四川盆地PM_(2.5)特征及污染参数关联分析

Analysis of PM_(2.5) Characteristics and the Correlation with Pollution Parameters in Sichuan Basin

定量分析四川盆地PM2.5污染时空分布的总体特征,文章利用2015-2018年18个城市的地面台站数据与污染监测数据进行研究。结果表明:2015-2018年期间,PM2.5的主要污染区域分布在盆地西南部成都平原经济区,以成都和自贡为2个高值中心,且PM2.5浓度具有明显的季节变化特征,分别为冬季(77.98μg/m3)>春季(45.25μg/m3)>秋季(39.30μg/m3)>夏季(29.16μg/m3)。文章选取9个主要城市的风速、温度、湿度、气压4项气象因子进行分析,得出各地PM2.5浓度与温度和风速均呈现负相关,气压表现为正相关,湿度相关性随地形变化波动较大,整体影响小。同时采用罗氏法和风速积分法计算了9个城市的混合层高度和通风系数这2个污染气象参数。得到的结论是:混合层高度总体呈现双峰双谷特征,通风系数与混合层高度变化特征一致,二者与PM2.5浓度均呈明显负相关。选取2017年1月1-6日成都市全域型重污染过程进行个例分析,该次过程PM2.5浓度逐日平均值维持在181μg/m3以上,盆地前期处于静小风状态,整体湿度大,贴地逆温频率达66.7%,后期气象条件逐步转好。

In order to quantitatively analyze the overall characteristics of spatial and temporal distribution of PM2.5 pollution in Sichuan Basin,the meteorological observation data and near-surface PM2.5 observation data of 18 cities in 2015-2018 are selected for research.The results indicate that during 2015-2018,the main pollution areas of PM2.5 are located in Chengdu Plain Economic Zone in the southwest of the basin,with Chengdu and Zigong as two high value centers.And the concentration of PM2.5 has obvious seasonal variation characteristics,which are respectively winter(77.98μg/m3)>spring(45.25μg/m3)>autumn(39.30μg/m3)>summer(29.16μg/m3).In this paper,the four meteorological factors of wind speed,temperature,humidity and air pressure in nine major cities are selected for analysis.It is found that concentration of PM2.5 is negatively correlated with temperature and wind speed,and the air pressure is positively correlated.The correlation of humidity fluctuates greatly with the change of terrain,and the overall impact is small.At the same time,Roche method and wind speed integral method are used to calculate the mixed layer height and ventilation coefficient of nine cities.The conclusion is that the height of the mixed layer shows the change characteristics of two peaks and two valleys,the ventilation coefficient is consistent with the change characteristics of the height of the mixed layer,and both of them are negatively correlated with the concentration of PM2.5.A case occurred in the all areas of Chengdu during 1 to 6 January 2017 was conducted.The daily average value of PM2.5 was maintained above 181μg/m3.In the early stage,the basin was in a light breeze,the humidity was high,and the frequency of ground inversion was 66.7%.In the later stage the meteorological conditions gradually improved.