Research Projects

This report describes determinations of concentrations of gaseous and particulate air pollutants in open-top field chambers used for exposing of tree seedlings to acidic rain and ozone. The study was performed at the Chico Tree improvement Facility, Chico, California in summer 1992. Measurements were performed in standard chambers used for air pollution exposures. During the study, air pollution concentrations were measured in the following types of chambers: charcoal-filtered (control); ambient air with ambient ozone concentrations: ambient air with double ambient ozone concentrations. In addition, measurements were also performed in outside, chamberless plots. Concentrations of gaseous nitric acid, gaseous nitrous acid, ammonia, sulfur dioxide and nitrate, ammonium and sulfate in fine and coarse particulate fractions were determined. Increased concentrations of nitric acid were detected in chambers due to the generation of ozone, however, these concentrations were lower than the ambient concentrations measured in outside plots. Elevated concentrations of nitrous acid were detected in the charcoal-filtered chambers. Nitrous acid was probably produced during the heterogeneous reactions of NO and NO, including hydrolysis of NO, occurring on charcoal fitters. Concentrations of nitric acid and nitrous acid determined in this study are compared to concentrations from other locations in North America and Europe.