Frontal affinity chromatography was applied to characterizing the mechanism of binding of silver with sediment particulates collected from Lake Ontario, Canada. The results showed that there was one major binding site for Ag+ in the particulates. The binding capacity ranges from 6.06 to 1.01 μ·mol·g-1, and the binding constant (lgK) from 6.23 to 7.43 M-1 in 0.005 M ion strength at pH=3-7. The binding capacity and affinity constant were found to be pH-dependent. It is suggested that the particulate surface site where silver was bound was the anionic base. This study would be helpful for better understanding of the fundamental environmental chemistry of silver in sediments.
Strong interaction between natural dissolved organic matter (DOM) and Hg(Ⅱ) may influence the trans- port, conversion, toxicity and bio-validity of mercury in the environment. In this paper ultraviolet (UV) absorbance titration was employed for the first time for the determination of the conditional stability constants of Hg(Ⅱ) and (DOM). With increasing Hg(Ⅱ) concentrations, the UV absorbance of fulvic acid, humic acid, and DOM in river increases progressively. By linear and non-linear model fitting, the conditional stability constants (lgK) of Hg(Ⅱ) and DOM were worked out to be 3.54?4.93 and 3.64?4.85, respectively. The results are consistent with those acquired by the typical fluorescence quenching titration method, with the maximum relative error of lgK being 2.6% and the average relative error being 0.2%. The UV absorbance titration method has the advantages of rapid determination, simple performance, and it will probably become a new approach to studying interactions between DOM and trace metallic ions.
BAI YingchenWU FengchangWAN GuojingLIU CongqiangFU PingqingLI Wen
Dissolved organic matter (DOM) is one of the most interesting and difficult problems in recent years due to its important functions in the ecological and environmental system and the complexity of its chemical composition and structure. It is well ac- cepted that fluorescence characteristics and mo- lecular weight distribution are two important pa- rameters in the DOM characterization. However, the relationship between them is still unknown. In this study, fluorescence and molecular weight distribution of DOM in Lake Hongfeng, Lake Baihua and their rivers, and their relationship were investigated using the combination of fluorescence spectroscopy and high-performance size exclusion chromatography (HPSEC) with on-line UV absorbance and fluores- cence detectors. The results show that there were two obvious humic-like fluorescence peaks (Peaks A and B) in DOM from lake water. But there was an- other obvious protein-like fluorescence peak (Peak C) in DOM from river water. The humic-like fluorescence material consisted of DOM fraction with smaller mo- lecular weight, ranging from 1.0 to 3.0 kDa, while the protein-like fluorescence material mainly consisted of DOM fraction with MW larger than 2.0 kDa. The cal- culation of MW using HPSEC was related to the UV absorbance wavelength chosen.
