Loss Of Polycyclic Aromatic Hydrocarbons Research Articles

Insights into relationship between microbial community-induced polycyclic aromatic hydrocarbons degradation and soluble organic matter transformation during vermiculite-amended sewage sludge composting

Vermiculite is a natural clay mineral with unique properties that are widely used in plant cultivation, soil remediation, and solid waste management. This study investigated the relationship between microbial community-induced polycyclic aromatic hydrocarbons (PAHs) degradation and dissolved organic matter (DOM) transformation during vermiculite-amended composting of sewage sludge. Four treatments with varying vermiculite percent compositions, 0%, 1%, 5%, and 10%, mixed with initial mix waste, were designed and then composted for 33 days. The results showed that the addition of 1% vermiculite caused the highest losses of 82.19%, 52.98%, and 69.00% for LMW-PAHs (2-3 rings), HMW-PAHs (4-6 rings), and total PAHs respectively compared to other treatments. Spectral and community analyses revealed that 1% vermiculite enhanced the PAHs losses by functional networking of key genera and promoting the aromatization and humification of DOM to format the micelles with PAHs. The transformation and utilization of DOM driven by key genera Acinetobacter, Ochrobactrum, Pseudoxanthomonas, and Bacillus were the important impact factors for the losses of PAHs. Finally, this study provides new insights and a guide for applying vermiculite to sludge composting for PAHs removal.

Air‐Sea Gas Exchange and Its Potential Influence on the Regional Fate of Polycyclic Aromatic Hydrocarbons in the East China Marginal Sea

AbstractTo investigate the air‐sea gas exchange and its potential influence on the regional fate of polycyclic aromatic hydrocarbons (PAHs) in the East China Marginal Seas (ECMS), which consist of the East China Sea (ECS) and Yellow Sea (YS), we collected air and surface seawater samples of this area in the summer 2018 and winter 2019, respectively. Generally, PAHs underwent a strong volatilization process in the ECMS in both summer and winter. Good correlations between wind speed and the magnitude of air‐sea gas exchange were found for low molecular weight PAHs, suggesting the rate of their air‐sea gas exchange was influenced by the static stability of overlying atmosphere. However, such an influence for high molecular weight PAHs was constrained by their low Henry's law constant. Dissolved concentration of PAHs in surface seawater was another key factor regulating their air‐sea gas exchange, which not only influenced the rate of air‐sea gas exchange but also was involved in the exchange direction. Higher air‐sea gas exchange fluxes of PAHs in winter were attributed to their increasing dissolved concentrations in seawater during this season. A mass conservation analysis revealed a huge volatilization loss of PAHs from seawater to atmosphere, suggesting air‐sea gas exchange might be a key process to modulate the distribution and occurrence of PAHs in the ECS and YS. Such a loss of PAHs in seawater might be compensated by the sediment resuspension, which implied that the sedimentary deposit could serve as a secondary source of PAHs in seawater and overlying atmosphere.

The high dose of biochar reduces polycyclic aromatic hydrocarbons losses during co-composting of sewage sludge and wheat straw

The aim of the study was to investigate the effect of the biochar (BC) dose on solvent extractable (Ctot) and freely dissolved (Cfree) polycyclic aromatic hydrocarbons (PAHs) content during co-composting. A significantly better reduction of Σ16 Ctot PAHs after 98 days occurred during composting with BC (for 1% of BC – 44% and for 5% of BC – 23%) than in the control (15%). Despite the relatively high reduction of Ctot PAHs in the experiment with 5% BC rate, the content of the PAHs was still the highest compared to other variants. Regarding Cfree PAHs, 5% rate of BC resulted in the best reduction of PAHs, while the 1% BC dose resulted in a lower reduction of Cfree than the control. For 1% BC, PAHs losses was more effective, and sequestration processes played a less significant role than in the experiment with 5% dose of BC. The total and dissolved organic carbon, and ash were predominantly responsible for Ctot and Cfree losses, and additionally pH for Cfree. The results of the experiment indicate that BC performs a crucial role in composting, affecting the Ctot and Cfree PAHs in the compost but the final effect strictly depends on the BC dose.

