The role of Base molecules in AErosol formation

Introduction

Aerosol formation and growth mechanisms need to be better understood to improve air quality and weather prediction models, and reduce uncertainty of radiative forcing in climate change projections. Globally, half of the aerosol population is formed via gas-to-particle conversion and the fraction exceeds 90% in high latitudes.

Formation Mechanisms

In many locations, the initial molecular cluster forms from sulphuric acid and ammonia or dimethylamine. Growth to an aerosol particle is often explained by the condensation of:

• Sulphuric acid
• Methanesulfonic acid
• Highly oxygenated organic compounds

While the roles of strong acids and organic compounds and their oxidation channels are quantified in laboratory and field studies, cation detection and neutral atmospheric base measurements are notably under-represented. An important innovation of this project will be the direct measurement of cations and neutral base molecules and clusters based on mass spectrometry.

Role of Ammonia

Ammonia, a base predominantly emitted by agriculture, is a key air pollutant in the formation of fine particulate matter (PM2.5). In western Europe, up to half of PM2.5 is attributed to ammonia pollution because of its ability to form aerosols in reactions with common atmospheric acids.

Current Limitations

Current atmospheric models do not include amines, which can form aerosol particles at a 1000-times faster rate than ammonia. To uncover the composition and level of toxicity of PM2.5, as well as the scattering and absorption of sunlight by aerosol particles, it is critical to understand the atmospheric chemistry and molecular pathways that control their formation and growth.

Project Focus

The project will focus on the role of base molecules in the formation of new particles and their fate in the atmosphere. It is led by an established PI with a demonstrated history in groundbreaking nanoaerosol and precursor studies.

Impact on Modelling

This project will underpin the modelling of atmospheric aerosol processes, which are subject to major precursor emission changes in Europe and beyond.