Project No: 16309326

Title: Modelling the Formation and Fate of Particulate Organic Nitrates from Anthropogenic and Biomass Burning Emissions

Principal Investigator: Prof. Qi YING

Co-Investigator: Dr. William P.L. CARTER

Abstract:

Organic nitrates (ONs) are key atmospheric compounds that link the cycles of volatile organic compounds (VOCs) and nitrogen oxides (NOₓ), exerting a complex influence on tropospheric ozone (O₃) and secondary organic aerosol (SOA) formation. While ON formation from biogenic VOCs is relatively well-studied, significant knowledge gaps remain regarding their sources, formation pathways, and fate in polluted regions influenced by anthropogenic emissions and open biomass burning. Current chemical transport models (CTMs) substantially underpredict observed particulate organic nitrate (pON) in these environments, hindering an accurate assessment of their impacts on air quality and health. This research addresses these gaps by investigating three interconnected questions: (1) What is the contribution of anthropogenic VOCs to observed gaseous and particulate ON in polluted urban atmospheres? (2) How much ON is formed during extensive Southeast Asian (SEA) biomass burning episodes? (3) To what extent do condensed-phase decay processes of pON feed back into gas-phase chemistry, affecting O₃, atmospheric oxidation capacity, and SOA? To address these questions, we propose a three-part research plan using the Community Multiscale Air Quality (CMAQ) model. In Task 1, we will incorporate two enhanced chemical mechanisms (SAPRC-22 and the Master Chemical Mechanism) to better represent ON formation from anthropogenic and biogenic VOCs. This will be coupled with advanced treatments of multiphase processes, including gas-particle partitioning and condensed-phase reactions (hydrolysis, aqueous OH oxidation, and photolysis). The model will be rigorously evaluated against field measurements from multiple East Asian campaigns. In Task 2, we will quantify the contribution of SEA open biomass burning to regional pON, assessing the sensitivity of predictions to VOC speciation profiles and plume-rise algorithms, and exploring non-linear interactions with urban anthropogenic emissions. In Task 3, targeted sensitivity simulations will isolate and quantify the feedback of pON condensed-phase decay on O₃ and SOA formation, critically examining uncertainties in reaction products and oxidant concentrations. This project will deliver a robust, evaluated modelling framework that can accurately simulate pON in polluted atmospheres, thereby addressing critical gaps in current models. By quantifying the relative contributions of anthropogenic and biomass burning sources, and by resolving key uncertainties in the multiphase fate of organic nitrates, the research will provide valuable mechanistic insights into the complete lifecycle of ONs. Ultimately, this will enable more accurate assessment of their impact on regional O₃ and particulate matter pollution, providing a scientific foundation for informed air quality management strategies.