Application of fish scale derivatives in ameliorating the phytotoxicity effects of multi-metal contaminated soil on paddy rice

Immobilization is an efficient method in the remediation of heavy metal-polluted soils. A greenhouse experiment was conducted to investigate the influence of fish scale powder, chitin, and chitosan on the growth and chemical composition of rice grown on a soil contaminated with Zn, Pb, Cd, and Ni. Results showed that the application of fish scale powder, chitin, and chitosan significantly increased root and shoot dry matter yield of rice, but decreased Pb phytoextraction efficiency. Further, the translocation factor of Ni decreased following the application of fish scale powder and chitosan. Application of fish scale powder decreased Ni, Cd, Zn, and Pb bioavailability in soil. The addition of chitosan caused 56% decrease in shoots Ni concentration as compared to control. Among different amendments, only the application of chitosan had a significant effect on the reduction of Zn content in rice root by 70% as compared to control. Considering that the translocation factors were less than one in all treatments, it can be concluded that biostabilization of the studied metals has occurred. Based on the obtained results, fish scale derivatives including fish scale powder and chitosan play an important role in the removal of heavy metals due to having suitable functional groups. Therefore, it can be deduced that due to the economic feasibility, environmentally friendly, and high metal removal capability of chitosan and fish scale powder, these two amendments are highly recommendable to be applied in multi-metal polluted soils for increasing metals removal and hence decreasing their phytotoxicity.