Potential Complexing Ability of Surface Water Organic Matter: II. Toxicity of Metal-Containing Aquatic Environment

Abstract

The results of biotesting the toxicity of natural water from the upper section of the Kanev reservoir and Lake Verbnoe before and after addition of 500 μg/L Al(III), Fe(III), and Cu(II) using juveniles of Daphnia magna Straus are discussed. The toxicity of the aquatic environment was assumed to be determined by the presence therein of a labile fraction of metals, primarily Cu(II) as potentially bioavailable. The concentrations of Al_lab, Fe_lab, and Cu_lab in the original natural water from the Kanev reservoir and Lake Verbnoe were estimated at 20.0, 27.5, and 6.8 μg/L and 20.2, 68.7, and 11.2 μg/L, respectively. The metals under study and at such concentrations did not show acute toxicity for juveniles of Daphnia magna Straus. In natural water with metal additives, the concentrations of Al_lab, Fe_lab, and Cu_lab decreased from 500 μg/L at the beginning of the experiment to 138, 70, and 34 μg/L, respectively, on the 28th day of the experiment, which was reflected in the results of biotesting. In the control (purified tap water), the concentrations of Al_lab, Fe_lab, and Cu_lab by the end of the experiment were 98, 217, and 105 μg/L, respectively, and acute toxicity persisted throughout the experiment. Water from the Kanev reservoir and Lake Verbnoe no longer showed acute toxicity only after the 14th and 28th day, and the corresponding Cu_lab, Al_lab, and Fe_lab concentrations were 70 and 34 μg/L, 200 and 212 μg/L, and 114 and 70 μg/L. The acute toxicity of Cu(II) without addition of Al(III) and Fe(III) was observed at a concentration of 230 μg/L, whereas Cu(II) in combination with Al(III) and Fe(III) showed acute toxicity at a lower concentration (50 μg/L).