[Ozone Deposition and Risk Assessment for a Winter Wheat Field:Partitioning Between Stomatal and Non-stomatal...

To better understand the ozone deposition and risk assessment over agroecosystems based on the ozone flux indices, an eddy-covariance system was used for measuring the ozone deposition continuously and dynamically in a winter wheat field. We analyzed the variations in ozone concentration, total ozone flux, and stomatal and non-stomatal flux. The relationships between stomatal/non-stomatal ozone deposition velocity and the main meteorological factors were investigated. Finally, the yield losses of winter wheat based on the ozone-dose index (AOT40) and ozone flux index (DF_s06) were calculated. Results showed that average daily ozone concentration (c_O) was 32.9 nL·L^-1. The daytime (08:00-18:00) and nighttime total ozone flux (F_O) were -7.6 nmol·(m²·s)^-1 and -3.1 nmol·(m²·s)^-1, respectively, and the mean diurnal F_O was -5.1 nmol·(m²·s)^-1. The mean daily stomatal ozone flux (F_s) and non-stomatal ozone flux (F_ns) ranged from 0 to -5.1 nmol·(m²·s)^-1 and from -1.43 to -10.31 nmol·(m²·s)^-1, respectively. The mean diurnal F_s and F_ns were -1.43 nmol·(m²·s)^-1 and -3.66 nmol·(m²·s)^-1. High solar radiation (SR), high temperature (T), and moderate humidity were used to analyze stomatal ozone deposition; high SR, moderate T, and high humidity were suitable to analyze non-stomatal ozone deposition. The cumulative total ozone flux (DF_O), cumulative stomatal ozone flux (DF_s), and cumulative non-stomatal ozone flux (DF_ns) were 31.58, 9.99, and 21.59 mmol·m^-2 during the entire experimental period, and DF_s and DF_ns accounted for 32% and 68% of DF_O. The ranges of yield loss in winter wheat were estimated at 11.58%-20.37% and 20%-23.56% using different assessment models based on the ozone dose index AOT40 and ozone flux index DF_s06, respectively.