澜沧江梯级水库CO_(2)和CH_(4)排放通量研究

Study on CO_(2) and CH_(4) emission fluxes from Lancang River cascade reservoirs

温室效应已成为重要的全球气候问题,而内陆水体是温室气体(CO_(2)和CH_(4))的重要排放源,更有研究发现筑坝蓄水可能引起河流水体CO_(2)和CH_(4)排放的增多。为积极响应国家“双碳”目标,使用水库温室气体净排放通量评估模型G-res Tool,利用流域基本信息及水库特征数据,对澜沧江干流已建成的10座梯级水库温室气体(CO_(2)和CH_(4))进行模拟计算,10座水库蓄水后温室气体(CO_(2)和CH_(4))年排放通量平均值为162.81 g CO_(2)e/(m^(2)·a),远低于全球水库平均水平,均表现为温室气体的“源”,从上游至下游整体呈增加趋势,且排放以CO_(2)为主,全年CO_(2)排放通量为CH_(4)的36倍。考虑了水库蓄水前的温室气体排放及其他非相关人类活动的影响后,得到澜沧江水库温室气体(CO_(2)和CH_(4))年净排放通量平均值为225.70 g CO_(2)e/(m^(2)·a),表明筑坝增加了库区水体温室气体排放,但和火力发电相比,仍属于相对清洁能源。

The greenhouse effect has become an important global climate issue,and inland waters are an important source of emissions of the greenhouse gases(GHG)CO_(2) and CH_(4).It has been found that hydropower energy,once considered clean,may cause an increase in CO_(2) and CH_(4) emissions from river waters as a result of damming and impounding water.In order to actively respond to the national“Dual-Carbon”goal and clarify the impact of damming and impounding on GHG emissions from water bodies,the G-res Tool,a model for evaluating the net flux of GHG emissions from reservoirs,was used to simulate the CO_(2) and CH_(4) emission fluxes before and after impoundment of 10 completed terrace reservoirs on the main stream of the Lancang River.The average annual GHG(CO_(2) and CH_(4))emission flux of the 10 reservoirs after impoundment is 162.81 g CO_(2)e/(m^(2)∙a),which is much lower than the global average level of reservoirs,but all of them behave as“sources”of GHGs,with an overall upward trend from upstream to downstream.Emissions are dominated by CO_(2),with an annual CO_(2) emission fluxes 36 times that of CH_(4),which is dominated by diffuse and off-gas emissions.After considering the GHG emissions prior to reservoir impoundment and the impacts of unrelated anthropogenic sources,the average annual net flux of GHG(CO_(2) and CH_(4))emissions from the reservoir is 225.70 g CO_(2)e/(m^(2)∙a),suggesting that damming increases the release of GHGs from the reservoir waters.However,hydropower is still a relatively clean energy compared to thermal power generation.