Polyurethane Foam Disks Research Articles

Wastewater Treatment Plant and Landfills as Sources of Polyfluoroalkyl Compounds to the Atmosphere

Polyfluoroalkyl compounds (PFCs) were determined in air around a wastewater treatment plant (WWTP) and two landfill sites using sorbent-impregnated polyurethane foam (SIP) disk passive air samplers in summer 2009. The samples were analyzed for five PFC classes (i.e., fluorotelomer alcohols (FTOHs), perfluorooctane sulfonamides (FOSAs), sulfonamidoethanols (FOSEs), perfluoroalkyl sulfonic acids (PFSAs), and perfluoroalkyl carboxylic acids (PFCAs)) to investigate their concentration in air, composition and emissions to the atmosphere. ∑PFC concentrations in air were 3-15 times higher within the WWTP (2280-24 040 pg/m(3)) and 5-30 times higher at the landfill sites (2780-26 430 pg/m(3)) compared to the reference sites (597-1600 pg/m3). Variations in the PFC pattern were observed between the WWTP and landfill sites and even within the WWTP site. For example, FTOHs were the predominant PFC class in air for all WWTP and landfill sites, with 6:2 FTOH as the dominant compound at the WWTP (895-12 290 pg/m(3)) and 8:2 FTOH dominating at the landfill sites (1290-17 380 pg/m(3)). Furthermore, perfluorooctane sulfonic acid (PFOS) was dominant within the WWTP (43-171 pg/m(3)), followed by perfluorobutanoic acid (PFBA) (55-116 pg/m(3)), while PFBA was dominant at the landfill sites (101-102 pg/m(3)). It is also noteworthy that the PFCA concentrations decreased with increasing chain length and that the emissions for the even chain length PFCAs outweighed emissions for the odd chain length compounds. Furthermore, highly elevated PFC concentrations were found near the aeration tanks compared to the other tanks (i.e., primary and secondary clarifier) and likely associated with increased volatilization during aeration that may be further enhanced through aqueous aerosol-mediated transport. ∑PFC yearly emissions estimated using a simplified dispersion model were 2560 g/year for the WWTP, 99 g/year for landfill site 1, and 1000 g/year for landfill site 2. These results highlight the important role of WWTPs and landfills as emission sources of PFCs to the atmosphere.

Global Distribution of Linear and Cyclic Volatile Methyl Siloxanes in Air

The global distribution of linear and cyclic volatile methyl silxoanes (VMS) was investigated at 20 sites worldwide, including 5 locations in the Arctic, using sorbent-impregnated polyurethane foam (SIP) disk passive air samplers. Cyclic VMS are currently being considered for regulation because they are high production volume chemicals that are potentially persistent, bioaccumulative, and toxic. Linear and cyclic VMS (including L3, L4, L5, D3, D4, D5, and D6) were analyzed for in air at all urban, background, and Arctic sites. Concentrations of D3 and D4 are significantly correlated, as are D5 and D6, which suggests different sources for these two pairs of compounds. Elevated concentrations of D3 and D4 on the West coast of North America and at high elevation sites suggest these sites are influenced by trans-Pacific transport, while D5 and D6 have elevated concentrations in urban areas, which is most likely due to personal care product use. Measured concentrations of D5 were compared to modeled concentrations generated using both the Danish Eulerian Hemispheric Model (DEHM) and the Berkeley-Trent Global Contaminant Fate Model (BETR Global). The correlation coefficients (r) between the measured and modeled results were 0.73 and 0.58 for the DEHM and BETR models, respectively. Agreement between measurements and models indicate that the sources, transport pathways, and sinks of D5 in the global atmosphere are fairly well understood.

A passive air sampler for characterizing the vertical concentration profile of gaseous phase polycyclic aromatic hydrocarbons in near soil surface air

Air–soil exchange is an important process governing the fate of polycyclic aromatic hydrocarbons (PAHs). A novel passive air sampler was designed and tested for measuring the vertical concentration profile of 4 low molecular weight PAHs in gaseous phase (PAH LMW4) in near soil surface air. Air at various heights from 5 to 520 mm above the ground was sampled by polyurethane foam disks held in down-faced cartridges. The samplers were tested at three sites: A: an extremely contaminated site, B: a site near A, and C: a background site on a university campus. Vertical concentration gradients were revealed for PAH LMW4 within a thin layer close to soil surface at the three sites. PAH concentrations either decreased (Site A) or increased (Sites B and C) with height, suggesting either deposition to or evaporation from soils. The sampler is a useful tool for investigating air–soil exchange of gaseous phase semi-volatile organic chemicals.

