中国南方地区氮沉降对稻田甲烷排放影响的遥感监测与模拟

Nitrogen deposition is one of the global environmental problems, inducing serious impact on ecosystems. However, the influence of nitrogen deposition on CH4 emissions from paddy field at regional scale is rarely studied. Taking the south area of China as the study area, this proposal firstly inverses the temporal and spatial variations of nitrogen deposition by fusing the profiles of NH4-N and NO3-N from the simulation of atmospheric chemistry model, NO2 column concentrations from satellite observation, and the wet and dry nitrogen depositions from ground observations. Second, controlled experiments are conducted to monitor the characteristics of CH4 emissions and the physical characteristics of soil from paddy field under the influence of different nitrogen compositions and amounts, and then the influencing model of CH4 by nitrogen deposition are constructed. At the same time, several fields are selected based on the spatial and temporal gradients of nitrogen deposition in the study area, and relevant soil parameters are measured to revise the influencing model based on the controlled experiments. Third, the spatial distribution, planting, rotation of paddy field in south area of China are obtained from MODIS. Based on the spatial distribution of nitrogen and paddy field, a process-model of nitrogen cycling is used to reveal the mechanism of the influence of nitrogen deposition on CH4 emissions at regional scale. This study has important theoretical and practical significance to the development of quantitative, fine direction in remote sensing applications, and to improve the estimation accuracy of the global CH4 emissions. Moreover, it also provides the scientific basis for the relevant departments to make adaptation policies.

氮沉降已经成为全球面临的重大环境问题之一，探讨区域尺度氮沉降对稻田排放甲烷（CH4）的影响对于全球变化研究和计算全球CH4收支平衡具有重要意义。本研究选择我国南方水稻种植区，首先利用卫星遥感监测的大气NO2柱浓度，耦合大气化学传输模型模拟的硝态氮和铵态氮廓线，并结合地基监测，根据干湿沉降模型模拟氮沉降的时空分布格局；布置受控实验，监测不同氮沉降组分和沉降量对稻田排放CH4的影响，建立定量影响模型，同时布置野外监测点，修正建立的影响模型；利用MODIS影像及其产品，提取水稻种植面积、轮作、水淹等信息；并根据氮沉降及稻田、土壤等的时空分布格局，利用生物地球化学模型模拟区域尺度氮沉降对稻田排放CH4的影响，从而揭示中国南方地区氮沉降影响稻田CH4排放的时空动态和驱动过程。该研究对遥感技术应用向定量化方向发展、全球变化研究具有重要意义，为国家相关部门制定适应性政策提供科学依据。

氮沉降已经成为全球面临的重大环境问题之一，探讨区域尺度氮沉降对稻田排放甲烷（CH4）的影响对于全球变化研究和计算全球CH4收支平衡具有重要意义。本研究基于卫星OMI监测的NH3和NO2大气柱浓度、大气化学传输模型MOZART-4模拟的NH3和NO2的廓线数据、以及区域尺度地面的站点监测数据，基于沉降过程构建了氮气体、颗粒物和湿沉降模型，并在此基础上估算了我国无机氮沉降的时空动态分布；并基于受控实验和DNDC模型，监测和模拟了氮沉降对我国稻田产量和CH4排放的影响。结果显示，我国无机N总沉降的值域范围为2.81~200.26 kg N ha-1 yr-1，平均值为26.64 kg N ha-1 yr-1。干沉降通量高于湿沉降通量，占总沉降量的61.8%；硝态氮沉降高于铵态氮沉降，占总沉降通量的55.9%。硝态氮沉降从1997年开始上升，在2012年达到最高值，然后呈现下降趋势；铵态氮则在1997-2017年间呈现一直上升的趋势。DNDC模拟结果显示，氮沉降对我国水稻的产量影响不显著的模拟单元（以县为单元）占84%，15%的模拟单元提高了稻谷产量；但是氮沉降在我国目前氮肥施用情况表现出明显的抑制作用，全国单季稻CH4总排放减少1.39×107 kg CH4-C，占全国平均总CH4排放量的1.3%；双季稻CH4总排放减少8.28×106 kg CH4-C，占全国平均总CH4排放量的0.6%。该研究对遥感技术应用向定量化、精细化方向发展，以及全球变化研究具有重要意义，也为国家相关部门制定适应性政策提供科学依据。