冬季太湖草、藻型湖区N2O的生成与排放特征

摘要

对太湖典型草(包括沉水植物及挺水植物湖区)、藻型湖区水-气界面N2O排放通量、水柱溶存浓度、泥-水界面通量以及3个湖区的水柱及沉积物理化性质进行了原位观测及实验室分析研究,并针对影响N2O生成与排放的主要环境因子进行了室内的微环境模拟试验.研究结果表明:水-气界面N2O释放通量及泥水界面N2O释放通量为藻型湖区＞沉水植物湖区＞挺水植物湖区((123.10±11.43)μg/(mLh),(79.19±4.90) μg/(m2·h),(53.45土4.22)μg/(m2·h)和(29.60±0.20)μmol/(m2·h),(10.89±1.66)μmol/(m2·h),(3.83±0.30)μmol/(m2·h));水体溶存N2O浓度均为藻型湖区＞挺水植物湖区＞沉水植物湖区((0.0247±0.0003)μmol/L,(0.0236±0.0003)μmol/L,(0.0219±0.0001)μmol/L);室内微环境实验结果表明:冬季升高温度能够显著地提高N2O的生成潜力,商盐度对3种生态类型湖区沉积物N2O的生成速率总体表现出抑制作用,藻型湖区及挺水植物湖区沉积物N2O释放潜力在添加Cl-组明显高于控制组,氮盐度过高会抑制沉积物N2O产生,而沉水植物湖区沉积物N2O产生受到抑制;随添加NH-N和NO3-N等营养盐浓度升高,藻型湖区及沉水植物湖区沉积物中N2O生成速率增加,挺水植物湖区N2O生成速率降低,而乙酸盐作为微生物活动的碳源和能源对N2O生成表现出抑制作用.冬季太湖典型草、藻型湖区N2O排放存在显著差异,冬季草/藻型湖区N2O生成主要受冬季低温的限制,另外也受水柱无机氮形态及浓度的影响.%N2O fluxes of water-gas interface and sediment-water interface and the dissolved N2O concentration in water column were studied in grass type zones including submerged plants and emergent plants and algae type zones in Lake Taihu.In situ observation of the physicochemical properties of water and sediments and the laboratory analysis the main factors were also carried out to determine the main factors affecting the production and release of N2O.The results showed that:both N2O fluxes of the water-gas interface and sediment-water interface of algae type zones were highest followed by emergent plants and submerged plants type zones (123.10±11.43)μg/(m2·h),(79.19±4.90)μg/(m2·h),(53.45±4.22)μg/(m2·h) and(29.60±0.20)μmol/(m2·h),(10.89±1.66)μ mol/(m2·h),(3.83±0.30)μmol/(m2·h)).The dissolved N2O concentration in water column of the algae type zones was the highest,but with the emergent plants type zones being the lowest ((0.0247±0.0003)μmol/L,(0.0236±0.0003)μmol/L,(0.0219±0.0001)μmol/L).The experimental results of indoor micro-environment simulation showed that the production of N2O was correlated with the temperaturewhile the high salinity had inhibitory effect in general on the formation of N2O in all three sites.The sediments of algae and emergent plant type zone with added salinity had a higher potential than the control group,and the inhibition persisted since the Cl-was added in submerged plant type zone.With the increase of nutrients concentrations such asNH4+-N and NO3--N,the rate of N2O formation in algae and submerged type zones increased,but emergent type zones decreased.The organic carbon sourceproviding the carbon source and energy for microbial activity inhibited the formation of N2O.There were different characteristics of N2O production and release in algae and grass type zones in Lake Taihu,the formation of N2O in grass and algae type region of Taihu Lake was mainly limited by low temperature of winter,and was also affected by inorganic nitrogen forms and concentration of water column.