RAISED BOG PEAT HUMIC ACID ELEMENTAL COMPOSITION: TRENDS OF CHANGES AND RELATED FACTORS

Peat deposits can be considered as archives of environmental changes and indicators of anthropogenic pollution. The character of element accumulation, the potential of metal ions to bind functional groups in the peat structure, the pH reaction, the presence of oxygen, the complexing compounds and inorganic ions are the main factors governing peat ability to accumulate major and trace elements. The aim of this paper has been to study the major and trace element accumulation in humic acids (HAs) in two well-characterized ombrotrophic peat profiles of Eipurs Bog and Dzelve Bog in Latvia and analyse factors affecting the element concentrations in HAs with reference to peat properties. The analysis of major elements (e.g., Ca, Fe, K, Mg, Na) and trace elements (e.g., As, Cd, Co, Cr, Cu, Ni, Pb, Se, Zn) was performed by total reflection X-ray fluorescence spectrometry. Thise c paper demonstrates that HAs are significant for several elements, however, they are not the dominant factor affecting the element accumulation. The concentration of trace elements in peat and in peat HAs depend not only on human-induced pollution (determining elevated concentrations of trace elements in upper layers of the bog). The study has revealed that for the accumulation of several toxic trace elements in peat (for instance, As, Pb and others) natural processes are of key importance.