Metal speciation in a dynamic intermittent hypoxic marine environment (Loch Etive, Scotland)


  • Supervisors: Dr. Pascal Salaun, University of Liverpool
    Prof. Jonathan Sharples, University of Liverpool


  • External Supervisors: Prof. Mark Innall, SAMS,
    Tim Brand, SAMS
  • Contact:

    Pascal Salaun, University of Liverpool, Salaun@liv.ac.uk

  • CASE Partner:

Application deadline: 10 January 2020

Introduction:

Deoxygenation of the oceans is an on-going process, mostly due to increased ocean temperatures. A recent review suggested that the oceans have lost 2% of the oxygen content since pre-industrial times. In coastal waters, this loss may be more important , mostly through processes of eutrophication. This oxygen removal is very much site dependent and depends on numerous parameters such the hydrography, bathymetry, tidal range, nutrient inputs, primary production and many more. When oxygen is removed from the water column and/or sediment, the redox potential of the water decreases and chemical conditions are altered. The most common example is the reduction of manganese oxide to manganese ions in surficial sediments; Mn2+ diffuse back to the water column before precipitating again1,2. Manganese being a known strong adsorbent, this precipitation is likely to be associated with the removal of part of other metals, affecting their overall chemical distribution, cycling and bioavailability/toxicity to the phytoplankton community. 

Loch Etive is a sea loch on the West coast of Scotland where hypoxic conditions are regularly occurring2, making it a unique place in Western Europe. This deoxygenation is due to the long residence time of the water that undergoes significant bacterial remineralisation. In this project, we want to:

  • Determine the background levels of specific metals in Loch Etive (currently not known for many of them);
  • Determine their chemical speciation to get insights into how deoxygenation can affect their biogeochemical cycling.

Project Summary:

The core activities of this PhD project will consist of field sampling campaigns to collect samples followed by their analysis in laboratory conditions. Field campaigns will be achieved at various stages of deoxygenation during a full cycle (believed to last on average 16 months), from fully oxygenated to low oxygen conditions before a mixing event occurs.  Samples will be collected at different depths and stations, will be filtered as soon as convenient for dissolved (< 0.45 um and/or <0.2 um) and soluble (< 0.02 um) fractions. Usual parameters such as dissolved oxygen, salinity, turbidity and chlorophyll will be obtained along with other physical parameters (e.g. current, ADCP outputs). Metals to be analysed will be iron, manganese, copper, iron, arsenic, antimony, lead, cadmium, zinc and/or platinum. 

Trace metal concentrations and speciation will be determined by ICP-MS and by various electroanalytical techniques (e.g3,4). Determination of thiols5 and humic substances6, both known complexing agents for various metals, will be also determined by electroanalysis. 

This local and exciting project will suit someone that enjoys working in an analytical laboratory, who is well organised, independent and motivated. We are looking for a student with a scientific background in Oceanography, Environmental Sciences, Chemistry or a related area.

References:

(1) Statham, P. J.; Connelly, D. P.; German, C. R.; Brand, T.; Overnell, J. O.; Bulukin, E.; Millard, N.; McPhail, S.; Pebody, M.; Perrett, J.; Squire, M.; Stevenson, P.; Webb, A. Environmental Science & Technology 2005, 39, 9440-9445.

(2) Overnell, J.; Brand, T.; Bourgeois, W.; Statham, P. J. Estuarine Coastal and Shelf Science 2002, 55, 481-492.

(3) Bi, Z.; Salaun, P.; van den Berg, C. M. G. Marine Chemistry 2013, 151, 1-12.

(4) Gibbon-Walsh, K.; Salaun, P.; van den Berg, C. M. G. Journal of Physical Chemistry A 2012, 116, 6609-6620.

(5) Laglera, L. M.; Downes, J.; Tovar-Sanchez, A.; Monticelli, D. Anal. Chim. Acta 2014, 836, 24-33.

(6) Whitby, H.; van den Berg, C. M. G. Marine Chemistry 2015, 173, 282-290.

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