Radioactive substances occur naturally in the environment and they emit small amounts of radiations. However, anthropogenic activities produce high levels of radioactive materials that are released into the environment causing pollution. The most common radioactive metals are Uranium, Plutonium, Polonium, Radium, Thorium and Cesium. Among these, Uranium is the most frequently and naturally occurring radioactive substance and possesses weak radioactivity properties. Therefore it is important to focus on mitigating its pollution and uranium bioremediation is one of them.
Air contamination is defined as the presence of toxins that affect the environment (Vallero 2011). India, as a rapidly developing nation, needs to manage its ecological issues well to minimise contamination of air, water and soil. The major factors for air pollution in the country are:
Mercury bioremediation processes as mercury occurs naturally in the environment and is found in both elemental inorganic and organic forms. It generally occurs in two oxidation states, Hg+1 and Hg+2, they are commonly found as:
- elemental mercury,
- mercuric chloride,
- mercuric sulfide (cinnabar ore),
- and methylmercury.
Textile dyes are artificial or natural substances used to dye fabric. Artificial dyes are one of the worst contributors to soil pollution as they contain mutagenic, cytotoxic, cancer and allergy causing properties (Khandare & Govindwar 2015). This is aggravated by the fact that the textile dye industry release by-products in the form of effluent, causing extensive pollution. However, existing physio-chemical technologies to clean up polluted water or soil are expensive and cause secondary problems in terms of disposal. Read more »
Bioremediation is a technology that ‘treats’ environmental pollution using microbes, plants or their by-products. It helps in removing xenobiotic and recalcitrant pollutants through physical or chemical methods. Pharmaceutical industry releases large quantities of recalcitrant pharmaceutical by-products. Additionally, farming and municipal wastes contribute to the pollution. Although pharmaceutical products are biologically active, they are non-biodegradable and recalcitrant in nature, which makes pharmaceutical pollution difficult to be rid of using conventional methods (1).
In the previous article, the hazards and possible solutions for lead and arsenic pollution from the perspective of bioremediation, were discussed. This article on the other hand, explores problems posed by chromium pollution in soil and the possibility of bioremediation as solution. It is well known that chromium metal exists in various forms in the environment, mainly as trivalent [Cr (III)] and hexavalent [Cr (VI)] cation. However, the water soluble hexavalent chromium is the most toxic form of the element with strong carcinogenic properties. Read more »
Arsenic is a heavy metal, known to occur naturally in the Earth’s crust, metal ores and sediments (both organic and inorganic forms). It is also found in the form of sulfides, oxides or salts of sodium, copper and iron among others. It exhibits different valences and is mostly encountered as trivalent Arsenite and pentavalent Arsenate, both of which are deemed toxic to humans (1). Naturally, this heavy metal enters groundwater from its natural geological bedrocks and also from arsenic rich geothermal fluids (2). However, human activities like smelting, extraction of metal, burning of petroleum, coal and wood, production of dyes, pharmaceutical industrial waste and pesticides, cause rampant arsenic pollution.
Soil is formed from the gradual breaking and weathering of rocks and covers of the landmass of earth as a thin layer. It is a complete ecosystem in itself and its maintenance is of utmost importance for the continuity of life processes of microbes, plants and animals. However, the quality of soil ecosystem is compromised due to increasing human activities resulting in release of pollutants. Furthermore, one such pollutant contributing to soil pollution is the discharge of high concentration of heavy metals (as shown in the figure below). Most noteworthy, Lead occurs most abundantly on Earth, constituting 0.002% of the total crust (1). This article discusses the need for Lead bioremediation in soil. Furthermore, the use of bio-remediation to mitigate the impact has also been discussed.