A comparison of X-ray fluorescence and wet chemical analysis for lead on air filters from different personal samplers used in a bronze foundry

Portable X-ray fluorescence (XRF) technology may provide faster turn-around without compromising accuracy when assessing personal exposures to metals such as lead, but it has only been tested in limited field environments. This study is part of a series, where different sampler types are used to collect airborne lead in different environments for presentation to a portable XRF analyzer. In this case personal samples were taken at a bronze foundry where lead is added to an alloy of copper, zinc and iron to improve casting, using the closed-face 37 mm cassette, the 37 mm GSP or "cone" sampler, the 25 mm Institute of Occupational Medicine (IOM) inhalable sampler, the 25 mm Button sampler, and the open-face 25 mm cassette. Mixed cellulose-ester filters were used in all samplers. Following XRF analysis the samples were extracted with acid and analyzed by inductively coupled plasma optical emission spectroscopy (ICP). For lead, all five samplers gave correlations (r(2)) greater than 0.9 between the two analytical methods over the entire range of found lead mass, which encompassed both the action level and the permissible exposure limit enforced in the USA by the Occupational Safety and Health Administration (OSHA). However, a correction was required to adjust linear regression trendlines to give a 1 : 1 correlation for the average of three readings across the GSP sampler, and a similar correction was required for the single readings from the IOM sampler and the 25 mm filter cassette. The bias possibly is due to interference from other metals, possibly copper which can absorb the fluorescent radiation of lead. In the case of the Button sampler, the bias is larger, indicating a further source of error, perhaps due to the thickness of the deposit. However, in all cases, correction of the lead results did not greatly affect the overall percentage of samples where the XRF result was within 25% of the ICP result, although it did improve the overall accuracy of the results. The GSP, IOM and Button samplers are suitable candidates for further evaluation as compatible with on-site XRF analysis for lead and other metals. It is important to check carefully factory pre-set instrument calibrations, as a bias in the calibration for copper was observed.     

A comparison of X-ray fluorescence and wet chemical analysis of air filter samples from a scrap lead smelting operation

Personal and area air samples were taken at a scrap lead smelter operation in a bullet manufacturing facility. Samples were taken using the 37-mm styrene-acrylonitrile closed-face filter cassette (CFC, the current US standard device for lead sampling), the 37-mm GSP or "cone" sampler, the 25-mm Institute of Occupational Medicine (IOM) inhalable sampler, and the 25-mm Button sampler (developed at the University of Cincinnati). Polyvinylchloride filters were used for sampling. The filters were pre- and post-weighed, and analyzed for lead content using a field-portable X-ray fluorescence (XRF) analyzer. The filters were then extracted with dilute nitric acid in an ultrasonic extraction bath and the solutions were analyzed by inductively coupled plasma optical emission spectroscopy. The 25-mm filters were analyzed using a single XRF reading, while three readings on different parts of the filter were taken from the 37-mm filters. The single reading from the 25-mm filters was adjusted for the nominal area of the filter to obtain the mass loading, while the three readings from the 37-mm filters were inserted into two different algorithms for calculating the mass loadings, and the algorithms were compared. The IOM sampler was designed for material collected in the body of the sampler to be part of the collected sample as well as that on the filter. Therefore, the IOM sampler cassettes were rinsed separately to determine if wall-loss corrections were necessary. All four samplers gave very good correlations between the two analytical methods above the limit of detection of the XRF procedure. The limit of detection for the 25-mm filters (5 microg) was lower than for the 37-mm filters (10 microg). The percentage of XRF results that were within 25% of the corresponding ICP results was evaluated. In addition, the bias from linear regression was estimated. Linear regression for the Button sampler and the IOM sampler using single readings and the GSP using all tested techniques for total filter loading gave acceptable XRF readings at loadings equivalent to sampling at the OSHA 8-hour Action Level and Permissible Exposure Limit. However, the CFC only had acceptable results when the center reading corrected for filter area was used, which was surprising, and may be a result of a limited data set. In addition to linear regression, simple estimation of bias indicated reasonable agreements between XRF and ICP results for single XRF readings on the Button sampler filters, (82% of the individual results within criterion), and on the IOM sampler filters (77% or 61%--see text), and on the GSP sampler filters using the OSHA algorithm (78%). As a result of this pilot project, all three samplers were considered suitable for inclusion in further field research studies.     

