Brassica Juncea (L.) Czern. (Indian Mustard): A Potential Candidate for the Phytoremediation of Mercury from Soil

Soil contamination caused by the deposition of mercury (Hg) is a global problem. Hg is released to the environment through the coal burning in thermal power plant and various anthropogenic sources and contaminates soil. Hg is taken up by plant roots from contaminated soil and transferred to aerial parts. Through bioaccumulation in the plant, Hg moves into the food chain, resulting in potential health and ecological risks. Coal combustion in thermal power plants is the major anthropogenic source of Hg in environment and India emits approximately 240 tonnes/year (in year 2010--2013). Indian coals are reported to have higher Hg contents than coals from other countries, with values ranging from 0.11 to 0.80 mg/kg. The world average Hg concentrations reported in coal and fly ash are 0.01--1 and 0.62 mg/kg, respectively. The mass of Hg accumulated globally in the soil is estimated to be 250--1000 Gg (1 Gg = 1000 tonnes). Phytoremediation method has been proved to be the best approach for removal of Hg from soil because this method is environmentally friendly and cost effective. The objective of this study was to investigate the efficiency of Brassica juncea plant for the removal of Hg from contaminated soil. A laboratory-scale pot study was conducted by spiking the Hg using solution of HgCl₂ in three different concentrations (10, 50, and 100 mg Hg/kg of soil). B. juncea was grown for 90 days and plant samples were collected after the exposure of 30th, 60th, and 90th days. Hg uptakes in plant (roots, shoots and leaves) and soil were digested as per USEPA standard methods and measured in Coal Vapor AAS.