Comparison Of Observations On The Characteristics Of Ozone Deposition In Winter Wheat And Maize

In this study,the eddy covariance system was used in conjunction with the fast and slow O₃ concentration analyzer to study the winter wheat and corn in Zhengzhou,the core city of the Central Plains Economic Zone in China,and to conduct the continuous dynamic observation of the ozone dry deposition process under natural farmland conditions.The ozone deposition characteristics of the two crops were revealed,and the distribution rules of different deposition channels of the two crops were compared,and the different effects of precipitation on the ozone deposition of winter wheat and maize were analyzed.The results are as follows:1.Characteristics of ozone deposition:During the observation period of winter wheat and maize,the daily average values of O₃ concentration were 42.7 and 68.7 nL/L,respectively,which were mainly affected by solar radiation and humidity,and the diurnal variation was single-peak.The daily mean values of ozone flux were-0.0073 and-0.0131?mol/?m²?s?,respectively?the negative sign indicates the direction downward?,and the maximum values appeared at 13:00 in the afternoon,which was greatly affected by the concentration of O₃,and the diurnal variation was a single valey type.The daily mean values of ozone deposition velocity were 0.38 and 0.42 cm/s,respectively,which are affected by many factors such as atmospheric turbulence,vegetation growth characteristics and meteorological conditions,and the diurnal variation was a single peak type.The average daily resistance of atmospheric transmission were 104.9 and 86.8 s/m,which is mainly controlled by atmospheric turbulence,and the diurnal variation was concave.The average daily canopy resistance were 236.2 and246.4 s/m,both reached the lowest value at 9:30 am,and the diurnal variation was single-valley.2.The distribution law of deposition channel:the diurnal variation of the deposition channel of winter wheat and maize is basically the same.The stomatal conductance shows a single-peak change during the day,and returns to zero at night,the daily average value was0.13 and 0.18 cm/s,respectively,the maximum value appears at 12:30 noon.The diurnal variation of non-stomatal deposition velocity showed a state of high morning,low afternoon,and stable at night.The daily average values were 0.63 and 0.50 cm/s,respectively,and the maximum values appeared in the morning,which was the main contribution of the highest value of canopy conductance.The daily mean values of stomatal deposition flux were-0.0024 and-0.0062?mol/?m²?s?,respectively,and the daily average values of non-stomatal deposition flux were-0.0050 and-0.0070?mol/?m²?s?,respectively.The non-stomatal deposition flux accounted for 68%and 53%of the total ozone deposition flux,and the non-stomatal deposition channels was dominant.The stomatal deposition flux during the day reached 45%and 60%,respectively,indicating that the stomatal absorption channel is still an important component of plant canopy deposition flux,and maize was relatively more dependent on stomatal absorption.3.Characteristics affected by precipitation:The daily average values of O₃ background concentration of winter wheat and maize under precipitation conditions were 39.7 and 56.1nL/L,respectively,which were significantly smaler than the daily average values of 43.9 and74.3 nL/L without precipitation.For the winter wheat crop ecosystem,precipitation affects the O₃ deposition velocity by reducing atmospheric turbulent exchange during the day,increasing non-stomatal deposition of the canopy,and reducing the stomatal conductance of the canopy.For the maize crop ecosystem,precipitation increases O₃ deposition velocity by enhancing nighttime atmospheric turbulent exchange,promoting non-stomatal deposition of the canopy,and enhancing daytime canopy stomatal conductance.Therefore,under different background conditions,the effects of precipitation by different scholars on the dry deposition of ozone are not the same.