A comparison of X-ray fluorescence and wet chemical analysis for lead on air filters from different personal samplers used in a secondary lead smelter/solder manufacturer

Portable X-ray fluorescence (XRF) technology may provide faster turn-around without compromising accuracy when assessing personal exposures to metals such as lead, but it has only been tested in limited field environments. This study is part of a series, where various types of sampler are used to collect airborne lead in different environments for presentation to a portable XRF analyzer. In this case personal samples were taken at a manufacturer of solder alloys consisting mainly of lead and tin, using the closed-face 37 mm cassette (CFC), the 37 mm GSP or "cone" sampler, the 25 mm Institute of Occupational Medicine (IOM) inhalable sampler, the 25 mm button sampler, and the open-face 25 mm cassette. Mixed cellulose-ester filters were used in all samplers. Following XRF analysis the samples were extracted with acid and analyzed by inductively coupled plasma optical emission spectroscopy (ICP). The internal surfaces of CFC's and 25 mm open-face cassettes were also wiped, and the wipes analyzed for lead to assess wall-losses in these two samplers. Analysis of all elements present is useful to ascertain contributions to matrix interference effects. In addition to lead, other metals such as tin, copper, iron, silver, cadmium and antimony were also detected in some or all of the samples by ICP analysis, but only copper and iron could be determined using the XRF analyzer under test. After the removal of a few outliers, all five samplers gave good correlations (r(2) > 0.9) between the two analytical methods over the entire range of found lead mass, which encompassed both the action level and the permissible exposure limit enforced in the USA by the Occupational Safety and Health Administration (OSHA). Linear regression on the results from most samplers gave almost 1 ratio 1 correlations without additional correction, indicating an absence of matrix effects, particularly from tin, which was the most common element after lead. The average of three XRF readings across filters from the GSP samplers gave the best results with 96.7% of results within +/-25% and 100% within +/-30% of the associated ICP values. Using the center reading only was almost as good with 90.0% of results within +/-25% and 96.7% within +/-30% of the associated ICP values, and results can be obtained faster with a single reading. The use of an algorithm developed by OSHA for three readings from the CFC filter samples gave the next best results with 93.3% of XRF results within +/-25% of the corresponding ICP values. However, analysis of wipes from the interior of the cassettes indicated a substantial loss of sample to the walls, and even larger wall-losses were encountered in the 25 mm open-face cassette. Neither this latter sampler nor the IOM or button sampler met the 95% criterion, even for +/-30% accuracy.     

Comparison of wood-dust aerosol size-distributions collected by air samplers

A method has been described previously for determining particle size distributions in the inhalable size range collected by personal samplers for wood dust. In this method, the particles collected by a sampler are removed, suspended, and re-deposited on a mixed cellulose-ester filter, and examined by optical microscopy to determine particle aerodynamic diameters. This method is particularly appropriate to wood-dust particles which are generally large and close to rectangular prisms in shape. The method was used to investigate the differences in total mass found previously in studies of side-by-side sample collection with different sampler types. Over 200 wood-dust samples were collected in three different wood-products industries, using the traditional 37 mm closed-face polystyrene/acrylonitrile cassette (CFC), the Institute of Occupational Medicine (IOM) inhalable sampler, and the Button sampler developed by the University of Cincinnati. Total mass concentration results from the samplers were found to be in approximately the same ratio as those from traditional long-term gravimetric samples, but about an order of magnitude higher. Investigation of the size distributions revealed several differences between the samplers. The wood dust particulate mass appears to be concentrated in the range 10-70 aerodynamic equivalent diameter (AED), but with a substantial mass contribution from particles larger than 100 microm AED in a significant number of samples. These ultra-large particles were found in 65% of the IOM samples, 42% of the CFC samples and 32% of the Button samples. Where present, particles of this size range dominated the total mass collected, contributing an average 53% (range 10-95%). However, significant differences were still found after removal of the ultra-large particles. In general, the IOM and CFC samplers appeared to operate in accordance with previous laboratory studies, such that they both collected similar quantities of particles at the smaller diameters, up to about 30-40 [micro sign]m AED, after which the CFC collection efficiency was reduced dramatically compared to the IOM. The Button sampler collected significantly less than the IOM at particle sizes between 10.1 and 50 microm AED. The collection efficiency of the Button sampler was significantly different from that of the CFC for particle sizes between 10.1 and 40 microm AED, and the total mass concentration given by the Button sampler was significantly less than that given by the CFC, even in the absence of ultra-large particles. The results are consistent with some relevant laboratory studies.     

