Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences, Beijing, 100083, People's Republic of China.
Environ Sci Pollut Res Int. 2018 Jun;25(17):16913-16921. doi: 10.1007/s11356-018-1878-5. Epub 2018 Apr 5.
Soil organic matters (SOM) have a great retention effect on Cr(VI) migration in subsurface environment, which act as the main electron donors for Cr(VI) reduction; however, Cr(VI) reduction mechanism by different SOM fractions is still unclear, such as undissolved humic acid (HA) and humin (HM). In this study, HA and HM fractions extracted from typical black soil from Northeast China were used to investigate the reaction mechanism between humus functional groups and Cr(VI). According to the results, phenol and hydroxyl were determined as the main electron donors for Cr(VI) reduction by HA and HM instead of carboxyl and carbonyl, which were more likely involved in Cr complexation. Furthermore, Cr(VI) reduction was more dependent on aromatic carbon, rather than aliphatic carbon, and functional groups on the particle surfaces of HA and HM were much more active for Cr(VI) reduction than their interior part. Additionally, HM was found to have a relatively low Cr(VI) reduction capability compared with HA resulting from its high content of cellulose structures that are quite resistant to Cr(VI) oxidation. These results suggest that in the soil environment, undissolved HA tends to play a much more important role than HM in Cr(VI) reduction and retention in the condition that their mass contents are comparable.
土壤有机质（SOM）对地下环境中 Cr(VI)迁移具有很强的保留作用，它们是 Cr(VI)还原的主要电子供体；然而，不同 SOM 组分（如未解离的腐殖酸（HA）和腐黑物（HM））的 Cr(VI)还原机制仍不清楚。在本研究中，我们使用从中国东北典型黑土中提取的 HA 和 HM 组分来研究腐殖质功能团与 Cr(VI)之间的反应机制。结果表明，HA 和 HM 中的酚和羟基被确定为 Cr(VI)还原的主要电子供体，而不是更可能参与 Cr 络合的羧基和羰基。此外，Cr(VI)还原更依赖于芳香碳，而不是脂肪碳，并且 HA 和 HM 颗粒表面的功能团比其内部部分更有利于 Cr(VI)还原。此外，与 HA 相比，HM 由于其富含纤维素结构，对 Cr(VI)氧化具有很强的抵抗力，因此 Cr(VI)还原能力相对较低。这些结果表明，在土壤环境中，在质量含量相当的情况下，未解离的 HA 比 HM 更倾向于在 Cr(VI)还原和保留中发挥更重要的作用。
