ANALYSIS OF GASEOUS-HYDROGEN PEROXIDE CONCENTRATIONS IN RALEIGH, NORTH-CAROLINA

Gas-phase total peroxides and hydrogen peroxide (H2O2) were monitored in the ambient air in downtown Raleigh, North Carolina as part of the Southern Oxidant Study-Southern Oxidants Research Programs on Ozone No n-Attainment (SOS-SORP/ONA). These measurements were made during Septe mber 8-16, 1991, using the continuous dual-channel fluorometric analyz er based on the horseradish peroxidase method. Measurements were also made of other photochemical oxidants and trace gases (O3, NO, NO2, NO( x), SO2, CO, HCHO) and meteorological parameters. Concentrations of H2 O2 showed a diurnal variation with maximum concentrations in the after noon (1400-1800) EST. The mean of all observations was 0.2 ppbv and th e range measured was below the level of detection (approximately 0.05 ppbv) to about 1 ppbv. An observational-based statistical analysis uti lizing Multivariate Principal Component Analysis (PCA) was applied to the data to determine the underlying processes. Four physicochemical c omponents were found to account for approximately 86 percent of the va riability of all the parameters. Application of Kaiser's Varimax ortho gonal rotation on the four retained principal components allowed in th e physical interpretation of the first four Principal Components as be ing: photochemical processes, primary pollutant concentrations, emissi on and transport Of SO2, and air mass type. A multiple linear regressi on analysis was carried out by regressing H2O2 on all the other physic ochemical air quality variables and/ora combination of these. It was f ound that all the variables put together account for 53 percent of the variability in H2O2 concentrations. Ozone alone accounts for 11 perce nt of the variability, and this value increased to 33 percent when tem perature, relative humidity and solar radiation were added to ozone. P CA was applied again to the data set (excluding H2O2) and the principa l components obtained were used as independent variables for the regre ssion analysis of H2O2. It was found that photochemical activity and p rimary pollutant concentrations were the most significant factors in c ontrolling gaseous H2O2 concentrations in Raleigh during the measureme nt period.