珠江三角洲大气降水低分子有机酸双碳同位素示踪

Low molecular weight (LMW) organic acids in the atmosphere are important components of volatile organic compounds (VOCs), which have a significant influence on the chemical composition, climate change and ecological environment. The predominant sinks for LMW organic acids is wet deposition. The composition and sources of LMW organic acids are largely variable and complicated, which have always been a concern in the atmospheric research. However, knowledge of their composition and sources is very limited. Identification of its source is the scientific basis for rational air pollution prevention and control policies. Stable carbon isotope (13C) is a good indicator for photochemical processing and aging of organic aerosols. Radiocarbon (14C) measurement is a powerful tool that allows to quantitatively estimate the contribution of modern biomass (contemporary levels of 14C or“alive”) and fossil fuels (14C free or“dead”) to LMW organic acids. To better understand detailed information about source and formation mechanism of LMW organic acids, compound-specific radiocarbon analysis (CSRA) and compound-specific stable-isotope analysis (CSIA) will be applied in this study. In this project, Rainwater samples will be collected in three typical sites in the Pearl River Delta Region (PRD), and LMW organic acids and their indivual molecular 13C &14C content will be analyzed, as well as dissolved organic carbon and biomarkers. The main purpose of this project aims to 1) characterize the molecular composition and seasonal variation of LMW organic acids; in precipitation; 2) and identify the sources and formation mechanism of LMW organic acids based on 13C and 14C results along with other source apportionment methods (correlation analysis and ratios of selected species, biomarkers and principle component analysis etc.), and to quantitatively estimate the sources of LMW organic acids; 3) and characterize the temporal and spatial variation of the sources and the factors influencing the variation of LMW organic acids in the precipitation in the PRD region.

大气中低分子有机酸是挥发性有机物的重要组分，对大气化学组成、气候变化、生态环境具有重要影响。其主要的汇是湿沉降，其化学组成和来源复杂，识别其来源是制定大气污染防治措施的科学依据。稳定碳同位素(13C)是示踪光化学过程和大气老化过程的良好指标，放射性碳同位素（14C）是有效识别并定量化石碳和当代生物碳对低分子有机酸相对贡献的强有力工具。为获得更详细大气降水中低分子有机酸来源及形成机制等信息，本项目将对其进行单分子13C 和14C分析。本研究选择珠江三角洲为研究靶区，旨在1）掌握其大气降水中低分子有机酸污染水平与组成特征；2）基于13C和14C示踪技术，联合其它示踪技术及源解析方法，查明该地区低分子有机酸的碳来源及形成机制信息，定量估算当代生物碳与化石碳的相对贡献；3）探究低分子有机酸来源的时空变化规律和影响因素。

大气中低分子有机酸是挥发性有机物的重要组分，对大气化学组成、气候变化、生态环境具有影响。其主要的汇是湿沉降，其化学组成和来源复杂，识别其来源是制定大气污染防治措施的科学依据。稳定碳同位素(13C)是示踪光化学过程和大气老化过程的良好指标，放射性碳同位素（14C）是有效识别并定量化石碳和当代生物碳对低分子有机酸相对贡献的强有力工具。为获得更详细大气降水中低分子有机酸来源及形成机制等信息，本项目将对其进行单分子13C 和14C分析。本研究以珠江三角洲为研究靶区，在1）获得了其大气降水中低分子有机酸污染水平与组成特征；2）基于双碳同位素（13C和14C）示踪技术，查明了该地区低分子有机酸的碳来源及形成机制信息，定量估算了当代生物碳与化石碳的相对贡献；3）探明了低分子有机酸来源的时空变化规律和影响因素。国内首次建立了大气气溶胶二元酸羧酸单体碳十四分析方法, 使得我们环境碳十四实验室成为全球第二个能够独立分析二元羧酸单体碳十四实验室，为我国大气14C 来源示踪研究提供了技术支撑。世界首次实现了环境大气中萘的三元同位素组成（δ13C，Δ14C 和 δ2H）测量，并用其对我国京津冀区域大气中的萘进行了源解析，指出化石源料是京津冀大气萘的主要来源，为京津冀地区大气精准防污减排提供了科学依据。