Calibration of polyurethane foam (PUF) disk passive air samplers for quantitative measurement of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs): factors influencing sampling rates

PUF disk passive air samplers are increasingly employed for monitoring of POPs in ambient air. In order to utilize them as quantitative sampling devices, a calibration experiment was conducted. Time integrated indoor air concentrations of PCBs and PBDEs were obtained from a low volume air sampler operated over a 50 d period alongside the PUF disk samplers in the same office microenvironment. Passive sampling rates for the fully-sheltered sampler design employed in our research were determined for the 51 PCB and 7 PBDE congeners detected in all calibration samples. These values varied from 0.57 to 1.55 m3 d(-1) for individual PCBs and from 1.1 to 1.9 m3 d(-1) for PBDEs. These values are appreciably lower than those reported elsewhere for different PUF disk sampler designs (e.g. partially sheltered) employed under different conditions (e.g. in outdoor air), and derived using different calibration experiment configurations. This suggests that sampling rates derived for a specific sampler configuration deployed under specific environmental conditions, should not be extrapolated to different sampler configurations. Furthermore, our observation of variable congener-specific sampling rates (consistent with other studies), implies that more research is required in order to understand fully the factors that influence sampling rates. Analysis of wipe samples taken from the inside of the sampler housing, revealed evidence that the housing surface scavenges particle bound PBDEs.     

Polyurethane foam (PUF) disks passive air samplers: wind effect on sampling rates

Different passive sampler housings were evaluated for their wind dampening ability and how this might translate to variability in sampler uptake rates. Polyurethane foam (PUF) disk samplers were used as the sampling medium and were exposed to a PCB-contaminated atmosphere in a wind tunnel. The effect of outside wind speed on PUF disk sampling rates was evaluated by exposing polyurethane foam (PUF) disks to a PCB-contaminated air stream in a wind tunnel over air velocities in the range 0 to 1.75 m s-1. PUF disk sampling rates increased gradually over the range 0-0.9 m s-1 at approximately 4.5-14.6 m3 d-1 and then increased sharply to approximately 42 m3 d-1 at approximately 1.75 m s-1 (sum of PCBs). The results indicate that for most field deployments the conventional 'flying saucer' housing adequately dampens the wind effect and will yield approximately time-weighted air concentrations.     

A second look at the Palmes' diffusive sampler

The Palmes' tube, the first diffusive sampler incorporating a fixed path length, has received wide usage for the sampling of a large number of gaseous pollutants. But despite numerous previous studies, questions remain regarding the accuracy of these inexpensive, simple-to-construct, open-ended samplers. Here the mass transfer resistance in a Palmes' diffusive sampler was measured using the loss of cyclohexane from a Palmes' tube containing liquid cyclohexane at its base. The average loss rates, at factorial combinations of five air incidence angles evenly spaced from 270 degrees to 90 degrees, and five air speeds from 0.5 m/sec to 2.5 m/sec ranged from 46% to 121% higher than rates calculated from the physical dimensions of the sampler, proving the need to calibrate these samplers rather than relying on a theoretical calculation. The mass transfer resistance was nearly constant when the airflow was perpendicular to the sampler and sufficiently high to avoid stagnation, a finding that may explain the widespread acceptance of the results obtained using this sampler.     

Evaluation of the use of diffusive air samplers for determining temporal and spatial variation of volatile organic compounds in the ambient air of urban communities

The Houston-Galveston metropolitan area has a relatively high density of point and mobile sources of air toxics, and determining and understanding the relationship between emissions and ambient air concentrations of air toxics is important for evaluating potential impacts on public health and formulating effective regulatory policies to control this impact, both in this region and elsewhere. However, conventional ambient air monitoring approaches are limited with regard to expense, siting limitations, and representative sampling necessary for adequate exposure assessment. The overall goal of this multiphase study is to evaluate the use of simple passive air samplers to determine temporal and spatial variability of the ambient air concentrations of selected volatile organic compounds (VOCs) in urban areas. Phase 1 of this study, reported here, was a field evaluation of 3M organic vapor monitors (OVMs) involving limited comparisons with commonly used active sampling methods, an assessment of sampler precision, a determination of optimal sampling duration, and an investigation of the utility of a simple modification of the commercial sampler. The results indicated that a sampling duration of 72 hr exhibited generally low bias relative to automated continuous gas chromatography measurements, good overall precision, and an acceptable number of measurements above detection limits. The modified sampler showed good correlation with the commercial sampler, with higher sampling rates, although lower than expected.     

