滇池沉积物不同分子量溶解性有机质分布及其与Cu和Pb的相互作用

Distribution of Different Molecular Weight Fractions of Dissolved Organic Matters and Their Complexation with Cu and Pb in the Sediment from Dianchi Lake,China

采用平衡渗析法、离子计和光谱分析等技术研究了滇池表层沉积物中DOM(溶解性有机质)的分子量分布特征及不同分子量的DOM对Cu和Pb的结合能力.结果表明,草海和外海沉积物中DOM的分子量组成有显著差异.草海沉积物中DOM主要以分子量为3.5～5.0 ku的组分为主;外海沉积物中DOM以分子量为0.5～2.0 ku的组分为主.滇池各级分子量DOM的腐殖化程度(以A3/A4计,A3、A4分别为DOM在300、400 nm处的紫外吸光度)在1.57～6.00之间,而且DOM腐殖化程度和芳香性随着分子量的增加而增大.离子计分析和三维荧光光谱特征表明,Cu趋向于和分子量为2.0～3.5 ku的DOM结合,而Pb趋向于和分子量≤0.5 ku的DOM结合.用结合容量和分配系数(Kd)表征Cu、Pb与DOM在两相中的结合能力,分子量为2.0～3.5 ku的DOM中的w(Cu)最大,草海和外海分别为717.65和340.27 mg/g;分子量≤0.5 ku的DOM中的w(Pb)最大,草海和外海分别为2 988.84和5 073.45 mg/g.

The methods of equilibrium membrane dialysis were employed to determine the molecular weight distribution of dissolved organic matters in the sediment of the Dianchi Lake. Ion selective electrode （ISE） and spectroscopy technology were applied to analyze spectral characteristics of dissolved organic matter （DOM） with different molecular weights and the interaction with Cu and Pb, as well as explore the effect of molecular weight on the interaction between heavy metals and DOM. Results indicated that Caohai DOM was dominated with the molecular weight between 3.5 and 5.0 ku, while Waihai DOM was dominated with the molecular weight between 0. 5 and 2. 0 ku. Overall, the molecular weights of DOM for Caohai were higher than that in Waihai. The UV absorption ratio values （A3/A4） of the various molecular weight DOM, characterizing the humification degree, aromatic structure, ranged from 1.57 to 6.00. and thedegree of humification and aromaticity of DOM increased with the molecular weights increased. The ISE results and 3DEEM spectral characteristics showed that Cu was mainly combined with DOM fraction with molecular weights from 2. 0 to 3.5 ku; Pb tended to be associated with low molecular weight （≤ 0. 5 ku ） DOMs. Complexing capacity and distribution coefficients （Kd ） were used to estimate the capability of Cu and Pb associated with DOM between the dissolved and the associated phases. The results indicated that, the combined Cu was maximal in the DOM with molecular weight of 2. 0-3.5 ku, 717.65 and 340. 27 mg/g in Caohai and Waihai, respectively; and the combined Pb was maximal in lower molecular weight DOM （ G0. 5 ku） , 2988.84 and 5073.45 mg/g in Caohai and Waihai, respectively.