Zheng Yu-Rong, Wang Xu-Hong, Zhang Xiu, Hu Gui-Gui, Liang Xiu-Juan, Niu Lin-Zhi, Han Hai-Qing
College of Urban and Environmental Science, Northwest University, Xi'an 710127, China.
Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, Northwest University, Xi'an 710127, China.
Huan Jing Ke Xue. 2021 Jun 8;42(6):2699-2712. doi: 10.13227/j.hjkx.202010018.
Aerosol optical depth (AOD) is one of the most fundamental optical properties of aerosols that characterizes the attenuation of light by aerosols and is an indicator of regional air pollution. Based on the blue band surface reflectance database from the MOD09A1 products for the period 2000-2019 and the ASTER spectral database, AOD was estimated from Landsat TM/OLI data using the deep blue algorithm (DB). Multi-year average/annual average and seasonal AOD values for the period 2000-2019 were then calculated to analyze the spatial characteristics and temporal variations of AOD using the empirical orthogonal function method (EOF). Furthermore, the impacts of urbanization on the spatio-temporal distribution of AOD were analyzed. The obtained results are summarized as follows:① The multi-year average AOD spatial distribution in the hinterland of the Guanzhong Basin was significantly affected by topography and human activities, with higher AOD values and variationsin areas of low altitude and high-intensity human activities compared to the surrounding mountains. Thus, changes in AOD in the study area are mainly affected by anthropogenic factors. AOD also showed significant seasonal variations, whereby spring (0.34) > summer (0.33) > autumn (0.23) > winter (0.12), and the largest regional differences occurred in summer; ② The annual average AOD (from 2000-2019) showed the trend of "increase-decrease-increase", and reached a maximum in 2005, with the high AOD area gradually moving to the south. The distribution of AOD values in spring and summer was relatively discrete, while it is in a low-value agglomeration state in winter; ③ Three main AOD spatial distribution modes were identified based on the EOF, which had cumulative contribution rate of 83.0%. The spatial distribution trend of AOD showed regional consistency, with feature vectors consistent with the altitude, thus reflecting the difference of AOD at different altitudes. Taking the Qinling Mountains as the dividing line, the AOD presented the "north-south" pattern, AOD showed a "north-south" pattern, reflecting the uniqueness of the regional development in the Guanzhong Basin compared to the southern Qinling Mountains. The "southeast-northwest" distribution pattern indicated that the AOD presented a reverse change trend between urban and non-urban; and ④ The results of correlation analysis between the AOD and urbanization revealed a positive correlation with permanent population density (=0.707, <0.05), impervious surface density (=0.377, <0.05), and industrial POI density (=0.727, <0.5). These results are significant for improving the monitoring of air quality in the Guanzhong Basin and for the construction of an urban ecological environment.
气溶胶光学厚度（AOD）是气溶胶最基本的光学特性之一，它表征了气溶胶对光的衰减作用，是区域空气污染的一个指标。基于2000 - 2019年MOD09A1产品的蓝波段地表反射率数据库和ASTER光谱数据库，利用深蓝算法（DB）从Landsat TM/OLI数据中估算AOD。然后计算2000 - 2019年的多年平均/年平均和季节AOD值，采用经验正交函数方法（EOF）分析AOD的空间特征和时间变化。此外，还分析了城市化对AOD时空分布的影响。所得结果总结如下：①关中盆地腹地的多年平均AOD空间分布受地形和人类活动影响显著，与周边山区相比，低海拔和高强度人类活动区域的AOD值更高且变化更大。因此，研究区域内AOD的变化主要受人为因素影响。AOD也呈现出显著的季节变化，即春季（0.34）>夏季（0.33）>秋季（0.23）>冬季（0.12），且夏季区域差异最大；②年平均AOD（2000 - 2019年）呈“增加 - 减少 - 增加”趋势，2005年达到最大值，高AOD区域逐渐向南移动。春季和夏季AOD值的分布相对离散，而冬季处于低值集聚状态；③基于EOF识别出三种主要的AOD空间分布模式，其累积贡献率为83.0%。AOD的空间分布趋势呈现出区域一致性，特征向量与海拔高度一致，从而反映了不同海拔高度AOD的差异。以秦岭为分界线，AOD呈现“南北”格局，反映了关中盆地与秦岭以南地区区域发展的独特性。“东南 - 西北”分布格局表明AOD在城市和非城市区域呈现相反的变化趋势；④AOD与城市化之间的相关性分析结果显示，其与常住人口密度（=0.707，<0.05）、不透水表面密度（=0.377，<0.05）和工业POI密度（=0.727，<0.5）呈正相关。这些结果对于改善关中盆地空气质量监测和城市生态环境建设具有重要意义。
