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INTRODUCTION:
OCCURANCE OF CHROMIUM:
Chromium is a heavy metal which is considered as an environmental pollutant (Nafish et al, .2012). It is 7th most occurring element on earth and its average concentration in the earth is about 100mg/kg. (Panda and Choudhory, .2005). Apart from its importance chromium causing serious hazards for those organisms and plants that are exposed to the chromium in polluted areas of high concentrations. Being highly toxic metal it mainly comes from leather tanning, textile and electroplanting industries (Stern, 1982).As a result of smelting process, chromium is also found in air as aerosol. (Kimbrough et al., 1999). By the use of water wastes and industrial effluents, soil pollution is increasing day by day due to chromium contaminants present in the soil usually in urban areas (Mushtaq & Khan, 2010).
Chromium occurs in different oxidative states like trivalent Cr (III) and hexavalent chromium Cr(VI). Both these states differ in different aspcets like mobility,bioavailabilty and toxicity (Shanker et al,.2005;Panda and Choudhory ,.2005). Toxic effects of chromium highly depend on the different states of the oxidative states. As the solubility and toxicity of the trivalalent chromium Cr+3 form is less than hexavalent chromium Cr+6 form ( Pandey and Sharma,. 2003).
Hexavalent chromium is converted to trivalent chromium when it reacts with matter of organic nature, Fe (II), and sulfides and this is facilitated by the manganese oxides. (Becquerel et al, 2003). Hexavalent chromium is easily available for living organisms because it is more soluble in water than trivalent chromium (Shrivastava et al,. 2002).Plants can grow well when there is less amount of chromium in the environment whether in case of high concentration of chromium it is carcinogenic to plants and animals (Shanker et al., 2005).At low concentration trivalent chromium is not as much harmful for the plants but when the concentration of the trivalent chromium is
OCCURANCE OF CHROMIUM:
Chromium is a heavy metal which is considered as an environmental pollutant (Nafish et al, .2012). It is 7th most occurring element on earth and its average concentration in the earth is about 100mg/kg. (Panda and Choudhory, .2005). Apart from its importance chromium causing serious hazards for those organisms and plants that are exposed to the chromium in polluted areas of high concentrations. Being highly toxic metal it mainly comes from leather tanning, textile and electroplanting industries (Stern, 1982).As a result of smelting process, chromium is also found in air as aerosol. (Kimbrough et al., 1999). By the use of water wastes and industrial effluents, soil pollution is increasing day by day due to chromium contaminants present in the soil usually in urban areas (Mushtaq & Khan, 2010).
Chromium occurs in different oxidative states like trivalent Cr (III) and hexavalent chromium Cr(VI). Both these states differ in different aspcets like mobility,bioavailabilty and toxicity (Shanker et al,.2005;Panda and Choudhory ,.2005). Toxic effects of chromium highly depend on the different states of the oxidative states. As the solubility and toxicity of the trivalalent chromium Cr+3 form is less than hexavalent chromium Cr+6 form ( Pandey and Sharma,. 2003).
Hexavalent chromium is converted to trivalent chromium when it reacts with matter of organic nature, Fe (II), and sulfides and this is facilitated by the manganese oxides. (Becquerel et al, 2003). Hexavalent chromium is easily available for living organisms because it is more soluble in water than trivalent chromium (Shrivastava et al,. 2002).Plants can grow well when there is less amount of chromium in the environment whether in case of high concentration of chromium it is carcinogenic to plants and animals (Shanker et al., 2005).At low concentration trivalent chromium is not as much harmful for the plants but when the concentration of the trivalent chromium is