关键词: 化学转化法, PM_2.5, 大气气溶胶, 铵态氮同位素比值

Abstract: Landscape fragmentation is one of the research hotspots in landscape ecology. The spatial distribution of landscape fragmentation can provide scientific basis for landscape pattern optimization. In this study, we analyzed the spatial correlation of landscape fragmentation of Bailongjiang Watershed in Gansu in 2014 using landscape pattern index, grid analysis, and spatial autocorrelation methods based on GeoDA and ArcGIS. The results showed that the Moran’s Ivalues of the landscape pattern indices, i.e. edge density (ED), contagion index (CONTAG), and Shannon’s diversity index (SHDI) under different grid sizes ranged from 0.478-0.501, 0.276-0.374, 0.406-0.436, respectively, indicating a stronger spatial positive correlation and a landscape fragmentation with the agglomeration. Taking 10 km×10 km as the characteristic scale to examine the spatial agglomeration effect of landscape fragmentation, we found that the areas with higher landscape fragmentation degrees were mainly distributed in the middle of Wudu District, and that the areas with lower landscape fragmentation degrees were located in southern Wenxian. Moreover, the Moran’s I value of human activity intensity with ED was 0.170, and the Moran’s I value of human activity intensity with SHDI was 0.180, with positive spatial correlation. However, the Moran’s I value of human activity intensity with CONTAG was -0.095, with negative spatial correlation, highlighting the role of human activity intensity in driving the spatialdistribution characteristics of landscape fragmentation. Our results suggest that GeoDA can be applied to landscape ecological spatial analysis.

Key words: chemical method, atmospheric aerosol., ammonium nitrogen isotope ratio, PM_2.5