Meetings

The next meeting of the RTP Chapter of the Air and Waste Management Association (AWMA) will be held on Tuesday, March 16th, 2010 from 12–1pm. The meeting will be held in Conference Room N110 at the USEPA NCC in Research Triangle Park.

Please join the chapter in welcoming students from NC State, who will present their Emissions Uncertainty Project and Secondary Ozone Standard project.

Emissions Uncertainty: “Focusing on NOx Emissions from Combustion Sources”

Alissa Anderson, Colin Geisenhoffer, Brody Heffner, Michael Shaw and Emily Wisner

Emission factors are important for estimating and characterizing emissions from sources of air pollution. An emission factor is a representative value that attempts to relate the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant. These factors are usually expressed as the weight of pollutant divided by a unit weight, volume, distance, or duration of the activity emitting the pollutant (e. g., kilograms of particulate emitted per megagram of coal burned). Such factors facilitate estimation of emissions from various sources of air pollution. In most cases, these factors are simply averages of all available data of acceptable quality, and are generally assumed to be representative of long-term averages for all facilities in the source category (i. e., a population average). The general equation for emission estimation is: E = A x EF x (1 - ER/100). Where: E=Emissions, A=Activity Rate, EF=Emissions Factor, and ER=overall reduction efficiency, %. The objectives of this project are to: (1) Verify the NOx emission factors from combustion sources with currently available continuous emission monitoring data; (2) Develop quantitative uncertainty indicators for A through E rated emission factors on NOx emissions from combustion sources; and (3) Determine the limitations of applying these quantitative uncertainty indicators to other pollutant and source types.

The Clean Air Act established two types of national ambient air quality standards for the major air pollutants. Primary standards protect public health, while secondary standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings. In 2006, EPA proposed a new metric as a possible secondary ozone standard based on a cumulative peak-weighted index to protect vegetation versus the daily maximum 8-hour average health-related metric (current primary standard). In 2008, the EPA Administrators recommended the secondary ozone standard be the same as the primary ozone standard; however, the secondary ozone standard is now being proposed as a separate standard.

This project performed exploratory analysis on the cumulative peak-weighted index to determine whether the monthly cumulative index varies during the year and whether three-month cumulative index varies from year to year. In addition, we looked into the locations of higher value trends and investigate whether elevation, latitude, or longitude has an impact on the values collected. Moreover, we studied meteorological conditions that may be conducive to high values. Analysis is done using three levels (7, 15, or 21ppm-hour) of proposed values for secondary ozone standards to examine the impact at each of the proposed levels. A comparison will be made between the proposed primary and secondary standards using the percentage of reduction needed for sites violating the primary and/or secondary standard to achieve standard levels. Our initial results show those sites that exceeded the proposed 21 ppm-hour level are located between 35 degrees and 40 degrees North across the United States. This may be due to a longer growing season and suggests that the secondary standard should be adjusted to account for different growing seasons. A possible solution would be to adopt different secondary standards for different growing seasons, based upon latitude.

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