赤泥自然成土过程及其微生物驱动机制

氧化铝废渣(赤泥)堆场生态修复的关键是赤泥土壤化。运用空间代替时间的方法,在未采取人工修复措施的赤泥堆场采集具有时间序列特征的赤泥样品,通过测定其理化生化指标及微生物群落结构变化,研究赤泥的自然成土过程及其微生物驱动机制。结果表明: 随赤泥泥龄的增加,其物理指标孔隙度、水稳性团聚体含量、团聚体平均重量直径提升,容重降低;化学指标pH值、电导率、酸中和能力和交换性钠饱和度降低;生化指标有机碳、总氮、有效态磷、微生物生物量碳、土壤基础呼吸提升,代谢熵降低。微生物Shannon多样性指数增加,群落结构由产氧光合细菌蓝细菌门、不产氧光合细菌绿菌门和绿弯菌门占据绝对优势转变为变形菌门、放线菌门和厚壁菌门占据优势地位,富营养细菌与贫营养细菌丰度比值明显增加。微观形态分析表明,微生物及其代谢产物通过对赤泥颗粒的吸附、链接、缠绕及包裹形成微生物-赤泥聚合体。在自然堆置过程中赤泥自发地由贫营养的极端生境向土壤生境转变,微生物通过提升营养水平、降低盐碱度、改善质地结构等途径参与赤泥的自然成土过程。

Natural soil genesis in red mud and underlying microbial mechanism.

Soil genesis is important for ecological restoration of red mud disposal area. Soil genesis of red mud and the microbial mechanism were studied by analyzing the change of physicochemical and biochemical characteristics of red mud. We analyzed the microbial community structure in a red mud disposal area without any human-induced restoration through a space for time substitution approach. The results showed that, with the increases of storage time, the physical parameters of porosity, water-stable aggregates content, and mean weight diameter increased, but the bulk density decreased. The chemical parameters, including pH, electrical conductivity, acid neutralizing capacity, and exchangeable sodium percentage, decreased with increasing storage time. The bio-chemical parameters of total organic carbon, total nitrogen, available phosphorus, microbial biomass carbon and basal respiration increased, but the metabolic quotient decreased. The Shannon diversity index increased, and the dominant microflora in red mud changed from the oxygenic photosynthetic bacteria Cyanobacteria and thanaerobic anoxygenic phototrophic bacteria Chlorobi and Chloroflexi to Proteobacteria, Actinobacteria and Firmicutes. The ratio between eutrophic and oligotrophic bacteria substantially increased. The micromorphology results showed that the microorga-nism-red mud aggregates were formed through adsorption, linkage, intertwinement and package between red mud particles, microbial cells and their metabolites. The red mud biotope changed spontaneously from extreme and oligotrophic into soil-like under natural stockpiling. The soil genesis process was mediated by microbes through increasing nutrient level, decreasing alkalinity and sali-nity, and improving soil structure.