Processus de transfert atmosphérique de polluants dans les agrosystèmes

Abstract

Different pollutants, either gaseous or particulate, are emitted in the atmosphere from agricultural systems. The sources may be farm housings, field application and volatilisation from the soil or the plant. These emissions are a loss of nutrients for the agricultural systems but also a source of pollution for the atmosphere and for the neighbouring ecosystems or surface water after deposition. The different processes involved in pollutant emission, atmospheric transport and deposition are reviewed. Emission occurs in different conditions: direct injection of particulates or droplets from animal housing or during field application of fertilisers or pesticides, and gas production resulting from either physico-chemical equilibria or microbial metabolism. For both gaseous or parliculate compounds, deposition is strongly dependent on the surface characteristics (leaf area index, wetness, roughness, metabolism). The deposition is usually determined by estimating a deposition velocity which accounts for the effects of turbulence, canopy processes and the pollutant characteristics. Atmospheric diffusion and transport processes make a link between the source (emission) and the sink (deposition) of pollutants. They are both dependent on meteorological conditions and surface characteristics. Then estimating atmospheric deposition at regional scale requires a coupling between emission, transport and deposition models.