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Extramural Research

Monitoring Results Synopsis

PI Project Year Goals Results # Pubs
Cass, G. Experimental investigation of the evolution of the size and composition distribution of atmospheric organic aerosols 2000* Fine particulate compositional characterization PUBLICATION 1: Average ambient fine particulate concentrations have declined; EC, CO, organics and nitrate are higher in winter; sulfate higher in summer, sulfate and EC have declined over past 15 years; nitrate and organics show no marked decline; negative measurement artifact for nitrate due to volatilization from Teflon filters. Q:Highest fine mass in winter - is that also highest hospital admissions? PUBLICATION 2: Urban areas with industrial emission sources appear to have higher mutagenicities per microgram of organic carbon with secondary pollutants playing a lesser, if any, role; if important mutagen-forming reactions occur in the atmosphere they must occur in cold as well as in warm seasons. 2 (CAO)
Chameides, W. Southern Center for the Integrated Study of Secondary Air Pollutants (SCISSAP) 2001 Elucidation of sources and dynamics of O3 and PM2.5 ambient air concentrations in Southeastern U.S. PUBLICATION 1: Inherent uncertainties result in differences between observations and models when using air quality models (AQMs) and suggested that all events making up spatial distribution of O3 be utilized rather than episodic events as they provide closer correlations. PUBLICATION 2: Consideration of a marine boundary layer (MBL) source of particles from H2SO4 nucleation is required to understand aerosol distribution; Aitken mode particles (20-100 nm) are observed in concentrations greater than predicted such that an additional and more constant source other than nucleation (i.e. free troposphere entrainment, horizontal diffusion or unaccounted ocean source) is apparent; the key is the highly nonlinear nature of nucleation of H2SO4 - a threshold value determines onset of nucleation process. 2
Cohen, B. Distribution of H+ and trace metals in ultrafine ambient aerosol 1999 Develop a field method to measure the number concentration and metal content of acidic airborne ultrafine particles, and a personal monitor for ultrafne acid aerosols FINAL REPORT: Ultrafine ambient monitor had 73% deposition efficiency for particles 50 nm and only 40% for <100 nm (particle size distribution on the detector is correlated with particle size distribution in air using efficiency (?)); 60% for 28nm and 50% for <20; higher concentrations of NH4+, SO4-2; and H+ in spring and summer vs fall and winter; nitrate concentrations very low. 3(?)
Eatough, D. Continuous measurement of PM2.5 and associated semi-volatile particulate species 1999 Design real-time ambient mass sampler (RAMS) to avoid errors in mass determination of PM2.5 due to loss of semi-volatile material (ammonium nitrate, organics) during sampling or addition of particle-bound water FINAL REPORT: Water minimization, good size selection; good agreement with conventional (denuder) sampler while RFM sampler has 30-40% loss of volatile mass; precision improved with change from cellulose portion of filter to glass fibers PUBLICATION 1: Ambient fine particulate concentrations (mass)are not well correlated with indoor fine particulate correlations, however ambient fine mass shows some correlation with soot and ultrafine particles. PUBLICATION 2: Development of fine particulate samplers w/ denuders (EM-, PC- and W-Boss); W-Boss has precision of + 0.8 g/m3, others poor; FRM and TEOM under measure PM2.5 ~20%. PUBLICATION 3: Diffusion denuder sampling system (PC-BOSS) combined with particle concentrator eliminates positive and negative sampling artifacts observed in FRM; 20% of volatilized material is ammonium nitrate and 80% fine particulate SVOC; positive artifact due to gas-phase material adsorption with 99% removal by PC-BOSS; denuder lifetime ~ few months; addition of Naflon-dryer and TEOM to PC-BOSS is RAMS. 3 + 9(?)
