Comparison of different types of filters for atmospheric trace element analysis by three analytical methods

Different atmospheric aerosol samples were collected on three types of filters. From both of the loaded and clean areas of each kind of filter, different disks were cut and investigated by XRF, PIXE and scanning electron microscopy (SEM). The blank concentration values of the elements Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br and Pb in the three types of filter are discussed. It is found that for trace elemental analysis, the Nuclepore membrane filters are the most suitable for sampling. These filters have much lower blank element concentrations than the glass fiber and ash free filters. It was found also that PIXE is a more reliable analytical technique for atmospheric aerosol particles than the other methods used.     

Investigation of different types of filters for atmospheric trace elements analysis by three analytical techniques

Different atmospheric aerosol samples were collected on three types of filters. Disks of both loaded and clean areas of each kind of filter were investigated by XRF, PIXE and Scanning Electron Microscope (SEM) methods. The blank concentration values of the elements Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br and Pb in the three types of fiters are discussed. It is found that for trace elemental analysis, the Nuclepore membrane filters are the most suitable for sampling. These have much lower blank element concentration values than the glass fibres and ash free filters. It was found also that the PIXE method is a more reliable analytical technique for atmospheric aerosol particles than the other methods.     

Development of a versatile,easy and rapid atmospheric monitor for benzene,toluene, ethylbenzene and xylenes determination in air

A new procedure for the passive sampling in air of benzene, toluene, ethylbenzene and xylene isomers (BTEX) is proposed. A low-density polyethylene layflat tube filled with a mixture of solid phases provided a high versatility tool for the sampling of volatile compounds from air. Several solid phases were assayed in order to increase the BTEX absorption in the sampler and a mixture of florisil and activated carbon provided the best results. Direct head-space-gas chromatography–mass spectrometry (HS-GC–MS) measurement of the whole deployed sampler was employed for a fast determination of BTEX. Absorption isotherms were used to develop simple mathematical models for the estimation of BTEX time-weighted average concentrations in air. The proposed samplers were used to determine BTEX in indoor air environments and results were compared with those found using two reference methodologies: triolein-containing semipermeable membrane devices (SPMDs) and diffusive Radiello samplers. In short, the developed sampling system and analytical strategy provides a versatile, easy and rapid atmospheric monitor (VERAM).     

Neutron activation analysis: Still a reference method for air particulate matter measurements

At ITN, PM10 and PM2.5 aerosols were collected on Nuclepore^® polycarbonate filters of 47 mm diameter, using Gent samplers at 15–17 l/min air flux. Filters were analyzed by INAA and PIXE. The availability of certified filters was very scarce, viz.: (1) fly ash embedded in a methyl cellulose 47 mm foil 10 µm thick, BCR CRM128, (2) particle-size reduced air particulate matter (APM) to simulate PM2.5 aerosol matter deposited on a 47 mm polycarbonate filter membrane, NIST SRM 2783. The high price and scarcity of APM standards did not permit their frequent use for analytical quality control. At ITN, to control the filter results' accuracy, the chemical elements potassium, iron and zinc, determined by both techniques, were systematically compared. After a few improvements introduced in INAA, this technique was now considered at ITN as the reference technique in air particulate measurements. Comparison of INAA to PIXE was discussed. Compared to previously reported situation it was concluded that the results were in better agreement for iron and zinc, and potassium values were still biased to the same extent as before.     

