Figure 4
From: Assessment of regional air quality by a concentration-dependent Pollution Permeation Index
Comparison between AQI and PPI.
(a) Jing-Jin-Ji (Beijing-Tianjin-Hebei), (b) Yangtze River Delta (YRD), (c) Pearl River Delta (PRD), and (d) Cheng-Yu (Chengdu-Chongqing). These two different indicators have similar tendencies, but the advantage of PPI is that it is capable of distinguishing an air pollution donor from an air pollution receptor. Moreover, a higher AQI does not necessarily imply an air pollution donor and vice versa.
