Annular Denuder System Research Articles

Artifacts of ionic species for hi-vol PM 10 and PM 10 dichotomous samplers

This study employs two Annular Denuder Systems (ADS 10 and ADS 2.5) to quantify sampling artifacts of soluble ionic species determined by the high-volume PM 10 (hi-vol PM 10) sampler using quartz fiber filters and PM 10 dichotomous (Dichot) sampler using Teflon filters. According to the experimental results, the percentage of artifact of a species over the actual species concentrationis +11, +8 and +15% for PM HV 10, PM DICH 10, PM DICH 2.5, respectively, for sulfate species; −16, −21 and −21% for PM HV 10, PM DICH 10, PM DICH 2.5, respectively, for nitrate species; −24, −32 and −54% for PM HV 10, PM DICH 10, PM DICH 2.5, respectively, for chloride ion species; −17, −21 and −18% for PM HV 10, PM DICH 10, PM DICH 2.5, respectively, for ammonium ion species. For volatile species such as nitrate, ammonium and chloride ions, additional sampling losses due to gas–particle and particle–particle interactions are more important than pure volatilization loss. Amount of positive and negative artifacts is approximately equal and the amount of net artifact does not account for more than 15% of PM 10 concentration.

Long term measurements of atmospheric gaseous and aerosol species using an annular denuder system in Nara, Japan

During the period from June 1994 to May 1995 a three-line annular denuder filter system was used to sample atmospheric gas phase SO 2, HNO 3, HNO 2, HCl, and NH 3 and aerosol phase SO 2- 4, NO - 3, Cl -, NH + 4, Na +, K +, Ca 2+, and Mg 2+ in Nara, Japan. The average annual concentrations of these species were determined together with their seasonal variations. It was found that even in a medium-sized city such as Nara HNO 3 and HNO 2 concentrations were fairly high. The present system also enabled the determination of the percent loss of aerosol components NO - 3, Cl - and NH + 4 collected on filters.

Analysis of ammonia and aerosol concentrations and deposition near the free troposphere at Mt. Mitchell, NC, U.S.A.

Measurements of airborne (gaseous and aerosol), cloud water, and precipitation concentrations of ammonia (NH 3) and ammonium (NH + 4) compounds were made at Mt. Mitchell State Park (Mt. Gibbs, ∼2006 m MSL), North Carolina. Measurements were made from May to September during 1988 and 1989. An annular denuder system was used to determine gaseous NH 3 and particulate NH + 4 and nitrate (NO - 3) compounds. Measurements of NH + 4 in cloud and rain water samples were made during the same time period. Mean concentrations of gaseous NH 3 were 0.62 μg m -3 for 1988 and 1.47 μg m -3 for 1989. Mean concentrations of fine particulate NH + 4 were 1.24 μg m -3 for 1988 and 0.89 μg m -3 for 1989. The NH + 4 concentrations in the cloud water were 214 and 147 μeq ℓ -1 for the 1988 and 1989 field seasons, respectively. The concentrations of NH + 4 in precipitation were quite low compared to cloud ionic values in both 1988 and 1989 at 14 and 15 μeq ℓ -1, respectively. The estimated mean total deposition of NH + 4 over the sampling period (5 months) of 1988 and 1989 was about 0.38 and 0.67 g N m -2 season -1, respectively. Cloud water interception contributed more nitrogen (∼70%) to the total deposition than combined wet (∼15%) and dry (∼15%) deposition.

Field Comparison of Methods for Evaluation of Vapor/Particle Phase Distribution of Ammonia in Livestock Buildings

