Absorption Of Polycyclic Aromatic Hydrocarbons Research Articles

Molecular Plasmon-Phonon Coupling.

Charged polycyclic aromatic hydrocarbons (PAHs), ultrasmall analogs of hydrogen-terminated graphene consisting of only a few fused aromatic carbon rings, have been shown to possess molecular plasmon resonances in the visible region of the spectrum. Unlike larger nanostructures, the PAH absorption spectra reveal rich, highly structured spectral features due to the coupling of the molecular plasmons with the vibrations of the molecule. Here, we examine this molecular plasmon-phonon interaction using a quantum mechanical approach based on the Franck-Condon approximation. We show that an independent boson model can be used to describe the complex features of the PAH absorption spectra, yielding an analytical and semiquantitative description of their spectral features. This investigation provides an initial insight into the coupling of fundamental excitations-plasmons and phonons-in molecules.

Effect of Polycyclic Aromatic Hydrocarbon Source Materials and Soil Components on Partitioning and Dermal Uptake.

The bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soils can be influenced by the source material they are emitted within, the properties of the receiving soil, weathering processes, and the concentration of PAHs. In this study 30 contaminated soils were constructed with common PAH sources (fuel oil, soot, coal tar based skeet particles) and direct spike with a solvent added to different types and contents of soil organic matter and minerals to achieve PAH concentrations spanning 4 orders of magnitude. Source material had the greatest impact on PAH partitioning. Soils containing skeet generally exhibited the highest KD values, followed by soot, fuel oil, and solvent spiked soils. Among all soil compositions, the presence of 2% charcoal had the largest enhancement of KD. Partitioning behavior could not be predicted by an organic carbon and black carbon partitioning model. Including independently measured partitioning behavior of the soil components and PAH sources allowed better prediction but still suffered from issues of interaction (oil sorption in peat) and highly nonlinear partitioning with depletion (for skeet). Dermal absorption of PAHs measured using pig skin was directly related to the freely dissolved aqueous concentration in soil and not the total concentration in the soil. Overall, we show that PAH source materials have a dominating influence on partitioning, highlighting the importance of using native field soils in bioavailability and risk assessments.

A review of non-exhaustive chemical and bioavailability methods for the assessment of polycyclic aromatic hydrocarbons in soil

Abstract Current environmental regulations relating to risk assessment for contaminated sites are often set assuming that the contaminant is 100% bioavailable. It is therefore not surprising that remediation of contaminated sites is very expensive and maybe it is unrealistic to achieve a “remediated state” under current regulatory guidelines using existing technologies. In fact the reality is that only a portion of the contaminant on site becomes available for absorption and goes into the systemic circulation. This article gives an overview of existing in vivo animal models that quantify oral bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soil. It also provides a summary of in vitro gastrointestinal extraction methodologies and some of the key factors influencing absorption of PAHs in soil. For innovation, it highlights that bioaccessibility values derived from in vitro studies still require validation from in vivo animal models to gain regulatory acceptance. Additionally, this review highlights the use of non-exhaustive chemical methodologies as a valuable tool to understanding the bioavailability process and behaviour of PAHs in soil.

Distribution and accumulation of polycyclic aromatic hydrocarbons (PAHs) in the food web of Nansi Lake, China.

