| 摘要: |
| 本研究基于大气化学传输模型模拟结果，分析了2005—2015年华北地区大气氮沉降的时空分布特征，通过对2005年和2015年的结果进行模型敏感性实验，定量分析了全国和华北本地的人为源排放以及气象场对华北地区氮沉降年际变化的贡献。结果表明：（1）2005—2015年华北地区氮沉降年均量为28.7 kg·hm−2·a−1（以N计，余同），其中18.7 kg·hm−2·a−1来自还原态氮（NHx），10.0 kg·hm−2·a−1来自氧化态氮（NOy）。湿沉降占比为56%（16.1 kg·hm−2·a−1），略高于干沉降（12.6 kg·hm−2·a−1）。氮沉降的高值主要集中在华北的东南地区，低值集中在华北的西北地区，整体呈夏季高冬季低的季节特征。（2）2005—2015年，华北地区氮沉降整体呈先增加后减少的趋势，波动范围在27.4—30.4 kg·hm−2·a−1。相较2005年，2015年氧化氮沉降增加了2.2 kg·hm−2·a−1，而还原氮沉降减少了1.9 kg·hm−2·a−1。其中氮氧化物（NOx）和氨气NH3）人为源排放的变化分别导致了1.0 kg·hm−2·a−1氧化氮沉降的增加和2.5 kg·hm−2·a−1还原氮沉降的减少，分别占全国人为源排放贡献的89%和53%，这说明区域传输对于2005—2015年还原氮沉降变化的影响较大。（3）华北地区干沉降的年际变化主要取决于前体物排放的变化，而湿沉降不仅受前体排放的影响，也受到降水等气象场的驱动。 |
| 关键词: 氮沉降 时空分布特征 人为源排放 气象场 |
| DOI：10.7515/JEE232001 |
| CSTR：32259.14.JEE232001 |
| 分类号: |
| 基金项目:山东省自然科学基金项目（ZR202102280270，2022HWYQ-066） |
| 英文基金项目:Shandong Provincial Natural Science Foundation (ZR202102280270, 2022HWYQ-066) |
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| Model study on the spatial and temporal variations of nitrogen deposition over North China |
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LIN Yizhen, LI Ling, ZHAO Yuanhong, CHEN Youfan
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1. College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China
2. Key Laboratory of Physical Oceanography, Ocean University of China, Qingdao 266100, China
3. Sichuan Academy of Environmental Policy and Planning, Chengdu 610041, China
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| Abstract: |
| Background, aim, and scope The observations indicate that North China is experiencing high levels of emissions and deposition of reactive nitrogen. A thorough analysis of the spatial and temporal variations of nitrogen deposition in North China is crucial for better understanding its potential ecological and climate impacts. Materials and methods In this study, we estimated the spatial and temporal variations of nitrogen deposition over North China using the atmospheric chemistry transport model GEOS-Chem. We also quantified the contributions of national (terrestrial regions in China) and regional (North China) anthropogenic emissions and meteorological conditions to the changes in nitrogen deposition between 2005 and 2015 based on model sensitivity experiments. Results The model simulations revealed that the averaged annual total nitrogen over North China during 2005—2015 is 28.7 kg·hm−2·a−1, with 18.7 kg·hm−2·a−1 is from reduced nitrogen (NHx) and 10.0 kg·hm−2·a−1 is from oxidized nitrogen (NOy). Wet deposition contributes 56% (16.1 kg·hm−2·a−1), slightly higher than dry deposition (12.6 kg·hm−2·a−1). High values of nitrogen deposition are primarily concentrated in the southeast of North China, while low values are concentrated in the northwest. Compared to 2005, reduced nitrogen deposition increased by 2.2 kg·hm−2·a−1, while oxidized nitrogen decreased by 1.9 kg·hm−2·a−1 in 2015. Anthropogenic emissions over North China led to a 2.5 kg·hm−2·a−1 decrease in reduced nitrogen and a 1.0 kg·hm−2·a−1 increase in oxidized nitrogen, contributing to 89% and 53%, respectively, of the changes driven by total anthropogenic emissions in China. Discussion In this study, we discovered that the interannual variation of oxidized nitrogen deposition in North China is consistent with its precursor NOx emissions. However, the interannual variation of reduced nitrogen deposition is quite distinct from that of NH3 emissions. Interannual variations in precipitation can significantly influence the wet deposition of reduced nitrogen, while changes in SO2 and NOx emissions affect the dry deposition of reduced nitrogen through nonlinear chemical processes. These complex factors determining reduced nitrogen deposition suggest that controlling nitrogen deposition over North China should not only consider the emissions of reactive nitrogen but also take into account meteorological conditions and nonlinear atmospheric chemistry. Conclusions The interannual variations in dry deposition over North China primarily depend on the variation of precursor emissions, while wet deposition is determined by both precursor emissions and meteorological conditions. From 2005 to 2015, regional transport played a more significant role in determining the changes in reduced nitrogen deposition compared to oxidized nitrogen deposition. Recommendations and perspectives This study examined the spatial and temporal characteristics of nitrogen deposition in North China and quantitatively analyzed the contributions of anthropogenic emissions and meteorological factors. The findings offer valuable insights for the government to develop science-based emission control policies to mitigate nitrogen pollution in North China. |
| Key words: nitrogen deposition spatial and temporal distribution anthropogenic emissions meteorological field |
