Fig. 1.

China’s Huai River/Qinling Mountain Range winter heating policy line and PM₁₀ concentrations. Black dots indicate the DSP locations. Coloring corresponds to interpolated PM₁₀ levels at the 12 nearest monitoring stations, where green, yellow, and red indicate areas with relatively low, moderate, and high levels of PM₁₀, respectively. Areas left in white are not within an acceptable range of any station.