Teflon Membrane Filters Research Articles

Validation of diffusive mini-samplers for aldehyde and VOC and its feasibility for measuring the exposure levels of elementary school children

Exposure to various chemicals can cause adverse effects to health, such as asthma and allergies, especially in children. Data on personal exposure levels in children are scarce, thus small lightweight diffusive mini-samplers for aldehydes and volatile organic compounds (VOCs) were designed to measure the exposure level of children to these chemicals. The aim of the study was to validate and examine the applicability of these mini-samplers for measuring daily chemical exposure. The diffusive mini-samplers are 20 mm in length, 11 mm in diameter, and 1.67 g in weight. The devices are cylindrically shaped with polytetrafluoroethylene membrane filters placed at each end. To measure aldehydes and acetone, 20 mg of 2,4-dinitrophenylhydrazine was used as an absorbent. To measure VOCs, a carbon molecular sieve was used. The sampling rate for each chemical was determined by parallel sampling with active samplers in a closed exposure bag. The blank levels of the chemicals and the storage stability of the device were tested. The mini-samplers were compared to commercially available diffusive samplers. To examine the applicability of the samplers, 65 elementary school children carried them for 24 h. The sampling rates for formaldehyde, acetaldehyde, and acetone were 20.9, 22.9, and 19.7 mL min(-1), respectively. The limits of quantification (LOQ) for the 24-hour sampling by high-performance liquid chromatography/ultraviolet (HPLC/UV) analysis were 8.3, 7.6, and 8.8 μg m(-3) for formaldehyde, acetaldehyde, and acetone, respectively. The sampling rates for the 11 VOCs were determined and ranged from 3.3 mL min(-1) for styrene and 2-ethyl-1-hexanol to 11.7 mL min(-1) for benzene. The LOQ for the 24-hour sampling by gas chromatography-mass spectrometry (GC-MS) analysis ranged from 5.9-105.2 μg m(-3), 1.1-24.7 parts per billion. The storage stability after 5 days ranged from 94.8 to 118.2%. Formaldehyde, acetone, benzene, and toluene were detected above the LOQ in more than 90% of the children, and the median concentrations were 21.7, 20.9, 10.1, and 21.5 μg m(-3), respectively. This study shows that the diffusive samplers developed were suitable for children to carry and were capable of measuring the children's daily chemical exposure.

Phenolic compounds from Potentilla alba

HPLC was used to determine the phenolic compounds. Portions (500 mg) of ground samples of air-dried raw material were weighed in 5-mL volumetric tubes. The volume was adjusted to the mark with MeOH (90%). The samples were irradiated for 30 min in an ultrasonic bath, left at room temperature for 3–4 h, placed for 15 min in the ultrasonic bath, and filtered through a teflon membrane filter (0.45 m) into vials for analysis (Table 1). Phenolic compounds were identified by retention times of standards and spectral properties of the studied extracts. Chromatography was performed on an Agilent Technologies Model 1100 chromatograph equipped with a G1379A flow-vacuum degasser, a G13111A four-channel lowpressure gradient pump, a G1313A automated injector, a G13116A column thermostat, and a G1316A diode-matrix detector. The Zorbax-SB C-18 chromatographic column (2.1 150 mm) was packed with octadecylsilyl sorbent (3.5 m). Phenolic compounds in MeOH extracts were identified by retention times of standard rutin, quercetin-3-O-glucoside, and p-coumaric acid (Sigma) and by comparison of spectral properties of the test compounds in the extracts with those of standards. The aerial part contained quercetin-3-O--D-glucopyranosyl-O--D-rhamnopyranoside, quercetin-3-O--Dglucopyranosido-7-O--D-glucopyranoside, kaempferol-3-O--D-glucopyranoside, quercetin-3-O--L-arabinoside, and kaempferol-3-O--L-arabinoside. Total flavonoids from the aerial part were dominated by quercetin-3,7-O-diglucoside (1.03%). The subterranean part of P. alba afforded p-coumaric acid (0.11%). Quercetin-3,7-O-diglucoside, kaempferol-3-O-glucoside, quercetin-3-O-arabinoside, and kaempferol-3-O-arabinoside were not previously reported from P. alba.

Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

Abstract. Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May–June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevations in the middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14–340 nm), and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC) and water-soluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening), during the transitional periods of boundary layer growth and collapse. The increase in number concentration during the peak periods was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shallow concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope) mountain winds that force the low level warmer air in the valley to rise. The mountain valley wind mechanisms induced by the topography along with the valley geometry appear to have a strong control in the diurnal cycle of the aerosol size distribution. During the sampling period, the chemical composition of PM2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64–68%) of the aerosol concentration followed by ionic species (24–26%, mainly SO42− and NH4+). Elemental Carbon (EC) compromised 7–10% of the total composition and 27% of OC was found to be water soluble at both sites. The day-to-day variability observed in the time series of aerosol composition could be explained by the synoptic scale haze that extended to the sampling region from the Indian Gangetic Plain (IGP), and rainfall occurrence. In the presence of regional scale haze during dry periods, the mean volume aerosol concentration was found to increase and so did the aerosol mass concentrations.

Filter Light Attenuation as a Surrogate for Elemental Carbon

Light attenuation (b att) measured from filter light transmission is compared with elemental carbon (EC) measurements for more than 180,000 collocated PM2.5 (particulate matter [PM] ≤ 2.5 µm in aerodynamic diameter) and PM10 (PM ≤ 10 µm in aerodynamic diameter) samples from nearly 200 U.S. locations during the past 2 decades. Although there are theoretical reasons for expecting highly variable relationships between batt and EC (such as the effects of “brown carbon” and iron oxides in PM2.5), reasonable correlations are found. These correlations are not a strong function of season or location (e.g., rural vs. urban). Median EC concentrations can be predicted from filter transmittance measurements to within ±15–30%. Although EC predicted from batt shows larger uncertainties (30–60%), especially at concentrations less than 0.3 µg/m3, the consistent mass absorption efficiency (σatt) derived from the regression analysis demonstrates the feasibility of using b att as a surrogate for EC. This study demonstrates that a constant factor of 0.1 g/m2 (equivalent to the 10 m2/g σatt used in the Interagency Monitoring of Protected Visual Environments chemical extinction formula) can be used to estimate EC concentrations from batt through a Teflon-membrane filter sample. Greater accuracy is achieved with site-specific σatt derived from a period with collocated EC measurements.

Diversity of airborne bacteria in samples collected using different devices for aerosol collection

Bacteria are ubiquitous in the atmosphere, where they form a highly diverse community, albeit low in abundance. Several approaches are available for collecting airborne particles, though few comparative studies have been conducted to date. This study examined how different sampling strategies affect the apparent composition of the airborne community. Three devices were tested: an impactor, a liquid impinger, and a Teflon membrane filter. Comparative studies were conducted at one mountainous location in Norway and one seaside location in Sweden. At both locations, microbial samples were collected in parallel using the sampling devices. DNA extraction, construction of 16S rRNA gene clone libraries, and subsequent sequencing were used to identify the bacteria. The comparison between clone libraries retrieved using the different devices indicated good agreement regarding dominant species, overall diversity, and distribution of species among phylogenetic groups. Among the less common species, there were few shared sequences in different clone libraries, likely due to the high diversity of the assessed samples. Bacteria belonging to the Bacteroidetes and Proteobacteria phyla dominated at both locations, and the most common genera were Sphingomonas sp. and Pantoea sp. Chloroplast-like 16S rRNA gene sequences were detected in all samples.

