Effect of Seaweeds on Degradation of DDT in Soils

Seaweed was investigated as an amendment to enhance remediation of 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (DDT)-contaminated soil. Under anaerobic conditions, the addition of seaweeds increased DDT degradation between 61 % and 88 % of the original concentration after 14 days of incubation whereas only 33 % of DDT was degraded in unamended soil. DDT was degraded to metabolites such as 1,1-dichloro-2,2-bis (p-chlorophenyl) ethane (DDD), 1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene (DDE), and 1-chloro-2,2-bis (p-chlorophenyl) ethylene (DDMU). Seaweed-amended soils converted 35–56 % of DDT to DDD while the unamended soil formed only 15 % DDD. Seaweed amendments modified soil conditions which include soils’ dissolved organic carbon (DOC), ionic strength, redox potential, and pH. These significant physicochemical changes influenced the increase in DDT bioavailability and transformation in seaweed-amended soils compared to the unamended soils. Multiple linear regression analysis also suggested that factors such as DOC, calcium, redox potential, and pH are involved against DDT degradation (p = 0.02).