新乡市大气PM2.5中水溶性离子的污染特征、来源解析及气象影响分析

为探究新乡市大气PM_2.5中水溶性无机离子（WSIIs）的污染演变、来源特征及其气象影响，利用URG-9000在线监测系统于2022年1月（冬季）、4月（春季）、7月（夏季）和10月（秋季）对PM_2.5组分进行在线观测.结果表明，TWSIIs（总水溶性无机离子）与PM_2.5的季节变化特征一致，季度ρ（TWSIIs）均值变化范围为19.62~72.15 μg·m^-3，在PM_2.5中的占比超过66%，WSIIs是大气PM_2.5的重要组分.年均NO₃^-/SO₄^2-（质量浓度比）为2.11，且呈现逐年增加的趋势，移动源对二次无机气溶胶（SNA）的影响不容忽视，年均[NH₄⁺]/[NO₃^-]（量比）为1.95，说明农业源是大气中氮的主要贡献者.后向轨迹分析表明，在盛行东北风且风速较大时，PM_2.5中Ca²⁺和Mg²⁺的浓度较高.低温高湿的气象条件下（T<8℃，RH>60%），SOR和NOR值均较高，更多的气态前体物SO₂和NO₂转化为颗粒态的SO₄^2-和NO₃^-.与SOR不同，在高温条件下（T>24℃），NOR并没有表现出高值特征，与高温条件下NH₄NO₃的分解有关.结合PMF和后向轨迹分析，来自西北方向的气团所对应的扬尘源对WSIIs的贡献较大，观测站点周边区域的低空低速气团所对应的二次硫酸盐以及二次硝酸盐和生物质源对WSIIs的贡献较大.

Pollution Characteristics, Source Apportionment, and Meteorological Response of Water-soluble Ions in PM2.5 in Xinxiang, North China

Pollution variation, source characteristics, and meteorological effects of water-soluble inorganic ions (WSIIs) in PM_2.5 were analyzed in Xinxiang city, Henan Province. PM_2.5 samples and their chemical components were monitored online by using URG-9000 in four seasons:winter (January, 2022), spring (April, 2022), summer (July, 2022), and fall (October, 2022). The results showed that the TWSIIs had the same seasonal fluctuations as PM_2.5. The average seasonal concentrations of WSIIs ranged from 19.62-72.15 μg·m^-3, accounting for more than 60% of PM_2.5, demonstrating that WSIIs were the major components of PM_2.5. The annual concentration value of NO₃^-/SO₄^2- was 2.11, which showed an increasing trend, suggesting predominantly mobile sources for secondary inorganic aerosols (SNA). Further, the molar concentration value [NH₄⁺]/[NO₃^-] was 1.95, demonstrating that agriculture emissions were the dominant contributors to atmospheric nitrogen. Furthermore, the backward trajectory analysis showed that the concentrations of Ca²⁺ and Mg²⁺ were higher when the northeasterly wind prevailed and the wind speed was high. High values of SOR and NOR were correlated with low temperatures and high relative humidity (T < 8℃, RH > 60%), demonstrating that more gaseous precursors were converted into sulfate and nitrate. At high temperatures (T > 24℃), there was no apparent high NOR value like that for SOR, mainly due to the decomposition of NH₄NO₃ at high temperatures. Finally, backward trajectories associated with the PMF-resolved results were used to explore the regional transport characteristics. The results illustrated that dust sources in the study areas were mainly influenced by air trajectories originating from the northwest regions, whereas secondary sulfate, secondary nitrate, and biomass sources contributed more to WSIIs when wind speed and altitude air masses were low in the area surrounding the observation site.