Comparison of methods for particulate phase mercury analysis: sampling and analysis

Accurate and reliable sampling and analysis of mercury forms is an overriding aim of any atmospheric monitoring effort which seeks to understand the fate and transport of the metal in the environment. Although a fraction of the total mercury forms found in the atmosphere, particulate phase mercury, Hg(p), is believed to play a prominent role in both wet and dry deposition to the terrestrial and aquatic environments. Currently, microwave acid extraction and thermoreductive methodologies for analysis of Hg(p) samples are widely used. We report on the potential for the use of a thermoreductive method for Hg(p) analysis to evaluate and optimize it for use in routine monitoring networks. Pre-baked quartz filters can be placed in particulate samplers with well-characterized size cuts, such as dichotomous samplers and microoriface impactors. The thermoreductive methodology facilitates rapid analysis after sample collection. It requires no chemical extraction thereby eliminating the potential for contamination and generation of hazardous waste. Our results indicate that, on average, the thermoreductive method yields 30% lower values for fine fraction Hg(p) when compared with microwave acid digestion. This may be due to matrix interferents that reduce the collection efficiency of mercury onto gold preconcentration traps. Results for total particulate mercury samples indicate that on average the thermoreductive method yields 56% lower values for the coarse fraction when compared with microwave acid digestion.Experiments were also conducted in Detroit, MI, USA to investigate whether elevated reactive gaseous mercury (Hg(2+)(g)) in an urban environment can lead to an artifact during the collection of filters for Hg(p) analysis. Our results indicate a significantly higher amount of Hg(p) collected onto a filter using the conventional methodology as compared to a filter collected downstream of KCl-coated annular denuders in the absence of Hg(2+)(g). These results point to the presence of Hg(2+)(g) as an artifact during Hg(p) measurement. These results indicate that a denuder must be utilized upstream of a filter for Hg(p) collection to prevent significant Hg(2+)(g) artifact formation.     

The sampling of sulfur dioxide in air with impregnated filter paper

A method is suggested for the sampling of sulfur dioxide in air with impregnated filter paper instead of bubblers. The best aqueous impregnating solution contained potassium hydroxide with glycerol or triethanolamine. The possibilities and limitations of the method are discussed. High collection efficiencies (over 95%) were obtained at relative humidities above 25%. Collected sulfur dioxide was stable for at least several weeks when the filters were kept dry after the sampling. The method is especially suited for short-time measurements and for automatic sampling with smoke samplers.     

Atmospheric trace metal characterization in industrial area of Lisbon, Portugal

Summary A set of 15 atmospheric aerosol samples was collected in an industrial area of Lisbon, Portugal and then analyzed by instrumental neutron activation analysis (INAA). Both fine and coarse aerosol samples were collected during November and December 2001 on polycarbonate filters with Gent samplers. The INAA methodology utilized both thermal and epithermal neutron irradiations. Compton suppressed and normal gamma-ray spectra were acquired simultaneously for each measurement and the elemental concentrations of 30 elements were determined. Enrichment factors, wind speed comparison and receptor modeling techniques were applied to obtain the different source contributions of the aerosols. Crustal, marine and anthropogenic sources were identified. The anthropogenic elements have origin mainly in the area close to the sampling site (<5 km), with the exception of Ca and V. A direct relationship was observed between the anthropogenic atmospheric aerosol concentrations and wind speed.     

Characteristics of Size-Fractionated Urban Aerosols and Trace Gases in Budapest

An air pollution study was conducted at two urban residential sites in Budapest from 9 April to 17 May 1996. Size-fractionated aerosol samples were simultaneously collected on a daily basis, and meteorological conditions were recorded at both sampling sites. Stacked filter units (SFUs) with an upper size inlet cutoff were used as sampling devices separating the urban aerosol into coarse [about 2- to 10-μm equivalent aerodynamic diameter (EAD)] and fine (<2 μm EAD) size fractions. In addition, atmospheric concentrations of some criteria pollutants, i.e., NO, NO₂, SO₂, CO, and total mass of the suspended particulate matter (TSP) were measured every half-hour at one of the sampling sites with commercial equipment. The SFU filters were weighed and analyzed by a light reflectance technique, particle-induced X-ray emission analysis, and instrumental neutron activation analysis. Atmospheric concentrations for 31 aerosol species have been obtained so far. The analytical results were used to characterize the levels and the multielemental composition of the urban aerosol at both sampling sites and for both size fractions, to investigate the atmospheric concentrations and diurnal variation of the criteria pollutants, and to compare the time trends of aerosols and trace gases. The present paper reports on the status of the air pollution study and gives a discussion of the results.     