Ammonia is a significant respiratory hazard for workers in enclosed livestockbuildings. It is hypothesized that ammonia originating from animal wastes is present inboth vapor phase and adsorbed onto dust (particulate phase), and that this physicaldistribution is an important determinant of deposition in the human respiratorysystem. The goals of this project were: (1) to evaluate the vapor/particle phasedistribution of ammonia in enclosed livestock buildings using annular denuders andimpingers with prefilters; and (2) to compare the annular denuders air samplingmethod to traditional active and passive ammonia sampling methods. Ammonia wassampled and analyzed using six methods: annular denuder systems with ionchromatographic (IC) analysis; impingers with pre-filter and IC analysis; impingerswithout pre-filters with IC analysis; long-term colorimetric tubes; direct readingcolorimetric detector tubes; and passive dosimeters. Field studies were conducted in sixenclosed swine and poultry buildings during the summer season. Analysis of varianceconfirmed by individual t-tests indicated that passive dosimeters and long-termcolorimetric tubes consistently yielded higher ammonia values than the denuder andimpinger methods. Denuder systems were less precise (pooled CV = 0.41) thanimpingers without pre-filters (pooled CV = 0.16), but more precise than impingerswith pre-filters (pooled CV = 0.47). The results of this study indicate that a measurableproportion of ammonia in enclosed livestock buildings is indeed associated withparticles, and that annular denuder systems have potential to be used in thisenvironment for evaluation of phase distributions of ammonia. However, the precisionand overall collection efficiency of the specific annular denuder evaluated was poorcompared to the traditional impinger method, and further work is needed to develop amore suitable denuder system for the relatively higher concentrations of gases andparticulates encountered in agricultural environments.

Analysis of ammonia, ammonium aerosols and acid gases in the atmosphere at a commercial hog farm in eastern North Carolina, USA

Measurements of atmospheric ammonia, acid gases, and ammonium aerosols were made at a commercial hog farm in Eastern North Carolina, USA, during September through December of 1997. Annular denuder systems (ADS) were used to sample gaseous (hydrogen chloride, nitrous acid, nitric acid, sulfur dioxide and ammonia) and fine aerosol (ammonium, chloride, nitrate, and sulfate) species. Ammonia and ammonium concentrations were determined by colorimetric analysis of the sample extracts. The acid gases and remaining fine particle ionic species were determined by ion chromatographic analysis of the sample extracts. Mean concentrations of the gaseous hydrogen chloride, nitrous acid, nitric acid, sulfur dioxide and ammonia were 0.743 μg/m 3, 0.255 μg/m 3, 0.154 μg/m 3, 2.968 μg/m 3, and 10.48 μg/m 3, respectively. Mean concentrations of the fine particle chloride, nitrate, sulfate and ammonium were 0.321 μg/m 3, 0.548 μg/m 3, 3.247 μg/m 3, and 1.102 μg/m 3, respectively. The fine aerosol fraction was dominated by ammonium sulfate particles. A linear regression of sulfate versus ammonium by equivalent concentration showed a slope of 0.715 and r 2 of 0.88. An emission factor for total ammonia nitrogen flux was estimated using a simple box model as approximately 5 to 10 kg animal −1 year −1.

Inertial collection of fine particles using a high-volume rectangular geometry conventional impactor

This paper presents the development and evaluation of a high-volume rectangular geometry conventional impactor. Operating with a preselective inlet that removes particles larger than 2.5 μm in aerodynamic size, the impactor has been designed to sample ambient fine particles in the accumulation mode range (0.1 < d p < 2.5 μm). Particles are accelerated in a rectangular nozzle, 0.032 cm wide and 28 cm long, and impact on a filter medium attached on a porous glass frit, which is soaked in mineral oil. The impactor operates at a flow rate of 1000 l min −1 with a total pressure drop of 30 kPa. The performance of the slit-nozzle impactor was validated in laboratory and field tests. Laboratory experiments conducted with monodisperse fluorescent PSL particles showed that the aerodynamic diameter of the 50% cutpoint of the impactor is approximately 0.09 μm. Laboratory and field intercomparisons between the high-volume slit impactor and the microrifice uniform deposit impactor (MOUDI) showed that particulate nitrate and sulfate concentrations obtained with the two samples are in good agreement (within 10%). Finally, a comparison between the particulate nitrate concentrations obtained with high-volume impactor and the Harvard/EPA annular denuder system (HEADS) was conducted, using indoor air as the test aerosol. Results from this comparison indicated that losses of nitrate from the impactor are not substantial and range between 5 and 15%. Results from the laboratory and field tests suggest that the high-volume impactor presented in this study constitutes a major improvement in the field of high-volume fine particle sampling.

