This article introduces a research work recently published in Atmospheric Environment. In conjunction with China Agricultural University, the Institute of Atmospheric Physics, the Chinese Academy of Sciences (CAS), and the Institute of Subtropical Agriculture, CAS adopted the HT8700 open-path NH3 analyzer and eddy covariance (EC) technique. The research team conducted a high-frequency observation of NH3 land-atmosphere exchange flux in the North China agricultural area.

Fig. 1 A picture of the eddy covariance (EC) system during the measurement period

The experimental site is in Quzhou County, Hebei Province. The problem of NH3 emission and deposition in this area is particularly prominent. It is the first attempt to measure both NH3 volatilization and deposition fluxes in an agricultural ecosystem using the open-path instrument-based EC technique.

The team successfully obtained the NH3 volatilization flux data of typical corn-wheat rotation farmland during winter wheat sowing and fertilization. The estimated loss of nitrogen accounted for 0.57-0.71% of the nitrogen fertilizer application rate, which was far lower than similar observational studies. The estimation results, mainly attributable to optimized fertilization management practices, provide observational evidence for assessing the effectiveness of NH3 reduction pathways in agriculture.

With the excellent performance of the observation equipment in terms of measurement accuracy and frequency, the research team obtained a high temporal resolution (half-hour) NH3 dry deposition flux dataset in agricultural areas. The monitored average deposition rate was 14 g N ha-1 d-1. The observed diurnal variation of dry deposition is quite different from the natural ecosystem. In the future, using the HT8700 to carry out long-term observation of NH3 dry deposition flux will help to improve the understanding of the temporal and spatial variation of NH3 deposition.

Fig. 2 Temporal variability of the half-hourly ammonia (NH3) concentration and fluxes

Fig. 3 Mean diurnal variations of the observed ammonia (NH3) deposition fluxes

Reference

1. Wang K., Wang J., Qu Z., Xu W., Wang K., Zhang H., Shen J., Kang P., Zhen X., Wang Y., Zheng X., Liu X., 2022. A significant diurnal pattern of ammonia dry deposition to a cropland is detected by an open-path quantum cascade laser-based eddy covariance instrument. Atmospheric Environment 278, 119070. (https://doi.org/10.1016/j.atmosenv.2022.119070)

2. Wang K., Kang P., Lu Y., Zheng X., Liu M., Lin T., Butterbach-Bahl K., Wang Y., 2021. An open-path ammonia analyzer for eddy covariance flux measurement. Agricultural and Forest Meteorology 308–309: 108570. (https://doi.org/10.1016/j.agrformet.2021.108570)