Transformations of Heavy Metals and Plant Nutrients in Dredged Sediments as Affected by Oxidation Reduction Potential and pH. Volume II. Materials and Methods/Results and Discussion.

摘要

A laboratory study was conducted to determine the effects of pH and oxidation-reduction conditions on the distribution of mercury,lead,cadmium,zinc,copper,manganese,iron,phosphorus,and ammonium-nitrogen among selected chemical forms in sediment-water systems from four (Gulf Coastal) sites. This study was designed to determine how changes in these physicochemical parameters,such as may occur during dredging and dredged material disposal,might affect the chemical availability of these nutrients and toxic substances and thus reflect possible changes in their bioavailability. Studies indicated the pH and redox potential influence the chemical form and distribution of the metals studied,although the response to changes in the physicochemical environment were frequently not the same for different metals. Results suggest that the pH and redox potential are important in regulating the chemical availability of a number of nutrients and potentially toxic trace metals. The metal regulatory processes involved included precipitation with sulfide,adsorption or coprecipitation with colloidal hydrous oxides,and complex formation with soluble and insoluble organics. In many cases,changes in acidity or oxidation-reduction conditions resulted in considerable transformations among potentially available forms.