Ammonia emission reduction is increasingly being considered one of the control measures to mitigate wintertime fine particulate matter (PM2.5) pollution. Three wintertime observations from 2012 to 2018 in Wuhan, China, were analyzed to examine the effectiveness of ammonia control in wintertime PM2.5 reduction based on the critical total ammonia concentration (CTAC, i.e., the inflection point of effective ammonia control for PM2.5 mass reduction based on the asymmetric response of PM2.5 to ammonia control). The CTAC gradually approached 0% (imme...
