Caves and palaeoclimate
Caves provide unique windows into the functioning of surface ecosystems and through speleothem deposition, record information on a wide range of processes, including infiltration dynamics, vegetation assemblages, soil carbon storage, air temperature, and much more besides. Our research focuses on a subset of chemical interactions affecting trace elements: the interaction of colloids (particles between 1 and 1000 nm), natural organic ligands and complexed (chemically-bound) metals, in order to develop speleothem proxies of past environmental change. This work benefits from collaborations with European research organisations through project QUEST.
Natural ligands and nanoparticles in soil and natural waters play a central role in controlling the mobility and bioavailability of metals and metalloids. Past research projects have included studies of the interaction of phosphorus with iron nanoparticles in lake systems and their influence over P bioavailability under variable redox conditions, and alum dosing of lakes for P-sequestration.
DGT (diffusive gradients in thin films) is a passive sampling technique which can be deployed for the specific measurement of dissolved species in water. Our research employs DGT to answer a range of questions relating to the chemical form (speciation) and biogeochemical availability of metals, nutrients and contaminants in natural and polluted aquatic environments.
Soil and sediment systems
The accumulation and transfer of metals and nutrient species within soils is controlled to a large extent by interactions at the soil-water-root interface. Research in our group involves the study of the fate, mobility and transformation of toxic metals (e.g. Cd), pollutants and nutrients in soils and sediments in collaboration with other New Zealand research institutes.
Stable and radio isotopes are essential tools in the study of Earth and environmental science. We use O and C isotope measurements as well as more exotic isotopes (e.g. δ114Cd, δ65Cu) to explore modern and ancient processes. This work benefits from collaborations with world-class isotope geochemistry labs (Melbourne, Otago, Woolongong).
Analytical techniques used in WEG research include:
- Diffusive gradients in thin films (DGT)
- Flow field-flow fractionation (Fl-FFF), size exclusion (SE), normal and reverse-phase high performace liquid chromatography (HPLC)
- Fluorescence spectroscopy (3D excitation emission matrices), total organic carbon (TOC) analysis, Gas Chromatography Mass Spectrometry (GC-MS)
- Inductively coupled plasma mass spectrometry (ICPMS), including laser-ablation (LA-ICPMS)
- Stable isotope mass spectrometry (IRMS and CRDS)