Qualitative and quantitative analysis of organochlorine insecticide residues were conducted in water, sediment, aquatic plants and animals from 3 freshwater reservoirs. Ninety water samples, 90 sediment samples, 397 aquatic plants samples and 121 aquatic animals samples were collected during March-April and August-September 1989. There were about 14 kinds of aquatic plants, such as water hyacinth, water lettuce, algae and water lilly etc. Aquatic animals are fish, shrimps and snails, but most of them are fish. They are striped snake-head fish, carp and catfish etc. Total samples of 698 were analyzed by using gas chromatographic techniques at Agricultural Toxic Substances Division. The results indicated that 5 kinds of insecticides were found in most samples. They were lindane, heptachlor, aldrin, dieldrin, DDT and derivatives. Dieldrin was detected at higher concentration and found in all samples. The residue level of dieldrin ranged from 0.01-0.12 ppb in water, 0.005-0.036 ppm in sediment, 0.001-0.138 ppm in aquatic plants and 0.001-0.037 ppm in aquatic animals respectively. The accumulation of dieldrin residue in water and aquatic plant samples from all reservoirs are not different but the level of dieldrin residue in sediment samples from Bueng Boraphed is higher than the other 2 reservoris. However the levels of dieldrin residue in sediment, aquatic plant and aquatic animal samples higher than those in water samples respectively.

Species composition of algae and aquatic plants in Bung Si Phi swamp were investigated during February to July 1985. The samples were collected randomly 3 times in February, April and July respectively. Thirty-five species of algae and seven species of aquatic plants were observed. Closterium sp., Cosmarium sp., Mougeotia sp., Onychonema sp., Pediastrum sp., Tetraedron sp., Anabaena sp., Oscillatoria sp., and diatom were dominant species of algae population while Ceratophyllum demersum, Hydrilla verticillata and Najas minor were dominant species of aquatic plant and occupied major area of the swamp. The proximate analysis of Spirogyra sp. showed 12.81 percent of protein nitrogen content by dry weight. The protein contents of aquatic plants ranged from 10.79 to 13.99 percent by dry weight.