Friedlander, K. Morphological and chemical characteristics of the submicron atmospheric aerosol: implication for standards 2001 To establish the prevalence and physical properties of ultrafine (<0.1 m) and accumulation (0.1 to 1.0 m) particles, to determine certain characteristics of these particles as related to health, to characterize ambient atmospheric aerosol PUBLICATION 1: Evaluation of versatile aerosol concentration enrichment system (VACES) that enriches concentrations of ambient coarse, fine and ultrafine particles; volatile species (e.g. ammonium nitrate) are preserved; results show no occurrence of particle coagulation; results indicate that ultrafine particles collected without loss; detailed morphological examinations indicate ultrafine particles collected without substantial changes in compactness or denseness. 1 + 1(?)
Hochgreb, S. Investigation of the formation of particulate matter in spark-ignited engines   Develop an experimental database of PM emissions (mass rate, composition, number and size distribution) from engines; develop and apply a time-resolved diagnostic for the measurement of instantaneous PM concentrations; use the developed database to characterize and quantify the important processes that control PM formation and oxidation in the engine; and develop a physical model for the PM formation and oxidation processes. CAO WEB PAGE: At high flow rates (Re > 60,000 and residence time 0.5 sec) as dilution ratio increases, cooling increases and HC vapor condensation on existing particles increases, thereby increasing particle mass with particle concentration increasing up to a dilution ratio of 15:1 and then decreasing; at low flow rates (Re < 9,000, residence time 3.5 sec) dilution ratio does not affect temperature and hence does not affect condensation rate and as dilution ratio increases, particle concentration decreases up to 15:1 ratio, then no longer affected; particle numbers decrease by 4% due to loss on walls, but mass concentration increases by 16% due to condensation and absorption; at lean air-fuel ratios (HC emissions high) PM emissions increase in number and mass; injection of liquid fuel in cylinder increases PM formation; chemical analyses ongoing. 0
Johnston, M. R823980 Speciation of volatile and reacting compounds in particulate matter 1998 Speciation of volatile and reacting compounds into simple particles by laser desorption ionization mass spectroscopic method (particles ablated with a high energy-pulsed laser beam) FINAL REPORT: With micron-sized particles, the surface layer is preferentially analyzed so total composition of the particle may not be determined correctly if a concentration gradient exists between the surface layer and the particle interior; recommend removal of water prior to analysis by laser desorption ionization to minimize quenching of marker ions and increase accuracy. PUBLICATION 1: NaCl/KCl and NaCl/NaNO3 multicomponent aerosols observed behaving consistent with thermodynamic analysis - as relative humidity(RH) reaches the theoretical deliquescence point the chemical composition of solution on particle surface changes gradually with increasing RH until the particle completes transition to aqueous droplet; this deliquescence occurs at lower points than theory predicts - possibly due to cracks or pores on the surface; the (NH4)2SO4/NH4NO3 aerosols differed from thermodynamic predictions showing absorption of water at low RHs - possibly due to the existence of the particles as metastable aqueous droplets rather than dry particles. 11
Johnston, M. R823980 Speciation of volatile and reacting compounds in particulate matter 1998 Speciation of volatile and reacting compounds into simple particles by laser desorption ionization mass spectroscopic method (particles ablated with a high energy-pulsed laser beam) PUBLICATION 2: Low laser irradiance theorized to desorb and ionize only material near the particles' surface while high laser irradiance ablates a greater fraction of the sample or the particle's surface and core areas; quantitative determination of relative amounts of nitrate and chloride could not be assessed due to large particle-to-particle variations; the increase in particle size due to addition of ammonium nitrate layer is less than the resolution of particle sizer (200 nm increase in the diameter of a 3.5 micron particle); only about 1/4 of the condensation occurs on particles; no accuracy or precision data provided. PUBLICATION 3: Matrix-Assisted laser desorption/ionization (MALDI) used to characterize aerosol particles - liquid and solid; in liquid matrix the analyte theorized to partition between the particle surface and bulk; in solid matrix the analyte theorized to absorb on surface and deposit there after crystallization; particles were of uniform size and composition during each experiment; salt contamination from the aerosol generator was evident, there may be solution characteristics unique to small particles ~2 microns; with solid matrix there is evidence that minor components preferentially deposit in surface layer while major components deposit in particle core.  
