Active Sampling Research Articles

Low-flow active and passive sampling of VOCs using thermal desorption tubes: theory and application at an offset printing facility.

While air sampling techniques using adsorbent-based collection, thermal desorption and chromatographic analysis have found a niche in ambient air sampling, occupational applications have been more limited. This paper evaluates the use of thermal desorption techniques for low flow active and passive sampling configurations which allow conveniently long duration sampling in occupational settings and other high concentration environments. The use of an orifice enables flows as low as 0.5 ml min(-1) and sampling periods up to several days without significant biases. A model is used to predict sampling rates of a passive sampler encompassing an orifice, a void space, glass wool, and the adsorbent. Laboratory and field tests conducted at a commercial offset printing facility, which contained a variety of volatile organic compounds (primarily aromatic but also a few chlorinated and terpene compounds at levels from 1 to 67,000 microg m(-3)), are used to evaluate the approach. Tenax GR and Carbosieve SIII, both singly and together, were employed as adsorbents. Side-by-side tests comparing high flow, low flow and passive samplers show excellent agreement and high linearity (r = 0.95) for concentrations spanning nearly five orders of magnitude. Active samplers were tested at flows as low as 0.5 ml min(-1), compared to typical flows up to 40 ml min(-1). Passive samplers demonstrated a linear range and agreement with predictions for adsorbate loadings from approximately 1 ng to nearly 10 microg. Using a chemical mass balance receptor model, concentrations in the facility were apportioned to solvents, inks and other indoor and outdoor sources. Overall, the use of low flow active and passive sampling approaches employing thermal desorption techniques provides good performance and tremendous flexibility that facilitates use in many applications, including workplace settings.

Application of Lichens for Assessment of Atmospheric Pollution by Tritium

ABSTRACTIt is known that lichens are used for assessment of atmosphere pollution by heavy metals, radioniclides, sulfur and nitrogen oxides, etc. However there were published in scientific literature only limited data on usage of lichens as bio-indicators of tritium1,2. There are presented in the paper the results of lichen application study for assessment of atmospheric pollution by tritium. Both tritium in tissue free water (TFWT) and organically bound tritium (OBT) were measured in lichen. Lichen species Hypogimnia physodes was used as a basic bioindicator. Pieces of lichen were sampled within the distance of 30 km of emission source. Established sampling sites were rectangular in shape with linear dimensions 100*100 m. Lichen samples were sampled from various trees: birch tree, aspen tree, pine tree and linden tree at the level of 1.5 m above the ground. Thermal vacuum desorption technique was used to extract TFWT from lichen samples. Pyrolitic oxidation of dried lichen samples by vanadium oxide was used to extract tritium from OBT. Air monitoring stations equipped with active and passive samplers were used to sample HT and HTO from the atmosphere. Liquid scintillation counting was used to measure tritium content in water samples.It was determined that tritium content in lichen samples (both in TFWT and OBT) in vicinity of an emission source is higher than that of tritium content in lichen at distant sampling sites. Variation of tritium activity of TFWT was about 10 times, variation of tritium activity in OBT was about 70 times. It was supposed that tritium content in TFWT was in equilibrium with tritium content in atmosphere at the minute of sampling, while tritium content in OBT was determined by tritium content in atmosphere over longer period of time.

Determination of Atmospheric Perfluorocarbon Background Concentrations of fL/L Range at the Western Coastal Area of Korea

As part of perfluorocarbon (PFC) tracer release experiment conducted at the western coastal area of Korea in February 2001, the background concentration level of perfluorocarbons (PFCs) in the atmosphere was determined by gas chromatography with electron capture detector. Prior to the PFC tracer release experiment in the field, air samples were collected using active samplers and the background concentrations of PFCs were determined. The concentrations of perfluoromethylcyclohexane (<TEX>$C_7F_{14}$</TEX>, PMCH) in the western coastal area of Korea were in the range of 5.8-8.7 fL/L. The mean concentration of the PMCH in the region exhibited no significant spatial and temporal variations. This concentration level is somewhat higher and has larger standard deviation than those of studies previously conducted in USA and Europe on the background concentration levels of PFCs. Because the background concentration of PMCH in Korea is still very low and consistent temporally and spatially, the PMCH tracer can be used suitably for the studies of long-range atmospheric transport.

Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O3, PM25, and CO

ABSTRACT While researchers have linked acute (less than 12-hr) ambient O3, PM25, and CO concentrations to a variety of adverse health effects, few studies have characterized short-term exposures to these air pollutants, in part due to the lack of sensitive, accurate, and precise sampling technologies. In this paper, we present results from the laboratory and field evaluation of several new (or modified) samplers used in the “roll-around” system (RAS), which was developed to measure 1-hr O3, PM25, and CO exposures simultaneously. All the field evaluation data were collected during two sampling seasons: the summer of 1998 and the winter of 1999. To measure 1-hr O3 exposures, a new active O3 sampler was developed that uses two nitrite-coated filters to measure O3 concentrations. Laboratory chamber tests found that the active O3 sampler performed extremely well, with a collection efficiency of 0.96 that did not vary with temperature or relative humidity (RH). In field collocation comparisons with a reference UV photometric monitor, the active O3 sampler had an effective collection efficiency ranging between 0.92 and 0.96 and a precision for 1-hr measurements ranging between 4 and 6 parts per billion (ppb). The limits of detection (LOD) of this method were 9 ppb-hr for the chamber tests and ~16 ppb-hr for the field comparison tests. PM2.5 and CO concentrations were measured using modified continuous monitors—the DustTrak and the Langan, respectively. A size-selective inlet and a Nafion dryer were placed upstream of the DustTrak inlet to remove particles with aerodynamic diameters greater than 2.5 um and to dry particles prior to the measurements, respectively. During the field validation tests, the DustTrak consistently reported higher PM2.5 concentrations than those obtained by the collocated 12-hr PM2 5 PEM samples, by approximately a factor of 2. After the DustTrak response was corrected (correction factor of 2.07 in the summer and 2.02 in the winter), measurements obtained using these methods agreed well with R2 values of 0.87 in the summer and 0.81 in the winter. The results showed that the DustTrak can be used along with integrated measurements to measure the temporal and spatial variation in PM2 5 exposures. Finally, during the field validation tests, CO concentrations measured using the Langan were strongly correlated with those obtained using the reference method when the CO levels were above the LOD of the instrument [~1 part per million (ppm)].

Exposure assessment to mercury vapor in chloralkali industry.

The aim of the study was to develop a sampling method aimed at individual sampling of mercury vapor and subsequent individual exposure assessment of the worker. Hopcalite available from Inowrocławskie Zakłady Chemiczne (in Poland) was found useful for mercury vapor sampling in active and passive individual samplers. However the sampling rate determined for passive sampler in steady-state laboratory chamber cannot be used under fluctuating conditions of mercury vapor concentration and air movement typical for field measurement. In order to check comparativeness of passive and active sampling methods, samples were taken in the same time and individual samplers fixed to worker's clothes were used. Mercury vapor concentration was measured at two chloralkali industries in Poland and the results were presented. Excessive exposure in both industries was confirmed by finding elevated mercury concentration in urine samples from the workers.

Field evaluation of a passive sampler for the exposure assessment of 2-methoxyethanol.

This paper presents a field evaluation of 3 M 3500 passive badges for measuring 2-methoxyethanol (ME) in a humid working environment. A total of 93 pairs of side-by-side active/passive samples, 48 pairs of duplicate active samples, 52 pairs of duplicate passive samples, and three groups of six replicate active/passive samples were compared. Three groups of six replicate active charcoal/active charcoal tube with drying tube samples were also compared to evaluate the humidity effect. No statistical difference was found between the passive badges and active samplers. Linear regression showed the correlation to be high (r = 0.992, slope = 0.973, n = 93) over the range of 0.17-163 ppm. The mean concentration difference was -0.34 ppm and the mean relative error was 3.50%. The intraclass correlation coefficients of 48 duplicate active samples and 52 duplicate passive samples were 0.994 and 0.989, respectively. The precision of replicate passive, active, and active/drying tube samples (n = 6) were 3.84%, 7.14%, and 5.12%, respectively. The humidity effect for active samples was insignificant at the low sampling rate (36.3 ml/min). It is therefore concluded that the use of the passive samplers to assess ME exposure produces comparable findings to that of active sampling.

