Air Partition Coefficients Research Articles

Exhaled Breath Condensates: Analyzing the Expiratory Plume

Exhaled Breath Condensates: Analyzing the Expiratory Plume

Predicting blood:air partition coefficients using basic physicochemical properties

Quantitative Property Property Relationships (QPPRs) for human and rat blood:air partition coefficients (PBAs) have been derived, based on vapour pressure (Log(VP)), the octanol:water partition coefficient (Log(KOW)) and molecular weight (MW), using partial least squares multilinear modelling. These parameters are all included in the standard data to be submitted under REACH. The chemical dataset consisted of volatile organic chemicals, principally aliphatic hydrocarbons, benzene derivatives with one aromatic ring, and ethers, with and without halogen atoms. Other chemicals represented were cyclic hydrocarbons and carbonic acid esters. Separate rat and human models were derived, as well as mixed ones. Log(VP) and Log(KOW) contributed most to the prediction of Log(PBA) in the three-parameter model, while the contribution of MW was relatively small. Still, the three-parameter model differed significantly from the two-parameter model and performed better. Its performance was comparable to that of models published in public literature, which are based on more complex molecular parameters or on measured olive:oil air and saline/water:air partition coefficients. Since, based on the available data for humans, rats, mice, dogs and rabbits, existence of interspecies differences of PBAs cannot be clearly excluded, the use of separate models for each species is advisable.Concluding, the three-parameter human model Log(PBA)=6.96−1.04 Log(VP)−0.533 Log(KOW)−0.00495MW and the three-parameter rat model 6.16−0.888 Log(VP)−0.521 Log(KOW)−0.00201MW provide robust and reliable models for predicting PBA values of volatile organic chemicals using commonly available chemical properties of molecules.

Measurement of isoprene solubility in water, human blood and plasma by multiple headspace extraction gas chromatography coupled with solid phase microextraction

The aim of this study was to determine the solubility (liquid-to-air ratios) of isoprene in water, human blood and plasma. To this end, an experimental setup combining multiple headspace extraction, solid phase microextraction and gas chromatography–mass spectrometry was applied. The water:air partition coefficients of isoprene were determined for the temperature range 4.5–37 °C and amounted to 1.171–0.277 (g mLl−1) (g mLa−1)−1. On the basis of these data, the enthalpy of volatilization was calculated as 29.46 ± 2.83 kJ mol−1. The blood:air partition coefficients at 37 °C were determined for ten normal healthy volunteers spread around a median value of 0.95 ± 0.09 (g mLl−1) (g mLa−1)−1 and were approximately 16% lower than the plasma:air partition coefficients (1.11 ± 0.2). The applied methodology can be particularly attractive for solubility studies targeting species at very low concentrations in the solution, i.e. when headspace sample enrichment is necessary to provide sufficient measurement sensitivity and reliability. This can be especially helpful if environmental or physiological solute levels have to be considered.

Beyond phthalates: Gas phase concentrations and modeled gas/particle distribution of modern plasticizers

The ongoing health debate about polymer plasticizers based on the esters of phthalic acid, especially di(2-ethylhexyl) phthalate (DEHP), has caused a trend towards using phthalates of lower volatility such as diisononyl phthalate (DINP) and towards other acid esters, such as adipates, terephthalates, citrates, etc. Probably the most important of these so-called “alternative” plasticizers is diisononyl cyclohexane-1,2-dicarboxylate (DINCH). In the indoor environment, the continuously growing market share of this compound since its launch in 2002 is inter alia apparent from the increasing concentration of DINCH in settled house dust. From the epidemiological point of view there is considerable interest in identifying how semi-volatile organic compounds (SVOCs) distribute in the indoor environment, especially in air, airborne particles and sedimented house dust. This, however, requires reliable experimental concentration data for the different media and good measurements or estimates of their physical and chemical properties. This paper reports on air concentrations for DINP, DINCH, diisobutyl phthalate (DIBP), diisobutyl adipate (DIBA), diisobutyl succinate (DIBS) and diisobutyl glutarate (DIBG) from emission studies in the Field and Laboratory Emission Cell (FLEC). For DINP and DINCH it took about 50 days to reach the steady-state value: for four months no decay in the concentration could be observed. Moreover, vapor pressures p 0 and octanol–air partitioning coefficients K OA were obtained for 37 phthalate and non-phthalate plasticizers from two different algorithms: EPI Suite and SPARC. It is shown that calculated gas/particle partition coefficients K p and fractions can widely differ due to the uncertainty in the predicted p 0 and K OA values. For most of the investigated compounds reliable experimental vapor pressures are not available. Rough estimates can be obtained from the measured emission rate of the pure compound in a microchamber as is shown for di-n-butyl phthalate (DnBP), di(2-ethylhexyl) adipate(DEHA), tri(octyl) trimellitate (TOTM) and DEHP.