Johnston, M. R823980 Speciation of volatile and reacting compounds in particulate matter 1998 Speciation of volatile and reacting compounds into simple particles by laser desorption ionization mass spectroscopic method (particles ablated with a high energy-pulsed laser beam) PUBLICATION 4: Utilization of real-time ambient mass monitors allows for sampling and analysis of particles within a millisecond yielding excellent resolution of particle-to-particle variations and minimizing analyte alterations/reactions during sampling; ideally the inlet should have high transmission efficiency (avoids size bias) but inhibited due: 1) rapid acceleration of entering air stream causing larger particles to hit walls and perturbing flow, and 2) rapid expansion of flow in mass spec source region causing smaller particles to move away from center of flow stream; ideally inlet should also have high flow rates but often long capillary tubes - which have low flow rates - are used to enable particle to attain flow velocity prior to exiting and those with short tubes although flow rates are high the particles do not have sufficient time to reach velocity of the flow; for particle detection and sizing one approach uses 2 continuous laser beams tracking particles thru vacuum chamber - particle passes thru first beam and provides start pulse and after passing thru second stream a stop pulse is generated both by resultant scattered radiation with the inverse of the time difference between pulses proportional to particle velocity; with LDI-MS (laser desorption/ionization with time of flight mass spec) instantaneous detection and analysis are performed with the main problem being bulkiness or non-compatibility with portable usage.  
Johnston, M. R823980 Speciation of volatile and reacting compounds in particulate matter 1998 Speciation of volatile and reacting compounds into simple particles by laser desorption ionization mass spectroscopic method (particles ablated with a high energy-pulsed laser beam) PUBLICATION 5: The mass spectra of single aerosol particles found to vary with humidity in 1 or 3 ways; depending on species: 1) sharp transition between a "wet"-particle spectrum and a "dry"-particle spectrum over a narrow humidity range (65-70 %) for sodium and ammonium chloride, 2) gradual spectral transformation over a broad humidity range (7 - 70%)for ammonium nitrate, and methanesulfonic acid, and 3) no spectral change with humidity for ammonium sulfate; wet particles yield very different spectra from their dry counterparts and signal quenching in wet particle spectra can be severe in multi-component aerosol compositions; in mixed compositions only nitrate and chloride could be unambiguously identified. PUBLICATION 6: On-line and real-time analysis of particles through nozzles may have biased results especially surface chemical characterizations due to condensation of vapors onto particles; increasing lag time (difference between particle residence time and fluid residence time) and capillary length increases condensation; condensation of water vapor is the main source; particle condensation can be significant even for low vapor concentrations and low surface accommodations; one possible solution is to dry carrier gas prior to sampling but this may affect aqueous particle compositions; with certain industrial sampling the presence of other volatile species in large amounts may contribute to particle growth as well. PUBLICATION 7*: Positive ion mass spectra of ultrafine particles are similar to those of micron size particles although ultrafine particles may have lower cluster signal intensities, ultrafine particles produce few (or none) atomic or molecular negative ions with electron emission occurring instead; positive ion signal intensities decrease only slightly with decreasing particle size; a small particle exhibits a higher ion yield than a large particle due to greater fraction of particle vaporized and lower probability of positive-negative charge recombination. (*See Wexler)  
Kinney, P. Columbia personal exposure study 2000 Characterize levels of and relationship among personal, indoor, and outdoor urban air toxics, using 2 high schools - 1 in New York city and the other in Los Angeles, monitoring of PM2.5 (mass and metal concentrations), VOCs and aldehydes, field work expected to be completed by the end of 2000 Ongoing (Mickey Leland Center) 6(?)
