How clean the air is depends in part on the airborne concentration of particulate matter (PM). Airborne PM is known to be a significant health hazard, and, as such, the U.S. Environmental Protection Agency (EPA) has set PM standards to help ensure that the air we breathe is clean. Of particular interest are particles smaller than 2.5 microns in diameter, collectively called PM2.5. These small particles are readily inhaled and can be deposited in the lungs. In addition, these airborne particles are largely responsible for haze in the environment. To prevent any further degradation of visibility, the Clean Air Act has established goals for reducing the ambient levels of PM.

Battelle is actively involved with efforts associated with enhancing PM-monitoring capabilities. Since PM plays such a significant role in air quality, there are extensive efforts in place to monitor PM concentrations. Traditionally, monitoring has involved the time-integrated collection of samples to be analyzed in the laboratory. More recently, there has been an increasing interest in establishing methods to monitor PM concentrations continuously in real time.

Continuous monitoring has a number of advantages over the traditional time-integrated sampling techniques. The continuous monitoring results are available almost in real time, whereas with traditional methods laboratory results are frequently not available for several days or even weeks. Continuous data provide a higher degree of time resolution for investigating temporal patterns— typically one hour resolution or less with real-time monitoring vs. 24-hour with time-integrated sampling.

A third benefit of continuous monitors is that they are far less labor intensive. A continuous monitor in the field may run for a month or more without manual intervention. Time-integrated sampling, on the other hand, requires sample set-up, sample retrieval, sample handling, and sample analysis, sometimes on a daily basis. Each of these steps is not only labor intensive but also provides the opportunity for sample contamination.

Recently Battelle performed a verification test of 13 continuous fine particle monitors as part of the EPA’s Environmental Technology Verification (ETV) program. These monitors employ a variety of measuring techniques and provide continuous, near real-time indications of the ambient levels of PM2.5 mass concentration, or of a specific chemical component of the aerosol. The goal of this test is to provide potential purchasers and consumers of the monitors with credible performance data with which to make informed decisions.

The results of this test are expected to be published on the ETV Web site at http://www.epa.gov/etv.

For more information about the particulate measurement program, contact Ken Cowen at (614) 424-5547, cowenk@battelle.org.