Status Study On AQI And PCDD/Fs In Atmosphere For Handan And Kaifeng Cities

In this study,the atmospheric PM_2.5,PM₁₀,the total PCDD/Fs-WHO₂₀₀₅-TEQ concentrations,PM_2.5-bound total PCDD/Fs-WHO₂₀₀₅-TEQ contents,and the gas-particle partitioning of PCDD/Fs,Concentrations and seasonal variation of six AQI pollutants in Handan City of Hebei Province and Kaifeng City of Henan Province between 2015 and 2017 were discussed.Then we explored the removal pathways of PCDD/Fs from the environment,such as:the atmospheric wet,dry,and total deposition fluxes and scavenging ratios.Finally,the effects of temperature,PM_2.5 concentration,PM₁₀0 concentration and total PCDD/Fs concentration on the total PCDD/Fs-WHO₂₀₀₅-TEQ dry deposition fluxes were investigated by sensitivity analysis.A regression analysis of the total PCDD/Fs-WHO₂₀₀₅-TEQ concentration and AQI was established to easily predict the trend of the total PCDD/Fs-WHO₂₀₀₅-TEQ concentration in ambient air.The specific research results can be divided into the following points:?1?From 2015²017,in Handan,the three-year average PM_2.5 concentrations in spring,summer,autumn and winter were 66.9,61.3,74.8,and 138?g m^�3,respectively,and averaged 85.3?g m^�3,which was 1.2 orders of magnitude higher than that in Kaifeng(71.1?g m^�3).The three-year average PM_2.5-bound total PCDD/Fs-WHO₂₀₀₅-TEQ content in spring,summer,autumn,and winter in Handan were 0.88,0.28,0.67,and 0.72 ng WHO₂₀₀₅-TEQ g^�1,respectively,and averaged 0.64ng WHO₂₀₀₅-TEQ g^�1,which was 1.1 order of magnitude higher than that in Kaifeng(0.57 ng WHO₂₀₀₅-TEQ g^�1).The three-year average fraction of gas phase total PCDD/Fs-WHO₂₀₀₅-TEQ concentrations in spring,summer,autumn,and winter in Handan were 26.4%,62.8%,28.9%,and 3.34%,respectively,and averaged 30.4%.The three-year average fraction of gas phase total PCDD/Fs-WHO₂₀₀₅-TEQ concentrations in Kaifeng?34.3%?was 1.1 order of magnitude higher than that in Handan?30.4%?.Positive correlations between the AQI and the total PCDD/Fs-WHO2005-TEQ concentration were found and their R² values in 2015,2016,and 2017 were 0.929,0.921,and 0.876,respectively.Therefore,the AQI can be used to roughly predict the level of total PCDD/Fs-WHO₂₀₀₅-TEQ in ambient air through the use of a regression equation in these two cities.?2?From 2016²017,the contribution fraction of dry deposition to the total PCDD/Fs-WHO₂₀₀₅-TEQ deposition flux ranged between 60.8%and 100%and averaged 80.4%.Dry deposition fluxes were more dominant than wet deposition fluxes.In terms of the seasonal variations in total PCDD/Fs-WHO₂₀₀₅-TEQ dry deposition fluxes?the mean values for 2016 and 2017?in Handan,those in spring,summer,fall,and winter were 1084,563,964,and 1325 pg WHO₂₀₀₅-TEQ m^�22 month^�1,respectively,while in Kaifeng,they were 963,428,715,and 1016 pg WHO₂₀₀₅-TEQ m^�2 month^�1,respectively.The total PCDD/FsWHO₂₀₀₅-TEQ deposition fluxes in winter was approximately 2.0 times of magnitude higher than that in summer.The sensitivity analysis of total PCDD/FsWHO₂₀₀₅-TEQ dry deposition fluxes in Handan and Kaifeng showed that the PM₁₀0 and PM_2.5 concentration were positively correlated sensitive factors.The second positively correlated sensitive factor was PCDD/Fs mass concentration.This was followed by the atmospheric temperature,and its effect was negatively correlated.The results of this study provide useful information that can be used to achieve more insights into both atmospheric deposition of total PCDD/Fs-WHO₂₀₀₅-TEQ and the sensitive factors for dry deposition fluxes.?3?From 2015²017,in Handan,the daily AQI ranged from 22 to 500 in 2015,from19 to 500 in 2016,and from 27 to 500 in 2017,for which the corresponding average values were 143,132 and 151,respectively.In Kaifeng,the daily AQI ranged from 25 to496 in 2015,from 20 to 420 in 2016,and from 21 to 434 in 2017,for which the corresponding average values were 129,124 and 131,respectively.The AQI were between 101 and 150,in Handan,PM_2.5,PM₁₀,and O₃ were the primary air pollutants.In Kaifeng,the primary air pollutants were PM_2.5,PM₁₀,NO₂,and O₃ in 2015;were PM_2.5,PM₁₀,and O₃ in 2016,and were PM_2.5,PM₁₀,and O₃ in 2017.When AQIs ranged between 151 and 200,in Handan,the primary air pollutants were PM_2.5,PM₁₀,and O₃ in both 2015 and 2016,and were PM_2.5,PM₁₀,NO₂,and O₃ in 2017.In Kaifeng,PM_2.5,PM₁₀,and O₃ were the primary air pollutants from 2015²017.When AQIs were between 201 and 300,in Handan,the primary air pollutants were PM_2.5 and PM₁₀ in2015 and were PM_2.5 and O₃ in 2017.In Kaifeng,the primary air pollutants comprised PM₁₀ in 2015,PM_2.5 and PM₁₀ in 2016,and PM_2.5 and O₃ at the same time.When the AQI values were between 301 and 500,which did not occur in Handan in 2015,the primary air pollutants comprised PM₁₀ in 2016,PM_2.5 and PM₁₀ in 2017,and in Kaifeng from 2015²017,PM_2.5,and PM₁₀ were the primary air pollutants.This study investigated the AQI values and corresponding primary pollutants in each season in more detail,the control strategies for these air pollutants will be more precisely.