Browsing by Author "Martin, Nicholas A."

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    Production and stability of low amount fraction of formaldehyde in hydrogen gas standards
    (Elsevier, 2018-03-03) Bacquart, Thomas; Perkins, Mark; Ferracci, Valerio; Martin, Nicholas A.; Resner, Kate; Ward, Michael K. M.; Cassidy, Nathan; Hook, Joshua B.; Brewer, Paul J.; Irvine, John T. C.; Connor, Paul A.; Murugan, Arul
    Formaldehyde is an intermediate of the steam methane reforming process for hydrogen production. According to International Standard ISO 14687-2 the amount fraction level of formaldehyde present in hydrogen supplied to fuel cell electric vehicles (FCEV) must not exceed 10 nmol mol−1. The development of formaldehyde standards in hydrogen is crucial to validate the analytical results and ensure measurement reliability for the FCEV industry. NPL demonstrated that these standards can be gravimetrically prepared and validated at 10 μmol mol−1 with a shelf-life of 8 weeks (stability uncertainty <10%; k = 1), but that formaldehyde degrades into methanol and dimethoxymethane, as measured by FTIR, GC-MS and SIFT-MS. The degradation kinetics is more rapid than predicted by thermodynamics, this may be due to the internal gas cylinder surface acting as a catalyst. The identification of by-products (methanol and dimethoxymethane) requires further investigation to establish any potential undesirable impacts to the FCEV.
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    Revisiting the concentration observations and source apportionment of atmospheric ammonia
    (Springer, 2020-08-13) Pan, Yuepeng; Gu, Mengna; He, Yuexin; Wu, Dianming; Liu, Chunyan; Song, Linlin; Tian, Shili; Lü, Xuemei; Sun, Yang; Song, Tao; Walters, Wendell W.; Liu, Xuejun; Martin, Nicholas A.; Zhang, Qianqian; Fang, Yunting; Ferracci, Valerio; Wang, Yuesi
    While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on whether agricultural or non-agricultural emissions dominate the urban ammonia budget. Identifying the ammonia source by nitrogen isotope helps in designing a mitigation strategy for policymakers, but existing methods have not been well validated. Revisiting the concentration measurements and identifying source apportionment of atmospheric ammonia is thus an essential step towards reducing ammonia emissions.