QSAR models of the inhalation toxicity of organic compounds

Results of QSAR research for chemical inhalation toxicity are presented. Data on the inhalation toxicity of organic compounds (403 chemicals) with respect to rats (4-h exposure) were taken from the Registry of Toxic Effects of Chemical Substances (RTECS). Among these, 28 inert chemicals with nonspecific toxicity were selected. Regression models were formed for all these compounds. The QSAR models were constructed using two approaches based on (i) experimental values of octanol—air partition coefficients and (ii) molecular physicochemical descriptors calculated by the HYBOT program. The best computer model was obtained on the basis of molecular physicochemical descriptors. A comparison of the inhalation toxicity of all examined compounds with the base nonspecific toxicity identified additional compounds with toxicity close to the base level that were not inert; a class of compounds with substantially greater toxicity (specific toxicants); and a class of compounds with substantially less toxicity due to metabolism. Satisfactory classification and regression QSAR models were obtained for 135 substances in the examined set with similar structures.

An assessment of the impact of physico-chemical and biochemical characteristics on the human kinetic adjustment factor for systemic toxicants

The objective of this study was to evaluate the magnitude of the human kinetic adjustment factor (HKAF) as a function of physico- and bio-chemical characteristics impacting the systemic clearance of chemicals. This factor is intended to replace the default value of 3.16 in non-cancer risk assessments and aims at accounting for interindividual variability in toxicokinetics. A steady-state algorithm was used to compute the internal dose metrics (blood concentration ( C blood) and rate of metabolite produced/L liver (RAM)) of hypothetical chemicals in neonates, adults, elderly, and pregnant women. After evaluating the algorithm with chemical-specific experimental data, C blood and RAM were calculated for hypothetical chemicals exhibiting blood:air partition coefficients (Pb) between 1 and 10,000 and hepatic extraction ratios in the average adult ( E) between 0.01 and 0.99. Based on Monte Carlo simulation results, HKAF values were computed as the ratio of the 95th percentile value for each subpopulation to the 50th percentile value in adults. The highest HKAF among those obtained for each subpopulation was reported in route-, pathway-, and dose metric-specific HKAF matrices as a function of Pb and E. These matrices allowed the recognition of cases where the default HKAF could be exceeded, and these occurred in neonates based on C blood in two situations. First, when the average adult-to-neonate ratio of body weight-adjusted systemic clearance was at least equal to 2.2 for a given systemic exposure (i.e., for CYP1A2 substrates only). Second, when E = 0.01–0.2 and Pb ≥ 300 or when E = 0.3–0.7 and Pb ≥ 100 for inhalation exposures to CYP2E1 substrates, with comparable values for the other substrates (higher for CYP1A2). Overall, this study showed the dependency of the HKAF on the dose metrics, chemical characteristics, metabolic pathways, and subpopulations considered.