Koutrakis, P. R825336 Development and Validation of a Novel Technique to Measure Ambient Particle Properties: Bound Water, Mass, Density, and Mean Diameter 1999 Develop and test - in an urban atmosphere - a continuous mass sampler for determination of mass, density, mean diameter and bound water PUBLICATION 1: In general pressure drop decreases slightly with particle size from 0.2 to 1.0 microns for any given pore size and face velocity - indicating pressure drop (PD) is independent of size in this range; there is a sharp increase in PD as particle size gets smaller than 0.2 microns; there is a sharp decrease in PD as particle size gets larger than 1.0 micron due to impaction; particle deposition on pore edges (main mechanism for increasing PD with time) increases with size also overall smaller particles have larger overall surface area so these effects tend to cancel; PD is inversely related to the square root of particle density; PD nearly doubles as humidity decreases (33 - 10%) possibly due to greater deposition via electrostatic mechanisms; at higher humidities (33 - 40 %)greater PD due to loading of liquid particles; for hygroscopic particles with humidities from 10 - 50 % PD decreases dramatically; the increase in PD with particle loading can be used to measure particle concentration when particle density and size are known. PUBLICATION 2 (Abstract Only): A Continuous Ambient Mass Monitor (CAMM) was developed that uses fibrous (Fluoropore®) filter and compared to FRM that uses Teflon® filter; CAMM uses filter tape transportation system allowing for several weeks of sampling - 1 hr periods; CAMM has minimum volatilization and adsorption artifacts and allows for control of relative humidity; ambient air in 6 urban cities was sampled; NH4NO3, NH4SO4, elemental and organic carbon and metal oxides were measured. 3 + 3(?)
Koutrakis, P. R825270 Development and Evaluation of a Novel Sampling Method to Determine the Phase Partitioning of Semi-Volatile Organic Compounds 2000 Develop and evaluate sampling method that separates particulate and gas phases of semi-volatile organic compounds and minimizes reactions during sampling of collected material with any reactive gases (O3, HNO3, HONO, and SO2) that might be present PUBLICATION 2: Particle losses due to bounce-off and re-entrainment were minimized with this high volume inertial impactor; particles were collected on a polyurethane foam; polyurethane foam is inert and nontoxic; the sampler can operate for a few hours or for a week or more; this sampler can be used in exposure and/or source apportionment studies because it collects lots of particles in a short time; however for trace organics and biological and toxicological information long time periods are best; solvent extract volumes required for particle recovery are smaller than with conventional fine samplers. 2 + 2(?)
Lippman, M. Development of a continuous monitoring system for PM10 and components of PM2.5 2000 Develop a PM mass monitor for: ultrafine particles; PM2.5; PM10; NH4NO3; particle-bound water; and organic compounds FINAL REPORT: The monitor reduces negative (from volatilization) and positive (from adsorbed water) artifacts in sampling; has 3 size-fractions: coarse (PM2.5-10), accumulation mode (PM0.15-2.5), and ultrafine (PM0.15 and smaller); good precision and efficiency. 1(?)
Ondov, J. R825269 Development of a semi-continuous monitor for determination of trace elements and heavy metals in ambient aerosol particles 1999 Develop a semi-continuous system for determining concentrations of various elemental components of fine particles FINAL REPORT: The monitor found to be accurate multi-element aerosol particle sampler with data down to a 30-minute resolution scale; collection efficiency ~ 95%. PUBLICATION 1: Monitor developed for collection of particles from 0.5 to 2.5 microns had an efficiency > 80%; flow rate is 50 L/min 45 or 60 minutes (FRM is 15.7 L/m3 for 24 hours); particles collected in a slurry at < 0.1 mL/min and can then be analyzed via furnace atomic spectrometry or inductively coupled plasma mass spectrometry. 1 + 3(?)
