Sorbent-impregnated Polyurethane Foam Disks Research Articles

Per- and polyfluoroalkyl substances and volatile methyl siloxanes in global air: Spatial and temporal trends

The study reports on the atmospheric concentrations of per- and polyfluoroalkyl substances (PFAS) and volatile methyl siloxanes (VMS) measured using sorbent-impregnated polyurethane foam disks (SIPs) passive air samplers. New results are reported for samples collected in 2017, which extends temporal trend information to the period 2009–2017, for 21 sites where SIPs have been deployed since 2009. Among neutral PFAS, fluorotelomer alcohols (FTOHs) had higher concentrations than perfluoroalkane sulfonamides (FOSAs) and perfluoroalkane sulfonamido ethanols (FOSEs) with levels of ND‒228, ND‒15.8, ND‒10.4 pg/m3, respectively. Among ionizable PFAS, the sum of perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) in air were 0.128–781 and 6.85–124 pg/m3, respectively. Longer-chain i.e. C9–C14 PFAS, which are relevant to the recent proposal by Canada for a listing of long-chain (C9–C21) PFCAs to the Stockholm Convention, were also detected in the environment at all site categories including Arctic sites. Cyclic and linear VMS ranged between 1.34‒452 and 0.01–12.1 ng/m3, respectively, showing dominance in urban areas. Despite the wide range of levels observed across different site categories, geometric means of the PFAS and VMS groups were fairly similar when grouped according to the five United Nations regions. Variable temporal trends in air (2009–2017) were observed for both PFAS and VMS. PFOS, which has been listed in the Stockholm Convention since 2009, is still showing increasing tendencies at several sites, indicating constant input from direct and/or indirect sources. These new data inform international chemicals management for PFAS and VMS.

Characterization of polyurethane foam (PUF) and sorbent impregnated PUF (SIP) disk passive air samplers for measuring organophosphate flame retardants

This study aimed to characterize the uptake of organophosphate esters (OPEs) by polyurethane foam (PUF) and sorbent-impregnated polyurethane foam (SIP) disk passive air samplers (PAS). Atmospheric OPE concentrations were monitored with high-volume active air samplers (HV-AAS) that were co-deployed with passive air samplers. Samples were analyzed for tris(2-chloroisopropyl) phosphate (TCIPP), tri(phenyl) phosphate (TPhP), tris(2-chloroethyl) phosphate (TCEP), and tris(2,3-dichloropropyl) phosphate (TDCIPP). The mean concentration of ∑OPEs in air was 2650 pg/m3 for the HV-AAS. Sampling rates and the passive sampler medium (PSM)-air partition coefficient (KPSM−Air) were calculated for individual OPEs. The average calculated sampling rates (R) for the four OPEs were 3.6 ± 1.2 and 4.2 ± 2.0 m3/day for the PUF and SIP disks, respectively, and within the range of the recommended default value of 4 ± 2 m3/day. Since most of the OPEs remained in the linear uptake phase during the study, COSMO-RS solvation theory and an oligomer-based model were used to estimate KPUF-Air for the OPEs. The estimated values of log KPUF-Air were 7.45 (TCIPP), 9.35 (TPhP), 8.44 (TCEP), and 9.67 (TDCIPP). Finally, four configurations of the PUF and SIP disks were tested by adjusting the distance of the gap opening between the upper and lower domes of the sampler housing: i.e. 2 cm, 1 cm, no gap and 1 cm overlap. The sampling rate did not differ significantly between these four configurations (p < 0.05).

Using air, soil and vegetation to assess the environmental behaviour of siloxanes.

This study aimed to contribute to the enhancement of the knowledge of levels, trends and behaviour of eight siloxanes (four linear and four cyclic) in the environment. Adding to the prioritised scrutiny of the incidence in the atmosphere through passive samplers (sorbent-impregnated polyurethane foam disks--SIPs), the sampling of pine needles and soil was also performed, thus closing the circle of atmospheric exposure in the areas of study. Two sampling campaigns (one in summer and one in winter) were done in a total of eight sampling points in the Portuguese territory, which covered a wide range of human presence and land uses (urban, industrial, remote and beach areas). By adopting a "green" approach in terms of analytical methods, namely reducing the clean-up steps for the passive air samples and using the quick, easy, cheap, effective, rugged and safe (QuEChERS) technology for soils and pine needles, the results showed total concentration of siloxanes between 5 and 70 ng g(-1) (dry weight) for soils and from 2 to 118 ng g(-1) (dry weight (dw)) for pine needles, with no clear seasonal trend. For SIPs, the levels varied from 0.6 to 7.8 ng m(-3) and were higher in summer than in winter in all sites. Overall, the cyclic siloxanes were found in much higher concentrations, with D5 and D6 being the most predominant in a great majority of cases. Also, the urban and industrial areas had the highest incidence, suggesting a strong anthropogenic fingerprint, in line with their main uses.

