Bioavailability Of PAHs Research Articles

Does higher ratio of wheat straw addition decrease PAHs degradation in PAHs-contaminated paddy soils and PAHs concentrations in rice?

There are considerable studies focusing on impacts of straw returning on PAHs degradation and bioavailability in PAHs-contaminated upland soils, while similar research in paddy soils is limited. Incubation experiments and pot trials were conducted to study effects of straw returning on PAHs degradation in paddy soils and PAHs accumulation in rice, respectively. There are threshold effects of straw returning on PAHs degradation in PAHs-contaminated paddy soils. The inflection point of PAHs degrading was recorded under 0.8 % wheat straw treatment (conventional (CS) and pretreated wheat straw (PS)), which increased PAHs degradation by 18.13–32.36 %. The lowest PAHs concentrations in rice were recorded under 1 % straw (CS and PS) treatment, which was attributed to the highest PAHs degradation in rhizosphere soils. Compared to CS treatment, PS treatment significantly (p < 0.05) increased PAHs degradation by 7.93–10.28 % and PAHs concentrations in rice by 12.38–45.87 % due to that increasing dissolved organic carbon (DOC) enhanced PAHs concentrations in porewater of rhizosphere soils. Higher diversity enhanced the metabolic pathways and function genes to degrade PAHs by improving bacterial phenotypes and biochemical processes under 1 % wheat straw and PS treatment. The present study firstly demonstrated that the effects of straw returning on PAHs degradation in PAHs-contaminated paddy soils and PAHs concentrations in rice depended on amount and methods of straw returning.

Bioremediation of polycyclic aromatic hydrocarbons: An updated microbiological review

A class of organic priority pollutants known as PAHs is of critical public health and environmental concern due to its carcinogenic properties as well as its genotoxic, mutagenic, and cytotoxic properties. Research to eliminate PAHs from the environment has increased significantly due to awareness about their negative effects on the environment and human health. Various environmental factors, including nutrients, microorganisms present and their abundance, and the nature and chemical properties of the PAH affect the biodegradation of PAHs. A large spectrum of bacteria, fungi, and algae have ability to degrade PAHs with the biodegradation capacity of bacteria and fungi receiving the most attention. A considerable amount of research has been conducted in the last few decades on analyzing microbial communities for their genomic organization, enzymatic and biochemical properties capable of degrading PAH. While it is true that PAH degrading microorganisms offer potential for recovering damaged ecosystems in a cost-efficient way, new advances are needed to make these microbes more robust and successful at eliminating toxic chemicals. By optimizing some factors like adsorption, bioavailability and mass transfer of PAHs, microorganisms in their natural habitat could be greatly improved to biodegrade PAHs. This review aims to comprehensively discuss the latest findings and address the current wealth of knowledge in the microbial bioremediation of PAHs. Additionally, recent breakthroughs in PAH degradation are discussed in order to facilitate a broader understanding of the bioremediation of PAHs in the environment.

Influence mechanism of organic matter and low-molecular-weight organic acids on the interaction between minerals and PAHs

Investigate the effect of soil organic matter (SOM) and low molecular weight organic acids (LMWOAs) on minerals adsorption of PAHs. Batch adsorption experiments have been carried out to study the adsorption of PAHs (Naphthalene (NaP), Phenanthrene (Phe) and Pyrene (Pyr)) by minerals (Montmorillonite (Mnt), kaolinite (Kln) and calcite (Cal)). This research found that compared with Kln and Cal, Mnt showed the maximum adsorption capability for PAHs. And the order of PAHs adsorption by Mnt was: Pyr > Phe > Nap, which corresponds to the octanol-water partition coefficient (Kow) of different PAHs. The adsorption kinetic and isotherm were well fitted by Pseudo-second-order kinetic model, Freundlich and Linear isotherm model. Furthermore, inorganic ions (Ca2+) impacted PAHs adsorption by competitive adsorption and cation-π interactive. Cal has the maximum desorption of PAHs among three minerals, and there was desorption hysteresis phenomenon. Field emission-scanning electron microscope (Fe-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analysis indicated that SOM enhanced the sorption of PAHs by van der Waals, hydrogen bonding, π-π interactions, and chemical bonding. LMWOAs significantly inhibited PAHs adsorption and promote PAHs desorption from the minerals. As a result, LMWOAs increased of PAHs bioavailability, which provide a new strategy to improve PAHs cleanup efficiency.

