The deuterium content of atmospheric molecular hydrogen: Method and initial measurements
2000; American Geophysical Union; Volume: 105; Issue: D21 Linguagem: Inglês
10.1029/2000jd900387
ISSN2156-2202
Autores Tópico(s)Atmospheric chemistry and aerosols
ResumoA new technique for determining the δD of atmospheric molecular hydrogen (H 2 ) at background mixing ratios is described in detail. An air sample is compressed into a high‐pressure cylinder, after which the cylinder is cooled to −196°C to condense the air and generate a headspace greatly enriched in H 2 . The H 2 ‐enriched headspace is collected and admitted into a high‐vacuum extraction line, where the H 2 is separated from the headspace gases by combustion to water followed by cryogenic collection. The H 2 ‐derived water is then reduced back to H 2 for measurement of its D/H content via isotope‐ratio mass spectrometry. The primary limitation of the method is contamination during compressor collection and subsequent storage of air samples in high‐pressure cylinders. The δD of atmospheric H 2 was measured on air samples collected between 46°N and 72°S during a research cruise in the Pacific Ocean during 1998 and at Cheeka Peak, Washington (48°N), during 1997–1999 and Point Barrow, Alaska (71°N), during 1996–1997. These measurements yield a global average δD of atmospheric H 2 of +130±4‰ and average Northern and Southern Hemispheric δD values of +123±3‰ and +138±8‰, respectively (versus Vienna standard mean ocean water).
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