Xu Qingcheng, Wang Shuxiao, Jiang Jingkun, Bhattarai Noshan, Li Xiaoxiao, Chang Xing, Qiu Xionghui, Zheng Mei, Hua Yang, Hao Jiming
State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China; State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing 100084, China.
State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China; State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing 100084, China.
Sci Total Environ. 2019 Nov 1;689:1293-1303. doi: 10.1016/j.scitotenv.2019.06.294. Epub 2019 Jun 20.
Water-soluble inorganic ions (WSI), a major component of PM, often increased rapidly during the haze event in Beijing. Sulfate (SO), Nitrate (NO), and Ammonium (NH) are three main components of WSI. Since year 2015, sulfate concentrations in PM has gradually decreased owing to the effective control of SO emissions. However, the contribution of nitrate to PM has significantly increased during haze events in Beijing at the same time. In this study, a highly time-resolved online analyzer (Monitor for Aerosols and Gases, MARGA) was employed to measure the WSI in PM in Beijing from 5 February to 15 November 2017. Three typical haze events during this sampling period were investigated. During heavy pollution episodes in winter, nitrate concentrations increased from 7.5 μg/m to 45.6 μg/m (45.0% of WSI), while sulfate increased from 4.2 μg/m to 20.1 μg/m (19.8% of WSI). This indicated that nitrate is more important than sulfate as a driver for the growth of PM during the period of heavy air pollution in winter. Nitrate also dominates the increase of WSI in the pollution episodes in autumn, with an average concentration of 52.5 μg/m, and contributed up to 67% of WSI. The average concentration ratio of NH to SO was higher in autumn (1.02) than that in summer (0.74) and close to that in winter (1.00). This is mainly because the emission control of coal combustion in Beijing and surrounding areas results in an NH-rich and SO-lean atmosphere, which promoted the formation of ammonium nitrate. Our study indicates that nitrate has become the most important component of WSI in PM and is driving the rapid growth of PM concentrations during heavy pollution episodes in Beijing. Therefore, more efforts shall be made to reduce the nitrogen oxide and ammonia emissions in Beijing and surrounding areas.
水溶性无机离子（WSI）是颗粒物的主要成分，在北京雾霾期间常常迅速增加。硫酸盐（SO）、硝酸盐（NO）和铵盐（NH）是WSI的三个主要成分。自2015年以来，由于有效控制了SO排放，颗粒物中硫酸盐浓度逐渐下降。然而，与此同时，在北京雾霾期间硝酸盐对颗粒物的贡献显著增加。本研究中，使用了一台高时间分辨率在线分析仪（气溶胶和气体监测仪，MARGA）来测量2017年2月5日至11月15日北京颗粒物中的WSI。对该采样期间的三次典型雾霾事件进行了调查。在冬季重度污染期间，硝酸盐浓度从7.5μg/m增加到45.6μg/m（占WSI的45.0%），而硫酸盐浓度从4.2μg/m增加到20.1μg/m（占WSI的19.8%）。这表明在冬季重度空气污染期间，硝酸盐作为颗粒物增长的驱动因素比硫酸盐更重要。硝酸盐在秋季污染事件中也主导了WSI的增加，平均浓度为52.5μg/m，占WSI的比例高达67%。秋季NH与SO的平均浓度比（1.02）高于夏季（0.74），接近冬季（1.00）。这主要是因为北京及周边地区煤炭燃烧排放控制导致大气中NH含量高而SO含量低，这促进了硝酸铵的形成。我们的研究表明，硝酸盐已成为颗粒物中WSI的最重要成分，并在北京重度污染事件期间推动了颗粒物浓度的快速增长。因此，应在北京及周边地区加大力度减少氮氧化物和氨的排放。