Exploring the PAHs dissipation and indigenous bacteria response in soil amended with two different microbial inoculants

This study investigated the bioremediation of PAHs in soil by two different microbial inoculants prepared with Paracoccus aminovorans HPD-2 and the carrier humic acid (HA) or montmorillonite (Mont). After incubation for 42 d, the greatest removal of PAHs, 42.8 % or 41.6 %, was observed in microcosms with 0.2 % HA inoculant or 2 % Mont inoculant. The PAH removal efficiency in these treatments was significantly greater than that in soil amended only with planktonic HPD-2. Bacterial community analysis showed that the survival of Paracoccus aminovorans was enhanced in the treatments with Mont inoculant compared with the treatments with HA inoculant or with HPD-2 alone. Moreover, the diversity of PAH-degrading bacterial genera was greater in the treatments containing Mont inoculant than in the treatments containing HA inoculant. These results indicate that the organic material HA and inorganic material Mont promote PAH removal in different ways. Specifically, HA promotes PAHs bioavailability to accelerate the degradation of PAHs in soil, whereas Mont protects PAH-degrading microorganisms to promote pollutant removal. Overall, the findings suggest that HA and Mont are promising materials for microbial immobilization for the bioremediation of PAH-contaminated soil.

Modelling polycyclic aromatic hydrocarbon bioavailability in historically contaminated soils with six in-vitro chemical extractions and three earthworm ecotypes

Accurate prediction of organic contaminant bioavailability for risk assessment in ecological applications is hindered by limited validation on relevant bioassay species. Here, six in-vitro chemical extraction methods (butanol, non-buffered and buffered hydroxypropyl-β-cyclodextrin (HPCD, Buf-HPCD), Tenax, potassium persulfate oxidation, polyoxymethylene solid phase extraction (POM)) were tested for PAH bioaccumulation prediction in three earthworm ecotypes with dissimilar exposures, Amynthas sp., Eisenia fetida, and Lumbricus terrestris, in historically contaminated soils from manufactured gas plant (MGP) sites. Extractions were compared directly and modelled in a calculation approach using equilibrium partitioning theory (EqPT) with a novel combination of different organic carbon/octanol-water partitioning parameters (KOC and KOW). In the direct comparison approach Buf-HPCD showed the closest prediction of accumulation for burrowing Amynthas sp. and L. terrestris (within 1.5 and 3.1, respectively), but Tenax and POM showed the closest approximation for E. fetida (within 1.1 and 0.9, respectively). The optimum method for predicting PAH bioaccumulation in the calculation approach depended on earthworm species and the partitioning parameters used in equations of the four models, but overall POM, which was independent of KOC, showed the closest approximation of accumulation, within a factor of 2.5 across all species. This work effectively identifies the optimum in-vitro based approaches for PAH bioavailability prediction in earthworms as a model soil health indicator for ecological risk assessment within regulatory and remediation decision frameworks.

Interfacial biodegradation of phenanthrene in bacteria-carboxymethyl cellulose-stabilized Pickering emulsions

The limited bioavailability of PAHs in non-aqueous phase liquid (NAPL) limits their degradation. The biodegradation of phenanthrene in n-tetradecane by hydrophilic bacterium Moraxella sp. CFP312 was studied with the assistance of two polymers, chitosan and carboxymethyl cellulose (CMC). Both chitosan and CMC improved the cell hydrophobicity of CFP312 and increased the contact angle of CFP312 cells from 30.4 to 78.5 and 88.5, respectively. However, CMC increased the degradation ratio of phenanthrene from 45 to nearly 100%, while chitosan did not cause any improvement. We found that CMC was more effective than chitosan in promoting CFP312 to stabilize Pickering emulsion. In the bacteria-CMC complex system, oil was dispersed into small droplets to obtain a high emulsification index and large specific surface area. Moreover, according to the microscopic image of the bacteria-CMC emulsion droplet, we observed that the droplet surface was tightly covered by the CFP312 cells. Therefore, CFP312 cells joined with CMC can utilize phenanthrene in oil phase at the oil-water interface. This study will offer a new strategy for effective microbial degradation of hydrophobic compounds in NAPLs by hydrophilic bacteria. KEY POINTS: • Biodegradation of phenanthrene in Pickering emulsions • Pickering emulsions stabilized by hydrophilic CFP312 joined with CMC. • Phenanthrene was degraded by CFP312 at oil-water interface.

