土壤溶解性有机质荧光特征及其与铜的络合能力

选取4种不同类型土壤和腐熟鸡粪,透析提取溶解性有机质(DOM),通过凝胶色谱、三维荧光光谱测定并分析了DOM的相对分子质量(M_r)分布、化学结构特征及其与铜的结合能力.结果表明,鸡粪DOM相对分子质量积分面积远高于其他样品,表现出其具有较高的有机物含量,泥炭土次之.暗棕壤、褐土和黑土较低,仅为鸡粪积分面积的4.5%~5%.鸡粪在中分子量段积分面积约占总物质的34.1%,低分子量段和高分子量段分别约占41.7%和24.2%.荧光光谱分析表明,各样品均出现类蛋白荧光峰(E_x/E_m=240~270/300~350 nm),在中、高分子量段(M_r500)暗棕壤存在的荧光峰消失.泥炭土出现了较为独特的可见光区类富里酸荧光峰(E_x/E_m=325/420 nm),该荧光峰和黑土的荧光峰在中、高分子量段(M_r500)都产生了红移现象.鸡粪分别出现了和黑土类似的紫外区类富里酸荧光峰,以及和泥炭土类似的可见光区类富里酸荧光峰,以及一类独特的类蛋白荧光峰(E_x/E_m=280/350 nm),但这种类蛋白荧光峰在中分子量段(500M_r12 000)消失.分析表明泥炭土与Cu的络合常数(lg K)为4.13,其他3种土壤与Cu的络合常数较小且差别不大,集中在2.10~3.10之间.鸡粪与Cu的结合能力最大,络合常数达到6.66.

Fluorescence Spectroscopic Characteristics and Cu2+-complexing Ability of Soil Dissolved Organic Matter

Extracted and dialyzed from four kinds of soil and chicken manure, DOM samples were analyzed to investigate their molecular weight distribution, chemical structure characteristics and the metal binding capacity. The results showed that the integral area of the molecular weight of chicken manure DOM was much higher than those of other samples, which indicated the high content of organic matter. And the peat soil followed it. The integral areas of dark brown soil, cinnamon soil and black soil were low, accounting for only 4.5%-5% of chicken manure integral area. The integral area of chicken manure DOM in middle molecular weight fraction accounted for about 34.1% of the total material, while those in low molecular weight and high molecular weight fractions accounted for about 41.7% and 24.2%, respectively. The protein-like fluorescence peaks (E_x/E_m=240-270/300-350 nm) were present in all samples, and absent in middle and high molecular fractions (M_r>500) for dark brown soil. The visible fulvic acid-like florescence peaks (E_x/E_m=325/420 nm) observed in peat soil, and the florescence peaks of black soil in the middle and high molecular fractions (M_r>500) both had a red shift phenomenon. The DOM of chicken manure had the UV-fulvic acid-like florescence peaks similar to black soil, and the visible fulvic acid-like florescence peaks similar to peat soil. Furthermore, it had a kind of protein-like fluorescence peak (E_x/E_m=280/350 nm) that was absent in the middle molecular weight fraction (500< M_r< 12000). The Cu²⁺ complexation constant was 4.13 for peat soil, and smaller for other three kinds of soil (between 2.10 and 3.10). Chicken manure showed the greatest ability to bind Cu²⁺ with a resulting complexation constant of 6.66, indicating the importance of the unique peak, protein-like fluorescence peak, in the chicken manure of the low and high molecular weight fractions.