Characterization of Nickel and Gold Mined-out Areas of Taganito Mining Corporation and Manila Mining Corporation, Claver and Placer, Surigao del Norte, Philippines

Mining industries are mandated by law to rehabilitate their mined-out areas. The waste materials, also called as mine tailings are left after the extraction of minerals have caused several environmental problems such as contamination and alteration of soil profiles, and the pollution and contamination of waterbodies. Experience in the Philippines indicates that mining companies are facing major difficulties in rehabilitating mined-out areas and tailings especially in raising potential nursery seedlings. Much more in outplanting raised nursery seedlings since mortality rates are high. The mined-out areas facing such problems are the nickel and gold mined-out areas in Taganito Mining Corporation (TMC) and Manila Mining Corporation (MMC) located in Claver and Placer, Surigao del Norte, respectively. This study assessed and characterized a cross section of their mined out areas in terms of the amount of residual heavy metal concentration in the soil, determine the current soil nutrient status and provide useful implications of the current physico-chemical properties of the mined-out soils. Results show that the soils in both sites need to be amended with compost (1:1 ratio), fertilizer (NPK) and microbial biofertilizers to ensure success in the rehabilitation efforts. TMC soils have deficient to low nutrient availability (%organic matter, total nitrogen, available P and exchangeable K) and have high nickel (7,166 ppm) content which is an order of magnitude higher than the Dutch standard intervention value of 210 ppm. On the other hand, MMC soils have low to moderate nutrient availability and a pH value of 6.14. Additionally, MMC soils have high concentration of molybdenum and copper with 39, 400 ppm and 449.2 ppm, respectively which extremely exceeded the Dutch standard intervention value of 200 ppm (molybdenum) and 190 ppm (copper). These values indicate serious contamination of soils and immediate remediation is highly recommended. It is likewise further recommended the use of native soils with biofertilizer amendments in the much needed seedling production for the massive rehabilitation efforts of these mining companies. Use of native plant species for nursery seedling production is highly recommended to be used in the rehabilitation efforts to ensure better coping mechanism and higher rates of survival when introduced into the mined-out soils. Bioremediation is highly recommended as a rehabilitation strategy in the mined-out areas of Taganito Mining Corporation and Manila Mining Corporation in Claver and Placer, Surigao del Norte, respectively. This method is environment-friendly, low-cost, a simple technology and ensures long-term solution in mined-out area rehabilitation.