Time Trends and Seasonal Variation of the Rainwater Chemical Composition in Spain

Abstract

A multiple regression model was used to describe temporal variations of the concentrations of H+, SO4 2 -, NO3 - and NH4 + in Spanish rainwater. The model included the effects of linear trend, annual cycle, and precipitation quantity simultaneously. The model fit very well for SO4 2 - and NO3 -, with statistical evidence of annual cycle and effect of precipitation quantity for these two ions and for NH4 +, but not for H+. There is no trend for any ion, with the single exception of a decreasing trend for H+ in one of the stations used