华北地区农村面源大气污染排放对区域空气质量的影响

The essential reason for the currently frequent haze raiding on the North China Plain (NCP) was ascribed to fine particle pollution, but the knowledge about the sources of the fine particles is still unclear. Almost all relative studies currently focus on pollutants emitted from cities and industries, whereas the emissions from the rural area in the NCP are almost neglected. Our observation in recent years found that the frequent haze formation periods closely relate with the periodically strong emissions of pollutants from the rural area in the NCP, mainly focusing on summer season of June-July during wheat harvesting period, autumn season of September-October during maize harvesting period and winter season during farmers' heating period by combustion of coal. Focusing on the three periods of strong pollutants emission from the rural area, the project applied will conduct the comparison study about the absolute concentrations and the relative composition of water soluble components in the atmospheric particles collected over Beijing and a rural area.The influence of the emission of pollutants from the rural area in the NCP on regional air quality will be diagnosed by the comparison results. In addition, the emission factors of key pollutants from the major sources in the rural area will be investigated,and the total emission and the proportion will be estimated. Furthermore，a practical control measure will be put forward for reducing pollutants emissions from straw returning agricultural field and from coal combustion during winter season in the rural area of the NCP. The project applied will provide a novel and practical scientific idea for improving the air quality in the NCP.

华北地区当前灰霾频繁暴发的根本原因是细粒子污染问题，但人们关于该区域大气中细粒子来源的认识仍然不清楚。所有相关研究当前主要集中在城市区域和工业排放，而广大面积的农村大气污染排放几乎被忽视。我们通过近几年的观测发现华北地区灰霾频繁暴发期与农村阶段性大气污染物强排放密切相关，主要集中在夏季6-7月小麦收割季节、秋季9-10月玉米收割季节和燃煤取暖的冬季。该申请项目针对农村大气污染物强排放的三个阶段，对比研究北京市和典型农村大气颗粒物中水溶性组分的绝对含量和相对组成，诊断华北地区农村面源大气污染排放对区域空气质量的影响；测定农村主要污染源中关键污染物的排放因子，估算其排放总量及其在该区域所占份额。进而针对华北地区当前秸秆还田以及冬季燃煤取暖所造成的区域空气质量恶化问题，提出一套可行的华北地区农村面源大气污染排放控制措施。该项目的实施将对有效改善华北地区空气质量提供新的科学思路，具有重要现实意义。

在我国灰霾重污染的华北典型城市（北京市区、保定市区及望都县城）和农村（东白陀村）地区，利用中流量采样器对大气颗粒物各组分进行为期近4年的连续观测（2014-2018年），系统研究了农村面源大气污染排放对区域空气质量的影响。基于城市站点和农村站点大气PM2.5中水溶性离子的对比结果，表明农民活动阶段性排放（夏季作物收割与施肥；秋季农作物收割、秸秆燃烧和土地翻耕；冬季采暖散煤燃烧等）对北京大气水溶性离子具有明显贡献；根据化学质量闭合法，在北京、保定、望都及东白陀四个站点2015年居民散煤燃烧排放对大气中一次PM2.5颗粒物的贡献分别可达32%、49%、43%和58%；基于冬季北京站点PM2.5中关键物种的小时变化及重污染期间二次气溶胶的污染特征，发现在严重污染时期大气中SO42-生成产率受H2O2显著影响，且仍存在未知的SO42-生成机制。结合煤炭秸秆等固体燃料的燃烧特点，研发了共燃技术，通过备燃区、过渡区、燃烧区的合理布局，实现了煤炭中挥发组分和固定碳的完全燃烧，极大降低了（>90%）颗粒物、OC/EC、NH3、VOCs等可燃性大气污染物的排放。基于共燃技术，开发了适合华北农民冬季取暖煤炉，并在北京、保定、石家庄以及徐州等地开展了广泛的应用示范。基于以上研究，撰写了《京津冀散煤污染治理的制约因素与对策》的建议稿，被《人民日报内参》采用，并获得国务院副总理张高丽的批示。