Potential of three plant species for phytoremediation of oil-contaminated soils in northern conditions

The aim of this work was to assess the potential of three plant species (Brassica juncea L., Trifolium repens L., Agrostis stolonifera L.) for phytoremediation of oil-contaminated soils. The germination time of seeds and their survival rate after sowing into the model oil-contaminated soil were found. The influence of the procedure of encapsulation of seeds in alginate gel was assessed. Green manure plants seeds are preferably added after 30 days of self-cleaning of the soil due to the absence of a continuous oil film and restoration of air exchange. Brassica juncea L. was found to have the shortest germination time, at the same time the encapsulation of seeds in a polymeric complex increased the time for the develop-ment of vegetative organs. The encapsulation of T. repens L. and A. stolonifera L. seeds in alginate gels, on the contrary, reduced the germination time. A. stolonifera was also found to be more drought-resistant. It was concluded that the use of an auxiliary gel coat is most effective for small plant seeds and increases the survival rate on oil-contaminated soil.The contribution of the green manure plants root rhizosphere to the processes of biochemical transformation of oil was assessed by comparing such diagnostic indicators of the state of the soil as the activity of dehydrogenase and urease. The dehydrogenase activity in all versions of the experiment was higher than in the oil-free soil. Moreover, for T. repens and A. stolonifera the values were 20-25% higher than in the contaminated soil without plants. The urease activity also increased, however, in the experiments with plants it was less than in the control experiment with the oil. In general, the selected plants can act as green manures for the accelerated formation of phytomass and restoration of species diversity on the recultivation territories.