中文摘要：

还原容量（RC）是衡量胡敏酸（HA）还原特性的重要指标。采用饱和H2振荡法和土壤溶液法对HA分别进行化学和微生物预处理，分别以硝酸铁（Fe（NO3）3）、柠檬酸铁（FeCit）作电子受体，测定了三种HA（上海巨枫SH，天津光复TJ，缙云山JY）的本底还原容量（NRC），化学还原容量（CRC），微生物还原容量（MRC）。对不同电子受体条件下、不同初始状态和不同种类的胡敏酸的RC进行比较。结果表明：三种HA中，以缙云山土壤提取的胡敏酸RC值最高，还原容量最大，分别为20．21±0．26mm01．mol^-1C（NRC）、26．02±1．12mmol，mol^-1（CRC）和29．29±1．56mnlol。mol^-1C（MRC）。两种电子受体中，采用Fe（NO3），得到的RC明显高于在FeCit条件下。另外，溶液态HA的RC明显高于固态。由此证明胡敏酸还原容量是一个相对量；其容量大小不仅和自身结构、性质有关，也受到HA初始形态和不同电子受体的影响。对比三个还原容量指标发现CRC和MRC显著大于NRC，而CRC和MRC之间无明确大小关系，因此用CRC来表征HA被微生物还原后的还原容量（MRC）还需作进一步验证。

英文摘要：

As an important parameter, Reduction capacity （RC） is recognized for evaluating redox characteristics of humic acids （HA） in environment. In this study, three HAs （tagged as SH, TJ and JY respectively） from different sources were selected and pretreated through methods of saturated hydrogen oscillation and soil solution incubation respec- tively for determining chemical reduction capacity （CRC） and microbial reduction capacity （MRC） by reduction of two electron acceptors including ferric nitrate （ Fe（ NO3 ） 3 ） and ferric citrate（FeCit） , in comparison with native reducing ca- pacity （NRC） obtained through the same measurement method based on HA samples without any pretreatments, The re- suits suggested that HA extracted from local humus layer of soil in JinYun Mountain had the greatest RC among three hu- mic acids, which showed the highest RC values of 20.21 ±0.26 mmolo mo1^-1 C （NRC）, 26.02 ± 1.12 mmolo mol-j C （CRC） and 29.29 ± 1.56 mmolo mol^-1 C （ MRC）, respectively. Meanwhile, Of the two electron acceptors, Fe（ NO3 ） 3 induced much higher RC than FeCit. In addition, HA in solution status showed higher RC than in solid status. All the above findings demonstrate that reduction capacity （RC） of HA is a variable parameter, which is closely related to the structure and properties of the HA per se and also affected by its initial status （e. g. solution or solid） and electron accep- tots. Comparison between the RC indexes of the HAs shows that CRC and MRC were evidently higher than NRC, however no significant difference in magnitude was observed between CRC and MRC. However, whether it is feasible to use CRC to characterize MRC needs further study for validation.