Biogeochemical interrelations between the Çayırhan oil shales and some plants growing on them (Turkey)

Authors: BERNA YAVUZ PEHLİVANLI, ŞÜKRÜ KOÇ, ESRA ERGİN, ALİ SARI, LEYLA AÇIK, MECİT VURAL

Abstract: Oil shales are exposed in wide areas around the town of Çayırhan (Beypazarı-Ankara). It is known that some elements are enriched in oil shales and similar organic-material rich rocks. The purpose of this study was to understand the possible relations between the element abundances found at the Çayırhan oil shales (ÇOS) and those of some plant types growing on these rocks. The results of chemical analysis of selected plants (8 species) were compared with each other and with element abundances from the ÇOS. The plant types examined were divided into 2 groups with respect to enrichment factors. The first group contained 6 plant species: Eryngium campestre L. var. virens Link, Echinophora tournefortii Jaub. & Spach, Sideritis gulendamiae H.Duman & Karavel., Euphorbia macroclada Boiss., Reichardia glauca V.A.Matthews, and Centaurea virgata Lam. In this group of plant types, almost all of the same elements (Na, Si, V, Cr, Rb, Y, Zr, Mo, Sn, Sb, Tl, Bi, Th, and U) were found to be enriched. The second group was represented by Echinops pungens Trautv. var. pungens and Reseda lutea L. var. lutea. In these plants, only 6 elements (U, Zr, Si, V, Cr, and As) were enriched. Some elements (e.g., Si, V, Rb, Y, Cr, Zr, Mo, Sb, Bi, and U) were enriched in both groups. Among these 10 elements, Si, Cr, Zr, and U showed enrichment in all plant species. Considering the enrichments of world oil shale averages, all of the major elements and the trace elements of Co, Ni, Cu, As, Rb, Sr, Zr, Mo, Cd, Ba, Pb, and U were found to be enriched in the ÇOS to varying extents. The data indicate that element enrichments in the plants are not related to the enrichments in rocks. Out of several elements enriched in the ÇOS, only 6 of them (Si, V, Cr, Zr, U, and Mo) showed enrichment in all of the studied plants. Although major elements Mg, P, S, K, Ca, Fe, and Mn and trace elements Ni, Cu, Zn, Sr, Ba, and Pb were enriched in the ÇOS, they were not seen to be enriched in any of the plants. The elements Tl, