with a peak in fine particle mode (<2.1 μm) and another peak in coarse particle mode (>2.1 μm). Generally, 5,6-ring PAHs associated mainly with fine particles and 4-ring PAHs spread out in both fine and coarse particles.     

Influence of water quality parameters on occurrence of polybrominated diphenyl ether in sediment and sediment to biota accumulation

Polybrominated diphenyl ether (PBDE) concentrations in sediment and fish from 12 principal rivers in Taiwan were investigated to determine their association with water quality parameters as well as the biota-sediment accumulation factor (BSAF) in fish with different living patterns. The highest PBDE concentration in sediment was found in the Bajhang River (261 ng g^?1 dry weight (d.w.)) and the lowest in the Beinan River and the Da-an River (0.17 ng g^?1 d.w.). The PBDE concentrations in fish samples ranged from 1.28 ng g^?1 d.w. (Oreochromis niloticus niloticus) in the Yanshuei River to 33.7 ng g^?1 d.w. (Varico rhinos barbatulus) in the Da-an River. We conclude that PBDEs contamination in sediment was significantly affected by NH₃–N, pH, and DO. The BSAF results showed a parabolic trend from low- to high-brominated BDEs. Fish easily accumulated the congeners BDE-47, -100, -119, -126, and -154 from sediment. The BSAF decreased in the following order: PeBDE > HxBDE > TeBDE > other BDEs. Principle component analysis showed that demersal fish have different PBDE sources than do pelagic fish. We conclude that living and feeding habits are critical factors affecting PBDE accumulation in fish.     

Emission of polycyclic aromatic hydrocarbons from gasohol and ethanol vehicles

The exhaust emission of the polycyclic aromatic hydrocarbons (PAHs) considered toxic to human health were investigated on two spark ignition light duty vehicles, one being gasohol (Gasohol, in Brazil, is the generic denomination for mixtures of pure gasoline plus 20–25% of anhydrous ethyl alcohol fuel (AEAF).)-fuelled and the other a flexible-fuel vehicle fuelled with hydrated ethanol. The influence of fuel type and quality, aged lubricant oil type and use of fuel additives on the formation of these compounds was tested using standardized tests identical to US FTP-75 cycle. PAH sampling and chemical analysis followed the basic recommendations of method TO-13 (United States. Environmental Protection Agency, 1999. Compendium Method TO-13A – Determination of polycyclic Aromatic hydrocarbons (PAH) in Ambient Air Using Gas Chromatography/Mass Spectrometry (CG/MS). Center for environmental research information, Cincinnati, p. 78), with the necessary modification for this particular application.Results showed that the total PAH emission factor varied from 41.9 μg km^?1 to 612 μg km^?1 in the gasohol vehicle, and from 11.7 μg km^?1 to 27.4 μg km^?1 in the ethanol-fuelled vehicle, a significant difference in favor of the ethanol vehicle. Generally, emission of light molecular weight PAHs was predominant, while high molecular weights PAHs were not detected. In terms of benzo(a)pyrene toxicity equivalence, emission factors varied from 0.00984 μg TEQ km^?1 to 4.61 μg TEQ km^?1 for the gasohol vehicle and from 0.0117 μg TEQ km^?1 to 0.0218 μg TEQ km^?1 in the ethanol vehicle.For the gasohol vehicle, results showed that the use of fuel additive causes a significant increase in the emission of naphthalene and phenanthrene at a confidence level of 90% or higher; the use of rubber solvent on gasohol showed a reduction in the emission of naphthalene and phenanthrene at the same confidence level; the use of synthetic oil instead of mineral oil also contributed significantly to a decrease in the emission of naphthalene and fluorene. In relation to the ethanol vehicle, the same factors were tested and showed no statistically significant influence on PAH emission.     

Seasonal variability of formaldehyde production from photolysis of rainwater dissolved organic carbon

Photochemical production of formaldehyde (HCHO) was measured in rainwater from 13 precipitation events in Wilmington, North Carolina, USA under conditions of simulated sunlight. HCHO concentrations increased in all samples irradiated with no changes observed in dark controls. HCHO photoproduction rates were strongly correlated with dissolved organic carbon (DOC) suggesting HCHO was derived from direct or indirect photolysis of rainwater DOC. The higher photoproduction rates (0.03–2.9 μM h^?1) relative to those reported for surface waters suggests that rainwater DOC is more photolabile in terms of HCHO production than surface waters. HCHO photoproduction rates were higher in growing season (1.0 ± 1.0 μM h^?1) compared to non-growing season (0.08 ± 0.05 μM h^?1) even when rates were normalized for DOC (6.8 ± 3.6 μM h^?1 mM C^?1 versus 1.8 ± 1.0 μM h^?1 mM C^?1). The higher growing season rate may be related to seasonal differences in the composition of DOC as evidenced by differences in fluorescence per unit carbon of rainwater samples. Irradiation of C18 extracts of rainwater also produced HCHO, but at lower rates compared to corresponding whole rain samples, suggesting that hydrophyllic components of rainwater play a role in HCHO photoproduction. Our results indicate that photolysis of rainwater DOC produces significant amounts of HCHO, and possibly other low molecular weight organic compounds, likely increasing its reactivity and bioavailability.     

