Evaluation of the TEOM^® Method for Measurement of Ambient Particulate Mass in Urban Areas

Abstract

IMPLICATIONSSemi-volatile organic and inorganic compounds can represent a substantial fraction of ambient particulate mass. Loss of semi-volatile compounds during filter collection can occur due to changes in the composition of the air sample. Heating of the air sample to a temperature 10-20 °C above ambient to remove particle-bound water can further enhance loss of the semi-volatile constituents of ambient particles. These losses depend on particle composition, which varies with location and time. Thus, it is not possible to determine the true concentration by using empirical factors to correct the observed concentrations. Therefore, to minimize losses of semi-volatile compounds, we recommend that particle mass measurements be made at temperatures comparable to ambient. In urban areas, a substantial fraction of ambient PM can be semi-volatile material. A larger fraction of this component of PM 10 may be lost from the TEOM-heated filter than the Federal Reference Method (FRM). The observed relationship between TEOM and FRM methods varied widely among sites and seasons. In East Coast urban areas during the summer, the methods were highly correlated with good agreement. In the winter, correlation was somewhat lower, with TEOM PM concentrations generally lower than the FRM. Rubidoux, CA, and two Mexican sites (Tlalnepantla and Merced) had the highest levels of PM 10 and the largest difference between TEOM and manual methods.PM 2.5 data from collocation of 24-hour manual samples with the TEOM are also presented. As most of the semi-volatile PM is in the fine fraction, differences between these methods are larger for PM 2.5 than for PM 10 .

Estimating particle exposure in the Mexico City metropolitan area

“…Some might seek to explain this observation by the fact that the heated ''tapered element'' in the TEOM monitor drives off the volatile organic component of the sample ( Allen et al, 1997 ). Recently, German researchers heated the air around a Harvard -Marple impactor to the same operating temperature as the tapered element of the TEOM and its measurements agreed well with those of the TEOM.…”

Evaluation of Time-Resolved PM2.5 Data in Urban/Suburban Areas of New Jersey

“…The narrow end of the tapered element oscillates in response to an applied electric field, and changes in oscillation frequency reflect changes in particle mass on the filter. 8,9 The instrument measures the oscillation frequency every 2 sec and uses the change in frequency to calculate the amount of PM 2.5 added to the filter. The TEOM stores 5-min, 1-, 8-, and 24-hr PM 2.5 averages in a computer connected to the system.…”

Adjusting Tapered Element Oscillating Microbalance Data for Comparison with Federal Reference Method PM2.5 Measurements in Region 5

“…A report on the evaluation of the TEOM method for 10 locations in North America shows that under most conditions, the TEOM underreports concentration when compared with reference filter-based methods. 3 Measurements of PM 2.5 and PM 10 in Kuopio, Finland, found variations in the ratio of filter-based concentration to TEOM-measured concentration. 4 Field trials of the TEOM in Cornwall, United Kingdom, found a nonlinear relationship with …”