An evaluation of total and inhalable samplers for the collection of wood dust in three wood products industries

In 1998 the American Conference for Governmental Industrial Hygienists (ACGIH) proposed size selective sampling for wood dust based on the inhalable fraction. Thus the proposed threshold limit values (TLVs) require the use of a sampler whose performance matches the inhalable convention. The Institute of Occupational Medicine (IOM) sampler has shown good agreement with the inhalable convention under controlled conditions, and the Button sampler, developed by the University of Cincinnati, has shown reasonable agreement in at least one laboratory study. The Button sampler has not been previously evaluated under wood working conditions, and the IOM has been shown to sample more mass than expected when compared to the standard closed-face cassette, which may be due to the collection of very large particles in wood working environments. Some projectile particles may be > 100 microm aerodynamic diameter and thus outside the range of the convention. Such particles, if present, can bias the estimates of concentration considerably. This study is part of an on-going research focus into selecting the most appropriate inhalable sampler for use in these industries, and to examine the impact of TLV changes. This study compared gravimetric analyses (National Institute of Occupational Safety and Health Method 0500) of side-by-side personal samples using the Button, IOM, and 37 mm closed-face cassette (CFC) under field-use conditions. A total of 51 good sample pairs were collected from three wood products industries involved in the manufacturing of cabinets, furniture, and shutters. Paired t-tests were run on each sample pair using Statistical Package for the Social Sciences (SPSS) version 10. The IOM and the CFC measured statistically different concentrations (p < 0.0005, n = 16). The IOM and Button measured statistically different concentrations (p = 0.020, n = 12). The Button and CFC did not measure statistically different concentrations of wood dust (p = 0.098, n = 23). Sampler ratios for IOM/CFC pairs ranged from 1.19-19 (median 3.35). Sampler ratios for IOM/Button pairs ranged from 0.49-163 (median 3.15). Sampler ratios for CFC/Button pairs ranged from 0.36-27 (median 1.2). In all cases, higher ratios were associated with higher concentrations. The median relative difference between the IOM's and CFC's is in accord with prior field studies in woodworking environments, and, taken together, the data imply a conversion factor greater than the 2.5 normally applied to CFC results to approximate inhalable values, as measured by the IOM. Raising the limit values by approximately 50% appears warranted for this particular situation of inhalable wood dust measured by the IOM. The IOM/Button and CFC/Button ratios were unexpectedly low, which may be due to the exclusion of very large particles, collected by the IOM and CFC samplers. Further work is required to explain these results.     

Portable XRF analysis of occupational air filter samples from different workplaces using different samplers: final results, summary and conclusions

This paper concludes a five-year program on research into the use of a portable X-ray fluorescence (XRF) analyzer for analyzing lead in air sampling filters from different industrial environments, including mining, manufacturing and recycling. The results from four of these environments have already been reported. The results from two additional metal processes are presented here. At both of these sites, lead was a minor component of the total airborne metals and interferences from other elements were minimal. Nevertheless, only results from the three sites where lead was the most abundant metal were used in the overall calculation of method accuracy. The XRF analyzer was used to interrogate the filters, which were then subjected to acid digestion and analysis by inductively-coupled plasma optical-emission spectroscopy (ICP-OES). The filter samples were collected using different filter-holders or "samplers" where the size (diameter), depth and homogeneity of aerosol deposit varied from sampler to sampler. The aerosol collection efficiencies of the samplers were expected to differ, especially for larger particles. The distribution of particles once having entered the sampler was also expected to differ between samplers. Samplers were paired to allow the between-sampler variability to be addressed, and, in some cases, internal sampler wall deposits were evaluated and compared to the filter catch. It was found, rather surprisingly, that analysis of the filter deposits (by ICP-OES) of all the samplers gave equivalent results. It was also found that deposits on some of the sampler walls, which in some protocols are considered part of the sample, could be significant in comparison to the filter deposit. If it is concluded that wall-deposits should be analyzed, then XRF analysis of the filter can only give a minimum estimate of the concentration. Techniques for the statistical analysis of field data were also developed as part of this program and have been reported elsewhere. The results, based on data from the three workplaces where lead was the major element present in the samples, are summarized here. A limit of detection and a limit of quantitation are provided. Analysis of some samples using a second analyzer with a different X-ray source technology indicated reasonable agreement for some metals (but this was not evaluated for lead). Provided it is only necessary to analyze the filters, most personal samplers will provide acceptable results when used with portable XRF analysis for lead around applicable limit values.     

