玉渡山水库生长季温室气体排放特征及其影响因素

为了探讨温带水库温室气体排放规律,采用静态箱-色谱分析法,研究了温带地区库龄10年内的北京玉渡山水库生长季3种温室气体CO2、CH4及N2O排放特征,及其影响因子。结果表明:样地类型、测定月份与样地类型交互作用对3种温室气体通量影响极显著,5月消落带CO2通量(664.31mg·m-2·h-1)达到最大,显著高于入库口和浅水区;8月消落带CH4通量(0.87mg·m-2·h-1)及N2O通量(3.05mg·m-2·h-1)最大;8月,切除消落带样地地上植物后,3种温室气体通量均有所降低。CO2通量与地下5cm地温、氧化还原电位和水体总氮显著正相关,与地上生物量和水体pH显著负相关;CH4通量与地表温度、地上生物量、水体pH呈显著相关,与水体总氮和水体铵态氮显著负相关;N2O通量与水体总氮含量显著相关,与水体pH显著负相关。采取平均估值法初步推测,在生长季,水库消落带、入库口及浅水区CO2排放量依次为15960、2160、-70kg·hm-2;CH4排放量依次20.04、-7.05、14.8kg·hm-2;N2O排放量依次83.42、3.79、-1.54kg·hm-2;表明消落带3种温室气体的排放量均较高,为玉渡山水库3种温室气体排放的重点区域。

Characteristics and environmental determinants of greenhouse gas emissions from Yudushan Reservoir during growth season

Wetland can produce and store large amount of organic matters, playing a significant role in the global carbon and nitrogen cycles, and in particular, greenhouse gases (CO2, CH4 and N2O) fluxes. Most of the previous studies are focused on the greenhouse gas emissions from peat lands, lakes, and crop fields, but few are targeted on reservoirs, especially those located in temperate zone. In this study, three greenhouse gases (CO2, CH4, and N2O) fluxes and their environmental determinants at different locations (eulittoral zone, reservoir entrance, and shallow water zone) in Yudushan Reservoir of Beijing were measured by using static opaque chamber-GC technique during the growth season (May, August, and October) in 2009 and 2010. A great variation in the greenhouse gases (CO2, CH4, and N2O) fluxes was observed among the sampling locations, and this variation was affected by the combined effect of sampling location and sampling month. In May, the CO2 flux in the eulittoral zone reached the highest (664.31 mg·m-2·h-1), which was significantly higher than that at the reservoir entrance and in shallow water zone. In August, the CH4 and N2O fluxes in the eulittoral zone was the highest (0.87 mg·m-2·h-1 for CH4 and 3.05 mg·m-2·h-1 for N2O), but the fluxes of CO2, CH4 and N2O in the zone had somewhat decrease after the vegetations above the ground were removed. Pearson correlation analysis indicated that CO2 flux was significantly positively correlated with soil temperature and redox potential at 5 cm depth and water total nitrogen content but significantly negatively correlated with above-ground biomass and water pH, CH4 flux was significantly correlated with surface soil temperature, above-ground biomass, and water pH but negatively correlated with water total nitrogen and NH4+ contents, while N2O flux was significantly correlated with water total nitrogen content but negatively correlated with water pH. By the mean value estimation method, it was deduced that the total greenhouse gas emissions in the eulittoral zone, reservoir entrance, and shallow water zone during growth season were 15960, 2160 and -70 kg·hm-2 for CO2, 20.04, -7.05 and 14.8 kg·hm-2 for CH4, and 83.42, 3.79 and -1.54 kg·hm-2 for N2O, respectively, suggesting that the eulittoral zone was the most important zone for the greenhouse gas emissions in the Yudushan Reservoir.