Ubiquitous Net Volatilization of Polycyclic Aromatic Hydrocarbons from Soils and Parameters Influencing Their Soil−Air Partitioning

Soils are a major reservoir of organic pollutants, and soil-air partitioning and exchange are key processes controlling the regional fate of pollutants. Here, we report and discuss the soil concentrations of polycyclic aromatic hydrocarbons (PAHs), their soil fugacities, the soil-air partition coefficients (K(SA)) and soil-air gradients for rural and semirural soils, in background areas of N-NE Spain and N-NW England. Different sampling campaigns were carried out to assess seasonal variability and differences between sampling sites. K(SA) values were dependent on soil temperature and soil organic quantity and type. Soil fugacities of phenanthrene and its alkyl homologues were 1-2 orders of magnitude higher than their ambient air fugacities for all sampling sites and periods. The soil to air fugacity ratio was correlated with soil temperature and soil redox potential. Similar trends for other PAHs were found but with lower fugacity ratios. The ubiquitous source of PAHs from background soils to the atmosphere found in all temperate regions in different seasons provides an indirect evidence of potential in situ generation of two to four ring PAHs and their alkyl homologues in the surface soil. We discuss this hypothetical biogenic source and other potential processes that could drive the high soil to air fugacity ratios of some PAHs.

Atmospheric Concentrations and Phase Partitioning of Polycyclic Aromatic Hydrocarbons in Izmir, Turkey

Ambient air polycyclic aromatic hydrocarbon (PAH) samples were collected at a suburban (n = 63) and at an urban site (n = 14) in Izmir, Turkey. Average gas-phase total PAH (∑14PAH) concentrations were 23.5 ng m−3 for suburban and 109.7 ng m−3 for urban sites while average particle-phase total PAH concentrations were 12.3 and 34.5 ng m−3 for suburban and urban sites, respectively. Higher ambient PAH concentrations were measured in the gas-phase and ∑14PAH concentrations were dominated by lower molecular weight PAHs. Multiple linear regression analysis indicated that the meteorological parameters were effective on ambient PAH concentrations. Emission sources of particle-phase PAHs were investigated using a diagnostic plot of fluorene (FLN)/(fluorine + pyrene; PY) versus indeno[1,2,3-cd]PY/(indeno[1,2,3-cd]PY + benzo[g,h,i]perylene) and several diagnostic ratios. These approaches have indicated that traffic emissions (petroleum combustion) were the dominant PAH sources at both sites for summer and winter seasons. Experimental gas–particle partition coefficients (KP) were compared to the predictions of octanol–air (KOA) and soot–air (KSA) partition coefficient models. The correlations between experimental and modeled KP values were significant (r2 = 0.79 and 0.94 for suburban and urban sites, respectively, p < 0.01). Octanol-based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. However, overall there was a relatively good agreement between the measured KP and soot-based model predictions.

Inherent and process-induced hydrophobicity influences aroma retention in fat-free dairy matrices

It was shown that both inherent and process-induced hydrophobicity can influence the aroma retention in fat-free dairy matrices. The extent and direction to which these parameters take effect depends on the composition of the dairy matrix as well as on the hydrophobicity (log P) of the aroma compounds. The phase ratio variation (PRV) method was used to determine the matrix–air partition coefficient K MG. For the hydrophobic aroma compound limonene, K MG increased when the ratio of casein protein to whey protein was increased in model milk, while the less hydrophobic ethyl hexanoate and the hydrophilic diacetyl remained unaffected. This was attributed to the hydrophobic character of the casein micelle. Upon acidification with glucono-δ-lactone, K MG of diacetyl decreased significantly while K MG of ethyl hexanoate and limonene slightly increased. This was attributed to the predominance of hydrophobic interactions in acidified dairy matrices, which were analysed via bonds analysis using destabilising buffer solutions.

