中国陆地生态系统大气酸沉降：时空格局、影响因素及其酸化效应

China has been considered as one of the three regions with higher atmospheric acid deposition in the world (maybe the most serious region), and the ecological and environmental effects of increasing atmospheric acid deposition (pH、SO42-、NO3-、NH4+), as a result of rapid increase in the anthropogenic emission of reactive S and N, through burning fossil fuels and fertilizer application in China, have received great interest by the public and scientists in the past decades. Unfortunately, a few of observation have been conducted on these natural ecosystems (forest, grassland, desert), which occupies a large proportion of land area in China, although we have established an observation network in cities or suburbs, which limits the scientific evaluation on the spatio-temporal patterns of atmospheric acid deposition and its eco-environmental effects. .In this project, we will first address the monthly dynamics of atmospheric acid in Chinese typical ecosystems, on the basis of a 10-year monitoring network in 45 ecological stations. Then, we will collect and extract available data of atmospheric acid deposition (pH、SO42-、NO3-、NH4+) from all possible approaches (e.g., books, papers, public database), and establish three periods of (1990s, 2000s, and 2010s) spatial data product on atmospheric acid deposition in China, and explore their changing trends and mainly influencing factors in the past three decades. Furthermore, we will gain the key parameters of acid effect of atmospheric acid deposition in different regions or different ecosystems, using available data from field manipulation experiments of simulation acid deposition and nitrogen deposition in the past decades. Finally, we will evaluate and predict how atmospheric acid deposition influence soil pH (or acid effect) in different natural ecosystems in China with help of all parameters (e.g., atmospheric acid deposition, soil physical and chemical properties, key parameters of acid effect in different ecosystem, and precipitation). All these findings may help us better explore atmospheric acid deposition in China in the past three decades and to better predict the potential effect of atmospheric acid deposition on the structure and functioning of natural ecosystems in China.

由于化石燃料燃烧和机动车尾气排放而释放的含硫和含氮废气大量增加，中国已成为世界上最严重的大气酸沉降区之一，其生态环境效应受到公众和科学家广泛关注。但我国目前对大气酸沉降的监测还主要集中在工业区或城市，对广泛分布的自然生态系统的定位观测还很匮乏，还难以对全国尺度大气酸沉降的时空格局及其生态效应进行准确评估。本研究拟基于联网监测的典型生态系统大气酸沉降数据，结合公开发表数据，构建1980s~2010s中国区域大气酸沉降数据集，探究中国生态系统降水酸沉降的时空格局及其主要影响因素；结合野外模拟酸沉降和氮沉降的实验数据，获得不同区域（或生态系统）土壤酸化效应参数；并将大气酸沉降、土壤理化属性、土壤酸化效应参数等结合，构建基于离子交换平衡理论的土壤酸化预测方法（或阈值），对不同生态系统类型土壤酸化状况进行预测或预警，为揭示大气酸沉降对生态系统结构和功能的影响提供重要的数据支撑和理论基础。

中国已成为世界上最严重的大气酸沉降区之一，其生态环境效应一直受到公众和科学家广泛关注。但目前我国对大气酸沉降的监测还主要集中在工业区或城市，对广泛分布的自然生态系统的定位观测还很匮乏，还难以对全国尺度大气酸沉降的时空格局及其生态效应进行准确评估。本项目依托2013年建立的基于中国生态系统研究网络（CERN）的全国湿沉降观测网络(ChinaWD)，以大气酸沉降（pH、SO42-、NO3 -、NH4+）为重点研究对象，项目执行期间，在全国45个典型陆地生态系统连续4年采集了台站每月雨水样品，开展了全国尺度大气雨水酸沉降的联网观测，获取了连续的月尺度酸沉降观测数据。此外，系统收集了中国境内酸沉降及雨水化学性质已发表文献。基于中国典型生态系统的联网监测数据、多源历史数据，构建了中国陆地生态系统大气酸沉降（不同组分）数据库。在此基础上，分析了大气酸沉降的时空格局及其影响因素，重点解析了中国大气盐基离子沉降的时空变异、来源及酸中和能力，发现了中国陆地生态系统湿硝酸盐沉降对减排的滞后响应；评估了大气酸沉降对中国陆地生态系统土壤酸化的影响，揭示了青藏高原东南部具有更高的土壤酸化风险；同时，综述了氮沉降转型变化及其对生态系统的潜在影响，分析了大气氮沉降及其组分对陆地生态系统碳通量的影响。完成了任务书的既定目标。为了全面认知大气沉降及其生态环境效应，利用基于站点的观测数据，进一步探究了大气雨水Si、Fe、Mo等沉降的时空格局及影响因素。相关研究结果可为揭示大气酸沉降对生态系统结构和功能的影响、全面评估大气沉降的生态环境效应以及环境污染治理提供重要的数据支撑和理论基础。