Robert W. Vanderpool

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

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

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

Evaluation of PM2.5 size selectors used in Speciation samplers

The separation characteristics of the PM2.5 aerosol size selectors used in speciation samplers developed for the U.S. EPA National PM2.5 Chemical Speciation Trends Network were evaluated under clean conditions. Measurement of particle penetration versus aerodynamic diameter was conducted using an APS 3320 in conjunction with a polydisperse test dust. The resulting penetration curves were integrated with assumed ambient particle size distributions (40 CFR Part 53, Subpart F) to obtain an estimate of measured mass concentration and to predict bias relative to the PM2.5 reference separator. The cutpoint of two sharp cut cyclones, from the family of cyclones developed by Kenny and Gussman (1997), compares favorably with the WINS, although possessing a slight tail that extends into the coarse particle mode. A second cyclone used by the Andersen Corp., AN 3.68, demonstrated the sharpest cut characteristics of the devices tested; however, it possesses a

Methodology for Measuring PM2.5 Separator Characteristics Using an Aerosizer

A method is presented that enables the measurement of the particle size separation characteristics of an inertial separator in a rapid fashion. Overall penetration is determined for discrete particle sizes using an Aerosizer (Model LD, TSI, Inc., Particle Instruments/Amherst, Amherst, MA) time-of-flight measurement device by comparing the number concentration of particles penetrating through a separator to the concentration entering the separator. Critical measurements of separator characteristics are determined using a vibrating orifice aerosol generator to produce the challenge aerosol. Measurements of penetration requiring less precision and accuracy may be determined using nebulized suspensions of polystyrene latex microspheres as the challenge aerosol. The time for measuring a single penetration curve can be reduced from a week using vibrating orifice aerosol to fewer than 2 h using polystyrene latex microsphere aerosol. Validation of the penetration determined with this method was made by comparison to fluorometric techniques. It is estimated that penetration may be measured with an accuracy of ±4%, which is equivalent to an uncertainty of approximately 0.04 μm in cutpoint diameter determination for PM 2.5 separators. The overall accuracy in determining a cutpoint diameter of a PM 2.5 separator (including uncertainty in the creation of test aerosols) is estimated to be better than ±0.09 μm.

Laboratory and Field Evaluation of Crystallized DOW 704 Oil on the Performance of the Well Impactor Ninety-Six Fine Particulate Matter Fractionator

Abstract Subsequent to the 1997 promulgation of the Federal Reference Method (FRM) for monitoring fine particulate matter (PM2.5) in ambient air, U.S. Environmental Protection Agency (EPA) received reports that the DOW 704 diffusion oil used in the method’s Well Impactor Ninety-Six (WINS) fractionator would occasionally crystallize during field use, particularly under wintertime conditions. Although the frequency of occurrence on a nationwide basis was low, uncertainties existed as to whether crystallization of the DOW 704 oil may adversely affect a sampling event’s data quality. In response to these concerns, EPA and the State of Connecticut Department of Environmental Protection jointly conducted a series of specialized tests to determine whether crystallized oil adversely affected the performance of the WINS fractionator. In the laboratory, an experimental setup used dry ice to artificially induce crystallization of the diffusion oil under controlled conditions. Using primary polystyrene latex calibration aerosols, standard size-selective performance tests of the WINS fractionator showed that neither the position nor the shape of the WINS particle size fractionation curve was substantially influenced by the crystallization of the DOW 704 oil. No large particle bounce from the crystallized impaction surface was observed. During wintertime field tests, crystallization of the DOW 704 oil did not adversely affect measured PM2.5 concentrations. Regression of measurements with crystallized DOW 704 versus liquid dioctyl sebacate (DOS) oil produced slope, intercept, and R2 values of 0.98, 0.1, and 0.997 μg/m3, respectively. Additional field tests validated the use of DOS as an effective impaction substrate. As a result of these laboratory and field tests, DOS oil has been approved by EPA as a substitute for DOW 704 oil. Since the field deployment of DOS oil in 2001, users of this alternative oil have not reported any operational problems associated with its use in the PM2.5 FRM. Limited field evaluation of the BGI very sharp cut cyclone indicates that it provides a viable alternative to the WINS fractionator.

Size-selective sampling performance of six low-volume “total” suspended particulate (TSP) inlets:

ABSTRACT Several low-volume inlets (flow rates ≤ 16.7 liters per minute (Lpm)) are commercially available as components of low-cost, portable ambient particulate matter samplers. Because the inlets themselves do not contain internal fractionators, they are often assumed to representatively sample “total” mass concentrations from the ambient air, independent of aerodynamic particle size and wind speed. To date, none of these so-called “TSP” inlets have been rigorously tested under controlled conditions. To determine their actual size-selective performance under conditions of expected use, wind tunnel tests of six commonly used omnidirectional, low-volume inlets were conducted using solid, polydisperse aerosols at wind speeds of 2, 8, and 24 km/h. With the exception of axially-oriented, isokinetic sharp-edge nozzles operating at 5 and 10 Lpm, all low-volume inlets showed some degree of nonideal sampling performance as a function of aerodynamic particle size and wind speed. Depending upon wind speed and assumed ambient particle size distribution, total mass concentration measurements were estimated to be negatively biased by as much as 66%. As expected from particle inertial considerations, inlet efficiency tended to degrade with increasing wind speed and particle size, although some exceptions were noted. The implications of each inlets non-ideal behavior are discussed with regards to expected total mass concentration measurement during ambient sampling and the ability to obtain representative sampling for size ranges of interest, such as PM2.5 and PM10. Overall test results will aid in low-volume inlet selection and with proper interpretation of results obtained with their ambient field use. Copyright