Determining particle size distributions in the inhalable size range for wood dust collected by air samplers

In the absence of methods for determining particle size distributions in the inhalable size range with good discrimination, the samples collected by personal air sampling devices can only be characterized by their total mass. This parameter gives no information regarding the size distribution of the aerosol or the size-selection characteristics of different samplers in field use conditions. A method is described where the particles collected by a sampler are removed, suspended, and re-deposited on a mixed cellulose-ester filter, and examined by optical microscopy to determine particle aerodynamic diameters. This method is particularly appropriate to wood dust particles which are generally large and close to rectangular prisms in shape. Over 200 wood dust samples have been collected in three different wood-products industries, using the traditional closed-face polystyrene/acrylonitrile cassette, the Institute of Occupational Medicine inhalable sampler, and the Button sampler developed by the University of Cincinnati. A portion of these samples has been analyzed to determine the limitations of this method. Extensive quality control measures are being developed to improve the robustness of the procedure, and preliminary results suggest the method has an accuracy similar to that required of National Institute for Occupational Safety and Health (NIOSH) methods. The results should provide valuable insights into the collection characteristics of the samplers and the impact of these characteristics on comparison of sampler results to present and potential future limit values. The NIOSH Deep South Education and Research Center has a focus on research into hazards of the forestry and associated wood-products industry, and it is hoped to expand this activity in the future.     

Air sampling of fungal spores on filters. An investigation on passive sampling and viability

In this study, glycerol was tested as a collection substrate for passive bioaerosol sampling. Filters (mixed cellulose acetate and nitrate) were soaked in glycerol and exposed for an aerosol from three different fungal species: Penicillum commune, Aspergillus versicolor and Paecilomyces variotii. The passive sampling method was compared with a closed-face polycarbonate filter sampling method. Exposure was performed in an exposure chamber. The total number of spores was determined by microscopic techniques, and the cultivable number was determined by cultivation on Malt Extract Agar dishes. The glycerol soaked filter demonstrated a good correlation with the closed-face sampler with regard to the total count. Spores stored in a pumped filter cassette were not affected by storage for up to 7 days. On the other hand, the culturability of the spores was markedly decreased after 1 day when stored on glycerol soaked filters.     

Comparison of PM10 concentrations in high- and medium-volume samplers in a desert environment

The USEPA replaced TSP with PM₁₀ as the National Ambient Air Quality Standard for particulate matter. The commercially available PM₁₀ sampler is a high-volume model using quartz fiber filters. In certain investigations, such as source apportionment studies, chemical analysis of the filter is necessary, however, many analyses cannot be run on quartz filters. An alternate filter such as Teflon is amenable to XRF and ion chemical analyses but is not amenable to analysis for carbon. To overcome these problems DRI constructed a medium-volume PM₁₀ sampler that is capable of collecting particulates on both Teflon and quartz fiber filters simultaneously. This paper describes the design of the DRI medium-volume PM₁₀ sampler, discusses a method for determining equivalence of two samplers, the results of applying the method to test the equivalence of the medium-volume sampler and a commerical high-volume sampler, and examines differences between PM₁₀ and TSP measurements in a southwestern desert.     