The concentrations of polycyclic aromatic hydrocarbons (PAHs) were analyzed in water, sediment, and biota (aquatic plant, shrimp, and fish) of Nansi Lake by gas chromatography-mass spectrometry (GC-MS). The concentrations of total PAHs were 27.54-55.04 ng L(-1) in water, 80.31-639.23 ng g(-1) dry weight (dw) in sediments, 20.92-192.78 ng g(-1) dw in aquatic plants, and 67.3-533.9 ng g(-1) dw in fish and shrimp muscles. The ratios of phenanthrene to anthracene (Ph/An), fluoranthene to pyrene (Flu/Pyr), and low molecular weight to high molecular weight (LMW/HMW) in sediment indicated that the sources of the PAHs were a mixture of pyrolytic and petrogenic contamination at most sampling sites in Nansi Lake. The composition profile of PAHs in plants was similar to that in water and animals with 2-3 ring PAHs being dominant. The 4-6 ring PAHs were the dominant PAH compounds in sediment. There is a positive correlation between sediment and aquatic plants, but their PAH composition profiles were different, implying that aquatic plant absorption of PAHs from sediment is selective and the accumulation of PAHs in aquatic plants is different. The concentration of PAHs in fish showed a positive correlation with plants, reflecting that the PAHs in fish are mainly absorbed from aquatic plants rather than directly from the water. Bioaccumulation of LMW PAHs in aquatic biota was higher than HMW PAHs. The biota-sediment accumulation factor (BSAF) values of total PAHs in the plants Potamogeton lucens Linn and Ceratophyllum demersum Linn were higher than that in most animals. The BSAF values of total PAHs in animals were in the following order: Cyprinus carpio>Macrobrachium nipponense>Carassius auratus>Channa argus. There was no significant relationship between PAH bioaccumulation and trophic levels in Nansi Lake. Risk assessment of PAHs in water, sediment, and animals indicated that the water environment of Nansi Lake is safe at present. It is worthwhile to note that benzo [a] anthracene (BaA), benzo [a] pyrene (BaP), indeno [1,2,3-cd] pyrene (InP), dibenz [a, h] anthracene (DBA), and benzo [ghi] perylene (BghiP) were detected in sediment, plants, and animals at all sampling sites, and they have potential carcinogenicity to the organisms of Nansi Lake.

Occupational exposure to polycyclic aromatic hydrocarbons: relations between atmospheric mixtures, urinary metabolites and sampling times.

Occupational exposure to polycyclic aromatic hydrocarbons (PAHs) can be assessed by either air monitoring or biomonitoring using urinary 1-hydroxypyrene (1-OHP) or 3-hydroxybenzo(a)pyrene (3-OHBaP). The aim of this study was to understand the links between atmospheric PAHs and urinary metabolites, in order to improve the biomonitoring strategy for assessing carcinogenic risk. Personal air sampling for pyrene and BaP measurements, and urines for 1-OHP and 3-OHBaP analyses of seven workers from electrode production plant were collected every day of the working week. High variability of atmospheric levels between activities and between days was observed, especially for gaseous pyrene. No correlation was found between urinary metabolites: 1-OHP maximum levels occurred for "electrode extrusion" activity; those of 3-OHBaP occurred for "raw materials dispatcher." Sixty percentage of 3-OHBaP maximum levels were observed in urines collected at the beginning of shift the last workday. Those of 1-OHP occurred at different sampling times, depending on the gaseous pyrene levels (not stopped by P3 respirators). Dermal absorption of PAHs was confirmed by significant effect of particulate pyrene on 1-OHP in the samples collected the morning of the following day (p < 0.02, n = 25). Lack of correlation between metabolites concentrations emphasizes the non-relevance of 1-OHP, from a non-carcinogenic gaseous and particulate compound, and the great interest of 3-OHBaP, from carcinogenic BaP. Its slower urinary elimination prevents the risk of exposure underestimation, and urinary analysis should be performed at the beginning of shift the end of working week, especially in case of high exposure variability.

Procarcinogens: Polycyclic Aromatic Hydrocarbons and Heavy Metal Content in Some Locally Processed Foods in South Eastern Nigeria

