ESTIMATING PRIMARY AND SECONDARY PRODUCTION OF HCHO IN EASTERN NORTH-AMERICA BASED ON GAS-PHASE MEASUREMENTS AND PRINCIPAL COMPONENT ANALYSIS

Based on atmospheric measurements of multiple species at Egbert, a rur al site in Ontario, Canada, during summer 1988, the emission ratios of HCHO/CO and HCHO/SIGMANO(y) for area sources and secondary production of HCHO have been estimated using a modified principal component anal ysis technique. The technique yields three principal components that r epresent a photochemically aged air mass, a diurnal cycle, and fresh a rea emissions. The area emission component has an emission ratio CO/SI GMANO(y) = 9 +/- 3 and SO2/CO = 0.005 +/- 0.003, in agreement with NAP AP area emission data for the eastern US [Buhr et al., 1992]. The emis sion ratios of HCHO/CO and HCHO/SIGMANO(y) in this component are 0.005 6 +/- 0.0022 and 0.05 +/- 0.007, respectively. If these ratios are typ ical of eastern North American area emissions, the total primary HCHO emission for this region will be 8 x 10(9) moles HCHO annually based o n the NAPAP CO emission inventories. Evidence of secondary HCHO produc tion can be found in the photochemically aged component which has cons iderably higher HCHO/CO (0.016 +/- 0.004) and HCHO/SIGMANO(y) (0.29 +/ - 0.03) ratios than the emission ratios. It is estimated that for ever y 1 ppb NO(x) converted to NO(y), 0.4 ppb HCHO are produced for the ra tio (1-NO(x)/NO(y))<0.6; after which the relative HCHO production rate becomes smaller. Using this relative rate, the maximum total HCHO pro duction over the eastern North America is estimated to be 1.3 x 10(11) moles year-1, or approximately 16 times that from primary emission.