Clean Air Status and Trends Network (CASTNET) - Beltsville, United States Environmental Protection Agency
NAL Geospatial Catalog
CASTNET measures ambient concentrations of sulfur and nitrogen species as well as rural ozone concentrations. The network includes 90 sites located throughout the US and Canada. Each site measures weekly concentrations of acidic pollutants, base cations and Cl- using a 3-stage filter pack with a controlled flow rate. Most CASTNET sites also include a temperature controlled shelter and continuous ozone monitoring system.