Chemotaxis to Local Chemical Gradients Enhanced Bacteria Dispersion and Bioavailability of PAH in a Heterogenous Porous Medium

Chemotaxis to Local Chemical Gradients Enhanced Bacteria Dispersion and Bioavailability of PAH in a Heterogenous Porous Medium

Characterization of PAHs contamination from unconventional bitumen derived synthetic crude oil in soil microcosms: composition, ecotoxicity and loss rate

The increasing exploitation of the unconventional bitumen-derived oils from Alberta (Canada) have raised new environmental concerns because they are inherently different than conventional oils. Previous studies mainly focused on diluted bitumen, but the Synthetic Crude Oil (SCO) which takes 35% of market share (of bitumen oils) has not been well studied. The main purpose of this study was to characterize PAHs in the SCO, since they are usually high-risk contaminants that often being prioritized in environmental monitoring practices. The obtained PAHs profile of SCO was also compared to that from a common benchmark oil, the Texas intermediate crude. PAH composition and eco-toxicity (based on Escherichia coli, Eisenia andrei and Lactuca sativa) were studied by spiking the oil in soil microcosms. Results showed a sharp difference in relative abundance of PAH between SCO spiked soil (SCO-soil) and Texas-soil. SCO-soil were characterized by a significantly higher fraction of heavy PAHs (with 3- to 6-rings), 85% versus 36% of relative abundance in Texas-soil. The two soils were also characterized by contrasted PAH-loss rates (82% for SCO-soil and 93% for Texas-soil) likely resulting from their contrasted composition. As for the eco-toxicity, SCO had generally lower toxicity of than Texas. This could attribute to the lower total PAHs concentration and the lower bioavailability of heavy PAHs more abundant in SCO than Texas. This study also suggests that evaluations of oil contamination in soil using selected regulated PAHs would be incomplete and biased for SCO that contains a large fraction of unregulated alkylated PAHs.

Assessment of polycyclic aromatic hydrocarbons in three environmental components from a tropical estuary in Northeast Brazil

The evaluation of occurrence, risk quotient (RQ), bioaccumulation factor (BAF), and sources of PAH was conducted in Sergipe-Poxim estuarine system. PAH distribution that ranged from 7.1 to 30.9 ng L−1 (surface water, SW), 5.4 to 19.5 ng g−1 (sediment, S), and 4.3 to 18.1 ng g−1 (oyster, O), characterized the environment with low contamination; 2-3 (SW), 5-6 (S), and 4 (O) PAH rings accounted for 54.5%, 68.7%, and 87.7%, respectively, along with naphthalene (SW), dibenzo(a,h)anthracene (S), and pyrene (O) as the prevailing compounds. PCA suggested the predominance of particular groups related to SW (LMW-PAH), S (HMW-PAH), and O (pyrene and fluoranthene). Furthermore, one sample of O presented a high PAH bioavailability as shown through the BAF, with emphasis on pyrene (BAF = 26.8). The RQ showed a low to moderate range in SW and S; hence, in-depth information about the possible toxic effect in organisms of this region is required.

