Remediation strategies for historical mining and smelting sites.

The environmental, social and economic problems associated with abandoned mine sites are serious and global. Environmental damage arising from polluted waters and dispersal of contaminated waste is a feature characteristic of many old mines in North America, Australia, Europe and elsewhere. Today, because of the efficiency of mining operations and legal requirements in many countries for prevention of environmental damage from mining operations, the release of metals to the environment from modern mining is low. However, many mineralized areas that were extensively worked in the 18th and 19th centuries and left abandoned after mining had ceased, have left a legacy of metal contaminated land. Unlike organic chemicals and plastics, metals cannot be degraded chemically or biologically into non-toxic and environmentally neutral constituents. Thus sites contaminated with toxic metals present a particular challenge for remediation. Soil remediation has been the subject of a significant amount of research work in the past decade; this has resulted in a number of remediation options currently available or being developed. Remediation strategies for metal/metalloid contaminated historical mining sites are reviewed and summarized in this article. It focuses on the current applications of in situ remediation with the use of soil amendments (adsorption and precipitation based methods are discussed) and phytoremediation (in situ plant based technology for environmental clean up and restoration). These are promising alternative technologies to traditional options of excavation and ex situ treatment, offering an advantage of being non-invasive and low cost. In particular, they have been shown to be effective in remediation of mining and smelting contaminated sites, although the long-term durability of these treatments cannot be predicted.