​Marine and Environmental Geochemistry

  • Marine Geochemistry

Marine Geochemistry studies all processes that influence the chemistry in the water. The chemical cycles in the oceans are closely related to processes in the atmosphere and terrestrial systems as well as to biological, and recently anthropogenic, activity. Marine Geochemistry also studies the sediments, including the pore waters as well as the abiotic and biotic processes that take place within the sediment. Currently our research at Stellenbosch University focuses on macro-nutrient (e.g., N, P, Si) and trace metal cycling in the modern ocean (e.g., Fe, Mg, Zn, Cd, Co, Cu), interactions with biological organisms (especially with microbes and algae), and impact of atmospheric deposition (dust). We currently focus on the Atlantic sector of the Southern/Antarctic Ocean and the west coast of southern Africa. 

contact(s): Prof. Roychoudhury (roy at sun.ac.za) or Dr. Susanne Fietz (sfietz at sun.ac.za)

facebook: Environmental Geochemistry at Stellenbosch University

Blog: https://southernoceanfe.wordpress.com

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Overview of ocean-land-atmosphere-biosphere interactions studied at Stellenbosch University, Earth Sciences

SA Algulhas II in Antarctic ice
Most of our marine research projects sampling and experiments are conducted on board SA's flagship, the research vessel/icebreaker SA Agulhas II 

  • Geochemical proxies for paleo-climate reconstructions

Climate and the environment are ever-changing, driving human activity in the past and being altered by human behaviour in the present and future. Understanding the past is crucial for predicting future climate scenarios. Instrumental analysis is limited to a few centuries, but sediments, peats and speleothems offer a window into the climate of the past. There is no means of directly measuring the past air or water temperature, or soil pH, or ocean acidity etc. The reconstructions are thus based on microfossils, isotopes, and biomarkers preserved over millions of years. At Stellenbosch University, Earth Sciences, we mainly focus on molecular biomarkers, organic compounds derived from microbes that provide clues about regional temperature variability, environmental forcings (e.g., dust deposition) and ecosystem functioning (e.g., algal and microbial community).

contact(s): Dr. Susanne Fietz (sfietz at sun.ac.za) or Prof. Roychoudhury (roy at sun.ac.za)

facebook: Environmental Geochemistry at Stellenbosch University

history book.gif(left) A sediment core is just like a history book. Cutting section by section, it provides clues to the past that we can use to understand the present and project the future.

(below) Examples of sediment core sections from the Pacific Southern Ocean: a) laminated diatom ooze, b) Nannofosil ooze

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(below) coring long piston cores in a lake and at sea


  • Isotope Hydrology

Isotopes provide unparalleled means of understanding the origins and movement of water through the meteorological cycle and the mechanisms and pathways of transfer into both the deep and shallow groundwater system.  Through this work I have been exploring the use of both traditional stable isotopes (O, H, and C) and radioactive isotopes (Tritium, C14), as well as more novel isotope tracers including stable isotopes of magnesium, boron, lithium and strontium, and radioactive isotopes of radon, radium, chlorine, iodine and krypton. This work is focussed on groundwater systems in the Naukluft Mountains, Namibia, the Buffels River in the northern Cape and the Verlorenvlei catchment in the Western Cape. The work is conducted in collaboration with Prof Torsten Vennemann (Lausanne University, Switzerland), Prof Chris Harris (University of Cape Town), Dr Petrus le Roux (University of Cape Town), Prof Keith Fifield (Australian National University).

contact: Dr Jodie Miller, jmiller at sun.ac.za

  • Groundwater and salinization in semi-arid and arid environments

Dry land salinity is a serious problem throughout arid and semi-arid regions of the world and leads to three main problems including loss of arable land, a decline in the quality of domestic water supplies and negative impacts on the natural ecology. Salinity studies are often focussed on salinization of surface or shallow groundwater systems. However, the interaction of shallow and deep groundwater systems can lead to salinization in deep aquifers and impact on potable groundwater reserves for future generations.  My work focusses on understanding the linkages between the meteorological system, the surface water system and the groundwater systems to delineate mechanisms and timescales of salinization with a view to developing effective management strategies. The work is conducted in conjunction with Dr Cathy Clarke, Dept Soil Science at Stellenbosch, Dr Willem de Clerqc from the Stellenbosch Water Institute, Prof Benjamin Mapani at the University of Namibia, Prof Torsten Vennemann at Lausanne University in Switzerland and Dr Randy Stotler at Kansas University in the USA. Field areas are focussed around the west coast of Southern Africa.

contact: Dr Jodie Miller, jmiller at sun.ac.za