Abstract
Mandor Village has developed as a tradisional gold mining area since years ago. It involved activities that have led to extreme land condition and the release of mining residues, i.e., mercury, to the soils. The study examined the potential of soil bacteria as mercury bioremediation agent based on their population and activity in former mines with different ages. The bacterial population was measured by isolating soil bacteria on solid media using the pour plate method, and the colonies were enumerated during the incubation. The Nutrient Agar (NA) medium was used to obtain the total population, whereas the Salt Base Solution (SBS) was to determine the presence of mercury-tolerant bacteria. The addition of HgCl2 affected the number of the colonies. The colony only grew until the concentration of HgCl2 reached 5 mg/l, and the total colony was larger in older mines. The observation of bacterial activity showed that biotransformation performance was lower when the concentration of mercury was the same as its natural presence in soils (0.1-0.5 mg/l) compared with higher mercury level (1 mg/l). The research showed that lower mercury concentrations in nature reduced the natural ability of bacteria to transform pollutants. This study provides information that can assist the development of a technological approach to control mercury pollution in former traditional gold mines in an environmentally friendly manner using indigenous soil bacteria.
Highlights
The traditional gold mining activities conducted by the community in Mandor Village, Landak Regency, West Kalimantan Province, known as PETI (Penambangan Emas Tanpa Ijin― Unlicensed Gold Mining), changed the physical, chemical, and biological characteristics of the soil in the environment
Based on the microscopic observations of the cells, the entire colony in this research was red and Gram-negative. These results are in line with Nofiani & Gusrizal (2004), which examine the narrow spectrum of the mercury-resistant bacteria in former PETI at the same location
In old mining sites (t>10 years), have the potential to transform mercury that is present with higher concentrations than its natural level in soils (
Summary
The traditional gold mining activities conducted by the community in Mandor Village, Landak Regency, West Kalimantan Province, known as PETI (Penambangan Emas Tanpa Ijin― Unlicensed Gold Mining), changed the physical, chemical, and biological characteristics of the soil in the environment. Mercury is the most dangerous contaminant disposed to the environment, yet miners still use it as a gold binder to separate gold from sand and soil. As a result of mining activities, changes in soil characteristics like temperature, pH, nutrients, minerals, and heavy metal concentration, potentially affect the number and activity of soil microorganisms. This microbial parameter is a potential indicator in monitoring heavy metalcontaminated soil through two ways: first, by measuring the population size of the microbes and, second, by assessing their activity in removing the pollutants (Ghorbani et al, 2002). Good soil quality is characterized by a high level of microbial diversity (Sarma et al, 2010)
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