贵州百花湖水中溶解有机质的分子量分布随深度的变化规律

利用高效体积排阻色谱法测量了百花湖水中溶解有机质的分子量及其分布。结果表明百花湖水中溶解有机质（DOM）主要以分子量小于3500道尔顿（Da）的组分为主,其中重均（Mw）和数均（Mn）分子量分别界于2300～2500 Da和1900～2150 Da之间,说明其主要来源于降水对土壤有机物的淋滤和径流作用。根据色谱分析的结果,可以把溶解有机质的分子量分布分为四个组分：大分子量组分（MW〉3500 Da）;中等偏大分子量组分（3500～2000 Da）;中等分子量组分（2000～1000 Da）和小分子量组分（MW〈1000 Da）。由于生物活动和光降解作用以及有机物的分解作用,导致各分子量组分随深度的变化规律不同,其中分子量在3500～2000 Da之间的有机物的含量随深度的增大而增大,其余组分的含量随深度的增大而减少。计算所得的溶解有机质的Mw和Mn在表层较小,在中部随深度基本保持不变,到底部又变大。这种变化趋势与分子量组分的变化结果一致。

Changes in Molecular Weight Distribution of Dissolved Organic Matter with Depth in Lake Baihua

High - performance size exclusion chromatography （HPSEC） was used to determine the molecular weight distribution of dissolved organic matter （DOM） in Lake Baihua. The results showed that major DOM was smaller than molecular weight 3 500 Da, Mw and Mn ranged from 2 300 to 2 500 Da and from 1 900 to 2 150 Da, respectively, This may indicate soil organic matter was the DOM main source. The molecular weight distribution was divided into four fractions ：large （ MW 〉 3 500 Da）, medium -large （3 500 -2 000 Da）, medium （2 000 - 1 000 Da） and small fraction （MW 〈 1 000 Da）. DOM proportion with different molecular weight varied with water depth, indicating the influence of photo - and micro - degradation and decomposition. The percent of medium - large fraction increased with depth, and other fractions decreased slightly, The estimated number - and weight - averaged molecular weight was small in surface water and kept constantly in middle of water, and in bottom water reached largest values.