Objective The article can provide reference for determining the concentration of cation NH_4~+ in the sample of air PM2.5 accurately,finding the factors that affecting analysis uncertainy and evaluating the area pollution situation and pollution source of haze formation through assessing the determination uncertainy.Methods According to the Monitoring Manual of Effects of Population Health by Air Pollution(published by 2015) and the JJF1059.1-2012 Evaluation and Expression of Uncertainy in Measurement,the a...