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Environmental Factors that Affect Nylon and Teflon Filters used in Air Pollution Monitoring
Pamela Padgett
Atmospheric Deposition Unit, USDA Forest Service, Pacific Southwest Research
Riverside Fire Lab, 4955 Canyon Crest Dr, Riverside CA, 92507
| Two proprietary filter media, Teflon (PTFE, PolyTetraFluoroEthylene)
and Nylasorb (nylon) are used by both long term national monitoring networks
and short term research-oriented monitoring projects. They are used in
active monitoring systems such as the filter packs in the CASTNET program
and in annular and honeycomb denuders, as well as passive monitoring systems
used by many researchers and land managers. Both chemical and physical
properties of the filters are engaged in trapping particulates and gasses.
A series of experiments were conducted to evaluate the effects of ozone,
relative humidity, and exposure time on the stability and reproducibility
of these pollutant trapping materials. Variability in extract concentrations
for NO3 - NH4 + and SO4 -2 within each experiment was <5% for all experiments,
and little particulate decomposition was observed with extended operation
and exposure. The presence of elevated ozone did, however, have a significant
effect on capture or retention of HNO3 on Nylasorb filters; the greater
the ozone concentration, the lower the extractable NO3 -. The effects
of relative humidity were complicated by several other environmental factors,
which will be highlighted in the presentation.
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