Rhizosphere interactions between PAH-degrading bacteria and Pteris vittata L. on arsenic and phenanthrene dynamics and transformation

The pot experiment was conducted to monitor the dynamics in soil solution chemistry in order to determine the main rhizosphere processes determining As and PAH bioavailability when utilizing P. vittata and PAH-degrading bacteria to remediate co-contaminated soils. The result showed that P. vittata was capable of depleting soil solution As and increasing phenanthrene solubilization, and thus facilitating plant As uptake and phenanthrene dissipation. Bacterial inoculation enhanced soil phenanthrene dissipation and concurrently modified As bioavailability though increasing soil pH, facilitating Fe and Ca minerals solubilization, and accelerating organic matter decomposition. However, the main factors that determine As bioavailability in the rhizosphere considerably varied with plant genotypes. Upon bacterial inoculation, P and Fe strongly influenced As(V) availability and its uptake by the Guangxi accession, and DOC, Fe, and pH were the main parameters correlated with As(V) availability in the rhizosphere of the Hunan accession. Bacterial inoculation tended to stimulate As(V) reduction in the rhizosphere of P. vittata. Microbial-induced changes in Ca, S, and C cycling and pH were indicators of As(V) reduction. Although bacterial inoculation increased soil As and phenanthrene availability, striking differences in As and nutrients uptake and phenanthrene dissipation were observed between P. vittata genotypes. It is suggested that apart from the microbial transformation, plant genotypes and bacterial mediated plant nutrition are also the critical factors in controlling the fates of As and phenanthrene. Our results uncovered the interactions between P. vittata and PAH-degrading bacteria on rhizosphere properties and nutrients cycling regulating As and PAH availability and remediation efficiency.

Combined application of rhamnolipid and agricultural wastes enhances PAHs degradation via increasing their bioavailability and changing microbial community in contaminated soil

Either biosurfactants or agricultural wastes were frequently used to enhance degradation of PAHs in soil, but there is still not clear whether combined application of biosurfactants and agricultural wastes is more efficient. Rhamnolipid and/or agricultural wastes (mushroom substrate or maize straw) were mixed with PAHs-contaminated soil to explore their performances in the removal of PAHs. The present study showed that rhamnolipid combined with mushroom substrate (MR, 30.36%) or maize straw (YR, 30.76%) significantly enhanced the degradation of soil PAHs compared with single application of mushroom substrate (M, 25.53%) or maize straw (Y, 25.77%) or no addition (19.38%). The addition of agricultural wastes significantly (p < 0.001) enhanced concentration of dissolved organic carbon (DOC) in soil. The combined application obviously improved the bioavailability of PAHs in soils and exhibited synergistic effects on concentration of organic acid-soluble HMW PAHs and the degradation rate of total HMW PAHs. Meanwhile, the combined application significantly (p < 0.01) enhanced the abundance of dominant bacterial and fungal genera being connected with PAHs degradation. The removal rate of PAHs was positively correlated with the dominant genera of bacteria (r = 0.539–0.886, p < 0.05) and fungi (r = 0.526–0.867, p < 0.05) related to PAHs degradation. Overall, the combined application exhibited a better performance in the removal of PAHs in contaminated soil via increasing their bioavailability and changing microbial communities in soil.

Advancing prediction of polycyclic aromatic hydrocarbon bioaccumulation in plants for historically contaminated soils using Lolium multiflorum and simple chemical in-vitro methodologies

This study compared chemical extraction methods for the prediction of PAH bioaccumulation in ryegrass (Lolium multiflorum) roots in four Manufactured Gas Plant (MGP) historically (>50 years) contaminated soils. The in-vitro methods compared were butanol (BuOH), non-buffered and buffered 2-hydroxypropyl-β-cyclodextrin extractions (HPCD, Buf-HPCD), potassium persulfate oxidation (KPS), solid phase extraction using Tenax resin (Tenax), and polyoxymethylene solid-phase extraction (POM). Extractions were directly compared with bioaccumulation and modelled using equilibrium partitioning theory (EqPT) with a combination of different partitioning parameters (KOC and KOW values) that aimed to improve predictions. The PAH accumulation in plant roots showed good correlation with concentrations in soils, and higher concentrations of the 4–6 ring PAHs compared with 2–3 ring PAHs. Plant accumulation of 16 PAHs in L. multiflorum was estimated within a factor of 5 using direct comparison for all bioaccessibility extraction methods. Accumulation values predicted using the calculation approach depended on the combination of KOC, KOW parameters and root components (total lipid vs total dry weight) used in calculations. Using KOC values derived from historically contaminated soils improved accuracy of predicted total root accumulation although precision was low. The combined contribution of PAH in lipid and carbohydrate root components (total dry weight) overestimated accumulation and a lipid only approach using generic partitioning parameters provided more accurate and precise approximation of bioaccumulation in roots of L. multiflorum in the soils. Overall, Tenax, POM and HPCD-based extractions showed promising results for predicting L. multiflorum root accumulation using the different approaches. This work significantly extends current knowledge for integrating simple chemical extractions into ecological risk assessment frameworks for the prediction of plant PAH bioavailability in historically contaminated soils.

