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.     

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.     

Polycyclic aromatic hydrocarbons in ambient air in the Philippines derived from passive sampler with polyurethane foam disk

Passive samplers with polyurethane disks (PUF) were applied in the determination of the concentration of polycyclic aromatic hydrocarbons (PAHs) in ambient air in six residential areas in the Philippines during four simultaneous sampling periods. The uptake profiles of PAHs were determined at one site during one sampling period. Most of the PAHs that were detected in air at concentrations that were significantly higher than their analytical detection limits exhibited a linear uptake trend on the PUF disk. The linear uptake profiles of some high molecular weight (HMW) PAHs were not established and this is attributed to the low concentration of the compounds in air in the gaseous phase. The retention concentrations of phenanthrene-d-10 were determined after depuration in four sampling sites during two sampling periods. The sampling rate for phenanthrene-d-10 was calculated at the linear phase of the uptake using the k_A derived from depuration experiments and the relationship of k_A and sampling rate which was established in a previous passive sampling study. The average sampling rate obtained for phenanthrene d-10 (2.94±0.69 m³ d⁻¹) was applied for derivation of the concentrations of the PAHs in the field samples.The passive sampler with PUF disk and short integration time of 42–56 days is applicable for the derivation of the concentrations of PAHs in ambient air in the Philippines. The concentrations of the organic pollutants derived from the passive sampler showed variability for the six residential areas; reflecting the influence of possible sources of emission of the pollutants at the sites at the different sampling periods. The weather conditions, including the occurrence of a tropical cyclone, increased rainfall and high-relative humidity during the rainy season, had an influence on the concentrations of PAHs derived by the passive sampler.     

Air concentrations of PCDD/Fs, PCBs and PCNs using active and passive air samplers

The concentrations of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) were determined in air samples collected at four sampling sites located in two zones of Barcelona (Spain): near a municipal solid waste incinerator (MSWI) and a combined cycle power plant (3 sites), and at a background/control site. Samples were collected using high-volume active samplers. Moreover, 4 PUF passive samplers were deployed at the same sampling points during three months. For PCDD/Fs, total WHO-TEQ values were 27.3 and 10.9 fg WHO-TEQm(-3) at the urban/industrial and the background sites, respectively. The sum of 7 PCB congeners and the Sigma PCN levels were also higher at the industrial site than at the background site. In order to compare active and passive sampling, the accumulated amounts of PCDD/Fs, PCBs and PCNs in the four passive air samplers, as well as the total toxic equivalents in each sampling site were also determined. To assess the use of PUF passive samplers as a complementary tool for PCDD/F, PCB and PCN monitoring, sampling rates were calculated in accordance with the theory of passive air samplers. PUF disks allowed establishing differences among zones for the POP levels, showing that they can be a suitable method to determine POP concentrations in air in areas with various potential emission sources. Although both particle and gas phase were sorbed by the PUFs, data of gas phase congeners are more reproducible.     

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.     

New passive samplers for chlorinated semivolatile organic pollutants in ambient air

Two new types of passive samplers were designed and tested on semivolatile organic compounds. The first type (a spiral-rod sampler) consists of a low-density polyethylene membrane acting as a permeation film and a silicone elastomer as the receiving material; the second (a stir-bar sampler) has the same membrane material but a polydimethylsiloxane-coated stir bar acting as the collector phase and installed radially symmetrically in the sampler. The advantages of the new samplers are their simple design, low costs, and their easy processing via thermodesorption coupled with capillary gas chromatography and mass selective detection. In both samplers, the uptake of selected analytes was integrative over exposure periods of up to 384 h. The sampling rates calculated from a laboratory calibration study using the chlorinated semivolatiles hexachlorobenzene, hexachlorocyclohexane isomers and polychlorinated biphenyls ranged from 88.1 ml h-1 for delta-hexachlorocyclohexane to 3443 ml h-1 for 2,2',5,5'-tetrachlorobiphenyl. A field trial at a hazardous waste dump near Bitterfeld, Germany, for up to 21 days combined with periodical determinations of air concentrations using low-volume sampling indicated that the new samplers can in principle be used in the field, although the sampling rates derived from the field results differed considerably from the laboratory findings. Nevertheless the preliminary results suggest that the new sampler types are promising for the long-term air monitoring of semivolatiles.     

