Fig. 7
From: Microscale pH variations during drying of soils and desert biocrusts affect HONO and NH3 emissions
Model prediction and observation of nitrous acid emission. Nitrous acid (HONO) gaseous emissions during biocrust drying as a function of soil hydration conditions (expressed in percent of water-holding capacity). Typical simulations of different conditions in drying patterns, and atmospheric ammonia (NH3) levels (low: 5 ppb, high: 20 ppb) are denoted as slow/high drying with low-/high-NH3 level, S–L (green), S–H (blue), F–L (orange), and F–H (red), respectively. The length of each box indicates ±1 standard deviation and each stick ranges the minimum and maximum emission of HONO from all simulations (n = 8). Colour gradients indicate the averaged spatial variability of local pH values (given as ±1 standard deviation) across simulations. a Simulated HONO emission with fast drying under high NH3 input was comparable with measurements from cyanobacteria-dominated crust in South Africa34. b Simulated HONO emission with slow drying under low NH3 input was comparable with measurements from light crust in Cyprus19