Evaluation of a rapid biosensor tool for measuring PAH availability in petroleum-impacted sediment

Decades of research have shown that the concentration of freely dissolved PAH (Cfree) in sediment correlates with PAH bioavailability and toxicity to aquatic organisms. Passive sampling techniques and models have been used for measuring and predicting Cfree, respectively, but these techniques require weeks for analytical chemical measurements and data evaluation. This study evaluated the performance of a portable, field-deployable antibody-based PAH biosensor method that can provide measurements of PAH Cfree within a matter of minutes using a small volume of mechanically-extracted sediment porewater. Four sediments with a wide range of PAHs (ΣPAH 2.4 to 307 mg/kg) derived from petroleum, creosote, and mixed urban sources, were analyzed via three methods: 1) bulk chemistry analysis; 2) ex situ sediment passive sampling; and 3) biosensor analysis of mechanically-extracted sediment porewater. Mean ΣPAH Cfree determined by the biosensor for the four sediments (3.1 to 55 µg/L) were within a factor of 1.1 (on average) compared to values determined by the passive samplers (2.0 to 52 µg/L). All mean values differed by a factor of 3 or less. The biosensor was also useful in identifying sediments that are likely to be non-toxic to benthic invertebrates. In two of the four sediments, biosensor results of 20 and 55 µg/L exceeded a potential risk-based screening level of 10 µg/L, indicating toxicity could not be ruled out. PAH Toxic Units (ΣTU) measured in these two sediments using the passive sampler Cfree results were also greater than the ΣTU threshold of 1 (6.7 and 5.8, respectively), confirming the conclusions reached with the biosensor. In contrast, the other two sediments were identified as non-toxic by both the biosensor (3.1 and 4.3 µg/L) and the passive sampler (ΣTUs of 0.34 and 0.039). These results indicate that the biosensor is a promising tool for rapid screening of sediments potentially-impacted with PAHs.

The remediation of PAH contaminated sediment with mangrove plant and its derived biochars

• Application of biochar remarkably increased PAH sorption from sediment. • Biochar amendments reduced the PAHs bioavailability in plant tissue after 56 days. • The tested biochars promoted the removal effeciency of PAHs in anaerobic conditions. • Biochar and K. obovata could be a sound remediation treatment when used in combination.

Assessing natural clays of a contaminated site to stabilize and reduce the ecotoxicity of a coal tar.

Stabilization/solidification is widely used for the immobilization of pollutants in matrices. This work addresses the effect of illite amendment to a liquid coal tar on organic compounds (OCs) immobilization, especially PAHs and BTEX. For practical purpose, illite was selected as raw clay material available on the coal tar contaminated site. Contaminants availability and ecotoxicity of clay/tar matrices at various ratios and considering several treatments were assessed. Varying the tar mass fraction from 1 to 0.12, strongly viscous pastes, pellets and powders were obtained successively, with minimal contaminant mobility observed for tar fractions ranging from 0.28 to 0.80. Pellets obtained for the tar fraction of 0.33 were particularly studied for toxicity tests, because of their ease of handling. Using the land snail Cantareus aspersus as an ecotoxicity probe, mechanisms of PAHs bioavailability considering several treatments were studied. Considering either land snails for direct contact or exposed to vapors, or Lymnaea stagnalis for contact with leachates, toxicity of matrices decreased with ageing or even better with incineration.

