ABSTRACT
Rainwater is the source of most groundwater and a logical starting point for the study of groundwater geochemistry. Continental rainwater is dominated by oceanic vapor and it does indeed resemble strongly diluted seawater. However, natural and anthropogenic dusts and gases modify the composition. Before the rain turns into groundwater, various processes in the soil may affect the concentrations. Dry-deposited dust particles and gases will dissolve. Evapotranspiration concentrates the solutes, and vegetation selects essential elements to store them temporarily in the biomass. Particularly the weathering of minerals in the soil is of importance in changing concentrations, and all the soil processes together often generate already much of the groundwater chemistry. In this chapter, we will follow the evolution in water chemistry from rain, via soil, to the aquifer.
