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1.4 CHEMICAL SCIENCES
Surface sediment samples were collected at sites within the Rockall Through at water depth ranges from 700 – 2774 metres. The study area was predefined by the availability of samples. Samples were collected by the British Geological Survey during their gravity core survey undertaken in 1998. Methods were optimised and validated for lead, cadmium, chromium, copper, nickel, zinc, lithium and aluminium using atomic absorption spectroscopy following total digestion, and for mercury, using cold vapour atomic fluorescence spectroscopy following partial digestion. The measured metal concentration were normalised to Li to compensate for the influence of natural variability in the concentration of contaminants in sediments. The mean concentration (range in brackets) of trace metals detected in these samples were 0.07 (00.3 – 0.35)mg kg-1 Hg, 8.51 (3.43 – 16.2) mg kg-1 Pb, 0.25 (0.03 – 2.57) mg kg-1 Cd,28.7 (15.1 – 54.2) mg kg-1 Cr, 17.1 (5.89 – 42.7) mg kg-1 Cu, 18.3 (8.83 – 38.9) mg kg-1 Ni 41.4 (18.0 – 149) mg kg-1 Zn, 19.7 (4.51 – 55.7) mg kg-1 Li and 2.70 (0.86 – 6.23) % Al, all of which fell within the provisional Ecotoxicological Assessment Criteria (EAC) values for metals in sediments, where available. Natural variations in concentrations of metals in sediments was modelled by linear regression using 95% confidence intervals. The concentration of lithium was used as an independent variable. The analytical quality assurance programme included the use of a number of Reference Materials (BCSS-1 obtained from the National Research Council of Canada and QTMO49MS obtained from QUASIMEME) to validate the accuracy and precision of the analytical methods developed and to provide ongoing quality control. Participation in QUASIMEME (Quality Assurance of Information in Marine Environmental Monitoring) an international proficiency-testing scheme also helped to underpin the analytical quality.
Tyrrell, L. (2005). The determination of environmentally important metals in marine sediments. Masters dissertation. Technological University Dublin. doi:10.21427/D70W4P