Watershed buffering: carbonate buffering Caco,+h,CO=Ca+2HCO H,C0=H*+HCO% Kegs iCa IHCO, l-=lot Ka=lH jAco 6.4 [ CO3 [H2CO3I H2CO3]=10M PH=pKa-log lH, co31 HCO3 I 2[Ca]=[HCO3 6.40+197=8.37 [BCO3]=10 That's how underground caves are formed Acidic rainwater can be neutralized by exposure to calcareous soils, with a concomitant significant increase in the concentration of calcium ion in solutionWatershed buffering: carbonate buffering HCO M Ca HCO H CO M H CO Ca HCO Keq CaCO H CO Ca HCO 3.0 0 3 3 2 4.9 2 3 4.4 1 2 3 2 3 2 3 2 3 2 3 [ ] 10 2[ ] [ ] [ ] 10 10 [ ] [ ][ ] 2 − − + − − − + − + − = = = = = + = + 6.40 1.97 8.37 [ ] [ ] log 10 3 2 3 6.4 [ ] [ ][ ] 2 3 3 2 3 3 = + = = − = = = + − − + − + − HCO H CO pH pKa Ka H CO H HCO H CO H HCO Acidic rainwater can be neutralized by exposure to calcareous soils, with a concomitant significant increase in the concentration of calcium ion in solution. That’s how underground caves are formed