PM10 is particulate matter equal to or less than 10 micrometers in diameter. In January 1988, the first PM10 monitor was installed in Virginia. 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. However, because the new PM2.5 monitors were being introduced and started up in 1999, the PM10 monitoring network was dramatically reduced to free up staff required for the new samplers. There are currently 13 PM10 monitoring sites in Virginia.
In 1997, the U.S. Environmental Protection Agency promulgated new national ambient air quality standards for PM2.5 (particle matter equal to or less than 2.5 microns in diameter). EPA determined that these standards are necessary to protect public health and the environment.
24-Hour Mass Samplers
The PM2.5 monitoring network began at the end of January 1999. The PM2.5 sequential samplers collect a 24-hour sample on a stretched Teflon filter. Most samplers in Virginia collect a sample every third day; however, there are four monitoring sites across Virginia where the samplers operate every day. PM2.5 sequential samplers used in Virginia are manufactured by Thermo Fisher Scientific.
Continuous Mass Monitors
There are currently six continuous PM2.5 mass monitors in the Virginia air monitoring network. The National Park Service operates one for VA DEQ at their air quality monitoring station at Big Meadows. The VA DEQ operates continuous PM2.5 monitors at five sites: MathScience Inovation Center in Henrico County, NASA Langley in Hampton, Round Hill Montessori Elementary School in Roanoke, the air monitoring site in Rest, VA (just above Winchester), and the Albemarle High School site just outside Charlottesville. All six monitors are Thermo Fisher Scientific TEOMs (Tapered Element Oscillating Microbalance). Data is captured as one-hour averages.
At the present, there is only one PM2.5 Speciation sampling site operating in Virginia. This site is at the MathScience Innovation Center in Henrico County, and is classified as a National Mini-Trends site. 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 RTI, the EPA contract lab in North Carolina. This lab then analyzes the filters:
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.
Virginia's PM2.5 Network
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". Please send your comments or questions to Tom Jennings.
PM2.5 Annual Summary Data
PM2.5 Quarterly Summary Data
Please send your comments or questions to Tom Jennings.