基于小波变换的武汉市PM_(2.5)、PM_(10)与臭氧污染特征

Studies on characteristics of PM_(2.5),PM_(10) and ozone pollution in Wuhan based on wavelet transform

为验证城市空气污染物排放及协同控制后的周期性规律,利用小波变换对武汉市2013~2020年共计2421d的逐日PM_(2.5)、PM_(10)及臭氧浓度数据进行分析.结果表明:可吸入颗粒物污染情况逐年改善,PM_(2.5)浓度年均值由80.5μg/m^(3)降至45.3μg/m^(3),超标比例由44%降至11%;PM_(10)浓度年均值由113.6μg/m^(3)降至72.6μg/m^(3),超标比例由22%降至2%.臭氧污染未有明显改善,浓度年均值在90~100μg/m^(3)间波动.PM_(2.5)、PM_(10)与臭氧浓度均表现出明显的周期性,PM_(2.5)浓度主周期300d、次周期140d左右;PM_(10)浓度主周期300d、次周期125d左右;臭氧浓度主周期300d、次周期143d左右.PM_(2.5)与PM_(10)的周期与位相均相似,表明武汉市PM_(2.5)与PM_(10)整体颗粒物污染行为更为一致;PM_(2.5)、PM_(10)与臭氧周期性相似,但位相有差异.0~64d左右的短周期内表现出正相关性;300d左右的长周期表现出负相关性.

In order to verify the periodic law after the cooperative control of urban air pollutants emission,wavelet transform was used to analyse daily PM_(2.5),PM_(10)and ozone concentration data of 2421 days(d)from 2013 to 2020 in Wuhan.The results are as follows:Inhalable particulate matter pollution had been reduced year by year.From 2014 to 2019,the annual average concentration of PM_(2.5)had reduced from 80.5μg/m^(3) to 45.3μg/m^(3),and that of PM_(10)had reduced from 113.6μg/m^(3) to 72.6μg/m^(3),which means the excessive rate of PM_(2.5)was reduced from 44%to 11%,and that of PM_(10)was reduced from 22%to 2%.The ozone pollution had kept unabated,with the annual average concentration of ozone fluctuating between 90μg/m^(3) to 100μg/m^(3).The concentration of all three kinds of pollutants displayed clear periodicity.PM_(2.5),PM_(10)and ozone concentration displayed with a same primary period of 300d.On the contrary,the secondary period of the three pollutants were 140d,125d,and 143d respectively.PM_(2.5)and PM_(10)had similar periods and phases,which indicates that pollution behaviours of both particulate matters are consistent.Furthermore,the concentration of the three pollutants had a positive correlation was revealed in short period(0~64d),whereas a negative correlation in long period of about 300d.