青藏高原大气气溶胶氮的组成、来源与环境意义

The ecosystem and environment in Tibetan Plateau (TP) is very fragile and sensitive. Now it is well recognized that TP is impacted by the air pollution from South Asia through transboundary transport. Nevertheless, the knowledge on the nitrogenous aerosols over TP is extremely scarce，although they are the major components of atmospheric pollutants and the critical element to affect the ecosystem. This project plans to choose representative sites in various ecological area in TP and conduct continuous aerosol sampling. Subsequently, the nitrogenous components (e.g. inorganic nitrogen/organic nitrogen, water soluble nitrogen/water insoluble nitrogen) in the aerosol samples will be accurately determined, with the special emphasis on the amino acids and urea. We aim to reveal the concentration level and spatial-temporal variation of nitrogenous aerosols in TP, and to identify their sources using the molecular markers and stable isotope ratios. Atmospheric modelling will be carried out to quantify the relative contribution of transboundary transport. Finally, the deposition flux and ecological impact of nitrogenous components in aerosols will be quantitatively evaluated. The research will present important information regarding the impact of anthropogenic activities on TP, provide theoretical basis for the construction of National Ecological Security Shelter Zone, and scientific support for the environmental diplomacy.

青藏高原生态环境敏感而又脆弱，受到南亚跨境污染影响已是不争的事实。氮是大气污染物的重要组成，也是影响生态的关键元素，但青藏高原气溶胶氮的认识非常匮乏。本研究将在青藏高原典型生态区开展连续气溶胶样品采集与观测，对大气气溶胶氮组分（无机氮/有机氮、水溶性氮/不溶性氮）进行准确测定，特别关注有机氮中的氨基酸、尿素等组分；揭示青藏高原不同生态区大气气溶胶氮的浓度水平、空间变化及季节差异；通过分子标志物和稳定同位素技术对其来源进行解析；利用大气模式模拟外源输入高原的传输路径和规模；准确估算气溶胶氮干沉降对青藏高原生态系统的输入通量与影响。研究成果将为评估人为活动对青藏高原影响提供新认识，为优化生态安全屏障建设提供理论依据，为环境外交提供科学支撑。

氮是大气气溶胶的重要组成部分，在全球生物地球化学循环中以及气候系统中发挥着重要的作用。青藏高原生态环境敏感而又脆弱，然而对于大气气溶胶的氮组分认识非常匮乏。围绕这一科学问题，在本项目的支持下取得了以下主要进展：（1）建立和完善了青藏高原大气气溶胶监测网络，连续开展了气溶胶样品的采集与观测；（2）通过全面化学分析，明确了不同形态氮（水溶性氮/不溶性氮、无机氮/有机氮）的组成特征，有针对性的改进和开发了相关测试方法，特别关注了有机氮中的氨基酸、尿素等组分；（3）基于化学分析数据和野外观测（黑碳仪和AERONET太阳光度计），结合卫星遥感产品，准确揭示了南亚大气氮组分跨境输入高原的传输路径；（4）估算了青藏高原大气气溶胶氮的干沉降通量，结合湿沉降数据初步评估了大气氮沉降的生态风险，发现在跨境污染物影响下，氮沉降已经超过高山生态系统的安全阈值。上述认识提升了对高寒特殊环境下氮的生物地球化学循环的理解，为揭示青藏高原地表多圈层（人类圈、大气圈和生物圈）相互作用机制提供了理论依据，为青藏高原生态文明建设提供了科学支撑。