Ecological Restoration of Oil Shale Waste Dumps

27 Mar Ecological Restoration of Oil Shale Waste Dumps

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Abstract

油页岩开采带来一系列的生态与环境问题 ,但对油页岩废渣场进行生态恢复的历史还较短 ,也缺少系统专门的研究报道。 国外对油页岩废渣的利用始于 20世纪 40年代 ,对废渣场生态恢复的研究始于 20世纪 60年代 ,均早于我国。 由于废渣场的基 质成分恶劣 ,缺乏一般的土壤结构 ,复垦难度大。 一般有 3种常规的复垦方法: 不经处理直接栽种植物 ;常规的物理或化学处理 后栽种植物;表土覆盖后再进行植被恢复。前 2种方法均难产生显著效果 ,第 3种见效较快 ,但工作量大。近年来 ,一些新技术 , 如生物降解、生物富集和生物强化技术等被发明并用来恢复油页岩废弃地 ,取得了较好的生态恢复与修复效果。我国从 1985年 开始 ,在广东茂名进行油页岩废渣场的生态恢复工作 ,先后对面积达 1. 4 km2 和 6. 7 km2 的 2个大型废渣场 (南排土场和北排 土场 )进行了治理 ,主要是采用生物修复技术中的植物修复来进行试验。南排土场经过 19a的复垦演替成了郁郁葱葱的森林;北 排经过 5a的实践也取得了很好的恢复效果 ,一些幼林初步形成。 然而 ,当前北排土场恢复实践中出现了一些很值得关注的现 象 ,如乔木树种矮化、分枝增多等 ,但这些问题还有待进一步研究解决。 此外 ,还探讨了油页岩废渣场开展生态恢复的步骤与原 则。

English Abstract

Mining activities of oil shale always result in a lot of ecological and environmental issues, and there is a shortage of specific or systematic reports on successful revegetation of oil shale waste dumps so far due to its short research history. Utilization of oil shale wastes began in the 1940s and ecological restoration of waste dumps started in the 1960s, both of them being implemented earlier outside China. It is difficult to revegetate waste dumps, because the substrate conditions are very harsh, and what’s worse is that they are devoid of natural soil components and suitable structure. Generally, there are three methods to adopt for restoring waste dumps: (1) plant the vegetation such as trees or shrubs directly on the untreated waste dump; (2) first treat the waste dump with common physical or chemical methods, and then plant trees or shrubs on it; and (3) cover the waste dump with topsoil at first, and then conduct revegetation work. The former two methods are difficult to gain satisfactory restoration effects while the third is labor-intensive and concerns a very high cost though it can produce a good restoration benefit. Some new techniques to accelerate the restoration process, such as biodegradation, bioaccumulation, and bioaugmentation, have been invented or introduce to the restoration of oil shale waste dumps in recent years. Furthermore, some better and more efficient utilization and rehabilitation methods have been obtained from countries such as Estonia, USA and Australia. China’s earliest restoration research on oil shale waste dump started in 1985, which was carried out in Maoming, Guangdong province. Two large-scale waste dumps, whose areas are 1.4 km~2 and 6.7 km~2, respectively, have been rehabilitated since then. The principal measure for rehabilitation is phytoreclamation. The smaller waste dump has been reclaimed into a forest park, winning a huge success through 19 years of its endeavor. The larger one has also obtained a good restoration outcome during the 5 years of practice which some young forests have come into being, though the area is still under restoration. However, some new phenomena, such as dwarfism of some tree species and a conspicuous increase of their lower ramification, occurred during the restoration process of the larger waste dump in recent years. The species producing the abovementioned changes are mainly Gmelina arborea, Cinnamomum camphora, Ilex rotunda, and Jacaranda acutifolia. Therefore, it is necessary and beneficial to sum up experiences and achievements and to probe into new solutions to those problems. The steps and principles for restoration of oil shale waste dumps are summarized in the paper.