Field comparison of three inhalable samplers (IOM, PGP-GSP 3.5 and Button) for welding fumes

Inhalable sampler efficiency depends on the aerodynamic size of the airborne particles to be sampled and the wind speed. The aim of this study was to compare the behaviour of three personal inhalable samplers for welding fumes generated by Manual Metal Arc (MMA) and Metal Active Gas (MAG) processes. The selected samplers were the ones available in Spain when the study began: IOM, PGP-GSP 3.5 (GSP) and Button. Sampling was carried out in a welding training center that provided a homogeneous workplace environment. The static sampling assembly used allowed the placement of 12 samplers and 2 cascade impactors simultaneously. 183 samples were collected throughout 2009 and 2010. The range of welding fumes' mass concentrations was from 2 mg m(-3) to 5 mg m(-3). The pooled variation coefficients for the three inhalable samplers were less than or equal to 3.0%. Welding particle size distribution was characterized by a bimodal log-normal distribution, with MMADs of 0.7 μm and 8.2 μm. For these welding aerosols, the Button and the GSP samplers showed a similar performance (P = 0.598). The mean mass concentration ratio was 1.00 ± 0.01. The IOM sampler showed a different performance (P < 0.001). The mean mass concentration ratios were 0.90 ± 0.01 for Button/IOM and 0.92 ± 0.02 for GSP/IOM. This information is useful to consider the measurements accomplished by the IOM, GSP or Button samplers together, in order to assess the exposure at workplaces over time or to study exposure levels in a specific industrial activity, as welding operations.     

Airborne endotoxin in woodworking (joinery) shops

Symptoms such as shortness of breath and cough have been noted in woodworking facilities even where wood dust itself is well-controlled. Suspicion has fallen on other possible contaminants in the workplace atmosphere, including bacterial endotoxin. A few studies have indicated potentially high endotoxin exposure with exposure to fresh wood in sawmills and in the production of fiberboard and chipboard, but fewer studies have been carried out on exposure to endotoxin in dry wood work, for example in joineries. A study of the endotoxin content of airborne wood dust samples from US woodworking facilities is presented, from the re-analysis of samples which previously had been taken to establish mass collection relationships between the IOM sampler, the closed-face 37 mm plastic cassette (CFC) sampler and the Button sampler. Endotoxin was strongly correlated with total dust, but the endotoxin content of a few fresh wood samples was found to be up to ten times higher per unit of wood dust than for dried-wood samples, and this difference was significant. No long-term time-weighted average sample exceeded the recommended limit value of 50 EU m(-3) (EU, endotoxin units)used in the Netherlands, although a number of the IOM samples came close (seven samples or 44% exceeded 20 EU m(-3)) and one short-term (48 minute) sample registered a high value of 73 EU m(-3). The geometric mean concentration from the IOM samples (11 EU m(-3)) is within the range of geometric means found from Australian joineries (3.7-60, combined: 24 EU m(-3)). In contrast, the corresponding values from the CFC (3.6 EU m(-3)), and the Button sampler (2.1 EU m(-3)) were much lower and no samples exceeded 20 EU m(-3). Endotoxin is likely only to be a significant problem in working with dried woods when associated with very high dust levels, where the wood dust itself is likely to be a cause for concern. The results from the few samples in this study where fresh wood was being worked were similar to results from other studies involving fresh woods. The agreement between these studies is encouraging given the difficulties of endotoxin analysis and the wide variation often expected between different laboratories.     

Influence of environmental parameters on the accuracy of nitrogen dioxide passive diffusion tubes for ambient measurement

Two studies at three sites in the UK provided confirmation that systematic positive bias in NO2 diffusion tube measurement occurred because of changes to "within-tube" chemistry, rather than eddy diffusion at the mouth of the tube. In the first study in Cambridge, UK, sampler overestimation for 1 and 2 week exposures was compared to corresponding time-averaged monitor measurements (NO-NO2-NOx, O3) and weather variables. Noninearity between sampler and monitor NO2 measurements was interpreted in terms of spatial and temporal variations in relative and absolute availability of NO, NO2 and O3 at the site. A maximum overestimation occurred for an exposure mean NO2/NOx approximately 0.5. The separate contributions of reduced NO2 photolysis and eddy diffusion were compared in Study II using samplers of two materials, acrylic and quartz, and of different lengths (40, 55, 71 and 120 mm) at three sites: Norwich background, Cambridge intermediate, London kerbside. For compared sites, NO2 measured by acrylic samplers was significantly higher than for equivalent quartz samplers. For quartz samplers [NO2]mean was only just above the monitor at Norwich and London; sampler/monitor NO2 = 1.04 (P = 0.59) and 1.01(P = 0.76), respectively. For acrylic samplers the order of [NO2]mean was 40 mm > 120 mm > 71 mm > or = 55 mm. Excepting 40 mm samplers, this accords with a chemical bias where co-diffusing NO and 03 molecules in longer tubes have more time to react to form excess NO2. Bias in 40 mm samplers is discussed. Eddy diffusion is negligible for standard samplers because [NO2]mean was equivalent for 55 mm and 71 mm acrylic samplers and close to monitor NO2 for 71 mm quartz tubes. Both studies showed that sampler accuracy was dependent on location. Significantly, overestimation was greatest (approximately 3-4 ppb) where the NO2 annual mean was approximately 20 ppb, close to the UK and EU air quality standard of 21 ppb.     

