TRACE ELEMENTS IN ESTONIAN PEAT

摘要

Estonian peat is commonly used in home country and exported all over the world, therefore we need to know the chemical composition of peat and the concentration of trace elements in it. 684 peat samples from 64 mires were analysed, concentration of 16 trace elements and general characteristics (peat type, degree of humification, pH and ash content) were determined. Samples were taken from the whole section after every 0.5 m, in places 0.25 m. Atomic absorption method was used to determine the concentration of Cd, Cr, Cu, Mn, Ni, Pb and Zn (AASflame), Cd (AAS-ETA), and Hg (cold vapour method). Concentration of As, Co, Mo, Sr, Th, U and V was determined by X-ray fluorescence method. By genesis peatlands are divided into 25 peat districts. The setting of peat layer, its genesis and concentration of trace elements in the peat is presented by the above peat districts. The concentration of trace elements in peat is small: As-2.40,Cd-0.120,Co-0.50,Cr-3.1,Cu-4.4,Hg-0.050,Mn-35.1,Mo-1.2,Ni-3.7, Pb - 3.3, Sr-21.9, Zn-10.0, Th-0.47,U-1.27, V-3.8mg/kg and S -0.25%. Main binding mechanisms are: mechanical, biological, physical-chemical, physical, chemical. The high concentrations of trace elements are mostly related to the mires feeding from springs. The trace elements can reach the human organism in different ways: via the food chain, by inhaling, by drinking water. Results of statistical processing show that Co has the highest positive correlations with different elements and ash content. The high correlation coefficients have also As, Ni, Mo, ash content and pH. The influence of peat layer decreases in the following order: transitional mire - raised bog - fen. The smallest values of most trace elements were recorded in mires feeding from precipitation and the highest - in mires feeding from groundwater. The influence of peat type on the concentration of trace elements decreases from surface layer towards the base. The mineral component of peat was analysed as well. The scientific research shows that the concentration of trace elements is often higher in the bottom part of peat layer. The peat presently produced in Estonia is ecologically clean.