Site selective real-time measurements of atmospheric N<sub>2</sub>O isotopomers by laser spectroscopy
We describe the first high precision real-time analysis of the N<sub>2</sub>O site-specific isotopic composition at ambient mixing ratios. Our technique is based on mid-infrared quantum cascade laser absorption spectroscopy (QCLAS) combined with an automated preconcentration unit. The QC...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2012-07-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/5/1601/2012/amt-5-1601-2012.pdf |
| Summary: | We describe the first high precision real-time analysis of the N<sub>2</sub>O site-specific isotopic composition at ambient mixing ratios. Our technique is based on mid-infrared quantum cascade laser absorption spectroscopy (QCLAS) combined with an automated preconcentration unit. The QCLAS allows for simultaneous and specific analysis of the three main stable N<sub>2</sub>O isotopic species, <sup>14</sup>N<sup>15</sup>N<sup>16</sup>O, <sup>15</sup>N<sup>14</sup>N<sup>16</sup>O, <sup>14</sup>N<sup>14</sup>N<sup>16</sup>O, and the respective site-specific relative isotope ratio differences δ<sup>15</sup>N<sup>α</sup> and δ<sup> 15</sup>N<sup>β</sup>. Continuous, stand-alone operation is achieved by using liquid nitrogen free N<sub>2</sub>O preconcentration, a quasi-room-temperature quantum cascade laser (QCL), quantitative sample transfer to the QCLAS and an optimized calibration algorithm. The N<sub>2</sub>O site-specific isotopic composition (δ<sup>15</sup>N<sup>α</sup> and δ<sup>15</sup>N<sup>β</sup>) can be analysed with a long-term precision of 0.2‰. The potential of this analytical tool is illustrated by continuous N<sub>2</sub>O isotopomer measurements above a grassland plot over a three week period, which allowed identification of microbial source and sink processes. |
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| ISSN: | 1867-1381 1867-8548 |