Improved analysis of Polycyclic Aromatic Hydrocarbons in atmospheric particulate matter by HPLC-fluorescence

An improved method is reported for determination of Polycyclic Aromatic Hydrocarbons (PAHs) in atmospheric particulate matter by HPLC-FLD. The sampling step (air volume collected during each sampling period varies in the range 10/13 m3) is carried out by means of a medium-flow pumping system (15 L min(-1)) on a glass fiber filter (47 mm diameter) placed as collecting substrate in the sampling-cassette. After sampling, the filter is extracted with 3 ml of acetonitrile in an ultrasonic bath for 30 minutes. As for extraction of PAHs from loaded filters a new criterion here is proposed to evaluate the recovery efficiency of PAHs from the sample, instead of the usual spiking method of standard solution. The extract was then reduced to 100 microL and analysed by HPLC-FLD on line spectra system. The method is rapid (about one hour for extraction and analysis), reproducible and enables to measure with good accuracy the atmospheric concentration of benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), benzo(ghi)perylene (BghiP), carcinogenic compounds always present in the urban airborne particulate matter. So it is useful for routine pollution studies and suitable to substitute the official method used now. Monthly average air concentrations, for the four PAHs above mentioned, measured in Rome from July 2001 to June 2002, are reported.     

Determination of atmospheric lead-210 by alpha-scintillation counting of air filters

Alpha-counting of filters used to sample large volumes of air provides a convenient way of determining atmospheric concentrations of²¹⁰Pb. Following decay of short-lived²²²Rn and²²⁰Rn progeny, alpha activity of the filters increases as²¹⁰Pb decays to²¹⁰Po. After transient equilibrium is reached at about 3 y, alpha activity diminishes with the 22.3 y halflife of²¹⁰Pb. The degree of equilibrium between²¹⁰Pb and²¹⁰Po can be calculated subsequent to sampling, and the average concentration of²¹⁰Pb in the air during the sampling period can be computed. Contributions to the total²¹⁰Pb from ambient short-lived radon progeny are small, typically 2–4%. Using high volume air samplers with collection rates of 1.1–1.7 m³/min for 24 h periods, and using counting times of 2 h for 20 cm² filter sections, we measured alpha counts ranging from 0.0100±0.0050 to 0.200±0.0200 dps. Periodic measurements on 100 of these filters over a 4 y period yielded mean²¹⁰Pb levels with standard deviations less than ±15%. The method requires minimal sample preparation and can be used to determine past atmospheric²¹⁰Pb concentrations on filters stored for up to 20 y and more.     

Quality control materials for the determination of trace elements in airborne particulate matter

The development of quality control materials for the determination of selected trace elements in air pollution studies is described. Three types of test samples were prepared for proficiency testing: (1) filters loaded with PM10 fraction of urban air particulate matter (APM) using high-volume air samplers, which were subsequently divided into smaller sections, (2) a bulk sample of APM collected in an automobile tunnel in Prague, and (3) simulated air filters loaded with APM using a wet deposition process. Homogeneity of the test samples was studied using instrumental neutron activation analysis, proton induced X-ray emission and atomic absorption spectrometry, and inductively coupled plasma optical emission spectrometry and mass spectrometry. Sufficiently homogeneous samples were prepared by all three procedures. The simulated air filters appeared to be the most suitable test samples for proficiency testing.     