A comparison of methods and materials for the analysis of leaded wipes

The purposes of this study are: (1) to determine whether proficiency analytical test (PAT) materials from the American Industrial Hygiene Association can be used to provide quality data for portable X-ray fluorescence analysis (XRF) of lead in dust wipe surface samples; (2) to provide data to determine whether the on-site analysis of field dust wipe samples by XRF and the laboratory method of inductively coupled plasma emission analysis (ICP) are comparable; and (3) to determine if differences exist between different wipe materials. Several wipes meet the ASTM E1792 performance requirements of lead background level less than 5 microg per wipe, be only one layer thick, yield recovery rates of 80- 120% from spiked samples, remain damp throughout the sampling procedure, and do not contain aloe. The wipes used in this study were Pace Wipes, which are used for the PAT materials, and, for the field samples, Palintest Wipes, which were supplied by the instrument manufacturer, and Ghost Wipes, which are popular because they digest in hot, concentrated acid, so that chemical analysis is simplified. Twenty PAT wipe samples were obtained from four different proficiency test rounds. Surface wipe samples were taken at three different locations representing different industry types. All samples were analyzed using a portable XRF spectrometer and by ICP. Strong linear relationships were found for the analysis of wipe samples by ICP and by portable XRF. For the PAT samples, the results from the ICP and XRF analysis were not statistically equivalent, which indicates a bias in the ICP analysis. The bias was not excessive, since all ICP analyses fell within the acceptable range for the proficiency samples. The good correlation between the proficiency sample reference values and the XRF determinations is not surprising considering similar proficiency samples were used to calibrate the instrument response. Users of this portable XRF analyzer could enroll in the proficiency test program as part of their quality assurance program. For field samples, the relationship was strongest for Palintest wipes, and the values found for all three industries could be combined. However, the results from the ICP and XRF analysis were not statistically equivalent using the correction factor in the calculation algorithm as supplied with the instrument, and a new coefficient was derived. The mean relative error for the XRF analysis versus the ICP analysis was greater than 25%, such that the method falls within the realm of screening procedures. For Ghost Wipe samples, the precision was different for different industries, and the results could not be pooled. Differences between the two wipe materials may be related to the number of folds required for analysis.     

Laboratory and field validation of a combined NO2-SO2 Radiello passive sampler

A combined NO2-SO2 Radiello radial-type diffusive sampler was validated under controlled laboratory conditions and compared with NO2-SO2 results of 3 other type of samplers in a field comparison at two locations Ghent-Mariakerke and Borgerhout in Flanders. Laboratory exposures at different temperatures (-5, 10 and 30 degrees C) and relative humidities (0, 50 and 80% RH) in combination with varying concentration levels and exposure times were carried out, with a focus on extreme conditions. Concentration level and exposure time were changed together following suppliers linear working range of samplers and assuring absolute amounts of compounds on the sampler corresponding to those of environmental levels. The average uptake rate for NO2 for 24 hour exposures at 10 degrees C and 50% RH and tested concentration levels (+/-73, 146 and 293 ppb NO2) was 0.076 +/- 0.011 ng ppb(-1) min(-1). Uptake rates during all experiments were lower than the uptake rate given in the instruction manual of the sampler. A significant effect of temperature and relative humidity on NO2 uptake rate was observed. The temperature effect from 10 to 30 degrees C corresponds to the temperature effect given by the supplier of the samplers. High relative humidity (70 to 80%) caused a strong non-reproducible decrease of uptake rate for NO2 at 24 hour experiments but this effect was not observed at longer exposures except for the tests at -5 degrees C. At the tested temperature below zero in combination with high relative humidity the sampler showed anomalous behaviour for NO2. The possible effect of concentration level and exposure time for NO2 needs further research. The average uptake rate for SO2 calculated from all exposures is 0.478 +/- 0.075 ng of sulfate ion each ppb min of SO2 and accords to suppliers uptake rate. No clear effects of temperature, relative humidity or concentration level/exposure time on the uptake rate for SO2 were found, partly due to the large scatter of results. Although NO2 accuracy of Radiello samplers was better during field campaigns than during laboratory validation, IVL and OGAWA samplers gave better results for NO2. In the field, IVL samplers showed best agreement with the continuous analyzers for both NO2 and SO2.     

