Changes in Inorganic Carbon Chemistry and Deposition of Onondaga Lake, New York

Changes in Ca²⁺, alkalinity, dissolved inorganic carbon (DIC) and pH have occurred in the epilimnion of Onondaga Lake over a 10-yr period, in response to a major reduction in external Ca²⁺ loading that resulted from the closure of an adjoining soda ash manufacturer. These changes included reduced Ca²⁺ concentrations, diminished depletion of DIC and alkalinity in the upper waters in the summer, and a shift to higher pH values. Results of analyses from sediment trap collections before and after closure of the facility indicate approximately 3-fold reductions in particulate inorganic carbon (PIC), and suspended solids deposition have occurred as a result of the closure. Despite these changes, the water column remains oversaturated with respect to the solubility of CaCO₃. Moreover, there was no apparent relationship between the degree of CaCO₃ saturation and PIC deposition. Changes in the extent of CaCO₃ precipitation have altered the acid-base chemistry of the lake which, in turn, affects prevailing pollution problems associated with inputs of domestic waste, such as NH₃ toxicity.