Infrared source, carbon dioxide

As shown in Fig. 4-42, carbon dioxide (C02) absorbs the second largest amount of long-wave infrared radiation in the atmosphere (about 32% Mann and Lazier, 1996). Over Earth s history, the predominant natural source of CO2 in the atmosphere has been volcanic eruptions, and the vast majority of that C02 is now stored in ocean sediments and rocks derived from those sediments (Mann and Lazier, 1996). If Earth did not have oceans, the concentration of C02 in Earth s atmosphere would be far higher than it is currently. 

The most abundant carbon-containing compound in the stratosphere and mesosphere is carbon dioxide (CO2). By interacting with infrared radiation, this gas plays an important role in the thermal budget of the atmosphere, and the 30% increase in its concentration resulting mainly from fossil fuel burning has provided a significant forcing to the climate system of about 1.5 Wm 2 (IPCC, 2001). Carbon dioxide does not play any substantial role in the chemistry of the atmosphere except in the lower thermosphere, where its photolysis is an important source of carbon monoxide (CO). This latter gas, which is also released at the Earth s surface by incomplete combustion (pollution) and is partially transported to the stratosphere, is converted to CO2 by reaction with the hydroxyl radical (OH). 

The EPA Method 10 discusses measuring carbon monoxide emissions from stationary sources from continuous samples extracted from an exhaust stack where the sample is measured with nondispersive infrared (NDIR) analyzer. Possible interferences include water, carbon dioxide, and carbon monoxide. Method lOA tells how to make certified carbon monoxide measurements from continuous emission monitoring systems (CEMS) at petroleum refineries. 

The nitrogen laser is pumped with a high-vollagc spark source that provides a momentary (1 to 5 ns) puLse of current through the gas. I he excitation creates a population inversion that decays very quickly by spontaneous emission because the lifetime of the excited stale is quite short relative to the lifetime of the lower level. The result is a short (a few nanoseconds) pulse of intense (up to I MW) radiaiion at. 337,1 nm. This output is used for exciting fluorescence in a variety of molecules and for pumping dye lasers. I he carbon dioxide gas laser is used to produce monochromatic Infrared radiation at 10.6 pm. 

The uncertainties in absorptance measurements for a specific mass of gas deposited are approximately 3 % for the infrared measurements and 5 % for the mercury-xenon source measurements. However, the uncertainties in deposit thicknesses for a specific mass of gas deposited are 11 % for water vapor and 12% for carbon dioxide. 

A sample is acidified, sparged, and injected directly into the reagent stream. The mixture flows through the reactor where organics are oxidised by the photon-activated reagent. The light source envelope is in direct contact with the flowing liquid. Oxidation proceeds rapidly, the resultant carbon dioxide is stripped from the reactor liquid and carried to the carbon dioxide-specific non-dispersive infrared (IR) detector. 

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