Crop loss assessment for California: Modeling losses with different ozone standard scenarios

Crop yield losses were estimated for ambient O 3 concentrations and for a series of potential O 3 air quality standards for California, including the current statewide 1-h oxidant (O 3) standard of 0·10 ppm (196 μg m −3), 12-h growing season averages, and other models. A model for statewide losses was developed using hourly O 3 data for all sites in the State, county crop productivity data, and available O 3 concentration-yield loss equations to determine potential yield losses for each crop in each county in California for 1984. Losses were based on comparison to an estimated background filtered air concentration of 0·025 or 0·027 ppm, for 12 or 7 h, respectively. Potential losses due to ambient air in 1984 were estimated at 19% to 25% for dry beans, cotton, grapes, lemons, onions, and oranges. Losses of 5% to 9% were estimated for alfalfa and sweet corn. Losses of 4% or less were estimated for barley, field corn, lettuce, grain sorghum, rice, corn silage, spinach, strawberries, sugar beets, fresh tomatoes, processing tomatoes, and wheat. Implementation of either a modified rollback to meet the current 1 h California O 3 standard (0·10 ppm) or a three-month, 12-h growing season average of 0·045 ppm was necessary to produce large reductions in potential crop losses.