The recalcitrance and potential toxicity of polycyclic aromatic hydrocarbons within crude oil residues in beach sediments at the BIOS site, nearly forty years later

The Arctic is a unique environment characterized by extreme conditions, including daylight patterns, sea ice cover, and some of the lowest temperatures on Earth. Such characteristics in tandem present challenges when extrapolating information from oil spill research within warmer, more temperate regions. Consequently, oil spill studies must be conducted within the Arctic to yield accurate and reliable results. Sites of the Baffin Island Oil Spill (BIOS) project (Cape Hatt, Baffin Island, Canadian Arctic) were revisited nearly 40 years after the original oil application to provide long-term monitoring data for Arctic oil spill research. Surface and subsurface sediment samples were collected from the intertidal zone of the 1981 nearshore oil spill experiment (Bay 11), from 1980 supratidal control plots (Crude Oil Point) and 1982 supratidal treatment plots (Bay 106). Samples were analyzed for Polycyclic Aromatic Hydrocarbons (PAHs) and alkylated homologues via Gas Chromatography – Mass Spectrometry (GC-MS). Our results suggest that total mean concentrations of all measured PAHs range from 0.049 to 14 mg/kg, whereas total mean concentrations of the 16 US EPA priority PAHs range from 0.02 to 2.1 mg/kg. The relative proportions of individual PAHs were compared between sampling sites and with the original technical mixture. Where available, percent loss of individual PAHs was compared with data from samples collected at the BIOS site, in 2001. All three sites featured samples where concentrations of various priority PAHs exceeded the established Interim Marine Sediment Quality Guidelines. All supratidal samples contained potentially toxic levels of PAHs. Even after nearly four decades of weathering, the recalcitrant crude oil residues remain a potential hazard for the native organisms. Continued monitoring of this unique study site is crucial for establishing a timeline for oil degradation, and to observe a reduction in toxicity over time.

Effect of carrier gas during pyrolysis on the persistence and bioavailability of polycyclic aromatic hydrocarbons in biochar-amended soil

AbstractIn this study the persistence (based on extractable, Ctot) and bioavailability (based on freely dissolved content, Cfree) of polycyclic aromatic hydrocarbons (PAHs) in biochar-amended soil was investigated. Biochar produced at 500 or 700 °C from sewage sludge (BC) or sewage sludge and willow (W) mixture (BCW) in an atmosphere of nitrogen (N2) or carbon dioxide (CO2) was evaluated. The biochars were applied to the real soil (podzolic loamy sand) at a dose of 2% (w/w). The content of Ctot and Cfree PAHs was monitored for 180 days. The biochar production conditions determined the Ctot and Cfree PAHs in the soil. A change of carrier gas from N2 to CO2 caused an increase in Ctot PAH losses in the soil from 19 to 75% for the biochar produced from SL and from 49 to 206% for the co-pyrolyzed biochar. As regards Cfree PAHs, the change from N2 to CO2 increased the losses of Cfree PAHs only for the biochar derived from SL at a temperature of 500 °C (by 21%). In the soil with the other biochars (produced at 700 °C from SL as well as at 500 and 700 °C from SL/W), the Cfree increased from 17 to 26% compared to the same biochars produced in an atmosphere of N2.

Polycyclic aromatic hydrocarbons in PM2.5 from an e-waste source site and a receptor site in Southern China: Atmospheric transport and process implications

