合肥市冬季PM_(2.5)水溶性离子污染特征分析

Analysis of Water-Soluble Ions Pollution Characteristics in PM_(2.5)During Winter in Hefei

为进一步了解合肥市冬季污染期间PM_(2.5)水溶性离子污染特征,选取合肥市2022年1月份的PM_(2.5)和水溶性离子(NO_(3)^(-)、NH_(4)^(+)、SO_(4)^(2-)、Cl^(-)、Na^(+)、K^(+)、Ca^(2+)、F^(-)和Mg^(2+))在线监测数据,对比分析了监测时段中污染日和非污染日的浓度变化特征。结果表明:监测期间合肥市PM_(2.5)平均浓度为68.4±5.9μg/m^(3),污染日平均浓度显著偏高,为104.0±4.9μg/m^(3),为非污染天的2.1倍。不同污染过程中PM_(2.5)的小时变化差异较为显著。水溶性离子平均质量浓度为38.0±3.3μg/m^(3),占PM_(2.5)质量浓度的55.9%,离子浓度从高到低排序依次是NO_(3)^(-)>NH_(4)^(+)>SO_(4)^(2-)>Cl^(-)>Na^(+)>K^(+)>Ca^(2+)>F^(-)>Mg^(2+)。SNA是离子中最主要的组分,非污染天和污染天占比分别为56.4%和54.7%。NO_(3)^(-)和SO_(4)^(2-)与NH4+的相关性显著,在PM_(2.5)中主要结合方式为NH_(4)NO_(3)和(NH_(4))_(2)SO_(4)。后向轨迹表明,冬季PM_(2.5)污染主要来自北部京津冀地区、东部江苏中部城市群和本地区域。

Based on the mass concentration of PM_(2.5)and water-soluble inorganic ions(NO_(3)^(-),NH_(4)^(+),SO_(4)^(2-),Cl^(-),Na^(+),K^(+),Ca^(2+),F^(-)and Mg^(2+))monitoring data in real time in Hefei urban area during January in 2022and the variation characteristics of PM_(2.5),its major water-soluble ion components were analyzed between clean and pollution days.The results showed that the average mass concentration of PM_(2.5)was(68.4±5.9)μg/m^(3)during the monitoring period.However,the pollution of PM_(2.5)was serious in pollution days.The average mass concentration of PM_(2.5)was(104.0±4.9)μg/m~3,which was 2.1times that of non-pollution days.The hourly variation of PM_(2.5)were significantly different in different pollution processes.The average total mass concentration of the water-soluble ions was(38.0±3.3)μg/m^(3),accounting for 55.9%of PM_(2.5).The ion concentrations presented the order of NO_(3)^(-)>NH_(4)^(+)>SO_(4)^(2-)>Cl->Na^(+)>K^(+)>Ca^(2+)>F^(-)>Mg^(2+).SNA was the most important component,accounting for more than 50%of the total water-soluble ions,but there was difference in different pollution episodes.Both NO_(3)^(-)and SO_(4)^(2-)had positive correlation with NH_(4)^(+),and they existed in the form of NH_(4)NO and(NH_(4))_(2)SO_(4).The backward trajectory showed that the PM_(2.5)mainly came from Beijing-Tianjin-Hebei Region,city groups in central Jiangsu Province and local area in winter.