Ondov, J. R825247 Atmospheric fate and dry deposition of urban soot to Great Waters using a novel, state-of-the-art particulate tracer 1999 Develop optimum tracer techniques to investigate behavior and deposition characteristics of soot particles FINAL REPORT: Measurement precision of + 0.2% for ambient aerosol samples with 1-10 pg of Iridium (Ir) and a detection limit of 150 fg was obtained using isotope dilution mass spectrometry; analysis by instrumental neutron activation analyzers (INAA) resulted in a precision of + 0.5% and a detection limit of 90 fg; no additional benefit from use of radiochemical neutron activation analyzers (RNAA); Micro-Orifice impactors used to determine differences in size distributions of trace elements and Ir tagged soot particles; the largest errors in particle size measurement occurred at the stage with the smallest cut point, growth for certain elements was observed in fine particles (Selenium - 22.4%, Antimony - 17.8% and Zinc - 14.0%); differences in growth for Cesium were ambiguous; tracer-induced Ir concentrations in submicrometer sizes well above background but size differentiations were difficult to make; iridium concentrations were well above background levels for particles in the submicrometer range with daily variations; for particle sizes of 2.4 - 1 m the background was comparable to the tracer concentrations and was attributed to resuspension and subsequent agglomeration of tagged soot particles; observations of particles at a site downwind showed an 18% growth for submicrometer particles and a 32% growth for 2.4 m particles; large increase in size of the 2.4 particles appears to reflect differences in amounts of resuspended dust; the contribution to the ambient air of particles 2.5 m or smaller was calculated to be 64 kg per year from diesel trucks (tagged soot); the largest contribution to tagged soot mass are particles larger than 4.7 m; IR tracer particles from diesel engines; particle size differences in site downwind from another attributed to inhomogenieties in aerosol plume and differences in levels of resuspended dust; particles were traced to area steel mill, incinerator, coal-fired power plants and more remote Ohio River Valley area through size and metal content; the highest concentrations of Fe, Zn, Cs, Sb and Se associated with steel production; incineration and coal combustion observed at industrial site; short-term PM mass and metal compositions found to be spatially non- 1 + 6(?)
Reynolds, S. Indoor air quality in large office buildings in the Midwest 1999 To characterize indoor air quality and compare (simultaneous measurements) to outdoor air, specific parameters include CO, CO2, organics, particulates and microorganisms, psychological (perception) analyses also done FINAL REPORT: CO2 values within range associated with "non=problem" buildings; typical CO2 values of 1 ppm with highest indoor value of 6 ppm and highest outdoor value of 26 ppm; no statistical difference observed between seasons; statistical difference observed between buildings except for CO2; highest value for themophilic bacteria 66 CFU/m3; PM10 values ranged from 3-71 g/m3; significant relationships between exposure to environmental pollutants and adverse health symptoms reported most prominent for males. PUBLICATION 1: Limonene (semivolatile terpenoid) shown to be a better indicator of environmental air quality (than esters, carbonyls, aliphatic and aromatic hydrocarbons) statistically; limonene was positively correlated with health symptoms; indoor limonene levels significantly higher in winter; indoor limonene from perfumes, cosmetics, beverages, fruits and cleaning agents; states in study (6 buildings) were Iowa, Minnesota and Nebraska; average indoor concentrations of limonene ~0.5 ppbv. 1 + 2(?)
Sarofim, A. Markers for emissions from combustion sources 1997 Develop methods for quantifying the structure and elemental composition of soot to determine potential use as signature for source of particulate carbon in ambient air FINAL REPORT: No PO listed, no final report. PUBLICATION 1: High-resolution transmission electron microscopy (HRTEM) analyzed as potential tool to determine carbon soot morphology and variations in reactivity with changes in conversion percentage; this study showed decrease in reactivity with increasing fractional coverage or conversion whereas an earlier study found the opposite; the unclear issues identified were concentration of inorganic material in soot and number of edge versus face carbon sites. PUBLICATION 2: HRTEM with correct band filtering (software manipulation via SEMPER6P®) of the Fourier transform was necessary to obtain realistic parameter values while eliminating noise and retaining all possible interplanar spacings; the optimum intensity threshold value must be found for consistent analyses with particles of various thickness; quantifiable parameters are circularity, elongation, lateral extent, angular dependence or fringe orientation, interplanar spacing and fractional coverage. PUBLICATION 3: Examination of 3 types of soot from diesel engines used in mining - Idle, Medium and Heavy; the lateral extent mean value of fringes in Medium load was slightly less than the other 2; Interlayer spacings showed the most variation with Idle (4.2 ), Medium 94.6 ) and Heavy (3.9 ); Medium also had the largest number of fringes (486) than either Idle of Heavy (301 and 366 respectively); reasons for difference among soot not clear. 3