The performance of passive flow monitors and phosphate accumulating passive samplers when exposed to pulses in external water flow rate and/or external phosphate concentrations

Passive samplers are typically calibrated under constant flow and concentration conditions. This study assessed whether concentration and/or flow pulses could be integrated using a phosphate passive sampler (P-sampler). Assessment involved three 21-day experiments featuring a pulse in flow rate, a pulse of filterable reactive phosphate (FRP) concentration and a simultaneous concentration and flow pulse. FRP concentrations were also determined by parallel grab sampling and the P-sampler calibrated with passive flow monitors (PFMs) and direct measurement of flow rates. The mass lost from the PFM over the deployment periods predicted water velocity to within 5.1, 0.48 and 7.1% when exposed to a flow rate pulse (7.5-50 cm s⁻¹), concentration pulse (5-100 μg P L⁻¹), or both simultaneously. For the P-sampler, good agreement was observed between the grab and passive measurements of FRP concentration when exposed to a pulse in flow (6% overestimation) or concentration (2% underestimation).     

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.     

A passive flux denuder for evaluating emissions of ammonia at a dairy farm

Passive samplers have been shown to be an inexpensive alternative to direct sampling. Diffusion denuders have been developed to measure the concentration of species such as ammonia (NH3), which is in equilibrium with particulate ammonium nitrate. Conventional denuder sampling has required active sampling that inherently requires air pumps and, therefore, electrical power. To estimate emissions of NH3 from a fugitive source would require an array of active samplers and meteorological measurements to estimate the flux. A recently developed fabric denuder was configured in an open tube to passively sample NH3 flux. Passive and active samplers were collocated at a dairy farm at the California State University, Fresno, Agricultural Research Facility. During this comparison study, NH3 flux measurements were made at the dairy farm lagoon before and after the lagoon underwent acidification. Comparisons were made of the flux measurements obtained directly from the passive flux denuder and those calculated from an active filter pack sampler and wind velocity. The results show significant correlation between the two methods, although a correction factor needed to be applied to directly compare the two techniques. This passive sampling approach significantly reduces the cost and complexity of sampling and has the potential to economically develop a larger inventory base for ambient NH3 emissions.     

Determination of deployment specific chemical uptake rates for SDB-RPD Empore disk using a passive flow monitor (PFM)

The use of the adsorbent styrenedivinylbenzene-reverse phase sulfonated (SDB-RPD) Empore disk in a chemcatcher type passive sampler is routinely applied in Australia when monitoring herbicides in aquatic environments. One key challenge in the use of passive samplers is mitigating the potentially confounding effects of varying flow conditions on chemical uptake by the passive sampler. Performance reference compounds (PRCs) may be applied to correct sampling rates (R_s) for site specific changed in flow and temperature however evidence suggests the use of PRCs is unreliable when applied to adsorbent passive samplers. The use of the passive flow monitor (PFM) has been introduced for the assessment of site-specific changes in water flow. In the presented study we have demonstrated that the R_s at which both atrazine and prometryn are accumulated within the SDB-RPD-Empore disk is dependent on the flow conditions. Further, the calibration of the measured R_s for chemical uptake by the SDB-RPD-Empore disk to the mass lost from the PFM has shown that the PFM provides an accurate measure of R_s for flow velocities from 0 to 16 cm s⁻¹. Notably, for flow rates >16 cm s⁻¹, a non linear increase in the R_s of both herbicides was observed which indicates that the key resistance to uptake into the SDB-RPD Empore disk is associated with the diffusion through the overlying diffusion limiting membrane. Overall the greatest uncertainty remains at very low flow conditions, which are unlikely to often occur in surface waters. Validation of the PFM use has also been undertaken in a limited field study.     

Calibration and field performance of membrane-enclosed sorptive coating for integrative passive sampling of persistent organic pollutants in water

Membrane-enclosed sorptive coating (MESCO) is a miniaturised monitoring device that enables integrative passive sampling of persistent, hydrophobic organic pollutants in water. The system combines the passive sampling with solventless preconcentration of organic pollutants from water and subsequent desorption of analytes on-line into a chromatographic system. Exchange kinetics of chemicals between water and MESCO was studied at different flow rates of water, in order to characterize the effect of variable environmental conditions on the sampler performance, and to identify a method for in situ correction of the laboratory-derived calibration data. It was found that the desorption of chemicals from MESCO into water is isotropic to the absorption of the analytes onto the sampler under the same exposure conditions. This allows for the in situ calibration of the uptake of pollutants using elimination kinetics of performance reference compounds and more accurate estimates of target analyte concentrations. A field study was conducted to test the sampler performance alongside spot sampling. A good agreement of contaminant patterns and water concentrations was obtained by the two sampling techniques.     

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.     

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   

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.     

