CHANGES IN INORGANIC CARBON-CHEMISTRY AND DEPOSITION OF ONONDAGA LAKE, NEW-YORK

Changes in Ca2+, alkalinity, dissolved inorganic carbon (DIC) and pH h ave occurred in the epilimnion of Onondaga Lake over a 10-yr period, i n 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 p H values. Results of analyses from sediment trap collections before an d after closure of the facility indicate approximately 3-fold reductio ns in particulate inorganic carbon (PIC), and suspended solids deposit ion have occurred as a result of the closure. Despite these changes, t he water column remains oversaturated with respect to the solubility o f CaCO3. Moreover, there was no apparent relationship between the degr ee of CaCO3 saturation and PIC deposition. Changes in the extent of Ca CO3 precipitation have altered the acid-base chemistry of the lake whi ch, in turn, affects prevailing pollution problems associated with inp uts of domestic waste, such as NH3 toxicity.