Effects of foliage wetness on the dry deposition of ozone onto red maple and poplar leaves

The deposition of ozone onto hypostomatous red maple and amphistomatous hybrid poplar leaves was studied under controlled environments. Under similar environmental conditions, the ozone deposition was substantially greater onto poplar than onto maple leaves. Two kinds of surface wetness (simulating dew and raindrops) were artificially created on leaves to determine how deposition was affected. The ozone deposition onto wet maple leaves markedly increased almost immediately after water spraying. The increases were measured during both daytime and nighttime conditions. Nighttime measurements revealed that the enhanced ozone deposition onto wet maple leaves was largely controlled by the chemistry of the solution which eventually developed while leaves remained wet. Unlike maple leaves, small ozone deposition reductions were measured after poplar leaves became wet during daytime conditions. In addition, little ozone deposition was detected onto wet poplar leaves during the night, indicating that leaf water chemistry was less important for poplar than for maple leaves.