|Parnell, Jr., Calvin|
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2007
Publication Date: 3/1/2008
Citation: Wanjura, J.D., Shaw, B., Parnell, Jr., C., Laey, R., Capareda, S. 2008. Comparison of continuous monitor (TEOM) and gravimetric sampler particulate matter concentrations. Transactions of the ASABE. 51(1):251-257. Interpretive Summary: State air pollution regulatory agencies are required to demonstrate that the air quality within the state is in compliance with Federal air quality standards. Compliance with the National Ambient Air Quality Standards (NAAQS) is determined by placing air samplers at community oriented monitoring sites to monitor ambient particulate matter concentrations. Further, some states have required that the emissions from a facility cannot impact downwind particulate matter concentrations such that the concentration at the property line of the facility is in excess of the NAAQS. If the NAAQS concentration limits are violated at the property line of a source, the source may be denied an operating permit or forced to implement additional pollution control equipment. The Federal Reference Method (FRM) PM10 and PM2.5 samplers required for use in monitoring programs to demonstrate compliance with the NAAQS have been shown to report concentrations in excess of true PM10 and PM2.5 concentrations. A method to determine accurate concentrations of PM10 and PM2.5 from measurements of total suspended particulate matter (TSP) has been developed in previous research work. Tapered Element Oscillating Microbalance (TEOM) samplers have been approved by the EPA for use in PM10 monitoring programs. The major advantage of using TEOM samplers is that they are capable of reporting real time concentrations on an automated basis requiring much less labor for maintenance and data processing. However, when a TEOM sampler is configured to measure PM10 concentrations, it uses the same sampler inlet as is used by the FRM PM10 sampler. Thus, PM10 concentrations reported by TEOM samplers face similar accuracy issues as do the concentrations reported by FRM PM10 samplers. The objective of this work was to define the relationship between TSP concentrations measured by TEOM samplers and reference method TSP samplers. Further, once this relationship is established, it may be possible to use the previously developed method to determine accurate PM10 and PM2.5 concentrations from TEOM TSP concentrations. Accurate concentration measurements are essential to the appropriate regulation of agricultural sources. The major findings of this work indicate that the TSP concentrations measured by the TEOM sampler correlate well with concentrations measured by reference TSP samplers but are influenced by the size characteristics of the sampled dust. These results indicate that it is possible to determine accurate TSP concentrations from TEOM concentrations. Further analysis of the size characteristics of the sampled dust can then be used to determine accurate PM10 and PM2.5 concentrations from TEOM TSP concentrations. The results of this work will help to ensure the appropriate regulation of agricultural sources.
Technical Abstract: The Tapered Element Oscillating Microbalance (TEOM) sampler is an EPA designated equivalent method sampler for measuring PM10 concentrations. PM10 refers to the mass fraction of particulate matter suspended in the atmosphere having a nominal aerodynamic diameter less than or equal to 10 micrometers (um). Many state air pollution regulatory agencies have implemented TEOM samplers in monitoring PM10 concentrations for regulatory purposes. Previous research has shown that TEOM samplers over state PM10 concentrations when compared to concentrations measured by collocated Federal Reference Method (FRM) gravimetric PM10 samplers in urban environments. Also, research has shown that the FRM PM10 samplers may report concentrations in excess of true PM10 concentrations by as much as 400%. More accurate measurements of PM10 concentrations can be achieved by measuring total suspended particulate (TSP) concentrations and multiplying the resulting TSP concentrations by the corresponding mass fraction ' 10 µm from a particle size distribution analysis. This manuscript presents the results of collocated TEOM and gravimetric samplers configured to measure TSP concentrations from a Texas cattle feedlot. The objective of this work was to define the relationship between PM concentrations measured by the TEOM and gravimetric samplers and characterize the influence of concentration intensity and particle size on that relationship. The results show that there is a significant positive linear relationship between the concentrations measured by the TEOM and gravimetric TSP samplers. It was observed that in general, the TEOM samplers will report lower TSP concentrations than the collocated gravimetric TSP sampler. Further investigation into these results indicated that the difference in the concentration measured by the TEOM sampler versus the gravimetric TSP sampler (known as the TEOM measurement error) is significantly correlated with the concentration measured by the gravimetric TSP sampler but the nature of that relationship varies by location. However, significant linear relationships were observed between the measurement error of the TEOM samplers and the mass median diameter and geometric standard deviation of the collocated gravimetric TSP sample.