Polycyclic aromatic hydrocarbons (PAHs) are potential contaminants released from informal electronic waste (e-waste) recycling. PAHs in PM2.5 collected at a rural e-waste (source) site and a background (receptor) site in Southern China were measured. Seasonal variations and regional transport of PAHs were investigated, and their sources and atmospheric processes were implied. The median concentrations of ∑18PAHs at the e-waste site (13.7 ng/m3) were one order of magnitude higher than those at the background site (median = 1.54 ng/m3), indicating the informal e-waste dismantling was a significant source. The seasonal variations of PAH concentrations at the two sites were similar, exhibiting noticeably unimodal distributions in winter, predominantly associated with the strengthened e-waste dismantling activities. Three molecular diagnostic ratios (MDRs) can be collectively used as potential markers of field informal e-waste burning sources. The dispersion model revealed that regional atmospheric transport from this e-waste site was a source of PAHs in the background air. Some MDRs significantly changed at the background site compared to the source site but could not be explained by the lifetime and/or gas-particle partition of the isomers. The differences complied with recent theories about the multiphase reactivity and evaporation of PAHs on aerosols. It was proposed that in warm and humid climates, the losses of PAHs from PM2.5 were dominated by their phase separation or diffusion, which was n-octanol/water partition coefficient (KOW) dependent. This hypothesis was further supported by data in the literature.

Non-equilibrium influence on G/P partitioning of PAHs: Evidence from the diurnal and nocturnal variation

Gas/particle (G/P) partitioning is an important behavior for the atmospheric transport of polycyclic aromatic hydrocarbons (PAHs). In this study, paired daytime and nighttime air samples were collected for one year in order to study the diurnal and nocturnal variations of concentration and G/P partitioning of PAHs. Higher PAHs concentrations in total phase were observed in nighttime. The geomean (GM) concentrations of Σ15PAHs in total phase were 69.6 and 52.8 ng/m3 in nighttime and daytime, respectively. More obviously diurnal and nocturnal variations were observed in non-heating season, with the GM ratios of Σ15PAHs in nighttime to daytime of 1.65 and 1.06 in non-heating season and heating season, respectively. The results could be attributed to emission sources and meteorological conditions. The values of particulate phase fraction (ϕP) and G/P partitioning quotient (log KP) were used to quantify the phase distribution of PAHs. For most high molecular weight PAHs, the values of ϕP and log KP in nighttime were higher than those in daytime, which could be mainly attributed to the lower temperature in nighttime. However, for the three light molecular weight PAHs (Acy, Ace and Flu), higher values of ϕP and log KP were observed in daytime. The regression of log KP against log KOA for the three PAHs in daytime differed from those in nighttime. The chemical losses of PAHs in different phases might be responsible for the result. These findings suggested that the chemical loss of PAHs in gas phase should be considered for the G/P partitioning process.

Orion Bar as a window to the evolution of PAHs

ABSTRACT We investigate the mid-infrared (IR) emission in the Orion Bar photodissociation region (PDR), using archival photometric and spectroscopic observations from the United Kingdom Infrared Telescope (UKIRT), Spitzer, Infrared Space Observatory(ISO), and Stratospheric Observatory for Infrared Astronomy (SOFIA) telescopes. Specifically, we consider flux densities of the emission bands at 3.3, 3.4, 3.6, 6.6, 7.7, and 11.2 $\mu$m in several locations and a spectrum from 3 to 45 $\mu$m in one location. We study the behaviour of band flux ratios, which are sensitive to external conditions, as revealed by their variations with the distance from an ionizing source. Assuming that the mid-IR emission arises mostly from polycyclic aromatic hydrocarbons (PAHs), and that a weak emission feature at 3.4 $\mu$m is related to PAHs with extra hydrogen atoms (H-PAHs), we trace variations of the ratios using a model for PAH evolution. Namely, we estimate how populations of PAHs of different sizes, hydrogenation and ionization states change across the Orion Bar over a time interval approximately equal to its lifetime. The obtained ensembles of PAHs are further used to calculate the corresponding synthetic spectra and band flux densities. The model satisfactorily describes the main features of the ratios I3.6/I11.2, I7.7/I11.2, I7.7/I3.6, and I3.3/I3.4. We conclude that the best coincidence between modelling and observations is achieved if C loss of PAHs is limited by the number of carbon atoms NC = 60, and the band at 3.4 $\mu$m may indeed be attributed to H-PAHs. We confirm that large cations dominate at the surface of the PDR but small neutral PAHs and anions are abundant deeper in the molecular cloud.

