A multi-channel instrument for simultaneously measuring at least reactive nitrogen (NOy) content, nitrogen dioxide content, ambient nitrogen oxides (NOx═NO+NO2)) content and ozone content in gas samples, the multi-channel instrument comprising:
- a laser producing a primary laser beam;
- beam divider coupled to the laser, dividing the primary laser beam into at least a first laser beam, a second laser beam, a third laser beam, and a fourth laser beam;
- a first channel measuring reactive nitrogen (NOy) content, the first channel comprising:
- a heater receiving a first gas sample, the heater heating the first gas sample and decomposing reactive nitrogen in the first gas sample into nitrogen oxides to output a decomposed first gas sample;
- a first reactor, coupled to the heater and an ozone supply, receiving the decomposed first gas sample and ozone and reacting nitrogen oxide in the decomposed first gas sample into nitrogen dioxide to produce a decomposed and reacted first gas sample;
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- a first cavity ring-down spectrometer, coupled to the first reactor and receiving the decomposed and reacted first gas sample, measuring the nitrogen dioxide content of the decomposed reacted first gas sample, and outputting a first output signal proportional to the nitrogen dioxide content in the decomposed reacted first gas sample, the first cavity ring-down spectrometer comprising a first optical cavity coupled to the beam divider and receiving the first laser beam, the first laser beam traversing the first optical cavity, such that when the laser is turned off, measurement is made of time for light from the first laser beam to decay to 1/e of its initial intensity to calculate concentration of the nitrogen dioxide in the first optical cavity, wherein the nitrogen dioxide content in the decomposed reacted first gas sample is proportional to the reactive nitrogen content (NOy) in the first gas sample and the first output signal is proportional to the total reactive nitrogen content (NOy) in the first gas sample;
- a second channel, measuring nitrogen dioxide content, the second channel comprising:
- a second cavity ring-down spectrometer receiving a second gas sample, the second cavity ring-down spectrometer measuring the nitrogen dioxide content of the second gas sample, and outputting a second output signal proportional to the ambient nitrogen dioxide content in the second gas sample, the second cavity ring-down spectrometer comprising a second optical cavity, coupled to the beam divider and receiving the second laser beam, the second laser beam traversing the second optical cavity, such that when the laser is turned off, measurement is made of time for light from the second laser beam to decay to 1/e of its initial intensity to calculate concentration of the nitrogen dioxide in the second optical cavity, producing the second output signal proportional to the ambient nitrogen dioxide content in the second gas sample;
- a third channel, measuring ambient nitrogen oxides (NOx═NO+NO2)) content, the third channel comprising:
- a second reactor, coupled to the ozone supply, the second reactor receiving a third gas sample and ozone and reacting nitric oxide (NO) in the third gas sample into nitrogen dioxide (NO2) to produce reacted third sample;
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- a third cavity ring-down spectrometer, coupled to the second reactor and receiving the reacted third gas sample, measuring the nitrogen dioxide content of the reacted third gas sample, and outputting an output signal proportional to the nitrogen dioxide content in the reacted third gas sample, the second cavity ring-down spectrometer comprising a third optical cavity, coupled to the beam divider and receiving the third laser beam, the third laser beam traversing the third optical cavity, such that when the laser is turned off, measurement is made of time for light from the third laser beam to decay to 1/e of its initial intensity to calculate concentration of the nitrogen dioxide in the third optical cavity, wherein the nitrogen dioxide content in the second reacted gas sample is proportional to the ambient nitrogen oxides (NOx═NO+NO2)) content in the third gas sample and the third output signal is proportional to the ambient nitrogen oxides (NOx) content in the third gas sample;
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- a fourth channel measuring ozone content, the fourth channel comprising:
- a third reactor, coupled to a nitric oxide (NO) supply, the third reactor receiving a fourth gas sample and nitric oxide and reacting ozone in the fourth gas sample with nitric oxide into nitrogen dioxide to produce a reacted fourth gas sample;
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- a fourth cavity ring-down spectrometer, coupled to the third reactor and receiving the reacted fourth gas sample, measuring the nitrogen dioxide content of the reacted fourth gas sample, and outputting an output signal proportional to the nitrogen dioxide content in the reacted fourth gas sample, the fourth cavity ring-down spectrometer comprising a fourth optical cavity, coupled to the beam divider and receiving the fourth laser beam, the fourth laser beam traversing the fourth optical cavity, such that when the laser turned off, measurement is made of time for light from the fourth laser beam to decay to 1/e of its initial intensity to calculate concentration of the nitrogen dioxide in the fourth optical cavity, wherein the nitrogen dioxide content in the reacted fourth gas sample is proportional to the ozone content in the fourth gas sample plus the ambient nitrogen dioxide in the fourth gas sample and the output signal is proportional to the ozone content in the fourth gas sample plus the ambient nitrogen dioxide in the fourth gas sample.