艾比湖流域气溶胶光学厚度与土地覆被景观格局关联分析

Relationship between land cover-landscape spatial characteristics and aerosol optical depth in Ebinur Lake Watershed

土地覆被-景观格局直接或间接影响大气环境,了解大气环境对土地覆被-景观格局的响应,对维护和改善生态环境具有重要的意义。该研究基于环境一号卫星HJ-1B CCD数据,研究艾比湖流域土地覆被-景观格局与气溶胶光学厚度(aerosol optical depth,AOD)的关联关系,首先通过CCD数据反演AOD,然后利用分维数分析和贡献分析方法,定量分析土地覆被-景观格局对AOD的影响。结果表明:1)研究区AOD主要集中于绿洲及人口集聚区,从绿洲的中心到绿洲边缘气溶胶光学厚度逐渐降低,且在南部山区集聚呈带状;2)流域平均AOD与景观指数PD、ED、LSI和AI之间均存在着高度相关性,且景观的组成和空间结构都影响着流域AOD的空间分布;3)通过分维数分析,可知耕地和盐渍地的AOD密度从高值中心到外边界下降,但在其他的土地覆被类型上变化相反,盐渍地和耕地是流域主要空气污染的贡献者;4)应用贡献分析法进一步阐明了耕地和盐渍地可以增加空气污染,而林草地的效果相反。土地覆被变化和人类活动是影响艾比湖流域AOD空间分布主要原因,对AOD与土地覆被-景观格局变化的定量研究可以使研究者更好地了解AOD与土地覆被-景观格局的关系,进一步为土地政策的制定和土地利用规划提供参考。

The rapid development of economy in the Ebinur Lake Watershed has caused a swift transition of Land use/cover-landscapes pattern, which directly or indirectly affect the atmospheric environment. Atmospheric particulate is one of the major air pollutants in China. The aerosol optical depth （AOD） which represents the integrated column of aerosols is one of the most important indicators of air quality. Ebinur Lake Watershed in Xinjiang Province was chose as a sample study area of the relationships between land cover-landscapes pattern and aerosol optical depth （AOD）. Environmental mitigation satellite （HJ-1B CCD） data taken on September 30th, 2011 and September 30th, 2015 were used for AOD analysis to correlate with land use/cover types. Land cover in the study area was classified into seven categories by using the maximum likelihood supervised classification as cropland, forest-grassland （including natural forests and grasslands）, desert, lake bed, water, saline land, and other land cover （including the built-up area, mountains, etc.）. Nine landscape indices were used, which are largest patch index （LPI）, percentage of landscape （PLAND）, patch density（PD）, landscape shape index （LSI）, aggregation index（AI）, interspersion and juxtaposition index （IJI）, Shannon＆#39;s diversity index （SHDI）, contagion index （CONTAG）, and patch cohesion index （COHESION）. Combined with the uncertainty in the improved algorithm, and pixel by pixel data, aerosol optical thickness was calculated for September 30th, 2011 and September 30th, 2015. Fractal analysis and contribution analysis were applied to quantitatively illustrate the impact of land use/cover on AOD patterns. Watershed air pollution patterns could be related to the land cover-landscapes pattern changes. Using fractal analysis, the relationship between variations in the AOD and different land cover types could be further understood. The radius dimension was imported to analyze the variation over land use associated with AOD patterns. The impact of different land use/cover types on the AOD and their relationship to air pollution. The results showed that： 1） In the study area, AOD is mainly concentrated in the oasis and population concentration area, and the optical thickness of the aerosol is gradually decreased from the center to the edge of the oasis in the southern mountain area. 2） Significant correlation between mean AOD and the landscape indicators （PD, ED, LSI and AI）, the composition and spatial structure of the landscape affects the spatial distribution of AOD. 3） Fractal analysis showed that the density of cropland and salinity decreased from the center to the outer boundary so does the AOD. Cropland and saline land are major contributors to AOD in the watershed. 4） Fractal analysis showed that the AOD density declined from the center to the outer boundary so does saline land and cropland. Saline land and cropland area corresponding AOD density was significantly reduced from the center to the edge, saline land and cropland land of air pollution are main sources. The study enhance a better understand of the relationship between AOD and land use. The quantified effects of landscape structure variations on AOD patterns helped to better understand the effects of land use on AOD and they are important for policy making and land use planning.