A holistic passive integrative sampling approach for assessing the presence and potential impacts of waterborne environmental contaminants

As an integral part of our continuing research in environmental quality assessment approaches, we have developed a variety of passive integrative sampling devices widely applicable for use in defining the presence and potential impacts of a broad array of contaminants. The semipermeable membrane device has gained widespread use for sampling hydrophobic chemicals from water and air, the polar organic chemical integrative sampler is applicable for sequestering waterborne hydrophilic organic chemicals, the stabilized liquid membrane device is used to integratively sample waterborne ionic metals, and the passive integrative mercury sampler is applicable for sampling vapor phase or dissolved neutral mercury species. This suite of integrative samplers forms the basis for a new passive sampling approach for assessing the presence and potential toxicological significance of a broad spectrum of environmental contaminants. In a proof-of-concept study, three of our four passive integrative samplers were used to assess the presence of a wide variety of contaminants in the waters of a constructed wetland, and to determine the effectiveness of the constructed wetland in removing contaminants. The wetland is used for final polishing of secondary-treatment municipal wastewater and the effluent is used as a source of water for a state wildlife area. Numerous contaminants, including organochlorine pesticides, polycyclic aromatic hydrocarbons, organophosphate pesticides, and pharmaceutical chemicals (e.g., ibuprofen, oxindole, etc.) were detected in the wastewater. Herein we summarize the results of the analysis of the field-deployed samplers and demonstrate the utility of this holistic approach.     

Passive sampling of ambient, gaseous air pollutants: an assessment from an ecological perspective

During some past two decades there has been a growing interest among air pollution-vegetation effects-scientists to use passive sampling systems for quantifying ambient, gaseous air pollutant concentrations, particularly in remote and wilderness areas. On the positive side, excluding the laboratory analysis costs, passive samplers are inexpensive, easy to use and do not require electricity to operate. Therefore, they are very attractive for use in regional-scale air quality assessments. Passive samplers allow the quantification of cumulative air pollutant exposures, as total or average pollutant concentrations over a sampling duration. Such systems function either by chemical absorption or by physical adsorption of the gaseous pollutant of interest onto the sampling medium. Selection of a passive sampler must be based on its known or tested characteristics of specificity and linearity of response to the chemical constituent being collected. In addition, the effects of wind velocity, radiation, temperature and relative humidity must be addressed in the context of absorbent/adsorbent performance and sampling rate. Because of all these considerations, passive samplers may provide under- or overestimations of the cumulative exposures, compared to the corresponding data from co-located continuous monitors or active samplers, although such statistical variance can be minimized by taking necessary precautions. On the negative side, cumulative exposures cannot identify short-term (相似文献   

Evaluation of the Use of Diffusive Air Samplers for Determining Temporal and Spatial Variation of Volatile Organic Compounds in the Ambient Air of Urban Communities

Abstract

The Houston-Galveston metropolitan area has a relatively high density of point and mobile sources of air toxics, and determining and understanding the relationship between emissions and ambient air concentrations of air toxics is important for evaluating potential impacts on public health and formulating effective regulatory policies to control this impact, both in this region and elsewhere. However, conventional ambient air monitoring approaches are limited with regard to expense, siting limitations, and representative sampling necessary for adequate exposure assessment. The overall goal of this multiphase study is to evaluate the use of simple passive air samplers to determine temporal and spatial variability of the ambient air concentrations of selected volatile organic compounds (VOCs) in urban areas. Phase 1 of this study, reported here, was a field evaluation of 3M organic vapor monitors (OVMs) involving limited comparisons with commonly used active sampling methods, an assessment of sampler precision, a determination of optimal sampling duration, and an investigation of the utility of a simple modification of the commercial sampler. The results indicated that a sampling duration of 72 hr exhibited generally low bias relative to automated continuous gas chromatography measurements, good overall precision, and an acceptable number of measurements above detection limits. The modified sampler showed good correlation with the commercial sampler, with higher sampling rates, although lower than expected.     

