黑碳气溶胶观测中的光学饱和效应研究

Black carbon (BC) is essentially a primary pollutant, emitted directly during the incomplete combustion of fossil and biomass carbonaceous fuels. One of the important atmospheric phennomena resulting from the presence of BC is the absorption of light in visible wavelengths. This absorption and subsequent atmospheric heating effect represents a considerable amount of heating of the atmosphere and a potantial factor causing global warming. Also BC is a major component of PM2.5 has been linked to significantly increased risk of death from lung cancer and other severe respiratory ailments. For its climate and environment effect, BC has been highly concerned in recent years. The Aethalometer is widely-used instrument for measuring BC mass concentration at high time resolution. Optical saturation effect, the decrease in mass absorption efficiency with increased loading of absorbing aerosol onto the filter, has been observed as a step-increase in Aethalometer response across tape advances. The effect is not only due to the nature and mass of the absorbing aerosol but also the presence of scattering aerosol.The study of the optical saturation effect will be helpful to further understand the optical properties of the aerosol. This proposal is focus on the impaction factors of the optical saturation effect and its compensation method. The study will base on the long-term network BC observation data at 31 stations. Also the observation on aerosol multiple parameters will be conducted at a city and a regional stations. The main impaction factors of the optical saturation and its indication significance to some properties of aerosol will be studied by the correlation analysis with the simultaneously observed parameters. We try to get a suitable compensation method for the optical saturation by evaluating and improving the exist methods. And the compensation coefficient will be analysed to find its temporal and spatial variation and the indicated the variation of aerosol properties, such as the absorbing and scattering properties. The wavelength-dependent property of the optical saturation effect will be also studied to investigate the impaction of the aerosol properties on it. Base on the previous study on the absorbing contribution of mineral aerosol, the multi-wavelength method will be implemented to futher understand the issue. Also the source properties will be identified. The research result will benefit to get more accurate BC observation data set and to recognize and understand the properties of the absorbing aerosol in China.

具有强吸收性的黑碳气溶胶具有增温效应，并对人体健康产生危害，在气候变化和大气环境领域受到高度关注。以光学方法在线测量黑碳气溶胶浓度时存在光学饱和效应，即随着吸收性气溶胶在滤膜上不断增加其光学吸收效率降低，这对于气溶胶一些光学特征的研究有重要的指示意义。本项目拟依托黑碳气溶胶多年站网观测资料分析，结合城市和本底站点的气溶胶多要素加强观测实验研究，获得适合我国站网观测黑碳气溶胶的光学饱和效应补偿方法，认识光学饱和效应的主要影响因素及其对气溶胶某些特性的指示意义，从光学补偿系数的时空分布特征中获得气溶胶吸收、散射特性的变化特征；研究不同波长光学饱和效应与气溶胶组分的关系，通过多波长光学饱和特性分析进一步评估矿物气溶胶对吸收性的贡献，以及吸收性气溶胶的主要来源。为进一步理解我国吸收性气溶胶特性提供一些科学依据。

具有强吸收性的黑碳气溶胶具有增温效应，并对人体健康产生危害，在气候变化和大气环境领域受到高度关注。以光学方法在线测量黑碳气溶胶浓度时存在光学饱和效应，即随着吸收性气溶胶在滤膜上不断增加其光学吸收效率降低，这对于气溶胶一些光学特征的研究有重要的指示意义。通过项目的研究揭示了我国不同粒径气溶胶浓度和黑碳气溶胶的时空分布和变化特征，指出了华北地区和东北是我国黑碳气溶胶浓度较高的地区，黑碳气溶胶呈现秋冬季浓度高、春夏季浓度低的特征。在人为排放集中的城市站点黑碳气溶胶通常占PM2.5浓度10%以上，是PM2.5中的一个重要组成部分。气象因素对短期内浓度变化的影响明显，风速和浓度反相关，相对湿度和浓度正相关（降水例外）。气象因素和排放因素都对颗粒物和黑碳浓度长期（年度）变化有重要影响。研发了判断数据离群值的算法和软件OutlierFlag，并在站网数据质量控制业务中得到推广应用。评估获得了适合我国黑碳气溶胶观测站网光学饱和效应补偿方法，并开发了相关计算程序。认识到光学饱和效应主要受散射性气溶胶含量的影响。着重分析了泰山、临安、龙凤山本底站的黑碳气溶胶变化特征，并获得了其潜在源区的分布。项目共发表学术论文12篇，其中SCI论文10篇。获得了两项软件著作权，相关软件在业务单位进行了推广应用。