This study explores the neglected role of atmospheric deposition in δ¹⁵N_4a-3s (δ¹⁵N difference between NH₄⁺ and source NH₃), a key parameter in atmospheric NH₄⁺ source tracing. We develop an integrated model coupling these two processes and find that the difference in δ¹⁵N_4a-3s between the combined effect and the pure fractionation scenario increases with f (NH₄⁺/NH_x molar ratio). This work provides a new idea for precise NH₄⁺ source partitioning.

We studied how environmental factors influence the release of mercury from seawater to the atmosphere. We applied a novel approach in which prior knowledge about cause-and-effect is captured as graphical models and then used to estimate effect sizes. Results showed that sunlight affects mercury both directly and indirectly, with about 32 % of the effect explained by temperature increase. Thus, causal models can improve our understanding of pollution processes and the effect policies.

Aviation impacts climate by forming contrails that trap heat and can persist for hours at cruising altitudes. Forecasting these humid regions is difficult, as satellites lack accuracy, aircraft data are limited, and ERA5 reanalysis has random errors. This study presents a hybrid machine learning method that corrects ERA5 with aircraft data, using decision trees in dry air and neural networks in humid air. It improves relative humidity predictions, especially in the lower stratosphere.

Gas-phase chemical mechanisms are key components of air quality models used by regulatory agencies for air quality and public health planning. We use modeled ozone concentrations and Ozone Production Efficiency (OPE) to compare four chemical mechanisms and find that OPE is a viable comparison metric under atmospheric conditions where nitrogen oxides are limited. Using OPE to predict how ozone responds to emissions reductions, however, is an oversimplification that can overstate ozone reductions.

Both fire and urban emissions are major contributors to air pollution in Southeast Asia. Relative increases in measurements of methane and carbon monoxide gases during an aircraft campaign near the Philippines in 2019 were used to isolate pollution emissions from fires vs. urban sources. Results were compared to atmospheric transport models to determine the sources' regional origins, and relationships between pollution indicators relevant to poor air quality were investigated for each source.

Biomass burning is a significant source of greenhouse gases and airborne pollutants in Asia. Airborne measurements of greenhouse gas enhancement ratios, trace gases, and particle scattering were used to identify air masses impacted by biomass burning over several Asian countries during February and March of 2024. Further analysis using atmospheric transport models and satellite hotspot products was performed to understand the transport history of biomass burning impacted airmasses over Thailand.