Selection of the best sorbent material to capture ammonia emissions using passive flux samplers

The agricultural sector is the most significant contributor to global ammonia (NH₃) emissions, affecting ecosystems and human health. In this context, passive flux samplers (PFS) have emerged as a cost-effective and practical alternative for monitoring air emissions. The PFS comprises a tubular body with inlet and outlet openings and a sorbent medium that passively collects the target pollutant. This study aims to identify the most efficient acid-coated sorbent among glass microfiber filters, solid glass beads, zeolite, and biochar for the determination of NH₃ emissions employing PFS. A comprehensive comparative analysis between the four acid-coated sorbents was conducted, involving aerodynamic analysis, sorption kinetics, variability, and precision of the data. Additionally, a weighted performance index was developed to objectively rank each material to be used in estimating NH₃ emissions. The results of this study highlight microfiber glass filters as the most effective acid-coated matrix, combining favorable aerodynamic behaviors with low variability (28 %). In contrast, porous materials such as zeolite and biochar showed high promising sorption capacities (12 573 μg and 3928 μg, respectively) but exhibited high variability (58 % and 37 %), limiting their reliability under field conditions. The methodology developed, the weighted index to select the best sorbent, lays the groundwork for a standardized, reproducible, and transferable approach to sorption evaluation in PFS devices, contributing to more reliable, scalable, and cost-efficient air quality monitoring strategies.