Poster Presentation Australasian Groundwater Conference 2017

Factors affecting dissolved organic carbon in coastal groundwater systems (#56)

Liza McDonough 1 2 , Denis O'Carroll 2 3 , Martin Andersen 2 3 , Karina Meredith 4 , Helen Rutlidge 2 , Phetdala Oudone 1 2 , Chris Marjo 5 , Andy Baker 1 2
  1. Department of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
  2. Connected Waters Initiative Research Centre, Sydney, NSW, Australia
  3. School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, Australia
  4. Australian Nuclear Science and Technology Organisation, Sydney, NSW, Australia
  5. Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW, Australia

Balancing the terrestrial global carbon budget has proven to be a significant challenge. Whilst the movement of carbon in the atmosphere and riverine waters has been extensively studied, the potential for organic carbon to desorb/adsorb from mineral surfaces and act as a groundwater organic carbon source/sink, is poorly understood.

To investigate the biodegradable component of groundwater dissolved organic carbon (DOC), groundwater samples were collected from six wells located on Rottnest Island, WA. Wells were selected to cover a range of DOC ages and concentrations in a carbonate aquifer. Water quality parameters such as pH, electrical conductivity, temperature, dissolved oxygen were measured in the field. Samples were analysed for their biodegradable DOC content using spectrofluorometric techniques at set intervals within a 28 day period.

Further to this, we examined the conditions and processes affecting DOC at a coastal wetland in Anna Bay, NSW. Four multilevel samplers (MLS’s) were installed in a transect with 1m spacing, with a distance of up to 3 m from the wetland edge. Two samples were taken from each MLS and analysed for DOC, dissolved inorganic carbon (DIC), anions and cations using LC-OCD, spectrofluorometry, UV-Vis and FIA techniques.

This research forms part of an ongoing project which will assist in identifying the factors affecting the mobilisation, transport and removal of DOC in uncontaminated groundwater. By quantifying the processes, we can then determine whether the groundwater is a carbon source or sink. Importantly, this information will help guide policy and identify the need to include groundwater resources as part of the carbon economy. 

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