Research on rehabilitation of ancient oil polluted soil through perennial plant phytoremediation

On lands with ancient oil pollution, there remain, for a long time, those chemical compounds characterized by high molecular weight, non-polar nature, and low volatility. They cause the formation of soil aggregates soaked with crude oil. The aggressiveness of heavy petroleum polluted soil, manifested by the specific suffering of cultured plants and it ended in their death. To alleviate aggression of polluted soils, they were treated with a mixture of fly ash and sewage sludge (1:1 wt./wt.). The treatment applied of 50 t/ha on a soil with 8% oil products caused the adaptation of a perennial crops of the Lotus corniculatus species. In the first year
of culture, plants occupied 25–35% of the cultivated area. In the spring of the second year of crop, plants expanded and occupied up to 65% of the cultivated area. Maintaining the trefoil plants culture demonstrates the possibility to rehabilitate soils polluted with 8% oil products. The used phytoremediation variants are based on the common agricultural techniques, the application of fertilizer and fly ash adsorbent agents of petroleum products. Furthermore, the reduction with more than 50% in oil content in 0–20 cm soil profile during the monitored period of 12 months represents the motivation for using trefoil in order to ecologically rehabilitate ancient oil polluted land.