Relationships between indoor and outdoor air quality during the summer season in Korea

The annular denuder system (ADS) was used to determine quantitatively the relationship between indoor and outdoor air. All indoor and outdoor measurements were done simultaneously using the ADS in Chongju, Korea during the summer season. The data set was collected on eight different days with a 24 h sampling period from 27 July 1995 to 27 August 1995. The chemical species measured were HNO 3, HNO 2, SO 2 and NH 3 in the gas phase and PM 2.5(d p < 2.5 μm), SO 2− 4 N0 − 3 and NH + 4 in the particulate phase. For these data, outdoor air contributed from 50 to 100% of indoor pollution environment during the summer season in Korea. Indoor concentrations for HN0 3, SO 2, PM 2.5, S0 2− 4 and NH + 4 were significantly related to the corresponding outdoor concentrations. These data are the first reported in Korea collected with the ADS.

Laboratory and field evaluation of an improved glass honeycomb denuder/filter pack sampler

A new and improved glass honeycomb denuder/filter pack sampler has been designed to measure atmospheric particles and gases. The new sampler combines the features of a previously developed glass honeycomb denuder sampler with a new inlet that minimizes loss of sampled gases on the inlet surfaces. Another novelty of the improved design is that the honeycomb denuders are entirely made of glass, instead of consisting of a large number of tubes sealed in an outer glass tube with epoxy resin. The new inlet was designed to reduce the residence time of the air sample as well as the overall surface area available for gas reaction. Although inlets of various materials were tested, the PTFE Teflon coated inlet was found to minimize loss of sampled gases. The honeycomb sampler with the improved inlet was characterized in two different field studies. Outdoor concentrations of nitric acid (HNO 3), nitrous acid (HONO), ammonia (NH 3), sulfur dioxide (SO 2), and fine-particle sulfate (SO 4 2−), ammonium (NH 4 +), strong acidity (H +) and fine particulate mass determined using the honeycomb denuder sampler (HDS) were compared to those determined with a collocated Harvard/EPA annular denuder system (HEADS). The average collection of the HEADS sampler was in excellent agreement (e.g. within ± 10% or less) with that of the honeycomb sampler for all the gas and particle phase species in the comparison studies. Results from the laboratory and field tests suggest that the new honeycomb denuder sampler with the improved inlet is suitable for sampling atmospheric particles and gases. In addition, it has the advantage of being more compact than annular denuder/filter pack systems, which makes the sampler more practical for large-scale monitoring studies.

A model for predicting performance of an annular denuder system

A mathematical model for simultaneous gas diffusion, aerosol diffusion and evaporation is presented to predict performance of the annular denuder system. Approximating the aerosol size distribution by a lognormal function and using the statistical method of moment, the evolution of the three aerosol moments and the mass balance equations for the two associated gases in the annular denuder system are obtained. The governing equations were cast into dimensionless form and the performance of the model was validated by the existing data available in the literature. The effects of governing dimensionless groups on the model performance were evaluated in the sensitivity analysis. The model was then applied for sampling nitric acid gas using a typical range of atmospheric aerosol and gas properties to derive the performance equation of the annular denuder system. The methodologies presented herein are helpful in providing design and operational criteria of the annular denuder system for a real sampling of atmospheric reactive gases that minimizes measurement artifacts.

95/05442 Atmospheric aerosol sampling by an Annular Denuder System and a high-volume PM 10 sampler

The Early Silurian (Llandoverian) Tuscarora Formation in central Pennsylvania contains shale beds with an abundant and predominantly land-derived palynoflora. Population studies of the assemblages of spore-like bodies (monads, dyads, and tetrads), leiospheres, nonacanthomorphic acritarchs, and miscellaneous organic structures from a section near Mill Hall provide data for biological, stratigraphic, and paleoecological investigations. Three new genera and eight new palynomorph species are described: Comasphaeridium hirsutum (n. sp); Leiosphaeridia acerscabrella (n. sp.); L. exasperata (n. sp.); Dyadospora membranifera (n. sp.); Pseudodyadospora laevigata (n. gen. et n. sp.); P. rugosa (n. sp.); Stegambiquadrella contenta (n. gen. et n. sp.); and Tortotubus protuberans (n. gen. et n. sp.). Experiments show that palynomorph size and morphology are significantly affected by oxidation, and that outer membranes are durable. The simple membrane coverings of the Silurian monads, dyads, and tetrads are distinguished from fern peri-spores and from the outer exines of cavate spores. A literature search on the occurrence of sporopollenin in extant and fossil algae is presented to demonstrate the possibility that some spore-like bodies could be algal in origin.

