模拟研究中国自然土壤源NO排放及其与气候变化的关系

Nitrogen oxides(NOx) play a critical role in regulating production and depletion of troposphere Ozone. Soil source NOx are mainly produced by microbial processes of nitrification and denitrification as Nitric oxide(NO). In the atmosphere, NO reacts rapidly with other atmospheric compounds, establishing an equilibrium between NO and nitric dioxide (NO2). Satellite observations can detect tropospheric vertical NO2 column densities, when combined with a global chemistry model and an inversion approach, the inventory of fuel combustion and soil sources can be derived. However it is still hard to indentify the soils sources under natural vegetation(SNOx) from agricultural sources. Currently, estimating the SNOx still relies on the emissions factor methods. Antropogenic fuel combustion and agricultural sources are the main sources for atmospheric NOx at human concentrated area, but especially in remote continental regions of the mid- and low-latitudes, SNOx is the dominant source of NOx. To understand the contributions of SNOx to the regional total sources of NOx in China:(1) we aim to develop a global SNOx database from the peer-reviewed literature. And this database will be used to calibrate the process-based dynamic nitrogen cycle model (DyN-LPJ); (2) the nine regions that were poorly influenced by human activities have been selected to compare the monthly and annual dynamics of the model simulation with satellite ovserved tropospheric vertical NO2 column densities. The key dominant climate factors for monthly and annual SNOx will be analyzed; (3) the SNOx from natural terrestrial ecosystems (forest, grassland, scrublands and deserts) in China and their their responses to climate change will be estimated. This research would be helpful to correctly quantify the contribution of SNOx to total atmospheric NOx sources in China regions.

氮氧化物（NOx）是影响对流层臭氧产生与消耗的重要活性成分。土壤源NOx主要通过微生物硝化反硝化过程以一氧化氮（NO）的形式排放到大气，后反应生成二氧化氮（NO2）。卫星可探测大气中NO2浓度，结合大气化学模式可反演工业源和总土壤源。但在区分自然土壤源（SNOx）与农业土壤源方面，主要依赖于排放因子法，仍存在很大的不确定性。特别是在远离人类活动的非农业生态系统，SNOx仍然是大气NOx 的主要源。如何有效的估算SNOx在总排放源中的贡献？本项目拟:1)建立全球自然生态系统SNOx数据库，校正与改进动态氮循环机理模式；2)在全球范围内选定9个受人类活动影响弱的地区，将机理模式模拟和卫星遥感监测NO2柱浓度相结合，分析SNOx的季节和年际动态及其与气候因子的作用机制；3)应用模式计算我国SNOx的空间分布格局及其对气候变化的响应。为客观评价SNOx对中国地区大气NOx总源的贡献提供科学依据。

氮氧化物（NOx）是影响对流层臭氧产生与消耗的重要成分。土壤源NOx主要通过微生物硝化反硝化过程以一氧化氮（NO）的形式排放到大气，后反应生成二氧化氮（NO2）。卫星可探测大气中NO2浓度，结合大气化学模式可反演工业源和总土壤源。但在区分自然土壤源（SNOx）与农业土壤源方面，主要依赖于排放因子法，仍存在很大的不确定性。本项目建立了全球自然生态系统SNOx排放数据库，应用该数据库检验并校正了陆地生态系统氮素循环、氮温室气体排放机理模式，DyN-LPJ。在全球范围内选定9个受人类活动影响弱的地区，将机理模式模拟和卫星遥感监测NO2柱浓度相结合，分析了SNOx排放的季节和年际动态及其和气候因子的作用机制；发现温度变化是控制森林和草地SNOx排放季节动态的关键要素。进而应用模式计算了我国SNOx的空间分布格局及其对气候变化的响应。中国2000年代的SNOx排放速率为：0.58±0.24 TgN/yr，其中森林为0.10±0.04 TgN/yr、灌丛0.15±0.05 TgN/yr、草地0.17±0.10 TgN/yr，农业本底排放源为0.14±0.04 TgN/yr。模式敏感性分析表明年际尺度上气温和大气CO2浓度升高促进SNOx释放。本项目对于客观评价在未来全球气候变化条件下SNOx对中国地区大气NOx总源的贡献具有重要意义。

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