A statistical assessment of changes in precipitation chemistry at CAPMoN sites, Canada. Canadian Air and Precipitation Monitoring Network.

The objective of this study is to decide if chemical concentrations measured during 1988-1997 in precipitation by the Canadian Air and Precipitation Monitoring Network (CAPMoN) indicate changes in the annual patterns. The inference is based on SO4, NO3, Cl, NH4, Na, Ca and K concentrations monitored daily with the rain water acidity pH. By pattern is understood the probability distribution of the annual sample at a particular location. Most of the annual data can be well described by means of a linear regression model with second order polynomial trend and autocorrelated noise. Statistical analysis based on the model shows luck of systematic significant year to year increases or declines of the concentrations.