Russell W. Wiener

Performance evaluation of the portable MiniVOL particulate matter sampler

Abstract The MiniVOL sampler is a popular choice for use in air quality assessments because it is portable and inexpensive relative to fixed site monitors. However, little data exist on the performance characteristics of the sampler. The reliability, precision, and comparability of the portable MiniVOL PM10 and PM2.5 sampler under typical ambient conditions are described in this paper. Results indicate that the MiniVOL (a) operated reliably and (b) yielded statistically similar concentration measurements when co-located with another MiniVOL (r2=0.96 for PM10 measurements and r2=0.95 for PM2.5 measurements). Thus, the characterization of spatial distributions of PM10 and PM2.5 mass concentrations with the MiniVOL can be accomplished with a high level of confidence. The MiniVOL also produced statistically comparable results when co-located with a Dichotomous Sampler (r2=0.83 for PM10 measurements and r2=0.85 for PM2.5 measurements) and a continuous mass sampling system (r2=0.90 for PM10 measurements). Environmental factors such as ambient concentration, wind speed, temperature, and humidity may influence the relative measurement comparability between these sampling systems.

Design and Calibration of the EPA PM2.5 Well Impactor Ninety-Six (WINS)

The EPA well impactor ninety-six (WINS) was designed and calibrated to serve as a particle size separation device for the EPA reference method sampler for particulate matter under 2.5

Technical Note: Performance of a Personal Electrostatic Precipitator Particle Sampler

Filter-based methodsused to measure aerosols with semi-volatile constituents are subject to biases from adsorption andvolatilization that may occur during sampling(McDowandHuntzicker 1990; Turpin and Huntzicker 1994; Volckens et al.1999; Tolocka et al. 2001). The development and evaluation ofsuitable methods for quantitative measurement of semivolatileorganic aerosols is of public health signi” cance because thisclass of chemicals can include polycyclic aromatic hydrocar-bons, pesticides, and many other known toxins(Harkov 1986;Finlayson-Pitts and Pitts 1999). Furthermore, the need existsfor personal exposure measurements, since microenvironmen-taloroutdoorsurrogateshavebeenshowntohavelimitedutility(Wallace 1996; Rodes et al. 1991). Previous laboratory and” eld studies have demonstrated that electrostatic precipitationmay be an effective means for sampling such aerosols(Leithet al. 1996; Volckens et al. 1999, 2000). However, samplesof semivolatile aerosols collected by electrostatic precipitators(ESPs)aresusceptibletoreactionsanddegradationduetoozonegenerated by the corona(Kaupp and Umlauf 1992).Although

Federal Reference and Equivalent Methods for Measuring Fine Particulate Matter

In the national ambient air quality standards specified by the U.S. Environmental Protection Agency in the Code of Federal Regulations, new standards were established for particulate matter on July 18, 1997. The new particulate matter standards specify mass concentration as the indicator for fine particulate matter (aerodynamic diameter of 2.5

The effect of a tall tower on flow and dispersion through a model urban neighborhood: part 1. Flow characteristics.

Wind tunnel experiments were performed to examine the effect of a tall tower on the flow around an otherwise uniform array of buildings. Additionally, preliminary CFD simulations were run to visualize the flow with more resolution. The model used in both the wind tunnel and CFD studies was designed to simulate an area of Brooklyn, NY, USA, where blocks of residential row houses form a neighborhood bordering a major urban highway. This area was the site of a field study that, along with the work reported here, had the goal of improving the understanding of airflow and dispersion patterns within urban microenvironments. Results reveal that a tall tower has a dramatic effect on the flow in the street canyons in the neighboring blocks, enhancing the exchange between the street canyon flow and the freestream flow aloft. In particular, vertical motion down the windward side and up the leeward side of the tower resulted in strong flows in the lateral street canyons and increased winds in the street canyons in the immediate vicinity of the tower. These phenomena were visible in both the wind tunnel and CFD results, although some minor differences in the flow fields were noted.