Field evaluation of a tailor-made new passive sampler for the determination of NO2 levels in ambient air

This study describes the field evaluation of a tailor-made new glass passive sampler developed for the determination of NO(2), based on the collection on triethanolemine (TEA)-coated fibre filter paper. The sampler has been derived from a Palmes design. The overall uncertainty of the sampler was determined by using Griess-Saltzman ASTM D 1607 standard test method as a reference method. The agreement between the results of the passive sampler and the reference method was +/-7.90% with the correlation coefficient of 0.90. Method precision in terms of coefficient of variance (CV) for three simultaneously applied passive samplers was 8.80%. The uptake rate of NO(2) was found to be 2.49 ml/min in a very good agreement with the value calculated from theory (2.63 ml/min). Sampler detection limit was 1.99 microg/m(3) for an exposure period of 1 week and the sampler can be stored safely for a period of up to 6 weeks before exposure. A comparison of the sampler performance was conducted against a commercially available diffusion tube (Gradko diffusion tube). The results from the applied statistical paired t test indicated that there was no significant difference between the performances of two passive samplers (R (2) > 0.90). Also, another statistical comparison was carried out between the dark and transparent glass passive samplers. The results from the dark-colour sampler were higher than that from the transparent sampler (approximately 25%) during the summer season because of the possible photodegradation of NO(2)-TEA complex.     

铅蓄电池企业废气中铅及其化合物便携式XRF检测方法

在企业污染源现场实现污染物排放浓度水平的快速判定和超标风险筛查,对生态环境管理部门提高执法效率、企业提高环境管理水平意义重大。铅是一种对人体危害极大的有毒重金属,目前缺少含铅废气中铅及其化合物的便携式直读检测设备和检测方法。探索性地将X射线荧光光谱(XRF)法应用于铅蓄电池企业含铅废气中铅及其化合物的便携式快速、直读检测。研究结果表明,基于XRF的面密度法适用于铅蓄电池企业含铅废气处理设施后铅及其化合物的快速、直读检测,相对国标方法具有快速、直读、对样品无损、便于复测等特点,可用于铅及其化合物排放浓度水平的快速判定和超标风险筛查。     

Determination of the dialdehyde glyoxal in workroom air-development of personal sampling methodology

The dialdehyde glyoxal (ethanedial) is an increasingly used industrial chemical with potential occupational health risks. This study describes the development of a personal sampling methodology for the determination of glyoxal in workroom air. Among the compounds evaluated as derivatizing agents; N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH), 1,2-phenylenediamine (OPDA), 1-dimethylaminonaphthalene-5-sulfonylhydrazine (dansylhydrazine, DNSH) and 2,4-dinitrophenylhydrazine (DNPH), DNPH was the only reagent that was suitable. Several different samplers were evaluated for sampling efficiency of glyoxal in workroom air using DNPH as derivatizing agent; in-house DNPH coated silica particles packed in two different types of glass tubes, impingers containing acidified DNPH solution, filter cassettes containing glass fibre filters coated with DNPH, a commercially available solid phase cartridge sampler originally developed for formaldehyde sampling (Waters Sep-Pak DNPH-silica cartridge), and the commercially available SKC UMEx 100 passive sampler originally developed for formaldehyde sampling. Aldehyde atmospheres for sampler evaluation were generated with an in-house made vapour atmosphere generator coupled to a sampling unit, with the possibility of parallel sampling. The resulting glyoxal-DNPH derivative was determined using both LC-UV and LC-APCI-MS with negative ionization. By far, the highest recovery of glyoxal was obtained employing one of the in-house DNPH coated silica samplers (93%, RSD = 3.6%, n = 12).     

