Air quality is monitored continuously at GLEES. Air pollutants are considered an important component of the atmosphere that can have an effect on terrestrial and aquatic ecosystems. Atmospheric deposition of gases, wet deposition of chemicals in precipitation including snow and rain, and dry deposition of chemicals are all monitored at GLEES. Although GLEES is a relatively remote and unpolluted site, deposition of pollutants can be important. The effects of ozone on native vegetation in alpine and subalpine ecosystems is generally unknown, but relatively high concentrations of ozone have been recorded at GLEES. Wet and dry deposition is important in snowmelt chemistry and subsequent input to aquatic ecosystems at GLEES.