Effects of charcoal air filtration and ozone generation on concentrations of some N and S compounds in open-top field chambers

Concentrations of nitric acid (HNO 3), nitrous acid (HNO 2), ammonia (NHA sulfur dioxide (SO 2), as well as particulate nitrate (NOD, sulfate (SO 4 2−), and ammonium (NH 4 +) were determined with annular denuder systems in open-top chambers (charcoal-filtered [CF] ; ambient air [AA] ; and ambient air with ozone [O 3] added [2 × O 3]) and the outside chamberless plot. Concentrations of HNO 3 were the highest in the outside plot, followed by the 2 × O 3, AA, and the CF chambers. Substantial increases of HNO 2 were noticed in the CF chambers compared with other chambers and the outside plot. No changes in concentrations of NH 3 were recorded for the studied filtration regimes. As expected, concentrations of SO 2 were drastically reduced for the CF treatment. No clear effects of air filtration on concentrations of the particulate pollutants were determined. Possible consequences of the observed chemical changes of the open-top chambers' environment on plants are discussed.

Spatial Variation in Acidic Sulfate and Ammonia Concentrations within Metropolitan Philadelphia

Abstract Acidic sulfate concentrations were measured in metropolitan Philadelphia during the summers of 1992 and 1993, as part of a continuing effort to characterize particle concentrations in urban environments. Sampling was performed simultaneously at eight sites located within and around metropolitan Philadelphia. Sites were selected based on their population density and on their distance and direction from the city center. Air pollution sampling was conducted every other day during the summer of 1992 and every day during the summer of 1993. All samples were collected for 24-h periods beginning at 9 a.m. (EDT). All acidic sulfate and ammonia samples were collected using modified Harvard-EPA Annular Denuder Systems (HEADS). In this paper, we examine the spatial variation in acidic sulfate and ammonia concentrations within the metropolitan Philadelphia area. We also identify factors that may influence their variation and develop models to predict their concentrations. Outdoor sulfate (SO4 2−) concentrations were uniform within metropolitan Philadelphia; however, aerosol strong acidity (H+) concentrations varied spatially. This variation generally was independent of wind direction, but was related to local factors, such as the NH3 concentration, population density, and distance from the center of the city. Physico-chemical models, which were developed using data collected during the summer of 1992, were excellent predictors of 24-h and mean summertime H+ concentrations measured during the summer of 1993. Models accounted for 78% of the variation in 24-h H+ levels. Results suggest that a single stationary ambient (SAM) monitor would be sufficient to estimate SO4 2− exposures for populations living in Philadelphia. For H+, however, multiple monitoring sites or models should be used to determine the outdoor H+ exposures of populations living in urban environments, although a single SAM site may provide an excellent index of H+ variation over time.

Atmospheric aerosol sampling by an annular denuder system and a high-volume PM 10 sampler

An Annular Denuder System (ADS) was used to study sampling errors of total PM 10 and soluble ionic species concentrations determined by the high volume PM 10 (HVPM 10) sampler. Experimental results show that in the HVPM 10 sampler, more alkaline glass fiber filters collect more sulfate and nitrate but less ammonium ion than quartz filters. However, total PM 10 concentrations do not seem to depend on the types of filters. Artifact sulfate concentrations in glass fiber filters of the HVPM 10 sampler are found to exceed those predicted by the Coutant's model. It is suggested that artifact sulfate and nitrate not only occur within filters but also in particle deposits. Chloride ion concentrations in the filters of the HVPM 10 sampler are underestimated significantly due to evaporative loss of ammonium chloride.

