The following article was generated with the assistance of an outside source using our products. Content was provided from the public information published on the Ammonia Monitoring Network website.
The National Atmospheric Deposition Program (NADP) launched the Ammonia Monitoring Network (AMoN) in 2010; but first piloted a passive sampling program beginning in 2007 with 16 test sites, experimenting with different types of passive sampling devices. Illinois Water Survey (IWS) operates as the Central Analytical Laboratory (CAL) for NADP’s AMoN. They deploy and analyze the ammonia test samples, and report the analytical data back to NADP.
Ammonia is emitted by many sources, including very important agricultural activities of fertilizer application and meat production. NADP’S AMoN provides useful information to the agricultural community to assess the fate and transport of ammonia in the atmosphere. Their goal is to measure atmospheric ammonia concentrations, and estimate dry deposition over North America. The network uses radiello; a low-cost, passive diffusion sampler, deployed every two weeks to 54 locations (Figure 1), providing an integrated and quality-assured measurement of ammonia in air.
Figure 1. NADP Ammonia Monitoring Network (AMoN)
The cartridge adsorbent (RAD168) is made of microporous polyethylene material and impregnated with phosphoric acid. Ammonia is adsorbed as ammonium ion. Airborne ammonium salts dispersed as particulate matter do not cross the diffusive membrane of radiello.
Ammonium ion is quantified by visible spectrometry as indophenol: at basic buffered pH ammonium ion reacts with phenol and sodium hypochlorite, with pentacyanonitrosylferrate catalysis (in the following cyanoferrate), to form indophenol. The reaction product is intense blue in color, with absorbance measured at 635 nm. (Figure 2).
Figure 2. Reaction of Ammonia on Adsorbent Cartridge
The sampler shelter (design available from Central Analytical Laboratory) consists of an inverted plastic shelter permanently fastened to an aluminum u-channel mounting bracket (Figure 3). The shelter is erected such that the lower edge is two meters (80 inches) above surrounding surfaces. The vertical arm of the aluminum bracket can be fastened to a metal fence post. Alternatively, the shelter can be mounted on a suitable wooden post or pole by using screws (or small lag bolts) driven through the predrilled holes in the lower part of the bracket. Triplicate radiello ammonia samplers are mounted within the shelter (Figure 4). Samplers are not mounted near plumbing stacks, chimneys, vents, exhausts or other possible sources of direct ammonia emissions.
Figure 3. Shelter Schematic
Figure 4. Installation of radiello Cartridges in Shelter
The radiello ammonia samplers are returned back to the Central Analytical Laboratory and analyzed. The cartridges are removed and the ammonia (as NH4+) is removed by sonication in deionized water, using Flow Injection Analysis (FIA).
The NADP selected radiello samplers based on their ease of use and deployment (no sampling pump or calibration requirement), as well as the quality of obtained data. In order to ensure the radiello samplers perform according to the AMoN criteria, they are compared against a denuder reference method at the Illinois field site. A denuder differs from radiello in that it is an active sampling method requiring a sampling pump. The denuder is comprised of coated glass sampler. Below is a plot comparing the data for radiello vs. denuder for ammonia measurements (Figure 5).
Figure 5. Comparison of radiello and Denuder Measurements at Champaign County, Illinois
The radiello ammonia sampler impregnated with phosphoric acid represents a low-cost, reliable and simple tool for assessing the atmospheric deposition of ammonia at parts per billion (ppb) concentration levels.
For more information on the NADP AMoN network or to participate in the program, contact:
Christopher M.B. Lehmann, Ph.D.
Director, Central Analytical Laboratory
Illinois State Water Survey; Prairie Research Institute
University of Illinois at Urbana-Champaign
2204 Griffith Dr., Champaign, IL 61820-7495
Phone: (217) 265-8512, Fax: (217) 333-0249
radiello is a trademark of Fondazione Salvatore Maugeri IRCCS