Strong impacts of biomass burning, nitrogen fertilization, and fine particles on gas-phase hydrogen peroxide (H2O2)

Gas-phase hydrogen peroxide (H 2 O 2 ) plays an important role in atmospheric chemistry as an indicator of the atmospheric oxidizing capacity. It is also a vital oxidant of sulfur dioxide (SO 2 ) in the aqueous phase, resulting in the formation of acid precipitation and sulfate aerosol. However, sources of H 2 O 2 are not fully understood especially in polluted areas affected by human activities. In this study, we reported some high H 2 O 2 cases observed during one summer and two winter campaigns conducted at a polluted rural site in the North China Plain. Our results showed that agricultural fires led to high H 2 O 2 concentrations up to 9 ppb, indicating biomass burning events contributed substantially to primary H 2 O 2 emission. In addition, elevated H 2 O 2 and O 3 concentrations were measured after fertilization as a consequence of the enhanced atmospheric oxidizing capacity by soil HONO emission. Furthermore, H 2 O 2 exhibited unexpectedly high concentration under high NO x conditions in winter, which are closely related to multiphase reactions in particles involving organic chromophores. Our findings suggest that these special factors (biomass burning, fertilization, and ambient particles), which are not well considered in current models, are significant contributors to H 2 O 2 production, thereby affecting the regional atmospheric oxidizing capacity and the global sulfate aerosol formation. • Biomass burning events led to high H 2 O 2 concentrations up to 9 ppb observed. • H 2 O 2 and O 3 were greatly enhanced after fertilization events due to HONO emission by fertilized soil. • Particle-phase reactions involving organic chromophores contributed to H 2 O 2 production.