Spatial heterogeneity analysis of PM2.5 concentrations in intra-urban microenvironments
HU Chen-xia1, ZOU Bin1, LI Shen-xin1, DUAN Xiao-li2, ZHOU Xiang3
1. School of Geosciences and Info-physics, Central South University, Changsha 410083, China; 2. School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China; 3. Hunan Land Resources Information Center, Changsha 410004, China
Abstract：Combing the observed hourly PM2.5 concentrations from 10 regular sites of national air quality monitoring network (sparse observation mode) and 203 ground portable air quality monitors (dense observation mode),we analyzed the micro-environmental distribution characteristic of PM2.5 concentrations from point and area perspectives in the downtown area of Changsha city.Results showed that,under dense observation mode,relatively high PM2.5 concentrations appeared in areas with intensive human and vehicles activities,such as road intersections,construction sites,residential districts,hospitals and industrial zones,while relatively low concentrations mainly happened in scenic regions with large vegetation coverage.More rarely differences of PM2.5 concentrations at same location did exist under dense and sparse observation modes.Meanwhile,inverse distance weighting based spatial interpolated map of PM2.5 concentrations from dense observation mode revealed that obviously heterogeneous characteristics of PM2.5 variations were marked with the highest values (>75μg/m3) in northwest part,moderate values (65~75μg/m3) in the central south part,and the lowest ones (<55μg/m3) in the east part of the study area.These characteristics were furtherly demonstrated by the significant spatial anisotropy from directional profile analysis.Inversely,the interpolated PM2.5 distribution map under sparse observation mode cannot reflect this inherent heterogeneity,with overall PM2.5 concentration lower than 55μg/m3.The PM2.5 concentrations at dense observation sites extracted from the sparsely interpolated distribution map were clearly lower than the real values,while the higher PM2.5 concentrations only appeared in the road intersections,construction sites and bus stations.Results suggest that the PM2.5 concentrations from the nationally regular sites established for protecting environmental was difficult to reflect the ground real PM2.5 values at the same locations.The microenvironments in intra-urban area with higher PM2.5 concentrations identified under sparse and dense observation modes are different.The greater concentration deviations of these microenvironments generally occurred with relatively good air quality.
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