【摘要】 大气细颗粒物(PM_2.5)与雾霾天气密切相关,PM_2.5吸附的有毒有害物质,可能给人体健康带来危害。二次水溶性无机离子(SNA,包括SO₄^2-、NO₃^-和NH₄⁺)是PM_2.5的重要组分,研究PM_2.5中SNA污染特征及形成和演化的影响因素,对认识雾霾污染的生消机制,提升人们的生活质量具有重要意义。利用在线气体及气溶胶成分监测系统（MARGA）观测了宁波市滨海地区春季、夏季和秋季大气PM_2.5中的SNA和气态污染物的变化趋势,并利用后向轨迹分析研究了不同气团影响下污染物的日变化规律。结果表明,观测期间,SNA在PM_2.5中的平均占比约为70.7%,NO₃^-是导致PM_2.5污染加重的主导离子。NO₃^-和SO₄^2-受气团传输影响较大,来自陆地气团的质量浓度普遍高于海洋气团,来自西北内陆方向的污染物输送是导致宁波空气质量下降的主要原因。宁波大气中的硫氧化率（SOR）较高,SO₄^2-主要由SO₂发生二次氧化反应生成;SO₄^2-的形成与相对湿度（RH）密切相关,SOR随着RH的增加而显著增大,当RH>85%时,大气中的硫氧化物绝大部分以SO₄^2-形式存在,SOR接近1;而温度变化对SOR无明显影响;来自西南与东部受海洋显著影响的气团SOR高于来自陆地气团的相应值。夏季RH普遍较高,西南方向气团影响下高浓度的气态污染物（NO₂、O₃、NH₃）可明显促进SO₄^2-的生成,一定程度上控制人为气态污染物的排放能有效减少SO₄^2-生成。与SOR比较而言,氮氧化率（NOR）和NO₃^-与温度、RH、气态污染物浓度等环境因素的关系比较复杂,暗示多种反应机理共同作用影响氮氧化物的转化。更多还原

【Abstract】 Severe haze weather is closely related to atmospheric fine particulate matter(PM_2.5), which could adsorb toxic and harmful substances, pose a severe danger to human health. Secondary water-soluble inorganic ions(SNA, including SO₄^2-, NO₃^-and NH₄⁺) are important components in PM_2.5. In order to control haze pollutant and improve people’s quality of life, it is of great significance to study the characteristics of SNA and the influencing factors of its formation and evolution in PM_2.5. A monitor for aerosols and gases in ambient Air（MARGA） was used to continuously measure SO₄^2-, NO₃^-and NH₄⁺ and trace gases at a coastal site in Ningbo. Based on the clusters analysis of back trajectory, the daily variations of SNA associated with different air mass originations were analyzed. It showed that 70.7% of PM_2.5 was SO₄^2-, NO₃^- and NH₄⁺ during the study period, and the elevated NO₃^- was the dominant ion during the polluted periods. The transmission of NO₃^- and SO₄^2-ions was greatly influenced by air masses.The SNA concentrations associated with the land air masses were significantly higher than that from the ocean air masses. The air mass from the northwest land was the main reason for the decline of air quality in Ningbo. The sulfur oxidation rate（SOR） was relatively high in Ningbo and SO₄^2- was mainly formed by secondary reaction activity. The formation of SO₄^2-was closely related to relative humidity（RH）, SOR increased significantly with the increase of RH, when RH>85%, SO₄^2-became the dominant form of atmospheric sulfur oxides, and SOR was close to 1. However, temperature had no obvious effect on SOR. The SOR associated with air masses from southwest and east, which were significantly affected by oceans, were higher than the corresponding values from terrestrial air masses. In summer, the high RH and the high concentration of gaseous pollutants（NO₂, O₃, NH₃） associated southwest air mass, would obviously promote the formation of SO₄^2-. Thus, we only can effectively reduce the formation of SO₄^2- through controlling the emission of anthropogenic gaseous pollutants to a certain extent. The relationships between nitrogen oxidation rate（NOR）, NO₃^- and environmental factors such as temperature, RH and gaseous pollution are more complicated comparing with SOR,which imply that there are several combination of reaction mechanisms affecting the transformation of nitrogen oxides.更多还原