土壤中铬进入食物链的微生物抑制和解毒作用基础研究

In order to reduce the toxicity of chromium in the soil, inhibit the absorption of the crops on the chromium，ensure food security and protect human health, the project intends to define the proportion of different valence and morphology of chromium under different soil environmental conditions, screen indigenous reducing bacteria in the soil with superior Cr (III) and steady-state chromium, obtain the dominant strain and mixed flora by vaccination, acclimation and selection. The bacteria efficient agents will be made by adding the appropriate amount of specialty fertilizers and soil amendments. And then the study will focus on the conversion rate of Cr (VI), the production of steady-state chromium, the different influencing factors, the transformation mechanisms, the transformation process dynamics, as well as the impact on the soil microecosystem under different soil environmental conditions. Finally, the research will obtain the inhibition and detoxification effects of chromium into the food chain and summarize the evaluation indicators and procedures..The soil remediation program proposed in this project can carry out easily and cheaply in situ without treatment facilities. The method can also be applied to biological treatment of chromium-containing slag and chromium-containing solid waste，so it shows a very broad application prospects. The study will provide a new method for the remediation in situ of soil contaminated by heavy metal and promote the development of bioremediation technology.

为降低土壤中重金属铬的毒性，抑制农作物对铬的吸收，保证食品安全，保护人群健康，本项目拟在不同土壤环境条件下，明确各种价态和形态铬的比例，并在Cr(Ⅲ)与稳态铬占优势的土壤中筛选土著还原菌，经接种、驯化和选育，获取优势菌种和混合菌群；适量添加特种化肥和土壤改良剂，并制成高效菌剂；采用土壤微宇宙试验装置，在不同土壤环境条件下，系统研究Cr(VI)的转化率、稳态铬的产生量、各种影响因素、转化机理及转化过程动力学，以及对土壤微生态的影响，最后获取铬进入食物链的抑制和解毒效果，给出评价指标和程序。.本项目提出的土壤修复方案可充分利用现场进行原位修复，不需处理设施，使用简便，运行费用低廉，还可推广应用于铬矿渣以及含铬固体垃圾的生物处理，应用前景非常广阔。该项研究可为土壤重金属污染的原位修复提供一种新方法，推动生物修复技术的发展。

本项目确定了六价铬高效还原菌驯化、筛选、分离的程序和方法，获得4株高效还原菌，对还原效果最优的菌株Cr4-1，经生理生化检验和16s rDNA鉴定，确定该菌株为蜡样芽孢杆菌。系统研究了蜡样芽孢杆菌Cr4-1的生长特性以及六价铬初始浓度、温度、酸碱度、溶解氧对还原效果的影响。乳酸钠和丙酮酸钠是细菌Cr4-1生长和还原的最佳碳源，乳酸钠的最佳浓度为12g/L。葡萄糖、甘油、琥珀酸钠也是该细菌的良好碳源和电子供体。. 蜡样芽孢杆菌Cr4-1对六价铬的还原动力学研究表明，在六价铬初始浓度为30mg/L-90 mg/L时，该还原菌对六价铬的还原符合一级动力学模型，反应速率与反应物浓度的一次方成正比。. 初步判断，蜡样芽孢杆菌Cr4-1的还原反应为酶介导。菌株Cr4-1的溶解在铬还原过程中可能起到重要的作用，还原终产物为可溶性三价铬。. 六价铬污染的土壤微宇宙中，蜡样芽孢杆菌Cr4-1可高效还原土壤中的Cr(VI)。向土壤中添加碳、氮源，能够促进Cr(VI)的还原。铬污染土壤与无铬污染土壤中微生物群落组成结构以及物种总数和多样性差异较大。蜡样芽孢杆菌还原土壤六价铬的修复过程中，土壤微生态多样性维持稳定状态。. 本课题研究结果为土壤重金属污染的原位生物修复提供了科学依据和技术支撑，还可推广应用于铬矿渣以及含铬固体垃圾的生物处理，应用前景非常广阔。.