Air concentrations and particle–gas partitioning of polyfluoroalkyl compounds at a wastewater treatment plant

Environmental contextPolyfluoroalkyl compounds, widely used chemicals in consumer and industrial products, are global pollutants in the environment. Transport mechanisms and environmental pathways of these compounds, however, are not yet fully understood. We show that a wastewater treatment plant can be an important source for polyfluoroalkyl compounds to the atmosphere where they have the potential to be transported long distances. AbstractAn air sampling campaign was conducted at a wastewater treatment plant (WWTP) to investigate air concentrations and particle–gas partitioning of polyfluoroalkyl compounds (PFCs). Samples were collected at an aeration tank and a secondary clarifier using both active high volume samplers and passive samplers comprising sorbent-impregnated polyurethane foam (SIP) disks. Water to air transport of PFCs was believed to be enhanced at the aeration tank owing to aerosol-mediated transport caused by surface turbulence induced by aeration. Mean air concentrations of target PFCs at the aeration tank were enriched relative to the secondary clarifier by factors of ~19, ~4 and ~3 for ∑fluorotelomer alcohols (FTOHs) (11 000 v. 590 pg m–3), ∑perfluorooctane sulfonamides & perfluorooctane sulfonamidoethanols (FOSAs & FOSEs) (120 v. 30 pg m–3) and ∑perfluoroalkyl carboxylates & perfluoroalkyl sulfonates (PFCAs & PFSAs) (4000 v. 1300 pg m–3) respectively. The particle associated fraction in the atmosphere increased with increasing chain length for PFCAs (from 60 to 100%) and PFSAs were predominantly bound to particles (~98%). Lower fractions on particles were found for FTOHs (~3%), FOSAs (~30%) and FOSEs (~40%). The comparison of the active and passive air sampling showed good agreement.

Seasonal and Spatial Variations of Air Concentrations of Polycyclic Aromatic Hydrocarbons in Northeastern Chinese Urban Region

Polyurethane foam disk passive air samplers were deployed along an urban-rural-background transect in a northeastern Chinese region (Harbin) to investigate the spatial and seasonal variations of polycyclic aromatic hydrocarbons (PAHs). The ∑₁₆PAHs concentrations [ng/(sample·day)] were high at urban sites (315 ± 206), followed by rural sites (222 ± 160), suburban site (142 ± 114) and background site (128 ± 107). The urban fractionation effect was observed along the transect with increasing proportions for low molecular weight PAHs and decreasing proportions for high molecular weight PAHs. PAHs were found to be higher in winter and spring than in summer and autumn, most likely due to the combustion of coal and biomass for domestic heating. Sources of PAHs were investigated by principal component analysis in combination with diagnostic ratios, which both indicated that pyrogenic sources were the main sources of PAHs in the air of Harbin, China.

Assessing seasonal and spatial trends of persistent organic pollutants (POPs) in Indian agricultural regions using PUF disk passive air samplers

The first survey of persistent organic pollutant (POP) concentrations in air across several Indian agricultural regions was conducted in 2006–2007. Passive samplers comprising polyurethane foam (PUF) disks were deployed on a quarterly basis at seven stations in agricultural regions, one urban site and one background site. The project was conducted as a sub-project of the Global Atmospheric Passive Sampling (GAPS) Network. In addition to revealing new information on air concentrations of several organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), the study has demonstrated the feasibility of conducting regional-scale monitoring for POPs in India using PUF disk samplers. The following analytes were detected with relatively high concentrations in air (mean for 2006 and 2007, pg/m3): α- and γ-hexachlorocyclohexane (HCH) (292 and 812, respectively); endosulfan I and II (2770 and 902, respectively); p,p′-DDE and p,p′-DDT (247 and 931, respectively); and for the sum of 48 PCBs, 12,100 (including a site with extremely high air concentrations in 2007) and 972 (when excluding data for this site).

