The URG-9000NS Ambient Nitrate & Sulfate Monitor provides time-resolved, direct measurements of anion particulate nitrate and sulfate contained in suspended fine particulate matter (PM-2.5). In its standard operational setting, the instrument generates a new particulate nitrate and sulfate measurement in micrograms per cubic meter (µg/m3) every hour. It can function as either a free-standing or rack-mounted unit and is automated for continuous, unattended operation in air quality monitoring stations.
Ambient particulate nitrate and sulfate can represent major fractions of the PM-2.5 concentration in certain areas—namely those where fuel combustion results in sulfur dioxide (SO2) emissions; it is often produced as a result of the interaction of ammonia (NH3), NOx, SO2 and other gaseous constituents. Its measurement can also be important with respect to understanding visibility degradation, atmospheric chemistry, and inputs into various ecosystems.
The Ambient Nitrate & Sulfate Monitor draws air in through a PM-2.5 sharp cut cyclone at a volumetric flow rate of 3Lpm to remove the larger particles from the air stream. The monitor then incorporates several state-of-the-art components to achieve continuous, direct measurements.
A sample is drawn through a liquid diffusion denuder where interfering acidic and basic gases are removed. In order to achieve high collection efficiencies, the particle-laden air stream next enters the aerosol super-saturation chamber to enhance particle growth. An inertial particle separator collects these enlarged particles and stores them in an aerosol sample collector until the particles can be injected into the Ambient Ion Detector. The particles are collected and injected using syringe pumps, PEEK™ valves, and PEEK™ and Teflon® tubing.
Ion Chromatography is the analysis method for the URG Ambient Nitrate & Sulfate Monitor. An Ion Chromatograph requires as little as 4 liters of deionized water for up to 28 sampling days and remains equilibrated and calibrated between eluent changes for up to 4 weeks.
The URG Ambient Nitrate & Sulfate Monitor includes a Eluent Regeneration Ion Chromatography System (IC). The IC System separates the nitrate and sulfate ions so that the measurements are not affected by other nitrogen-containing compounds. Losses due to volatilization are eliminated due to the collection of the particles in a solution that is then analyzed by Ion Chromatography.
The analytical technique used in the Ambient Nitrate & Sulfate Monitor has undergone thorough laboratory testing with liquid standards and is fully inspected and calibrated before leaving the factory. The monitor contains software support for flow calibrations conducted by the end user.
The instrument transmits collected data to an external device via USB and serial cables where the information is displayed and processed in the Microsoft® Windows® based program and Chromeleon®. The data is displayed in micrograms per cubic meter.