AIRNET Program Description

AIRNET is a network of more than 50 environmental air stations that sample radionuclides in ambient air. To learn more about the program, select a topic from the drop-down list below.

Analytical Chemistry

Individual particulate filters (typically half filters) are sent to a commercial laboratory for analysis. The filters are dissolved and counted for gross alpha and beta radioactivity with a gas-flow proportional counter, meeting the requirements of 40 CFR 61, Appendix B, Method 114. A composite is prepared quarterly for each station by combining the other half filters from the six or seven sampling periods during the quarter. The composites (one for each station) are submitted to commercial laboratories for analysis. At these laboratories, chemical analyses consist of complex radiochemical separations followed by alpha spectroscopy (radioactive isotopes) or inductively coupled plasma emission spectroscopy (non-radioactive elements), which conform to EPA requirements. The analyses and instruments are listed in the table below.

Every two weeks, WES-DO staff distill the moisture from the silica gel cartridges and submit the distillate to the analytical laboratory for tritium determination by liquid scintillation counting.

Required detection limits, called minimum detectable amounts (MDAs), for analyses were established by application of the EPA data quality objective process. These MDAs were defined, in a manner consistent with EPA guidelines, as functions of the standard deviations (sigma) of background count rates for radioactive isotopes or the standard deviation among multiple determinations of background signal for non-radioactive elements. Target MDAs (as 3 sigma values) are as follows.

Analytical Chemistry Requirements for Ambient Air Samples

• Note: MDA = Minimum Detectable Amounts

Calculation of Air Concentrations

Final concentrations of airborne materials are normally reported in units of weight/volume or activity/volume (e.g. picograms/cubic meter or picoCuries/cubic meter). Absolute humidity is measured by the LANL meteorological tower network and reported in grams/cubic meter. The following formulae, along with the measurement data from the individual sites, are used to calculate the air concentrations reported for each sample:

• Particulate filters: [(Result)/(Fraction analyzed)]/(air volume)
• Tritium cartridges: [(Result)*(absolute humidity)]

Sampling Procedures

Each AIRNET sampler is equipped with a filter to collect a particulate matter sample (for gross alpha/beta and radiochemical determinations) and a silica gel cartridge to collect a water sample (for tritium determination).

A pump pulls ambient air into the housing that protects the sampling apparatus and through the filter and cartridge. Instrumentation within the housing records the total time the pump ran during the two-week sample period and the flow in the particle and the tritium sampling trains.

During a two week period, the filter will collect particulate material from approximately 2,280 m3 of air, and the silica gel cartridge will collect the moisture from approximately 4 m3 of air. The particulate filter and the gel cartridge are collected and analyzed biweekly. The particulate filters are accumulated for three months, composited, split, and then sent to commercial analytical laboratories for radiochemical analyses. Details about the sample collection, sample management, chemical analysis, and data management activities are provided in the Quality Assurance Project Plan (ENV-MAQ - AIRNET) and in the numerous procedures through which the plan is implemented.

AIRNET Environmental Air Monitoring Station

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