The Ammonia Monitoring Network (AMoN), associated with the National Atmospheric Deposition Program (NADP), is currently measuring ambient ammonia concentrations (NH₃) at over 100 sites throughout the United States and Canada. To accomplish this, a passive sampler consisting of a Radiello^® adsorbent cartridge (microporous polyethylene impregnated with phosphoric acid) enclosed in a Radiello^® diffusive body is shipped to each of the sites. The samplers are deployed for two weeks under a protective shelter, after which the sampler is returned to the NADP Central Analytical Laboratory (Wisconsin State Laboratory of Hygiene), where the adsorbed ammonia (ammonium – NH₄) is extracted from the cartridge and the concentration determined with flow-injection spectrophotometry. In this presentation we will present the outcomes of three separate studies designed to address the efficacy of proposed sampler shipping improvements and sampler extraction optimization.

Study 1: Currently, a glass jar (with lid) is used to protect the sampler from contamination and damage during shipping; however, movement of the sampler within the glass jar can compromise its’ integrity and result in significant sampler attrition. This study investigated the use of plastic bags to ameliorate this issue; specifically, if placing the sampler inside a plastic bag will limit the motion of the sampler within the jar and thereby reduce damage. A comparison of damage rates during shipping of bagged samplers to those with no bags will be presented. We also investigated the potential for ammonia contamination from the bags.

Study 2:   This study evaluated the use of Mylar and anti-static bags as viable alternatives to glass jars, which are expensive to ship due to their weight and may contribute to sampler breakage.  Results from this study will be used to evaluate both barrier effectiveness to ambient ammonia and ammonia contamination issues.

Study 3: This study focused on optimization of the extraction protocol of ammonium from the adsorbent cartridge (core). The current procedure is to place the core into a Radiello^® tube and fill with 10.0 mL of 18.2 MΩ-cm water. The tube is then sonicated for 20 minutes and placed in a refrigerator overnight. The next day, the core is removed from the tube and the solution analyzed for ammonium. This study investigated the influence of sonication time and duration of core exposure to the 18.2 MΩ-cm water on ammonium desorption from the core. The outcomes of this study may point to improvements in ammonium extraction efficiency and quality/reproducibility of the ammonia data.