Time-Resolved Particle and Gas Measuring Systems

The 9000 series Ambient Ion Monitor (AIM) provides time-resolved direct measurements of anion particulate nitrate, sulfate, nitrite, phosphate and chloride found in PM-2.5. Nitrite and sulfate aerosols are produced as a result of the interaction of ammonia (NH3), NOX, SO2, and other gaseous constituents. These ions can represent a significant portion of the PM-2.5 and are important in understanding visibility degradation, atmospheric chemistry and inputs into various ecosystems. Other models in the series provide additional Ion Detection of cation particulates, anion gases and ammonia.

Sample Collection

The AIM incorporates several state-of-the-art components for sample collection. It draws air in through a PM-2.5 sharp-cut cyclone at a volumetric-flow controlled rate of 3Lpm to remove the large particles from the air stream. The sample is then drawn through a Liquid Diffusion Denuder where interfacing acid gases are removed. In order to achieve high collection efficiencies, the particle-laden air stream enters the Aerosol Super-Saturation Chamber to enhance particle growth. An Inertial Particle Separator collects these enlarge particles, which are then injected into the Ion Chromatograph. Both particles and gases are collected and injected using syringe pumps, PEEK™ valves, Teflon® tubing and PEEK™ tubing.

The sampler can collect and analyze up to 10 days unattended. This period can be extended, if necessary, by using larger solution reservoirs.

Analysis Method

The analysis method for the AIM is Ion Chromatography from Dionex®. An AIM requires as little as 4 liters of deionized water for 10 sampling days. The detection limit is 0.05µg per cubic meter and can be less depending on which ion is being measured. The Ion Chromatography separates the nitrate and sulfate ions, so that the measurements are not affected by other nitrogen-containing compounds. Losses due to volatilization are eliminated because the particles are collected in a solution and then analyzed by Ion Chromatography.