IMPACTS OF OZONE CONCENTRATION AND EXPOSURE TIME CHANGES ON RICE YIELDS^*

The impacts of O3 concentration change on rice yields for different lengths of exposure time are studied by means of the OTC-1 open-top chamber.The resuhs indicate that when O3 concentration increased from 50 ppb to 200 ppb during the time period of 20 to 80 days in the experiment,the rice yield was reduced by 6.78% to 33.72%.Two main influencing factors for rice yields are the increased O3 concentration and the extended exposure time.Using a logarithm function to simulate the impacts of O3 concentration on rice yields is better than using a the Weibull function.