Polyfluorinated Compounds in Residential and Nonresidential Indoor Air

Indoor air concentrations of fifteen volatile per- and polyfluorinated compounds (PFCs) (five fluorotelomer alcohols (FTOHs), three fluorotelomer acrylates (FTAs), three perfluorinated sulfonamido ethanols (FASEs), and three perfluorinated sulfonamides (FASAs)) were determined in residential and nonresidential indoor air environments. Air samples were taken with passive samplers, consisting of XAD-4 impregnated polyurethane foam (PUF) disks in steel housings. Impregnated PUF disks were extracted by fluidized bed extraction (FBE) using methyl-tert-butyl ether/acetone (1:1) and analyzed by gas chromatography-mass spectrometry. Total PFC indoor air concentrations ranged from 8.2 to 458 ng m(-3). Individual PFC concentrations were between 42 pg m(-3) (6:2 FTA) and 209 ng m(-3) (8:2 FTOH). Concentrations of total FTOHs, FTAs, and FASAs + FASEs ranged from 0.2 to 152 ng m(-3) (FTAs), from 3.3 to 307 ng m(-3) (FTOHs), and from 4.4 to 148 ng m(-3) (FASAs + FASEs). Most elevated individual, group, and total PFC concentrations were detected in two stores selling outdoor equipment, one furniture shop, and one carpet shop. Indoor air concentrations were several orders of magnitude higher than published outdoor air concentrations indicating indoor air environments as sources for PFCs to the atmosphere. Concentrations were used to estimate human exposure to investigated PFCs.

In vitro reconstruction of a three-dimensional mouse hematopoietic microenvironment in the pore of polyurethane foam

Hematopoietic stem cells exist in specific niches in the bone marrow, and generate either more stem cells or differentiated hematopoietic progeny. In such microenvironments, cell-cell and cell-matrix interactions are as important as soluble factors such as cytokines. To provide a similar environment for in vitro studies, a three-dimensional culture technique is necessary. In this manuscript, we report the development of a three-dimensional culture system for murine bone marrow mononuclear cells (mBMMNCs) using polyurethane foam (PUF) as a scaffold. The mBMMNCs were inoculated into two kinds of PUF disks with different surface properties, and cultured without exogenous growth factors. After seeding the inside of the PUF pores with mBMMNCs, PUF disks were capable of supporting adherent cell growth and continuous cell production for up to 90days. On days 21-24, most nonadherent cells were CD45 positive, and some of the cells were of the erythroid type. From comparisons of the cell growth in each PUF material, the mBMMNC culture in PUF-W1 produced more cells than the PUF-R4 culture. However, the mBMMNC culture in PUF-W1 had no advantages over PUF-R4 with regard to the maintenance of immature hematopoietic cells. The results of scanning electron microscopy and colony-forming assays confirmed the value of the different three dimensional cultures.

Global Pilot Study of Legacy and Emerging Persistent Organic Pollutants using Sorbent-Impregnated Polyurethane Foam Disk Passive Air Samplers

Sorbent-impregnated polyurethane foam (SIP) disk passive air samplers were deployed alongside polyurethane foam (PUF) disk samplers at 20 sites during the 2009 spring sampling period of the Global Atmospheric Passive Sampling (GAPS) Network. The SIP disk samplers consisted of PUF disks impregnated with finely ground XAD-4 resin. The addition of XAD-4 greatly improves the sorptive capacity of the PUF disk samplers for more volatile and polar chemicals, and allows for linear-phase sampling over several weeks for these compounds. The SIP and PUF disks were analyzed for polychlorinated biphenyls (PCBs), neutral polyfluoroalkyl compounds (PFCs), and ionic PFCs. Correlations between sampler-derived air concentrations for PCBs in the PUF and SIP disks samplers were significant (p < 0.05). The SIP disks effectively captured 4-50% more of the low molecular weight PCBs than the PUF disks samplers, and the PUF disks also had limitations for time-weighted passive sampling of neutral PFCs in air. Theoretical uptake curves for PUF disks showed rapid equilibration occurring in just hours for 8:2 FTOH and in a few days for MeFOSE, while theoretical curves for SIP disks showed superior sampling profiles for the neutral PFCs. PFCs were measured on SIP disks at all sites with 8:2 FTOH being the dominant compound detected and urban centers (n = 3) having the highest total neutral PFC concentrations ranging from 51.7 to 248 pg/m(3). A positive correlation was found between the FTOHs and FOSAs/FOSEs (p < 0.001, Pearson correlation) indicating similar contamination sources. The SIP disk appears to be a promising passive air sampler for measuring both emerging and legacy POPs on a global scale. They can also be used as a complement to the PUF disk sampler for capturing broader classes of compounds, or as a replacement for PUF disks entirely, especially when longer than quarterly deployment periods are desired.

