[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 SO ₂ ,CO,and NO ₂ were much higher.In the multiple influencing factors GAM models of PM _2.5 concentration,the contribution of the SO ₂ ,CO,NO ₂ ,O ₃ ,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 SO ₂ ,NO ₂ and wind,and non-linear relationship between PM _2.5 and CO,O ₃ ,PRE and RHU.The GAM models,which considered the interaction of SO ₂ respectively with CO,PRE and RHU,the interaction of CO respectively with NO ₂ ,O ₃ ,PRE,Wind and RHU,and the interaction of NO ₂ respectively with Wind、PRE and RHU,all passed the significance test ( P <0.01 or P <0.05).The interaction of SO ₂ ,CO and NO ₂ 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.