Phytoremediation potential of sorghum bicolor for soil decontamination from oil hydrocarbons and heavy metals

Abstract

The results of vegetation experiments carried out over 12 of years in order to assess the application of Sorghum bicolor (L.) Moench) for soil clean up from oil hydrocarbons and heavy metals in the Saratov Region are given. It was found that the cultivation of sorghum in contaminated soils under controlled conditions for 2 to 4 months led to the elimination of hydrocarbon pollutants by 21-98%. The decrease in the concentration of oil and oil sludge occurred primarily due to the reduction of the content of paraffins and naphthenes fractions. The degradation of diesel fuel and of phenanthrene as an individual polycyclic aromatic hydrocarbon was most successful. The role of the plant in the manifestation of the rhizosphere effect and of the pollutant detoxification was suggested to be based on the coupled plant-microbial metabolism of pollutants in the rhizosphere. The high extracting activity of sorghum towards heavy metals such as cadmium and nickel was revealed. Sorghum plant can accumulate up to 1003 mg of metals per kg of dry biomass. It was shown that cadmium predominantly accumulated in the sorghum roots. High concentrations of nickel accumulated in the plant shoots. Special attention is paid to phytoremediation of mixed pollution of soil with hydrocarbons and metals. A significant mutual influence of petroleum hydrocarbons and heavy metals on their elimination from soil has been established. The presence of organic pollutants reduces cadmium and nickel extraction capacity of sorghum. In contrast, cadmium increased the degradation of oil sludge. The data obtained emphasize the need for more detailed studies of the mutual influence of the components of mixed pollution in order to understand and predict the cleaning up processes in the environment. In general, taking into account the economic and biological characteristics of sorghum crops, it was concluded that the application of sorghum is promising for phytoremediation of contaminated soil in the Saratov Region.