Global atmospheric emission inventory of polycyclic aromatic hydrocarbons (PAHs) for 2004

The global atmospheric emissions of the 16 polycyclic aromatic hydrocarbons (PAHs) listed as the US EPA priority pollutants were estimated using reported emission activity and emission factor data for the reference year 2004. A database for emission factors was compiled, and their geometric means and frequency distributions applied for emission calculation and uncertainty analysis, respectively. The results for 37 countries were compared with other PAH emission inventories. It was estimated that the total global atmospheric emission of these 16 PAHs in 2004 was 520 giga grams per year (Gg y^?1) with biofuel (56.7%), wildfire (17.0%) and consumer product usage (6.9%) as the major sources, and China (114 Gg y^?1), India (90 Gg y^?1) and United States (32 Gg y^?1) were the top three countries with the highest PAH emissions. The PAH sources in the individual countries varied remarkably. For example, biofuel burning was the dominant PAH source in India, wildfire emissions were the dominant PAH source in Brazil, while consumer products were the major PAH emission source in the United States. In China, in addition to biomass combustion, coke ovens were a significant source of PAHs. Globally, benzo(a)pyrene accounted for 0.05% to 2.08% of the total PAH emission, with developing countries accounting for the higher percentages. The PAH emission density varied dramatically from 0.0013 kg km^?2 y in the Falkland Islands to 360 kg km^?2 y in Singapore with a global mean value of 3.98 kg km^?2 y. The atmospheric emission of PAHs was positively correlated to the country's gross domestic product and negatively correlated with average income. Finally, a linear bivariate regression model was developed to explain the global PAH emission data.     

Modelling the behaviour of PAHs during atmospheric transport from the UK to the Arctic

Persistent organic pollutants (POPs) such as PAHs are subject to long-range atmospheric transport, which can result in the contamination of remote areas such as the Arctic. A simple model was developed to describe the removal processes of four PAHs; fluorene (FLU), phenanthrene (PHEN), fluoranthene (FLA) and benzo[a]pyrene (B[a]P) transported over a 5 day period from a source area over the UK to the Russian Arctic. The purpose of this model was to study processes affecting the PAHs within the atmosphere, rather than their interaction with the earth's surface. The components to the model included gas/particle partitioning, reaction with OH radicals and dry and wet deposition (both rain and snow). Atmospheric/meteorological parameters for the geographical region of interest were generated from three-dimensional atmospheric models. Air concentrations were prescribed in the source area with no additional PAH inputs along the transect, both winter and summer scenarios were modelled. Reaction with OH was a major removal mechanism for gas-phase FLU, PHEN and FLA, most notably in the temperate atmosphere. Wet deposition in the form of snow accounted for the majority of PAH loss in the winter, although the gas and particle scavenging ratios used in this model ranged over several orders of magnitude. Using a 5 day transport scenario in a `1-hop’ event, the model predicted that a primary emission of FLA and B[a]P to the atmosphere of the southern UK, would not reach the Russian Arctic at a distance of ∼3500 km, assuming a constant windspeed of 10 m s⁻¹. However, both FLU and PHEN with calculated half-lives of >60 h during the winter could be transported to this area under this scenario.     

Relating dissolved organic matter fluorescence and functional properties

The fluorescence excitation–emission matrix properties of 25 dissolved organic matter samples from three rivers and one lake are analysed. All sites are sampled in duplicate, and the 25 samples include ten taken from the lake site, and nine from one of the rivers, to cover variations in dissolved organic matter composition due to season and river flow. Fluorescence properties are compared to the functional properties of the dissolved organic matter; the functional assays provide quantitative information on photochemical fading, buffering capacity, copper binding, benzo[a]pyrene binding, hydrophilicity and adsorption to alumina. Optical (absorbance and fluorescence) characterization of the dissolved organic matter samples demonstrates that (1) peak C (excitation 300–350 nm; emission 400–460 nm) fluorescence emission wavelength; (2) the ratio of peak T (excitation 220–235 nm; emission 330–370 nm) to peak C fluorescence intensity; and (3) the peak C fluorescence intensity: absorbance at 340 nm ratio have strong correlations with many of the functional assays. Strongest correlations are with benzo[a]pyrene binding, alumina adsorption, hydrophilicity and buffering capacity, and in many cases linear regression equations with a correlation coefficient >0.8 are obtained. These optical properties are independent of freshwater dissolved organic carbon concentration (for concentrations <10 mg L⁻¹) and therefore hold the potential for laboratory, field and on-line monitoring and prediction of organic matter functional properties.     

Hexabromocyclododecanes in surface sediments and a sediment core from Rivers and Harbor in the northern Chinese city of Tianjin

In the present study, hexabromocyclododecanes (HBCDs) were investigated in the sediment from Haihe River (HR), Dagu Dainage Canal (DDC) and Tianjin Harbor (TH) at Bohai Bay using a total of 51 samples of surface sediments and a sediment core collected from May to September in 2010, and its diastereomer- and enantiomer-specific profiles were analyzed. The concentration of total HBCDs were generally high, with mean value and ranges of 31.0 and 1.35–634 ng g^?1 dw, respectively. The contamination followed the order of TH > DDC > HR. Higher levels (up to 634 ng g^?1 dw) occurred in the lower reach of HR and DDC located in an industrial area of Tianjin. This is the first time to report so high concentration of HBCDs in sediment in Southeast Asia. The γ-diastereomer dominated in most samples (44 out of 51), and this is in agreement with the diastereomer distribution pattern in industrial products, while α-HBCD was the dominant diastereomer in the other seven samples. However, only few samples exhibited γ-diastereomer ratio similar to that (75–89%) in technical products, indicating the inter-transformation and variable degradation of the different isomers. The high ratio of γ-diastereomer could be used as an indicator for fresh contamination input. Enantiomeric factors (EFs) of HBCD isomers in most of the samples were statistically different from technical products (p < 0.05), showing a trend of more easily enrichment of the (?)-HBCD-enantiomer compared to the (+)-HBCD-enantiomer. The δ- and ε-diastereomers were frequently detected but at low level. The HBCDs in the sediment core showed several peaks, and the greatest value occurred in 2005, when a plastic manufacture plant using HBCD was set up nearby.