Comparison Among Active and Passive Samplers for Monitoring Polycyclic Aromatic Hydrocarbons

In this paper we report the result of our research aimed to verify the applicability of the biological passive sampling for the analysis of polycyclic aromatic hydrocarbons in the atmosphere in substitution to the particulate matter sampling. The work concerned 11 sites selected in urban area of Catania, a town situated on the east coast of the Sicily, where the samples of particulate matter and pine needles have been collected. The PAH concentrations of the needles were referred to fresh and dry weight, to lipids content and superficial area. The PAH profiles were different for each matrix and we showed that the passive sampler can be a substitute of the particulate matter sampling for medium molecular weight PAH.

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 (<few hours) pollutant episodes or regulatory non-compliance, where appropriate. Equally important, cumulative exposures (e.g. with ozone, a non-accumulating pollutant in plants) cannot account for the stochasticity and the dynamics of air pollutant exposure and plant (particularly deciduous vegetation) response. Although still being tested, statistical methods appear to be available to reconstruct passive sampler data to mimic the dynamics of the co-located continuous monitoring data. Regional level air quality and ecological risk assessments (multi-point models) as a whole should consider this type of approach in the future, using co-located passive samplers, with continuous monitors at selected locations as calibration points for mapping the air quality distribution on temporal and spatial scales.

Initial field evaluation of the Harvard active ozone sampler for personal ozone monitoring.

Assessing personal exposure to ozone has only been feasible recently with the introduction of passive ozone samplers. These devices are easy to use, but changes in air velocity across their collection surfaces can affect performance. The Harvard active ozone sampler (AS) was developed in response to problems with the passive methods. This active sampler has been tested extensively as a microenvironmental sampler. To test for personal sampling, 40 children attending summer day-camp in Riverside, California wore the active ozone sampler for approximately 2.6 h on July 19 and 21, 1994, when ozone concentrations were about 100 ppb and 140 ppb, respectively. The children spent 94-100% of the sampling period outside, staying within a well-defined area while participating in normal camp activities. Ambient ozone concentrations across this area were monitored by two UV photometric ozone monitors. The active sampler was worn in a small backpack that was also equipped with a passive ozone sampler. Device precision, reported as the percent difference between duplicate pairs of samplers, was +/- 3.7% and +/- 4.2% for the active and passive samplers, respectively. The active sampler measured, on average, 94.5 +/- 8.2% of the ambient ozone while the passive samplers measured, on average, 124.5 +/- 18.8%. The samplers were worn successfully for the entire sampling period by all participating children.

Particle-bound benzene from diesel engine exhaust.

The large surface area of the carbon core of diesel exhaust particles may contribute to the adsorption or condensation of such volatile carcinogenic organic compounds as benzene. The attention of this study focused on determining the distribution of benzene between the gas and particulate phases in the breathing zone of bus garage workers. Benzene and suspended particulate matter were evaluated jointly in the air of a municipal bus garage. Personal passive monitors were used for benzene sampling in the breathing zone of the workers. Active samplers were used for sampling diesel exhaust particles and the benzene associated with them. The benzene levels were measured by gas chromatography. Diesel engine exhaust from buses was the main source of air pollution caused by benzene and particles in this study. The concentration of benzene in the gas and particulate phases showed a wide range of variation, depending on the distance of the workplace from the operating diesel engine. Benzene present in the breathing zone of the workers was distributed between the gas and particulate phases. The amounts of benzene associated with particles were significantly lower in summer than in winter. The particulate matter of diesel exhaust contains benzene in amounts comparable to the concentrations of carcinogenic polycyclic aromatic hydrocarbons (PAH) and the usually found nitro-PAH. The concentration of benzene in the gas phase and in the suspended particulate matter of air can serve as an additional indicator of exposure to diesel exhaust and its carcinogenicity.

