You are here:
RESPONSE OF LEAD SOLUBILITY TO DISSOLVED CARBONATE IN DRINKING WATER
Citation:
Schock, M. RESPONSE OF LEAD SOLUBILITY TO DISSOLVED CARBONATE IN DRINKING WATER. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-80/294 (NTIS PB81222713).
Description:
A model is presented showing the detailed response of the theoretical solubility curves for lead to changes in dissolved inorganic carbonate concentration (TIC) and pH at 25 C. Aqueous Pb(II) ion, lead carbonate complexes, lead hydroxide monomers and polymers, and the solids lead hydroxide, cerussite and hydrocerussite were considered. Results of pipe loop solubility experiments at log TIC(mol/L) values of -3.6, -3.0 and -2.7 (25, 100 and 200 mg/L as CaC03) are presented. The model agrees very well with these data, as well as with previously published pipe coupon tests and precipitation data at high TIC. The predicted minimum molar solubility of lead is shown to increase by a factor of approximately 2 to 10,000 over that predicted by previous two-solid phase models that ignored lead carbonate complexes. Further, a general reversal in trend occurs with increasing TIC and curve shapes are greatly changed in contrast with those previous models. Reduction of lead levels to below 0.05 mg/L in standing samples purely by hydroxide and carbonate solubility considerations is possible, but only under very restricted pH and TIC conditions.