Representative Polycyclic Aromatic Hydrocarbons Research Articles

Low-molecular-weight organic acids influence the sorption of phenanthrene by different soil particle size fractions.

The impact of low-molecular-weight organic acids (LMWOAs) on the sorption of phenanthrene (a representative polycyclic aromatic hydrocarbon) by different particle size fractions of a soil was investigated using a batch technique. Citric and malic acids were used in experiments. Four soil fractions were fractionated: fine sand, silt, coarse clay, and fine clay. Laser granulometry confirmed the suitability of the fractionation method used for the particle size distributions in this investigation. The sorption of phenanthrene by the different soil fractions was described well using a linear distribution-type model, and the distribution coefficients () followed a descending order of fine sand > fine clay > coarse clay > silt, irrespective of the addition of organic acids. This order was significantly positively correlated with the organic carbon content of test soil solids. The values for phenanthrene sorption by soil fractions initially increased but then decreased as the concentrations of citric and malic acids increased (0-1000 mmol L). The presence of citric and malic acid at lower concentrations (<100 mmol L) generally promoted the sorption of phenanthrene, while higher concentrations (>100 mmol L) inhibited sorption irrespective of the soil fraction. The mechanism of the LMWOA-influenced sorption of phenanthrene by test solids is discussed based on the observed sorption of organic acid, the dissolution of metal cations and minerals in soil, and the competition from dissolved organic matter in solution that were released from soil solids.

Gas chromatographic determination of polycyclic aromatic hydrocarbons in water and smoked rice samples after solid-phase microextraction using multiwalled carbon nanotube loaded hollow fiber

A novel solid-phase microextraction fiber was prepared based on multiwalled carbon nanotubes (MWCNTs) loaded on hollow fiber membrane pores. Stainless steel wire was used as unbreakable support. The major advantages of the proposed fiber are its (a) high reproducibility due to the uniform structure of the hollow fiber membranes, (b) high extraction capacity related to the porous structure of the hollow fiber and outstanding adsorptive characteristics of MWCNTs. The proposed fiber was applied for the microextraction of five representative polycyclic aromatic hydrocarbons (PAHs) from aqueous media (river and hubble–bubble water) and smoked rice samples followed by gas chromatographic determination. Analytical merits of the method, including high correlation coefficients [(0.9963–0.9992) and (0.9982–0.9999)] and low detection limits [(9.0–13.0ngL−1) and (40.0–150.0ngkg−1)] for water and rice samples, respectively, made the proposed method suitable for the ultra-trace determination of PAHs.

DBT- and DBTO2-induced dysplasia and their associated proteomic alterations in the small intestines of Wistar rats.

Dibenzothiophene (DBT) and its oxidized derivative dibenzothiophene sulfone (DBTO2) are important representatives of polycyclic aromatic hydrocarbons (PAHs). Due to the importance of PAHs in oncogenesis and the lack of toxicological investigations related to DBT and DBTO2, this work proposes to assess their toxic and molecular effects caused by chronic treatment of Wistar rats. In parallel, their effects were compared to those caused by treatment with 1,2-dimethylhydrazine (DMH), a classic mutagenic agent. At the 14th day post-treatment, the animals were sacrificed and blood withdrawn for hematology and evaluation of liver and pancreatic functions. No significant alterations were observed. Nevertheless, histopathological analyses revealed dysplastic lesions in the intestines of animals treated with DBT and DBTO2. CD44 and carcinoembryonic antigen (CEA) staining demonstrated an approximately 3-fold increase in expression of both tissue markers for animals administered DBT, DBTO2, and DMH. A comparative two-dimensional gel analysis revealed additional 23 proteins exhibiting altered levels in the small intestines caused by exposure to DBT and DBTO2. At last, a protein-metabolite interaction map provided major insights into the metabolism of the dysplastic tissues. Our results provided strong evidence that DBT and its derivative could potentially act as cancer inducers, highlighting their toxicological and environmental relevance.

