基于激光吸收光谱技术的农田氨挥发研究

doi:10.3964/j.issn.1000-0593(2020)03-0885-06

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Abstract Ammonia volatilization is an important path of nitrogen loss from farmland into the environment, and is also the main factor of PM_2.5 formation, which has serial disadvantageous effect on the ecological environment and agricultural production. Previously, most of the traditional methods for ammonia emission measurement collected atmospheric ammonia by an acid absorbent. However, these techniques were labor intensive, making it difficult to determine diurnal variation of ammonia volatilization. The open-path tunable diode laser absorption spectroscopy is a reliable tool with high precision, high selectivity, and fast response time for continuous and nonintrusive monitoring of ammonia concentrations over distances from tens to hundreds of meters under field conditions. Currently, the combination of tunable diode laser absorption spectroscopy and micrometeorological backward Lagrangian stochastic diffusion model (TDLAS-BLS) has become a popular technique in the measurement of ammonia volatilization in the field. The objectives of the study are first, to compare TDLAS-BLS technique with the micrometeorological integrated horizontal flux method for its accuracy and applicability for quantitatively measuring ammonia emission from large area of farmland through field experiments. Second, determine the dynamics of ammonia volatilization via high-temporal resolution data and identify the factors that govern ammonia volatilization from urea applied to winter wheat. The results indicated that the estimates made by TDLAS-BLS method were statistically equivalent to those made by the IHF method (regression gradient=0.97, R²=0.97, n=14). The ammonia emission rates and total ammonia loss estimated by the TDLAS-BLS technique were only 3% and 6% lower than those from the IHF method, respectively. This implied that TDLAS-BLS technique can be used to quantitatively estimate ammonia emission from large area of farmland during topdressing period of winter wheat with acceptable accuracy. Ammonia concentration was higher in daytime than in the night at topdressing stage of winter wheat, due to wind speed fluctuation causing it to fluctuate greatly. Ammonia volatilization rate increased slowly after fertilization, and reached a maximum value at the sixth day after fertilization and then decreased gradually after 15 days. This was mainly concentrated in the 5～8 days after fertilization, and accounted for 69% of the total during the overall monitoring period. During this period, the total loss determined by TDLAS-BLS method was 8.8 kg N·ha^-1 (6.3% of the total applied N). The lower loss was related due to furrow application of urea and low temperature. This demonstrated the ability of the TDLAS-BLS method to characterize the diurnal patterns of ammonia emission and the environmental influences on ammonia emission from cropland via high-temporal resolution data. Ammonia volatilization showed large diurnal variability during the daytime, which was coincident with temperature, wind speed and solar radiation. Wind speed, solar radiation, soil temperature and precipitation are significantly correlated with ammonia volatilization. Meteorological factor (such as precipitation) are the main factors influencing ammonia volatilization in abnormal weather.

Key words：Laser absorption spectroscopy; Backward Lagrangian stochastic diffusion model; Micrometeorological integrated horizontal flux method; Winter wheat; Ammonia volatilization; Influencing factors

Received: 2019-01-08 Accepted: 2019-04-16

ZTFLH:

O433.1

Corresponding Authors: ZHU An-ning E-mail: anzhu@issas.ac.cn

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)03-0885-06 OR https://www.gpxygpfx.com/EN/Y2020/V40/I03/885