Research Collection Doctoral Thesis Microscale Distribution of Environmental Proxies in Snow Author(s): Trachsel, Jürg Publication Date: 2019 Permanent Link: https://doi.org/10.3929/ethz-b-000387457 Rights / License: Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library DISS. ETH NO. 26360 Microscale Distribution of Environmental Proxies in Snow A thesis submitted to attain the degree of DOCTOR OF SCIENCES of ETH Zurich (Dr. sc. ETH Zurich) presented by JÜRG CHRISTIAN TRACHSEL MSc ETH in Civil Engineering born on 06 January 1986 citizen of Brugg AG and Wattenwil BE accepted on the recommendation of Prof. Dr. Konrad Steffen Dr. Martin Schneebeli Dr. Franziska Scholder-Aemisegger Dr. Ulrich Krieger 2019 “People think focus means saying yes to the thing you've got to focus on. But that's not what it means at all. It means saying no to the hundred other good ideas that there are. You have to pick carefully.” Steve Jobs, 1997 Contents Zusammenfassung........................................................................................................................ v Summary ..................................................................................................................................... ix 1 Introduction ............................................................................................................................ 1 1.1 Project Overview ........................................................................................................................ 2 1.2 Snow – an environmental proxy ................................................................................................. 2 1.3 Instrument development and experimental .............................................................................. 4 1.3.1 Droplet Chopper (PSI) – Artificial snow .............................................................................. 4 1.3.2 Metamorphism chamber (SLF) – “Aging” snow .................................................................. 5 1.3.3 Micro-computer tomography scanner (SLF) – Snow structure analysis ............................. 6 1.3.4 Elution experiments (SLF) – Investigation of ion (re)distribution in the snow ................... 7 1.3.5 Ion chromatography (IC) and plasma mass spectrometry (ICP-SF-MS) (PSI) ..................... 7 1.3.6 Picarro laser spectrometry (Weissfluhjoch) – Water vapor isotope measurement .......... 8 1.3.7 Sampling snow pit – Collecting impurity records ............................................................... 9 1.4 Study site .................................................................................................................................. 10 1.5 Goals and Outline ..................................................................................................................... 11 References ........................................................................................................................................ 13 2 Microscale rearrangement of ammonium induced by snow metamorphism ............................ 19 Abstract ............................................................................................................................................ 20 2.1 Introduction .............................................................................................................................. 20 2.2 Methods ................................................................................................................................... 23 2.2.1 Preparation of artificial and natural snow samples .......................................................... 23 2.2.1.1 Preparation of artificial snow ................................................................................ 23 2.2.1.2 Sampling of natural snow at WFJ .......................................................................... 24 2.2.2 Laboratory-controlled and natural snow metamorphism ................................................ 24 2.2.2.1 Laboratory-controlled metamorphism experiment .............................................. 24 2.2.2.2 Natural metamorphism: Samples of natural snow from a WFJ snow pit ............. 26 2.2.3 Elution Experiments .......................................................................................................... 26 2.2.4 Vertical distribution of ions after temperature gradient storage..................................... 27 2.2.5 Ion chromatography (IC) ................................................................................................... 28 2.2.6 X-ray microtomography (microCT) ................................................................................... 28 i Contents 2.3 Results ...................................................................................................................................... 28 2.3.1 Structural development during metamorphism ............................................................... 28 2.3.1.1 Temperature gradient metamorphism ................................................................. 28 2.3.1.2 Isothermal metamorphism .................................................................................... 31 + 2.3.2 Redistribution of NH4 and other major ions during snow metamorphism ..................... 31 2.3.2.1 Elution experiments .............................................................................................. 31 2.3.2.2 Temporal changes of ion concentrations in first eluate and residual snow ......... 33 2.3.2.3 Temporal changes in ion concentrations under isothermal conditions................ 34 + 2.3.2.4 Enrichment of NH4 in the residual sample (gradient/isothermal) ....................... 34 2.3.2.5 Vertical distribution of ions after temperature gradient storage ......................... 35 2.4 Discussion ................................................................................................................................. 35 2.4.1 Structural change under temperature gradient metamorphism ..................................... 36 2.4.2 Structural changes under isothermal conditions .............................................................. 37 + 2.4.3 Rearrangement of NH4 and other major ions during snow metamorphism ................... 37 2.4.3.1 Initial chemical characterization of the snow ....................................................... 38 2.4.3.2 First eluate vs residual sample: What we learn with respect to accessibility? ..... 39 2.4.3.3 Impact of structural changes during metamorphism on distribution of ions ....... 41 2.4.3.4 Environmental implications ................................................................................... 45 2.5 Conclusion ................................................................................................................................ 46 Acknowledgements .......................................................................................................................... 47 References ........................................................................................................................................ 48 3 Melt-induced fractionation of major ions and trace elements in an Alpine snowpack .............. 57 Abstract ............................................................................................................................................ 58 3.1 Introduction .............................................................................................................................. 58 3.2 Materials and Methods ............................................................................................................ 60 3.2.1 Study site and meteorological setting .............................................................................. 60 3.2.2 Snow pit sampling ............................................................................................................. 61 3.2.3 Major ion, water stable isotope and trace element analysis ........................................... 62 3.2.4 Data Evaluation ................................................................................................................. 62 3.3 Results and Discussion .............................................................................................................. 63 3.3.1 Major ions (MIs) ................................................................................................................ 63 3.3.1.1 Comparison of the five MI concentration profiles ................................................ 63 3.3.1.2 Preferential elution of MIs: Elution sequence and discussion .............................. 64 3.3.2 Trace elements (TEs) ......................................................................................................... 67 3.3.2.1 TE concentration profiles ...................................................................................... 67 3.3.2.2 Different preservation of TEs under melt conditions ............................................ 69 3.4 Conclusion ................................................................................................................................ 72 ii Contents Acknowledgements .......................................................................................................................... 73 References .......................................................................................................................................