| PM2.5 | fine particulate matter |
| NOx | nitrogen oxides |
| VOCs | volatile organic compounds |
| SO2 | sulfur dioxide |
| NH3 | ammonia |
| UYR | the upper zone of the Yellow River |
| MUPR | the middle and upper zone of the Pearl River |
| MYR | the middle zone of the Yellow River |
| NC | the northern coastal zone |
| NE | the northeast zone |
| MUYR | the middle and upper zone of the Yangtze River |
| SC | the southeast coastal zone |
| XJ | the Xinjiang zone |
| QTP | the Qinghai-Tibetan Plateau |
| EC | the eastern coastal area |
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