IOSR Journal of Agriculture and Veterinary Science (IOSR-JAVS) e-ISSN: 2319-2380, p-ISSN: 2319-2372. Volume 5, Issue 3 (Sep. - Oct. 2013), PP 34-40 www.iosrjournals.org www.iosrjournals.org 34 | Page Effect of vermicompost on biotransformation and bioavailability of hexavalent chromium in soil Sunitha Rangasamy 1* , Bharani Alagirisamy 1 , Gayathri Purushothaman 2 and Mahimairaja Santiago 1 1 Department of Environmental Science, Agriculture College and Research Institute, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu 641 003, India. 2 Department of Biotechnology, Indian Institute of Technology, Karagpur, West Bengal, India. Abstract: Chromium is released into the environment by a number of processes such as steel manufacturing, pulp processing, wood preservation, leather tanning, metal plating, metal cleaning and processing and alloy formation, mostly with-out proper treatment. As a consequence, elevated concentrations of chromium become a major threat to the environment. Among the different forms of chromium, hexavalent chromium is highly soluble in water, and mutagenic and carcinogenic. Recently, concern about Cr as an environmental pollutant has been escalating due to its build up to toxic levels in the environment as a result of various industrial and agricultural activities. In the present study, the hexavalent chromium was reduced into trivalent chromium from chromium contaminated (300 µg g -1 ) soil. The vermicompost and microbial cultures (Pseudomonas fluorescens and Trichoderma viride) were used for chromium detoxification studies. The chromium (VI) reduction was observed in best treatment like vermicompost alone reduced the chromium up to 85 per cent and vermicompost along with Pseudomonas fluorescens reduced the hexavalent chromium up to 84.6 per cent. The large amount of hexavalent chromium was detoxified due to application of vermicompost. The chromium hexavalent reduction was confirmed with maize plant uptake. The plants grown on the control soil (T 1 ) had the highest content of Cr (39.2 µg g -1 ) and the plants grown on the soil with the application of Trichoderma viride (T 9 ) had the lesser value of Cr content. These biological materials were reduced the toxicity of chromium and bioavailability to the maize plant uptake. Key words: Bioremediation, biotransformation, Cr (VI), Vermicompost, Pseudomonas fluorescens I. Introduction In recent years, contamination of the environment by Cr, especially hexavalent Cr, has become a major area of concern. Chromium is used on a large scale in many different industries, including metallurgical, electroplating, production of paints and pigments, tanning, wood preservation, Cr chemicals production, and pulp and paper production. Often wastes from such industries (e.g., sludge, fly ash, slag, etc.) are used as a fill material at numerous locations to reclaim marshlands, for tank dikes, and for backfill at sites following demolition (Salunkhe et al., 1998). At many such sites, leaching and seepage of Cr (VI) from the soils into the groundwater poses a considerable health hazard. The tanning industry is an especially large contributor of Cr pollution to water resources; Chandra et al. (1997) estimated that in India alone about 2000 to 3200 tones of elemental Cr escape into the environment annually from the tanning industries, with a Cr concentration ranging between 2000 and 5000 mg L −1 in the effluent compared to the recommended permissible limit of 2 mg L −1 . Increasing levels of heavy metals in the environment pose serious threats to water quality, soil ecosystem, human health and living organisms (An et al., 2001; Wingenfelder et al. 2005; Vinodhini and Narayanan, 2008). Cr, Ni, Zn, Cu and Cd are considered as priority metals from the point of view of potential health hazards to human. Hexavalent chromium has high toxicity for humans and animals (McBride 1994; Ayuso et al., 2003; Babel and Opiso, 2007) and commonly interferes with beneficial use of effluents for irrigation and industrial applications. They are also the groundwater contaminants at industrial installations (Mier et al., 2001; Malakootian et al., 2009). In epidemiological studies, an association has been found between exposure to Cr (VI) by the inhalation and lung cancer. IARC has classified chromium (VI) in Group 1 (human carcinogen) (WHO 2004). Some cities in Iran have high amount of hexavalent chromium contents in ground water resources. Conventional method for industrial effluent treatment is physicochemical treatment including ion exchange, vacuum evaporation, solvent extraction and membrane technologies (Applegate 1984; Sengupta and Clifford 1986; Kentish and Stevens 2001). Among these, ion exchange is one of the most effective and economical methods (Tran et al., 1999; Nameni et al., 2008). Use of various sorbents such as bentonite (Zvinowanda et al., 2009), chitosan (Jha et al., 1988), perlite (Mathialagan and Viraraghavan 2002), coal (Karabulat et al., 2000), and activated carbon (Fan and Anderson 2005; Gueu et al., 2007) have been reported