基于TDLAS-bLS方法的夏玉米农田氨挥发研究

Use of Open-Path TDL Technique and the Backward Lagrangian Stochastic Model to Monitor Ammonia Emission from Summer Maize Field

采用开放光程可调谐二极管激光吸收光谱技术和反向拉格朗日随机扩散模型,通过田间试验,开展基于高时间分辨率数据的农田氨挥发研究,旨在为揭示农田氨挥发的动态变化规律提供新技术新方法。结果表明,TDLAS-bLS法能有效监测农田氨挥发动态,尤其是日内变化规律。豫北平原潮土农田夏玉米追肥后日内氨挥发有两个挥发峰值,分别在9:00和14:00左右,第一个高峰是由于夜晚溶解在露水中的氨气随露水蒸发而再次挥发,第二个高峰受地温和光照影响所致。追肥后氨挥发速率迅速升高,但挥发高峰期持续时间较短,集中于前四天,整个监测期内氨挥发损失约25.3%。TDLAS-bLS法与通气法相比,测定结果有一定差异。

The backward Lagrangian stochastic dispersion model in conjunction with open-path tunable diode absorption spectroscopy was used to quantify ammonia emissions from farmland based on the high-temporal resolution data,aiming to provide innovative achievements to diagnose patterns of ammonia flux.The results indicate that the bLS dispersion technique using open-path lasers to measure atmospheric ammonia concentrations is suitable for determining ammonia emissions from farmland continuously,especially for characterizing diurnal characteristics of NH3 emissions.The ammonia emissions have a significant diurnal pattern with two emission peaks from urea applied to maize on a calcareous sandy loam fluvo-aquic soil in the North China Plain.We believe that the first peak starting at approximately 9：00 am is due to NH3 absorbed by the dew re-emission at night as the dew evaporates.The maximum of ammonia flux at 14：00 corresponds to the peak of soil temperature and solar radiation.The ammonia emission increased rapidly,but the duration of emission peaks lasted approximately 4 d.Cumulative NH3 emission was 25.3% of the applied N over the entire measurement period.The NH3 emissions measured with bLS dispersion technique and venting method had certain difference.