Digital gene expression analysis of reproductive toxicity of benzo[a]pyrene in male scallop chlamys farreri

Benzo[a]pyrene (BaP) is a representative polycyclic aromatic hydrocarbon (PAH) and is studied widely for its strong toxicity and wide distribution. Although BaP pollution in marine environment is increasing, molecular mechanisms underlying reproductive toxicity of BaP in marine mollusks have been seldom systematically studied, especially in males. In this study, genes that regulated reproductive responses of Chlamys farreri under BaP stress were analyzed through digital gene expression (DGE) sequencing with testis tissues. A total of 12,485,055 and 14,454,127 clean reads were generated from control and BaP exposure DGE libraries, respectively. After comparing two libraries, 1051 differentially expressed genes were detected, with 223 up-regulated and 828 down-regulated genes. Gene ontology (GO) annotation and kyoto encyclopedia of genes and genomes (KEGG) pathway analyses were performed on all genes to understand their biological functions and processes. The results showed that numerous enriched, differentially expressed genes related to aromatic compound catabolic processes, spermatid development, microtubule-based movement, energy production and immune response. Quantitative real-time PCR was performed to verify the expressed genes of DGE. The study generated data to show the overall reproductive transcription responses of male C. farreri under BaP stress, and it also can serve as the reference for future study of organic pollutions in aquatic mollusks.

Thermal equation of state of solid naphthalene to 13 GPa and 773 K: in situ X-ray diffraction study and first principles calculations.

In a wide range of P-T conditions, such fundamental characteristics as compressibility and thermoelastic properties remain unknown for most classes of organic compounds. Here we attempt to clarify this issue by the example of naphthalene as a model representative of polycyclic aromatic hydrocarbons (PAHs). The elastic behavior of solid naphthalene was studied by in situ synchrotron powder X-ray diffraction up to 13 GPa and 773 K and first principles computations to 20 GPa and 773 K. Fitting of the P-V experimental data to Vinet equation of state yielded T 0 = 8.4(3) GPa and T' = 7.2 (3) at V0 = 361 Å(3), whereas the thermal expansion coefficient was found to be extremely low at P > 3 GPa (about 10(-5) K(-1)), in agreement with theoretical estimation. Such a diminishing of thermal effects with the pressure increase clearly demonstrates a specific feature of the high-pressure behavior of molecular crystals like PAHs, associated with a low energy of intermolecular interactions.

Use of toxicogenomics to predict the potential toxic effect of Benzo(a)pyrene on zebrafish embryos: Ocular developmental toxicity

Benzo(a)pyrene (BaP) is a representative polycyclic aromatic hydrocarbon (PAH), which is ubiquitous in the environment. The toxic effects of BaP on fish embryos have been described in detail, but some potentially toxic effects of BaP might have been neglected owing to the limitations of traditional techniques. In the present research, global transcriptional patterns were used to study the potentially toxic effects of BaP, as well as its underlying toxicological mechanisms. The expression levels of multiple genes were significantly changed by BaP exposure. The results of ontology assignments and cluster analysis showed that BaP could affect the processes of photoreceptor maintenance and phototransduction. We also conducted an experiment on phototactic response and found that larvae exposed to BaP displayed a decreasing response to light. In addition, BaP exposure decreased the cellular density of the ganglion cell layer (GCL) significantly. These results suggested that BaP exposure induced visual system developmental defects and dysfunction by perturbation of photoreceptor development related genes. Our results were helpful for an understanding of the toxicity of BaP. This study also indicated that microarray analysis was effective for predicting the potential toxicity of chemicals with high sensitivity and accuracy.

Metabolism of a Representative Oxygenated Polycyclic Aromatic Hydrocarbon (PAH) Phenanthrene-9,10-quinone in Human Hepatoma (HepG2) Cells

Exposure to polycyclic aromatic hydrocarbons (PAHs) in the food chain is the major human health hazard associated with the Deepwater Horizon oil spill. Phenanthrene is a representative PAH present in crude oil, and it undergoes biological transformation, photooxidation, and chemical oxidation to produce its signature oxygenated derivative, phenanthrene-9,10-quinone. We report the downstream metabolic fate of phenanthrene-9,10-quinone in HepG2 cells. The structures of the metabolites were identified by HPLC–UV–fluorescence detection and LC–MS/MS. O-mono-Glucuronosyl-phenanthrene-9,10-catechol was identified, as reported previously. A novel bis-conjugate, O-mono-methyl-O-mono-sulfonated-phenanthrene-9,10-catechol, was discovered for the first time, and evidence for both of its precursor mono conjugates was obtained. The identities of these four metabolites were unequivocally validated by comparison to authentic enzymatically synthesized standards. Evidence was also obtained for a minor metabolic pathway of phenanthrene-9,10-quinone involving bis-hydroxylation followed by O-mono-sulfonation. The identification of 9,10-catechol conjugates supports metabolic detoxification of phenanthrene-9,10-quinone through interception of redox cycling by UGT, COMT, and SULT isozymes and indicates the possible use of phenanthrene-9,10-catechol conjugates as biomarkers of human exposure to oxygenated PAH.