Field method comparison for the characterization of acid aerosols and gases

Abstract This paper presents findings from two intercomparison studies of acid aerosol measurement systems, which were conducted in Uniontown and State College, PA, during the summers of 1990 and 1991, respectively. As part of these studies, acid aerosol and gas concentrations (NH3, HNO3, HNO2, SO2, H+, NH4+, NO3, SO42−) were measured using five systems: the Harvard/EPA Annular Denuder Systems (HEADS), the Personal Annular Denuder System (PADS), the Continuous Sulfate/Thermal Speciation system (CSTS), the Micro-Orifice Impactor (MOI), and the Harvard Marple Impactor (HI). Concentrations were measured over 3, 12, and 24 h periods, with resultant acid aerosol and gas measurements compared for each system. Results from these studies show excellent agreement among the particulate measurement systems. The sulfate (SO42−), aerosol strong acidity (H+), and ammonium (NH4+) concentrations measured by all systems were highly correlated. In addition, 3 and 12 h particulate measurements were comparable for HEADS, MO1, and PADS samplers. Although significantly different, mean relative differences between HEADS measurements and those obtained using the HI and CSTS (SO42− only) systems were small. For the gases nitric acid (HNO3) and sulfur dioxide (SO2), the performance of the HEADS sampler was found to be independent of sample duration, as the 3 and 12 h HEADS measurements were comparable. The PADS sampler, however, was found to measure concentrations of both HNO3 and SO2 poorly. PADS measurements, of HNO3 in particular, were significantly lower than corresponding HEADS measurements. These lower values probably resulted from their deposition on the inlet surfaces of the PADS sampler. The performance of the measurement systems for ammonia (NH3), nitrous acid (HONO), and nitrate (NO3−) could not be determined, since their outdoor levels generally were near or below the limit of detection (LOD).

Monitoring Deposition of Nitrogen-Containing Compounds in a High-Elevation Forest Canopy

Measurements of airborne (gaseous and aerosol), cloud water, and precipitation concentrations of nitrogen compounds were made at Mt. Mitchell State Park (Mt. Gibbs, ~2006 m MSL), North Carolina, during May through September of 1988 and 1989, An annular denuder system was used to ascertain gaseous (nitric acid, nitrous acid, and ammonia) and particulate (nitrate and ammonium) nitrogen species, and a chemiluminescence nitrogen oxides analyzer was used to measure nitric oxide and nitrogen dioxide. Measurements of NO3 − and NH4 + ions in cloud and rain water samples were made during the same time period. Mean concentrations of gaseous nitric acid, nitrous acid, and ammonia were 1.14 μg/m3, 0.3 μg/m3, and 0.62 μg/m3 for 1988, and 1.40 μg/m3,0.3 μg/m3, and 1.47 μg/m3 for 1989, respectively. Fine particulate nitrate and ammonium ranged from 0.02 to 0.21 μg/m3 and 0.01 to 4.72 μg/m3 for 1988, and 0.1 to 0.78 μg/m3 and 0.24 to 2.32 μg/m3 for 1989, respectively. The fine aerosol fraction was dominated by ammonium sulfate particles. Mean concentrations of nitrate and ammonium ions in cloud water samples were 238 and 214 μmol/l in 1988, and 135 and 147 μmol/l in 1989, respectively. Similarly, the concentrations of NO3 and NH4 + in precipitation were 26.4 and 14.0 μmol/l in 1988, and 16.6 and 15.2 μmol/l in 1989, respectively. The mean total nitrogen deposition due to wet, dry, and cloud deposition processes was estimated as ~30 and ~40 kg N/ha/year (i.e., ~10 and ~13 kg N/ha/growing season) for 1988 and 1989. Based on an analytical analysis, deposition to the forest canopy due to cloud interception, precipitation, and dry deposition processes was found to contribute ~60, ~20, and ~20 percent, respectively, of the total nitrogen deposition.

Measurement of Atmospheric Formic and Acetic Acids: Methods Evaluation and Results from Field Studies

Formic and acetic acids are important contributors to atmospheric acidity, present in low and subparts per billion by volume (ppbv) range. This paper presents the results of laboratory and field studies to evaluate the performance of an annular denuder system to collect gas-phase formic and acetic acids. The collection efficiencies for formic and acetic acids by a KOH-coated annular denuder have been determined to be 99.1% and 98.5%, with precisions of 1.9% and 1.2% and capacities greater than 5.08 and 1.36 mg, respectively. The extracts of samples with chloroform added as a biocide have been shown to be stable for storage periods of 4 months at 4°C in the dark. Interference by aldehydes with measurement of formic acid and acetic acid was determined to be small