Sorption of a diverse set of organic chemical vapors onto XAD-2 resin: Measurement, prediction and implications for air sampling

The wide-spread use of styrene–divinylbenzene-copolymeric resin (XAD-2) in air sampling necessitates a quantitative understanding of its sorption characteristics for organic chemicals. Inverse Gas Chromatography (IGC) was used to measure the sorption of a diverse set of 52 organic chemicals to XAD-2 at temperatures between 40 °C and 100 °C and at relative humidities between 0 and 87%. Even though relative humidity has been shown to influence sorption to other sorbents, it did not significantly influence most chemicals’ sorption to XAD-2, indicating that water does not form a strong physical barrier to sorption on XAD-2 at high relative humidity. The resin–air partition coefficients (KXAD) determined by IGC and the enthalpies of sorption derived from them were regressed against solute descriptors to derive poly-parameter Linear Free Energy Relationships (ppLFERs) which allow the estimation of KXAD for chemicals which are not sufficiently volatile to be amenable to IGC and for temperatures outside the experimental range. KXAD values at 20 °C estimated for a set of 296 chemicals for which solute descriptors are available, including polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides, indicate that for many of the substances commonly found in the atmosphere sorption is higher to XAD-2 than to poly-urethane foam, another popular air sampling sorbent.

Atmospheric polycyclic aromatic hydrocarbon concentrations and gas/particle partitioning at background, rural village and urban sites in the North China Plain

Gas and particle-phase polycyclic aromatic hydrocarbons (PAHs) were measured in air at a background site (Xiaolongmen), two rural village sites (Gubeikou and Donghe), and at an urban site (Beijing) in the North China Plain from September 2007 to August 2008. The annual average total PAH concentration in Donghe was 730.7 ± 608.0 ng/m 3 and 18.2, 3.0, and 1.8 times higher than Xiaolongmen, Gubeikou and Beijing, respectively. Gas/particle partitioning coefficients, K p, were calculated for each PAH and their relationship with the subcooled liquid vapor pressure p 0 l and octanol–air partition coefficients ( K oa) of the PAHs was investigated. At the rural (Gubeikou) and urban (Beijing) sites, the regression slopes of log K p versus log p 0 l were much steeper than −1, indicating that adsorption of PAHs to particulate matter dominated over absorption possibly because, at these sites, the freshly emitted particulate matter and PAHs had not yet reached equilibrium. However, gas/particle partitioning of PAHs approached equilibrium at the background site (Xiaolongmen) because of long-range transport and longer transport times of the PAHs. In addition, the partitioning between the gas and particle phases was studied according to three different models: the Junge–Pankow adsorption model, the K oa absorption model, and the dual organic matter absorption model combined with the soot carbon adsorption model. The Junge–Pankow model and K oa model both under-predicted our experimental K p values. However, the dual model fit our experimental K p values well. This suggests that PAH adsorption onto soot carbon and absorption into organic matter were both important for PAH gas/particle partitioning in the North China Plain.

Polybrominated diphenyl ethers (PBDEs) in indoor and outdoor window organic films in Izmir, Turkey

Polybrominated diphenyl ether (PBDE) concentrations of outdoor and indoor organic films on window glasses were measured at different locations (offices, laboratories, and homes in urban, suburban, rural, and industrial sites) in Izmir, Turkey. ∑ 7PBDE concentrations were dominated by technical penta and deca-BDE mixture components. Average total outdoor PBDE (∑ 7PBDE) concentrations for suburban, urban, and industrial sites were 43.5, 45.5, and 206 ng m −2, respectively. This spatial gradient (industrial > urban > suburban concentrations) was similar to one observed for ambient air concentrations recently in Izmir, Turkey. The highest concentrations measured in the industrial area were attributed to the significant PBDE emissions from several steel plants located in the area. Air-organic film partitioning modeling results have suggested that organic films can be used in conjunction with the dynamic uptake model to approximate the gas-phase ambient air concentrations. Modeling results have also indicated that congeners in the gas-phase with very large octanol–air partition coefficients (i.e., BDE-154, -153, and -209) will require several months to approach equilibrium with the surface films. This finding may have important implications for gas-particle and gas-film partitioning, transport, and photolytic degradation of atmospheric PBDEs.