New experimental methods for the development and evaluation of aerosol samplers

An understanding of the scaling laws governing aerosol sampler performance leads to new options for testing aerosol samplers at small scale in a small laboratory wind tunnel. Two methods are described in this paper. The first involves an extension of what is referred to as the "conventional" approach, in which scaled aerosol sampler systems are tested in a small wind tunnel while exposed to relatively monodisperse aerosols. Such aerosols are collected by test and reference samplers respectively and assessed gravimetrically. The new studies were carried out for a modified, low flowrate version of the IOM personal inhalable aerosol sampler. It was shown that such experiments can be carried out with a very high level of repeatability, and this supported the general validity of the aerosol sampler scaling laws. The second method involves a novel testing system and protocol for evaluating the performances of aerosol samplers. Here, scaled aerosol samplers of interest are exposed to polydisperse aerosols, again in a small wind tunnel. In this instance, the sampled particles are counted and sized using a direct-reading aerodynamic particle sizer (the APS). A prototype automated aerosol sampler testing system based on this approach was built and evaluated in preliminary experiments to determine the performance of another modified version of the IOM personal inhalable aerosol sampler. The design of the new test system accounts for the complex fluid mechanical coupling that occurs near the sampler inlet involving the transition between the external flow outside the sampler and the internal airflow inside the sampler, leading in turn to uncontrolled particle losses. The problem was overcome by the insertion of porous plastic foam plugs. where the penetration characteristics are well understood, into the entries of both the test and the reference samplers. Preliminary experiments with this new system also supported the general validity of the aerosol sampler scaling laws. In addition, they demonstrated high potential that this approach may be applied in a standardised aerosol testing method and protocol.     

The equivalence of diffusive samplers to reference methods for monitoring O3, benzene and NO2 in ambient air

A study of the equivalence to the reference methods of the Radiello samplers for ozone (O(3)) and benzene as well as the membrane-closed Palmes tube (MCPT) for nitrogen dioxide (NO(2)) is presented. These samplers benefit from new model equations capable of estimating their uptake rate. For O(3), the aim here was to demonstrate the equivalence for the reference period of 8 h and 120 microg m(-3), the target value of the 3rd European Daughter Directive. For benzene, the demonstration of equivalence to the annual limit value of 5 microg m(-3) of the 2nd European Daughter Directive was examined. In the case of NO(2), the equivalence to the annual limit value of the 1st European Daughter Directive (40 microg m(-3)) was considered. Results show that the radial sampler for O(3) fails to meet the Data Quality Objective (DQO) for continuous monitoring. However, with an expanded uncertainty of less than 30%, the O(3) diffusive sampler fulfils the DQO for indicative measurements. For benzene, the Radiello sampler exposed for 7 days gave satisfying results showing the ability of the sampler to meet the DQO of the reference method. Nevertheless, the field tests should be complemented by measurements for a wider range of benzene concentrations. In the case of NO(2), all the results of the laboratory and field experiments respected the requirements necessary for the demonstration of equivalence. Overall, these findings thus show that the Radiello sampler and the MCPT are equivalent to the reference methods only for assessment of benzene and NO(2), respectively.     

Further studies using X-ray fluorescence to sample lead contaminated carpeted surfaces

The sampling of carpeted surfaces to test for lead contamination primarily focuses upon vacuum techniques. Vacuum sampling techniques, however, require time-consuming, expensive laboratory analysis of the dusts obtained and are unable to determine total lead load on the carpet. X-ray fluorescence (XRF) analysis is an on-site, inexpensive, non-destructive, quick technique for predicting metals levels in a variety of media, such as water, soil, filter paper and painted surfaces. A 1992 study of the feasibility of XRF to analyze for lead and soil loadings on carpeted surfaces indicated that XRF can detect lead at a low enough level to warrant further study. This paper expands this earlier study and developes lead and soil loading calibration curves for three different carpet types based upon XRF lead L-beta peak areas and XRF iron and barium K-alpha peak and background areas. Results indicate that variation in the data can be reduced through modifications of the XRF analysis technique, thus reducing the statistically determined detection level, and that carpet type does affect the calibration. Detection levels of approximately 70 mg/m² for lead and 5 g/m² for soil were obtained. Overall, good agreement was found between results of this study and the earlier one. XRF shows excellent potential for quantitative analysis of lead on carpeted surfaces.