Simulating 2,4,6-trinitrotoluene (TNT) elimination in a pond inhabited by freshwater algae of the Rhizoclonium genus

Abstract

Military operations over large areas of Ukraine lead to release of explosives and their derivatives into the environment with subsequent accumulation in natural and artificial water bodies, which unwittingly serve as reservoirs for collecting pollutants from the catchment area. The need to restore aquatic ecosystems dictates the search for efficient, cost-effective and environmentally friendly methods for the elimination of explosives, which corresponds to the processes of biological treatment. In this work, we examined the ability of common freshwater algae of the genus Rhizoclonium to detoxify 2,4,6-trinitrotoluene (TNT) under model conditions of water pollution (at a TNT concentration of 100 mg/L). The exposure time of the algae to TNT was 48 hours, during which the content of TNT and nitrites in the aqueous medium was monitored, as well as the content of chlorophyll and the activity of glutathione S-transferase in plant tissues. 2,4,6-trinitrotoluene was extracted from the aqueous medium with toluene, followed by separation in a separatory funnel, removal of residual water with sodium sulfate, and reduction of the extract volume using a rotary evaporator. The decrease in the concentration of TNT, established by GC-MS technique, was 66.4% by the end of the experiment, while the content of nitrites increased almost 15-fold. In the algae cells, a threefold increase in the enzymatic activity was observed already in the second hour of exposure, followed by a gradual decrease and maintenance at a level of 50% of the control until the end of the experiment. The total chlorophyll content increased significantly from the sixth hour of exposure to the end of the experiment due to an increase in the content of chlorophyll b. The results obtained indicate the efficient biodegradation process and prospects of using algae of the genus Rhizoclonium for cleaning water bodies contaminated with TNT.