Nonhomologous DNA end joining and chromosome aberrations in human embryonic lung fibroblasts treated with environmental pollutants

In order to evaluate the ability of a representative polycyclic aromatic hydrocarbon (PAH) and PAH-containing complex mixtures to induce double strand DNA breaks (DSBs) and repair of damaged DNA in human embryonic lung fibroblasts (HEL12469 cells), we investigated the effect of benzo[a]pyrene (B[a]P) and extractable organic matter (EOM) from ambient air particles <2.5μm (PM2.5) on nonhomologous DNA end joining (NHEJ) and induction of stable chromosome aberrations (CAs). PM2.5 was collected in winter and summer 2011 in two Czech cities differing in levels and sources of air pollutants. The cells were treated for 24h with the following concentrations of tested chemicals: B[a]P: 1μM, 10μM, 25μM; EOMs: 1μg/ml, 10μg/ml, 25μg/ml. We tested several endpoints representing key steps leading from DSBs to the formation of CAs including histone H2AX phosphorylation, levels of proteins Ku70, Ku80 and XRCC4 participating in NHEJ, in vitro ligation activity of nuclear extracts of the HEL12469 cells and the frequency of stable CAs assessed by whole chromosome painting of chromosomes 1, 2, 4, 5, 7 and 17 using fluorescence in situ hybridization. Our results show that 25μM of B[a]P and most of the tested doses of EOMs induced DSBs as indicated by H2AX phosphorylation. DNA damage was accompanied by induction of XRCC4 expression and an increased frequency of CAs. Translocations most frequently affected chromosome 7. We observed only a weak induction of Ku70/80 expression as well as ligation activity of nuclear extracts. In summary, our data suggest the induction of DSBs and NHEJ after treatment of human embryonic lung fibroblasts with B[a]P and complex mixtures containing PAHs.

The effects of benzo[a]pyrene on leucocyte distribution and antibody response in rainbow trout (Oncorhynchus mykiss)

Polycyclic aromatic hydrocarbons (PAHs) are a group of compounds with immunotoxic and carcinogenic potential that may pose a threat to fish populations. This study aims to utilize a newly developed fish immunotoxicology model to determine the immune tissue/cell population level effects of PAHs on rainbow trout, using benzo[a]pyrene (BaP) as a representative immunotoxic PAH. Intraperitoneal injection of 25 or 100mg/kg BaP resulted in sustained exposure as indicated by biliary fluorescence at BaP wavelengths for up to 42 days. A new flow cytometry method for absolute counts of differential leucocyte distributions in spleen, blood, and head kidney was developed by combining absolute quantitative counts of total leukocytes in the tissue (3,3′-dihexyloxacarbocyanine iodide (DiOC6) dye) with relative differential counts using monoclonal antibodies for B cells, T cells, myeloid cells, and thrombocytes. Experiments indicated dose- and time-dependent decreases in the absolute number of B cells, myeloid cells, or T cells in blood, spleen, or head kidney after 7, 14 or 21 d of exposure. There was no change in the absolute numbers of erythrocytes or thrombocytes in any tissue. When rainbow trout were exposed to inactivated Aeromonas salmonicida after a 21 d exposure to 100mg/kg BaP, circulating antibody concentrations were decreased by 56%. It was concluded that BaP has a cell lineage-specific toxic effect on some immune cells of rainbow trout, and causes a decrease in circulating antibody levels.

Use of [13C]/[12C] ratios as an indicator of the role of microorganisms in protection of plants from the phytotoxic action of naphthalene

Using molecular and isotopic mass spectrometry, we investigated the toxic effect of naphthalene as a representative of polycyclic aromatic hydrocarbons (PAHs) on plants growing under sterile conditions and plants inoculated with microorganisms capable and incapable of naphthalene degradation. Tobacco plants of the Samsun variety were grown in a closed gas-nutrient system on a mineral medium with sucrose as a carbon source. Naphthalene used as a toxicant at a concentration of 5.2 × 10−4% contained 13C isotope whose amount was characterized by the value δ13C = +281.4 ± 0.6‰ relative to the PDB standard and differed from that of sucrose, the main source of carbon (δ13C = −12.0 ± 0.1‰). Degradation of naphthalene was determined by the inclusion of its carbon in metabolic CO2 and plant tissues (the root, stem, leaves). The effect of naphthalene on plants was indicated by the rates of O2 production and CO2 uptake during the light period as compared with the dark period of exposure. A decrease of the toxic effect of naphthalene on plants was observed only at the inoculation of plants with Pseudomonas aureofaciens BS1393 rhizosphere bacteria bearing plasmid pBS216, which controls the naphthalene biodegradation ability. The occurrence of other heterotrophic microorganisms incapable of naphthalene degradation had no similar protective effect.

