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Ambient Air Quality Monitoring
The District operates an extensive 24-hour air monitoring network to measure ground-level concentrations of criteria pollutants and air toxics in the outdoor ("ambient") air, as well as surface meteorological conditions. Monitoring data is crucial in determining compliance with EPA primary and secondary air quality standards. It also supports the timely reporting of air quality forecasts and long-term health assessments, and tracks the long-term air quality to gauge the effectiveness of emission control and abatement strategies. Monitoring results help ensure the Department's policies reflect the current state of the science.
The District's air monitoring network contains monitoring stations located at the McMillan Reservoir, River Terrace Elementary School, Takoma School, Verizon Center, and Haines Point.
Each of the five station locations is sited based on population density and distribution, the location of stationary and mobile sources, and the historic concentration of particular pollutants. The air that is monitored is representative of the air that most District residents and visitors are breathing.
Each station has equipment that screens the concentration of particular pollutants in the outdoor air. DDOE visits the sites on a daily or weekly basis to perform routine data checks, performance audits, and scheduled maintenance. They also change filters and, depending on the type of sampler, retrieve raw data or achieve other quality assurance or quality control duties.
This network allows the District to conduct the following major activities and functions:
Continuous Monitoring - Real-time measurements are taken using automated sensoring equipment on an hourly basis. Measurments include:
- Carbon monoxide
- Nitrogen dioxide
- Sulfur dioxide
Semi-Continuous Monitoring - Air quality samples are collected using filters or canisters, typically every day or once in every 3 or 6 days, to develop 24-hour average data. The filters are sent to a lab daily for analysis.
- Photochemical Assessment Monitoring Station (PAMS) - Measures ozone as well as ozone precursors and meteorological conditions, which contribute to the formation of ozone, during the ozone season (May to September).
- PM2.5 Chemical Speciation Network (CSN) - Measures PM2.5 as well as fine particulate precursors.
- National Air Toxics Trends Station (NATTS) - The NATTS program is a national monitoring network designed to assess trends in high-risk urban air toxics including black carbon, heavy metals, and hexavalent chromium-VI. The District hosts the first NATTS station in all of EPA Region 3.
Data generated from this monitoring network is carefully reviewed, edited and analyzed prior to submittal into EPA's national air quality database called the Aerometric Information Retrieval System-Air Quality Subsystem (AIRS-AQS), as required under the Clean Air Act.
For more inquiries, please contact Rama Tangirala (use contact information below).