Mercury fractionation in soil and sediment samples using thermo-desorption method.

Mercury is one of the most hazardous elements. Its transformation and transport in the environment strongly depend on its chemical form. The information about Hg form is also important for understanding the bioavailability as well as toxicity of this element. There are many methods for Hg speciation but most of them are expensive and time consuming. Therefore the aim of this research was to develop a simple thermo-desorption method for mercury fractionation in soil and sediment samples using a direct mercury analyser. The DMA-80 direct mercury analyser (Milestone, Italy) was chosen for this purpose and Hg species were characterised by the temperature range at which they were released. Thirteen synthetic standard materials as well as "natural" standards for a humus-like substance and methyl mercury were used in this work. The method was tested on a certified reference material as well as on natural samples: soil, beach sand and marine sediment. The obtained results show that the temperature fractionation, in spite of some limitations, could be considered as a screening method for the evaluation of the percentage contribution of certain groups of Hg compounds with similar properties in solid samples. This method could be applied for solid samples with low, environmental Hg concentration. The result obtained by this four-step fractionation could be comparable with different research, conducted using other mercury analysers.