This study investigated the presence of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in commonly consumed roasted meats and smoked fish in Owerri, Imo State, Nigeria. The processed foods were grouped as; freshly processed6 to 12 hours heat/flame/smoke exposure and long processed7 days heat/flame/smoke exposure. Freshly processed (FP) and long processed (LP) beef, fatty beef, chicken, fish and pork samples were purchased from road-side food vendors, wrapped in clean labelled paper foil and taken to the laboratory for analysis. Gas chromatography with flame ionization detector (GC-FID) was used for the evaluation of PAH and atomic absorption spectrophotometer (AAS) was used to determine heavy metals. Our result showed that the total concentration of PAHs in LP food samples were higher when compared to FP samples. Benzo(a)pyrene and other PAHs which are probable human carcinogen, were present in varying concentrations in the samples. Toxic heavy metals such as lead and cadmium were present at varying concentrations in the samples, while mercury was not detected in any of the samples. This study have added to the numerous evidences that processing of food by Research Article British Journal of Applied Science & Technology, 4(1): 249-260, 2014 250 exposure to heat, flame and smoke encourages the generation of toxic compounds and the nature of the food chain and certain environmental activities can impact negatively on their nutritional content. This therefore places consumers at potential health risk.

Absorption of Hazardous Pollutants by a Medicinal FernBlechnum orientaleL.

A Chinese medicinal fern Blechnum orientale (Linn) was separately collected from polluted and unpolluted sites to determine whether it could accumulate hazardous pollutants or not. Metal concentrations (Cu, Zn, Mn, Pb, Cd, Cr, As, and Hg) both in the fronds and roots and polycyclic aromatic hydrocarbons (PAHs) in the fronds of this fern were quantified. At both sites, roots of B. orientale had significantly higher heavy metals than the fronds. Concentrations of Pb, As, Hg, Cd, and Cu in the fronds at the polluted site were more than 2, 6, 7, 14, 5, and 13 times of those at the unpolluted site. Translocation factor and bioaccumulation factor implied that B. orientale did not have a good ability to transport heavy metals from the roots to the fronds. Total PAHs in the fronds at the polluted site were significantly higher than those at the unpolluted site, indicating the physiological PAHs absorption by B. orientale growing at polluted sites. Uptake of pollutants via stomata might be the main reason causing the significant accumulation of hazardous pollutants in the fronds of B. orientale. Large-scale systematical survey and intensive monitoring on pollutants in this medicinal fern should be necessarily strengthened.

Origin and Distribution of Polycyclic Aromatic Hydrocarbons in Lagoon Ecosystems of Morocco

Polycyclic Aromatic Hydrocarbons (PAHs) were determined in sediments and bivalves by the Gas chromatography coupled to Mass spectrometer (GC/MS). PAHs concentrations in sediments of My Bousselham and Khnifiss, Atlantics lagoons, (expressed as ∑PAH) ranged from 31 to 82 ng/g of dry weight and from 6.6 to 34 ng/g of dry weight, respectively. Concerning organisms, PAHs levels contamination ranged from 28 to 117 ng/g of dry weight for My Bousselham (Ruditapes Decussates) and from 7 to 18.5 ng/g of dry weight for Khnifiss Lagoon Oyster (Crassostrea gigas). In the Med Lag (Nador), the results obtained showed a range varying from 6 to 126 ng/g of dry weight for sediments and from 24 to 32 ng/g of dry weight for organisms (Mytilus Galoprovincialis). The origin investigation of PAHs in sediment revealed, that the process of combustion was the main source in these Lagoons, while the diagenetic source, related to the high concentrations obtained of Perylene, was established only in both Atlantics Lagoons (Khnifiss and My Bousselham). A prevalence of high molecular weight PAHs was observed, with a considerable predominance of 4-ring PAHs in sediments and organisms of the My bousselham and Nador lagoons, while, no clear predominance was observed in the compartments studied in the Khnifiss lagoon. Correlation study of individual PAH between sediments and organisms, showed that absorption by Clams of low molecular weight PAH group, of which correlation was low, could be done through the water dissolved form, while the absorption of heavier molecular weight PAHs, which showed a high correlation of their distribution between sediments and Clams, could be the absorption from particulate matter.