Comparison of Four Active and Passive Sampling Techniques for Pesticides in Air

Four sampling systems were evaluated for their ability to determine the concentrations of pesticides in the atmosphere of rural southern Ontario. Two active air samplers (AAS, high-volume and low-volume pumps) and two passive air samplers (PAS, polyurethane foam disks and XAD-resin) were deployed between March 2006 and September 2007 using different sampling frequencies (biweekly to annually) and durations (24 h to 1 yr). Concentrations of nine pesticides in air determined by the different systems were compared at time scales of two weeks, two months, and one year. Agreement in the average concentrations obtained by different techniques improved with increasing length of the comparison period, especially for pesticides with high short-term temporal concentration variability. Such variability was high for the most volatile and reactive pesticides (trifluralin and pendimethalin). Except for these two pesticides, the annually averaged air concentrations determined by the different systems are within a factor of 2.5 for all pesticides and are not statistically different. Even though the PUF-PAS may have approached equilibrium with the atmosphere during deployment, the air concentrations are not statistically significantly different from those determined by AAS when averaged over longer time scales. Two month XAD-PAS deployments during the second summer resulted in sufficient sampling volumes to reliably establish air concentrations. If the sole purpose of collecting air samples is the assessment of long-term air concentration trends, this can be achieved most cost-effectively, i.e., with the least number of samples with year-long XAD-PAS.

Modification and Calibration of a Passive Air Sampler for Monitoring Vapor and Particulate Phase Brominated Flame Retardants in Indoor Air: Application to Car Interiors

A passive air sampler was modified to monitor both vapor and particulate phase brominated flame retardants (BFRs) in indoor air using polyurethane foam disks and glass fiber filters (GFF). Significant correlation (p < 0.01) was observed between passive (ng day(-1)) and active sampler (ng m(-3)) derived BFR concentrations in an office microenvironment (r = 0.94 and 0.89 for vapor and particulate phase BFRs, respectively). A calibration experiment was performed where concentrations of target BFRs were obtained for an office using a low volume active sampler operated over a 50 day period alongside passive samplers. The passive uptake rates of each studied BFR ranged between (0.558-1.509 ng day(-1)) and (0.448-0.579 ng day(-1)) for vapor and particulate phases, respectively. The passive entrapment of particles by the GFF was investigated using environmental scanning electron microscopy which revealed gravitational deposition of particles as the main mechanism involved. The developed sampler was applied to monitor BFR concentrations in 21 cars. Average concentrations of SigmaHBCDs, TBBP-A, and Sigmatetra-deca BDEs were 400, 3, and 2200 pg m(-3) in cabins and 400, 1, and 1600 pg m(-3) in trunks. No significant differences (p < 0.05) were observed between levels of SigmaHBCDs and Sigmatrito hexa- BDEs in cabins and trunks. However, TBBP-A, BDE-209, and SigmaPBDEs concentrations were significantly higher in vehicle cabins.

Field intercomparison on the determination of volatile and semivolatile polyfluorinated compounds in air

Environmental context.Polyfluorinated compounds are an emerging group of organic pollutants that are globally distributed in urban and natural environments. Reliable air monitoring methods are crucial to our understanding of how these pollutants are released to, and transported in, the atmosphere. This intercomparison study, involving laboratories that investigate polyfluorinated compounds in air, uncovers inconsistencies in the reported data, and highlights necessary analytical improvements for future research projects. Abstract.Fluorotelomer alcohols, perfluorinated sulfonamides or sulfonamido ethanols are volatile precursors of persistent perfluorinated acids. Published air-sampling strategies and analytical methods to determine these compounds differ. To assess performance on the determination of airborne polyfluorinated compounds, an intercomparison comprising four international research groups was established. Instrumental and analytical comparability between laboratories varied depending on the compound class. Variability in different sampling strategies was assessed for active (high-volume) v. passive samplers consisting of either semipermeable membrane devices or sorbent-impregnated polyurethane foam disks. Results from passive samplers were typically within an order of magnitude of air concentrations from averaged continuous high-volume samples. Smallest deviations (passive v. active) were observed for sorbent-impregnated polyurethane foam disk samplers with best agreement for fluorotelomer alcohols. This study reveals that it is important to be aware of several types of uncertainty or error for the determination of airborne polyfluorinated compounds and report data in this context or to take steps to minimise their impact.

