The Air Monitoring section of the MDAQMD is charged with monitoring the air in compliance with the Federal Clean Air Act and California air pollution laws.
There are certain pollutants that are found almost everywhere that are harmful to humans if their concentration in the ambient air is above certain levels. In the United States, National Ambient Air Quality Standards (NAAQS) have been set for each of these pollutants.
These standards include six pollutants: particulate matter(PM), sulfur dioxide (SO2), nitrogen dioxide(NO2), carbon monoxide(CO), photochemical oxidants(O3), and lead(Pb).
For each criteria pollutant except carbon monoxide, both primary and secondary standards have been established. The primary standards are set at levels that protect public health. If the ambient concentrations of those pollutants remain below their primary NAAQS, it is believed that the most sensitive member of the public will not be harmed by breathing the air. The secondary standards are set at levels that protect public welfare. This means that if concentrations remain below the secondary standards, crops, buildings, etc., will not be damaged. Continuously monitoring the air tells us whether or not we are "in compliance" with these standards.--source: Environmental Resource Guide-Air Quality
The Air Monitoring Section maintains a network of six air monitoring stations. These are: Barstow,Hesperia, Phelan,Trona, Twenty-nine Palms and Victorville.
Additionally. The Mojave Desert AQMD is contracted to the Antelope Valley AQMD to maintain an air monitoring station.
Our air quality is monitored continuously, 24 hours a day, seven days a week. This data is made available to the public via this web site on a near real time basis.
After validation, this data becomes part of a national air quality database that is maintained by the Environmental Protection Agency.
In addition to regular continuing maintenance of this network,calibrations are performed on a regularly scheduled basis in order to insure that all gaseous air monitoring instruments report data with no more than 5 percent error.
In addition to monitoring gaseous pollutants in the air, the MDAQMD also monitors the presence of microscopic solids that are suspended in the lower atmosphere. The presence of soot, ash or dust can have an effect on human health and produce haze that and may significantly reduce visibility. In the case of blowing dust or sand, "fugitive" particulate matter can damage property as well.
Particulate matter, or "PM" is divided into three classes based on size, ranging from PM-10, particles less than 10 microns in diameter to PM-2.5, or particles less then 2.5 microns in diameter. Generally, exposure to the smallest of particles has the greater effect on health and can have a significant effect on persons who have have respiratory problems. The third category encompasses the two, and is known as "TSP" or total suspended particulates.
Until only recently, the real time collection and quantative reporting of these substances were not possible. One such instrument, the "TEOM", uses a tapered element oscillating microbalance, a patented technique that makes it possible to measure particle mass collected on a filter in real time. In simplified terms, a clean filter resting atop a tapered element is made to oscillate during calibration and a resonant frequency is then calculated . The amount of drift from this frequency in normal operation due to mass accretion on the filter translates into quantative measure of particulate matter over time.
The MDAQMD has three of these instruments in operation. They are located in Victorville, Trona, and Lancaster. This data is reported on an hourly basis through the MDAQMD data acquisition network and can be found on this web site.
Sampling for particulates is also done using the Andersen PM10 monitor. On a six day scheduled cycle, this instrument draws a volume of air through a 8 X 10 inch filter over a twenty-four hour period.
The Air Monitoring Section maintains seven of these instruments. They are located in Victorville, Barstow, Hesperia, Twenty-nine Palms, Trona, Lucerne Valley and Lancaster. The Mojave Desert AQMD is contracted to the Antelope Valley AQMD to maintain the monitor in that location.
PM2.5 Sampling and The Lab
The focus of sampling the air for smaller particulates has become sharper in the last few years because of the impact that is has on public health. With the implementation of PM2.5 program, and certain requirements for the expeditious handling of these filters, the MDAQMD made the decision to incorporate a filter weighing laboratory into the building plan at the new district office building in Victorville.
This Laboratory provides the required temperature and humidity controlled environment for the filter weighing process. The MDAQMD is one of a handful of agencies that maintains such a "lab" and has been contracted by several other entities to service their needs as well. The PM 10 program benefits from this also inasmuch as these larger filters no longer need to be sent out but can now be weighed locally.
The Andersen RAAS PM2.5 sampler uses a circular 49mm diameter filter. This instrument has a carousel that can be loaded with several filters to be sampled in turn over a number of days. The cabinet provides a protected environment for the filters until they are retrieved by the technician.
These filters are weighed in the laboratory at the MDAQMD's main office in Victorville.Total weights are recorded from both PM10 and PM2.5 filter weighing operations and this data, after verification, becomes part of the EPA database.
PM2.5 filters are kept in cold storage after sampling and weighing in order that the various sample constituents be analyzed should the need arise.
Currently the MDAQMD operates and maintains three Andersen Sequential samplers. Two are located at the Victorville station and third is located at the Lancaster station at the Antelope Valley Air Quality Management District office.
IT'S ALL ABOUT THE DATA
An immense amount of meteorological data has been collected since the first weather observation was made. Atmospheric data is constantly being collected by governments and their agencies as well as private concerns around the world. Certainly everyone is aware of the hazards present in severe weather and in many cases the rapid public dissemination of such information in the form of a "Weather Warning" can be a matter of life and death.
Because of an increasing interest in the state of our environment and the quality of our air, the science of data collection and the disposition of such data has been redefined in the few past years. While the effects of air pollution may not be as immediately spectacular as a tornado, or hurricane, the long term effects on populations, and certain more sensitive segments of those populations, can nonetheless be hazardous to health and well being.
Whereas weather data has traditionally been gathered by human observers, the quality of our air by its very nature, must be determined by instrumentation. Prior to the year 2000, air quality data, once gathered, was and still is assessed for its accuracy and submitted to the EPA to be stored in a database. This data is used to to fuel studies to determine how the movement of the atmosphere affects the properties of various pollutant gases, and in turn, what the effect these gases might have on the population as a whole. A new discipline, defined as "modeling" has grown out of this; scientists, armed with computers and sophisticated software attempt to create a vision of how our atmosphere might be transformed in the future.
Since the year 2000, air quality data has become available to the public in a near real time sense. Informing people as to how atmospherics and air pollution might affect every day activities has become a priority with the Environmental Protection Agency. Heretofore, the lack of truly reliable instrumentation and the lack of a communications conduit, has made outreach to the public nearly impossible. Technological advances however, have made instrumentation more reliable and the Internet has provided a practical means to transmit data from remote locations on an hourly basis to a central location for distribution.
Meteorologists and Modelers now have immediate data at their disposal and this facilitates the generation of more accurate and timely air quality forecasts. The EPA's AirNow web site gives the public a wide selection of air quality data products.
The Mojave Desert Air Quality Management District has been on the cutting edge of software development that facilitates hourly data collection and enables the district to participate in the "Ozone Mapping" program. This program illustrates near real time ozone data in a graphical format from air quality districts nation wide. Because the software that is necessary for the implementation of these continuously evolving programs is created locally, we are able to keep pace with new requirements cost effectively and to be innovative as well.
Our public outreach efforts have become more effective and data collection has become more reliable. The media has expressed a continuing interest in including air quality data and forecasts along with their regularly scheduled weather forecasts.
Links to to the EPA web site and the Ozone Mapping presentations can be found elsewhere on this web site.