Partition coefficients for nonane and its isomers in the rat

Jet Fuel 8 (JP-8) is a major fuel source used by US and NATO military. JP-8 is a complex mixture of aliphatic and aromatic isomers of hydrocarbons. Tissue/blood partition coefficient (PC) values are chemical-specific parameters used in modeling the kinetic behavior of chemicals. The partition coefficient values for n-alkanes tend to increase with the increasing carbon number, but less is known about the trend for isomers of n-alkanes. PC values were obtained for the n-alkane nonane (C9) and five of its isomers, namely 3-methyloctane, 4-ethylheptane, 2,3-dimethylheptane, 2,2,4-trimethylhexane, 2,2,4,4-tetramethylpentane. The blood:air and tissue:air PC values correlated with the published log octanol/water (O:W) PC values for n-nonane and its isomers. Experimentally determined blood:air and tissue:air PC values for n-nonane with the largest O:W value were greatest and smallest for the isomer 2,2,4,4-tetramethylpentane with the lowest O:W value. As expected the fat tissue had the highest PC values and muscle the lowest for n-nonane and its isomers. For each tissue, a linear relationship was observed between the tissue/blood PC values for the isomers of n-nonane and n-nonane. This suggests that tissue/blood PC values for all isomers of an alkane could be estimated using data collected from only a sub-set of alkanes of equal carbon number. These reported tissue/blood PC values will support the development of a jet fuel physiologically-based pharmacokinetic (PBPK) model.

Quantitative property–property relationships for computing Occupational Exposure Limits and Vapour Hazard Ratios of organic solvents

Vapour Hazard Ratio (VHR) is used in solvent substitution to select the best replacement option regarding overexposure potential of solvents. However, VHR calculations are limited by the availability of Occupational Exposure Limits (OELs). The overall objective of this study was to develop quantitative property–property relationship (QPPR) approaches for computing OELs, in view of supporting the derivation of VHRs for solvents without OELs. QPPRs were developed for estimating OELs using a database of 88 solvents which have health-based Time-Weighted Average (TWA) OELs published by the American Conference of Governmental Industrial Hygienists (ACGIH). Three surrogates of biotic lipid : air partition coefficients [n-octanol : air (Koa ), olive oil : air (Koila ) and fat : air (Kfa )] were selected for evaluating the descriptive/predictive relationship with OELs for solvents with local modes of action. For solvents with systemic modes of action, the prediction of OEL needs to consider quantitative differences in toxicokinetics (i.e. kinetic variability factor, KVF) and toxicological potency (i.e. effective internal concentration, EIC). The n-octanol : water (Kow ), the oil : water (Koilw ) and the fat : water (Kfw ) partition coefficients were selected for evaluating the relationship with EICs. For local modes of action, Koa is the most accurate predictor of OELs [OEL (ppm) = ; n = 21, r 2 = 0.71, PRESS/SSY = 0.36, F = 45.5 with p < 0.001] and the mean (±SD) (range) of the recommended to predicted OELs was 1.04 ± 0.61 (0.2–2.5). For systemic modes of action, KVFs and EICs vary in a range from 0.73 to 41.4 µmol L−1 and 1.20–848 µmol L−1, respectively. Kow is an accurate predictor of calculated EICs [EIC (µmol L−1) = ; n = 27, r 2 = 0.88, PRESS/SSY = 0.12, F = 181 with p < 0.001] and 50% of the predicted OEL values were within a factor of two of the recommended TWA OELs. Overall, 61% and 87% of the predicted VHRs were within a factor of two and five, respectively, of the calculated VHRs. The QPPR models developed in this study represent potentially useful tools for estimating provisional OELs for solvents lacking such guideline values. These provisional OELs are developed only to support initial estimations of VHR for dealing with the challenge of solvent substitution where relative values rather than absolute values of OEL and vapour pressure guide the hygienist in making pragmatic decisions for managing occupational health hazards.