Field validation of an active sampling cartridge as a passive sampler for long-term carbonyl monitoring

A carbonyl sampler originally designed for the active sampling method (Sep-Pak XPoSure) was used for long-term passive sampling, and its applicability as a passive sampler was examined through field experiments. The uptake rates of passive sampling were determined experimentally from collocated passive and active samplings for various sampling periods. The obtained uptake rates of formaldehyde, acetaldehyde, and acetone were 1.48, 1.23, and 1.08 mL/min, respectively. These uptake rates were consistent for a wide range of the sampling term (12 hr-2 weeks). Uptake rates of each carbonyl were proportional to the diffusion coefficients of each. Therefore, the ratios of diffusion coefficients were used to calculate the uptake rates of carbonyls for which the rates were not determined experimentally. Lower limits of determination were 2.16-17.5 microg/m3 for 2-week sampling. It was confirmed that 2-week monitoring of carbonyl concentrations up to 118-229 microg/m3 was possible. Relative standard deviations of the passive method generated from the repeatability test were 2-12.3% error for five samplings, and the recovery efficiencies were larger than 90%. Thus, the passive sampler was found to be highly suitable for long-term monitoring of carbonyl compounds.     

Radial diffusive sampler for the determination of 8-h ambient ozone concentrations

The 8-h ozone radial diffusive sampler was evaluated according to the CEN protocol for the validation of diffusive samplers. All the parameters regarding the sampler characteristics were found to be consistent with the requirements of this protocol apart from the blank value, which must be evaluated and subtracted at each sampling. The nominal uptake rate was determined in laboratory conditions. However, the uptake rate depends on the mass uptake, temperature, humidity and on the combination of temperature and humidity. Based on laboratory experiments, an empirical model has been established which improved the agreement between the radial sampler and the reference method. This improvement was observed under several different meteorological and emission conditions of sampling. By using the model equation of uptake rate, the data quality objective of 30% for the expanded uncertainty included in the O(3) European Directive, is easily attained. Therefore, the sampler represents an appropriate indicative method.     

A Passive Flux Denuder for Evaluating Emissions of Ammonia at a Dairy Farm

Abstract

Passive samplers have been shown to be an inexpensive alternative to direct sampling. Diffusion denuders have been developed to measure the concentration of species such as ammonia (NH₃), which is in equilibrium with particulate ammonium nitrate. Conventional denuder sampling that inherently requires air pumps and, therefore, electrical power. To estimate emissions of NH₃ from a fugitive source would require an array of active samplers and meteorological measurements to estimate the flux. A recently developed fabric denuder was configured in an open tube to passively sample NH₃ flux. Passive and active samplers were collocated at a dairy farm at the California State University, Fresno, Agricultural Research Facility. During this comparison study, NH₃ flux measurements were made at the dairy farm lagoon before and after the lagoon underwent acidification. Comparisons were made of the flux measurements obtained directly from the passive flux denuder and those calculated from an active filter pack sampler and wind velocity. The results show significant correlation between the two methods, although a correction factor needed to be applied to directly compare the two techniques. This passive sampling approach significantly reduces the cost and complexity of sampling and has the potential to economically develop a larger inventory base for ambient NH₃ emissions.     

A directional passive air sampler for monitoring polycyclic aromatic hydrocarbons (PAHs) in air mass

A passive air sampler was developed for collecting polycyclic aromatic hydrocarbons (PAHs) in air mass from various directions. The airflow velocity within the sampler was assessed for its responses to ambient wind speed and direction. The sampler was examined for trapped particles, evaluated quantitatively for influence of airflow velocity and temperature on PAH uptake, examined for PAH uptake kinetics, calibrated against active sampling, and finally tested in the field. The airflow volume passing the sampler was linearly proportional to ambient wind speed and sensitive to wind direction. The uptake rate for an individual PAH was a function of airflow velocity, temperature and the octanol-air partitioning coefficient of the PAH. For all PAHs with more than two rings, the passive sampler operated in a linear uptake phase for three weeks. Different PAH concentrations were obtained in air masses from different directions in the field test.     

A comparative study of the performance of passive samplers

Atmospheric concentrations of benzene, toluene, ethylbenzene, and xylenes (o-xylene and m,p-xylene) were assessed in the Tricity area (Gdańsk-Sopot-Gdynia, Poland) with the use of two types of passive samplers: permeation (homemade passive samplers) and diffusive (Radiello and Orsa 5). Samples were collected during 2008 at selected sites in the Tricity area at monitoring stations belonging to the agency of Regional Air Quality Monitoring Foundation. The field study was conducted to compare the performance of these two different types of passive samplers. A statistical approach was formulated, and the experimental data were evaluated using the paired t test, Wilcoxon signed rank-sum test, and Friedman analysis of variance. All the statistical results confirm the hypothesis that the differences between the performances of the three sampling devices are highly significant. Despite the fact that data obtained with the homemade passive sampler indicated that the results were higher compared with those for the Radiello and Orsa 5 diffusive samplers, the authors note that all differences between the homemade permeation sampler and the Radiello and Orsa 5 diffusive samplers are positive.