生态修复条件对铁路岩石边坡创面人工土壤Pb、Cd污染特性的影响及机理

In mountainous areas, a large number of rock cut slopes have been left by rapid railway constructions. Artificial soil is widely used onto the surface of the rock cut slopes to promote the establishment of vegetation. Pb and Cd are the main heavy metal elements produced by railway transportation. However, little is known regarding the effects of re-vegetation conditions on the pollution of Pb, Cd in the artificial soil on the surface of railway rock cut slopes，and this is an important issue which needs to be solved urgently. In this project, we choose some typical railway rock slopes with different re-vegetation time and vegetation modes, and simulated slopes with different types of artificial soil and vegetation modes as our study objectives. The soil properties, vegetation conditions and contamination characteristics of Pb, Cd will be investigated by field orientation experiments, simulated experiments and pot experiments. The effects of re-vegetation time, vegetation modes and artificial soil types on the pollution characteristics of Pb and Cd, and the mutual relationships among the soil properties, vegetation conditions and contamination characteristics of Pb, Cd will be studied. Furthermore, with the results of these studies we will find out the contamination mechanism of Pb, Cd in the artificial soil on the surface of the railway rock cut slopes, and provide the theoretical basis for the ecological management of the rock slopes and the scientific protection of roadside environment.

山区大规模的铁路建设造成了大量的裸露岩石边坡，人工土壤是人为建造在岩石边坡创面上满足植物生长的植生基材。Pb、Cd是铁路运输产生的主要重金属，然而，生态修复条件对铁路岩石边坡创面人工土壤Pb、Cd污染特性有何影响尚不清楚，是亟待解决的基础性科学问题。因此，本项目针对不同生态修复年限和植物搭配类型互作条件下的典型铁路岩石边坡、不同人工土壤类型和植物搭配类型互作条件下的模拟铁路岩石边坡，利用野外定位试验、模拟实验、盆栽实验，调查测定铁路岩石边坡创面人工土壤的Pb、Cd污染特性以及土壤性质与植被状况。阐明生态修复年限、人工土壤类型、植物搭配类型对铁路岩石边坡创面人工土壤Pb、Cd污染特性的影响，明确铁路岩石边坡创面人工土壤Pb、Cd污染与土壤性质、植被状况之间的互馈关系，揭示铁路岩石边坡创面人工土壤Pb、Cd污染的形成机理，为铁路岩石边坡的生态治理与路域环境保护提供理论依据。

以不同生态修复年限、植被类型、人工土壤类型的典型岩石边坡、模拟岩石为对象，研究了边坡植被状况、优势植物生物量及Cd、Pb含量、土壤理化性质、侵蚀状况、人工土壤Cd、Pb 含量和形态等。结合人工降雨实验，研究了Cd、Pb的迁移规律及生态风险，探索了生态修复年限、植被类型、人工土壤类型对Cd、Pb污染的影响及其作用机制。结果表明，道路边坡均受到不同程度的Cd、Pb污染，Cd、Pb 有中等程度的富集，Cd的生态风险较大，Pb的生态风险较小，污染程度随生态修复时间的增加而升高。植被类型和人工土壤类型显著影响Cd、Pb迁移。草灌乔植被类型具有更高的生物量和根重量密度，优势植物对Cd有很好的固定作用，通过减少地表径流、土壤流失，减少Cd、Pb迁移量。植被生物量、根重量密度、优势植物对Cd和Pb的固定作用是影响Cd、Pb迁移的主要因素。人工土壤随着农田土含量的增高，土壤质量指数和抗侵能力增加，Cd、Pb迁移量减小。人工土壤类型影响土壤的物理、化学、生物性质，从而影响土壤质量和抗侵蚀的能力，进而影响土壤流失量以及随土壤流失的Cd和Pb 的量，影响其生态风险。本研究结果为铁路岩石边坡的生态治理与路域环境保护提供理论依据。