Development and Evaluation of a Small Active Ozone Sampler

Current methods for monitoring ambient and microenvironmental ozone include continuous measurement instruments, such as UV photometric and chemiluminescence monitors, open-path diffusion optical absorption spectrometer, and passive sampling devices. This paper introduces a new small active ozone sampler that utilizes a single etched glass denuder as the collection substrate. The denuder is coated with a solution containing the nitrite ion that reacts with ozone to produce nitrate. It is attached to a small personal pump driven by a 9-V battery. When compared with UV photometric measurements, the active sampler demonstrated very good accuracy (active sampler/UV photometer = 0.94−1.00) and precision (%P = ±4.1−6.5%) under laboratory and ambient conditions for sampling period from 1 to 60 h. The Harvard active ozone sampler performed as well as the Timed Exposure Diffusion sampler, the only other active ozone sampler currently in use. Sampler performance was found to be insensitive to variations in relative humidity (active sampler/UV photometer ≈ 1.00 at 20−80% RH) except at very low relative humidity (active/UV photometer = 0.81 at 12%). A low limit of detection of 10 ppb·h allows for sampling at very low concentrations.

Drift of aerially applied diflubenzuron over an oak forest

A field study was conducted in a Central Pennsylvania forest to quantify the offsite drift of aerially applied Diflubenzuron. Spray was released along a flight line which was normal to the cross wind and also to a 750 m long line of sampling targets located just above the forest canopy. Short-range deposition (less than 133 m) was sampled with passive targets (Teflon® spheres), and active samplers (rotorods) were used at long-range distances (133–755m). Ten spray trials (replications) were conducted over 3 days in late summer. Profiles of wind, turbulence, temperature, and humidity were measured with instrumentation on a micrometeorology tower at levels up to 20m above the 20m tall canopy. Measured deposit patterns showed that significant amounts of the Diflubenzuron (approximately 30%) drifted further than 100m from the flight line without being delivered to the canopy top. Small amounts of drifting material were transported 750m downwind on all but one occasion. Downwind from the target area the amount of material present at the canopy top increased with increasing friction velocity, u ∗ .

Field trials of active and multi-port sock samplers in gravel-packed wells

Four novel sampling systems were tested for their ability to obtain level-representative groundwater samples from two gravel-packed boreholes in different hydrogeological settings at Skrydstrup (Denmark) and Torgau (Germany). Samples obtained with the novel devices were compared with those obtained from nearby permanent dedicated reference systems. Results obtained using the novel samplers vary from excellent agreement to no agreement. Numerical analysis was carried out in an attempt to understand the variation in the sampling results. Investigation showed that a single perfect sampler does not exist for these sites. Level-determined groundwater samples in gravel-packed wells can be obtained using active as well as multi-port sock samplers. The choice of the sampler depends mainly on the specific hydrogeological conditions, well completion, the type of pollution and the time available for sampling.

?Badge-type? passive sampler for monitoring ambient ammonia concentrations

A passive “badge-type” sampling device for the determination of gaseous ammonia was developed. The collection substrate is phosphoric acid. The sampler can be used for outdoor and indoor sampling of ammonia in the concentration range from 0.05 μg/m3 to 10 mg/m3. The performance was tested in the laboratory and in the field against an annualar denuder, a filter pack and an impinger technique. The intercalibration showed that the passive sampler compares very well with active samplers (r2=0.99; k=1.05). The average reproducibility of the sampler was 8%. Hence the badge sampler is well suited for the determination of ammonia in a wide range of concentrations and particularly for application under rural background conditions. The sampling rate of the device was calculated according to a simple multi-layer model.

Report of Workshop #3 on Active and Passive Sorbent Samplers

Report of Workshop #3 on Active and Passive Sorbent Samplers

An advanced air sampling technique for hazardous waste sites

Development and performance of a passive soil-air flux sampler as an alternative to conventional sampling systems is discussed. The passive sampler is designed to provide longterm measurements of flux rates of volatile organics at waste sites without disturbing the subsurface plume. Laboratory and field experiments conducted with the passive sampler and an active sampler (emission-isolation flux chamber) indicate that the passive sampler provides results very close to those of the active sampler and that the passive sampler is sensitive to smaller emissions. The passive sampler has added advantages over the emission-isolation flux chamber, such as easy deployment, minimum maintenance, and no power requirements.

