The Syringe Pump Gas Distribution (SPGD) system: A simple and low-cost method for simulating NH3/15NH3 deposition

Chunze Wu Xing Wei ^* Chenghang Zhang Saima Khan

• School of Forestry, Northeast Forestry University, Harbin, China

Ammonia (NH 3 ) in the atmosphere plays a crucial role in the global nitrogen cycle. Elevated NH 3 deposition can result in various detrimental ecological and environmental consequences. Traditionally, researchers have employed methods such as static fumigation, dynamic fumigation using high-precision mass flow meters or standard gas cylinders, and free air enrichment to investigate vegetation responses to NH 3 deposition. However, these approaches may suffer from inaccuracies, high costs, or technical complexity. In order to address this issue, we developed the Syringe Pump Gas Distribution (SPGD) system, a cost-effective new method for simulating NH 3 / 15 NH 3 deposition. This system allows for precise and stable mixing of NH 3 / 15 NH 3 stored in a syringe with air using a microsyringe pump. The resulting mixture is then utilized to simulate NH 3 / 15 NH 3 deposition. With just one 20ml syringe, a single SPGD system can simulate NH 3 deposition flux ranging from 0 to 31.74 mg N m -2 d -1 (equivalent to 0 -116 kg N ha -1 yr -1 ) over an area of 0.36m 2 . The SPGD system demonstrated reliability and stability during a 21-day simulated deposition test on potted Populus cathayana under greenhouse conditions (including simulated rainfall). It exhibited adequate adjustment resolution to generate environments with varying NH 3 concentrations, corresponding to different NH 3 deposition fluxes. The test findings indicated a positive correlation between the δ 15 N levels in P. cathayana leaves and the NH 3 deposition flux increase. The cost, complexity, and risk associated with simulating NH 3 deposition can be significantly decreased by utilizing the SPGD system. The SPGD system is modular (gas supply unit and NH 3 supply unit) and can be adapted to different research needs, including for simulating the deposition of NO 2 , SO 2 or mixtures. Adopting this system, researchers can safely and efficiently simulate NH 3 deposition or perform 15 NH 3 labeling, thereby advancing the understanding of physiological and ecological processes associated with plants and even forest ecosystems under gaseous deposition.