Acid-tolerant plant species screened for rehabilitating acid mine drainage sites

Large areas of land have been impacted by acidic mine drainage. These sites could potentially be re-vegetated for growing energy plants. Conventional phytoremediation method may fail because the pH of some mine drainage and contaminated soils can reach 2.0. Thus, it is necessary to screen acid-tolerant plants as pioneers to rehabilitate those severely acidified areas. In the first phase of this study, seven levels of low pH media were used to estimate the acid-tolerant ranges of three plant species for 1 month. In the second phase, 50 commonly cultured plant species from 17 families, native in Guangdong Province of China or introduced from Australia, were evaluated for acid tolerance at three pH levels which were chosen based on results in the first phase. We found that Acacia auriculiformis could survive and nodulate at pH a parts per thousand yen2.0, Acacia confusa and Melaleuca armillaris could survive at pH a parts per thousand yen2.5 but A. confusa nodulate at pH > 3.5. In the second phase, 12 plant species, in addition to A. auriculiformis, can survive in pH 2.0 media. No family or genus commonality in acid tolerance was found. Two of these tolerant species, i.e., A. auriculiformis and Jatropha carcas, could potentially be planted as an economically and ecologically viable option for acid mine remediation due to their potential function as biofuel feedstock.