Light emitting diode cavity enhanced differential optical absorption spectroscopy (LED-CE-DOAS): a novel technique for monitoring atmospheric trace gases

The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light- Emitting Diodes, LEDs) lends itself to the application of cavity enhanced DOAS (CE-DOAS) to perform sensitive and selective point measurements of multiple trace gases with a single instrument. In contrast to other broad-band CEAS techniques, CE-DOAS relies only on the measurement of relative intensity changes, i.e., does not require knowledge of the light intensity in the absence of trace gases and aerosols (I0). We have built a prototype LED-CE-DOAS instrument in the blue spectral range (420-490nm) to measure nitrogen dioxide (NO2), glyoxal (CHOCHO), iodine monoxide (IO), water (H2O) and oxygen dimers (O4). Aerosol extinction is retrieved at two wavelengths by means of observing water and O4 and measuring pressure, temperature and relative humidity independently. The instrument components are presented, and the approach to measure aerosol extinction is demonstrated by means of a set of experiments where laboratory generated monodisperse aerosols are added to the cavity. The aerosol extinction cross section agrees well with Mie calculations, demonstrating that our setup enables measurements of the above gases in open cavity mode.

[1]  J. Burrows,et al.  Simultaneous global observations of glyoxal and formaldehyde from space , 2006 .

[2]  D. Salcedo,et al.  A missing sink for gas‐phase glyoxal in Mexico City: Formation of secondary organic aerosol , 2007 .

[3]  A. O’Keefe,et al.  Cavity ring‐down optical spectrometer for absorption measurements using pulsed laser sources , 1988 .

[4]  M. Molina,et al.  Remote Sensing of Glyoxal by Differential Optical Absorption Spectroscopy (DOAS): Advancements in Simulation Chamber and Field Experiments , 2006 .

[5]  L. Hernández-Mena,et al.  Biodirected mutagenic chemical assay of PM(10) extractable organic matter in Southwest Mexico City. , 2007, Mutation research.

[6]  M. Molina,et al.  DOAS measurement of glyoxal as an indicator for fast VOC chemistry in urban air , 2005 .

[7]  Prompt deliquescence and efflorescence of aerosol nanoparticles , 2006 .

[8]  Owen B. Toon,et al.  The optical constants of several atmospheric aerosol species: Ammonium sulfate, aluminum oxide, and sodium chloride , 1976 .

[9]  M. Molina,et al.  Secondary organic aerosol formation from anthropogenic air pollution: Rapid and higher than expected , 2006 .

[10]  A. Wiedensohler,et al.  An approximation of the bipolar charge distribution for particles in the submicron size range , 1988 .

[11]  T. Leisner,et al.  Using a high finesse optical resonator to provide a long light path for differential optical absorption spectroscopy: CE-DOAS , 2008 .

[12]  D. Dockery,et al.  Health Effects of Fine Particulate Air Pollution: Lines that Connect , 2006, Journal of the Air & Waste Management Association.

[13]  Peter Spietz,et al.  High-resolution absorption cross-section of glyoxal in the UV–vis and IR spectral ranges , 2005 .

[14]  Hendrik Fuchs,et al.  Measurement of glyoxal using an incoherent broadband cavity enhanced absorption spectrometer , 2008 .

[15]  T. Wagner,et al.  MAX-DOAS detection of glyoxal during ICARTT 2004 , 2006 .

[16]  John H. Seinfeld,et al.  Chamber studies of secondary organic aerosol growth by reactive uptake of simple carbonyl compounds , 2005 .

[17]  Ulrich Platt,et al.  Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) – applicability and corrections , 2008 .

[18]  Ulrich Platt,et al.  Differential optical absorption spectroscopy (DOAS) , 1994 .

[19]  Jun Q. Lu,et al.  Determination of complex refractive index of polystyrene microspheres from 370 to 1610 nm , 2003, Physics in medicine and biology.

[20]  Robert McLaren,et al.  Reactive uptake of glyoxal by particulate matter , 2005 .

[21]  Steven S Brown,et al.  Absorption spectroscopy in high-finesse cavities for atmospheric studies. , 2003, Chemical reviews.

[22]  R. Kamens,et al.  Heterogeneous Atmospheric Aerosol Production by Acid-Catalyzed Particle-Phase Reactions , 2002, Science.

[23]  Ulrich Platt,et al.  Correction of the oxygen interference with UV spectroscopic (DOAS) measurements of monocyclic aromatic hydrocarbons in the atmosphere , 1998 .

[24]  Christoph Kern,et al.  Applicability of light-emitting diodes as light sources for active differential optical absorption spectroscopy measurements. , 2006, Applied optics.

[25]  J. Burrows,et al.  The continental source of glyoxal estimated by the synergistic use of spaceborne measurements and inverse modelling , 2009 .