Calibration and field application of a solvent-based cellulose membrane passive sampling device for the monitoring of polar herbicides

A passive sampler device selective for hydrophilic analytes was constructed from cellulose membrane (40microm thickness) pre-stained with ruthenium red for 96-168h to impede degradation of the cellulose. The sampling device consisted of pre-stained cellulose membrane tubing containing a binary mixture of the solvents 1-dodecanol and 2,2,4-trimethylpentane as the sequestering medium. A laboratory flow-through system was used to investigate the rates of uptake of herbicides into the solvent mixture of the device and their release. The target herbicides were diuron, atrazine, metolachlor and molinate. Uptake of the herbicides into the solvent mixture of the cellulose membrane device was linear for up to 22 days, and daily sampling rates were determined. Release half-lives from the solvent mixture of the sampling device varied from 14 days for diuron, 15 days for atrazine, 84 days for metolachlor and 28 days for molinate. A field study was undertaken to determine if herbicide concentrations in agricultural drainage water derived from the passive sampler devices deployed for periods from 7 to 22 days, using the laboratory-derived sampling rates, would compare closely with time-weighted average herbicide concentrations determined from extractions of daily composite water samples. The concentrations of diuron, atrazine, metolachlor and molinate determined using the cellulose membrane devices were within twofold of the cumulated mean of the daily drainage water extractions.     

Validation of a flow-through sampler for pesticides and polybrominated diphenyl ethers in air

At locations without access to the electrical grid, a flow-through sampler (FTS) collects large volumes of air for the analysis of semi-volatile organic compounds (SVOCs). To test its performance under field conditions, an FTS and a traditional pumped high volume air sampler, both using polyurethane foam (PUF) as sampling medium, were co-deployed at the campus of the University of Toronto Scarborough from August 2006 to June 2007. Polybrominated diphenyl ethers (PBDEs) and various pesticides were quantified in the samples taken by both samplers to test the FTS's applicability to relatively non-volatile and slightly polar SVOCs. Air concentrations in samples taken with the FTS over five 2-week periods compare favourably with the average of the concentrations in several 24-h active high volume samples taken during the same period. In particular, time trends, temperature dependence relationships, and isomer ratios show a reasonable agreement between the two sampling techniques. An empirical linear solvation energy relationship for predicting the apparent theoretical plate number of the PUF assembly used in the FTS illustrates the effect of chemical properties, as well as temperature and wind speed, on sampling efficiency. In the absence of electrical power, the FTS can collect SVOCs from large air volumes as reliably and quantitatively as traditional HiVol samplers, although without separating gas and particle phase.     

Computational fluid dynamic modeling of two passive samplers

To effectively use a passive sampler for monitoring trace contaminants in the gas-phase, its sampling characteristics as a function of ambient wind conditions must be known. In this study two commonly used passive samplers were evaluated using computational fluid dynamics. Contaminant uptake by the polyurethane foam (PUF) was modeled using a species transport model. The external-internal flow interactions in the sampler were characterized, and the uptake rates of contaminant species were quantified. The simulations show that flow fields in the samplers have strong velocity gradients, and single-point velocity measurements do not capture flow interactions accurately. Sampling rates calculated for a PUF in freestream are in good agreement with sampling rates for PUFs in the passive samplers studied for the same average velocity over the PUF. The calculated sampling rates are in general agreement with those obtained experimentally by other researchers.     