Mercury and organotin compounds monitoring in fresh and marine waters across Europe by Chemcatcher passive sampler

Several field trials have been carried out to assess the performance of the passive sampler Chemcatcher as aquatic monitoring technology for inorganic mercury and the organotin pollutants monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in different types of waters across ten locations in Europe. Two version of the sampler were used. One for mercury that consists on 47?mm Empore? disks of iminodiacetic chelating groups as the receiving phase overlaid by a diffusion membrane of polyethersulphone; and other for organotin compounds comprising a C₁₈ disk and a cellulose acetate membrane. Both membranes were held in a disposable polycarbonate body. The two samplers were calibrated in the laboratory in a previous work to estimate the pollutant concentration. For field sampling, the samplers were deployed for 14 days. In parallel spot samples were periodically collected during the deployment period for comparison purposes. No significant biofouling on the samplers was observed for the locations monitored. In general, water concentrations estimated by Chemcatcher were lower than those found in spot water samples due to the device only collected the soluble bioavailable fraction of target pollutants. However, the pre-concentration capability of Chemcatcher allowed the determination of the tested pollutants at levels where spot sampling fails, even in difficult water bodies such as sewage treatment plants. These advantages lead to consider this emerging methodology as a complementary tool to traditional spot sampling.     

Radiometric efficiency of analytical filters at different physical conditions

The radiometric efficiency of three analytical filters AFA-RSP-20, AFA-RMP-20 and AFA-RMV-20 was examined at different air velocities and aerosol number concentrations. An experimental setup had been constructed with 2 m³ radon chamber. Alpha radiometry was used to measure the deposited activities in the filters. Aerosols parameters like number concentration and size distribution are measured continuously with an aerosol diffusion spectrometer (ADS). RMV filter has a stable efficiency ~ 99.8%. The RSP and RMP filters efficiency is depending on the aerosol concentration and air sampling velocity. The effect of an aerosol concentration on the filter efficiency is more obvious than the effect of air velocity.

     

Routine determination of major anions in atmospheric aerosols by capillary electrophoresis

Capillary electrophoresis (CE) with indirect UV detection utilizing a pyromellitate-based electrolyte was used for the routine analysis of major anions in atmospheric aerosols collected on filters with high-volume (Hi-Vol) samplers. The long-term reliability of the CE system was checked over an 8-month period during which over 2900 samples were analyzed. In addition, approximately 1100 samples were analyzed in parallel by ion chromatography (IC). It has been shown that acceptable analytical performance can be routinely obtained. The agreement between the CE and IC results is good, generally better than 20% at concentrations larger than 1 mg l⁻¹.     

Iron, manganese, copper and titanium in welding fume dust on filters for internal and external quality assurance

Summary Filters charged with welding fume dust were developed and produced for internal and external quality assurance to evaluate and improve the performance of analytical methods used for monitoring iron, manganese, copper and titanium in the working environment. The filters were simultaneously loaded, using a Sputnic air sampling unit containing 100 cellulose nitrate filters. The welding fume dust was collected in industrial working conditions where Metal Inert Gas welding in construction steel was being carried out. The metal concentrations on the filters were close to the metal concentrations from environmental and industrial exposure. The homogeneity of the filter materials was evaluated to document the suitability of the air sampler in producing quality control materials. The filters were homogeneous within 5.0–12.7% according to amount of metal. The welding fume dust loaded on the filters was (0.2021±0.0093 mg/filter) and the amounts of metals loaded on the filters were (34.6±6.4 g/filter, 16.0±0.8 g/filter, 2.4±0.1 g/filter) for iron, manganese and titanium, respectively. Normalizing the amount of metal according to the welding fume dust improved the homogeneity. The most satisfactory results were obtained for manganese and titanium, for which within batch variation was below 6.3%. The Sputnic air sampler was shown to be suitable in preparing quality control materials, although a few improvements are needed for future experiments, such as the method of charging the dust and rules for outlier exclusion.     