PMF 모델을 이용한 수도권 내 3개 도시에서의 PM10오염원의 기여도 추정

The Korean government strengthened the environmental polices to manage and enhance Metropolitan Area air quality, and also has enforced "Special Act on Seoul Metropolitan Air Quality Improvement (SASMAQI)" issued in Dec. 2004. Recently government expanded the Seoul Metropolitan Air Quality Management District (SMAQMD) to the outskirts satellite cities of Seoul area through the "Revised Law Draft of SASMAQI". The SMAQMD has been alloted the allowable emission loads to the local governments on the basis of the carrying <TEX>$PM_{10}$</TEX> capacity. However, in order to establish the effective air quality control strategy for <TEX>$PM_{10}$</TEX>, it is necessary to understand the corresponding sources which have a potential to directly impact ambient <TEX>$PM_{10}$</TEX> concentration. To deal with the situations, many receptor methodologies have been developed to identify the origins of pollutants and to determine the contributions of sources of interests. The objective of this study was to extensively identify <TEX>$PM_{10}$</TEX> sources and to estimate their contributions at the metropolitan area. <TEX>$PM_{10}$</TEX> samples were simultaneously collected at the 3 semi-industrialized local cities in the Seoul metropolitan area such as Hwasung-si, Paju-si, and Icheon-si sites from April 15 to May 31, 2007. The samples collected on the teflon membrane filter by one <TEX>$PM_{10}$</TEX> cyclone sampler were analyzed for trace metals and soluble ions and samples on the quartz fiber filter by another sampler were analyzed for OC and EC. Source apportionment study was then performed by using a positive matrix factorization (PMF) receptor model. A total of 6 sources were identified and their contributions were estimated in each monitoring site. Contribution results on Hwasung, Paju, and Icheon sites were as follows: 33%, 27%, and 27% from soil source, 26%, 26%, and 21% from secondary aerosol source, 11%, 11%, and 12% from biomass burning, 12%, 6%, and 5% from sea salt, 7%, 15%, and 19% from industrial related source, and finally 11%, 15%, and 16% from mobile and oil complex source, respectively. This study provides information on the major sources affecting air quality in the receptor sites and thus it will help to manage the ambient air quality in the metropolitan area by establishing reasonable control strategies, especially for the anthropogenic emission sources.

Methods to Assess Carbonaceous Aerosol Sampling Artifacts for IMPROVE and Other Long-Term Networks

Volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) adsorb to quartz fiber filters during fine and coarse particulate matter (PM2.5 and PM10, respectively) sampling for thermal/optical carbon analysis that measures organic carbon (OC) and elemental carbon (EC). Particulate SVOCs can evaporate after collection, with a small portion adsorbed within the filter. Adsorbed organic gases are measured as particulate OC, so passive field blanks, backup filters, prefilter organic denuders, and regression methods have been applied to compensate for positive OC artifacts in several long-term chemical speciation networks. Average backup filter OC levels from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network were approximately 19% higher than field blank values. This difference is within the standard deviation of the average and likely results from low SVOC concentrations in the rural to remote environments of most IMPROVE sites. Backup filters from an urban (Fort Meade, MD) site showed twice the OC levels of field blanks. Sectioning backup filters from top to bottom showed nonuniform OC densities within the filter, contrary to the assumption that VOCs and SVOCs on a backup filter equal those on the front filter. This nonuniformity may be partially explained by evaporation and readsorption of vapors in different parts of the front and backup quartz fiber filter owing to temperature, relative humidity, and ambient concentration changes throughout a 24-hr sample duration. OC-PM2.5 regression analysis and organic denuder approaches demonstrate negative sampling artifact from both Teflon membrane and quartz fiber filters.

Carbon-isotopic analysis of microbial cells sorted by flow cytometry.

One of the outstanding current problems in both geobiology and environmental microbiology is the quantitative analysis of in situ microbial metabolic activities. Techniques capable of such analysis would have wide application, from quantifying natural rates of biogeochemical cycling to identifying the metabolic activity of uncultured organisms. We describe here a method that represents one step towards that goal, namely the high-precision measurement of 13 C in specific populations of microbial cells that are purified by fluorescence-activated cell sorting (FACS). Sorted cells are concentrated on a Teflon membrane filter, and their 13 C content is measured by coupling an isotope ratio mass spectrometer (IRMS) with a home-built spooling wire microcombustion (SWiM) apparatus. The combined instrumentation provides measurements of δ13 C in whole cells with precision better than 0.2‰ for samples containing as little as 25ng of carbon. When losses associated with sample handling are taken into account, isotopic analyses require sorting roughly 104 eukaryotic or 107 bacterial cells per sample. Coupled with 13 C-labelled substrate additions, this approach has the potential to directly quantify uptake of metabolites in specific populations of sorted cells. The high precision afforded by SWiM-IRMS also permits useful studies of natural abundance variations in 13 C. The approach is equally applicable to specific populations of cells sorted from multicellular organisms.