EFFECT OF BIOMASS ADDITION BEFORE SEWAGE SLUDGE PYROLYSIS ON THE PERSISTENCE AND BIOAVAILABILITY OF POLYCYCLIC AROMATIC HYDROCARBONS IN BIOCHAR-AMENDED SOIL

There is a lack of studies dealing with the effects of co-pyrolyzed biochars produced from different materials on the persistence of polycyclic aromatic hydrocarbons (PAHs). This research aimed to determine the persistence (based on extractable Ctot) and bioavailability (based on freely dissolved content, Cfree) of PAHs in soil amended with biochar derived from sewage sludge (SL) or a mixture of SL and biomass (SLW). Biochars produced at 500, 600, and 700 °C were applied to the soil (podzolic loamy sand) at a rate of 2% (w/w) and incubated for 180 days. The content and changes of PAHs differed between the experiment with SL, SL-derived biochar, and SLW-derived biochar. In the soil with the SLW-derived biochar, the losses of Ctot Σ16 PAHs were lower (between 13 and 38%) than in the soil with the SL-derived biochar (from 27 to 74%). Compared to Ctot, a completely different trend was observed for Cfree PAHs. The decrease of Cfree PAHs in the soil with the SLW-derived biochar was higher than or similar (from 4 to 18%) to the losses of Cfree PAHs in the soil with the addition of the SL-derived biochar. The differences between the individual treatments resulted from the difference in the physical and chemical properties of the biochars, which affected the persistence and bioavailability of the studied compounds.

Non-equilibrium interplay between gas–particle partitioning and multiphase chemical reactions of semi-volatile compounds: mechanistic insights and practical implications for atmospheric modeling of polycyclic aromatic hydrocarbons

Abstract. Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic air pollutants. The dispersion of PAHs in the atmosphere is influenced by gas–particle partitioning and chemical loss. These processes are closely interlinked and may occur at vastly differing timescales, which complicates their mathematical description in chemical transport models. Here, we use a kinetic model that explicitly resolves mass transport and chemical reactions in the gas and particle phases to describe and explore the dynamic and non-equilibrium interplay of gas–particle partitioning and chemical losses of PAHs on soot particles. We define the equilibration timescale τeq of gas–particle partitioning as the e-folding time for relaxation of the system to the partitioning equilibrium. We find this metric to span from seconds to hours depending on temperature, particle surface area, and the type of PAH. The equilibration time can be approximated using a time-independent equation, τeq≈1kdes+kads, which depends on the desorption rate coefficient kdes and adsorption rate coefficient kads, both of which can be calculated from experimentally accessible parameters. The model reveals two regimes in which different physical processes control the equilibration timescale: a desorption-controlled and an adsorption-controlled regime. In a case study with the PAH pyrene, we illustrate how chemical loss can perturb the equilibrium particulate fraction at typical atmospheric concentrations of O3 and OH. For the surface reaction with O3, the perturbation is significant and increases with the gas-phase concentration of O3. Conversely, perturbations are smaller for reaction with the OH radical, which reacts with pyrene on both the surface of particles and in the gas phase. Global and regional chemical transport models typically approximate gas–particle partitioning with instantaneous-equilibration approaches. We highlight scenarios in which these approximations deviate from the explicitly coupled treatment of gas–particle partitioning and chemistry presented in this study. We find that the discrepancy between solutions depends on the operator-splitting time step and the choice of time step can help to minimize the discrepancy. The findings and techniques presented in this work not only are relevant for PAHs but can also be applied to other semi-volatile substances that undergo chemical reactions and mass transport between the gas and particle phase.