Determination of lead in atmospheric particulates by flameless atomic absorption spectrometry with a graphite tube

A procedure for the determination of atmospheric particulate lead by flameless atomic absorption spectrometry is described. Aerosols are collected on 10-cm Whatman 41 filters with high-volume pumps. The lead is removed from a one-eighth sector of the filter by two ultrasonic treatments in 0.1 M nitric acid for 10 and 5 min, respectively. Investigations, including comparison with samples pre-ashed at low temperature, indicated that the lead was completely recovered. Routinely 20-μ1 amounts of the solution are injected into a graphite tube and the % absorption at 283.3 nm is measured. The elements normally encountered in atmospheric aerosols do not interfere. The sensitivity for 24-h samples is 0.01 μg m^?3 of air. Sampling time can be reduced to a few minutes in urban air when a larger segment of the filter is used and a larger volume is injected. The reproducibility of the complete procedure is 3% for a typical lead concentration of 0.35 μg m^?3. The method was applied to short-period variations of the lead concentration in urban air.     

Mercury in atmospheric aerosols: A preliminary case study for the city of Krakow,Poland

The level of contamination by mercury associated with airborne particulate matter in Krakow was determined. Samples of PM10 were collected on quartz filters using low-volume samplers. The total particulate mercury (TPM) concentrations in collected samples were determined by mercury analyser MA-3000 (Nippon Instruments Corporation). The reported results include also data on the carbonaceous aerosol and inorganic ions concentrations during the reported sampling campaign. The average concentration of the Total Particulate Mercury (TPM) in Krakow (Poland) was 0.22 ng·m⁻³ (during the period from 22 February to 2 March) and 0.49 ng·m⁻³ (on 3 March). A marked correlation between TPM and elemental carbon (EC) as well as with Cl^– was found. No significant association of the TPM with NO₃^– and SO₄^2– could be shown. The dry deposition flux of mercury was calculated as an average over the sampling period and was 47.3 ng·m⁻²·d⁻¹.     

Examination of a procedure for the production of a simulated filter-based air particulate matter reference material

An approach for producing simulated air particulate matter (APM) deposited on filters has been developed and investigated as to its usefulness for yielding large batches of filters as a future reference material. The APM deposited on the filters was a material collected from an urban industrial area, and had been milled to approximate a material of PM-2.5 particle size distribution. The milled APM material was loaded onto filter substrates (Nuclepore) through the deposition of aliquots from a liquid suspension via vacuum filtration. It should be noted that these filters do not represent a typical PM-2.5 elemental composition, since the milling increased the proportion of crustal materials and the suspension in liquid decreased the sulfate content. Homogeneity between filters was tested using INAA (whole filter analysis) and ED-XRF and PIXE and was estimated to be in the 5% range (relative standard deviation). Homogeneity within the filters and among the filters was also tested using micro-XRF and found to be acceptable for the elements tested. The results of the tests carried out on the filters indicate that this approach is appropriate for large-scale production of similar filters for distribution as reference materials.     

Determination of the chemical composition of the South Pole aerosol by instrumental neutron activation analysis

Atmospheric particulate samples were collected at the geographic South pole, using cellulose and polycarbonate filters and cascade impactors. The samples were analysed for 40 elements by instrumental neutron activation analysis. From the filter samples atmospheric concentrations for 33 elements could be obtained. The highest atmospheric concentrations were found for S: 49 ng/standard cubic meter (SCM) of air, Na: 3.3 ng/SCM and Cl: 2.6 ng/SCM. In the cascade impactor samples, only a few elements were observed above blank. For these elements it could be concluded that they are associated for over 80–90% with submicron size paricles.     

Fractionation and Chemical Analysis of Urban Air Particulate Extracts

Abstract

Urban air samples were collected using Hi-Vol PM₁₀ samplers during 24 hours periods. Samples were collected from October 1993 to September 1994 both in Teplice and Prachatice and from October 1996 to April 1997 in Teplice, CR. Organic material (EOM) was extracted from filters with methylene chloride in a Soxhlet apparatus. Acid base partitioning of the crude extract was carried out and neutral compounds were further fractionated by silica gel column chromatography. More than one hundred and seventy compounds were identified by GC-MS in the fractions. Levels of PAHs and the distribution profile was similar at both sampling locations. Higher concentrations of PAHs, nitro-PAHs, polycyclic aromatic ketones and organic acids and bases were observed in winter period when the fuel consumption for home heating is high.