Characteristics of Sediment Heavy Metal Levels in Lead-zinc Ore Cho Don District Area, Bac Kan Province, Vietnam

Vietnam is a country with diverse and abundant mineral resources with nearly 5000 mines and ore spots of about 60 different minerals. Mining and processing of mineral resources have contributed about 9.6-10.6% of the country's GDP since the year of 2000. However, the exploitation and processing of mineral resources have been leading to a certain soil and sediment contamination by heavy metals. Soil and sediment samples around lead-zince mines have been collected and analyzed for Cu, Zn, As, Cd, Hg, Pb and Ni in Cho Don district, Bac Kan province, Vietnam. Single pollution, geoaccumulation and enrichment indices have been used for assessing the sediment quality in terms of heavy metals by comparison with threshold and ecological risk limits. High concentration of Cu and Zn in the sediment is due to extremely high content of the two metals in the ore-surrounding soil in the lead-zinc mines, i.e. high background values. High concentration of As and Cd in the sediment is affected in a greater extent by high content of the two metals in the ore-surrounding soil in the lead-zinc mines, and in a lesser extent by contamination due to geoaccumulation and enrichment. High Pb concentration in sediment is affected in a greater extent by high content of the metal in the ore-surrounding soil in the lead-zinc mines, and in a lesser extent by contamination due to geoaccumulation and enrichment. The pollution sequence based on an average single pollution index is Pb(125.76) > As(55.48) > Zn(26.82 > Cd(14.17) > Cu(5.08) > Ni(1.36) > Hg(0.42), while based on the average geoaccumulation index, the sediment is mostly uncontaminated with the sequence Cd(1.1) > As(0.7) > Cu, Zn, Hg, Pb, Ni(<0). However, a significant to an extremely enrichment of some metals is observed with the following sequence based on the average enrichment factor Cd(4.8) = As(4.8) > Hg(4.1) > Pb(1.4) > Cu(0.9) > Ni(0.6). The results highlight the need for a comprehensive and detailed study program on heavy metal content in different soil and sediment resources to identify the magnitude and details of the problem associated with heavy metal contamination for development of a remediation plan and more effective pollution preventing measures including technology develop for recovering of useful components.