中文摘要：

选取位于吉林龙升、河南封丘、浙江慈溪和江西进贤的4种水稻土剖面，分析比较了不同气候带水稻土剖面和各粒级复合体的有机碳及其δ^13C值的分布特征，探讨了不同水稻土胡敏酸结构和功能基团构成的差异，旨在为深入研究水稻土有机碳动态变化和运转机理提供参考依据。结果表明：不同气候带水稻土剖面中，有机碳δ^13C值均随着土层深度的增加逐渐升高；样点位置愈往北，水稻土表层有机碳δ^13C值愈高。各样点水稻土表层有机碳主要集中在〈10μm复合体部分，其有机碳分配系数均大于50％。水稻土不同粒级复合体δ^13C值随着粒级的减小不断升高，高δ^13C的老碳在细粒中富集；水稻土表层〈10μm复合体中有机碳的降解程度为：封丘〉慈溪〉进贤〉龙井。各样点水稻土胡敏酸结构大致相似，封丘和龙井的水稻土胡敏酸含有较多C=O基团，氧化程度较高，另外，其胡敏酸的芳化度和聚合程度也高于慈溪和进贤的水稻土。

英文摘要：

Profiles of paddy soils were sampled in Longjing of Jilin Province, Fengqiu of Henan Province, Cixi of Zhejiang Province and Jinxian of Jiangxi Province, which are in different climatic zones. Distribution of organic carbon （OC） and δ^13C in profiles and organo-mineral complex of the paddy soils was studied, and structure and functional group composition of humic acid （HA） in different paddy soils was explored with the aid of infrared spectrum （IR）. Its aim was to provide some scientific data for reference for the study on organic carbon dynamics and its mechanism. With increasing soil depth in profiles of paddy soils, δ^13C of OC increased gradually, and with increasing latitude of the locations of the profiles, δ^13C of OC increased gradually, too, in the topsoil of the paddy soils. Topsoil OC of paddy soils was mostly concentrated in organo-mineral complex in the size fraction 〈 10 μm, and their OC abundance was over 50%. With decreasing particle-size, δ^13C of topsoil complex increased continually, and old OC high in δ^13C natural abundance accumulated in fine particles. In terms of degradation degree of OC in soil complex 〈 10 μm, the four profiles were in a decreasing order of Fengqiu 〉 Cixi 〉 Jinxian 〉 Longjing. Structure of the HA differed slightly between paddy soils. Compared to paddy soils sampled in Cixi and Jinxian, paddy soils sampled in Fengqiu and Longjing contained HA high in C=O groups, and in oxidation, aromatization and polymerization degrees.