Particulate Monitoring

PM10 and PM2.5 Background InformationPM10 Monitor

The Clean Air Act established National Ambient Air Quality Standards (NAAQS) to protect public health and welfare. To help states comply with the NAAQS, EPA created national rules to reduce emissions from power plants (stationary sources) and mobile sources (trucks and automobiles). EPA reviews the NAAQS standards every five years to ensure the standards are based on the latest scientific research and set at a level that is protective of public health and welfare.

One of the pollutants is particulate matter or PM, which is a complex mixture of extremely small particles and liquid droplets present in the air (aerosol). Once inhaled, these particles can affect the heart and lungs and may cause serious health effects. PM is usually measured in two size ranges, PM10 and PM2.5. PM10 refers to airborne particles with diameters that are less than or equal to 10 microns in size (a micron is one-millionth of a meter, or about 1/7 the diameter of a human hair).  PM2.5, consists of fine particles with diameters that are less than or equal to 2.5 microns in size, and when inhaled these can cause adverse cardiovascular health effects.

PM10 Ambient Monitoring

Virginia's first PM10 monitor was installed in January1988; this was the beginning of the Virginia Ambient Air Monitoring Network sampling for inhalable particulate. Over the years there have been dozens of PM10 monitoring sites around the state, but the PM10 monitoring network was dramatically reduced when the PM2.5 standard was enacted by EPA in 1997. There are currently nine PM10 monitoring sites in Virginia.  PM10 is currently monitored in the following cities/counties: Galax, Winchester, Henrico, Hopewell, Hampton, Norfolk, Stafford, Fairfax, and Alexandria.

PM2.5 Ambient Monitoring

PM2.5 Monitor

EPA established regulatory requirements and NAAQS for PM2.5 in 1997 and Virginia's PM2.5 monitoring network began operating in January 1999. The current PM2.5 Monitoring Network for Virginia has been developed following the requirements of 40 CFR Part 58 and applying EPA's "Guidance for Network Design and Optimum Site Exposure for PM2.5 and PM10" .  Virginia has both continuous PM2.5 monitoring as well as 24-hour sequential samplers.

24-Hour PM2.5 Samplers - The Federal Reference Method (FRM) PM2.5 sequential samplers used in Virginia are manufactured by Thermo Fisher Scientific. The PM2.5 sequential samplers collect a 24-hour sample on a stretched Teflon filter. Most samplers in Virginia collect a sample once every three days as required by EPA, however there are few monitoring sites in Virginia where the samplers operate every day.  Please see the following links for the annual averages and quarterly averages for Virginia’s PM2.5 FRM network:


Please send your comments or questions on PM2.5 data to Namita Verma

24-Hour Speciation - At present there is only one PM2.5 Chemical Speciation Network sampling site operating in Virginia at the MathScience Innovation Center in Henrico County; Operating on a one-in-three day sampling schedule, two samplers collect fine particulate matter. The two samplers are: MetOne SASS unit utilizing nylon and Teflon filters and a URG 3000 Carbon Sampler utilizing a quartz filter.  After a 24-hour sampling period, the samples are picked up by the operator and shipped refrigerated to Wood PLC, the EPA contract lab for shipping and weighing filters. This lab analyzes the filters for gravimetric mass and the samples are sent for chemical speciation analysis to UC Davis.
The following analyses are done:
  • Teflon filter: total mass loading in ug/m3, and thirty-three trace elements (such as: aluminum, antimony, arsenic, bromine, iron, lead, vanadium, zirconium)
  • Nylon filter: cations (ammonium, potassium, sodium), anions (nitrate, sulfate)
  • Quartz filter: carbons (carbonate carbon, elemental carbon, organic carbon, total carbon)

These samples give a "chemical fingerprint" of air masses moving through the Richmond area.  This data, in conjunction with past data from the former Virginia speciation sites, and data from other states give a representative picture of the constituents of the air samples, which help identify sources of high values, and show how the air masses move over a broad area.

Continuous Mass Monitors - Virginia operates a network of continuous PM2.5  mass samplers which are used for Air Quality Index (AQI) forecasting . The continuous measurements provide hourly averages in ug/m3 and provide real-time PM2.5 ambient levels. Some of the samplers are Thermo Fisher Scientific TEOMs (Tapered Element Oscillating Microbalance) and some are Federal Equivalent Method (FEM) Thermo 5014i beta attenuation Monitors.

Please send your comments or questions on the PM2.5 monitoring network operations to Anton Sorkin.

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Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000


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