Persistence And Accumulation Of Organochlorine Pesticides Inselectedcocoafarms In Southwestern Nigeria

ABSTRACT

Organochlorine Pesticides (OCPs) are cyclic chlorinated hydrocarbons that are toxic and can bioaccumulate in the environment. Although, its usehas been prohibited in many countries including Nigeria; nevertheless they are still used extensively for pests control by cocoa (Theobroma cacaoL.) farmers in Nigeria. In addition, OCPs residual concentrations among other factors in cocoa bean influences their price in the World market. Therefore, this study was designed toassess the persistence of OCPs in cocoa plants, soil, surface water, and sediments in selected cocoa farms in Southwestern Nigeria. The cocoa farms selected for this study were classified as; farms where OCPs have been used and discontinued for 15 years [Cocoa Research Institute of Nigeria, Ibadan [(CRIN (I&II)]; for 3–5 years (Sabo, Ondo); still in use [(Igba, Ondo) and (Sore-Bale, Ogun)]. Sampling was carried out during wet and dry seasons between November, 2009 and September, 2011. A total of 480 samples were randomly collected comprising: 120 soils [(0-15 and 15-30 cm), (CRIN I&II-48; Sore-Bale-24; Sabo-24; Igba-24)]; 60surface water (CRIN I&II-24; Sore-Bale-12; Sabo-12; Igba-12); 60 sediments (CRIN I&II-24; SoreBale-12; Sabo-12; Igba-12); 60 each of leaves, bark, pods and seeds (CRIN I&II-24; SoreBale-12; Sabo-12; Igba-12, per matrix)for analysis. Control samples were collected 5.0 km from CRIN I, where OCPs were not used. Terrestrial Field Dissipation (TFD) and adsorption-desorption studies for OCP were done by EPA/OECD methods using endosulfan (6,7,8,9,10,10-Hexachloro-1,5,5a,6,9a-hexahydro-6,9-methano,2,4,3- benzodioxathiepin-3-oxide). Extractions and clean-up of OCPs were done using standard analytical methods. TheOCPs were determined using Gas Chromatography-Mass Spectrophotometric (GC-MS) technique. Data were compared with WHO/FAO limits and analysed using correlation and descriptive statistics.