Reclamation of a Petroleum-Contaminated Calcareous Soil Using Phytostimulation

Soil contamination by hydrocarbons poses a threat to groundwater and food chains. Hence, the elimination of these compounds from contaminated soil is vital. In this study, we investigated the degradation of total petroleum hydrocarbons (TPHs) in the rhizosphere of tall fescue (Festuca arundinacea L.), agropyron (Agropyron smithii L.), safflower (Carthamus tinctorius L.), and sunflower (Helianthus annus L.) at three soil contamination levels, denoted as C0 (50 mg kg-1 TPH), C1 (40360 mg kg-1 TPH), and C2 (69760 mg kg-1 TPH). The dry matter yield decreased with increasing contamination level in all four plant species. Safflower seedlings grew poorly and died within 10 to 11 weeks at the highest contamination level. Soil microbial respiration rate increased by 77 and 80% in the rhizosphere soil of tall fescue and agropyron, respectively, in the C1 treatment as compared to the control. The TPH concentration decreased by 71 and 69% in the C1 treatment and by 45 and 42% in the C2 treatment in the rhizosphere soil of agropyron and tall fescue, respectively. Sunflower had no significant effect on the degradation of the contaminating petroleum hydrocarbons in comparison to plant-free control. According to these results, agropyron and tall fescue appear to be suitable choices for the phytoremediation of investigated petroleum-contaminated soils.