WeO-07

A COMPARISON OF ICPAES AND ICPMS FOR THE DETECTION OF MERCURY IN SEDIMENTS FROM THE GREAT BARRIER REEF LAGOON

G. Stewart Walker*¶#, Gregg J. Brunskill¶ and Michael J. Ridd#

*Cooperative Research Centre for the Ecologically Sustainable Development of the Great Barrier Reef, Townsville, Queensland 4811

¶Australian Institute of Marine Science, PMB 3, Townsville, Queensland 4810

#Advanced Analytical Centre, James Cook University of North Queensland, Townsville, Queensland 4811

Sediment cores of up to 4 metres in depth have been collected from various locations around the coast of North Queensland. The location of the sites has been chosen on consideration of the potential for natural and anthropogenic input into the Great Barrier Reef Lagoon. Six possible sources of mercury in the sediments have been identified :-

1) Natural abundance
2) Natural events such as volcanic eruptions or thermal up welling
3) Mining - mercury amalgamation was used in the decades before 1900
4) Agricultural runoff - a mercury based fungicide is used extensively in sugar plantations
5) Shipwrecks - with mercury as a cargo leading to localized point source input
6) A combination of factors such as burning fossil fuel or paint pigments [1]

Methodology for the digestion of sediment samples has been investigated. Digested samples were analysed by a Varian CGA-76 Cold Vapour Generator (CVG) coupled to a Varian Liberty 220 Inductively Coupled Plasma Atomic Emission Spectrometer (ICPAES) by a published method [2]. An appropriate method was developed for analysis of samples by CVG coupled to a Varian UltraMass Inductively Coupled Plasma Mass Spectrometer (ICPMS).

A comparison of results from a series of standard solutions run on both instruments will be presented. Limits of detection in solutions of standard Mercury Chloride was found to be around 10ppt for the ICPMS. Results from sediment digests will be presented. Limits of detection of mercury in digested solution were found to be 1ppb for ICPAES and 0.05ppb for ICPMS. The method and factors effecting precision and background level will be discussed.

Combined results indicate an anomalous concentration of mercury in certain levels of sediment from an area in the Great Barrier Reef Lagoon. The data will be presented and the results discussed.

  1. Walker, G.S., Project proposal submitted to Cooperative Research Centre for the Ecologically Sustainable Development of the Great Barrier Reef, June 1995.
  2. K.A. Elrick and A.J. Horowitz, Analysis of Rocks and Sediments for Mercury by Wet Digestion and Flameless Cold Vapour Atomic Absorption, Report number AA-72, Varian,1987.