Chemical and Physical Properties of Emissions from Kuwaiti Oil Fires

After the Iraqi retreat from Kuwait in 1991, airborne sampling was conducted in the oil fire plumes near Kuwait City and ground-level samples were taken of the air within the city. For the airborne sampling, a versatile air pollution sampler was used to determine the SO2, elemental concentrations, the aerosol mass loadings and SO42− and NO3 concentrations. Striking differences between the black and white plumes were associated with high concentrations of NaCl and CaCI2 measured in the white plumes and large numbers of carbon chain agglomerates in the black plumes. For the ground-based measurements, an annular denuder system was used to determine levels of SO2, SO42−, trace elements, and mass loadings. Certain pollutant levels rose in the city during inversion conditions, when winds were too weak to continue moving the combustion products directly to the Persian Gulf, and the increased levels of Pb and certain trace elements were comparable to those in other large urban areas in Europe. This paper has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and administrative review policies and approved for presentation and publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Measurement and evaluation of acid air pollutants in Chicago using an annular denuder system

The cyclone/annular denuder/filter pack sampling system (ADS) was used to collect and evaluate ambient air pollutants in Chicago. Eighty-one 12-h samples, equally divided into day/night intervals, were collected from April 1990 to March 1991. The chemical species measured were HNO 3, HNO 2, SO 2 and NH 3 in the gas phase, and SO 4 2−, NO 3 −, NH 4 +, and H + in the particulate phase. The ADS data were collected simultaneously with PM10 samples. The particulate matter was analysed for elemental composition. These compositions were combined with the ADS observations and subjected to evaluation using a chemical mass balance receptor model (CMB). From the CMB analysis, the sum of the contributions from soil (15%), mobile (14%), incinerator (2%), coal (0.6%), steel (0.3%) and refinery (0.2%) was 32% of the PM10. NO 3 −, which was not included in the fingerprints, represented an additional 9% of the PM10. Residual SO 4 2− and residual organic carbon, possibly formed in the atmosphere, represented an additional 22 and 20% of the PM10, respectively, leaving only 17% from other unidentified sources. From the standpoint of source contributions of sulfur and nitrogen compounds, coal combustion (23%) and refinery emissions (23%) are the major contributors of ambient sulfur (with 49% from unidentified sources). Mobile sources (87%) contributed most of the ambient nitrogen (with only 2% from unidentified sources).

Intercomparison of annular denuder and filter pack sampling methods for collection of acidifying species in south east England

Both annular denuder system (ADS) and filter pack (F.P) samplers exhibited a broad agreement. However, the F.P sampler collected higher concentrations of large particles reflecting better inlet characteristics. The F.P sampler also overestimated measurements of NH 3, HCl and HNO 3 primarily due to evaporation of ammonium chloride and ammonium nitrate to their precursor gases. Sulphate particles showed good accord in both samplers. It is very important to stress that these techniques may vary from one place to another.

Comparison of annular denuder and filter pack collection of HNO3 (g), HNO2((g), SO2 (g), and particulate-phase nitrate, nitrite and sulfate in the south-west desert

During the 15 January–4 February 1986 SCENES Special Study, a comparison study was conducted to determine atmospheric HNO3 (g), HNO2 (g), SO2 (g), and particle-phase nitrate, nitrite and sulfate sampled with annular diffusion denuder and filter pack sampling systems for 12-h periods. The results of the ion chromatographic analyses of the denuder and filter extracts from the annular denuder system showed that an average of 88% of the total nitrate measured was HNO3 (g), 97% of the total nitrite was HNO2 (g), and 91% of the total sulfur was present as SO2 (g). Analyses of the various gas-phase species collected by replicate annular denuder systems indicated that a precision of ± 3% to ± 18% was achieved using these denuders. The good agreement in HNO3 (g) concentrations observed between the filter pack and the denuder (r2=0.873, slope=1.06±0.03, intercept=0±3.5 nmol m−3) results from the fact that the majority of the atmospheric nitrate consisted of HNO3 (g), which minimized any positive artifact in HNO3(g) due to loss of HNO3(g) from particles collected in the filter pack. The particulate-phase nitrate correlation between the two sampling systems was not as good (r2=0.709, slope=0.519±0.045, intercept =0±1.2 nmol m−3) because the lower percentage of nitrate present as the particulate species was more affected by the loss of particulate nitrate during sampling with the filter pack.