Analysis On The Characteristics Of Spring Aerosol Pollution And Depolarization Ratio In Urban Areas Of East Asia-Fukuoka, Japan

In recent years,the regional transportation of atmospheric pollutants has become a hot spot。This paper analyzes the aerosol pollution characteristics,depolarization ratio changes and backward trajectory analysisto determine its source of pollution in Fukuoka of Japan,and provides a certain reference for the regional transportation problems in East Asia.This article takes Fukuoka,Japan as an example.We used an continuous dichotomous aerosol chemical speciation analyzer（ACSA-12）and polarization optical particle counter（POPC）on the roof of the third floor of the Institute of Applied Mechanics（33.51°N,130.50°E）of Kyushu University in the spring of 2014。Obtained PM_2.5,PM_2.5-10,and nitrate in the atmosphere(nitrate in PM_2.5is called fine mode nitrate,f NO₃);nitrate in PM_2.5-10is coarse mode nitrate,c NO₃),sulfate（f SO₄,c SO₄）,BC and single particle depolarization ratio data,through the spatial and temporal distribution characteristics and formation mechanism of aerosol chemical components,aerosol depolarization ratio change characteristics analysis,and air flow trajectory simulation to obtain the following main conclusion:（1）The Fukuoka area of Japan has experienced many pollution processes in the spring.The main pollutant is PM_2.5.The average daily concentration of PM_2.5-10in March is 13.8±12.5μg·m^-3in March,It can reach 63.5±21.5μg·m^-3in the sand-dust pollution day.The main contribution sources of PM_2.5come from fine sulfate and fine nitrate.The proportion of PM_2.5in polluting days(f NO₃/PM_2.5+f SO₄/PM_2.5)can reach up to 35.9%.The contribution of crude nitrate and crude sulfate to PM_2.5-10is small.（2）PM_2.5concentration has a tendency to increase in the afternoon,but it is not very obvious.The highest value appears at 16:00.The PM_2.5concentration on the rest day is greater than the concentration on the working day。On he rest day,The PM_2.5average concentration increased by 26%compared with the working day.The diurnal variation of fine nitrate（f NO₃）and black carbon（BC）is characterized by a double-peak structure,and its high value area corresponds to the morning and evening peaks.The daily average concentration of f NO₃on rest days is 21%higher than that on working days.The daily average concentration of BC on rest days is 11%higher than that on working days.Fine sulfate（f SO₄）and soluble organic carbon（f WSOC）have no obvious diurnal variation characteristics.The average daily concentration of f SO₄and f WSOC on rest days increased by 37.5%and 59.4%compared with working days,and f WSOC increased by 59.4%compared with working days。The depolarization ratio of particles with a particle size of 1μm and 3μm decreased by10%and 7%on the rest day compared with the working day,and their morphology was more regular than the particles with the same particle size on the working day,the depolarization ratio’s upper and lower quartile distances on the box chart of the day off of 1μm and 3μm are shorter,indicating that the distribution of depolarization ratios is more concentrated,and the last step shows that the fine particles are more affected by human activities and are more fully mixed.The concentration of PM_2.5and its related components is less affected by sea and land winds,and is more affected by local source emissions.（3）The PM_2.5-10concentration distribution has a clear trend of high day and low night,reaching the highest value at 16:00,and the concentration of the rest day increased by 20.6%compared with the concentration of the working day.The concentration of crude nitrate（c NO₃）has no obvious day and night changes on working days,and there is a tendency to increase significantly on the afternoon of the rest day.Its average concentration on the rest day is increased by 12.5%??compared with the working day.The concentration is 2-3 times the concentration of c NO₃on working days.PM_2.5-10and c NO₃concentrations have a clear upward trend at the weekend afternoon,the reason is that f NO₃reacts and converts to c NO₃under high temperature and high humidity conditions.（4）Among the three typical pollution days,the concentration of f NO₃and BC is the highest on the day with human activities as the main,the particles with a particle size of 3μm have the smallest depolarization ratio,the least dispersion and the most regular morphology.The appearance of coarse particles（5um）in the artificial pollution day is relatively regular.The concentration of c NO3 and c SO₄was the highest in the dust-type pollution day.The concentration of f SO₄was the highest in mixed pollution days.In the dust-type and mixed-type pollution days,the particles smaller than 3μm are more regular,and the particles with a particle size of 5μm appear irregular.（5）The main sources of pollution days in the Fukuoka area of Japan come from local source contributions,and some are from the Mongolia area to the south of China via China.The source of pollution on Clean Day comes from local source transportation and regional transportation from Russia and Mongolia.