Abstract
The present study aimed to measure the air concentration and exchange flux of ozone (O3) in a paddy field for the single cropping of rice in central Japan from June 2010 to September 2011. A passive sampler method and a gradient method were used to determine the weekly means of the air concentration at two heights (6m and 2m above ground surface) and the exchange flux of O3, respectively. The present study also tested a solution to eliminate the overestimation by the filters to measure the O3 concentrations, which originated from the collection of nitric acid gas in the atmosphere. The solution was the combined use of two types of filters made of the same material ; one is the nitrite and alkaline impregnated filter and the other is the alkaline impregnated filter. The collection effect of nitric acid gas, i.e., the ratio of the nitrate that originated from nitric acid gas to the total nitrate, was on average 9.2% in the present study. The weekly mean O3 concentrations at the study site during the rice cultivation period were frequently higher than 40 ppb, which tended to be higher than those at the neighboring observatories for air quality. The estimated deposition velocities of O3 in the daytime and the nighttime in the cropping season were 0.94 and 0.40 cm s-1, respectively.
