Fig. 2: Chemical composition during a rapid growth event at +5 °C and 60% relative humidity.
From: Rapid growth of new atmospheric particles by nitric acid and ammonia condensation
This growth event is indicated in Fig. 1c with a black-outlined purple square. a, Gas-phase nitric acid (NO3), ammonia (NH3) and sulfuric acid (H2SO4) mixing ratios versus time in an event initiated by SO2 oxidation, with constant nitric acid and ammonia. b, Particle diameters and number distributions versus time, showing a clean chamber (to the left of the vertical dotted line), then nucleation after sulfuric acid formation and rapid growth once particles reach 2.3 nm. Black curves are linear fits to the 50% appearance times. c, Particle volume distributions from the same data, showing that 200-nm particles dominate the mass after 15 min. 1 μcc = 1 cm−6. d, FIGAERO thermogram from a 30-min filter sample after rapid growth (c.p.s., counts per second). The particle composition is dominated by nitrate with a core of sulfate, consistent with rapid growth by ammonium nitrate condensation on an ammonium sulfate (or bisulfate) core (note the different y-axis scales; the instrument is not sensitive to ammonia). A thermogram from just before the formation event shows no signal from either nitrate or sulfate, indicating that vapour adsorption did not interfere with the analysis.
