Ultrasound assisted mercury extraction from soil and sediment

A method for mercury (Hg) determination in soil, river sediment and marine sediment without sample digestion is investigated. Mercury determination is performed by cold vapour atomic absorption spectrometry (CV-AAS) using a flow injection system. Mercury quantitatively leaches out from the investigated marine sediment into 30% (v/v) HNO3 assisted by ultrasonic irradiation (during 90-120 s) when sample particles size are less than or equal to 120 mum. Similar conditions can be applied for Hg determination in river sediment and soil, excepting the time of sonication which needs to be increased to 180 s and KCl is also added to the extraction medium. The presence of 0.15% (m/v) KCI in addition to 30% (v/v) HNO3 is seen to be effective for quantitative Hg leaching. The certified samples PACS-2 and MESS-3 (both marine sediment from NRCC), Buffalo River (NIST 8704), Montana Soil (NIST 2710) and the non-certified river sediment sample RS-3 were analysed. The attained results were well within the 95% confidence level of the certificate or close to information value. Samples were analysed using aqueous standard calibration. A characteristic mass of 25 pg, a LOD (3s) of 0.2 mug Hg l(-1) and a LOQ (10s) of 0.012 mug Hg g(-1) are typically attained. These are based on 800 mul of sample solution and 1.000 g of sample mass in 20 ml. The RSD of 10 consecutive runs of the sample is < 5%. The proposed method was finally applied for the determination of Hg in real samples of soil, river sediment and marine sediment. The same samples were also analysed using a digestion method giving similar results. (C) 2004 Elsevier B.V. All rights reserved.