Copper binding by dissolved organic matter: II. Variation in type and source of organic matter

Copper binding properties of several fulvic acid (FA) and whole water samples are compared by means of an empirical model that was calibrated using Suwannee River FA. Within the calibration limits of the model (pH 5.0–8.5, total Cu concentration 0.1–100 μM, ionic strength 0.1, and dissolved organic carbon, DOC, 1–10 mg C/1), ρCu in solutions of a variety of FA samples are predicted with < 0.2 ρCu units root mean square error (RMSE). Within the calibration limits, many whole water sample ρCu's are predicted with <0.3 ρCu units RMSE if only one-half of the dissolved organic carbon is assumed to bind Cu. Agreement between prediction and experiment at lower ionic strength is not as good. Variations in Cu binding among different sources of dissolved organic matter appear to be much smaller than those due to chemical factors such as pH and ionic strength.