The measurement of fine particulate semivolatile material in urban aerosols

Ammonium nitrate and semivolatile organic material (SVOM) are significant components of fine particles in urban atmospheres. These components, however, are not properly determined with methods such as the fine particulate matter (PM2.5) Federal Reference Method (FRM) or other single filter samplers because of significant losses of semivolatile material (SVM) from particles collected on the filter during sampling. The R&P tapered element oscillating microbalance (TEOM) monitor also does not measure SVM, because this method heats the sample to remove particle bound water, which also results in evaporation of SVM. Recent advances in monitoring techniques have resulted in samplers for both integrated and continuous measurement of total PM2.5, including the particle concentrator-Brigham Young University organic sampling system (PC-BOSS), the real-time total ambient mass sampler (RAMS), and the R&P filter dynamics measurement system (FDMS) TEOM monitor. Results obtained using these samplers have been compared with those obtained with either a PM2.5 FRM sampler or a TEOM monitor in studies conducted during the past five years. These studies have shown the following: (1) the PC-BOSS, RAMS, and FDMS TEOM are all comparable. Each instrument measures both the nonvolatile material and the SVM. (2) The SVM is not retained on the heated filter of a regular TEOM monitor and is not measured by this sampling technique. (3) Much of the SVM is also lost during sampling from single filter samplers such as the PM2.5 FRM sampler. (4) The amount of SVM lost from single filter samplers can vary from less than one-third of that lost from heated TEOM filters during cold winter conditions to essentially all during warm summer conditions. (5) SVOM can only be reliably collected using an appropriate denuder sampler. (6) A PM2.5 speciation sampler can be easily modified to a denuder sampler with filters that can be analyzed for semivolatile organic carbon (OC), nonvolatile OC, and elemental carbon using existing OC/elemental carbon analytical techniques. The research upon which these statements are based for various urban studies are summarized in this paper.     

Field evaluation of two diffusive samplers and two adsorbent media to determine 1,3-butadiene and benzene levels in air

Two types of diffusive samplers, both of which are compatible with thermal desorption, but differ in their geometry—SKC-Ultra (badge-type) and Radiello (radial symmetry-type)—were evaluated indoors and outdoors under varying temperature, humidity and wind speed conditions, using the graphitized adsorbents Carbopack X or Carbograph 5 to measure 1,3-butadiene and benzene in ambient air. The results obtained by diffusive sampling were compared with results obtained using a conventional active sampling method over both long (1 week) and shorter periods (6–24 h). Analysis and detection were performed using an automatic thermal desorber (ATD) connected to a gas chromatograph-flame ionization detector (GC/FID). Results from each sampler and adsorbent combination were examined using ordinary or multiple linear regression analysis. The overall uncertainty (OU) was also determined. In general, the results obtained with both samplers showed good agreement with those obtained by active sampling. Carbopack X appeared to be a more efficient adsorbent than Carbograph 5 for 1,3-butadiene, but the two adsorbents were equivalent for benzene. No effects of either humidity or air velocity were observed. Minor temperature effects were observed for both samplers for 1,3-butadiene. In summary, the results confirmed the accuracy of sampling rates previously determined for the two samplers and adsorbents. We consider the two samplers to be suitable for stationary and personal monitoring for the general population of 1,3-butadiene and benzene in various environments, indoors and outdoors. They are almost independent of meteorological conditions and may be suitable for monitoring industrial atmospheres.     

Practical considerations for addressing uncertainties in monitoring bulk deposition

The assessment of the deposition of both wet (rain and cloud) and dry sedimenting particles is a prerequisite for estimating element fluxes in ecosystem research. Many nations and institutions operate deposition networks using different types of sampler. However, these samplers have rarely been characterized with respect to their sink properties. Major errors in assessing bulk deposition can result from poor sampling properties and defective sampling strategies. Relevant properties are: sampler geometry and material, in particular the shape of the rim; sink properties for gases and aerosols; and microbial transformations of the collected samples. An adequate number of replicates allows the identification of samples which are contaminated, in particular by bird droppings. The paper discusses physical and chemical properties of the samplers themselves. The dependence of measurement accuracy on the number of replicates and the sampling area exposed is discussed. Recommendations are given for sampling strategies, and for making corrections and substitution of missing data.     

