Anthropogenic-Biogenic Interactions at Night: Enhanced Formation of Secondary Aerosols and Particulate Nitrogen- and Sulfur-Containing Organics from β-Pinene Oxidation

Mixing of anthropogenic gaseous pollutants and biogenic volatile organic compounds impacts the formation of secondary aerosols, but still in an unclear manner. The present study explores secondary aerosol formation via the interactions between beta-pinene, O-3, NO2, SO2, and NH3 under dark conditions. Results showed that aerosol yield can be largely enhanced by more than 330% by NO(2 )or SO2 but slightly enhanced by NH(3 )by 39% when the ratio of inorganic gases to beta-pinene ranged from 0 to 1.3. Joint effects of NO2 and SO2 and SO2 and NH3 existed as aerosol yields increased with NO2 but decreased with NH3 when SO2 was kept constant. Infrared spectra showed nitrogen-containing aerosol components derived from NO2 and NH3 and sulfur-containing species derived from SO2. Several particulate organic nitrates (MW 215, 229, 231, 245), organosulfates (MW 250, 264, 280, 282, 284), and nitrooxy organosulfates (MW 295, 311, 325, 327, and 343) were identified using high-resolution orbitrap mass spectrometry in NO2 and SO2 experiments, and their formation mechanism is discussed. Most of these nitrogen- and sulfur-containing species have been reported in ambient particles. Our results suggest that the complex interactions among beta-pinene, O-3, NO2, SO2, and NH3 during the night might serve as a potential pathway for the formation of particulate nitrogen- and sulfur-containing organics, especially in polluted regions with both anthropogenic and biogenic influences.

Automated summary

This study found that under dark conditions, the aerosol yield can be significantly enhanced by nitrogen dioxide or sulfur dioxide within a certain ratio range of inorganic gases to biogenic volatile organic compounds, while ammonia showed a slight increase. The nitrogen- and sulfur-containing aerosol components were derived from nitrogen dioxide, ammonia, and sulfur dioxide, with organic nitrates and organosulfates identified in the experiments. These interactions among various compounds during the night could serve as a potential pathway for the formation of particulate nitrogen- and sulfur-containing organics in polluted regions with both anthropogenic and biogenic influences.