초록 ▼

A sensitive, compact detector measures total reactive nitrogen (NOy), as well as NO2, NO, and O3. In all channels, NO2 is directly detected by laser diode based cavity ring-down spectroscopy (CRDS) at 405 nm. Ambient O3 is converted to NO2 in excess NO for the O3 measurement channel. Likewise, ambie

A sensitive, compact detector measures total reactive nitrogen (NOy), as well as NO2, NO, and O3. In all channels, NO2 is directly detected by laser diode based cavity ring-down spectroscopy (CRDS) at 405 nm. Ambient O3 is converted to NO2 in excess NO for the O3 measurement channel. Likewise, ambient NO is converted to NO2 in excess O3. Ambient NOy is thermally dissociated at 700 C to form NO2 or NO in a heated quartz inlet. Any NO present in ambient air or formed from thermal dissociation of other reactive nitrogen compounds is converted to NO2 in excess O3 after the thermal converter. The precision and accuracy of this instrument make it a versatile alternative to standard chemiluminescence-based NOy instruments.

대표청구항 ▼

1. 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

1. 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; anda 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; anda 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; anda 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; anda 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. 2. The instrument of claim 1, further comprising: a data processing system, receiving the first output signal and calculating reactive nitrogen content in the gas sample as a function of the first output signal. 3. The instrument of claim 2, wherein the first gas sample, the second gas sample, the third gas sample, and the fourth gas sample each comprise an atmospheric air sample, each collected contemporaneously with one another. 4. The instrument of claim 3, wherein the data processing system subtracts the second output signal proportional to measured ambient nitrogen dioxide content value as measured by the second channel from the third output signal proportional to measured ambient nitrogen oxides (NOx) content value as measured by the third channel to calculate nitric oxide (NO) in the gas samples. 5. The instrument of claim 3, wherein the data processing system subtracts second output signal proportional to measured ambient nitrogen oxides (NOx) content value as measured by the second channel from the first output signal proportional to reactive nitrogen content (NOy) value as measured by the first channel, to calculate oxidized reactive nitrogen (NOz) in the gas samples. 6. The instrument of claim 3, wherein the data processing system subtracts the fourth output signal proportional to ozone content value as measured by the fourth channel, from the second output signal proportional to nitrogen dioxide content value as measured by the second channel, to calculate ozone content in the gas samples. 7. The instrument of claim 1, wherein the heater comprises a quartz tube wrapped with nichrome wire. 8. A method of simultaneously measuring at least reactive nitrogen content, nitrogen dioxide content, the ambient nitrogen oxides (NOx═NO+NO2) content and ozone content in a gas samples, comprising the steps of: generating a laser beam with a laser;dividing, in a beam divider coupled to the laser, the primary laser beam into at least a first laser beam, a second laser beam, a third laser beam, and a fourth laser beam;measuring reactive nitrogen (NOy) content in a first channel comprising the steps of: heating a first gas sample in a heater, to decompose reactive nitrogen in the first gas sample into nitrogen oxides outputting a decomposed first gas sample;reacting the decomposed first gas sample with ozone in a first reactor coupled to the heater and an ozone supply, to react nitric oxide in the decomposed first gas sample with the ozone, into nitrogen dioxide to produce a decomposed and reacted first gas sample;measuring nitrogen dioxide content in the decomposed and reacted first gas sample in a first cavity ring-down spectrometer coupled to the reactor, the first cavity ring-down spectrometer comprising a first optical cavity coupled to 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 the concentration of the nitrogen oxide in the first optical cavity; andoutputting from the first cavity ring-down spectrometer, an output signal proportional to the nitrogen dioxide content in the decomposed reacted first gas sample;wherein the nitrogen dioxide content in the decomposed reacted first gas sample is proportional to the reactive nitrogen content in the first gas sample and the output signal is proportional to the total reactive nitrogen content in the first gas sample;measuring nitrogen dioxide content in a the second channel, comprising the steps of: measuring, in 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 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;measuring ambient nitrogen oxides (NOx═NO+NO2)) content in a third channel, comprising the steps of: reacting, in a second reactor receiving a third gas sample, and to the ozone supply, the second reactor receiving the third gas sample and ozone and reacting nitric oxide (NO) in the third gas sample into nitrogen dioxide (NO2) to produce a reacted third gas sample;measuring, in 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 third 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 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 oxide in the third optical cavity, wherein the nitrogen dioxide content in the third gas sample is proportional to the ambient nitrogen oxides (NOx) 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;measuring ozone content in a fourth channel, comprising the steps of: reacting, in a third reactor receiving a fourth gas sample and to a nitrogen oxide (NO) supply, the third reactor receiving the fourth gas sample and nitrogen oxide and reacting ozone in the fourth gas sample with nitrogen oxide into nitrogen dioxide to produce a reacted fourth gas sample;measuring, in 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 first 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. 9. The method of claim 8, wherein the first gas sample, the second gas sample, the third gas sample, and the fourth gas sample each comprise an atmospheric air sample, each collected contemporaneously with one another. 10. The method of claim 9, wherein the step of heating the first gas sample comprises the step of heating the first gas sample to substantially 650° C. to 750° C. to decompose reactive nitrogen NOy into nitrogen oxides NO and NO2. 11. The method of claim 10, wherein the heater comprises a quartz tube wrapped with nichrome wire. 12. The method of claim 9, further comprising the steps of: subtracting, in a data processing system, the second output signal proportional to the measured ambient nitrogen dioxide content value as measured by the second channel from the third output signal proportional to the measured ambient nitrogen oxides (NOx) content value as measured by the third channel to calculate nitrogen oxide (NO) in the gas samples. 13. The method of claim 9, further comprising the steps of: subtracting in a data processing system, the second output signal proportional to the measured ambient nitrogen oxides (NOx) content value as measured by the second channel from the first output signal proportional to the measured reactive nitrogen content (NOy) in the first gas sample as measured by the first channel to calculate oxidized reactive nitrogen (NOz) in the gas samples. 14. The method of claim 9, further comprising the step of: subtracting, in a data processing system, the fourth output signal proportional to ozone content value as measured by the fourth channel, from the second output signal proportional to nitrogen dioxide content value as measured by the second channel, to calculate ozone content in the gas samples.