A primary study of the methane flux on the water-air interface of eight lakes in winter, China

Abstract

采用静态箱-气相色谱法对中国不同地区的8个湖泊(洞庭湖、鄱阳湖、巢湖、南四湖、洪泽湖、抚仙湖、洱海、滇池)冬季水体水-气界面甲烷(CH₄)通量进行了24h连续观测, 对中国湖泊冬季CH₄的总释放量进行了估算, 结果表明:鄱阳湖、巢湖、南四湖、洪泽湖和滇池24h内各时段均为大气CH₄的源, 其通量分别为0.818、0.021、0.034、0.019、0.163 mg/(m²·h);洞庭湖、抚仙湖和洱海部分时段为大气CH₄的汇, 但从24h平均通量来看, 仍为大气CH₄的源, 通量分别为0.199、0.012、0.044mg/(m²·h)冬季湖泊水体CH₄通量空间差异较小, 其大小主要受风速的影响, 与水温、箱内温度和DOC没有明显的相关关系.中国湖泊冬季(90d)CH₄总释放量大约为3.22±2.75×10⁷kg, 约为1990年中国稻田CH₄总释放量的2.8‰.;In order to examine the winter daily change of the methane flux of the eight lakes in China, the methane flux on the water-air interface was observed continuously for 24-hour based on a closed-chamber and gas chromatography-based system from 14, Dec.in 2004 to 14, Jan.in 2005, including Lake Dongting, Lake Poyang, Lake Chaohu, Lake Nansi, Lake Hongze, Lake Fuxian, Lake Erhai and Lake Dianchi.Furthermore, the total methane emission from lakes to atmosphere was calculated during the winter period according to the average methane flux of the eight lakes.The result suggested that Lake Poyang, Lake Chaohu, Lake Nansi, Lake Hongze and Lake Dianchi were the source of the atmospheric methane during the time, with the average flux of 0.818, 0.021, 0.034, 0.019 and 0.163 mg/(m²·h) respectively.As for Lake Dongting, Lake Fuxian, Lake Erhai they were yet the methane source to the atmosphere by the average flux of 24 h, which was 0.199, 0.012 and 0.044 mg/( m²·h) respectively, though they were the sink at some time.There was little difference among the methane flux of these eight lakes, and it was mainly affected by wind speed.In addition, no obvious statistic relationships were found between the flux and water temperature, and between the temperature in the sample bucket and the concentration of DOC.The average flux of eight lakes was 0.164 ±0.140 mg/( m²·h).Multiplied by 9.1 ×10⁴ km² which is the surface area of all lakes in China and 90-day for winter period, a total of 3.22 ±2.75 ×10⁷ kg of methane was estimated to emit to the atmosphere from the winter lakes.Compared with other emission sources, the methane emission from lakes was lower, only 2.8‰ of the total methane emission from rice field in 1990.