Abatement of Polycyclic Aromatic Hydrocarbon Residues in Biochars by Thermal Oxidation

Biochars often contain residues of polycyclic aromatic hydrocarbons (PAHs) that can pose risks to exposed organisms and ultimately to human health. This study shows that thermal oxidation of an anoxically produced (500 °C) softwood biochar using brief post-pyrolysis thermal oxidation in air caused a substantial decline in solvent-extractable PAHs (up to 85% of Tot-PAH) and a sharp decrease (up to 82%) in the EPA Relative Potency Factor. Optimum conditions were 400 °C for 20 min. An alternative approach of including 1% O₂ in the nitrogen flow stream during pyrolysis was less effective. PAH loss is attributed to combustion processes as opposed to outgassing. Oxidation of PAHs occurs in the gas and adsorbed phases and is promoted by pore reaming of biochar micropores and mesopores during thermal oxidation, which facilitates diffusive exchange of O₂, reactive oxygen species, and PAH molecules. Oxidation also may be promoted by self-heating of the biochar body, which increases the local temperature. The results indicate that a short post-pyrolysis thermal oxidation step can reduce the risks associated with PAH residues in biochar.

Polycyclic aromatic hydrocarbons (PAHs) persistence, bioavailability and toxicity in sewage sludge- or sewage sludge-derived biochar-amended soil

Soils can be contaminated with polycyclic aromatic hydrocarbons (PAHs) when either sewage sludge (SSL) or biochar (BC) are used. There are no comparative studies regarding the effects of soil amendment with SSL or BC on the persistence, bioavailability and toxicity of PAHs. This research compared the persistence of PAHs (based on the extractable content, Ctot) and their bioavailability (freely dissolved, Cfree) as well as the toxicity (solid phase: Phytotoxkit F with Lepidium sativum and the Collembolan test with Folsomia candida; leachates: Phytotestkit F with L. sativum and Microtox® with Aliivibrio fischeri) of soil amended with SSL or with SSL-derived BCs. BCs were produced from three different sewage sludges at a temperature of 500 °C. SSLs or BCs were added to the soil at a rate of 1% (30 t/ha). Adding SSL to the soil increased more the PAH content in it than after BC application, which was associated with a higher content of PAHs in SSL. Losses of Σ16 Ctot and Cfree PAHs were higher than those observed for biochar only in the case of one SSL. In the other cases, PAH losses were either higher for biochar or did not differ significantly between SSL and BC. On the other hand, the analysis of the individual groups of PAHs showed significant differences between SSL and BC, both for Ctot and Cfree. Nonetheless, these differences were largely driven by the type of sewage sludge and biochar. Only in the case of root growth inhibition the toxicity higher was for the SSL-amended soils than for the BC-amended ones. In the other cases, varying results were observed which were determined by the type of sewage sludge/biochar, similarly to PAH losses.

Dissipation and sorption processes of polycyclic aromatic hydrocarbons (PAHs) to organic matter in soils amended by exogenous rich-carbon material

PurposeThe aim of the research was to assess the effect of biochar addition on aging, degradation, and sorption processes of polycyclic aromatic hydrocarbons (PAHs) to soil organic matter. The study was carried out as a sorption experiment in strictly controlled water and air conditions, which allowed for the accurate observation and prediction of PAH behavior in soils.Materials and methodsFour soils were fortified with a PAH mixture (Fluorene-Flu, Anthracene-Ant, Phenanthrene-Phe, Pyrene-Pyr, Chrysene-Chry) at 20 mg kg−1 of single-compound concentration level. The experiment was carried out in two trials: soils + 5PAHs amended with biochar and soil + 5PAHs without biochar addition with incubation times of 0, 1, 3, 6, and 9 months. After each interval time, the extractable (E-SOM) and stable organic matter (S-SOM) were measured as well as PAHs determined in two forms: total concentration (PAH-tot) and residual concentration (PAH-rest) after E-SOM extraction. The PAH loss and half-life times were estimated according to pseudo first-order kinetics equation.Results and discussionThe amounts of PAH-tot in the soils without biochar decreased by an average of 92%, while in soil with biochar, this was 41% after 9 months of aging. The amount of PAHs-rest bounded with S-SOM after 9 months of incubation varied from 0.9 to 3.5% and 0.2 to 1.3% of the initial PAH concentration, respectively, for soils non-induced and induced by biochar. In soils without biochar, Flu, Ant, Phe, and Pyr exhibited similar T1/2 (43–59 days), but Chry was characterized by a much higher and broader T1/2 than other hydrocarbons (67–280 days). Biochar addition to the soils significantly influenced the half-life changes for all PAHs. The highest changes were noted for Phe (14-fold increase), and the lowest was for Flu (7-fold increase).ConclusionsThe addition of exogenous-rich carbon material such as biochar to the soil significantly changes the behavior and sorption potential of PAHs in the soil. Soils enriched with biochar are characterized by a higher persistence of PAHs, longer aging time, and lower affinity for sorption by native organic matter structures. Soils freshly polluted by PAH are mainly sorbed by E-SOM, which significantly increases their accessibility and reduces formation of bound-residues in the soil.