Retained Nitrate, Hydrated Sulfates, and Carbonaceous Mass in Federal Reference Method Fine Particulate Matter for Six Eastern U.S. Cities

Material balance of fine particulate matter (PM2.5) measured with the Federal Reference Method (FRM) is developed for one rural and five urban locations in the eastern half of the United States using routine Speciation Trends Network (STN) and FRM chemical measurements and thermodynamic models. The Aerosol Inorganics Model is used to estimate retained particle bound water, and an ammonium nitrate evaporation model is used to estimate nitrate concentrations retained on the Teflon-membrane filter of the FRM. To address large uncertainties in carbonaceous mass calculated from STN carbon measurements, retained carbonaceous mass is derived by material balance between PM2.5 FRM mass and estimates of its non-carbon constituents. The resulting sulfate, adjusted nitrate, derived water, inferred carbonaceous material balance approach (SANDWICH) is compared with reconstructed fine mass (RCFM) using the Interagency Monitoring of Protected Visual Environments monitoring program equation. For this study, the SANDWICH method resulted in ∼21–27% higher sulfate mass and ∼24–85% lower nitrate mass. The combined mass associated with sulfates and nitrates, however, are well within ±10% of the proportion derived using the more traditional RCFM method. The discrepancies between SANDWICH and measurement-derived carbonaceous mass vary from −21% to +56% on an annual basis and are attributed in part to urban–rural source influences and uncertainties in estimating FRM-retained carbonaceous mass.

Development and evaluation of personal respirable particulate sampler (PRPS)

This paper presents the development, laboratory evaluation, and field tests of a personal respirable particulate sampler (PRPS). The PRPS is designed as a personal sampling system to collect particulate matter (PM 0.5, PM 1.0, PM 2.5, PM 4.5, and PM 10) and gaseous pollutants, including O 3, SO 2, and NO 2. It operates at a flow rate of 5.0 LPM and consists of five selectable impaction stages (with cutpoints of 10, 4.5, 2.5, 1.0, and 0.5 μm), a backup filter, and two diffusion passive samplers. In each impaction stage, particles are collected onto a polyurethane foam (PUF) substrate. This substrate, using no adhesive, was shown to have minimum particle bounce and re-entrainment. A backup 37 mm Teflon membrane filter is used downstream to collect particles smaller than the cutoff diameter of the final impaction stage. The impaction stage cutpoints were characterized in the laboratory using artificially generated polydisperse aerosols. Particle losses for each stage were found to be acceptably low. The performance of the PRPS was also compared with that of a collocated micro-orifice cascade impactor (MOI) and real-time particle sizing instruments (SMPS/APS) in laboratory experiments using artificially generated particles. The size distributions measured by the PRPS were found to be much closer to those measured by the real-time particle sizing instruments than to those measured by the MOI. A field PM intercomparison study was also conducted using the PRPS and three reference samplers, the Harvard Impactor (HI), the USEPA PM 2.5 Well Impactor Ninety Six (WINS), and the Harvard Personal Environmental Monitor (Harvard PEM) sampler. The PM 10, PM 2.5, and sulfate concentrations measured by PRPS were in a very good agreement with those obtained from the reference samplers.

Results from a pilot-scale air quality study in Addis Ababa, Ethiopia

Twenty-one samples were collected during the dry season (26 January–28 February 2004) at 12 sites in and around Addis Ababa, Ethiopia and analyzed for particulate matter with aerodynamic diameter <10 μm (PM 10) mass and composition. Teflon-membrane filters were analyzed for PM 10 mass and concentrations of 40 elements. Quartz-fiber filters were analyzed for chloride, sulfate, nitrate, and ammonium ions as well as elemental carbon (EC) and organic carbon (OC) content. Measured 24-h PM 10 mass concentrations were <100 and 40 μg m −3 at urban and suburban sites, respectively. PM 10 lead concentrations were <0.1 μg m −3 for all samples collected, an important finding because the government of Ethiopia had stopped the distribution of leaded gasoline a few months prior to this study. Mass concentrations reconstructed from chemical composition indicated that 34–66% of the PM 10 mass was due to geologically derived material, probably owing to the widespread presence of unpaved roads and road shoulders. At urban sites, EC and OC compounds contributed between 31% and 60% of the measured PM 10 while at suburban sites carbon compounds contributed between 24% and 26%. Secondary sulfate aerosols were responsible for <10% of the reconstructed mass in urban areas but as much as 15% in suburban sites, where PM 10 mass concentrations were lower. Non-volatile particulate nitrate, a lower limit for atmospheric nitrate, constituted <5% and 7% of PM 10 at the urban and suburban sites, respectively. At seven of the 12 sites, real-time PM 10 mass, real-time carbon monoxide (CO), and instantaneous ozone (O 3) concentrations were measured with portable nephelometers, electrochemical analyzers, and indicator test sticks, respectively. Both PM 10 and CO concentrations exhibited daily maxima around 7:00 and secondary peaks in the late afternoon and evening, suggesting that those pollutants were emitted during periods associated with motor-vehicle traffic, food preparation, and heating of homes. The morning concentration maxima were likely accentuated by stable atmospheric conditions associated with overnight surface temperature inversions. Ozone concentrations were measured near mid-day on filter sample collection days and were in all cases <45 parts per billion.

