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 amphistomatou s hybrid poplar leaves was studied under controlled environments. Unde r similar environmental conditions, the ozone deposition was substanti ally greater onto poplar than onto maple leaves. Two kinds of surface wetness (simulating dew and raindrops) were artificially created on le aves to determine how deposition was affected. The ozone deposition on to wet maple leaves markedly increased almost immediately after water spraying. The increases were measured during both daytime and nighttim e conditions. Nighttime measurements revealed that the enhanced ozone deposition onto wet maple leaves was largely controlled by the chemist ry of the solution which eventually developed while leaves remained we t. Unlike maple leaves, small ozone deposition reductions were measure d after poplar leaves became wet during daytime conditions. In additio n, 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.