Analyses of the cycling process of the trace metals in lake water by chemical speciation

The chemical stability of large organic molecule-metal complexes(LOMMCs)dissolved in pond water were investigated by a hyphenated system of size exclusion chromatography/UV absorption detection/inductively coupled plasma mass spectrometry(SEC/UV/ICP-MS)after ultrafiltration using a filter with a molecular permeation limit larger than 10，000Da.LOMMCs dissolved in the preconcentrated pond water sample were observed at the retention times corresponding to molecular weights larger than 300，000Da(Peak I)and that of 10，000-50，000Da(Peak II)in the chromatograms measured by UV absorption and ICP-MS.When the pH of the sample solution.These results indicate that LOMMCs were decomposed by addition of HNO I D 23 D 2.Peak I was rapidly decomposed below pH4，while Peak II was gradually decomposed over the pH range from 7.0to0.5。The decomposition curve of Peak I was similar to the solubility characteristics of hydroxides of Fe and Al.On the other hand，that of Peak II suggested the dissociations of metal complexes(Cu And Zn)with some biogenic organic molecules。It was concluded from these results that some colloidal particles of hydroxides of Fe and Al may be core materials of LOMMCs for Peak I，while some metal complexes with biogenic protein-like compounds may be LOMMCs for Peak II.The possible models for LOMMCs in pond water were proposed as“a string-ball model”，which might interpret as the removal and preservation mechanisms for trace elements in natural water.

The chemical stability of large organic molecule-metal complexes (LOMMCs) dissolved in pond water were investigated by a hyphenated system of size exclusion chromatography/UV absorption detection/inductively coupled plasma mass spectrometry (SEC/UV/ICP-MS) after ultrafiltration using a filter with a molecular permeation limit larger than 10,000 Da. LOMMCs dissolved in the preconcentrated pond water sample were observed at the retention times corresponding to molecular weights larger than 300,000 Da (Peak I) and that of 10,000-50,000 Da (Peak II) in the chromatograms measured by UV absorption and ICP-MS. When the pH of the sample solution. These results indicate that LOMMCs were decomposed by addition of HNOィイD23ィエD2. Peak I was rapidly decomposed below pH4, while Peak II was gradually decomposed over the pH range from 7.0 to 0.5. The decomposition curve of Peak I was similar to the solubility characteristics of hydroxides of Fe and Al. On the other hand, that of Peak II suggested the dissociations of metal complexes (Cu and Zn) with some biogenic organic molecules. It was concluded from these results that some colloidal particles of hydroxides of Fe and Al may be core materials of LOMMCs for Peak I, while some metal complexes with biogenic protein-like compounds may be LOMMCs for Peak II. The possible models for LOMMCs in pond water were proposed as "a string-ball model", which might interpret as the removal and preservation mechanisms for trace elements in natural water.