TRACE ELEMENT COMPOSITION OF AQUEOUS EXTRACTS OF SOME DIATOMITE AND LYDITE SAMPLES FROM KARELIA

Abstract

The relevance of the research consists in the necessity to obtain reliable information on microelemental composition of aqueous extracts of diatomite and lydite. Currently, diatomites are expected to be widely used in medical, pharmaceutical and food industries, but a detailed study of their composition has not been conducted. The main aim of the research is to investigate the trace element composition of aqueous extracts of several samples of diatomite and lydite using ICP MS analytic method. The objects: three samples of diatomite and two samples of lydite from Karelia (North-West of Russia). Methods: grinding samples of diatomite and lydite infused with deionized water at room conditions. Assays of aqueous extracts of the studied samples were centrifuged and analyzed by ICP MS after 1, 3 and 10 days. Results. The authors present the results of 54 chemical elements identification in water extracts of diatomite and lydite using ICP MS. In all water extracts Mg, Na, Ca, K and Al (up to several thousand µg/l) are the predominant elements. Extracts of diatomite samples have a more homogeneous composition. The most important elements were: P – 650, Fe – 1700 (sample no. 1) and Mn – up to 3300 (sample no. 3) µg/L. Concentrations in the range from 10 to 100 µg / l are typical for a number of elements (Li, B, Ti, Cr, Co, Ni, Cu, Zn, Sr, Y, Zr and Ba) of all diatomite samples. Extracts of diatomite samples no. 1 and 2 had a maximum concentration of light REE: Nd (up to 247 µg/l), Ce (up to 230 µg/l), La (up to 156 µg/l). Chemical composition of extracts of lydite was differed markedly, both among themselves and from diatomites. Acidic medium (pH 4,5–4,6) of an aqueous extract of the sample lydite no. 4 contributed to accumulation of a number of elements Sr, Mn, U and, especially, Be, Fe, Co, Ni, Cu, Zn, Y, Ba, Tl. At the same time, maximum concentrations of V, Mo, W, Zr, Hf were observed in the extract of sample no. 5 under slightly alkaline conditions (pH 7,4–7,5). We noted an excess of permissible limits of fishery water bodies for Al and Mn in all samples. The excess of the «normal» maximum permissible concentrations have also shown the transition elements (Fe, Co, Ni, Cu, Zn) in extracts of diatomite and sample lydite no. 4, as well as V and Mo in the sample lydite no. 5. The study of aqueous extracts of diatomite and lydites showed that diatomite and lydites under certain conditions can have a significant impact on composition of low-mineralized waters in the territory of Karelia. At the same time, the presence of useful elements for the plant growth (Mg, Ca, K, Cu, Zn, V, Mn, Sr, Y, Zr) gives the possibility of their use as a «soft» fertilizers (or additives to mineral fertilizers).

Keywords

• diatomite
• lydite
• trace element composition
• water extracts
• karelia
• paleoproterozoic
• holocene