Marine and Environmental 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
Overview of ocean-land-atmosphere-biosphere interactions studied at Stellenbosch University, Earth Sciences
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
(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
(below) coring long piston cores in a lake and at sea
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
