Study On The Response Mechanism Of PM_2.5 To Land-use Changes In The Yangtze River Delta Region

PM_2.5 pollution has become the focus of the government and the public in recent years,and is also an urgent problem to be studied and solved.Land-use changes affect the concentration of atmospheric particulate matter directly or indirectly.It is important to understand the response mechanism of PM_2.5 to land-use changes to prevent and improve air pollution.Based on the remote sensing inversion PM_2.5 data from 1998 to 2015 and land use data,this paper uses the ensemble empirical mode decomposition,exploratory spatial data analysis,landscape pattern index method,correlation coefficient method and multiple stepwise regression method in the Yangtze River Delta core region to analyze the spatial-temporal characteristics of PM_2.5,the characteristics of land-use changes and the response mechanism of PM_2.5to land-use changes.The results are as follows:（1）The annual average value of PM_2.5 in the Yangtze River Delta region was 52.83μg/m3 from 1998 to 2015,and the annual fluctuation of the PM_2.5 was increasing.PM_2.5 concentration showed a non-linear upward trend by using the EEMD to analyze.Refer to the Environmental Air Quality Index Technical Regulations（Trial）divided by the air quality index level,the ratio of PM_2.5 to the annual limit of 1998 to 2015 is 1.2%～28%.The PM_2.5 pollution intensified.（2）The concentration of PM_2.5 in the Yangtze River Delta region was clustering,and the degree of agglomeration was getting higher and higher.That was,PM_2.5 pollution regional characteristics became more obvious.And the PM_2.5 pollution in Jiangsu Province was the largest and the most extensive,the overall degree of fluctuations of concentration in cities was in the larger,where the high value agglomeration area mainly concentrated,and showing a trend of expansion.Followed by Shanghai,Jiaxing,Huzhou and the main urban area of Hangzhou,the pollution was more serious,of which the largest fluctuation in Shanghai.PM_2.5 pollution was better in Zhejiang Province,especially in coastal cities,and the concentration change was small,where the low value mainly concentrated,and showing a stable trend.（3）From 2000 to 2010,the land-use structure in the Yangtze River Delta region was dominated by cultivated land,woodland and construction land.The obvious feature of its spatial pattern change was the rapid expansion of construction land,the sharp decrease of cultivated land area and the smaller changes of other land-use types.The whole landscape presented the pattern of a variety of patches of the distribution.（4）PM_2.5 had a significant positive correlation with the area of construction land,and the continuous development of construction land could significantly increase PM_2.5 concentration.And it was negatively correlated with woodland and grassland area,which indicated that they could reduce the concentration of PM_2.5 effectively,especially the complex shape of the large area of woodland and large density of grass could be more conducive to reduce.At the level of landscape,the average shape index was negatively correlated with the PM_2.5 concentration,indicating that the irregularity of the landscape patches reduced the PM_2.5 concentration to a certain extent.（5）Using the multiple stepwise regression method to fit the variables,with the land use type as the independent variable,the woodland area and the water area were into the equation,indicating that the woodland and the water were the two types of land-use that affected the PM_2.5 concentration.With landscape metrics as independent variables,the maximum plaque ratio of woodland and the edge density of water entered,with the larger the maximum patch area in the woodland,the smaller the edge density of the water body,the more conducive to reduce the PM_2.5 concentration.