云南省植被覆盖对PM2.5时空分布的影响

Effects of Vegetation Cover on Temporal and Spatial Distribution of PM2.5 in Yunnan Province

以2001—2020年云南省的归一化植被指数(Normalized Differential Vegetation Index,NDVI)和县级PM_(2.5)栅格数据为研究对象,采用Sen趋势分析法与Mann-Kendall显著性检验,分析云南省PM_(2.5)浓度与NDVI的时空分布特征,利用Pearson相关系数分析云南省PM_(2.5)污染与植被覆盖的相关性。结果表明:(1)近20年植被覆盖在整体上呈上升趋势,面积为338190.56 km^(2),占比达85.81%。(2)近20年的PM_(2.5)污染在整体上呈下降趋势,面积为348480.88 km^(2),占比达88.42%。在NDVI低值区的PM_(2.5)污染较轻,较严重污染主要集中在NDVI的高值区。(3)在2001—2014年间,NDVI总体较低而PM_(2.5)浓度总体较高;2014—2020年植被覆盖面积快速上升,而PM_(2.5)污染在不断减少。(4)植被覆盖与PM_(2.5)污染整体表现为负相关,局部呈不相关,极少区域呈正相关,其中负相关面积为242854.38 km^(2),占比达61.62%。

The normalized differential vegetation index(NDVI)and PM_(2.5) raster data of counties in Yunnan Province from 2001 to 2020 were taken as the research object.The Sen trend analysis method and Mann-Kendall significance test were used to analyze the spatio-temporal distribution characteristics of PM_(2.5) concentration and NDVI in Yunnan Province.The correlation between PM_(2.5) pollution and vegetation coverage in Yunnan Province was analyzed by Pearson correlation coefficient.The results show that:(1)The vegetation coverage in the whole province has shown an upward trend in the past 20 years,and the area is 338190.56 km^(2),accounting for 85.81%.(2)In the past 20 years,the overall PM_(2.5) pollution in Yunnan Province has been in a downward trend,accounting for 88.42%,covering an area of 348480.88 km^(2).In the low-value area of NDVI,the PM_(2.5) pollution is relatively light,and the serious pollution is mainly concentrated in the high-value area.(3)From 2001 to 2014,the NDVI was generally low,and the PM_(2.5) concentration was generally high.From 2014 to 2020,the vegetation coverage increases rapidly,while PM_(2.5) pollution is decreasing.(4)The whole province’s vegetation coverage and PM_(2.5) pollution are negatively correlated,partially irrelevant,and positively correlated in very few areas,of which the negative correlation accounts for as high as 61.62%,covering an area of 242854.38 km^(2).