PAHs Removal from Urban Storm Water Runoff by Different Filter Materials

AbstractUrban storm water runoff is contaminated as deleterious materials wash from roadways, parking lots, and open spaces, and the subsequent discharge into surface water sources, such as lakes, can pose adverse effects on public health and the environment. Oil leaks and spills on roadways and parking lots can contain toxic polycyclic aromatic hydrocarbons (PAHs) that can be washed by storm water runoff. Although many best management practices have been developed to treat urban storm water, in-ground filter systems can be best suited in urban site-constrained settings. This paper investigates the effectiveness of different permeable inorganic materials as filter media for the removal of PAHs from storm water runoff. Several series of batch experiments were conducted using four different filter media (calcite, zeolite, sand, and iron filings) and synthetic storm water containing representative PAHs (naphthalene or phenanthrene) at different initial concentrations. The PAH removal and system chemistry in ...

Interception of Benzo[a]pyrene-7,8-dione by UDP Glucuronosyltransferases (UGTs) in Human Lung Cells

Polycyclic aromatic hydrocarbons (PAHs) are environmental and tobacco carcinogens. Proximate carcinogenic PAH trans-dihydrodiols are activated by human aldo-keto reductases (AKRs) to yield electrophilic and redox-active o-quinones. Interconversion among benzo[a]pyrene (B[a]P)-7,8-dione, a representative PAH o-quinone, and its corresponding catechol generates a futile redox-cycle with the concomitant production of reactive oxygen species (ROS). We investigated whether glucuronidation of B[a]P-7,8-catechol by human UDP glucuronosyltransferases (UGTs) could intercept the catechol in three different human lung cells. RT-PCR showed that UGT1A1, 1A3, and 2B7 were only expressed in human lung adenocarcinoma A549 cells. The corresponding recombinant UGTs were examined for their kinetic constants and product profile using B[a]P-7,8-catechol as a substrate. B[a]P-7,8-dione was reduced to B[a]P-7,8-catechol by dithiothreitol under anaerobic conditions and then further glucuronidated by the UGTs in the presence of uridine-5′-diphosphoglucuronic acid as a glucuronic acid group donor. UGT1A1 catalyzed the glucuronidation of B[a]P-7,8-catechol and generated two isomeric O-monoglucuronsyl-B[a]P-7,8-catechol products that were identified by RP-HPLC and by LC-MS/MS. By contrast, UGT1A3 and 2B7 catalyzed the formation of only one monoglucuronide, which was identical to that formed in A549 cells. The kinetic profiles of three UGTs followed Michaelis–Menten kinetics. On the basis of the expression levels of UGT1A3 and UGT2B7 and the observation that a single monoglucuronide was produced in A549 cells, we suggest that the major UGT isoforms in A549 cells that can intercept B[a]P-7,8-catechol are UGT1A3 and 2B7.

Size-dependent melting of polycyclic aromatic hydrocarbon nano-clusters: A molecular dynamics study

The size-dependent melting behaviour of clusters of polycyclic aromatic hydrocarbon (PAH) molecules is studied computationally using the isotropic PAHAP potential (Totton et al., 2012, Phys Chem Chem Phys, 14, 4081–4094). The investigation aims to shed light on the understanding of the liquid-like behaviour of PAH clusters. Detailed molecular dynamic (MD) simulations are performed to investigate the size-dependent melting of two representative homogeneous PAH clusters composed of either pyrene (C16H10) or coronene (C24H12) molecules. The evolution of the intermolecular energy and the Lindemann index are used to estimate the melting points of individual nano-clusters. The results from the MD simulations show that individual PAH molecules within nano-clusters are highly mobile below typical flame temperatures. A detailed morphological investigation of coronene500 further reveals that the coronene clusters evolve from a columnar particle in the solid phase to an irregular spherical particle in the liquid phase. In contrast, no such evolution is observed for pyrene300 which remains in a spherical configuration. The nano-cluster reduced melting temperature decreases with decreasing particle size following a linear relation with reciprocal size. The melting process of these clusters starts from the surface and the liquid layer grows inwards with increasing temperature.

