2019—2021年疫情前后唐山市大气污染物变化特征及成因分析
马东玲, 任永强, 陈星彤, 孔金哥

Analysis of the variations and causes of air pollutants in Tangshan City before and after the COVID-19 pandemic from 2019 to 2021
MA Dongling, REN Yongqiang, CHEN Xingtong, KONG Jinge
图5 重污染阶段风向玫瑰图
Fig.5 Rose chart of wind direction in heavy pollution stage