Li Rui, Lei Li-Guo, Jiang Chang-Sheng, Chai Xue-Si, Huang Zhe, Fan Zhi-Wei, Hao Qing-Ju
Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, Chongqing 400716, China.
Huan Jing Ke Xue. 2016 Jul 8;37(7):2721-2730. doi: 10.13227/j.hjkx.2016.07.040.
Three heights (180 m, 175 m and 155 m) located in a typical drawdown area in Wangjiagou of the Three Gorges Reservoir were selected for studying the NO emissions from subtropical reservoirs. The experimental period lasted two years from August 2010 to August 2012. The methods of static opaque chambers during the drainage period and floating chambers during flooding period were adopted in this study. The heights of 175 m and 155 m were both located in the drawdown area, whereas the 180 m height was located in the land as a control to 175 m and 155 m. NO fluxes showed clear seasonal trends at each height and remarkable differences were observed between the two years at the 180 m height. NO fluxes were lowest in spring at the 180 m height. NO fluxes showed a single-peak pattern with climax in summer in the first year, whereas a double-peak pattern with climax in summer and after dry-wet alternating in the next year after the highest water level of 175 m was succeeded in the Three Gorges Reservoir. NO fluxes presented a single-peak shape with summer climax at the 155 m height. Additionally, NO fluxes were higher during the drainage period than in the flooding period at both the 175 m and 155 m heights. The order of the annual NO cumulative emissions at the three heights was 175 m (853.92 mg·m) > 180 m (336.69 mg·m) > 155 m (324.69 mg·m), and there was a notable difference between 175 m and 155 m, indicating that short-term flooding could increase NO emissions but long-term flooding could restrain NO emissions. Correlation analysis showed that there were no obvious relativities between NO fluxes and environmental factors in the land and during the drainage period. However, NO fluxes were significantly negatively correlated with water temperature and wind speed during the flooding period. Principal component analysis found that soil nutrient conditions and physicochemical properties were the most important factors for NO emissions in the land, the nitrogen distribution in water was a main determinant for NO emissions during the flooding period, and soil physicochemical properties and microbial activity importantly affected NO emissions during the drainage period in the drawdown area.
选取三峡水库王家沟典型消落区内的三个高度（180米、175米和155米），用于研究亚热带水库的一氧化氮排放情况。实验期从2010年8月持续至2012年8月，为期两年。本研究采用了排水期的静态不透明箱法和洪水期的浮动箱法。175米和155米的高度均位于消落区内，而180米高度位于陆地上，作为175米和155米高度的对照。各高度处的一氧化氮通量呈现出明显的季节趋势，且180米高度处两年间存在显著差异。180米高度处春季的一氧化氮通量最低。第一年，180米高度处的一氧化氮通量呈单峰模式，夏季达到峰值；而在三峡水库成功蓄水至175米最高水位后的次年，一氧化氮通量呈双峰模式，夏季达到峰值，且在干湿交替后出现峰值。155米高度处的一氧化氮通量呈单峰形状，夏季达到峰值。此外，175米和155米高度处排水期的一氧化氮通量均高于洪水期。三个高度处一氧化氮年累积排放量的顺序为175米（853.92毫克·米）>180米（336.69毫克·米）>155米（324.69毫克·米），175米和155米之间存在显著差异，表明短期洪水会增加一氧化氮排放，但长期洪水会抑制一氧化氮排放。相关性分析表明，陆地区域和排水期内一氧化氮通量与环境因子之间无明显相关性。然而，洪水期一氧化氮通量与水温和风速度显著负相关。主成分分析发现，土壤养分状况和理化性质是陆地区域一氧化氮排放的最重要因素，水体中的氮分布是洪水期一氧化氮排放的主要决定因素，土壤理化性质和微生物活性对消落区排水期的一氧化氮排放有重要影响。
