[Combining ultrafiltration, fluorescence spectroscopy and HPSEC to characterize dissolved organic matter in surface...

The combination of ultrafiltration, three-dimensional excitation/emission matrix (3DEEM) fluorescence spectroscopy and high-performance size-exclusion chromatography (HPSEC) was used to characterize the molecular weight distribution properties of different fluorescence materials, further revealing the differences in the sources and components. Dissolved organic matter (DOM) from different lakes fractionated by ultrafiltration with a nominal 1,000 molecular weight cut-off regenerated cellulose membrane, then 3DEEM spectrophotometry and HPSEC were applied to investigate the characteristics of high molecular weight materials in retentate and low molecular weight materials in permeate. The result indicated that the flulvic acid-like (Ex/Em approximately equal to 260 nm/450 nm of peak A and Ex/Em approximately equal to 320 nm/439 nm of peak C) and protein-like (Ex/Em approximately equal to 275 nm/312 nm of peak B and Ex/Em approximately equal to 220 nm/308 nm of peak D) fluorophores in permeate were detected after ultrafiltration which is covered by high absorbing peak of humic-like (Ex/Em approximately equal to 360 nm/462 nm of peak E) fluorescence fluorophores in the original Shennonajia bog water, Hubei province. They permeated the membrane because of their low molecular weight distribution properties. The content of autochthonous protein-like (Ex/Em approximately equal to 280 nm/334 nm of peak B and Ex/Em approximately equal to 225 nm/328 nm of peak D) component was too low to be measured by high-sensitivity fluorescence spectrophotometer in the original water of Lake Hongfeng, Guizhou province. But they can be concentrated attribute to their high molecular weight distribution properties. The 3DEEM fluorescence spectroscopy of retentate exhibited evident protein-like fluorophores. Moreover, there had obviously difference in molecular weight between different sources of fulvic acid-like and protein-like components. It has been shown that the molecular weight distribution of autochthonous protein-like matter in Hongfeng lake is larger than allochthonous protein-like matter in Aha lake, Guizhou province. One was retained by membrane and another was permeated. Therefore, these techniques together will offer direct and convenient qualitative information about DOM in lake waters.