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Persistence and Distribution of [14c] Malathion in Rice-fish Model Ecosystem

M. Rahman
Institute of Food and Radiation Biology Atomic Energy Research Establishment G.P.O. Box 3787, Dhaka-1000, Bangladesh

N. Islam
Institute of Food and Radiation Biology Atomic Energy Research Establishment G.P.O. Box 3787, Dhaka-1000, Bangladesh

J.A. Khatoon
Institute of Food and Radiation Biology Atomic Energy Research Establishment G.P.O. Box 3787, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

Study was conducted in model ecosystem with [¹⁴C] Malathion as tracer to determine the persistence and distribution of radioactivity in water, soil, fish and rice plant which are the major components of ecosystem. The half life (DT50) of malathion in paddy water was found to be only 9 days. Highest concentration was recorded on the 2nd day of the experiment and with progress of time dissipation occurred rapidly. By 14 days about 88% was dissipated from the water. Malathion applied to soil was found to be extractable by 96% on the first day and it was decreased to 41% on 90 days. Bound malathion in soil was found to be increased with time from about 4% to 58% by 90 days. In rice plant, highest concentration was contained in leaves followed by stem and then root. Malathion residues in fish was always higher in visceral portion than muscle. Highest concentration of residues 44% in muscle and 56% in viscera were found on 14 days.

Keywords: Persistence, Distribution, Malathion, Ecosystem

Location: Pesticide Residue Laboratory of Institute of Food and Radiation Biology, AERE, Savar, Dhaka.

Start Date: 15-02-1999

End Date: 15-05-1999

Program Area: Risk Management in Agriculture

Non-commodity: Performance

Objectives:

To determine the persistence and distribution of radiolabelled malathion in the four major components i.e. water, soil, plant and fish of rice model system under simulated field conditions.

Methodology:

Model ecosystem, Sampling and Analysis. In order to simulate an actual field conditions a micro ecosystem made of glass tank (90 x 45 x 50 cm) with 50 kg of soil in it was carried out at the Pesticide Residue Laboratory of Institute of Food and Radiation Biology, AERE, Savar, Dhaka. Soil was collected from rice paddy field which had not received any pesticide earlier. Stones, weeds, twigs and other debris were removed from the soil before treatment with 22.52 µCi (0.3 mg) of [¹⁴C]malathion plus 8.018 mg of non-labelled cold commercial formulation of malathion (Fyfanon 57 EC). Malathion was incorporated the soil at a rate of 1.2 L a.i.ha-1 . To prepare a homogenous solution, the cold formulation and radiolabelled compound in acetone were mixed in a volumetric flask. Acetone was further added to wash and stirred for 5 minutes by a vortex mixture. The mixed solution was transferred quantitatively in glass tank. The soil used was a clay type with organic matter content of 3.61% and pH 4.2. High yielding varieties of rice seedlings of one month old Oryaza sp. were transplanted into the glass tank with a gap of about 6-8 em from each Pond water was added and same water level 4 em above soil was maintained throughout the experimental period of 90 days. The tank was kept in an environment similar to that of the actual field. Under this condition, 25 catfishes (Heteropneustes fossilis) were released on the day of the experiment which was free from toxicity. A separate toxicity test was carried with cold malathion before starting this study and it was found that after 5 days of malathion no mortality of catfish was recorded.

Source of Information: Bangladesh J. Agril. Sci. 27(1): 105-110, January, 2000

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From this study, it was found that malathion applied in the paddy water, soil, fish or rice plants were not persistent. Fish (Heteropneustes tassilis) could be released in malathion treated field after 5 days of application and by 9 days half of the applied concentration of malathion in water was found to be lost.

Knowledge Management: Journal