A comparative evaluation of passive and active samplers for measurements of gaseous semi-volatile organic compounds in the tropical atmosphere

The polyurethane foam (PUF) disk-based passive air samplers (PAS), mounted inside two aluminium bowls to buffer the air flow to the disk and to shield it from precipitation and sunlight, were used for the collection of atmospheric SVOCs in Singapore during April 2008–June 2008. Data obtained from PAS measurements are compared to those from active high-volume air sampling (AAS). Single factor ANOVA tests show that there were no significant differences in chemical distribution profiles between actively and passively collected samples (PAHs, F = 3.38 × 10 −8 < F critical = 4.17 with p > 0.05; OCPs, F = 2.71 × 10 −8 < F critical = 4.75 with p > 0.05). The average air-side mass transfer coefficient ( k A ) for PAS, determined from the loss of depuration compounds such as 13C 6 – HCB (1000 ng), 13C 12 – 4,4′ DDT (1000 ng) and 13C 12 – PCB 101 (1000 ng)spiked on the disks prior to deployment, was 0.12 ± 0.04 m s −1. These values are comparable to those reported previously in the literature. The average sampling rate was 3.78 ± 1.83 m 3 d −1 for the 365 cm 2 PUF disk. Throughout the entire sampling period (∼68 d), most of the PAHs and all OCPs exhibited a linear uptake trend on PAS, while naphthalene, acenaphthylene, acenaphthene and fluorene reached the curvilinear phase after the first ∼30 d exposure. Theoretically estimated times to equilibrium ( t eq ) ranged from around one month for Acy to hundreds of years for DB(ah)A. Sampling rates, based on the time integrated active sampling-derived concentrations and masses collected by PUF disks during the linear uptake phase, were determined for all target compounds with the average values of 2.50 m 3 d −1 and 3.43 m 3 d −1 for PAHs and OCPs, respectively. More variations were observed as compared to those from the depuration study. These variation were most likely due to the difference of physicochemical properties of individual species. Lastly, multiple linear regression models were developed to estimate the log-transformed gaseous concentration of an individual compound in air based on the mass collection rate of the gaseous SVOCs measured using the PAS and the molecular weight (MW) of the particular compound for both PAHs and OCPs, respectively.

Field Evaluation of Polyurethane Foam Passive Air Samplers to Assess Airborne PAHs in Occupational Environments

There is a need for simple air sampling techniques to enable routine monitoring of the occupational exposure to polycyclic aromatic hydrocarbons (PAHs) in compliance with occupational exposure limits. Other gas-phase contaminants can be monitored in workplaces using passive samplers but this is currently not the case for PAHs. Here, polyurethane foam (PUF) disk passive air samplers (PAS), routinely used for outdoor air monitoring of PAHs and POPs, were assessed for their suitability in an indoor occupational environment against: ability to accumulate detectable levels within 1-2 weeks; quantitative sampling of benzo(a)pyrene (BaP), precision, uptake kinetics, influence of shelter design, and performance of 16 deuterated PAHs as depuration compounds (DCs). Sampling rates (R-values) for PAHs in PUF-PAS, estimated by comparison to low-volume active samplers, and the loss of DCs, varied for individual PAHs (1-10 m(3) day(-1)) but were found to be in the same order of magnitude for both gas-phase and particle-associated PAHs including BaP. Only one PAH (Acy) fulfilled the DC criteria of >40% loss during the 2 week exposure. These results suggest that PUF-PAS are potentially useful tools for PAHs in occupational environments in screening workplaces and identifying sources/hotspots - although unlikely to replace active sampling.