Sorption of PAHs to microplastic and their bioavailability and toxicity to marine copepods under co-exposure conditions

Organic chemical pollutants associated with microplastic (MP) may represent an alternative exposure route for these chemicals to marine biota. However, the bioavailability of MP-sorbed organic pollutants under conditions where co-exposure occurs from the same compounds dissolved in the water phase has rarely been studied experimentally, especially where pollutant concentrations in the two phases are well characterized. Importantly, higher concentrations of organic pollutants on ingested MP may be less bioavailable to aquatic organisms than the same chemicals present in dissolved form in the surrounding water. In the current study, the sorption kinetics of two model polycyclic aromatic hydrocarbons (PAHs; fluoranthene and phenanthrene) to MP particles in natural seawater at 10 and 20 °C were studied and the bioavailability of MP-sorbed PAHs to marine copepods investigated. Polyethylene (PE) and polystyrene (PS) microbeads with mean diameters ranging from 10 to 200 μm were used to identify the role of MP polymer type and size on sorption mechanisms. Additionally, temperature dependence of sorption was investigated. Results indicated that adsorption dominated at lower temperatures and for smaller MP (10 μm), while absorption was the prevailing process for larger MP (100 μm). Monolayer sorption dominated at lower PAH concentrations, while multilayer sorption dominated at higher concentrations. PE particles representing ingestible (10 μm) and non-ingestible (100 μm) MP for the marine copepod species Acartia tonsa and Calanus finmarchicus were used to investigate the availability and toxicity of MP-sorbed PAHs. Studies were conducted under co-exposure conditions where the PAHs were also present in the dissolved phase (Cfree), thereby representing more environmentally relevant exposure scenarios. Cfree reduction through MP sorption was reflected in a corresponding reduction of lethality and bioaccumulation, with no difference observed between ingestible and non-ingestible MP. This indicates that only free dissolved PAHs are significantly bioavailable to copepods under co-exposure conditions with MP-sorbed PAHs.

Bioaugmentation of PAH-Contaminated Soils With Novel Specific Degrader Strains Isolated From a Contaminated Industrial Site. Effect of Hydroxypropyl-β-Cyclodextrin as PAH Bioavailability Enhancer.

A PAHs-contaminated industrial soil was analyzed using PCR amplification of the gene 16S ribosomal RNA for the detection and identification of different isolated bacterial strains potentially capable of degrading PAHs. Novel degrader strains were isolated and identified as Achromobacter xylosoxidans 2BC8 and Stenotrophomonas maltophilia JR62, which were able to degrade PYR in solution, achieving a mineralization rate of about 1% day–1. A. xylosoxidans was also able to mineralize PYR in slurry systems using three selected soils, and the total extent of mineralization (once a plateau was reached) increased 4.5, 21, and 57.5% for soils LT, TM and CR, respectively, regarding the mineralization observed in the absence of the bacterial degrader. Soil TM contaminated with PYR was aged for 80 days and total extent of mineralization was reduced (from 46 to 35% after 180 days), and the acclimation period increased (from 49 to 79 days). Hydroxypropyl-ß-cyclodextrin (HPBCD) was used as a bioavailability enhancer of PYR in this aged soil, provoking a significant decrease in the acclimation period (from 79 to 54 days) due to an increase in PYR bioavailable fraction just from the beginning of the assay. However, a similar global extension of mineralization was obtained. A. xylosoxidans was then added together with HPBCD to this aged TM soil contaminated with PYR, and the total extent of mineralization decreased to 25% after 180 days, possibly due to the competitive effect of endogenous microbiota and the higher concentration of PYR in the soil solution provoked by the addition of HPBCD, which could have a toxic effect on the A. xylosoxidans strain.

Bioavailability and distribution of PAHs and PCBs in the sediment pore water of the German Bight and Wadden Sea

The freely dissolved concentration (Cfree) was measured for PAHs and PCBs in sediments of the German Bight and Wadden Sea. Ex-situ Solid Phase Microextraction (SPME) was applied using Polydimethlysiloxane (PDMS) coated glass fibers followed by automated thermal desorption and GC–MS analysis. This study provides the first dataset on the spatial distribution of Cfree for PAHs and PCBs in the German Bight and the Wadden Sea. We found elevated PCB concentrations in the Wadden Sea and especially in the Weser estuary. Sandy North Sea sediments were rather less contaminated, except for some former dumping sites. The sorption strength of PAHs was generally stronger, while PCBs in the Wadden Sea sediments were only weakly bound. This SPME method is a rapid and sensitive tool to study Cfree of hydrophobic organic chemicals to improve todays sediment risk assessment.

