Quantification and speciation of mercury in streams and rivers sediment samples from Paracatu, MG, Brazil, using a direct mercury analyzer®

This paper describes the application of a method for the direct speciation of Hg in sediment samples by thermal desorption using a Direct Mercury Analyzer®. The different thermal behavior of the Hg species allowed direct chemical speciation by DMA. The set of temperature steps was as follows: 50 °C, 100 °C, 150 °C, 200 °C, 250 °C, 300 °C, 400 °C, 500 °C, 600 °C and 700 °C. Sediment samples presented total Hg concentrations varying over a range of 36 to 1996 μg·kg−1, with 78% of the samples being over of the TEL (threshold effect level). According to the speciation analysis, a prevalence of oxidized Hg was observed. This method was efficient, simple and adequate for determining the Hg speciation in sediment samples. The great advantage is that the method does not require pretreatment of the samples, and it is applicable to homogeneous solid samples.