안면도에서 대기 중 가스상 PAHs의 계절적 변동

Passive air samplers with polyurethane foam (PUF) disks were employed to determine seasonal gas phase variation of polycyclic aromatic hydrocarbons (PAHs) in ambient air on Anmyeon island from March 2007 to January 2008. Sum of 13 PAHs ranged between <TEX>$3.5\;ng/m^3$</TEX> and <TEX>$27.6\;ng/m^3$</TEX>. Total PAHs during the heating season was 6.2 times higher than non-heating season. The dominant PAHs components during sampling periods were low and middle molecular weight PAHs including phenanthrene, fluoranthene, pyrene and chrysene. Gas exchange fluxes of PAHs across the air-water interface of the Yellow Sea were calculated using a modified two-film exchange model. PAHs fluxes ranged from <TEX>$196\;ng/m^2/d$</TEX> net volatilization during summer to <TEX>$3830\;ng/m^2/d$</TEX> net absorption during winter. Passive air sampler provides a convenient and cost-effective tool for measuring averaged gas phase PAHs, which was successfully used for calculation of gas exchange flux of PAHs in the Yellow Sea.

Further studies on the uptake of persistent organic pollutants (POPs) by polyurethane foam disk passive air samplers

Passive air samplers (PAS) can be used to monitor semi-volatile organic compounds in the atmosphere. Polyurethane foam (PUF) disks are a popular sampling medium because they have a high retention capacity for such compounds. This paper reports a highly time-resolved uptake study, to derive uptake rate data under field conditions, and investigate the effects of using different foam densities on the uptake rate. PUF disks were deployed alongside an active sampler, for periods of up to 12 weeks. The uptake rates were measured for a range of gas- and particle-bound persistent organic pollutants (polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs)), of different properties, to explore whether gas–particle partitioning affected uptake rate. Uptake rates for two different densities of foam (0.021 and 0.035 g cm −3) were not statistically significantly different from each other. Uptake rates of light PCBs averaged ∼6.5 m 3 day −1, somewhat higher than in previous studies; higher wind speeds and lower temperatures in this study are the likely reason for this difference. The study showed: i) the uptake rate of the compound with lowest K OA considered in this study (PCB-28/31) declined in the later weeks, indicating an approach to equilibrium; ii) uptake rates of lighter BDEs and heavier PCBs (compounds of intermediate K OA in this study) remain similar throughout the study period, indicating that they are not approaching equilibrium during the 12-week-study; iii) uptake rates were typically: ∼8 m 3 day −1 for PCB-52; ∼9.5 m 3 day −1 for PCB-95; ∼11 m 3 day −1 for BDE-28 and ∼2 m 3 day −1 BDE-99. The latter compound has an important particle-bound component and this lowers the sampling rate compared to predicted uptake rates for compounds which are in the gas phase only. It is shown that knowledge of gas–particle partitioning is needed to correct for this effect, and to improve predicted uptake rates.

Use of Depuration Compounds in Passive Air Samplers: Results from Active Sampling-Supported Field Deployment, Potential Uses, and Recommendations

Depuration compounds (DCs) are added to passive air samplers (PAS) prior to deployment to account for the wind-dependency of the sampling rate for gas-phase compounds. This correction is particularly useful for providing comparable data for samplers that are deployed in different environments and subject to different meteorological conditions such as wind speeds. Two types of PAS--the polyurethane foam (PUF) disk sampler and semipermeable membrane devices (SPMDs)--were deployed at eight heights on a 100 m tower to test whether the DC approach could yield air concentrations profiles for PCBs and organochlorine pesticides and account for the wind speed gradient with height. Average wind speeds ranged from 0.3 to 4.5 m s(-1) over the 40 day deployment, increasing with height Two low volume active air samples (AAS), one collected at 25 m and one at 73 m over the 40 day deployment showed no significant concentration differences for target compounds. As expected, the target compounds taken up by PAS reflected the wind profile with height This wind-dependency of the PAS was also reflected in the results of the DCs. A correction based on the DC approach successfully accounted for the effect of wind on PAS sampling rates, yielding a profile consistent with the AAS. Interestingly, in terms of absolute air concentrations, there were differences between the AAS and PAS-derived values for some target compounds. These were attributed to different sampling characteristics of the two approaches that may have resulted in slightly different air masses being sampled. Based on the results of this study, guidelines are presented for the use of DCs and for the calibration of PAS using AAS.

