Acid mine drainage and heavy metals contamination of abandoned and active mine site at Old Repas Dam in Bentong, Pahang, Malaysia

Abstract

Acid Mine Drainage (AMD) occurs as a result of mining activities during mineral exploration. Interaction of the minerals in the presence of atmospheric oxygen and water produces AMD as an end product. AMD can also be produced by weathering of sulphide minerals through series of process, which includes oxidation and hydrolysis. The main aim of the study is to determine the presence of Acid Mine Drainage (AMD) and contamination of the active and abandoned mining sites with heavy metals in Bentong Pahang. This study deals with the identification of heavy metal toxins traces in water bodies that result in discoloration of the water catchment, downstream of the Old Repas dam. Any discoloration of the water present proves the occurrence of AMD. In order to have better comprehension of the scenario, site reconnaissance and survey is carried. This is to examine the areas affected and thus recognising two different sampling points that have traces of AMD contamination. Water sampling and testing are carried out in the chosen sampling point using four in-situ parameters and five selected heavy metals. The chosen parameters are water pH, dissolved oxygen content, total dissolved solids and ammoniacal nitrogen. The selected heavy metals are Zinc, Lead, Tin, Mercury and Arsenic. Four samples were collected each from two sampling point on two different sampling days. In addition to that, the surface water with sediments was also collected and analysed for the presence of heavy metals. From the results, it was found that the pH of the sampling point was ranging from 5 to 7 indicating the presence of AMD, which is the major finding in this study. Based on the heavy metal analysis, it was found that the concentration of Pb, Sn, Hg, As & Zn was present in greater than the allowable standard limits for treated water by the Malaysian Ministry of Health. This concludes an urgent intervention required to treat the site to prevent any further environmental deterioration.