我国东部沿海大气边界层顶新粒子生成的观测和模拟研究

Atmospheric aerosol particles impact both human health and climate. On a number basis, new particle formation (NPF, including nucleation and the subsequent growth process) is the dominant source of particles on a global scale. A recent study found that under complex air pollution in China, NPF is an important cause of secondary aerosol pollution. Currently, the exact mechanism for NPF remains unknown. Both observations and simulations have shown that NPF mechanisms differ in time and space. However, existing schemes were mostly based upon relatively clean atmospheric conditions abroad. By taking Mount Lao as the regional background site, this project aims to systematically study the NPF features at the top of the boundary layer of the east coast of China. The observation results will enrich the NPF data set of China and help explore the gas-to-particle conversion scheme. Meanwhile, the 3D air quality model (NPF-explicit WRF-Chem) will be used to simulate the observed NPF events to better understand the nucleation and consequent growth mechanisms, evaluate the regional impacts of NPF on CCN, and provide scientific support for improving national air quality.

大气气溶胶对人体健康和气候均有影响。从数浓度的角度来看，在全球范围内，新粒子生成（NPF，包括颗粒物成核和后续的增长过程）是气溶胶的主要来源。最近的一项研究发现在我国大气复合污染条件下，NPF是二次颗粒物污染的重要诱因。目前，对NPF机理尚无统一的认识。以往研究的观测和模拟结果均表明成核机制因时间、地点的不同而呈现出差异。然而，现有机制的提出多基于国外较为干净的大气环境。因此，本项目拟选取崂山作为我国东部沿海地区的高山背景站点，结合外场观测和三维区域空气质量模式（NPF-explicit WRF-Chem）模拟，系统研究我国东部沿海大气边界层顶的NPF特征。观测结果将丰富我国的NPF数据库，有助于探讨大气中气态前体物向颗粒物转化的机理；同时，结合三维空气质量模型来模拟观测到的NPF事件，深入理解颗粒物的成核和增长机制、估测NPF对CCN的区域性影响，进而为全国空气质量改善提供科学技术支撑。

新粒子生成（NPF）是大气颗粒物的重要来源，目前对新粒子的生成和增长机理尚无统一的认识。依托本项目，我们在青岛沿海开展了外场观测实验，获得了不同季节（春季、夏季和冬季）的气象、气体和颗粒物浓度数据，结合三维空气质量模式NPF-explicit WRF-Chem分析研究了颗粒物数浓度变化特征、新粒子生成事件的发生频率、新粒子的生成和增长速率及影响新粒子生成和增长速率的主要气象条件和关键性气态前体物。研究结果表明，低相对湿度有利于NPF事件的发生。在春季，高温有利于NPF事件的发生；而在夏季和冬季，温度对NPF无明显影响。受海洋气团影响，NPF在夏季的发生频率最低。SO2是NPF的重要前体物，并且贡献了颗粒物的增长。在冬季，颗粒物的增长主要受硫酸盐和硝酸盐影响；而在春夏季，有机物对新粒子的增长也起到了重要的作用。该项目研究成果可为更好地理解沿海地区大气新粒子的生成和增长提供科学依据。