| A large number of studies have proved that urban green land can effectively reduce air pollutants, but in the case of urban land is not enough, relying on increasing the green area to improve urban air quality is often difficult to achieve, so through the urban green landscape optimization to improve urban air quality has important practical significance.Based on the simulation of the concentration distribution of NO2 and PM2.5 in Wuhan city(December 2016 - February 2017), based on the principal component analysis (PCA), the index of green land fragmentation degree, green land landscape dominance, green land patch shape complexity and green land patch discrepancy degree in Wuhan were screened.And the correlation between the greenland landscape pattern index and the concentration of air pollutants was studied by using bivariate correlation analysis and RDA binding sequencing analysis in order to provide the basis for the optimization of urban green space.The main results are as follows:(1) The distribution of NO2 concentration in winter in Wuhan showed a ring decreasing trend from city to suburb. NO2 light pollution area is mainly distributed in the south of Jiangan District, east of Qiaokou District, Jianghan District and Qingshan District.NO2 good area is mainly distributed in the road-intensive area in the surrounding area and suburb, and NO2 excellent area is mainly distributed in the suburb away from urban area and air pollution sources, there is no moderate pollution aera, severe pollution area and serious pollution area of NO2. In general, Wuhan City, 2016 - 2017 winter NO2 pollution situation is lighter.(2) The distribution of PM2.5 concentration in winter in Wuhan showed a ring decreasing trend as the center of air pollution sources. PM2.5 severe pollution area is mainly distributed in Qingshan District. PM2.5 moderate pollution aera is located in the air pollution sources and their adjacent area and road-intensive area. PM2.s light pollution area is located in the suburb away from the air pollution sources and road-intensive area.NO2 good area is only very few area, located in the southwest of Caidian District.There is no excellent area and serious aera pollution area of PM2.5.In general, Wuhan City,2016-2017 winter PM2.5 pollution situation is serious.(3) The results of Wuhan greenland landscape pattern selection shows that, average patch area index(AREA_MN) and patch density index (PD) are used to describe the landscape fragmentation of green land. The maximum patch index (LPI) is used to describe the landscape dominance of green land. Landscape shape index(LSI) is used to describe the patch shape index of green land, and patch dispersion of the green land is described by the distribution and parallel index (IJI).(4) From the landscape fragmentation of green land point of view,under different landscape area, the average patch area index (AREA_MN) is not correlated with the concentration of NO2 and PM2.5, and the patch density index (PD) of the green land is negatively correlated with the concentration of NO2 and PM2.5, and the correlation size increased with the increase of the total area.There is a significant positive correlation between AREA_MN and NO2 and PM2.5 concentrations when the green area ratio is 0-35%. When the green area ratio is 0-40%, PD was negatively correlated with NO2 and PM2.5 concentrations, and the correlation size increased with the increase of green area,while green area ratio is more than 40% ,there is not relevant. It can be seen that the higher the landscape fragmentation of green land is, the lower the concentration of NO2 and PM2.5 is, when the green area is relatively small (<35%).The concentration of NO2 and PM2.5 was not correlated with the degree of green fragmentation,when green area ratio is more than 40%.(5) From the landscape dominance of green land point of view,under different landscape areas,there was a significant negative correlation between the maximum patch index (LPI) and the concentration of NO2 and PM2.5, and the correlation size becomes smaller as the total area of the landscape becomes larger. There was a significant positive correlation between LPI and PM2.5 concentration when the green area ratio is 0-35%, and there was a significant positive correlation with NO2 concentration when green area ratio is 0-15%. In general, the lower the dominance of green patches is, the lower the concentration of NO2 and PM2.5 is.(6) From the patch shape index of green land point of view, under different landscape areas,the correlation between landscape shape index (LSI) and NO2 and PM2.5 concentration is not significant. When the green area ratio is 0-40%, the LSI was negatively correlated with the concentration of NO2 and PM2.5, and the correlation size increased with the increase of green area ratio.In general, when the green area ratio is less than 40%, the more complex the green patches is, the lower the concentration of NO2 and PM2.5 is. When the green area ratio is more than 40%, the complexity of the patch shape of the green land is not related to the concentration of NO2 and PM2.5, the more complex the patch shape is conducive to the reduction of NO2 and PM2.5 pollutants.(7) From the patch dispersion of the green patches point of view,under different landscape areas,distribution and parallel index (IJI) has a significant positive correlation with NO2 and PM2.5 concentrations, and the correlation size increased with the increase of the total area of the landscape. When the green area ratio is 0-60%,IJI and NO2 and PM2.5 concentrations showed a significant positive correlation,and the correlation size increases with the green area ratio shows the trend of first increase and then reduce. When the green area ratio is 60%-100%,there is no correlation. Therefore, when the proportion of green area is less than 60%, the smaller the degree of dispersion between green patches, the lower the concentration of NO2 and PM2.5, and the distribution of concentrated patches in urban green space is conducive to the reduction of air pollutants. |
PDF Full Text Request