Deliquescence Relative Humidity and Reversible Non-deliquescent Water Uptake in the Sodium Salts of Succinic Acid

When metal ions from sea spray and other sources interact with dicarboxylic acids dissolved in atmospheric droplets, the results can be the precipitate of organic salts under dry atmospheric conditions. This study focused on the hygroscopic properties of the sodium salts of succinic acid (NaHC₄H₄O₄ and Na₂C₄H₄O₄). The salts reversibly take up water at relative humidities (RHs) lower than the deliquescence relative humidity (DRH) at 298 K. At higher RH values, a normal DRH is observed and temperature-dependent values were determined. The enhanced water content of otherwise dry particles may have an impact on heterogeneous chemistry on these particles as well as their optical properties.