METHANE EMISSIONS FROM WATER-HYACINTH-INFESTED FRESH-WATER ECOSYSTEMS

Methane emission from waterhyacinth was studied under natural, laborat ory and greenhouse conditions. The emission rate varied between 6 and 326 mg m-2 h-1; methane dissolved in surface water (11-61 mug l-1) was taken up by the plant and eliminated through the plant's ventilating system largely through the leaves. Although methane emission increased with increase in the content of dissolved methane, wind velocity, pla nt surface area and light intensity, there was no proportionality betw een methane emission and these factors. Methane emission was reduced a bout 70% in darkness. The optimum pH and soil temperature for methane production by methanogens was 33-degrees-C. Leaf tissues were most eff iciently utilized by soil microorganisms for methane production. It ha s been estimated that in India alone 1.2 Tg of methane are emitted per year.