Real-Time Single-Particle Characteristics and Aging of Cooking Aerosols in Urban Beijing

Abstract

Cooking is an important source of organic aerosols in urban environments, while the physicochemical properties and aging of cooking aerosols in the atmosphere are still poorly understood. In this study, we investigated the single-particle characteristics and aging of cooking aerosols in Beijing during winter based on single-particle mass spectrometry measurements. The mixing state of cooking particles showed that molecular tracers (i.e., palmitic acid, linoleic acid, and oleic acid) mixed with inorganics (sulfate, nitrate, and ammonium) and carbonaceous species in the atmosphere, indicating that they had experienced aging. Cooking aerosols contributed more to particulate matter during clean periods than during polluted periods. The size distribution of cooking particles showed a bimodal pattern with a higher degree of aging of larger particles. In addition, we found high azelaic acid/oleic acid ratios in oleic acid-containing particles usually occurred under high O3 concentrations, and the ratio of azelaic acid to oleic acid peaked in the afternoon following the peak of the O3 concentration, indicating ozonolysis of oleic acid to form azelaic acid. Furthermore, oleic acid was found to age faster during clean periods with higher O3 concentrations. Our results can help in the assessment of the impact of cooking aerosols on air quality, human health, and climate.