Estimate pe for the aquatic systems characterized by the following information: i) Water from deeper layers of a lake having [O2(aq)] = 0.02 mg/L and a pH of 7.0. ii) An anaerobic digester in which 60% CH.(g) and 40% CO2(g) are in contact with water of pH 7.0. i) reasonable to set PH2S between 10 and 10 atm. A water sample of pH = 6.0 containing [SO.] = 10 M and smelling of H2S(g). It is