A passive sampling-based analytical strategy for the determination of volatile organic compounds in the air of working areas

An analytical methodology based on the use of a polyethylene layflat tube filled with activated carbon and Florisil (ACFL-VERAM) was employed for the passive sampling of volatile organic compounds (VOCs) in the air of working areas of packing industries. VOCs amount in the ACFL-VERAM sampler was directly determined through head-space-gas chromatography–mass spectrometry (HS-GC–MS) allowing a direct determination in only 20 min without the need of any previous treatment. Uptake parameters, like sampling rate ( R S) and sampler–air partition coefficient ( K SA), were determined for every studied VOC from adsorption isotherm data. Additionally, experimental equations have been proposed to predict R S and K SA from the octanol–air partition coefficients reported in the literature. The proposed methodology reaches method detection levels from 0.007 to 0.2 mg m −3 for the studied VOCs.

Evaluation of Tree Bark as a Passive Atmospheric Sampler for Flame Retardants, PCBs, and Organochlorine Pesticides

To investigate the relationship between the levels of persistent organic pollutants in tree bark (a passive sampler) and those in air and precipitation, tree bark and air and precipitation samples were collected during the same time period at the five U.S. Integrated Atmospheric Deposition Network (IADN) sites located in Great Lakes basin. The concentrations of polybrominated diphenyl ethers, Dechlorane Plus, decabromodiphenyl ethane, polychlorinated biphenyls, DDTs, and chlordanes were measured in these samples. Overall, the pollutant concentrations in tree bark are significantly related to the concentrations of these compounds in the air and precipitation collected where the tree was growing. Generally, the highest tree bark and air pollutant concentrations were observed at urban sites, and the lowest concentrations were observed at remote sites. The overall correlation between bark and atmospheric and precipitation concentrations for all the compounds measured in this study was highly significant (P < 0.0001) over 3-4 orders of magnitude. In addition, bark-air partition coefficients, measured for all the chemical categories in this study, were about 10(6), which was in good agreement with previously estimated bark-air partition coefficients for corresponding pollutant groups.

Determination and prediction of octanol–air partition coefficients of hydroxylated and methoxylated polybrominated diphenyl ethers

The octanol–air partition coefficient ( K OA) of 19 hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and 10 methoxylated polybrominated diphenyl ethers (MeO-PBDEs) were measured as a function of temperature using a gas chromatographic retention time technique. At room temperature (298.15 K), log K OA ranged from 8.30 for monobrominated OH/MeO-PBDEs to 13.29 for hexabrominated OH/MeO-PBDEs. The internal energies of phase change from octanol to air (Δ OA U) for 29 OH/MeO-PBDE congeners ranged from 72 to 126 kJ mol −1. Using partial least-squares (PLS) analysis, a statistically quantitative structure–property relationship (QSPR) model for log K OA of OH/MeO-PBDE congeners was developed based on the 16 fundamental quantum chemical descriptors computed by PM3 Hamiltonian, for which the Q cum 2 was about 0.937. The molecular weight ( Mw) and energy of the lowest unoccupied molecular orbital ( E LUMO) were found to be main factors governing the log K OA.

Prediction of gas collection efficiency and particle collection artifact for atmospheric semivolatile organic compounds in multicapillary denuders

