Organochlorine compounds in a Brazilian watershed with sugarcane and intense sediment redistribution.

Until 1985 persistent organochlorine compounds such as aldrin [(1alpha,4alpha,4abeta,5alpha,8alpha,8abeta)-1,2,3,4,10,10-hexachloro-1,4,4a,5,8,8a-hexahydro-1,4:5,8-dimethanonaphthalene] and heptachlor (1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methano-1H-indene) were recommended and used as insecticides on a large scale in sugarcane (Saccharum officinarum L.) cropping in Brazil. The environmental impact of these applications was not investigated in the past neither prior to nor after their restriction of use in Brazil. In a case study conducted during 1999, organochlorine insecticides were investigated in soils, colluviums, submerged sediments, and organisms in a watershed located in a traditional sugarcane-growing region in the southeastern region of Brazil. The results indicated that past applications of organochlorine insecticides (prior to 1985) do not represent an environmental threat at the present time. Most insecticides applied in the past were not detected or were present only in amounts that were below the detection limit. The organochlorine compounds lindane [(1alpha,2alpha,3beta, 4alpha,5alpha,6beta)-1,2,3,4,5,6-hexachlorocyclohexane] and heptachlor that remained on the market after 1985 for purposes other than for soil application were still detectable in significant amounts in soils, sediments, and soil organisms (heptachlor in form of the epoxide metabolites). This may suggest that these residues were originated from applications after 1985. These compounds showed a capacity for accumulation in sediments and soil organisms. The enrichment ratio from soils to sediments was 2 to 3 times and from soils to organisms up to 20 times.