Performance evaluation of a tailor-made passive sampler for monitoring of tropospheric ozone

Introduction

This study presents the performance evaluation of a tailor-made passive sampler developed for the monitoring of tropospheric ozone.

Methods

The performance of the passive sampler was tested in the field conditions in terms of accuracy, precision, blank values, detection limit, effects of some parameters such as sampling site characteristics and sampling period on the field blanks, self-consistency, experimental and theoretical uptake rates, shelf life and comparison with commercial passive samplers.

Results

There was an agreement (R ²?=?0.84) between the responses of passive sampler and the continuous automatic analyser. The accuracy of the sampler, expressed as percent relative error, was obtained lower than 15%. Method precision in terms of coefficient of variance for three simultaneously applied passive samplers was 12%. Sampler detection limit was 2.42???g?m^?3 for an exposure period of 1?week, and the sampler can be stored safely for a period of up to 8?weeks before exposure. Satisfactory self-consistency results showed that extended periods gave the same integrated response as a series of short-term samplers run side by side. The uptake rate of ozone was found to be 10.21?mL?min^?1 in a very good agreement with the theoretical uptake rate (10.32?mL?min^?1). The results of the comparison study conducted against a commercially available diffusion tube (Gradko diffusion tube) showed a good linear relationship (R ²?=?0.93) between two passive samplers.

Conclusions

The sampler seems suitable to be used in large-scale measurements of ozone where no data are available or the number of existing automated monitors is not sufficient.     

Sampling and analysis of biological aerosols

The extreme particle size range and enormous heterogeneity of airborne biological particles make sampling a significant challenge. Three major sampler types available include gravity devices, impactors and suction samplers. Gravity methods, while most commonly used, are neither qualitatively or quantitatively accurate and of very limited use. Impaction samplers (rotating, centrifugal) accelerate air by rotating the collecting surface or with a fan. Particles are collected from measured volumes of air but these devices preferentially sample particles larger than 10 μm. Suction samplers, which efficiently collect particles of a wide size range from measured volumes of air, include slit samplers, cascade impactors, filtration devices and liquid impingers. Suction samplers can retrieve viable particles by direct impaction on culture media, or by subsequent culture of impinger fluid or filter eluates. Nonviable particles can often be identified by microscopic examination of slides, filters or filtrates of impinger fluids. Immunoassays and biochemical assays can be used with impinger fluid and filter eluates to assess antigen and toxin levels in measured air samples.     

Performance characteristics of PM10 samplers under calm air conditions

The size range of airborne particles that is closely related to specific deposition regions in the human respiratory tract and excess lung burden of these deposited particles is associated with disease. Size-selective sampling, therefore, needs to be performed to assess the related health risks. Performance criteria applied to these samplers must be well characterized in order to provide accurate and reliable results. The PM10 samplers that have been used in place of the total suspended particulate samplers for the collection of ambient air particles are more relevant to potential inhalation hazards. In order to be certified, a PM10 sampler must meet reliable performance specifications, primarily the aerosol penetration test with liquid and solid particles in a wind tunnel (wind speeds of 2, 8, and 24 km/hr). This testing is intended to assure reasonable accuracy in aerosol measurements. However, the sampler performance under calm air conditions has not been well studied. In the present study, the sampling heads of three devices--the Harvard impactor, the Personal Environmental Monitor (PEM), and the Sierra Andersen model 241 dichotomous sampler PM10 inlet head--were tested for aerosol separation efficiency. With the consideration of bias and imprecision of the measurements, five specimens of each type of sampler were chosen for performance testing, repeating the tests 5 times for each specimen. An ultrasonic atomizing nozzle was used to nebulize potassium sodium tartrate tetrahydrate and dioctyl phthalate particles as the solid and liquid challenge aerosols, respectively. The aerosol number concentrations and size distributions upstream and downstream of the samplers were measured by using an aerosizer calibrated against a settling velocity chamber. The results showed that among the samplers tested, the dichotomous sampler PM10 inlet head had the best fit to the PM10 convention, while the other two samplers not only appeared to have a steeper separation-curve slope but also had significant particle bounce when challenged with solid particles. Analysis of variance also confirmed the superiority of the dichotomous samplers. Surface-coating with oil or grease greatly reduced the problem of particle bounce.     

