赤泥堆场土壤团聚体结构形成与稳定性调控研究

Bauxite residue is an alkaline, saline-sodic waste byproduct generated by the extraction of alumina from bauxite. The global inventory reached more than 4.0 billion tonnes and is predicted to increase by 150 million tons per annum. Disposal and storage of the vast amounts of bauxite residue still remains an increasing problem. Ideally this residue would be utilized as an industrial by-product for other applications, leading to a zero waste situation. However, little evidence exists of any significant utilization of bauxite residue. Establishment of a vegetation cover is the most promising way forward for the management of bauxite residue, although its physical and chemical properties can limit plant growth due to high alkalinity and salinity, low hydraulic conductivity, metal element toxicity (Al and Fe) and deficiencies in organic matter and nutrition concentrations. Spontaneous vegetation colonization on deposits in Central China, over a period of 20 years, has revealed that natural weathering processes may convert bauxite residue to a soil-like medium. The hypothesis of this work is whether natural weathering processes can ameliorate BRDAs and improve soil aggregation and formation over time without human assistance, whilst predictors of soil genesis and soil-forming factors during the pedogenic process of bauxite residues and stability regulation in bauxite residue have also been considered. Samples from the different stacking ages are selected to determine aggregate formation and stability, and its relationship with iron-aluminum oxides and organic carbon. Pedogensis in restored bauxite residue is driven by the development of roots systems and soil communities. According to the natural succession phenomenon, the study investigates aggregate formation and structural stabilization of the residues following natural regeneration, and the effect of substrate amelioration on aggregate formation and stabilization of bauxite residue. The potential results of this project may provide a theoretical basis for understanding the mechanism of aggregate formation in bauxite residue, and offers a scientific basis for improving soil genesis and rehabilitation on bauxite residue disposal areas.

赤泥是氧化铝工业生产过程中产生的强碱性废弃物，盐分含量高、金属毒性强、环境风险大、综合利用难，资源化利用率<5%、大量外排赤泥以堆存为主，2016年全球赤泥堆存量已超过40亿吨，并以1.5亿吨/年的速度增加，赤泥堆场的环境安全问题正严重威胁氧化铝工业的可持续发展，探索适宜的的赤泥处置方式已成为政府管理部门和氧化铝企业面临的紧迫任务之一，而赤泥土壤化则是一种有发展前景的赤泥规模化处置方法。项目拟在氧化铝赤泥堆场生态调查的基础上，以不同环境条件下的典型赤泥堆场为研究对象，开展赤泥堆场土壤团聚体结构形成及稳定性调控研究，分析赤泥堆场风化过程的土壤发生学特性研究，探讨赤泥堆场土壤发生过程的团聚体结构形成机制，以期实施赤泥堆场成土过程中的团聚体稳定性调控。研究成果对于实现氧化铝工业赤泥的土壤化处置、加快赤泥堆场的生态重建、经济安全地消除赤泥堆场环境隐患具有重要意义。

赤泥是氧化铝生产过程中排放的强碱性固体废物，也是有色金属工业排放量最大的固体废物，综合利用率<3%，以堆存方式为主，全球赤泥堆存量约50亿吨，迄今尚无经济可行的处置方法，赤泥堆存的环境安全问题正严重制约铝工业的可持续发展。通过对典型赤泥堆场开展生态调查，发现自然风化过程促进赤泥物理性状改善，孔隙度增加，水稳性团聚体含量提高，微生物生物量和微生物量碳氮增加，葡萄糖苷酶、脲酶和碱性磷酸酶活性增强，有机碳和pH是赤泥堆场微生物群落演替的主要驱动因子；施用污泥增强赤泥稳定性，改变微生物群落多样性，变形杆菌门、拟杆菌门的相对丰度增加，pH值和EC是影响微生物结构的主要因素；配施磷石膏和腐殖酸-丙烯酰胺共聚物能够提高赤泥总孔隙率、总孔容、平均孔径等指标，改善赤泥孔隙形态特征，增强团聚体稳定性；盐分离子分布、铁铝氧化物形态、有机碳含量等影响团聚体的形成，脱硫石膏改变赤泥大团聚体（2-0.25 mm）离子的分布，铁铝氧化物对<0.05 mm团聚体作用更大，有机碳能促进赤泥成土过程中团聚体结构的改善；草酸青霉添加明显提高团聚体中多糖和微生物残体的含量，植物-微生物-改良剂联合作用促进大团聚体的形成，降低了微团聚体的比例，有助于促进赤泥团聚体稳定性增强。经过四年的努力，培养博士3名、硕士4名，在国内外知名期刊发表SCI/EI论文23篇（第一标注11篇、第二标注12篇），授权国家发明专利1件，主办第二届赤泥土壤化处置及堆场生态修复国际学术研讨会（2019年）。这些研究成果，对于实现赤泥土壤化处置、加快堆场生态重建、消除赤泥堆场环境隐患具有重要的科学意义。