Summery

This research was carried out in the laboratories and glass house of the College of Science, University of Salahaddin- Erbil during September 2021 to May of 2022 to apply four ex-situ techniques for remediation of drill cutting soil, including physical remediation by using (UVC-260nm) radiation, chemical remediation by using (hydrogen peroxide), nano-remediation by using zero valence iron nanoparticle (nZVI) and phytoremediation for clean-up of the polluted soil. The experimental design was based on factorial completely randomize designs including two factors.  For each technique the first factor was involved five different exposure times to UVC, four different times of exposure to hydrogen peroxide (0,12,24,48) hrs. five different concentrations (0, 0.2, 0.4, 0.6, 0.8) of zero valence iron nanoparticle (nZVI) and the second factor in all applied techniques involved the studying sites.

Five evergreen plant genera including Dodonaea viscosa L., Myrtus communis L., Ficus benjamina L. and Platycladus orientalis L., Cupressus Sempervirens were used for phytoremediation techniques.

 The summary of the main results is presented as follow:  

1. Statistical analysis of heavy metals and total petroleum hydrocarbon showed significant variance between both sites after UV application. The minimum value of heavy metals (Pb, Ni, Cr and Cd) was (84.82, 014, 1.09 and 0.023) mg.kg^-1. However, the minimum values of (C8-C24, C24-C40 and TPHs) were (314.54, 84.87, 427.68) mg.kg^-1.
2. The exposure time to UV was significantly affected the concentration of heavy metals and TPH, the lowest values were (1344.323, 2.872, 0.260 and 11.639) mg.kg^-1 for heavy metals (Pb, Ni, Cd, Cr) in drill cutting soil were recorded in (T5, T3, T2 and T4). While the lowest values of TPH were (238.15, 74.20 and 312.35) ppm for (C8-C24, C24-C40 and TPH) that recorded in (T5).
3. The combination between exposure time to UV and sites was significantly affected on the concentration of heavy metals and TPH. The lowest values of heavy metals were (1174.135, 1.173, 0.174 and 8.526) mg.kg^-1 for (Pb, Cd), (Ni) and (Cr) that recorded in combination treatment (S2T4), (S2T1) and (S1T3) respectively.
4. The result also showed significant negative correlation between concentration of (nZVI) and concentration of heavy metals in drill cutting soil.
5. The exposure time to hydrogen peroxide significantly affected on the concentration of heavy metals. The lowest values were (1359.75, 4.25, 14.5 and 0.23) mg.kg^-1 for the heavy metals (Pb, Ni, Cr) that recorded from (T2) except (Cd) was recorded by treatment (T4).
6. The combination between time of exposure to hydrogen peroxide and sites significantly affected on the concentration of heavy metals. The minimum values were (1175.188, 1.17293, 0.13541 and 8.09023) mg.kg^-1 for heavy metals (Pb, Ni, Cd and Cr) that recorded from combination treatment (S2T3, S2T1, S1T4 and S1T2) respectively.
7. Statistical analysis of heavy metals for hydrogen peroxide showed significant variation between both sites. The minimum values were (86.42, 0.22, 1.07) and (0.023) mg.kg^-1 for heavy metals (Pb, Ni, Cr) that recorded from (S2) except (Cd) which was recorded from (S1).
8. The evergreen plants were halted in the drill cutting soil due to the physicochemical properties of the studied soil particularly the higher EC value.
9. Statistical analysis of heavy metals and TPH for (nZVI) show significant variation between both sites. The minimum values were (94.594, 0.115, 1.368) and (0.030) mg.kg^-1 for heavy metals (Pb, Ni, Cr) that recorded from (S2) except for (Cd) which was recorded from (S1).
10. The combination between sites and concentration of (nZVI) was significantly affected the concentration of heavy metals and TPH. The lowest values were (1369.891, 1.131, 0.226 and 15.942) mg.kg^-1 of heavy metals (Pb, Ni, Cr and Cd) that recorded in the combination treatments (S2C4, S2C1, S2C5 and S2C3) respectively.
11. The concentration of (nZVI) significantly affected the concentration of heavy metals and TPH. The lowest values were (1424.511), (2.155) and (0.286, 19.414) mg.kg^-1 for the heavy metals (Pb), (Ni) and (Cd, Cr) were recorded from treatment (C4), (C2) and (C5) respectively. However, the lowest petroleum hydrocarbon values were (218.65, 707.88) and (81.3750) ppm for (C8-C24, TPH) and (C24-C40) were recorded from (C5) and (C4).