Effect of vermicompost on biotransformation and bioavailability of hexavalent chromium in soil

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 without 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.