By DEQ Communications Office
Air monitoring is the beginning–and the end–of everything we do at the Utah Department of Environmental Quality (DEQ) to protect and improve Utah’s air. The Division of Air Quality’s (DAQ’s) statewide monitoring network gives us the ability to:
- Collect long-term air-pollution data
- Assess the levels of air pollution relative to regulatory standards
- Prepare three-day forecasts and pollutant trend charts
- Provide real-time air-quality data for the public
- Find solutions when air pollution becomes a problem
If our monitoring data show air-pollution levels above the federal health-based standards, we begin looking for ways to reduce emissions to correct the problem. We have a variety of tools to address air pollution, including air-quality planning, rules and regulations, permit conditions, air-quality research, and enforcement actions. After we implement changes, we monitor again and continue to monitor to see how the rules and/or permit conditions are working. If we don’t see the improvements we need or expect, we look at other options. Throughout the process, we use our monitoring data to gauge how well we’re doing and where we can improve our efforts.
Our data are only as good as our equipment. That’s why our regulatory monitors have to meet strict requirements. The statewide stationary air-monitoring system is designed to measure pollutant levels, ensure compliance with the National Ambient Air Quality Standards (NAAQS), and provide data for air-quality modeling. The equipment we use in our monitoring network has to meet Federal Reference Method (FRM) or Federal Equivalency Method (FEM) requirements. These requirements ensure that our data are accurate and representative of the conditions in the airshed. We follow a prescribed set of procedures that include proper siting, precise calibration, regular maintenance, data validation, and periodic audits to ensure proper equipment functioning. Our quality control/quality assurance procedures certify the accuracy of the data we report to the Environmental Protection Agency (EPA) and the public.
DAQ monitors for two types of pollutants: particle pollutants (such as PM10 and PM2.5) and gaseous pollutants such as oxides of nitrogen (NOx) and ozone. Each type requires slightly different monitoring equipment.
We use filters for particulates (think of your furnace filter, only with the capacity to trap extremely fine particles). Our scientists put these filters on our monitors to collect the particles in the air over a 24-hour period. The filter fills up with particles for 24 hours (the NAAQS have a 24-hour standard for particulates), then the monitor draws air into the next filter for another 24 hours.
Air-monitoring staff go out every week or so to collect and replace the filters at our monitors and bring them back to the lab for weighing. We weigh the filters before we install them, and weigh them again when they are filled. We compare the initial weight to the filled weight to determine the amount of particulates collected on the filter. That number goes into a calculation that includes the airflow to see how much air has gone through the filter. The final sum gives us the mass concentration in micrograms per cubic meter (µg/m3). Since the federal health-based standard is 35 µg/m3 over a 24-hour period, we always hope to see less than the standard average on our filters. Short-term events like a truck idling near a monitor may have an impact, but shouldn’t affect the 24-hour average.
In addition to filter-based methods for collecting particulates, DAQ has a variety of real-time technologies that read particulate levels every five to six minutes. These data from monitoring instruments across the state feed into a central network that we use to populate our air-quality webpage and mobile app. The filter-based method for determining particulate levels takes several days to a week to verify; continuous methods provide real-time data.
DAQ also has the monitoring capability for gaseous pollutants. Our continuous monitoring equipment measures gases in real time, which is helpful during high-ozone episodes. Monitoring sensors can capture changes in ozone levels minute-to-minute, although we typically look at one-hour intervals. This method is particularly helpful for pollutants that can vary significantly over a shorter time span. For example, because ozone is formed through a photochemical reaction, if the sun goes behind the clouds or sets at the end of the day, we can see the ozone levels dropping in real time.
Real-time Data for the Public
DAQ monitors serve another important purpose besides mapping trends and measuring our compliance with federal health-based air-quality standards: they provide the public with real-time data on current air-quality conditions. These data are particularly important for sensitive populations such as children, the elderly, and those with respiratory conditions or cardiovascular ailments. Users of our webpage and phone app can access real-time air-quality conditions, action alerts, air quality index information, and three-day forecasts — information they can use to plan their day, limit outdoor activities, or make different transit choices.
Monitoring informs everything we do at DAQ — from our air-quality modeling to our planning, from our permit conditions to our rules. Monitoring shows us when and where there’s a problem and verifies whether we’ve adequately addressed the problem. It helps us predict bad-air days so we can issue voluntary and mandatory action alerts to keep air pollution from getting worse. It provides critical information for people with respiratory issues. While monitoring can’t prevent our air-pollution issues, it plays a key role in remedying them.