Ecological restoration of mineland with particular reference to the metalliferous mine wasteland in China: A review of research and practice

Abstract

Despite a principal contributor to the rapid economic growth, the mining industry in China produced a large amount of wasteland and caused water pollution and soil erosion as well as other environmental damages. In 2002, this industry generated 265.4 Mt tailings, 130.4 Mt gangue and 107.8 Mt smelting slags. The degraded land associated with mining is estimated to be 3.2 Mha by the end of 2004, deteriorating the land shortage of China. Restoration of mine wasteland began in late 1970s but the restoration process was sluggish. The overall restoration rate (the ratio of reclaimed land area to the total degraded land area) of mine wasteland was some 10–12% with a higher rate for coal mine spoils but a lower rate for metal-mined derelict land. From 1994 to 2004, 149 research papers were published about the restoration of China's mining wasteland, of which 70 were on metal-mined land and 61 on the non-metal-mined land. Although 37 institutions in China were involved in the restoration research, only a few remained active and productive. Metal-mined derelict land is often more metal toxic and deficient of macronutrients and is tougher for revegetation. Many substrate amelioration techniques were proposed and tolerant plant species were tested for use of reclamation of the metal-mined tailings. Five hyperaccumulator species have been reported in China for the potential use in phytoremediation. However, these accomplishments were all at laboratory or small-scale field demonstration stage and still far from the practical use in reality. To accelerate the restoration and utilization of mine wasteland, several recommendations are put forward in this review. Above these suggestions, the commitment and efficiency of the government at all levels are vital.

Introduction

Our society and civilization now rely heavily on the mining industry to operate and maintain comfort. In China, especially, as a principal raw materials supplier, the mining industry has to expand continuously to meet the demands of the ever-increasing economic growth. More than 95% of non-renewable energy sources, 80% of industrial raw materials and over 75% of agricultural means of production come from the mining and minerals industries (Zhu, 2000). However, mining transforms fertile, cultivated land into wasteland as mining activities generate a vast amount of solid wastes which deposit at the surface and occupy a huge area of lands. Typically a mine degraded wasteland comprises: stripped areas (59%), open-pit mines (20%), tailings dams (13%), waste tips (5%) and land affected by mining subsidence (3%) (Miao and Marrs, 2000). During surface mining, 2–11 times more land is damaged than with underground mining. The direct effects of mining activities can be an unsightly landscape, loss of cultivated land, forest and pasture land, and the overall loss of production. The indirect effects can be multiple, such as soil erosion, air and water pollution, toxicity, geo-environmental disasters, loss of biodiversity, and ultimately loss of economic wealth (Wong, 2003, Xia and Cai, 2002).

For nearly three decades in China, we were taught that the country we lived was a vast territory with unexhausted abundant resources. With more than 21% of the world's population living on cultivated land which is less than 10% of the total area available on earth (Lin and Ho, 1996), this widely held belief has been challenged greatly with the loss of its extremely scarce arable lands (0.106 ha cultivated land per capita against the world's average of 0.236 ha) to industrial expansion, mining operation and urbanization. It was reported mining activities alone in China have generated a total derelict land of about 3.0 million ha by the end of last century (Wong and Luo, 2003) and the figure is increasing at an alarming rate of 46,700 ha per year (Bai et al., 1999). Some 280,000 mines were in operation in 1994 and 5 million people were employed in the mining sector (UNEP, 1997). Of these mines, over 8000 were state-owned mining enterprises and around 230,000 were small-scale mining workshops (Shu et al., 2003) throughout the country, many of which were located in the poor and remote areas. Mining operations and their associated mine tailings polluted a land area of 600,000 ha (Li et al., 2004), causing a direct economic loss of over RMB 9 billion yuan and an indirect loss of about 30 billion each year (Liu and Shu, 2003).

The Chinese Government learned a good lesson from the past and realized that rehabilitation of mineland is one of the pressing needs to be addressed for social and economic development to be healthy and sustainable. In their tenth 5-year plans (2000–2005), many provincial governments have designated ecological restoration of mined wastelands as one of the priority issues to be solved and set up quantified restoration goals to be achieved. This contribution, based on the author's research on the latest publications from the last 10 years and other related data published in China, aims to examine the current situation of ecological restoration of mine wasteland, both on research and practice. More attention is placed on the metal-mined wasteland as this part usually represents greater problems and is tougher for restoration.