关中地区含氮气溶胶的时空分布、来源及健康影响

Nitorgen-containing aerosols play an important role in the biogeochemical cycle of nitrogen and strongly affect air quality, climate and human health. As one of the biggest nitrogen emitters, the atmospheric deposition of nitrogen in China increased by about 60% from 1980s to 2000s, with the concentration 5-100 time higher than that in the US and Europe. Quantitative understanding of the environmental and health effects of the nitrogen-containing aerosols requires a detailed knowledge of their composition, sources, spatial and temporal variation. In this project, we plan to take one year-round (four seasons) PM2.5 aerosol samples simultaneously at the heavily polluted Guanzhong region, China including four urban sites, three rural sites and one background site. The total nitrogen, total water insoluble nitrogen, total water soluble inorganic nitrogen and total water soluble organic nitrogen will be quantified to investigate their spatial and temporal distribution. Correlations of different nitrogen component with species of known source will be studied to get insights into the potential sources of nitrogen-containing aerosols. Further, the excess cancer risk of certain nitrogen-containing organic aerosols will be investigated in terms of their spatial and temporal variation. This will improve our understanding of the potential health impact of nitrogen-containing aerosols. The resutls obtained will also provide knowledge for the mitigation of nitrogen emissions in China and the necessary data for improved model simulation of the environmental and health effects of aerosols.

含氮气溶胶在氮的生物地球化学循环中发挥重要作用，影响空气质量、气候和人类健康。中国是氮排放大国，其大气氮沉降比上世纪80年代增长了近60%，是欧美国家的5-100倍。为了定量认识含氮气溶胶的环境和健康效应，并制定有针对性的氮减排策略，需要了解其化学成分、来源、空间分布和季节性变化。本研究拟在污染严重的关中地区8个采样点(4个城市点、3个郊区点、1个背景点)进行为期一年的同步观测，获得细粒子气溶胶PM2.5中总氮、非水溶性氮、水溶性无机氮和水溶性有机氮的时空分布特征与季节变化趋势，探讨含氮气溶胶各组分的地球化学行为特征及其与主要排放源的定量关联，揭示含氮气溶胶可能来源，并通过对比分析几类含氮有机物潜在的致癌等效因子在不同区域和季节的变化，认识含氮有机气溶胶潜在的健康影响，为政府制定有针对性的氮减排措施提供科学依据，并为模式研究提供必要数据。

含氮气溶胶在氮的生物地球化学循环中发挥重要作用，影响空气质量、气候和人类健康。中国是氮排放大国，其大气氮沉降比上世纪80年代增长了近60%，是欧美国家的5-100倍。定量含氮气溶胶的化学成分、来源、空间分布和季节性变化，对认识含氮气溶胶的环境和健康效应，并制定有针对性的氮减排策略具有重要意义。本项目已建立并优化PM2.5中有机胺分析的两种方法，并在西安地区开展大气细颗粒物采样，获取西安地区水溶性氮（WSN）浓度均值为677 nmol N m-3，水溶性有机氮（WSON）浓度均值为300 nmol N m-3，水溶性无机氮（WSIN）浓度均值则为377 nmol N m-3，其中WSIN和WSON的浓度呈现秋冬季高，夏季低的季节特征。通过Pearson分析表明，二次形成和生物质燃烧可能是西安地区WSON的重要贡献来源。同时，项目对西安地区大气中含氮组分之一大气亚硝酸（HONO）进行测量并解析其来源，观测期HONO浓度在0.02-4.3 ppb之间，平均值为1.1 ppb，其中夜间HONO主要来自于NO2非均相转化，其次是NO和OH的气相反应和机动车直接排放，日间HONO的生成主要受未知源主导（对HONO贡献为61%），这一未知源可能与光增强的NO2转化有关。此外，项目还对青海湖夏季的含氮气溶胶进行了定量，结果发现总氮质量浓度的平均值为1.15μg•m-3, 约占PM2.5的6%左右。水溶性无机氮质量浓度的平均值为0.76 μg•m-3，占总氮质量的66.5%，其中NH4+-N在青海湖含氮气溶胶中所占比例较高。