Summer-time distribution of air pollutants in Sequoia National Park, california

Concentrations of air pollutants were monitored during the May-November 1999 period on a network of forested sites in Sequoia National Park, California. Measurements were conducted with: (1) active monitors for nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O-3); (2) honeycomb denuder/filter pack systems for nitric acid vapor (HNO3), nitrous acid vapor (HNO2), ammonia (NH3), sulfur dioxide (SO2), particulate nitrate (NO3-), ammonium (NH4+), and sulfate (SO42-), and (3) passive samplers for O-3, HNO3 and NO2. Elevated concentrations of O-3 (seasonal means 41-71 ppb), HNO3 (seasonal means 0.4-2.9 mug/ml), NH3 (seasonal means 1.6-4.5 mug/m(3)), NO3- (1.1-2.0 mug/m(3)) and NH4+ (1.0-1.9 mug/m(3)) were determined. Concentrations of other pollutants were low. With increasing elevation and distance from the pollution source area of O-3, NH3 and HNO3 concentrations decreased. Ammonia and NH4+ were dominant N pollutants indicating strong influence of agricultural emissions on forests and other ecosystems of the Sequoia National Park. Published by Elsevier Science Ltd.