STUDY OF THE EMISSION OF METHANE FROM THE RICE FIELDS AND WETLANDS OF BANGLADESH AND ITS INHIBITION BY ORGANOMETALLIC COMPLEXES SYNTHESIZED FROM NEEM TREE LEAVES EXTRACTS

Abstract

The concentration of Methane in Earth's atmosphere is reported to be inoreasing on the basis of the results obtained by means of a variety of independent measurements attributed to the emission from rice growing regions. To understand the global budget of atmospheric methane, intensive research on individual methane sources are required to be investigated and integrated for arriving at a definite conclusion. Attempts have, therefore, been made for measuring methane emission from different rice fields of different places in Bangladesh. Methene emission observed were of highest magnitude in the last 2-3 weeks before harvest. Hourly emissions have been observed to be 27.21 mg. m"2hr_1 and the emissions have been found to vary with the paddy varieties, geographical location, soil group, soil texture and structure, soil temperature, soil pH, ambient temperature and various other factors.Effect of different parameters on methane effluxes have been discussed. A correlation of plant growth on methane emissions has been formulated. In order to study the mitigation measures for the suppression or reduction of methane emission from the rice fields, investigations with the natural pesticides were carried out in the laboratory and then applied in the field experiments. For this purpose the extracts of Neem tree components (Azadirachta Indica) and some metalcomplexes of the extracted components were used. Petroleum ether, EtOAc, MeOH and also aqueous extracts of AZADIRACHTA INDICA leaf showed insecticidal effect towards house flies while petroleum ether extract exhibited only repelling effect against mosquitoes and insecticidal effect on lice. Attempts were made to effect complexation of the extracts with metal ions like Ni(II), Cu(II) and Zn(II) and the extracts were subjected to chromatography to yield a number of compounds. The IR spectral data of these compounds have been discussed. In the laboratory experiments the extracts was found to be effective