Removal of phenanthrene and pyrene from contaminated sandy soil using hydrogen peroxide oxidation catalyzed by basic oxygen furnace slag.

Soil contamination with polycyclic aromatic hydrocarbons (PAHs) is a serious problem in Northeast China, especially in the steel industrial area. The objective of this study was to evaluate the feasibility of using basic oxygen furnace (BOF) slag to activate the Fenton-like remediation of PAH-contaminated soil to achieve the objectives of "waste control by waste" and "resource recycling" in Chinese steel industry. The effects of BOF slag dosages, H2O2 concentrations, and exothermicity-driven evaporation were evaluated with respect to the removal efficiencies of phenanthrene (Phe) and pyrene (Pyr). Results indicated that PAH oxidation was proportional to the BOF slag dosages and was increased exponentially with H2O2 concentrations. Evaporation due to increasing temperature caused by exothermic reaction played an important role in total soil PAH losses. The sequential Fenton-like oxidation with a 3-times application of 15% H2O2 and the same BOF slag repeatedly used were able to remove 65.87% of Phe and 58.33% of Pyr, respectively. Soluble iron oxides containing in BOF slag were reduced, while amorphous iron oxide concentration remained stable during the repeated Fenton-like process. Column study mimics real field applications showing high removal efficiencies of Phe (36.05-83.20%) and Pyr (21.79-68.06%) in 30-cm depth of soil profile. The tests on soluble heavy metal concentrations after the reactions with high slag dosage or high H2O2 concentration confirmed that BOF slag would not cause heavy metal contamination. Consequently, BOF slag may provide an efficient way for enhancing the Fenton-like based remediation of heavily PAH-polluted soil with little risk on collateral heavy metal contamination. However, an external gas collection and purification equipment would be essential to eliminate the evaporated PAHs.

Impacts of photochemical ageing on the half-lives and diagnostic ratio of polycyclic aromatic hydrocarbons intrinsic to PM2.5 collected from 'real-world' like combustion events of wood and rice straw burning.

The present experimental study describes the characteristics of polycyclic aromatic hydrocarbons (PAHs) emitted with PM2.5 particles during wood and rice straw burning as well as impacts of photochemical ageing on the half lives of particulate PAHs and their diagnostic ratio values. The photochemical degradation kinetics experiments were carried out by exposing the PM2.5 to light and synthetic air flow. Pseudo first order rate constants were calculated based on PAH loss as a function of exposure time. Relatively quick degradation of lighter PAHs (3-rings) [(0.2-0.5)h-1] than heavier PAHs (4-6 rings) [(0.0005-0.03)h-1] indicates substantial impact of PAH-substrate interaction through π-π stacking with the carbonaceous substrates. Moreover, our results showed distinct PAH diagnostic ratios (DR) for wood and rice straw burnings which, however, change with time due to photochemical degradation. The later may add uncertainties in the applications of DR values for source apportionment. Furthermore, considerably large half lives (100-3000 h) of the carcinogenic PAHs as estimated under ambient solar radiation may cause poor and adverse air quality in long range and therefore demands immediate regulations against uncontrolled biomass burning.

