A comparative study of the total mercury determination in highly contaminated soils by AAS and RNAA methods

Sysalová, J.

High total mercury (T-Hg) contents in soils, up to 25 mg kg−1, were determined by two independent methods: a one-purpose atomic absorption spectrometer AMA-254 (Advanced Mercury Analyser) with direct solid sampling, and radiochemical neutron activation analysis (RNAA), using sample masses of 10 mg to 25 mg and about 150 mg, respectively. An excellent agreement between results of both methods was obtained. For quality control (QC) purposes, NIST SRM 2711 Montana Soil and NIST SRM 2711a were analysed by both methods using the above sample masses. The results obtained were compared with the NIST certified values within the uncertainty margins, thus proving the accuracy of the procedures employed. It has been found that the cryogenic grinding used provided sufficiently representative and homogeneous samples. A test in which HgS was analysed by RNAA showed that even mercury present in sulfide form would be fully recovered using the procedures employed. For contents of T-Hg above the upper limit of the AMA-254 working range (500 ng), samples were firstly diluted with sea sand in the ratio 1:10 and homogenised well to get RSD below 5%. The dilution procedure was verified using the certified reference material ERM-CC580 Estuarine Sediment.

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