Observation And Simulation Of Ozone Dry Deposition Flux In Summer Maize Field

Ozone is one of the main atmosphere pollutants in the surface layer,and its increasing concentration will cause great harm to the terrestrial ecosystem and food security.In this paper,eddy correlation system was used in the natural ecosystem to observe the ozone dry deposition flux in summer maize field from tasseling stage to mature stage.The characteristics of ozone dry deposition in summer maize field and the influence of environmental factors on it were discussed.The stomatal conductance was simulated by using SW model and PM formula.On this basis,the characteristics and influencing factors of stomatal and non-stomatal deposition were analyzed.The mean results are as follows:（1）During the observation period,ozone concentration,dry deposition flux,dry deposition velocity,and stomatal absorption flux all show obvious diurnal variation characteristics,and the mean values are:58.55 nL·L^-1,-10.95 nmol·m^-2·s^-1,0.41 cm·s^-1,and-4.58 nmol·m^-2·s^-1（negative sign indicates downward direction）.The daily variation of total ozone dry deposition flux and stomatal absorption flux is of"U"type,with drastic change during the day and slight and gentle change at night,reaching the maximum value around 13:30.And the dry deposition rate reaching the maximum value around 09:00.（2）Under different weather conditions,the ozone dry deposition flux and velocity show different trends.From 12:30 to 14:30 in the afternoon of sunny days,the ozone dry deposition flux will first decrease unusually and then gradually rise.The ozone dry deposition process showed obvious change characteristics in different period,and the stomatal and non-stomatal deposition flux and the deposition velocity decreased gradually with the development of the growth period.（3）The ozone dry deposition flux increases with the increase of temperature,friction rate,vapor pressure deficit,solar radiation and ozone concentration.The variation of daytime the ozone dry deposition flux is mainly affected by ozone concentration.When the temperature and solar radiation are high and the relative humidity is low,the concentration of O₃ is also high.The higher friction rate is beneficial to the increase of atmospheric turbulence and the deposition of O₃ in the canopy.When temperature,solar radiation,saturation vapor pressure deficit,and friction wind speed are too large,stomatal absorption will be restrained to some extent,while non-stomatal deposition will not be significantly affected,resulting in a reduced increase amplitude in the total deposition flux.When the relative humidity is too high or too low,it is not good for ozone stomatal absorption.The increase of relative humidity will promote the rate of non-stomatal deposition.（4）The stomatal conductance calculated by P-M formula combined with GPP was compared with that calculated by P-M formula combined with SW model,founded that:in heavy rainfall days,the latter will be unusually large,and in other cases,the latter will be slightly smaller than the former.There was a good correlation between them.This method is not suitable for simulating the stomatal conductance in heavy rainfall days,and it is better in sunny and cloudy days...