Nocturnal formation and evolution of organic nitrates and their night-to-day transition in urban and rural areas

Organic nitrates (ONs), as an important reservoir of nitrogen oxides (NOx), play a crucial role for secondary organic aerosol (SOA) and tropospheric ozone (O3) production.

Our understanding of their life cycle is incomplete due to more limited laboratory studies on their nocturnal formation, evolution, and night-to-day transition, relative to their daytime chemistry.

The nocturnal variation of boundary layer (BL) structure leads to the separation into a lower stable BL (SBL) and an upper residual layer (RL), which are characterized by different temperature and humidity profiles, as well as the abundance of precursors for ONs. Despite this, vertical observations of ONs above ground level are quite limited.

This project will combine laboratory experiments, fieldwork, and modeling approaches to study ONs not only at the surface but also aloft.

Specifically, we will combine the ground-level measurements with an unmanned aerial vehicle (UAV)-based sampling platform to detect ONs in the SBL and RL for both urban and rural sites.

We will perform laboratory experiments to constrain physiochemical processes responsible for ONs’ formation and evolution observed in the real atmosphere. Finally, the obtained knowledge is used in models to better assess how ONs influence the regional NOx budget.

Closing this critical knowledge gap is of importance for accurately evaluating its roles for NOx recycling, O3 and SOA formation with scenarios including future climate change and climate policy.