PHYTOREMEDIATION POTENTIAL OF Catalpa bignonioides IN CRUDE OIL-CONTAMINATED SOILS: EVIDENCE FROM DUHOK, KURDISTAN REGION

Phytoremediation is a promising method for cleaning crude oil-contaminated soils. This study aimed to evaluate the potential of Catalpa bignonioides seedlings for remediating soil polluted with 1% and 2% (w/w) crude oil. One- and two-year-old seedlings were grown for eight months under contaminated conditions. Plant growth parameters, crude oil degradation percentage, total petroleum hydrocarbons (TPH), soil pH, electrical conductivity (EC), organic matter (OM), and nitrogen (N), phosphorus (P), and potassium (K) levels in both soil and plant shoots were measured. The seedlings successfully grew in contaminated soil, with no plant mortality observed, despite some leaf yellowing and necrosis. Chlorophyll a remained unaffected, while chlorophyll b significantly decreased. Plant height, shoot and root biomass were significantly reduced at 2% oil concentration. Soil pH slightly decreased, while EC and OM increased with contamination. TPH analysis showed complete removal of 10 hydrocarbon fractions (C3–C8, C10–C14), with degradation rates ranging from 70.37% to 84.02%. Crude oil significantly affected soil N and P levels but not K; in plant tissues, only N was significantly altered. Two-year-old seedlings exhibited greater growth and higher N and K content than younger plants. These findings confirm the species’ potential for phytoremediation of crude oil-contaminated soils