Development of passive flux samplers based on adsorption to estimate greenhouse gas emissions from agricultural sources

Abstract

Passive flux samplers (PFSs) packed with adsorbents are used to estimate gaseous emissions. A key condition of their use is maintaining a linear relationship between internal and external air velocities. The performance of PFSs designs depends on the characteristics of the adsorption bed and on the sampler design. The parameters required to enable PFSs to estimate greenhouse (GHG) emissions from agricultural sources were studied. The effect of the particle size of the adsorbent used as collector medium was analyzed theoretically using the Ergun equation. Three orifice plates with 0.5, 0.7 and 1 mm bore diameter were evaluated in order to determine the most appropriate diameter to control air flow through a new passive flux sampler (PFS) prototype while maintaining adequate linearity between internal and external air velocity. The effect of the adsorbent bed thickness (19, 50, 100 and 200 mm) on the internal-external air velocity relationship in the PFS was evaluated. The best performance was obtained using the 0.7 mm orifice plate and an adsorbent bed thickness of 50 mm. Spherical adsorbents with high adsorption capacity are recommended in order to decrease the adsorbent bed thickness and improve sampling performance. A series of experiments showed that the estimated mass flow obtained by the developed PFS was close to the confidence interval of values obtained by direct detection. Thus, the developed PFS can be used as a tool for the estimating of GHG emissions from agricultural sources.

Evaluation of passive flux samplers with different orifice sizes to measure ammonia volatilization losses

“…During this study, the average wind speed was low at 1.4 m·s −1 and the maximum wind speed was always below 10 m·s −1 . Previous research has shown that at the same external wind speed, the pressure drop across an orifice plate decreases as the orifice diameter increases (Larios et al., 2018; Yin et al., 2021). Thus, at the same low wind speed in the field, a 1‐mm orifice would be expected to have greater turbulence than a 2‐mm orifice, which may have led to better contact with the tube wall, better NH 3 adsorption, and greater measurement of NH 3 volatilization loss.…”

“…One of the methods that can measure actual NH 3 loss under field conditions is the integrated horizontal flux (IHF) that uses anemometers and dynamic air samplers placed at different heights from the soil surface. This method requires expensive and complex equipment as well as the availability of electrical power in the field, which makes it difficult to have many treatment replications (Larios et al., 2018). The development of IHF methods with passive instead of dynamic flux samplers has reduced costs and made replications more feasible under field conditions (Leuning et al., 1985; Schjoerring et al., 1992).…”

“…The purpose of the orifice is to reduce air speed through the sampler and create turbulence to increase contact with the inside surfaces of the tubes so that NH 3 can be trapped by oxalic acid coating the surfaces (Schjoerring et al., 1992; Sommer et al., 1996). This turbulence created behind the orifice decreases as wind speed decreases and as orifice diameter increases (Ballil & Jolgam, 2022; Larios et al., 2018; Yin et al., 2021).…”

Preparation of Nafion Membranes for Reproducible Ammonia Quantification in Nitrogen Reduction Reaction Experiments

“…Since the atmospheric levels of ammonia can vary greatly between locations world‐wide, [19] the ammonium content in the membrane will highly depend on the location of the experiment. The atmospheric concentration of ammonia also highly depends upon temperature and season (fertilizer application) [20] . Measurements of aerosol NH 3 in Heimaey, an active volcano island south of Iceland, demonstrated 0.05–0.12 ppb NH 3 in air [21] .…”

Preparation of Nafion Membranes for Reproducible Ammonia Quantification in Nitrogen Reduction Reaction Experiments

“…The atmospheric concentration of ammonia also highly depends upon temperature and season (fertilizer application). [20] Measurements of aerosol NH 3 in Heimaey, an active volcano island south of Iceland, demonstrated 0.05-0.12 ppb NH 3 in air. [21] Atmospheric concentrations have been measured in various cities worldwide and reported between 3 ppb and 100 ppb (up to 800 times the reported concentration in Heimaey) depending on location and time.…”