冻融作用对土壤中溶解性有机物的光谱学特性的影响

以受季节性冻融过程影响显著的辽宁省棕壤和暗棕壤为研究对象,考察了冻结温度、融化温度、冻结时间和冻融次数对土壤中溶解性有机物(DOM)的光谱学特性的影响.结果表明:冻融处理条件下土壤中的溶解性有机碳(DOC)含量、波长254 nm处的紫外吸光度(UV-254)和单位浓度DOC的紫外吸收值(SUVA)的变化规律相似,均随冷冻和融化温度的升高而增大,随冷冻时间的延长先减小后增大,随冻融次数的增多而减小.冻融作用使DOM的腐殖化程度提高,分子量减小.随着冷冻时间的延长,DOM中类富里酸荧光物质和类腐殖酸荧光物质的含量先减少后增多;随着冻融次数的增多,DOM中荧光物质的含量逐渐减少.研究成果对于准确掌握冻融条件下土壤中DOM的变化规律,以及实施有效的土壤生态环境和地表水流域环境管理具有重要的理论意义和实用价值.

Effect of freezing-thawing on the spectroscopic characteristics of dissolved organic matter in soil

The effect of freezing and thawing temperatures, freezing time, and times of freeze-thaw cycles on the spectroscopic characteristics of dissolved organic matter (DOM) in dark-brown and brown earths in Liaoning Province was investigated. The results showed that variations of dissolved organic carbon (DOC) contents, absorbance of ultraviolet light at 254 nm (UV-254), and specific ultraviolet light absorbance (SUVA) soil caused by freezing-thawing were similar. They increased with increasing freezing and thawing temperatures, decreased initially and then increased with increasing freezing time, and decreased with increasing times of freezing-thawing cycles. The humidification degree of DOM increased and the molecular weight of DOM decreased as a result of freezing-thawing. The contents of fulvic and humic acid-like fluorescent materials in DOM decreased initially and then increased with increasing freezing time. The contents of fluorescent materials in DOM decreased with increasing times of freezing-thawing cycles. The research results are of important theoretical significance and practical value for the accurate grasp of variations of DOM in soil resulted from freezing-thawing, and are helpful for carrying out effective managements of soil ecological environment and surface water basin environment.