[Interactive Effects of the Influencing Factors on the Changes of PM_2.5 Concentration Based on GAM Model]

In this paper,the generalized additive model (GAM) was introduced to analyze the interactive effects of the influencing factors on the change of PM_2.5 concentration during 2013-2015 in Nanjing city.The results showed as follows:PM_2.5 and its influencing factors appeared to follow normal distribution.There were strong correlations among the influencing factors,especially among the temperature (TEM),pressure (PRS) and water vapor pressure (VAP).For the single influencing factor GAM models of PM_2.5 concentration,all influencing factors passed the significance test.Moreover,the equation fitting degrees of SO₂,CO,and NO₂ were much higher.In the multiple influencing factors GAM models of PM_2.5 concentration,the contribution of the SO₂,CO,NO₂,O₃,precipitation (PRE),wind and relative humidity (RHU) to the change of PM_2.5 concentration was 73.9% with significant impacts on the change of PM_2.5 concentration.Based on the diagnostic analysis of the effect of multi factors on the change of PM_2.5 concentration,there were linear relationship between PM_2.5 and SO₂,NO₂ and wind,and non-linear relationship between PM_2.5 and CO,O₃,PRE and RHU.The GAM models,which considered the interaction of SO₂ respectively with CO,PRE and RHU,the interaction of CO respectively with NO₂,O₃,PRE,Wind and RHU,and the interaction of NO₂ respectively with Wind、PRE and RHU,all passed the significance test (P<0.01 or P<0.05).The interaction of SO₂,CO and NO₂ respectively with other factors such as meteorological factors had the most important influence on the change of PM_2.5 concentration.At last,through the visualized three-dimensional map of the GAM models considering the interaction of the influencing factors on the PM_2.5 concentration,the interactive effects of the influencing factors on PM_2.5 concentration were quantitatively modeled.Our results demonstrated that GAM could be used to quantitatively analyze the interactive effect of the influencing factors on the change of PM_2.5 concentration.Therefore,the research method is innovative and important for PM_2.5 pollution and control.