A method for developing ozone exposures that mimic ambient conditions in agricultural areas

Abstract

Ozone fumigations that mimic ambient ozone distributions facilitate the development of links between 1. (1) vegetative effects results that are generated in the laboratory and the field and 2. (2) predictive effects models that depend upon ambient air quality data. Experimental exposure profiles were constructed from a readily available ambient air quality data base (i.e. EPA SAROAD). Air quality data from selected monitoring sites were characterized over the 5-month growing season by identifying 1. (a) the number of occurrences of hourly ozone concentrations equal to or above 0.07 ppm, 2. (b) the number of days of each episode, 3. (c) the number of days between episodes and 4. (d) the rate of rise and decline of the daily ozone concentrations. An episodic profile was constructed incorporating the information into a representative 30-day ozone exposure pattern in which the concentration was changed on an hourly basis. In order to compare treatments having equivalent exposures (sum of hourly ozone concentrations equal to or above a minimum value) but dissimilar temporal distributions of hourly concentrations, a second profile was created. This profile was characterized by a repeated daily incremental rise and decline in ozone concentration that had the same hourly maximum concentration each day. The use of experimental exposure profiles mimicking ambient air quality characteristics and applied under controlled experimental conditions permits the examination of important exposure parameters on plant response.