Mass independent fractionation in tropospheric H2O: Relation to precipitation pH, Ozone, Radiocarbon and Stratosphere-Troposphere Exchange

Ranjan, Shyam (2013). Mass independent fractionation in tropospheric H2O: Relation to precipitation pH, Ozone, Radiocarbon and Stratosphere-Troposphere Exchange (Unpublished). (Dissertation, Universität Bern, Philosophisch–naturwissenschaftliche Fakultät, Physikalisches Institut, Abteilung für Klima– und Umweltphysik)

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Water is a vital part for an existence of life on Earth. Discovery of isotopes and mass spectrometer identified the isotopes of water as a tracer for understanding the hydrological cycle and partly for the past temperature reconstruction in ice cores. Discovery of Mass independent fractionation (MIF) process through the chemical reaction in 1980s further extended the application of water isotopes and its ratio to understand the origin of solar system and global biosphere productivity on Earth.
My thesis contribute to understand the last three decades triple oxygen isotopic ratio of precipitated water in free troposphere, its relation to pH, temperature, relative humidity and ozone. Influence on triple oxygen isotope ratio and an isotopic anomaly during strong events i.e. Pinatubo eruption in 1991 and European heat wave event in 2003 also has been discussed in detail in my thesis. Additionally, an online continuous flow method by using the CoF3 chemical has been developed in order to find an isotopic anomaly by high precision in precipitated water.
Chapter 1 dedicated to an Introduction, history and application of isotopes. Fractionation of isotope in terrestrial atmosphere is generally through the process of mass dependent, so that 17O enrichment becomes about half of 18O enrichment relative to 16O. Therefore as a result, δ17O and δ18O in terrestrial materials plot along a line with a mass-dependent slope of about 0.52. But the discovery of MIF in meteorites and ozone shows the equal lowering of δ17O and δ18O and provide a slope that nearly equal to 1. In this chapter, various application of MIF has been given in detail.
Chapter 2 describes the development of an online system by using CoF3 chemical. The major drawback to obtain high precision through an online continuous flow method is sample signal variation and therefore, precision. Various tests were performed with reactor and system line to obtain the high precision. This chapter describe in detail about our approach to obtain the high precision though continuous flow method.
Last three decades variations in the triple oxygen isotope of free tropospheric precipitated water is part of chapter 3. CO2 - equilibrium method was applied for the last three decades sample measurements. Triplicate of sample were measured for better precision. Trend in water oxygen isotopes, temperature and relative humidity has been discussed in detail in this chapter. Chapter 4 dedicated to the last three decades pH measurements of free tropospheric precipitated water and its relation with low altitude stations. Relation with temperature, air pressure and relative humidity has been also discussed. Variation in pH in both altitude and very low pH value observed at the high altitude stations during large volcanic eruption has been discussed in detail in this chapter.
In 2003, Europe had experience of very dry and hot weather mainly due to the well-known heat wave event. Chapter 5 describes the variation in the triple oxygen isotope of precipitated water during 2003 heat wave event. Sample measurements were performed from seven different stations in Switzerland. Relations with meteorological parameters and variation with different altitude have been discussed here in detail.
Chapter 6 is dedicated to understaning the five station’s pH variation in the last four decades. Different stations were selected along transect with varying altitude. Monthly, seasonal and annual trend were discussed in detail here. In addition, moving average of all station was performed to find the seasonal variations. Interestingly, relation between pH and relative humidity has been found which has been discussed in detail in this chapter.
In chapter 7, last three decades ozone relationship with triple oxygen isotopes, pH and with meteorological parameters have been discussed. Monthly, seasonal and annual variations have been discussed in detail. Further, variation in all parameters during large volcanic eruption and during 2003 heat wave event also has been discussed. A brief description about the radiocarbon measurements at Jungfraujoch has been included in this chapter.
In chapter 8, a brief introduction about my Ph.D experience from non-scientific perspective part has been mentioned. Last three decades triple oxygen isotope datas of free tropospheric water including seven different station’s triple oxygen isotope data of precipitated waters from 2002-2004 has been provided in appendix. In addition to all of these, pH of precipitated water of seven different station is also available in appendix.

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