A Novel “By Difference” Method for Assessing Dermal Absorption of Polycyclic Aromatic Hydrocarbons from Soil at Federal Contaminated Sites

A highly precautionary cost-effective method for estimating dermal absorption using data from 24-h skin soap washes from in vitro dermal absorption tests in Bronaugh flow-through diffusion cells with human skin is reported. Skin was dosed with 16 U.S. Environmental Protection (EPA) priority polycyclic aromatic hydrocarbons (PAH) applied in mixture each at 2 μg/ml (ppm) in acetone without soil. Concurrent tests were conducted with an unspiked aqueous suspension of PAH-contaminated soil obtained from a Canadian federal contaminated site. Percentage dermal absorption was estimated “by difference” from the applied dose and that detected by high-performance liquid chromatography (HPLC) in 24-h skin soap washes. The dermal absorption for 11 PAH ranged from 71 to 88.3% without and with soil, respectively. Lower absorption was found for 5 PAH in soil, in the range of 26.4 to 60.8%. Data could not be corrected for evaporative loss due to inconsistent data from Tenax adsorbent. Corroboratory gas chromatography/mass spectroscopy (GC/MS) tests are needed. Previously published in vitro data from the authors' laboratory supported use of the “by difference” method.

DNA adducts in skin biopsies and 1-hydroxypyrene in urine of psoriasis patients and healthy volunteers following treatment with coal tar

Coal tar ointments (CTO) are frequently used in the treatment of psoriasis and eczema, but CTO contain carcinogenic polycyclic aromatic hydrocarbons (PAH). PAH are absorbed and metabolized in the skin. In psoriasis, the skin barrier is altered and therefore, absorption and metabolism of PAH may differ from healthy skin. In this study, levels of urinary 1-hydroxypyrene and PAH-DNA adducts in the skin were studied in psoriatic patients and healthy volunteers. Three punch biopsies were taken from the lower back of 10 male volunteers and from a psoriatic plaque in 10 male patients. A surface of 6.25cm2 was treated with CTO. After 96h CTO was removed and another three skin biopsies were collected from the treated area. DNA was isolated from skin biopsies and urine was collected during and after the exposure period. After 24h, a twofold lower 1-hydroxypyrene urinary excretion was observed in patients compared to healthy volunteers and after 48h, this difference reached statistical significance (p<0.05). Over 96h the median level of the sum of PAH-DNA adducts, analyzed by 32P-post-labeling, increased from 3.5 before CTO administration to 21.1 adducts per 108 nucleotides in volunteers, and from 1.0 to 3.6 adducts per 108 nucleotides in patients. At 96h, PAH-DNA levels were higher in healthy volunteers than in patients (p<0.05). Biomarkers for uptake, bioavailability and bioactivation of PAH were lower in patients compared to volunteers. These data suggest a lower risk of carcinogenic effects of CTO in psoriatic skin compared to healthy skin.

Mobile passive samplers: Concept for a novel mode of exposure

Integrative passive sampling with devices such as semipermeable membrane devices generally relies on rigs for month-long static exposures in water. We evaluate here whether mobile exposures of passive samplers can provide reliable estimates of dissolved contaminant concentrations. Mobile exposures were obtained by towing samplers fastened to the end of a benthic trawl net. Significant and reproducible absorption of polycyclic aromatic hydrocarbons during 5 h-long deployments was made possible by high sampling rates resulting from high water turbulences during towing at 1.2–1.5 knots. Sampling rates (72–215 L d−1) estimated from the dissipation of performance reference compounds were supported by in situ calibration with samplers exposed for a 30 days in the vicinity of the test site. Higher fluoranthene and pyrene absorption in samplers exposed to the trawling-induced sediment plume could be attributed to desorption from re-suspended sediments. This mode of exposure has the potential to be used in monitoring programmes.

