合肥市PM2.5浓度时空分布特征及影响因素分析

Temporal and Spatial Distribution Characteristics and Influencing Factors of PM2.5 Concentrationin Hefei City

利用2017年合肥市污染监测站点PM2.5浓度数据、气象数据以及土地利用类型数据,结合随机森林算法(RF)与土地利用回归模型(LUR),模拟合肥市PM2.5浓度空间分布,并利用主成分分析法对PM2.5影响因素进行分析。结果表明:(1)合肥市PM2.5浓度日变化特征大致呈双峰变化,春季、夏季及秋季的峰值多出现在8∶00~9∶00,而冬季的峰值则出现在10∶00~11∶00。低谷值大致都出现在15∶00~17∶00。全年PM2.5浓度变化趋势与春季类似。夏季PM2.5浓度变化最为平稳。(2)2017年合肥市PM2.5浓度分布由城市中心向外减弱,形成北高南低,西高东低的空间分布格局。(3)影响因素方面,PM2.5浓度变化与降水、风速以及相对湿度等呈负相关关系,日照对PM2.5浓度的影响较大,气压及其他污染物与PM2.5浓度呈正相关关系,其中NO2对PM2.5浓度的影响力度较大。

With the acceleration of urbanization,air pollution has become one of the major problems faced by every city.We used the concentration data,meteorological data and land use type data of 2017 PM2.5 monitoring station in Hefei,and we combined the random forest algorithm(RF)and land use regression model(LUR),to simulated the spatial distribution characteristics of PM2.5 concentration in Hefei.And the influencing factors of PM2.5 were analyzed by principal component analysis.The results showed that:(1)The daily variation characteristics of PM2.5 concentration in Hefei City showed two peaks,most of which appeared at 8∶00-9∶00 in spring,summer and autumn,while appeared at 10∶00-11∶00 in winter.The low values are generally between 15∶00 and 17∶00.The change trend of PM2.5 concentration in the whole year is similar to that in spring.The change of PM2.5 concentration is the most stable in summer.(2)In 2017,the concentration distribution of PM2.5 in Hefei weakened from the city center to the outside,forming a spatial distribution pattern of high in the north and low in the south,high in the West and low in the East.(3)In terms of influencing factors,the change of PM2.5 concentration is negatively correlated with precipitation,wind speed and relative humidity,sunlight has a greater influence on PM2.5 concentration,air pressure and other pollutants have a positive correlation with the change of PM2.5 concentration,and NO2 among atmospheric pollutants has a greater influence on the change of PM2.5 concentration.