降水和风对泰安地区PM_(2.5)浓度的影响及区域传输研究

Impacts of precipitation and wind on PM_(2.5)concentration and its region transport in Tai′an

利用泰安市2018—2019年降水、风和PM_(2.5)逐小时观测数据,分析了降水和风对PM_(2.5)浓度的影响,并对PM_(2.5)进行了源解析。结果表明:降水对PM_(2.5)有一定清除作用,降雨日PM_(2.5)平均质量浓度较非降雨日平均降低约7.2%,秋冬季节最为显著。降水对PM_(2.5)的清除率与降水强度、降水前PM_(2.5)初始浓度及降水时间均有关。当降水强度大于4 mm·h^(-1)时,清除率多在40%以上;当降水强度小于2 mm·h^(-1)、初始浓度低于75μg·m^(-3)或降水强度小于1 mm·h^(-1)、初始浓度在75—100μg·m^(-3)范围,且降水持续时间在5 h以内时容易出现PM_(2.5)浓度反弹现象。不同风向风速对泰安地区霾粒子清除也有明显差异,西南偏西风和东北偏东风更容易造成泰安地区霾污染,重污染期间风速超过5 m•s-1偏南风和风速超过3 m•s-1偏北风均对污染物具有有效清除作用。而区域风场相关矢结果表明重污染期间PM_(2.5)污染物主要从广西—湖南—江西一带、安徽南部及浙江北部在西南气流引导下传输至泰安地区,本地源贡献则较少。

Using the hourly observation data of precipitation,wind,and PM_(2.5)in Tai′an from 2018 to 2019,the impacts of precipitation and wind on PM_(2.5)concentration as well as the source of PM_(2.5)were analyzed.The results showed that precipitation has a certain scavenging effect on PM_(2.5).The average mass concentration of PM_(2.5)on rainy days is about 7.2%lower than that on non-rainy days,especially in autumn and winter.The scavenging rate of PM_(2.5)by precipitation is related to precipitation intensity,initial PM_(2.5)concentration before precipitation,and precipitation duration.The scavenging rate of PM_(2.5)is higher than 40%when the precipitation intensity is greater than 4 mm·h^(-1).The PM_(2.5)concentration tends to rebound under conditions of precipitation intensity<2 mm·h^(-1),or the initial PM_(2.5)concentration<75μg·m^(-3) and precipitation intensity<1 mm·h^(-1),or the initial PM_(2.5)concentration within the range of 75-100μg·m^(-3) and precipitation duration<5 h.Different wind directions and wind speeds show different impacts on the scavenging of haze particles in Tai′an.The west-southwesterly wind and the east-northeasterly wind are more likely to cause haze pollution in the Tai′an area.During heavy pollution,the southerly winds>5 m•s-1 and the northerly winds>3 m•s-1 can effectively remove pollutants.PM_(2.5)is mainly transported from Guangxi-Hu′nan-Jiangxi provinces,southern Anhui province,and northern Zhejiang province to Tai′an by southwesterly airflows,and less contribution is from the local emissions.