Anaerobic Degradation of Organochlorinated Pesticides DDT and Heptachlor in River Sediment of Taiwan
Chiu, Tzu-Chuan , Jui-Hung Yen, Tzu-Ling Liu, Yei-Shung Wang
Abstract
p,p’-DDT [1,1,1-trichloro-2,2-bis(4-chlorophenyl)-ethane] and heptachlor [1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetra-hydro-4,7-methanoindene] are of serious concern in countries because of the chemical stability, estrogen-like characters and potential toxicity on animal (Kirby et al. 2001). Several decades ago, DDT and heptachlor were widely used in the world to control insects and environmental pest. Due to high lipophilicity, residues of organochlorine pesticides were still detectable in soils, water, and sediments. (Abou-Arab et al. 1995; Sarkar et al. 1997; Yuan et al. 2001). Biodegradation is a very important mechanism for removal of organic chlorinated pesticides from environments. Under anaerobic conditions, microbial reductive dechlorination was thought to be the predominant process of excluding chlorine atom from chlorinated hydrocarbons, which are recalcitrant under aerobic conditions. The same characterizations were also found in our previous study on other persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) (Chen et al. 2001a; Chen et al. 2001b). A variety of organochlorine pesticide residues still exist in the river sediments in Taiwan (Doong et al. 2002). Therefore, to understand the ability of microbial degradation of organochlorine pesticides is quite useful in enabling bioremediation. The present research was designed to comprehend the anaerobic degradation of DDT and heptachlor in the river sediment by indigenous microorganisms of Taiwan. The effects of environmental factors were also investigated.