A new organosilicon adsorbent for air-gas mixture purification

Natural zeolites (klinoptiolits) were treated with Onkosorb adsorbent (N,N′-bis(3-triethoxysilyl-propyl-thiocarbamide)) to attain greater nitrosamine (NA) and polycyclic aromatic hydrocarbon (PAH) adsorption capacity. The efficiency of volatile NA recovery rose from 30 to 77%; that of PAH recovery, from 20 to 63.7 %. The increased adsorption efficiency of the toxicants from an air-gas mixture was also reflected in biological indicators. Prolonged exposure of rats to the air-gas mixture (similar in composition to the air in industrial zones) led to a 25% reduction in the maximum rates of succinate oxidation and the efficiency of oxidative phosphorylation in liver mitochondria. The changes in the energetics of mitochondria were apparently associated with the action of the toxicants, as is indicated by a 22 % increase of P-450 cytochrome content in the liver tissue. An air-gas mixture passed through an Onkosorb adsorbent layer on zeolite did not produce any of the above changes in the mitochondrion energetics or the effect on P-450 cytochrome content in the liver tissue. We assume a high level of efficiency for Onkosorb adsorbent on zeolite in PAH and NA absorption.

Genotoxic and apoptotic effects of Goeckerman therapy for psoriasis

Goeckerman therapy (GT) for psoriasis is based on cutaneous application of crude coal tar [polycyclic aromatic hydrocarbons (PAH)] and exposure to ultraviolet radiation (UVR). PAH and UVR are mutagenic, carcinogenic and immunotoxic agents that promote apoptosis. We evaluated dermal absorption of PAH as well as the genotoxic and apoptotic effects of GT in 20 patients with psoriasis, by determining numbers of chromosomal abnormalities in peripheral lymphocytes, and levels of 1-hydroxypyrene (1-OHP), p53 protein and soluble FasL (sFasL) in urine and/or blood, before and after GT. Psoriasis Area and Severity Index (PASI) score was used to evaluate clinical efficacy of GT. Compared with pre-treatment levels, there was a significant increase in urine 1-OHP, indicating a high degree of dermal absorption of PAH (P < 0.01). We also found a significant increase in the number of chromosomal abnormalities in peripheral blood lymphocytes (P < 0.001), suggesting that GT is genotoxic; significantly increased p53 protein in plasma (P < 0.05), an indicator of cell response to DNA damage; and significantly increased sFasL in serum (P < 0.01), an indicator of apoptosis. The PASI score was significantly decreased after GT (P < 0.001), confirming clinical benefit of this treatment. Our results demonstrate high dermal absorption of PAH during GT and provide evidence that GT promotes genotoxicity and apoptosis.

On the Research of adsorption of Polycyclic Aromatic Hydrocarbons (Phenanthrene) in Soil-Groundwater in Zhangshi Irrigation District

The thesis mainly studies the dynamic variation features of absorption of polycyclic aromatic hydrocarbons (PAHs) in soil and groundwater of Zhangshi irrigation district in southwest part of Shengyang City of China. On the basis of the field inspection on hydrogeochemistry of Zhangshi irrigation district, we choose four typical sites, taking samples from surface soil layer, sub-vadose zone and acquifer to do experiment of dynamic successive absorption on phenanthrene as the typical pollutant. And we also study the absorptional dynamics characteristics of phenanthrene in soil and groundwater. Linear models and Freundlich models are also used to simulate the absorption isotherm. The results show two outstanding phases of phenanthrene adsorption in underground environment: the quick linear partition phase and the slow nonlinear adsorption phase. Phenanthrene adsorption is in positive correlation with the organic contents in soil. Whereas the balance time of adsorption is in negative correlation with the organic contents in soil. Since the adsorption curve is a typical “S” type in the organic-rich top soil, the tendency shows the likeliness of multilayer adsorption. The partition function of solid phase and liquid phase of phenanthrene in the relatively poor organic lower vadose zone shows certain linear relationship. The adsorption of phenanthrine in organic-poor acquifer soil particles belongs to linear adsorption. The relevant factors R are all above 0.9627.

