天津冬夏季PM_(2.5)中二次无机离子的特征及重污染事件分析--基于连续两年的观测  

Characteristics of secondary inorganic ions in PM_(2.5)and study of heavy pollution events in winter and summer in Tianjin-Based on observations for two consecutive years

作　　者：郝新妮 肖浩[1] 李亲凯 丁士元 李晓东[1] HAO Xinni;XIAO Hao;LI Qinkai;DING Shiyuan;LI Xiaodong(School of Earth System Science,Tianjin University,Tianjin,300072,China)

机构地区：[1]天津大学地球系统科学学院,天津300072

出　　处：《环境化学》2022年第10期3288-3298,共11页Environmental Chemistry

基　　金：国家自然科学基金(41773006)资助.

摘　　要：本研究于2018、2019年的1月和7月在天津市采集PM_(2.5)样品,测定并分析了PM_(2.5)及水溶性无机离子浓度,并结合气象因素及氮/硫氧化率,揭示4次重污染过程SO_(4)^(2−)、NO_(3)^(−)的二次转化机制.结果表明,2018及2019年冬季天津市PM_(2.5)浓度均低于2017年的,但夏季PM_(2.5)浓度变化不明显,这可能是冬季受“代煤工程”的影响.SNA(SO_(4)^(2−)、NO_(3)^(−)、NH_(4)^(+))是水溶性离子的主要组分,冬季NO_(3)^(−)占比最高,而夏季SO_(4)^(2−)最高,并且浓度呈现出昼夜差异,这可能是受光照强度、温度及相对湿度等气象因素的影响.此外,冬季SNA主要以(NH_(4))_(2)SO_(4)、NH_(4)NO_(3)和NH_(4)Cl的形式存在,而夏季主要以(NH_(4))_(2)SO_(4)和NH_(4)NO_(3)的形式存在.冬季NH_(4)NO_(3)的质量浓度明显高于(NH_(4))_(2)SO_(4),夏季样品呈现相反的特征.污染天NH_(4)NO_(3)的浓度明显升高,说明硝酸铵的升高是导致PM_(2.5)浓度升高的关键.此外,4次重污染事件中,SO_(4)^(2−)、NO_(3)^(−)的生成机制有所不同,冬季污染的形成主要受到相对湿度的影响,而夏季除相对湿度外,还受到O_(3)及温度的影响.This study has collected the PM_(2.5)samples in January and July of 2018 and 2019 in Tianjin.PM_(2.5)concentrations and water-soluble inorganic ions in the samples were measured,together with information such as meteorological conditions and nitrogen/sulfur oxidation rate,to elucidate the secondary conversion mechanism of SO_(4)^(2−)and NO_(3)^(−)in heavy pollution processes.The study reveals that the PM_(2.5)concentrations in winter of 2018 and 2019 were lower than those in 2017,while the change of PM_(2.5)concentrations in two summers was not significant.This temporal variation might be related to the Coal Substitution Project in winter.SNA(SO_(4)^(2−)、NO_(3)^(−)、NH_(4)^(+))is the main component of water-soluble ions.NO_(3)^(−)dominated SNA in winter while SO_(4)^(2−)was dominant in summer.The concentration of SNA also showed a diurnal difference.These variances might be due to the different meteorological factors such as light intensity,temperature and relative humidity.In addition,SNA mainly existed in the forms of(NH_(4))_(2)SO_(4),NH_(4)NO_(3)and NH_(4)Cl in winter,but only(NH_(4))_(2)SO_(4)and NH_(4)NO_(3)in summer.The mass concentration of NH_(4)NO_(3)was obviously higher than that of(NH_(4))_(2)SO_(4)in winter,but the opposite characteristic was present in summer.The NH_(4)NO_(3)concentration increased significantly in the polluted days,indicating that the increase of NH_(4)NO_(3)was the key factor for the increase of PM_(2.5)concentration.Furthermore,the formation mechanism of SO_(4)^(2−)and NO_(3)^(−)was different in the four heavy pollution events.The pollution was mainly affected by relative humidity in winter,but relative humidity,O_(3)and temperature in summer.

关 键 词：PM_(2.5) SNA 形成机制 重污染事件 污染特征 天津 

分 类 号：X513[环境科学与工程—环境工程]