Air Monitoring

Background

The ultimate goal of the Pima County air quality control program is to reduce the concentration of harmful air contaminants in ambient air to safe and healthy levels, and to maintain those levels. A key process in controlling air pollution is to define the nature and extent of air quality problems within a geographical area through monitoring. Ambient air monitoring in Pima County has been conducted by the Pima County Department of Environmental Quality (PDEQ) and its predecessors since the 1960's. Over time, various air pollution monitoring and research programs have been established and revised to meet changing federal regulations and local needs.

Currently, the Pima County monitoring network is being operated by the Technical Operations division of PDEQ. The Environmental Protection Agency has delegated authority to PDEQ to operate the portion of the State or Local Air Monitoring Stations (SLAMS) located in Pima County. In addition to SLAMS, Special Purpose Monitoring Stations (SPMS) are operated to accomplish various objectives. PDEQ also operates and maintains a visibility and urban haze network in Pima County for the State of Arizona. PDEQ also generates an Air Quality Index (AQI) report several times a day for public notification of current air quality conditions.

Monitoring Network Locations, Information and Data

• Air Monitoring Sites - Locations and Information
• Current and Historic Hourly Air Pollution Data
• Historic 24 Hour Particulate Data
• Air Quality Index Report (AQI)
• Current and Historic Air Quality Index (AQI) Reports
• Which of these AQI Reports should I use?
• 2007 Annual Air Quality Data Summary (PDF - 2,790 KB)
• 2007 Annual Air Quality Data Summary Appendix (PDF - 1,109 KB)
• 2007 Monitoring Assessment Plan (PDF - 1,370 KB)
• Beryllium Monitoring Network

Please note: Many of these reports display values for 1-hour PM10 and PM2.5 (particulate matter 10 and 2.5 microns or less in diameter) concentrations. These data values are provided for informational purposes only. The EPA Health Standard for PM10 and PM2.5 is a 24-hour standard, based on the average of 24 hourly readings from midnight to midnight. The EPA has not yet developed a 1-hour standard for PM10 or PM2.5.

Operation of Monitoring Network

The air quality monitoring groups is divided into 3 units; the Field Monitoring unit, the Data Management unit and the Quality Assurance / Quality Control (QA/QC) unit. The field monitoring unit conducts all operations related to routine maintenance, operations, troubleshooting and repair of equipment necessary for air quality monitoring. The data management unit handles all operations related to network operations, data acquisition, management, storing and reporting of data. The QA/QC unit assures the quality and accuracy of the equipment operation and the data recovered.

Almost all routine air quality monitoring data generated by PDEQ are submitted to the U.S. Environmental Protection Agency (EPA) AIRS database system. Most air quality monitoring sites in the PDEQ network are equipped with electronic data loggers designed specifically for the logging of air quality data. These data loggers are programmed to take the electrical outputs from air quality monitoring instruments at a site and transmit this information via a modem to a central computer data acquisition system (DAS) located in the PDEQ offices. This information is then validated to detect possible erroneous readings, and stored in a central database. The information is then reported to the EPA, documented in summary reports, and made available to local agencies, researchers and the public.

Quality Assurance

Local agencies such as PDEQ involved in federal monitoring programs must comply with federal air quality assurance requirements. Each agency must develop and implement a Quality Assurance (QA) program consisting of policies, procedures, specifications, standards, and documentation necessary to:

1. Provide data of adequate quality to meet monitoring objectives, and
2. Minimize loss of air quality data due to malfunctions or out-of-control conditions.

It is the policy of PDEQ to conduct and support appropriate quality assurance activities to ensure that these objectives are met.