Liao Haiqing

Characterization of dissolved organic matter fractions from Lake Hongfeng, Southwestern China Plateau.

With XAD-series and ion exchange resins, dissolved organic matter (DOM) from Lake Hongfeng in Southwestern China Plateau was isolated into 6 fractions, i.e., humic acid (HA), fulvic acid (FA), hydrophobic neutrals (HON), hydrophilic acids (HIA), hydrophilic bases (HIB) and hydrophilic neutrals (HIN). Those fractions were characterized by high performance size exclusion chromatography, fluorescence spectroscopy and UV absorbance. Among the 6 fractions, FA was predominant and accounted for 51% of the total DOM. The weight-average (Mw) and number-averaged (Mn) molecular weight of these fractions ranged from 1688 to 2355 Da and from 1338 to 1928 Da, respectively. A strong correlation was observed between specific UV absorbance at 280 nm, E2/E3 (absorbance at 250 nm to 365 nm), and the molecular weight for DOM fractions. UV-Vis fulvic-like fluorescence peaks were found in all fractions. Protein-like fluorescence peaks existed in HON may indicate that microbial activity was severely in Lake Hongfeng. There was a significant relationship between fluorescence intensities and specific UV absorbance at 254 nm for those DOM fractions, suggesting their similar luminescence characteristics. The values of fluorescence index (f450/500) indicated that hydrophobic fractions may derive from terrestrial sources, and the hydrophilic fractions from microbial and terrestrial origins. Those results suggest that there were inter-relationships between molecular weight, fluorescence and absorbance characteristics, and also subtle consistencies between the hydrophilic and hydrophobic properties and the sources for these 6 fractions from Lake Hongfeng.

Natural organic matter and its significance in terrestrial surface environment

Natural organic matter is an important component in terrestrial surface environment. More and more researches indicated that it plays an important role in physical, chemical and biological processes of terrestrial ecosystem; it is the important cycling routes of matter and energy and relates with nearly all the important links of ecosystem. Natural organic matter is not only the important study field of biogeochemistry, ecology and environment sciences, but also a basic theoretical area in the assessment, prediction and control of environment pollution. Natural organic matter now becomes the focus of environment quality, toxicology, environment law and management. Using fresh lake and river as examples, this article briefly summarizes the study results of sources, chemical structure, cycling characteristics, coupling relations with nutrients cycling, and its effects on mobility and transformation of toxic metals and organic pollutants, and expounds the possible right research directions and contents referring to water eutrophication and environment pollution. This article also makes a prospect about modern organic environment and biogeochemistry.