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  • 1
    Online Resource
    Online Resource
    Unexpected nascent atmospheric emissions of three ozone-depleting hydrochlorofluorocarbons
    Proceedings of the National Academy of Sciences ; 2021
    In:  Proceedings of the National Academy of Sciences Vol. 118, No. 5 ( 2021-02-02)
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 118, No. 5 ( 2021-02-02)
    Abstract: Global and regional atmospheric measurements and modeling can play key roles in discovering and quantifying unexpected nascent emissions of environmentally important substances. We focus here on three hydrochlorofluorocarbons (HCFCs) that are restricted by the Montreal Protocol because of their roles in stratospheric ozone depletion. Based on measurements of archived air samples and on in situ measurements at stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, we report global abundances, trends, and regional enhancements for HCFC-132b ( C H 2 C l C C l F 2 ), which is newly discovered in the atmosphere, and updated results for HCFC-133a ( C H 2 C l C F 3 ) and HCFC-31 ( C H 2 ClF). No purposeful end-use is known for any of these compounds. We find that HCFC-132b appeared in the atmosphere 20 y ago and that its global emissions increased to 1.1 Gg ⋅ y −1 by 2019. Regional top-down emission estimates for East Asia, based on high-frequency measurements for 2016–2019, account for ∼ 95% of the global HCFC-132b emissions and for ∼ 80% of the global HCFC-133a emissions of 2.3 Gg ⋅ y −1 during this period. Global emissions of HCFC-31 for the same period are 0.71 Gg ⋅ y −1 . Small European emissions of HCFC-132b and HCFC-133a, found in southeastern France, ceased in early 2017 when a fluorocarbon production facility in that area closed. Although unreported emissive end-uses cannot be ruled out, all three compounds are most likely emitted as intermediate by-products in chemical production pathways. Identification of harmful emissions to the atmosphere at an early stage can guide the effective development of global and regional environmental policy.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.2010914118
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2021
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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  • 2
    Online Resource
    Online Resource
    Weak Northern and Strong Tropical Land Carbon Uptake from Vertical Profiles of Atmospheric CO 2
    American Association for the Advancement of Science (AAAS) ; 2007
    In:  Science Vol. 316, No. 5832 ( 2007-06-22), p. 1732-1735
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 316, No. 5832 ( 2007-06-22), p. 1732-1735
    Abstract: Measurements of midday vertical atmospheric CO 2 distributions reveal annual-mean vertical CO 2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO 2 gradients estimate weaker northern uptake of –1.5 petagrams of carbon per year (Pg C year –1 ) and weaker tropical emission of +0.1 Pg C year –1 compared with previous consensus estimates of –2.4 and +1.8 Pg C year –1 , respectively. This suggests that northern terrestrial uptake of industrial CO 2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO 2 .
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1137004
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2007
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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  • 3
    Online Resource
    Online Resource
    H 2 in Antarctic firn air: Atmospheric reconstructions and implications for anthropogenic emissions
    Proceedings of the National Academy of Sciences ; 2021
    In:  Proceedings of the National Academy of Sciences Vol. 118, No. 36 ( 2021-09-07)
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 118, No. 36 ( 2021-09-07)
    Abstract: The atmospheric history of molecular hydrogen (H 2 ) from 1852 to 2003 was reconstructed from measurements of firn air collected at Megadunes, Antarctica. The reconstruction shows that H 2 levels in the southern hemisphere were roughly constant near 330 parts per billion (ppb; nmol H 2 mol −1 air) during the mid to late 1800s. Over the twentieth century, H 2 levels rose by about 70% to 550 ppb. The reconstruction shows good agreement with the H 2 atmospheric history based on firn air measurements from the South Pole. The broad trends in atmospheric H 2 over the twentieth century can be explained by increased methane oxidation and anthropogenic emissions. The H 2 rise shows no evidence of deceleration during the last quarter of the twentieth century despite an expected reduction in automotive emissions following more stringent regulations. During the late twentieth century, atmospheric CO levels decreased due to a reduction in automotive emissions. It is surprising that atmospheric H 2 did not respond similarly as automotive exhaust is thought to be the dominant source of anthropogenic H 2. The monotonic late twentieth century rise in H 2 levels is consistent with late twentieth-century flask air measurements from high southern latitudes. An additional unknown source of H 2 is needed to explain twentieth-century trends in atmospheric H 2 and to resolve the discrepancy between bottom-up and top-down estimates of the anthropogenic source term. The firn air–based atmospheric history of H 2 provides a baseline from which to assess human impact on the H 2 cycle over the last 150 y and validate models that will be used to project future trends in atmospheric composition as H 2 becomes a more common energy source.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.2103335118
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
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