Photodegradation Rate Constants for Anthracene and Pyrene Are Similar in/on Ice and in Aqueous Solution.

Snowpacks contain a variety of chemicals, including organic pollutants such as toxic polycyclic aromatic hydrocarbons (PAHs). While PAHs undergo photodegradation in snow and ice, the rates of these reactions remain in debate. Some studies report that photochemical reactions in snow proceed at rates similar to those expected in a supercooled aqueous solution, but other studies report faster reaction rates, particularly at the air-ice interface (i.e., the quasi-liquid layer, or QLL). In addition, one study reported a surprising nonlinear dependence on photon flux. Here we examine the photodegradation of two common PAHs, anthracene and pyrene, in/on ice and in solution. For a given PAH, rate constants are similar in aqueous solution, in internal liquid-like regions of ice, and at the air-ice interface. In addition, we find the expected linear relationship between reaction rate constant and photon flux. Our results indicate that rate constants for the photochemical loss of PAHs in, and on, snow and ice are very similar to those in aqueous solution, with no enhancement at the air-ice interface.

Volatilization and oxidative artifacts of PM bound PAHs collected at low volume sampling (1): Laboratory and field evaluation

Laboratory and field studies were carried out to assess the effects of oxidative degradation and volatilization on PM10 bound polycyclic aromatic hydrocarbons (PAHs), collected at low volume condition according to the EU sampling reference method EN12341:2014 (flow rate 2.3 m3 h−1), on 47 mm quartz filters. For the laboratory experiments, pairs of twin samples were collected in field and, after treatments favoring decomposition or/and volatilization of PAHs on one sample, the PAH amount was compared with that of the corresponding untreated sample. Ozone exposure caused a general PAHs decay with more marked effects on benzo [a]pyrene, perylene and benz [a]anthracene; these compounds showed, similarly to benzo [ghi]perylene, correlations between ozone dose and losses. Treatments with zero air exhibited losses due to volatilization even for 5-ring PAHs up to benzo [a]pyrene, whereas a linear dependence was observed between filter PAH load and losses for benzo [a]anthracene, chrysene and benzofluoranthenes. Concentrations on samples collected simultaneously over 48, 24, 12 and 6 h were compared. Results confirmed a lack of temporal auto-consistency in the PAHs sampling methodology here adopted. In particular higher atmospheric PAH concentrations were ascertained on samples constituted by cumulative filters exposed over shorter sampling times. When 24–h and 2 × 12-h samples were compared, comparable losses were evaluated in the hot and cold seasons. This finding shows that, although in summer meteorology conditions favor sampling artifacts, the effectiveness of these phenomena continue in the winter, probably due to the larger amount of PAH available on the sampling filter (total PAHs ∼ 10 vs 0.5 ng m−3).

Indirect influence of eutrophication on air – water exchange fluxes, sinking fluxes, and occurrence of polycyclic aromatic hydrocarbons

How eutrophication affects biogeochemical processes of hydrophobic organic contaminants (HOCs) in aquatic environments is a pending challenge. Although the direct influence of eutrophication on biogeochemical processes of HOCs in waters has been well addressed, the indirect influence of eutrophication on biogeochemical processes of HOCs remains largely unknown. Here we take the large shallow eutrophic Lake Taihu in China and polycyclic aromatic hydrocarbons (PAHs) as examples to provide novel knowledge on the indirect influence of eutrophication on air – water exchange fluxes, sinking fluxes, and occurrence of HOCs. The air – water exchange fluxes of individual PAHs varied dramatically at different sites in all studied seasons. The sinking flux of ΣPAH16 was 14 855.3 ± 1579.9, 3548.9 ± 650.6, and 5588.4 ± 530.7 ng m−2 d−1 in spring, summer, and winter. The corresponding concentration of ΣPAH16 in surface sediments was 713.1 ± 78.6, 339.7 ± 36.6, and 293.0 ± 35.2 ng g−1 d.w. Our study for the first time suggested that recruitment of cyanobacteria from surface sediments to water column in spring reduced the concentrations of PAHs in surface sediments, but enhanced their concentrations in the bulk water column, and overwintering of cyanobacteria in winter enhanced the concentrations of PAHs in surface sediments. High pH induced indirectly by eutrophication decreased seasonal air – water exchange fluxes (enhanced net volatilization) of PAHs, reduced the aromaticity of surface sediments and the hydrophobicity of phytoplankton cell surface, and reduced the accumulation of PAHs in surface sediments and phytoplankton consequently. Sinking fluxes and daily loss of PAHs from the water column decreased with phytoplankton biomass because the fraction of organic matter sinking from the water column decreased with phytoplankton biomass. Our study provides novel complementary knowledge for the biological pump for HOCs, and has important implications for understanding the coupling between eutrophication and biogeochemical processes of HOCs in subtropical shallow eutrophic waters.

