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Environmental Geochemistry

The Environmental Geochemistry group conducts multidisciplinary research into biogeochemical processes, environmental change, and the fate of contaminants in the environment. 

Prof. Marc Humphries |  | Google Scholar

I enthusiastically lead a coherent and independent research program in multidisciplinary environmental geochemistry. My interests in geochemistry and environmental science are diverse, but focus primarily on the links between geochemistry, environmental processes and ecosystem functioning. I am particularly interested in the coastal environment, the geochemical processes that take place within wetland sediments, and how coastal systems respond to environmental change. I use a variety of geochemical techniques to understand how coastal systems function, how they changed in the past, and how they may respond to future anthropogenic impacts and climate change. I have worked on a variety of fascinating coastal and wetland systems across South Africa, Botswana, Tanzania, Madagascar and Australia.

Specific areas of interest include:

  • Geochemical and sedimentary processes in wetlands and coastal systems
  • Examining climate and palaeoenvironmental change using geochemical proxies
  • Contaminant bioaccumulation, ecotoxicology, and the use of novel sentinel species
  • Submarine groundwater discharge and the flow of nutrients, carbon and contaminants into the coastal ocean

Dr Letitia Pillay |  | Google Scholar

My research interests focus primarily on the concentration, behavior and potential remediation of contaminants (both organic and inorganic) in environmental ecosystems, with a particular focus on metal mobility and speciation in plants, sediment, water and to a more limited extent marine biota.

The bioavailability and speciation of metals in environmental and biological samples are key to understanding their toxicity and impact on living organisms. Understanding these parameters allows for assessments to be made on the impact and extent of pollutants on an ecosystem in both the short and long term.

Metal uptake by plants can be a useful tool to facilitate phytoremediation, a cleaner, greener technology for reducing pollutants in contaminated environments. Hyperaccumulator plants can take up elevated concentrations of metals from soils and can have a major impact on successful phytoremediation processes. My current research involves the identification of compounds responsible for hyperaccumulation (and accumulation) in plants and elucidating uptake mechanisms. This will allow for manipulation of uptake processes which in turn may enhance remediation or provide novel techniques for remediation.

Projects include:

  • Characterization of the chemical constituents in South African metal hyperaccumulators from the Asteraceae family
  • The effect of soil amendments on the rate and capacity of metal uptake in both hyperaccumulator and accumulator species
  • Nanomaterials in water remediation
  • Metal speciation (arsenic and mercury) in contaminated environments

Recent publications

Gomes, M., Ralph, T., Helander, C., Humphries, M., 2023. Landscape connectivity dynamics of the transboundary Mara River catchment, East Africa, and implications for river and wetland response in a globally important conservation region. Catena 228, 107148

Gomes, M., Ralph, T., Humphries, M. 2023. Contemporary channel adjustment and geomorphic sensitivity of the lower Mara River and its floodplain wetlands, Tanzania. Geomorphology 425, 108583

Fietz, S., Baker, A., Miller, C.S., Naafs, D.A., Peterse, F., Finch, J., Humphries, M., Schefuß, E., Roychoudhurya, A.N., Routh, J. 2023. Terrestrial temperature evolution of southern Africa during the late Pleistocene and Holocene: Evidence from the Mfabeni Peatland. Quaternary Science Reviews 299, 107870

Humphries, M.S., Benitez-Nelson, N., Combrink, X., 2022. Trace metal accumulation in eggs of wild Nile crocodiles (Crocodylus niloticus) from Lake St Lucia, South Africa: implications for biomonitoring in a global biodiversity hotspot. Archives of Environmental Contamination and Toxicology 83, 214–225.

Mehlhorn, P., Humphries, M., Gensel, J., Buah-Kwofie, A. Tyohemba, R.L., Haberzettl, T., 2023. Organochlorine pesticide contamination in sediments from Richards Bay, South Africa: spatial trends and ecotoxicological risks. Environmental Science and Pollution Research 30, 2247–225

Humphries, M., McCarthy, T.S., 2022. Chemical sedimentation as a driver of habitat diversity in dryland wetlands. Wetlands Ecology and Management 30, 675–694.

Humphries, M., Myburgh, J., Campbell, R., Combrink, X., 2022. High lead exposure and clinical signs of toxicosis in wild Nile crocodiles (Crocodylus niloticus) from a World Heritage Site: Lake St Lucia estuarine system, South Africa. Chemosphere 303, 134977.

Gensel, J., Humphries, M.S., Zabel, M., Sebag, D., Hahn, A., Schefuß, E., 2022. Origin, transport and retention of fluvial sedimentary organic matter in the Mkhuze wetland system, South Africa’s largest freshwater wetland. Biogeosciences 19, 2881–2902.

Dladla, N., Green, A., Humphries, M., Cooper, A., Godfrey, M., Wright, I., 2022. Back-barrier evolution and along-strike variations in infilling of the Kosi Bay lake system, South Africa. Estuarine, Coastal and Shelf Science 272, 107877.

Green, A., Humphries, M., Cooper, A., Strachan, K., Gomes, M., Dladla, N., 2022. The Holocene evolution of Lake St Lucia, Africa’s largest estuary: geological implications for contemporary management. Estuarine, Coastal and Shelf Science 266, 107745.

Tyohemba, R.L., Humphries, M.S., Schleyer, M.H., Porter, S.N., 2022. Accumulation of commonly used agricultural herbicides in coral reef organisms from iSimangaliso Wetland Park, South Africa. Environmental Pollution 294, 118665

Tyohemba, R.L., Pillay, L., Humphries, M.S., 2021. Bioaccumulation of current-use herbicides in fish from a global biodiversity hotspot: Lake St Lucia, South Africa. Chemosphere 284, 131407.

Chetty, S., Pillay, L., Humphries, M.S., 2021. Gold mining’s toxic legacy: pollutant transport and accumulation in the Klip River catchment, Johannesburg. South African Journal of Science 117(7/8), Art. #8668.