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

Abstract: 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'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.