LONG-TERM DAILY MEAN MIXING RATIOS OF O-3, PAN, HNO3, AND PARTICLE NITRATE AT A RURAL LOCATION IN EASTERN CANADA - RELATIONSHIPS AND IMPLIED OZONE PRODUCTION EFFICIENCY

Temporal trends (long term, annual, and daily) for concurrent observat ions of O-3, PAN, HNO3, and pNO(3)(-) (particle nitrate) are derived. Correlations between these compounds and the meteorological parameters temperature and precipitation are outlined using a partial correlatio n analysis and a principal component analysis. Long-term trends are ob served for the nitrogen oxides that do not appear to be due to eastern North American sources. No long-term trend in O-3 is found, and a dec rease in the efficiency of its production as function of nitrogen oxid e abundance is indicated which may be caused by a decrease in the leve ls of hydrocarbons. Annual cycles of O-3 and PAN show similarity with a spring peak and a summer minimum. These compounds are positively cor related at all times but especially so in the spring, independent of t he annual cycle, and it is inferred that a common mechanism drives the spring maximum. HNO3 and pNO(3)(-) do not show a similar spring maxim um: HNO3 maximizes in the summer and pNO(3)(-) in the winter. On a day -to-day basis, PAN and O-3 show almost identical autocorrelation which is greater than that for HNO3 and pNO(3)(-), probably due to the vari ance introduced by precipitation scavenging of the latter. HNO3 and te mperature correlate negative in the winter and positive in the summer with O-3 reflecting the different production mechanisms of HNO3. Posit ive correlation between HNO3 and PAN is seen suggesting that part of t heir variance is due to their common precursor NOx, while the negative correlation between PAN and temperature is probably reflecting the th ermal instability of PAN. The results are used to infer the seasonal v ariation in the O-3 production efficiency as a function of nitrogen ox ide abundance. A slight negative value is derived for the winter, and only during the period May to August is O-3 expected to be produced ef ficiently.