Characterization of Two Passive Air Samplers for Per- and Polyfluoroalkyl Substances

Two passive air sampler (PAS) media were characterized under field conditions for the measurement of per- and polyfluoroalkyl substances (PFASs) in the atmosphere. The PASs, consisting of polyurethane foam (PUF) and sorbent-impregnated PUF (SIP) disks, were deployed for over one year in parallel with high volume active air samplers (HV-AAS) and low volume active air samplers (LV-AAS). Samples were analyzed for perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkane sulfonic acids (PFSAs), fluorotelomer alcohols (FTOHs), fluorotelomer methacrylates (FTMACs), fluorotelomer acrylates (FTACs), perfluorooctane sulfonamides (FOSAs), and perfluorooctane sulfonamidoethanols (FOSEs). Sampling rates and the passive sampler medium (PSM)-air partition coefficient (KPSM-A) were calculated for individual PFASs. Sampling rates were similar for PFASs present in the gas phase and particle phase, and the linear sampling rate of 4 m(-3) d(-1) is recommended for calculating effective air sample volumes in the SIP-PAS and PUF-PAS for PFASs except for the FOSAs and FOSEs in the PUF-PAS. SIP disks showed very good performance for all tested PFASs while PUF disks were suitable only for the PFSAs and their precursors. Experiments evaluating the suitability of different isotopically labeled fluorinated depuration compounds (DCs) revealed that (13)C8-perfluorooctanoic acid (PFOA) was suitable for the calculation of site-specific sampling rates. Ambient temperature was the dominant factor influencing the seasonal trend of PFASs.

Sorbent impregnated polyurethane foam disk passive air samplers for investigating current-use pesticides at the global scale

A pilot study conducted at a subset of 20 sites operated under the GAPS (Global Atmospheric Passive Sampling) Network compared the performance of two types of passive samplers for measuring air concentrations of currently–used pesticides, during 3–month deployment periods. The conventional polyurethane foam (PUF) disk sampler was able to capture a range of targeted current–use pesticides CUPs (dacthal, trifluralin, chlorothalonil, chlorpyrifos, and pendimethalin) but experienced equilibrium for some compounds (dacthal, trifluralin, and chlorothalonil) during the deployment period. The second sampler type used was a modified PUF disk sampler impregnated with XAD powder [i.e. the SIP (sorbent–impregnated PUF) disk] to increase sorptive capacity. The SIP disk sampler accumulated greater amounts of most targeted CUPs when compared to the PUF disk sampler. Results of the study showed that chlorothalonil was the most abundant CUP reflecting its widespread use, globally; whereas dacthal exhibited greater global distribution, including presence at remote sites, reflecting its high potential for long–range atmospheric transport. A thorough calibration of both the PUF disk and the SIP disk samplers is required to further define uptake profiles and to determine their range of applicability for various CUPs.

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.

Sorbent-Impregnated Polyurethane Foam Disk for Passive Air Sampling of Volatile Fluorinated Chemicals

A passive air sampler comprising a polyurethane foam (PUF) disk impregnated with XAD-4 powder has been developed. This sorbent-impregnated PUF (SIP) disk builds on previous work using PUF disk passive air samplers that have been effective in spatial air mapping studies of nonpolar hydrophobic chemicals, without the need of electricity or expensive air sampling equipment. In this study, PUF disks and SIP disks are calibrated for sampling volatile polyfluorinated chemicals--specifically, the fluorotelomer alcohols (FTOHs) and perfluoroalkyl sulfonamides (PFASs). Results demonstrate the low sorptive capacity of the PUF disk samplers, particularly for the FTOHs, with PUF disks reaching equilibrium within 1 day, after collecting approximately 0.4 and 1.2 m3 of air for 8:2 FTOH and 10:2 FTOH, respectively. This limits their use for these target compounds when time-weighted, linear-phase sampling is desired. The presence of just 0.4 g of XAD powder in the SIP disks greatly increases the sorptive capacity (by approximately 2 orders of magnitude for the FTOHs) and provides linear-phase sampling for a period of several weeks. PUF-air partition coefficients, KPUF-A, calculated for the FTOHs and PFASs are considerably lower than values predicted using previously established correlations against the octanol-air partition coefficient, KOA, demonstrating the unique partitioning behavior of the polyfluorinated chemicals. Using results from these calibration tests, air concentrations of FTOHs were derived from PUF disk samples that were deployed in 52 homes in Ottawa, Canada, during 2002/2003. These represent the first comprehensive measurements of FTOHs in indoor air in North America. Range and (geometric mean) air concentrations (pg m-3) were 261-28 900 (2070) for 8:2 FTOH and 104-9210 (890) for 10:2 FTOH. These air concentrations are orders of magnitude higher than observed for outdoor air, establishing indoor environments as important for human exposure and also as potential sources to the larger environment.