Loss of PM2.5 Nitrate from Filter Samples in Central California

Evaporative loss of particulate matter (with aerodynamic diameter <2.5 μm, [PM2.5]) ammonium nitrate from quartz-fiber filters during aerosol sampling was evaluated from December 3, 1999, through February 3, 2001, at two urban (Fresno and Bakersfield) and three nonurban (Bethel Island, Sierra Nevada Foothills, and Angiola) sites in central California. Compared with total particulate nitrate, evaporative nitrate losses ranged from <10% during cold months to >80% during warm months. In agreement with theory, evaporative loss from quartz-fiber filters in nitric acid denuded samplers is controlled by the ambient nitric acid-to-particulate nitrate ratio, which is determined mainly by ambient temperature. Accurate estimation of nitrate volatilization requires a detailed thermodynamic model and comprehensive chemical measurements. For the 14-month average of PM2.5 acquired on Teflon-membrane filters, measured PM2.5 mass was 8–16% lower than actual PM2.5 mass owing to nitrate volatilization. For 24-hr samples, measured PM2.5 was as much as 32–44% lower than actual PM2.5 at three California Central Valley locations.

Performance evaluation of commonly used impaction substrates under various loading conditions

This paper presents the results from the systematic performance evaluation tests of commonly used impaction substrates including uncoated metal plate, teflon membrane filter, greased metal plate, oiled sintered porous metal, and polyurethane foam (PUF), at various loading conditions. A single stage impactor and artificially generated aerosol composed of polydisperse glass beads were used to test the substrates. Significant particle bounce was observed for both the uncoated metal plate and Teflon filter substrate for particles larger than the impactor cutpoints ( d 50 ) at very low loading conditions. Particle bounce decreased with increasing particle loading until it reaches a plateau at a loaded mass of approximately 3 mg. A shift of collection efficiency curve was also observed, including a decrease of d 50 for both the uncoated metal and the teflon filter. Despite the fact that the collection efficiency for particles larger than d 50 remained high (95%) and constant up to about 30 mg of collected mass on the greased and the oiled sintered metal, an indication for minimum particle bounce and re-entrainment, a decrease of the d 50 was also observed. However, while the changes in collection efficiency curve with increased loading and the consequent decreases of d 50 were significant for the greased and oiled sintered metal substrate, for the PUF substrate, neither substantial particle-bounce nor significant changes in collection efficiency were observed. For PUF, the collection efficiency remained high (98%) for particles larger than the d 50 for upto 30 mg of collected mass. The changes of the d 50 on PUF are considerably less than those for the flat and rigid substrates. These results comprise a comprehensive confirmation that the nature of the impaction substrate has a significant effect on the particle bounce and particle separation performance of conventional inertial impactors.

Herbicide Sorption to Fine Particulate Matter Suspended Downwind of Agricultural Operations: Field and Laboratory Investigations

Tillage-induced erosion of herbicides bound to airborne soil particles has not been quantified as a mechanism for offsite herbicide transport. This study quantifies the release of two preemergent herbicides, metolachlor and pendimethalin, to the atmosphere as gas- and particle-phase species during soil incorporation operations. Fine particulate matter (PM2.5) and gas-phase samples were collected at three sampling heights during herbicide disking into the soil in Davis, CA, in May 2000 and May 2001 using filter/PUF sampling. Quartz fiber filters (QFFs) were used in May 2000, and Teflon membrane filters (TMFs) were used in May 2001. The field data were combined with laboratory filter/PUF partitioning experiments to account for adsorption to the filter surfaces and quantify the mass of PM2.5-bound herbicides in the field samples. Laboratory results indicate a significant adsorption of metolachlor, but not pendimethalin, to the quartz filter surfaces. Metolachlor partitioning to PM2.5 collected on TMF filters resulted in corrected PM2.5 field partition coefficient values, Kp,corr = Cp/Cg, of approximately 10(-3.5) m3/microg, indicating its preference for the gas phase. Pendimethalin exhibited more semivolatile behavior,with Kp,corr values that ranged from 10(-3) to 10(-1) m3/ microg and increased with sampling height and distance downwind of the operation. An increase in pendimethalin enrichment at a height of 5 m suggests winnowing of finer, more sorptive soil components with corresponding higher transport potential. Pendimethalin was enriched in the PM2.5 samples by up to a factor of 250 compared to the field soil, indicating thatfurther research on the processes controlling the generation of PM-bound herbicides during agricultural operations is warranted to enable prediction of off-site mass fluxes by this mechanism.

