Figure 4.

(a) AMS normalized signal ratio of NH₃⁺ to SO₂⁺ as a function of mass concentration estimated from the measured dry number size distribution resulting from nebulizing the 2:1 NaCl/(NH₄)₂SO₄ solutions. The mass concentration is varied by changing the concentration of the nebulized solution, also shown in the top x-axis. (b) Modeled ratio between NH₄⁺ and SO₄^2– in the particle phase (E-AIM model) at various particle mass concentrations, modeled at an a_w of 0.30 (squares) and 0.5 (circles).