Mercury is present in the marine environment through both natural sources, such as volcanic eruptions, and anthropogenic sources, such as the atmospheric deposition of combusted fossil fuels. Mercury exists in a variety of different forms, and it is methylmercury which is of the greatest concern in the marine environment due to its toxicity and biomagnification potential in marine food webs.
Numerous techniques exist to measure the speciation and concentration of mercury in environmental samples. The development and application of accurate measurement techniques is important in the assessment and monitoring of mercury pollution in the marine environment.
At the Australian Nuclear Science Technology Organisation (ANSTO) we apply radioisotope tracer techniques to understand the movement and fate of contaminants like mercury in simulated marine environments under controlled conditions. We have produced mercury-203 (203Hg) at ANSTO via neutron irradiation. This radioisotope emits gamma radiation which is easily detectable on the Hidex instrument (AMG, Automatic Gamma Counter). We are using 203Hg to investigate rates of mercury methylation, and potentially demethylation, in Australian marine sediments. As such, we have adapted and applied an extraction technique to measure inorganic and organic 203Hg in environmental samples. The benefits of using this technique include reduced processing time and increased sample throughput. The use of radioisotopes also allows us to investigate mercury pathways under environmentally relevant concentrations, due to the high specific activity (I.e., high activity to low Hg concentration) making low concentrations (i.e., <ppb) of Hg easily detectable.
We will present the challenges and steps taken to adapt and validate this extraction protocol to determine mercury speciation in marine sediments and how we have applied this protocol so far.