Comparison of sorption kinetics of PAHs by sorptive sinks and caco-2 cell and the correlation between bioaccessibility and bioavailability of PAHs in indoor dust

Sorptive sinks are extensively used in the bioaccessibility of organic contaminants, but their suitability for simulating the intestinal cell is seldom reported. In the present study, the sorption efficiency of PAHs by sorptive sinks including silica, poly(ethylene-co-vinyl acetate) (polyE), tenax, and C18 were compared with that by caco-2 cells. The elimination rate constants of phenanthrene, fluoranthene, pyrene, benzo(a)pyrene by caco-2 cell were 0.0417 ± 0.006 min−1, 0.0411 ± 0.0074 min−1, 0.0362 ± 0.006 min−1, and 0.0526 ± 0.0037 min−1, respectively, which were more closely to that of silica and polyE compared to other materials. This indicated that these materials might be the preferable sorptive sinks to simulate absorption of PAHs by intestinal cells. The bioaccessibility of phenanthrene, fluoranthene, pyrene, benzo(a)pyrene in indoor dust ranged from 15.5–43.5%, 9.10–38.8%, 10.0–37.9%, and 6.00–21.9%, respectively, based on physiologically based extraction test (PBET) and the sorptive sinks added in the intestinal solution led to 1.17 to 8.47-fold enhancement of bioaccessibility. The correlation of in vivo PAHs relative bioavailability (RBA) and in vitro digestion bioaccessibility with or without the sorptive sinks of indoor dust were measured, and the results indicated that silica and polyE were more likely to predict PAHs RBA of indoor dust, which was consistent with the results of sorption kinetics assay. The present results indicate that silica and polyE have the potential to simulate caco-2 cell and the inclusion of these materials in the PBET is likely to predict PAHs RBA in indoor dust.Capsule: Silica and polyE were more likely to simulate absorption of PAHs by intestinal cells, and to predict PAHs RBA of indoor dust.

In vitro prediction of polycyclic aromatic hydrocarbon bioavailability of 14 different incidentally ingested soils in juvenile swine

Predicting mammalian bioavailability of PAH mixtures from in vitro bioaccessibility results has proven to be an elusive goal. In an attempt to improve in vitro predictions of PAH soil bioavailability we investigated how energetic input influences PAH bioaccessibility by using a high and low energetic shaking method. Co-inertia analysis (COIA), and Structural Equation Modeling (SEM) were also used to examine PAH-PAH interactions during ingestion. PAH bioaccessibility was determined from 14 historically contaminated soils using the fed organic estimation of the human simulation test (FOREhST) with inclusion of a silicone rod as a sorption sink and compared to bioavailability estimates from the juvenile swine model. Shaking method significantly affected PAH bioaccessibility in the FOREhST model, with PAH desorption from the high energy FOREhST almost an order of magnitude greater compared to the low energy FOREhST. PAH-PAH interactions significantly influenced PAH bioavailability and when these interactions were used in a linear model, the model predicted benzo(a)anthracene bioavailability with an slope of 1 and r2 of 0.66 and for benzo(a)pyrene bioavailability has a slope of 1 and r2 of 0.65. Lastly, to confirm the effects as determined by COIA and SEM, we spiked low levels of benzo(a)anthracene into historically contaminated soils, and observed a significant increase in benzo(a)pyrene bioaccessibility. By accounting for PAH interactions, and reducing the energetics of in vitro extractions, we were able to use bioaccessibility to predict bioavailability across 14 historically contaminated soils. Our work suggests that future work on PAH bioavailability and bioaccessibility should focus on the dynamics of how the matrix of PAHs present in the soil interact with mammalian systems. Such interactions should not only include the chemical interactions discussed here but also the interactions of PAH mixtures with mammalian uptake systems.