Saxena, V. Surface levels of ultraviolet-B radiation under variable conditions of tropospheric air quality and cloudiness 2000 Measure UV-B irradiance, characterize the physical-chemical properties of transported aerosol, digitize cloud cover, evaluate impact of aerosols, cloud cover and solar zenith angle on tropospheric UV-B transmission and determine differences relative to clean and polluted air. PUBLICATION 1: Clouds can substantially reduce incoming UV-B radiation; reflection of radiation occurs and can increase radiation levels even on cloudy days when radiation exposure might be deemed to be negligible, however still less than if no clouds were present. PUBLICATION 2: A single-scattering-separate-delta-Eddington model was developed that handles both absorption in the stratosphere and anisotropic scattering within optically thin cloud layers better than conventional Eddington models and is easier to use; this method allows for determination of when scattering is important and when conventional model is good approximation (adequate for optically thin molecular scattering layers without strong absorption and for cloud or aerosol layers with optical depths > 10); this model also enables study of coupling between scattering and absorption within compositionally complex atmospheric layers. PUBLICATION 3: A dip occurs in the normalized transmission at wavelengths < 320 nm (due to coupling of multiple scattering by aerosol particles and absorption by O3 and to rapidly increasing absorption coefficient of tropospheric water-soluble particles); important to note that the combination of aerosols and O3 results in greater decrease in UV than a simple sum of separate influences; there is an increase in normalized atmospheric transmission at wavelengths > 320 nm which implies that the radiative properties of aerosols cannot be assumed constant in the visible band of spectrum; depending on humidity levels urban aerosols reduce transmissions. 6+ 8(?)
Saxena, V. Surface levels of ultraviolet-B radiation under variable conditions of tropospheric air quality and cloudiness 2000 Measure UV-B irradiance, characterize the physical-chemical properties of transported aerosol, digitize cloud cover, evaluate impact of aerosols, cloud cover and solar zenith angle on tropospheric UV-B transmission and determine differences relative to clean and polluted air. PUBLICATION 4: No substantial change in aerosol optical depth noted in the past 30 years comparing this data with previous; differences in optical depth shown in air masses from highly polluted versus polluted marine versus polluted continental source regions; highly polluted air masses showed lowest mean UV-B transmissions; empirical relationships developed for optical depth and UV-B transmissions; aerosol single scatter albedo varied greatly with a heavier dependence on humidity than air mass type. PUBLICATION 5: Black carbon (BC) mass concentrations averaged 217 ng/m3 in polluted air, 170 ng/m3 in continental air, and 66 ng/m3 in marine air; higher average BC mass concentrations associated with higher influences from polluted and continental air masses; BC and cloud condensation nuclei (CCN) showed positive correlation suggesting a percentage of BC may be in form of internal mixture; the amount of BC measured in cloud water too low to significantly effect absorption of solar radiation by clouds; the amount of BC incorporated in cloud droplets is small fraction of total; the observed BC/sulfate ratios will only slightly reduce negative direct forcing by sulfate.  
Saxena, V. Surface levels of ultraviolet-B radiation under variable conditions of tropospheric air quality and cloudiness 2000 Measure UV-B irradiance, characterize the physical-chemical properties of transported aerosol, digitize cloud cover, evaluate impact of aerosols, cloud cover and solar zenith angle on tropospheric UV-B transmission and determine differences relative to clean and polluted air. PUBLICATION 6: When clouds are superimposed on aerosol profile with cloud drops and particles externally mixed the normalized transmission spectrum is dominated by effect of cloud drops; the influence of aerosols in external mixtures decreases with increasing optical cloud depth; when cloud drops and particles are internally mixed through coagulation the normalized transmission spectrum is still dominated by cloud drop effects unless there is an unrealistically high volume fraction of soot but the influence of aerosols increases with increasing optical cloud depth; the number density or optical depth of aerosol particles has a higher influence on magnitude and shape of transmission spectrum than variations in interstitial optical depth or volume fraction of absorbing inclusions; in continental and urban areas prone to high aerosol loadings the attenuation of clouds with optical depths of 10 or less may either increase or decrease with wavelength depending on atmospheric conditions.  
