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 β-pinene, O, NO, SO, and NH under dark conditions. Results showed that aerosol yield can be largely enhanced by more than 330% by NO or SO but slightly enhanced by NH by 39% when the ratio of inorganic gases to β-pinene ranged from 0 to 1.3. Joint effects of NO and SO and SO and NH existed as aerosol yields increased with NO but decreased with NH when SO was kept constant. Infrared spectra showed nitrogen-containing aerosol components derived from NO and NH and sulfur-containing species derived from SO. 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 NO and SO 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 β-pinene, O, NO, SO, and NH 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.