Microwave-assisted determination of total mercury and methylmercury in sediment and porewater

Abstract

Existing methods for total mercury and methylmercury determination in sediment and porewaters were improved by applying open microwave heating for extraction of Hg species from the sample and decomposition of MeHg prior to detection as Hg(II) by CV AFS. It was shown that nitric acid can quantitatively leach Hg from sediment, already at a low microwave power (30 W, 5 min). Methylmercury can be quantitatively leached from sediment by dilute sulphuric acid (1 mol/L) at a power of 60 W during 5 minutes, without being decomposed. So obtained extract can be further distilled with a reduced possibility for artefactual MeHg formation, as it contains much lower levels of inorganic Hg, compared to the original sediment. Microwave-assisted BrCl oxidation was shown to be more effective for decomposition of MeHg and stable organomercury complexes in water solutions (sediment distillate and porewater), as compared with BrCl oxidation at room-temperature. Therefore, the application of low-power microwave digestion can significantly improve determination of Hg species in sediment and porewater, both in terms of time and efficiency.