[Ecological restoration technologies for mined lands: a review]

Mining activities usually cause catastrophic and extensive environmental changes, and eventually cause major damages to the whole ecosystem. The natural restoration for mine lands and tailings is a very slow process, and even can hardly reach their original states. Therefore, how to develop rapid and efficient approaches to accelerate restoration of mined lands has been highlighted by restorationists and environmental engineers during the past two decades. Almost all studies in this field indicate that the major problems come from soils: such as high metal concentrations, extremely strong acidity resulting from oxidation of pyrite, and poor fertility. Replacement of topsoil is therefore regarded as the most efficient method to alleviate adverse conditions of substrates; if this method is not available, other alternatives with lime, fertilizers, organic manures, garbage, mining wastes, and others will be applicable. In the aspect of using plants, species with strong resistance and rapid growth, like grasses and herbaceous legume, are always the first choice. If utilizing plants for the purpose of phytoremediation, species that are capable of accumulating exceptionally high concentrations of phytotoxic metals and of course, have a huge biomass, are preferably considered. No matter what type of ecosystem a mined land is restored or reclaimed to, an evaluation on whether it is a successful restoration or reclamation should be given. However, more practical, simple, and universal evaluation methods as well as more cost-effective, and operation-easy restoration techniques are still waiting to be developed. A set of artificial restoration methods that can be widely applied was summarized, and a discussion on the advantage and disadvantage of several evaluation systems was conducted in this review.