The predominant ion below pH 6.9 is Cu” llVh1l€ Cu(OH) is the major solution species above this pH. The
hydrolysis Species Cu()H+ becomes slightly significant near pH 7 whereas
Cu(0H) ? Cu(OH)i`, and Cu2(()H)+ are insignificant in soils.
Several Cuz* complexes are given by Reactions 21 through 35 of Table
14.1. The pyrophosphate complexes were considered in the previous section
and the remainder of these complexes are shown in Fig. 14.6 in equilibrium
with soil-Cu.
The complexes of great importance in soils are CuSOf’, and CuCO.
At 1O'2?36 M so;-, CuSO and Cuz* activities are equal, and CuSO2
changes 10-fold for each 10-fold change in S021 At 1O“2?35 atm of CO2
the activities of CuCO and Cu(OH) are equal. Tenfold changes in CO2
' h lexes that may contribute more than
change CuCO3 accordingly.