Uptake rates of alkylphenols, PAHs and carbazoles in semipermeable membrane devices (SPMDs) and polar organic chemical integrative samplers (POCIS)

Passive sampling devices provide a useful contribution to the monitoring of contaminants in the aquatic environment. However, calibration data needed for the calculation of water concentrations from sampler accumulations are restricted to a limited number of compound classes. Thus uptake of a range of alkylated phenols (AP), polycyclic aromatic hydrocarbons (PAH) and carbazoles was determined for semipermeable membrane devices (SPMDs) and polar organic chemical integrative samplers (POCIS) using a flow through exposure system. Sampling rates ranged from 0.02 to 0.26 l d(-1) for POCIS and 0.02 to 13.83 l d(-1) for SPMDs. Observed SPMD uptake was also compared to that predicted by an empirical model including the use of performance reference compounds (PRCs). Predicted sampling rates did not differ by more than a factor of 1.3 from experimental values for PAH, providing further evidence that the PRC approach can be successfully used to determine in situ sampling rates for these compounds. Experimental sampling rates for AP in SPMDs were, however, much lower than predicted. This discrepancy was too large to be explained by small uncertainties in the calibration system or in the calculations. Based on these data we conclude that while hydrophobic AP are accumulated by SPMDs their partitioning cannot be predicted from their logK(ow) using current methods. Due to this lower than expected uptake, sampling rates were only higher in SPMDs than POCIS in the range of logK(ow)>5.0. Simultaneous deployment of both sampler types allows the study of compounds with a broad range of physicochemical properties.     

The Collection and Analysis of Inorganic Dust Downwind of Source Effluents

Two directionally oriented high-volume samplers are used to pinpoint the collection of specific inorganic dusts from an industrial emission. One of the samplers is placed upwind of the source, and the other downwind. Both samplers are activated by winds blowing from the direction of the source to the downwind sampler. Both are de-activated when the wind shifts from the 30° sampling arc. Thus, the upwind sampler “sees” background dust, and the downwind sampler “sees” material originating from the source. Microsorban filters are used to collect the dust materials. The filter is then dissolved in benzene and the residue washed with benzene to remove the filter material and organic substances collected. The residue consists of dry, inorganic dust, which is then subjected to X-ray diffraction and optical microscopy, for analysis. This technique was successfully used to collect and analyze cement dust and mica dust from two separate industrial sources. The technique has promise for the analysis of a wide variety of inorganic materials which can be identified by X-ray diffraction, optical microscopy or other techniques.     

Comparative application of solid-phase microextraction fibre assemblies and semi-permeable membrane devices as passive air samplers for semi-volatile chlorinated organic compounds. A case study on the landfill "Grube Antonie" in Bitterfeld, Germany

Solid phase microextraction (SPME) fibres coated with Carbowax/divinylbenzene and semi-permeable membrane devices (SPMDs) of standard configuration were used to obtain time-weighted average (TWA) field air concentrations of selected chlorinated semi-volatile compounds on a landfill, where large amounts of lindane by-products were deposited, together with other hazardous chemical residues in the past. Additionally, spot sampling with SPME fibres was performed to identify the emission hotspot and sampling rates were determined/predicted for the substances of interest. Both samplers yield comparable TWA air concentrations of lindane and its isomers and of DDT with its metabolites and gain in certainty about the landfill as remaining source of air pollution with these compounds in the region. Both SPME fibres and SPMDs (respective their modifications) can be recommended as sampling tools in process studies and larger air monitoring programmes. However, further calibration studies and field tests are necessary to obtain reliable sampling rates for a wider range of semi-volatile compounds.