A semi-empirical approach to model net particulate matter fluxes between vegetated surfaces and the atmosphere

• Modeling of bi-directional PM fluxes over a grassland. • Surface concentrations are an additional parameter. • The flux depends on the vertical concentration gradient. • Surface concentrations are related to water vapor condensation. • Aitken mode modeled fluxes lack precision compared to observations. Particulate matter (PM) is a major atmospheric pollutant and public health concern. Atmospheric levels of PM can be reduced by decreased emissions or their removal through deposition. Dry deposition models already exist but do not reproduce the net emission fluxes observed in situ . This study aims to address this issue by developing a semi-empirical approach to model PM bidirectional exchanges between the atmosphere and vegetated surfaces based on existing resistive schemes, with the addition of a non-zero PM surface concentration, which allows for including emission in the net flux computation. Three PM flux datasets above a grassland in Lusignan (France) are used, one to calibrate and two to validate the model. The surface concentrations represent aerosol dynamics phenomena such as coagulation, nucleation, or condensation. Good agreement is found between the modeled and measured fluxes, with a robust linear model of modeled versus measured fluxes yielding a 90% slope.