Pyruvic acid, an efficient catalyst in SO<sub>3</sub> hydrolysis and effective clustering agent in sulfuric-acid-based new particle formation

Abstract. The role of pyruvic acid (PA), one the most abundant α-keto carboxylic acids in atmosphere, was investigated both SO3 hydrolysis reaction to form sulfuric (SA) and SA-based aerosol particle formation using quantum chemical calculations a cluster dynamics model. We found that PA-catalyzed is thermodynamically driven transformation process, proceeding with negative Gibbs free-energy barrier, ca. −1 kcal mol−1 at 298 K, ∼ 6.50 lower than water-catalyzed hydrolysis. Results indicated can potentially compete SA production, especially dry polluted areas, where it be 2 orders magnitude more efficient reaction. Given effective stabilization product as SA⚫PA cluster, we proceeded examine PA clustering efficiency sulfuric-acid–pyruvic-acid–ammonia (SA-PA-NH3) system. Our thermodynamic data used Atmospheric Cluster Dynamics Code under relevant tropospheric temperatures concentrations (106 molec.cm-3), (1010 molec.cm-3) NH3 (1011 5 × 1011 PA-enhanced involves clusters containing molecule. Namely, these monomer 238 (SA)2⚫PA⚫(NH3)2 contribute by 100 % net flux formation. At higher (258 278 K), however, dominated pure SA-NH3 clusters, while would rather evaporate from high not enhancing effect examined evaluating ratio ternary SA-PA-NH3 rate binary rate. results show enhancement factor almost insensitive concentrations, 4.7 102 K [NH3] = 1.3 molec.cm-3. This indicates may actively participate formation, only cold regions troposphere highly NH3-polluted environments. inclusion this mechanism models reduce uncertainties prevail modeling impact on climate.