PPT Slide
Groundwater in calcareous soils carries high loads of dissolved Ca(HCO3)2 and other carbonates.
CaCO3+CO2+HOH<=>Ca(HCO3)2+[CO2]equil 2<=> Ca++ + 2 HCO3- +[CO2]equil 2
- Respiring soil bacteria provide water percolating through the soil a supersaturated CO2 environment. The resulting carbonic acid promotes the dissolution of calcite-bearing material in the soil.
- When ground water super-saturated with CO2 aand with Ca(HCO3)2 enter surface water systems (e.g. stream channels), Henry’s Law reasserts itself. CO2 is lost to the atmosphere, and calcite (CaCO3) is precipitated.
- Spring inlets on stream channels are often marked by white-grey deposits of marl because of this re-equilibration of CO2 content- a fact useful in locating groundwater sources in stream ecology