Gene expression profile changes induced by acute toxicity of benzo[a]pyrene in marine medaka

Differential gene expression profiling was carried out using cDNA microarray hybridization on hepatic tissue from marine medaka (Oryzias javanicus) after exposure to benzo[a]pyrene (BaP), a representative polycyclic aromatic hydrocarbon classified as a persistent organic pollutant. Forty-one differentially expressed candidate genes were identified; 18 were induced and 23 were repressed (P/0.05). The genes were assembled into 18 groups based mainly on the Eukaryotic Orthologous Groups classification. These differentially expressed gene candidates could have great potential as molecular biomarkers for identifying environmental stressors and prognosis for the biological effects of BaP. The candidate genes isolated in this study were grouped into endocrine disruption, cardiovascular disease, tumorigenesis, immune response, detoxification, energy production and conversion, and other biological responses. Our results could allow future studies to assess the molecular mechanisms of BaP toxicity and to develop a systems biology approach to environmental stress biology.

Can root exudate components influence the availability of pyrene in soil?

Little information is currently available regarding the influence of different root exudate components (RECs) on the availability of persistent organic pollutants in the soil environment. In this study, we investigated the impacts of different RECs including organic acids, amino acids, and fructose on the availability of pyrene as a representative polycyclic aromatic hydrocarbon (PAH) in soils. Citric acid, oxalic acid, malic acid, serine, alanine, and fructose were used in the experiments as representative RECs. Pyrene-spiked soils (TypicPaleudalfs) with present RECs were incubated for 30 days, and the available fraction of pyrene was determined using n-butanol extraction procedure. The amount of n-butanol-extractable pyrene in soil increased with the addition of tested RECs and increased when REC concentrations are enhanced within the range of 0–21 g kg−1. The extractability of pyrene in soil with REC treatments and the enhancement ratio (r, %) of the extractable pyrene in soil by the addition of RECs after a 30-day incubation decreased in the following order: organic acids (oxalic acid ≥ citric acid > malic acid) > amino acid (alanine > serine) > fructose. This decrease was observed irrespective of soil sterilization, although the concentrations of extractable pyrene were lower in non-sterilized soils compared to sterilized soils. The concentrations of metal cations and dissolved organic matter (DOM) in solution increased when organic acids were added. The tested RECs at concentrations of 0–21 g kg−1 clearly enhanced the availability of pyrene in soils, and larger amounts of RECs resulted in higher pyrene availabilities in the tested soils. Microbial biodegradation diminished the amount of available pyrene irrespective of the presence of RECs. The mechanism of REC-influenced availability of pyrene in soil may be related to the metal dissolution and release of DOM from soil solids. The results of this study will be useful in assessing PAH-related risks to human health and the environment and will be instructive in food safety and remediation strategies at contaminated sites.

The effects of benzo[a]pyrene on leukocyte distribution and antibody response in rainbow trout (Oncorhynchus mykiss)

a b s t r a c t Polycyclic aromatic hydrocarbons (PAHs) are a group of compounds with immunotoxic and carcino- genic potential that may pose a threat to fish populations. This study aims to utilize a newly developed fish immunotoxicology model to determine the immune tissue/cell population level effects of PAHs on rainbow trout, using benzo(a)pyrene (BaP) as a representative immunotoxic PAH. Intraperitoneal injec- tion of 25 or 100 mg/kg BaP resulted in sustained exposure as indicated by biliary fluorescence at BaP wavelengths for up to 42 days. A new flow cytometry method for absolute counts of differential leucocyte distributions in spleen, blood, and head kidney was developed by combining absolute quantitative counts of total leukocytes in the tissue (3,3

Response of bacterial communities to short-term pyrene exposure in red soil

Pyrene, a representative polycyclic aromatic hydrocarbon (PAH) compound produced mainly from incomplete combustion of fossil fuels, is hazardous to ecosystem health. However, long-term exposure studies did not detect any significant effects of pyrene on soil microorganism. In this study, short-term microcosm experiments were conducted to identify the immediate effect of pyrene on soil bacterial communities. A freshlycollected pristine red soil was spiked with pyrene at 0, 10, 100, 200, and 500 mg·kg−1 and incubated for one day and seven days. The bacterial communities in the incubated soils were analyzed using 16S rRNA sequencing and terminal restriction fragment length polymorphism (TRFLP) methods. The results revealed high bacterial diversity in both unspiked and pyrene-spiked soils. Only at the highest pyrene-spiking rate of 500 mg·kg−1, two minor bacteria groups of the identified 14 most abundant bacteria groups were completely suppressed. Short-term exposure to pyrene resulted in dominance of Proteobacteria in soil, followed by Acidobacteria, Firmutes, and Bacteroidetes. Our findings showed that bacterial community structure did respond to the presence of pyrene but recovered rapidly from the perturbation. The intensity of impact and the rate of recovery showed some pyrene dosage-dependent trends. Our results revealed that different levels of pyrene may affect the bacterial community structure by suppressing or selecting certain groups of bacteria. It was also found that the bacterial community was most susceptible to pyrene within one day of the chemical addition.

