Sulfuric acid nucleation: An experimental study of the effect of seven bases

TLDR

The study compares measured sulfuric acid–base nucleation rates with predictions and prior experiments, extrapolating them to atmospheric conditions. Nucleation of sulfuric acid, water, and nitrogenous bases was investigated in a flow reactor by controlling acid and water flows, determining base concentrations from permeation rates, and measuring particle distributions with a nano‑differential‑mobility analyzer. The experiments show that amines enhance sulfuric acid nucleation more than ammonia alone, with dimethylamine and trimethylamine being the most effective, triethylamine weaker than methylamine, and urea/acetamide negligible; moreover, ammonia and amine together synergistically boost nucleation, implying significant atmospheric impacts.

Abstract

Abstract Nucleation of particles with sulfuric acid, water, and nitrogeneous bases was studied in a flow reactor. Sulfuric acid and water levels were set by flows over sulfuric acid and water reservoirs, respectively, and the base concentrations were determined from measured permeation rates and flow dilution ratios. Particle number distributions were measured with a nano‐differential‐mobility‐analyzer system. Results indicate that the nucleation capability of NH 3 , methylamine, dimethylamine, and trimethylamine with sulfuric acid increases from NH 3 as the weakest, methylamine next, and dimethylamine and trimethylamine the strongest. Three other bases were studied, and experiments with triethylamine showed that it is less effective than methylamine, and experiments with urea and acetamide showed that their capabilities are much lower than the amines with acetamide having basically no effect. When both NH 3 and an amine were present, nucleation was more strongly enhanced than with just the amine present. Comparisons of nucleation rates to predictions and previous experimental work are discussed, and the sulfuric acid‐base nucleation rates measured here are extrapolated to atmospheric conditions. The measurements suggest that atmospheric nucleation rates are significantly affected by synergistic interactions between ammonia and amines.