Levels and Vertical Distributions of PCBs, PBDEs, and OCPs in the Atmospheric Boundary Layer: Observation from the Beijing 325-m Meteorological Tower

Polyurethane foam disk passive air sampling was carried out to investigate the levels, vertical distributions, and potential sources of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs) in the atmospheric boundary layer of an urban site in Asia. Sampling was performed at nine heights (15, 47, 80, 120, 160, 200, 240, 280, 320 m) of the 325-m meteorological tower in Beijing, China over three 2-month periods between December 2006 and August 2007. This is the first study to report vertical variations of PBDEs in the ABL and one of only a few studies to investigate vertical distributions of persistent organic pollutants. The levels of sigma19PCBs and sigma8PBDEs were relatively low, ranging from 22 to 65 and from 2.3 to 18 pg m(-3), respectively. Air concentrations of gamma-HCH were high, with values in the range of 39-103 pg m(-3) in winter, 100-180 pg m(-3) in spring, and 115-242 pg m(-3) in summer, respectively. alpha-HCH concentrations ranged from 20 to 86 pg m(-3), p,p'-DDT between 7.3 and 78 pg m(-3), and HCB between 15 and 160 pg m(-3). The seasonal variations of PCBs, PBDEs, and OCPs may reflect different sources for these chemicals, such as those related with regional use (gamma-HCH), volatilization/re-emission (PBDEs, PCBs, alpha-HCH), and pesticide impurities (HCB). Although the performance reference compounds (PRCs) were spiked before deployment, the sampling rates showed strong dependency on wind speeds, resulting in large variations in uptake rates in the ABL, ranging from approximately 7.0 m3 day(-1) at ground level to 11 m3 day(-1) at 320 m. Levels of PCBs, PBDEs, and OCPs decreased with increasing ABL height indicating the potential of Beijing as the local sources.

Field calibration of polyurethane foam disk passive air samplers for PBDEs

A field study was performed to derive uptake rates of airborne polybrominated diphenyl ethers (PBDEs) to polyurethane foam (PUF) disk passive air samplers (PAS) and to investigate the influence of deployment location and device design. Data are presented on the gas-particle partitioning of PBDEs, since atmospheric phase distribution was considered to be a variable which could affect sampler performance. Uptake rates for these compounds were similar to those derived previously for other classes of persistent organic pollutants (POPs) (approximately 2-6 m(3)/day), with rates higher for the higher brominated species. Whilst other compound classes (e.g. polychlorinated biphenyls) are predominantly present in the air in the gas phase, heavier PBDEs have an association with particulates in the atmosphere at ambient temperatures. In this study, the PUF disk PAS therefore sampled PBDEs present in the gas phase and on fine aerosols with a similar sampling efficiency to those which are predominantly gas phase compounds. Compounds which are exclusively on particles are sampled less efficiently. A comparison of the three most commonly used PUF deployment configurations, used by different research groups, indicated little difference in uptake rates. The ranges of derived air concentrations for BDE-47, -99, and -183 between three sampler designs were 7.5-9.8, 7.4-12.4, and 4.7-6.6 pg/m(3), respectively. This suggests the robustness of this sampler in comparisons between regional and global campaigns where these three designs are employed.

A study of aerosol entrapment and the influence of wind speed, chamber design and foam density on polyurethane foam passive air samplers used for persistent organic pollutants

Polyurethane foam disks are a cheap and versatile tool for sampling persistent organic pollutants (POPs) from the air in ambient, occupational and indoor settings. This study provides important background information on the ways in which the performance of these commonly used passive air samplers may be influenced by the key environmental variables of wind speed and aerosol entrapment. Studies were performed in the field, a wind tunnel and with microscopy techniques, to investigate deployment conditions and foam density influence on gas phase sampling rates (not obtained in this study) and aerosol trapping. The study showed: wind speed inside the sampler is greater on the upper side of the sampling disk than the lower side and tethered samplers have higher wind speeds across the upper and lower surfaces of the foam disk at a wind speed > or = 4 m/s; particles are trapped on the foam surface and within the body of the foam disk; fine (<1 um) particles can form clusters of larger size inside the foam matrix. Whilst primarily designed to sample gas phase POPs, entrapment of particles ensures some 'sampling' of particle bound POPs species, such as higher molecular weight PAHs and PCDD/Fs. Further work is required to investigate how quantitative such entrapment or 'sampling' is under different ambient conditions, and with different aerosol sizes and types.