合肥市颗粒物和气象条件对大气能见度的影响研究

利用2019—2021年合肥市气象参数、颗粒物浓度、颗粒物化学组分、颗粒物散射系数、颗粒物粒径谱等的逐小时观测数据,分析了合肥市大气能见度变化趋势及其影响因素。结果表明,2019—2021年,合肥市能见度呈逐年上升的总体特征,并且在季节变化上呈现为夏高冬低,在日变化上呈现为午后最高、夜间最低。相关性分析结果显示,合肥市能见度与颗粒物浓度、相对湿度均呈显著负相关关系,且能见度与相对湿度的相关程度比与颗粒物浓度的相关程度高15.5%~219.2%。相对湿度是直接影响合肥市能见度的主要因素之一,而温度、风速对能见度的间接影响作用相对较小。能见度与颗粒物特性关系研究结果表明:能见度与水溶性离子的相关程度高于与碳质组分的相关程度;当能见度处于较低水平时,能见度与PM_2.5主要组分浓度的相关性明显减弱,相对湿度、超细颗粒物占比、水溶性离子含量和碳质组分含量等因素对能见度的影响逐渐凸显;在较高PM_2.5浓度环境条件下,颗粒物散射系数的显著变化是导致能见度降低的主要原因;小粒径颗粒物对合肥市大气能见度的影响程度相对较高,应优先大幅度降低PM_1.0浓度。

Effects of Particulate Matter and Meteorological Conditions on Atmospheric Visibility in Hefei

Based on the hourly observation data of meteorological parameters,particle concentration,chemical composition,scattering coefficient and particle size distributions in Hefei from 2019 to 2021,the variation trends of visibility and its influencing factors in Hefei were analyzed in this paper.The results indicated that the visibility was generally increasing from 2019 to 2021 in Hefei.In the seasonal variation,visibility was high in summer and low in winter,and in the diurnal variotion,visibility was highest in afternoon and lowest at night.The results of correlation analysis showed that visibility was significantly negatively correlated with particle concentration and relative humidity,and the correlation between visibility and relative humidity was 15.5%-219.2% higher than that of particle concentration.And relative humidity was one of the main factors that directly affected the visibility of Hefei,while the indirect effect of temperature and wind speed on visibility was relatively low.According to the research and analysis of visibility and particle characteristics,the correlation between visibility and water-soluble ions were higher than that of carbonaceous components.When the visibility was low,the correlation between visibility and the concentration of main components of PM_2.5 were significantly weakened,and factors such as relative humidity,ultrafine particles,water-soluble ions and carbon components might gradually highlighted the effect on the visibility.Under the conditions of high PM_2.5 concentration,the significant change of particle scattering coefficient was the main reason for the reduction of visibility.At the same time,the influence of fine particles on atmospheric visibility was relatively high in Hefei.Therefore,the priority should be given to significantly reducing the PM_1.0 concentration.