溶液培养条件下腐殖酸对Cr(Ⅵ)微生物还原的影响

Effect of Humic Acids on Microbial Reduction of Cr(Ⅵ) in Aqueous Condition

探明铬(Cr)的氧化还原作用机制对于深入认识其污染过程特征进而制订科学的防控措施有重要意义。本研究采用从山西大同风化煤、河南巩县褐煤和云南昆明滇池底泥中提取的腐殖酸(分别记为HAs、HAh、HAk),通过分别添加,以及共同添加葡萄糖和不同制备来源或不同浓度的腐殖酸,并接种水稻土悬液,研究了溶液培养条件下腐殖酸对Cr(Ⅵ)的微生物还原过程的影响。结果表明:在有充足碳源存在条件下腐殖酸能够发挥其电子传递作用促进Cr(Ⅵ)的微生物还原过程。腐殖酸促进Cr(Ⅵ)还原的作用随其添加浓度的升高而增强,腐殖酸浓度为0.02 g/L时其促进作用较微弱,而2.00 g/L时培养期间Cr(Ⅵ)的还原率达到95%以上。腐殖酸的结构组成差异对其作用于Cr(Ⅵ)的微生物还原过程有重要的影响,腐殖化程度相对较高的HAk和HAs对Cr(Ⅵ)的微生物还原的促进作用明显,HAk更因含有一定量的多糖或类多糖物质而加快了Cr(Ⅵ)微生物还原过程的发生时间,而HAh则对Cr(Ⅵ)的微生物还原的影响较小。

Better understanding the processes of Cr（Ⅵ） microbial reduction to Cr（Ⅲ） is of great interest in bioremediation of contaminated environments. In this study, the paddy soil suspension was used as microbial inoculation and humic acids were extracted from materials as weathering coal of Datong in Shanxi Province, lignite of Gongxian in Henan Province and Dianchi Lake sediment （abbreviated respectively as HAs, HAh, HAk）. The effects of humic acid on microbial Cr（Ⅵ） reduction were studied by adding glucose or humie acid （HA） solely/together in anaerobic aqueous condition. The results indicated that the microbial Cr（Ⅵ） reduction process was promoted by humic acid which acted as electron shuttles in the presence of the available carbon source. The stimulative effect on the microbial Cr（Ⅵ） reduction enhanced with the concentrations of humic acid added, the concentration as 0.02 g/L almost had little effect while 2.00 g/L reduced above 95% of the Cr（Ⅵ） in solution. HA extracted from different materials had distinct influences on microbial Cr（Ⅵ） reduction. HAk and HAh had greater effects than HAh for their higher degree of humification, HAk contained certain polysaccharides or polysaccharide-like which also advanced the processes of microbial Cr（Ⅵ） reduction. The effect of HAk on microbial Cr（Ⅵ） was very weak.