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近地面高浓度臭氧(O3)对植物生长发育和光合作用等都有副作用.基于O3通量(特别是植物气孔吸收)的评价指标被认为比基于O3浓度的指标能更好地反应O3对生态系统的影响.本文报道了利用涡度相关技术进行农田生态系统(玉米地)O3通量的观测结果,初步分析了该地区夏玉米地上O3浓度、沉积速度(Vd)和臭氧通量(Fo)的日变化规律及其与生态环境条件的关系.结果表明:(1)观测期间(2011年8月9日至9月28日),30 min平均O3浓度存在明显的日变化规律,其最低值(16.5 nL L-1)和最高值(60.1 nL L-1)的出现时间分别为6:30和16:00左右.白天(6:00～18:00)和夜间(18:00～6:00,下同)的O3浓度分别为(39.8±23.1)和(20.7±14.1)nL L-1(平均值±标准差),瞬时O3浓度最大值为97.5 nL L-1.O3浓度受太阳辐射和温度影响比较明显.(2)无论白天还是夜间,近地层O3都是向下运动的.Vd日变化规律表现为夜间小而平稳、上午快速上升、中午前后大而平稳以及下午快速下降的过程.白天和夜间的Vd平均值分别为0.29和0.09 cm s-1,最大值为0.81 cm s-1.白天Vd的大小受作物生长期的影响,而Vd的日变化受太阳辐射和相对湿度的影响最为明显.(3)O3通量的日变化受O3浓度和Vd的共同影响,白天和夜间的平均O3通量(Fo)分别为-317.7和-70.2 ng m-2 s-1.Fo与CO2通量(Fc)和潜热通量(LE)的相关关系比较显著,通过比较白天和晚上Vd的差别,可以判断白天的气孔吸收是玉米地上大气O3主要的汇.
High concentrations of ozone near the ground (O3) have side effects on plant growth and photosynthesis, etc. The evaluation index based on the flux of O3 (especially the stomatal absorption of the plant) is considered to be better than the index based on the O3 concentration to better reflect the eco- System.This paper reports the observation results of the O3 flux of farmland ecosystem (maize field) by using the eddy covariance technique, and analyzes the O3 concentration, deposition rate (Vd) and ozone flux (Fo) (1) During the observation period (August 9, 2011 to September 28, 2011), there was a clear diurnal variation trend of average daily O3 concentration at 30 min, with the lowest value (16.5 nL L-1) and highest value (60.1 nL L-1) occurred at 6:30 and 16:00, respectively. Daytime (6:00 to 18:00) and nighttime (18:00 to 6:00) 00, the same below) were (39.8 ± 23.1) and (20.7 ± 14.1) nL L-1 (mean ± standard deviation) respectively, and the maximum instantaneous O3 concentration was 97.5 nL L-1.O3 concentration was affected by solar radiation And temperature are more obvious. (2) The O3 in the near-surface layer moves downward during the daytime and the nighttime, and the daily variation of Vd is small and stable at night and fast in the morning , Large and stable at noon and rapid decline in the afternoon.The average values of Vd at day and night were 0.29 and 0.09 cm s-1, respectively, and the maximum was 0.81 cm s-1. The size of daytime Vd was affected by crop growth period, While the diurnal variation of Vd was most affected by solar radiation and relative humidity. (3) The diurnal variation of O3 flux was influenced by O3 concentration and Vd, and the average O3 flux (Fo) at daytime and at night was -317.7 and -70.2 ng m-2 s-1 .Fo has a significant correlation with CO2 flux and latent heat flux (LE). By comparing the difference of Vd between day and night, it can be judged that the stomata absorption during the day is the corn atmosphere O3 main sink.