A modeling approach is presented to predict the sorptive sampling collection efficiency of gaseous semivolatile organic compounds (SOCs) and the artifact caused by collection of particle-associated SOCs in multicapillary diffusion denuders containing polydimethylsiloxane (PDMS) stationary phase. Approaches are presented to estimate the equilibrium PDMS–gas partition coefficient ( K pdms) from a solvation parameter model for any compound, and, for nonpolar compounds, from the octanol–air partition coefficient ( K oa) if measured K pdms values are not available. These estimated K pdms values are compared with K pdms measured by gas chromatography. Breakthrough fraction was measured for SOCs collected from ambient air using high-flow (300 L min −1) and low-flow (13 L min −1) denuders under a range of sampling conditions (−10 to 25 °C; 11–100% relative humidity). Measured breakthrough fraction agreed with predictions based on frontal chromatography theory using K pdms and equations of Golay, Lövkvist and Jönsson within measurement precision. Analytes included hexachlorobenzene, 144 polychlorinated biphenyl congeners, and polybrominated diphenyl ethers 47 and 99. Atmospheric particle transmission efficiency was measured for the high-flow denuder (0.037–6.3 μm diameter), and low-flow denuder (0.015–3.1 μm diameter). Particle transmission predicted using equations of Gormley and Kennedy, Pich, and a modified filter model, agreed within measurement precision (high-flow denuder) or were slightly greater than (low-flow denuder) measured particle transmission. As an example application of the model, breakthrough volume and particle collection artifact for the two denuder designs were predicted as a function of K oa for nonpolar SOCs. The modeling approach is a necessary tool for the design and use of denuders for sorptive sampling with PDMS stationary phase.

Determination of Octanol−Air Partition Coefficients (KOA) of Fluorotelomer Acrylates, Perfluoroalkyl Sulfonamids, and Perfluoroalkylsulfonamido Ethanols

Octanol−air partition coefficients (KOA) for three fluorotelomer acrylates (6:2 FTA, 8:2 FTA, 10:2 FTA), two perfluoroalkyl sulfonamides (n-methyl perfluorooctane sulfonamide (MeFOSA), n-ethyl perfluorooctane sulfonamide (EtFOSA)), and two perfluoroalkyl sulfonamido ethanols (n-methyl perfluorooctane sulfonamido ethanol (MeFOSE), n-ethyl perfluorooctane sulfonamido ethanol (EtFOSE)) were determined over a temperature range from (278 to 313) K using a modified generator column method. The KOA values were calculated as the ratio of the target analyte concentrations in octanol to the target analyte concentrations in octanol saturated air. Calibrated log KOA values at 298 K ranged from 4.5 (6:2 FTA) to 6.7 (EtFOSE). Log KOA values decreased with increasing temperature and increased in the order of 6:2 FTA, 8:2 FTA, 10:2 FTA, MeFOSA, MeFOSE, EtFOSA, EtFOSE. The combined uncertainty of the method applied ranged from 5.1 % (6:2 FTA) to 17.6 % (MeFOSA). The relative extended uncertainty (P = 95 %) ranged from 11....

Gas/particle partitioning of atmospheric PCDD/Fs in a satellite town in Eastern China

Gas/particle partitioning of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) in ambient air was investigated in a satellite town in Eastern China from April 2007 to January 2008 comprehending large temperature variations (from 3 to 34 °C, daily average). Molecular weight, molecular structure and ambient temperatures are the three major factors that govern the gas/particle partitioning of atmospheric PCDD/Fs throughout the year. Generally, good agreements were obtained (except for winter) between measured particulate fractions and theoretical estimates of both the Junge–Pankow adsorption model and Harner Bidleman absorption model using different sets of subcooled liquid vapor pressure ( P L o ) and octanol–air partition coefficient ( K oa ) , respectively. Models utilizing P L o estimates, derived from gas chromatographic retention indices (GC-RIs), are more accurate than that of entropy-based. Moreover, during winter, the K oa -based model using the GC-RIs approach performs better on lower chlorinated PCDD/Fs than that of P L o -based. Furthermore, possible sources of mismatch between measured and predicted values in winter (3–7 °C) were discussed. Gas adsorption artifact was demonstrated to be of minor importance for the phenomena observed. On the other hand, large deviations of slopes ( m r ) and intercepts ( b r ) in log K p vs. log P L o ( Pa ) / log K oa plots from theoretical values are observed in the literature data and these are found to be linearly correlated with ambient temperatures ( P < 0.001 ) in this study. This indicates that the non-equilibrium partitioning of PCDD/Fs in winter may be significantly influenced by the colder temperatures that may have slowed down the exchange between gaseous and particulate fractions.