The Pertraction of Hydrophobic Organic Solutes across a Hydrophobic Membrane

Abstract The pertraction of hydrophobic organic solutes across a hydrophobic membrane is a continuous separation process, which can be used as a substitute to active carbon. The permeabilities of hydrophobic organic solutes were examined in a two compartment cell partitioned by a hydrophobic membrane. The permeability was dominated by the hydrophobicity of the solute and the dissociation in the receiving phase. The permeability of the hydrophobic solutes increased with increasing pH of the receiving phase solution for the Teflon membrane filter Fluoropore. The preferential permeability of a hydrophobic solute was obtained, and the pertraction of a hydrophobic solute against its concentration gradient was also possible under a concentration gradient of hydroxide ion. Solute permeability changes were observed by coating the surface of Fluoropore to cover its pores with tetrafluoroethene–hexafluoropropene copolymer, FEP, and a highly selective permeability was obtained between phenol and 2-isopropyl-5-methylphenol (thymol) by suppressing the phenol permeability by coating the FEP membrane.

Elemental composition of springtime aerosol in Chillán, Chile

An aerosol monitoring study was established to measure ambient aerosol composition and study air pollution for one sampling site located at the University of Concepción, Chillán Campus. Chillán, a typical agricultural city in the central valley, is located in the southern Bio Bío Region of Chile. The Chillán Campus is located approximately 4 km north of the city's downtown. The aerosol monitor operated on the campus from 9 October to 9 December, 1998. The study employed an IMPROVE sampler with an Anderson PM10 inlet at 3 m collecting PM10 on 25 mm Teflon membrane filters. The filters were weighed before and after sampling to obtain mass concentration, then proton induced X-ray emission and X-ray fluorescence analysis were used to measure the concentration of 22 elements to levels below 0.68ng/m3. Moderate aerosol concentration was observed (up to 116μg/m3). The main aerosol particle source in Chillán is resuspended soil dust, which accounts for 55% of the PM10 aerosol. The presence of Br, Pb and V and other heavy metals in analyzed samples points to traffic emissions in the city. Aerosol associated with transportation activities accounts for 11% of the PM10 mass. Non-transportation organics, associated with hydrogen measured by proton elastic scattering analysis, are an important component accounting for 19% of the PM10 mass. Sulfate particles account for 3%. In addition, presence of several trace metals, including Mn, Zn, Cu, Ga, As, and Sr in our samples suggests the presence of industrial emissions in the city.

Performance of air filters cleaned by supercritical carbon dioxide

A new technique based on the use of supercritical carbon dioxide (CO 2) for cleaning HEPA filters was developed. Glass fiber filters and polytetrafluoroethylene (PTFE) membranes loaded with dioctylphthalate (DOP) droplets were cleaned with supercritical carbon dioxide under various conditions. The cleaning performance was evaluated by the weight recovery of the filter media and the recoveries of their collection efficiencies and pressure drops. The extent of DOP removal from glass fiber filters was nearly complete with supercritical carbon dioxide cleaning at 20 MPa and 40 °C for a period of 120 min and the collection efficiency and pressure drop were also recovered to those of new filters. Furthermore, thermo-gravimetric (TG) analysis showed that cleaning did not wash away any of the binder resins. However, less satisfactory results were obtained for PTFE membrane filters.

A LC/MS method for the determination of cyanobacteria toxins in water.

The cyanobacteria toxins anatoxin-a, microcystin-LR, microcystin-RR, microcystin-YR, and nodularin were separated in less than 30 min on several 1 mm x 15 cm reversed-phase liquid chromatography (LC) columns, and their electrospray mass spectra were measured using injections of 50 ng or less with a benchtop time-of-flight (TOF) mass spectrometer. New data from this work include the following: (a) the impact of acetic acid concentrations in the methanol-water mobile phase on measured ion abundances; (b) the performance of the electrospray-TOF mass spectrometer as an LC detector; (c) the accuracy and precision of exact m/z measurements after LC separation with a routinely used mass spectrometer resolving power of 5000; and (d) recoveries of the five toxins from reagent water, river waters, and sewage treatment plant effluent samples extracted with C-18 silica particles enmeshed in thin Teflon membrane filter disks. This technique has the potential of providing a relatively simple and reasonable-cost sample preparation and LC/MS method that provides the sensitivity, selectivity, reliability, and information content needed for source and drinking water occurrence and human exposure studies.

