交替冻融对松花江流域典型土壤可溶性有机碳的影响

Freeze-thaw Cycles Effects on Dissolved Organic Carbon of Typical Soils in Songhuajiang River Watershed

以受季节性冻融过程影响显著的黑土、暗棕壤和水稻土为例,采用实验室模拟的方法,研究交替冻融循环过程(分别在-20℃和20℃下处理)对土壤可溶性有机碳(DOC)的影响。研究表明,初次交替冻融后暗棕壤和水稻土DOC升高,黑土DOC仅降低1.3%。随着冻融次数增加,黑土和暗棕壤DOC含量逐渐下降,并趋于稳定,水稻土DOC呈交替上升趋势。15次交替冻融后,黑土DOC含量下降21%,水稻土DOC含量上升9%,暗棕壤DOC含量未出现明显变化。三维荧光分析结果验证了土壤DOC的变化趋势,15次交替冻融后,黑土可溶性有机物结构变复杂,分子量增加;水稻土可溶性有机物结构变简单,分子量变小;暗棕壤产生的新物质,一部分使可溶性有机物结构变复杂,分子量变大,另一部分使有机物分子量变小。

The study investigated the effects of freeze-thaw cycles（FTCs） on the dissolved organic carbon（DOC） in black soil（BS）,dark brown soil（DS） and paddy field soil（PS） by indoor simulating experiments.The result showed that after the first FTC treatment at-20 ℃ and at 20 ℃,the DOCs in DS and PS increased and the DOC in BS decreased slightly.After the second FTC,the DOCs in DS and BS decreased and then tended to be stable.After fifteenth FTC,the DOC in BS sample decreased by 21%.The DOC in DS sample changed a little.In contrast,from the 2nd to 15th FTC,the DOC in PS sample increased wavelike.The DOC in PS sample increased by 9% finally.The trends of DOCs in soil samples were identified from the result of EEM fluorescence spectra.The molecular weight of BS DOC increased and it decreased in the PS DOC sample.While in DS sample,some part of new substance produced in the freeze-thaw cycles had higher molecular weight and the other part had lower molecular weight.