Bioavailability of Polycyclic Aromatic Hydrocarbons (PAHs) from Soil and Hay Matrices in Lactating Goats

This experiment was aimed at determining the bioavailability of three polycyclic aromatic hydrocarbons (PAHs) in goats: phenanthrene, pyrene, and benzo[a]pyrene. A Latin square design procedure was carried out involving three alpine lactating goats and three PAH-contaminated matrices (soil, hay, and oil as a control). Milk and urine samples were collected to assess PAH and hydroxy-PAH excretion kinetics and to compare the carry-over rates for the different matrices. PAHs were found to be excreted mainly in urine; metabolite concentrations were about 20 times higher in urine than in milk. 1-Hydroxypyrene was the major metabolite in both body fluids (8000 ng/mL urine and 450 ng/mL milk); it may be considered as a valuable indicator of the ruminant exposure to PAHs. Apparent absorption of PAHs estimated by the metabolite excretion in urine and milk reached 34% for pyrene from soil, and the bioavailability of soil-bound PAHs was found to be similar to the bioavailability of PAHs from the other matrices.

Determination of total and available fractions of PAHs by SPME in oily wastewaters: overcoming interference from NAPL and NOM

Polycyclic aromatic hydrocarbons (PAHs) are often found in oily wastewaters. Their presence is usually the result of human activities and has a negative effect on the environment. One important step in addressing this problem is to evaluate the effectiveness of PAH removal by biological processes since these are the most cost-effective treatments known today. Many techniques are presently available for PAH determination in wastewaters. Solid phase microextracion (SPME) is known to be one of the most effective techniques for this purpose. When analyzing complex matrices with substances such as natural organic matter (NOM) and non-aqueous phase liquids (NAPL), it is important to differentiate the free dissolved PAH from matrix-bonded PAH. PAHs associated with the bonded fraction are less susceptible to biological treatment. The present study concerns the development of a simple and suitable methodology for the determination of the freely dissolved and the total fraction of PAHs present in oily wastewaters. The methodology was then applied to an oily wastewater from a fuel station retention basin. Headspace SPME was used for analyzing PAH since the presence of a complex or dirty matrix in direct contact with the fiber may damage it. Four model PAHs-anthracene, fluorene, phenanthrene, and pyrene-were analyzed by GC-MS. Negligible depletion SPME technique was used to determine the free fraction. Total PAH was determined by enhancing the mass transfer from the bonded phase to the freely dissolved phase by temperature optimization and the use of the method of standard additions. The PAH absorption kinetics were determined in order to define the optimal sampling conditions for this method. The fitting of the experimental data to a mathematical model was accomplished using Berkeley Madonna software. Humic acid and silicon oil were used as model NOM and NAPL, respectively, to study the effect of these compounds on the decrease of SPME response. Then, the method was evaluated with wastewater from a fuel station spill retention basin. The SPME kinetic parameters-k (1) (uptake rate), k (2) (desorption rate), and K (SPME) (partition coefficient)-were determined from experimental data modeling. The determination of the free fraction required 15-min sampling to ensure that PAH depletion from sample was below 1%. For total PAH, a 30-min extraction at 100 degrees C ensured the maximum signal response in the GC-MS. For the determination of free and total PAHs, extractions were performed before reaching the SPME equilibrium. The wastewater used in this study had no free fraction of the analyzed PAHs. However, the four studied PAHs were found when the method for total PAH was used. The addition of NOM and NAPL dramatically decreased the efficiency of the SPME. This decrease was the result of a greater partition of the PAHs to the NAPL and NOM phases. This fact was also observed in the analysis of the fuel station spill retention basin, where no free PAH was measured. However, using the method of standard addition for the determination of total PAH, it was possible to quantify all four PAHs. The method developed in the present study was found to be adequate to differentiate between free and total PAH present in oily wastewater. It was determined that the presence of NOM and NAPL had a negative effect on SPME efficiency. The presence of binding substances had a great influence on SPME kinetics. Therefore, it is of extreme importance to determine their degree of interference when analyzing oily wastewaters or results can otherwise be erroneous. Other factors influencing the total PAH determinations should be considered in further studies.

