Plants and Atmospheric Aerosols

Atmospheric aerosols are liquid, solid, or mixed suspensions of heterogeneous chemical composition, ranging from a few nanometers to almost 100 μm in diameter. Plants are sources and sinks of these diverse aerosols. Vegetation is influenced by aerosols through the water cycle, radiation balance, and nutrient transport, on global and regional scales, but direct interactions of aerosols with plant ecophysiology have not been considered in sufficient detail. Plant surface characteristics and aerodynamic factors control deposition. These factors may be manipulated in efforts to mitigate aerosol concentrations using urban vegetation as efficient aerosol collectors. Hygroscopic aerosols deposited on leaves generate concentrated solutions that reduce surface tension and generate thin liquid films. These films are shown to enter the stomatal pores, facilitating foliar nutrient uptake and enhancing liquid water loss that is poorly controlled by stomata. Aerosol pollution can reduce plant drought tolerance and alter nutrient balance. Anthropogenic aerosols now exceed natural aerosols, particularly in urban areas. The effects of these aerosols on plants require a focused research effort.