Smith, K. Real-time analysis of PAH bound to size-resolved atmospheric particles by tandem time of flight mass spectrometers 2000 Develop and demonstrate an aerosol mass spectrometer capable of quantifying polycyclic aromatic hydrocarbons (PAHs) associated with individual size-segregated atmospheric particles in real time PUBLICATION 1: For aerosols containing volatile and semivolatile species, the aerosol mass spectrometer developed provides good quantitative data on particle size as a function of chemical composition; aerodynamic particle diameter is determined by measuring particle velocity via time of flight (TOF); fast particle detection is through flash vaporization of volatile and semivolatile components; collection efficiency is ~ 100% for aerodynamic diameters from 70 - 500 nm; spherical and/or larger particles focused more efficiently than non-spherical and/or smaller particles; particles with insufficient mass (< ~2 x 10-14 gm) cannot be detected without averaging mass spec ion signals over many TOF periods; this method tested for pure compounds and tests must be run for multi-component compounds; measurement of mass loading as a function of aerodynamic diameter can provide more in depth and faster information than FRM; particle composition information is limited to size-resolved analyses of particle ensembles. 1 +1(?)
Weisel, C. EOHSI personal exposure study 2000 Show relationship between personal exposure to air toxics and outdoor sources, 3 cities: Los Angeles, CA(mostly mobile sources); Houston, TX (mostly industrial point sources); and Elizabeth, NJ(mostly area and point sources) , 100 homes in each city with ambient and personal monitors, monitoring for: PM2.5 (mass and metals); VOCs and aldehydes Field work done by 2/01, sample analyses done by 5/01. (Ongoing) Mickey Leland Center ?
Wexler, A. Real-time measurement of the size and composition of atmospheric particulate matter 2000 Development and evaluation of a portable monitor that sizes and analyzes particles in the 10 nanometer to 2 micrometer range PUBLICATION 1: The mass flow rate of particles exclusively depends upon a modified Reynolds number; one-dimensional models are adequate for approximating mass flow through sonic nozzles; beams produced by capillaries have lower angular spread than those by conical nozzles; in conical nozzles the beams have a sharp focal point downstream where the beam width is minimum and beams diverge sharply after focal point; in capillaries the focal point occurs within the capillary and beams subsequently straighten out; the particle size distribution in beams from conical nozzles varies sharply for different axial locations but not in capillary beams; although capillaries result in beams of low divergence they: allow lower flow rates, lower the radial acceleration near nozzle entrance, have increased nozzle clogging due to inertial deposition of particles on walls, and promote vapor condensation of particles; for nozzles of fixed geometry and operating conditions only particles in a narrow size range are efficiently transmitted hence changing geometry and conditions allows different sizes of particles to be sampled. PUBLICATION 2*: Positive ion mass spectra of ultrafine particles are similar to those of micron size particles although ultrafine particles may have lower cluster signal intensities; ultrafine particles produce few (or none) atomic or molecular negative ions with electron emission occurring instead; positive ion signal intensities decrease only slightly with decreasing particle size; a small particle exhibits a higher ion yield than a large particle due to greater fraction of particle vaporized and lower probability of positive-negative charge recombination. (*See Johnston) PUBLICATION 3: A novel technique for rapid analysis of particles from 1 m to 10 nm was developed; particles are selectively (by size) transmitted via high speed particle beams by varying nozzle pressure; as pressure goes from 760 to 3 torr, optimal particle size goes from 1.8 m to 35 nm; some concerns with negative ion spectra (dominated by free electrons); modifications can be made to achieve 10 m upper limit; efficiency is lowered by deflection by electric field formed by ion optics. 2 + 1(?)

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