Examination of sampling methods for assessment of personal exposures to airborne aldehydes

A personal exposure monitor was required for the determination of airborne aldehyde exposures caused by emissions from methanol-fuelled vehicles. Derivatization of aldehydes during collection was selected as the technique to enhance the integrity of samples and to facilitate analysis. Three derivatization agents, HMP [2-(hydroxymethyl)piperidine], BEA (N-benzylethanolamine) and DNPH (2,4-dinitrophenylhydrazine), were examined. High blank levels and poor chromatographic resolution of some of the derivatives discouraged the use of BEA and HMP, whereas DNPH derivatization allowed good sensitivity and resolution of the hydrazones of formaldehyde, acetaldehyde, acrolein, crotonaldehyde and benzaldehyde. Passive and active samplers containing DNPH-impregnated XAD (ORBO-43) and glass-fibre filters were evaluated for the determination of airborne aldehydes at several concentrations in the range 10–5000 µg m–3. Although analytical detection limits were better than 40 µg m–3, sampler blank values limited practical detection limits to 50–100 µg m–3 for the individual aldehydes. The analytical precision relative standard deviation approximately 20%, based on results for samplers deployed in triplicate in a test atmosphere. The effects of humidity, air velocity and concentration of aldehydes on the sampling characteristics of active and passive samplers were measured. Some discrepancies, particularly for the unsaturated aldehydes, were noted for results obtained with the different sampling procedures in controlled-atmosphere chamber tests. These results suggested that, after further development, a DNPH-based passive sampling method could meet the required performance criteria.

Exposure to Mercury in Industry and Dentistry: A Field Comparison between Diffusive and Active Samplers

Abstract A field comparison between active and diffusive Hydrar samplers for measurements of mercury in air was performed in a chloralkali plant, in a thermometer factory, and in six dentistry surgeries. Personal and stationary air samples were taken, as well as blood and urine for biological monitoring. In the chloralkali plant, in the thermometer factory, and in dentistry, the diffusive samplers showed considerably lower values than the active samplers. In the range 1-123 μg/m3 of mercury in air, the passive samplers showed 64 percent (95 percent confidence interval 60-68) of the results of the active samplers. One possible explanation is that the proposed sampling rate given by the manufacturer was incorrect to use here, owing to the low air velocities. However, no model for correction of the sampling rate is available. Mercury levels in air were low in dentistry (median 2.8 μg/m3) and moderate in the thermometer factory (median 38 μg/m3). The exposure for maintenance workers in the chloralkali industr...

Determination of ppb levels of formaldehyde in air

In order to be able to determine 100–500 ppb levels of formaldehyde in workroom air and 10–50 ppb levels in homes, methods for sampling and determination of formaldehyde in air have been investigated. With active samplers based on reaction with 2,4-dinitrophenylhydrazine on C18 cartridges, 8 h sampling time resulted in a detection limit of 1 ppb. With a passive sampling method and equal sampling time, the detection limit was determined to 22 ppb.

Environmental Monitoring of Tritium in Air with Passive Diffusion Samplers

AbstractA field trial in which outdoor air was sampled with an active reference sampler and several passive HTO-in-air samplers simultaneously was carried out at Chalk River Laboratories. Both passive and active samplers were changed on an approximately monthly schedule from 1990 September 2 to 1991 April 18. Average temperatures for the sampling intervals ranged from −8.6°C to +15.5°C and HTO-in-air concentrations measured by the active sampler were typically 10 Bq/m3. A total of 129 passive HTO-in-air sampler measurements were made during the seven sampling intervals. The passive samplers used for the field trial were of the type described by Stephenson,1 prepared with either tritium-free water or a solution of 50% tritium-free water and 50% ethylene glycol. As expected, the samplers prepared with the water-glycol solution performed more consistently than the samplers prepared with water only. Good agreement between passive and active sampler measurements was observed throughout the field trial. Passive...