Determination of various types of labile atmospheric iron over remote oceans

Atmospheric deposition of iron (Fe) is a major source of the micronutrient to the remote ocean. Most studies have focused on the total atmospheric Fe fluxes to the oceans while fewer studies have focused on the chemistry and chemical speciation of atmospheric Fe. This speciation of Fe in the atmosphere is critical to understanding the fraction of Fe that will be labile in surface waters after deposition and consequently has implications for the bioavailability of this atmospherically derived Fe. In this study, 24‐hour aerosol samples were collected using a high‐volume dichotomous virtual impactor (HVDVI) that collected coarse (Dp &gt; 2.5 μm) and fine (Dp&lt; 2.5 μm) aerosol fractions on two 90‐mm Teflon membrane filters, over the tropical and subtropical North Atlantic Ocean. A sequential aqueous extraction procedure using a pH 4.5 buffer solution and a chemical reductant (hydroxylamine hydrochloride (HA)) was used to measure various labile Fe fractions. The extraction procedure was performed immediately after aerosol sample collection and used time series measurements of Fe(II) using long path length absorbance spectroscopy (LPAS) for analysis of Fe(II). The method measured both the quantities of labile Fe and also the dissolution and reduction kinetics of the labile Fe. Comparisons of HA‐reducible Fe and photoreducible Fe concentrations were conducted on board and showed that both reduction processes had similar reduction kinetics and final Fe(II) concentrations during the initial 90 min. The average pseudo‐first‐order rate constants for the increase in Fe(II) were 0.020 and 0.0076 min−1 for the photoreducible Fe extraction and HA‐reduction extraction, respectively. This HA‐reducible Fe amount could potentially be used to determine the maximum amount of labile atmospheric Fe that is deposited into the ocean.

A compact multistage (cascade) impactor for the characterization of atmospheric aerosols

This paper presents the development, laboratory characterization, and field evaluation of a compact multistage cascade impactor (CCI). The CCI operates at a flow rate of 30 LPM and consists of eight impaction stages equipped with rectangular slit-shaped acceleration nozzles. A 47 mm backup Teflon membrane filter is used downstream of the eighth stage to collect particles smaller than 0.16 μm . In each stage, particles are retained by impaction onto the inert polyurethane foam (PUF) substrate. The major feature of this novel sampler is its ability to both fractionate by size and collect relatively large amounts of particles (mg quantities) onto an inert polyurethane foam impaction substrates. Even though the impaction substrates are not coated with adhesives such as grease or mineral oil, particle bounce and re-entrainment losses were found to be insignificant. Impaction characteristics (cutpoint and sharpness of collection efficiency curve) of the PUF substrates are maintained for mass loadings of at least 25 mg , which is much higher than for other commonly used rigid, flat impaction substrates. The system was calibrated in laboratory experiments using polydisperse aerosols. The 50% cutpoints of the eight stages were 9.9, 5.3, 3.3, 2.5, 1.7, 1.0, 0.47 and 0.16 μm (aerodynamic diameter), with pressure drops of 0.02, 0.02, 0.04, 0.06, 0.08, 0.27, 1.57 and 5.73 kPa . These pressure drops are considerably lower than those obtained using flat rigid impaction substrates with comparable cutpoints. Particle losses for each stage were less than 10% for particles smaller than 7 μm and less than 20% for particles larger than 7 μm . The CCI was also compared with the collocated micro-orifice impactor (MOI) in laboratory-controlled experiments using artificially generated polydisperse aerosol. These laboratory tests showed that the mass concentrations measured by the MOI are considerably lower than those measured by the CCI (the average ratio of total mass concentration of MOI to CCI was 0.86), with the size distribution measured by the CCI closer to that measured using the real time particle sizing instruments (SMPS, APS). A field comparison of CCI, the Harvard impactor (HI) and the federal reference method (FRM) for fine particles showed a good agreement between the CCI and the reference samplers for particles smaller than 2.5 μm .