CH 4 emission and oxidation in Chinese rice paddies

摘要: In the paper, characteristics of CH4 emission from rice paddies, its temporary and spatial variations as well factors regulating oxidation are reviewed with an emphasis on paddies in China. The observed four types diel variation two type seasonal can be explained by methane production soil transport efficiencies three routs. inter-annual fields is significant, but process causing this change very complicated unclear based available data at present. large special variation, more than 10 times difference, total season emissions various China, largely attributed to difference although both physics chemistry important. Rice growing activities regulate patterns emissions. Drainage flooded water may significantly reduce emission. Organic fertilizer enhance emission, while some chemical fertilizers Local climate conditions, average temperature annual rainfall, responsible for part year differences Estimates Chinese fields, field measurement model calculation, 9.7–12.7 Tg/year 8.17–10.52 respectively, 1994. Oxidation reduces produced atmosphere. most likely sites water–soil interface rhizosphere. When flood dries up irrigated important partially explain lower rates during last period before harvest experiments. magnitude rhizosphere not known. Good correlation between reduction O2 mixing ratio has been found types. Methane rate mainly controlled gas resistance soil. increases increase range 5–36 °C.