On the modification of the low flow-rate PM10 dichotomous sampler inlet

A popular flat-topped inlet used for the collection of atmospheric particulate matter was modified to reduce water intrusion during rain and snow events. Simple alterations in the intake region of this inlet were made, including a larger drain hole, a one piece top plate, and louvers. Wind tunnel tests were performed at 24 km/h for fine particle aspiration and at 2, 8, and 24 km/h for coarse particle sampling characteristics of the modified design. The laboratory evaluations of this inlet for fine (PM2.5) and coarse (PM10) particle sampling demonstrated that the aspiration characteristics of this inlet were identical to those of the original inlet. This inlet should greatly reduce, if not totally prevent, the intrusion of precipitation. Further, sampling effectiveness test results suggest that the modified inlet could be substituted for the original inlet where the original inlet is part of a designated reference or equivalent method sampler for PM10.

Field Performance of PM2.5 Federal Reference Method Samplers

The results of several research field studies were evaluated to estimate the precision and bias of various designated PM2.5 Federal Reference Method (FRM) samplers. Precision was favorable in these carefully conducted research studies where all operational activities were strictly controlled, with an average coefficient of variation (CV) ranging from 2 to 6%. No significant bias was found between the method designations. Comparisons between the designated reference method samplers meet the EPA Equivalent Method Criteria for comparability except for one pair of samplers. In this instance, the

Evaluation of the Loading Characteristics of the EPA WINS PM2.5 Separator

The loading characteristics of the USEPA Well Impactor Ninety Six (WINS) PM2.5 separator was an important design consideration during the separators development. In recognition that all inertial separators eventually overload, the loading surface of the WINS was designed to be easily accessible, replaceable, and cleanable. Prior to promulgation of the method, the loading capacity of the WINS separator was evaluated by measuring its performance after repeated loading with laboratory-generated, high concentration, coarse-mode aerosol. For this purpose, a low flow rate loading wind tunnel was designed and constructed to artificially create coarse mode aerosols composed of Arizona Test Dust. This controlled test atmosphere was sampled by the PM2.5 reference method sampling train, as specified in 40 CFR Part 50, Appendix L, at total aerosol mass concentrations averaging 332

Experimental considerations for the study of contaminant dispersion near the body.

Experimental considerations are discussed for conducting controlled studies of the dispersion of contaminants released near a mannequin. A 183 cm x 183 cm cross section wind tunnel was modified to study the low velocity range of 10 to 100 cm/sec (20 to 200 ft/min). Installation of a removable biplanar slat grid produced turbulent intensities up to 15%. The results of validation testing for selected experimental components are reported, including (1) a minimum, unambiguous velocity measurement capability of 2.0 cm/sec (4.0 ft/min); (2) a minimum required integration interval for velocity and contaminant measurements of at least 3 min; (3) a determination that smoke streamline plume settling may be a problem at velocities < or = approximately 15 cm/sec (approximately 30 ft/min); (4) a determination that a 14% tunnel blockage by the mannequin was not of consequence for frontal measurements; and (5) a finding that the biplanar grid produced turbulence spectra representative of low velocity indoor settings. A deceleration zone was noted that extended 50 cm upstream from the mannequin, with freestream velocities reduced 50 to 60%, 2.5 cm from the chest. A contaminant tracer released as a point source 60 cm upstream typically dispersed laterally only 10 to 15 cm and diluted by a factor of 10(4) before reaching the chest.

Parameterization of meteorological variables in the process of infiltration of outdoor ultrafine particles into a residential building

As part of the Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study, a field investigation was conducted of the mechanisms involved in infiltration of outdoor particles (0.02 microm to 1 microm) into a near-highway urban residential building. Using continuous real-time total number concentration time-series data measured simultaneously at multiple outdoor and indoor locations, the infiltration time was estimated for various indoor sites by using the cross-correlation analysis method. The effects of meteorological variables on infiltration times were also characterized at given locations. In particular, infiltration time was examined as a function of outdoor mean rooftop wind speed. Outdoor and indoor temperature and relative humidity were also investigated in relation to infiltration times. Our results showed that outdoor wind speed was the dominant meteorological parameter affecting the infiltration rate, but no correlation was found with temperature. The outdoor-indoor PM concentration ratio was found to be significantly different for the first and second floors of the test building. Finally, we determined the effectiveness of a protective shelter-in-place area inside the building by calculating infiltration times into the area. We found that the shelter-in-place area offered some protection against the infiltrating particles because of increased attenuation of the outdoor concentration.