Study of the interactions between zinc ion and dissolved organic matter by using in situ methods of absorbance

The bioavailability and toxicity of zinc to aquatic life depends on dissolved organic matter (such as Suwannee River Fulvic Acid) ,which plays important role in the speciation of zinc.This study examined reactions of SRFA with... [ view full abstract ]

The bioavailability and toxicity of zinc to aquatic life depends on dissolved organic matter (such as Suwannee River Fulvic Acid) ,which plays important role in the speciation of zinc.This study examined reactions of SRFA with varying zinc concentration at pHs from 3.0 to 9.0, as well as competitive binding of Calcium/Magnesium and zinc to SRFA at pH 6.0 by using in situ methods of absorbance. Interactions of Zn2+ with SRFA chromophores were accompanied by the emergence of features in Zn-differential spectra, Among all of Zn2+-SRFA systems, the dominant peaks were located at 230 nm, 270 nm, 320 nm, 375 nm, the highest intensity of them was located at 230 nm, the observed results indicated the occurrence of the replacement of a characteristic number of protons by the bound Zn2+ . The extent of Zn2+ binding with SRFA could be quantified by calculating the changes of the slopes of Zn-differential log-transformed absorbance in the range of wavelength 350 to 400 nm (denoted as DS350-400) and by comparing the data with predictions made using the Non-ideal Competitive Adsorption (NICA-Donnan) model, the result showed DS350-400 were well correlated to the bound Zn2+ concentrations predicted by NICA-Donnan model with or without Ca2+ or Mg2+.Ca2+ and Mg2+ only effect intensity of the Zn-differential and Zn-differential log-transformed absorbance rather than shape.In situ methods of absorbance can be used to gain more information about Men+-DOM interactions in the presence of varying metals.