A State-or-the-Art Environmental Geochemistry Laboratory at HKU

Dr Thibodeau, Benoit   (Principal Investigator (PI))

24

2016-06-27

90000

A State-or-the-Art Environmental Geochemistry Laboratory at HKU

Climate Change, Environment, Geochemistry, Paleoceanography, Pollution, Stable isotopes

Earth Sciences,Environmental Studies and Science

Physical Sciences (P)

201602173003

Dr. Stephen S.F. Hui Trust Fund

2015

Completed

Geochemistry is a unique tool in environmental and earth sciences to track down processes through space and time. The new research group I co-founded on Paleoceanography and Geochemistry (http://web.hku.hk/~bthib/) aims to tackle environmental issues as nitrogen, heavy and trace metal pollution and global changes by using the most recent advance in geochemistry. One of the most impactful application in nitrogen geochemistry has been the denitrifiers method, where denitrifying bacteria are used to transform dissolved inorganic nitrogen to nitrous oxide that can be easily measured by isotope-ratio-spectrometry (Sigman et al., 2001, Casciotti et al., 2002). This technique can be coupled with a wet-oxidation method that is used to transform organic nitrogen to dissolved organic nitrogen and allow its isotopic measurement (Knapp et al., 2005; Thibodeau et al., 2013). The coupling of those methods allowed the development of a whole new array of nitrogen isotope measurement in material where it was not possible before, as hard corals and foraminifers, both of which form carbonates structure that incorporate too little organic matter to be measured with traditional methods (Staub et al., 2013). The overarching objective of this proposal is to build a state-of-the-art environmental geochemistry laboratory in Earth Sciences at HKU. This facility would be available to all earth sciences students, including the one from the environmental sciences major in which I teach and supervise final year and summer research projects. Having this facility at HKU will allow not only world-leading research to be performed at HKU, raising the international reputation of the university, but also it will give HKU students the opportunity to acquire cutting-edge analytical skills that are highly in demand in both earth and planetary sciences and environmental sciences. Thus, this proposal will be a contribution (that will be matched by the PI) toward the acquisition of an essential instrument to carry this research with the highest standard a Mars6 Microwave Reaction System, where we will oxidize dissolved organic nitrogen under controlled and monitored conditions in order to produce the most reliable data possible with today’s technology. This instrument will be used on a regular basis and will contribute to a large extent of the research carried within the Paleoceanography and Geochemistry Research Group. I will here focus on the two main applications of this machine, one is a project already partially funded by the HKU seed-grant program and the second one is now under review for the UGC-General Research Funds. However, due to the cost of this machine (usually around 300 000 HKD), it could not be included in any of these proposals. The first research program that will benefit from the acquisition of the Mars6 Microwave Reaction System is related to nitrogen cycling in coral reef around Hong Kong. The main goal of this project is to identify how nitrogen cycles between the different forms of dissolved nitrogen and how it is incorporated in coral reefs around Hong Kong. This project will provide basic knowledge about the N-cycle and its effect on coral reefs under Hong Kong human-impacted conditions and thus will lay down the premises for our future larger N-cycle-oriented projects. We aim to respectively quantify the importance of dissolved inorganic nitrogen and dissolved organic nitrogen in the coral nutrient consumption, for which we need to oxidize the organic nitrogen. The Mars6 Microwave Reaction System will allow us to routinely perform the oxidation with a much higher replicability than with the less reliable traditional method of autoclaving at a much higher rate because of the large capacity of the Mars6. The second research program that will benefit from the acquisition of the Mars6 Microwave Reaction System is related to paleoceanography. Measuring the nitrogen isotope of the organic matter that is encapsulated within carbonates fossils, as corals or foraminifera is much more reliable compared to the traditional bulk method since it is now subject to diagenesis. It is thus a new, robust way to reconstruct surface water nitrate isotopic composition, which is controlled by the surface water stratification in the North Atlantic and the Nordic Seas (Straub et al., 2013, Thibodeau et al., in review). Since stratification in the Nordic Seas is thought to be directly linked to the convective mixing leading to deep water formation in this region, our investigation will have as an objective to estimate how stratification evolved through time and asses how the potential demise of Greenland- ice-sheet will affect the overturning circulation and global climate. Here, I propose to use the Trust fund as a large contribution toward the acquisition of the Mars6 Microwave Reaction System. As I managed to negotiated an extremely good price for the quotation provided (around 200 000 HKD) I am ready to provide 100 000 HKD from my start-up fund in order to match the Trust fund and acquire the instrument.