Application of the Multimedia Urban Model to estimate the emissions and environmental fate of PAHs in Tarragona County, Catalonia, Spain

The Multimedia Urban Model (MUM-Fate) was used to estimate the emissions, fate and transport of polycyclic aromatic hydrocarbons (PAHs) in Tarragona County, Catalonia, Spain, where the largest chemical/petrochemical industrial complex of Southern Europe is located. MUM-Fate is a Level III steady-state fugacity model consisting of seven bulk media compartments (lower and upper air, surface water, sediment, soil, vegetation, and an organic film that coats impervious surfaces). The model was parameterized according to environmental conditions in Tarragona County, and used to back-calculate emissions from measured air concentrations of naphthalene, anthracene, phenanthrene, fluoranthene, pyrene, and benzo[a]pyrene. Modelled results in soils were within the range reported for measured concentrations. Estimated emissions of ∑6PAH were 42ty−1, with phenanthrene having the greatest value (16ty−1). The fate and transport of ∑6PAH were subsequently estimated by running the model an illustrative emission rate of 1molh−1. Organic film on impervious surfaces was the compartment that achieved the highest concentrations of PAHs, being up to 2·108ngm−3. However, as the film conveys chemicals to surface waters, the persistence in this compartment was <1day. Soils and sediments were the greatest sinks for PAHs, with a persistence of 100–1000days. The greatest loss of PAHs was due to advection from air, followed by photodegradation from air. These results provide a first approximation of the current emissions and fate of PAHs in Tarragona County.

Determination of 16 Polycyclic Aromatic Hydrocarbons in Tea by Simultaneous Dispersive Solid-Phase Extraction and Liquid–Liquid Extraction Coupled with gas Chromatography–Tandem Mass Spectrometry

An anti-contamination method for the simultaneous determination of 16 polycyclic aromatic hydrocarbons (PAHs) in tea was developed using gas chromatography–tandem mass spectrometry. In this study, three transitions for each PAHs were monitored at multi-reaction monitoring (MRM) mode and pseudo-MRM mode to improve the reliability of the developed method. The PAHs were extracted using acetonitrile and then cleaned up by simultaneous dispersive solid-phase extraction (D-SPE) and liquid–liquid extraction (LLE). A mixture of adsorbents that contain primary–secondary amine, octadecylsilane and florisil was applied for the D-SPE cleanup. The solvent used for LLE was n-hexane with a 1:2 (v/v) ratio of acetonitrile extracts and n-hexane. Loss of PAHs occurred during sample preparation because of incomplete extraction of PAHs from the acetonitrile extracts into n-hexane with the LLE treatment. Isotopic surrogate standards were used to calibrate for the loss of PAHs during sample preparation. For the 16 PAHs, linear calibrations with coefficients R 2 ≥ 0.99 were obtained. The limits of quantifications of the 16 PAHs were <3 μg kg−1. The recovery rates of samples spiked with 10, 50 and 200 μg kg−1 of analytes varied from 77 to 116 %, with relative standard deviations of <13 %. The developed method was used to determine the PAHs in 46 tea samples.