Ca2+ Promoted the Low Transformation Efficiency of Plasmid DNA Exposed to PAH Contaminants

The effects of interactions between genetic materials and polycyclic aromatic hydrocarbons (PAHs) on gene expression in the extracellular environment remain to be elucidated and little information is currently available on the effect of ionic strength on the transformation of plasmid DNA exposed to PAHs. Phenanthrene and pyrene were used as representative PAHs to evaluate the transformation of plasmid DNA after PAH exposure and to determine the role of Ca2+ during the transformation. Plasmid DNA exposed to the test PAHs demonstrated low transformation efficiency. In the absence of PAHs, the transformation efficiency was 4.7 log units; however, the efficiency decreased to 3.72–3.14 log units with phenanthrene/pyrene exposures of 50 µg·L–1. The addition of Ca2+ enhanced the low transformation efficiency of DNA exposed to PAHs. Based on the co-sorption of Ca2+ and phenanthrene/pyrene by DNA, we employed Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and mass spectrometry (MS) to determine the mechanisms involved in PAH-induced DNA transformation. The observed low transformation efficiency of DNA exposed to either phenanthrene or pyrene can be attributed to a broken hydrogen bond in the double helix caused by planar PAHs. Added Ca2+ formed strong electrovalent bonds with “–POO––” groups in the DNA, weakening the interaction between PAHs and DNA based on weak molecular forces. This decreased the damage of PAHs to hydrogen bonds in double-stranded DNA by isolating DNA molecules from PAHs and consequently enhanced the transformation efficiency of DNA exposed to PAH contaminants. The findings provide insight into the effects of anthropogenic trace PAHs on DNA transfer in natural environments.

Influence of nitrogen excited species on the destruction of naphthalene in nitrogen and air using surface dielectric barrier discharge

The destruction of naphthalene, as representative polycyclic aromatic hydrocarbons, by surface dielectric barrier discharge is investigated in air as well as dry and humidified nitrogen at ambient temperature. Naphthalene destruction efficiency is evaluated in terms of chemical change vis-a-vis energy utilization. The detected byproducts are qualitatively evaluated in order to understand the role of the active species in the destruction process. The results show that the destruction efficiency and the energy efficiency are higher in the dry nitrogen than in the humidified nitrogen, and these decrease with the increase of the humidity. Measured concentration of ozone as a byproduct qualitatively indicates the roles of oxygen and ozone in the destruction process in air. The analysis of the aerosol particles formed during the destruction process, both in the dry and humidified nitrogen, confirmed the adverse effects of the humidity on the byproducts formation and subsequently on the destruction process.

The Impact of Different Root Exudate Components on Phenanthrene Availability in Soil

This study investigated the impact of different root exudate components (RECs) on the availability of phenanthrene as a representative of polycyclic aromatic hydrocarbons (PAHs) in soil (TypicPaleudalfs) using laboratory batch assays. Four typical RECs were compared including malic acid, alanine, serine, and fructose. An n‐butanol extraction procedure and a sorption–desorption experiment were used to predict the availability of phenanthrene in soil. We found that the n‐butanol extractable amounts of phenanthrene in soil increased with increasing REC concentrations. The extractability of phenanthrene in soil with various treatments decreased in the following order: malic acid &gt; alanine &gt; serine &gt; fructose treatments. Organic acid (malic acid) resulted in the most significant increase in PAH extractability by soil. Phenanthrene sorption by soil could be described using a linear model regardless of the presence of RECs. The simulated distribution constants (Kd) and carbon‐normalized distribution constants (Koc) for phenanthrene sorption decreased significantly with the addition of all test RECs. Malic acid enhanced desorption of phenanthrene from soils. In contrast, lower concentrations of test amino acids promoted phenanthrene desorption, while higher concentrations inhibited desorption. Fructose had a minimal effect on PAH desorption. The mechanism of REC‐influenced availability of PAH in soil is discussed based on the observed metal dissolution, soil organic matter reduction, and dissolved organic matter release from soil solids.