Absorption of polycyclic aromatic hydrocarbons by Pinus bark: Analytical method and use for environmental pollution monitoring in the Palermo area (Sicily, Italy)

In the light of using biomaterial as pollutants sorbents for the environmental biomonitoring, we report here the results of the absorption of polycyclic aromatic hydrocarbons (PAHs) by pine bark. Quantitative analysis of 19 different polycyclic aromatic compounds was performed, after Soxhlet extraction in dichloromethane, by means GC–MS technique. Pinus was chosen due to its wide distribution in the Mediterranean area. The passive absorption of PAH by pine bark in the metropolitan areas allowed us to evaluate the air quality of Palermo. The obtained results showed a very high range of PAHs concentrations, from 33 μg/kg (bark dry weight), as ΣPAHs, at the control site to 1015 μg/kg along a road with high traffic flow.

Standardized Investigation of Percutaneous Absorption of Bitumen Emission in Humans

The potential for percutaneous absorption of aerosols and vapors of bitumen was investigated in human beings using an experimental chamber. Commercial bitumen B 65 was used to generate the bitumen emissions. The system used for air sampling and analysis permitted the separate evaluation of aerosols and vapors as well as the polycyclic aromatic hydrocarbon (PAH) concentrations and contents, respectively. n = 10 male nonsmokers were exposed for 8 h with and two of them in addition without a powered air purifying respirator (PAPR). Quantification of the percutaneous and combined inhaled/percutaneous absorption was related to the biological monitoring of the PAH metabolites pyrene, chrysene, and phenanthrene in urine. The bitumen emissions in chamber were determined to be 20.4 mg/m 3 with a vapor content of about 88%. Two subjects stressed by inhalation and percutaneous contact with bitumen showed PAH absorption values of approximately 57% for pyrene and chrysene and about 50% for phenanthrene.

Adsorption and absorption of polycyclic aromatic hydrocarbons to rice roots

Rice roots and surrounding air, soil and water samples were collected for polycyclic aromatic hydrocarbon (PAH) analysis. The rice roots were separated into lateral roots and nodal roots, and the PAH concentration in the former was found to be higher than that in the latter. In addition, root physiological characteristics including root biotic mass, root lipid content and specific surface area are also discussed. When normalizing the total, adsorption and absorption PAH fractions on a dry root weight basis to root biomass, root lipid, and surface area bases respectively, the differences between PAHs in the two types of roots diminished by 2 to 3 times on average. Results from sequential extraction indicated that PAHs were more easily absorbed by interior rice roots than adsorbed on the surface. In addition, more than 60% of total PAHs accumulated in root tissue for both lateral and nodal roots. However, the results were highly related to the solvent used, extraction time and methodology. Correlation analysis between bioconcentration factors (root over environment) and K OA, K OW showed water to be more significant for PAH adsorption in rice roots than other environmental media.

Development of a Biokinetic Model to Evaluate Dermal Absorption of Polycyclic Aromatic Hydrocarbons from Soil

The high carcinogenic potency of polycyclic aromatic compounds often results in the dermal pathway indicating significant risk to human health at sites with contaminated soils, resulting in the establishment of conservative, risk-based remediation goals. The sorptive properties of soil sequester chemical contaminants, making them less available for uptake by receptors. Recent studies of desorption from soil indicate that PAHs follow a nonlinear desorption pattern that can be estimated by two phases: a rapid, followed by a slow, desorbing fraction. In this work, we adapt a fugacity-based model to evaluate the availability of polycyclic aromatic hydrocarbons (PAHs) from soil to human skin. Incorporating two-site desorption kinetics into the fugacity model renders a less available fraction of chemical in soil for absorption, decreasing predicted dermal uptake. We explore the impacts to dermal bioavailability of removing the “fast-desorbing” fraction of chemical from the soil. The model predicts uptake within a factor of two when compared with experimental data on dermal uptake. Soil moisture and soil loading rates emerge as potential limiting variables; however, the model is most sensitive to the size of the fast desorbing fraction of chemical in soil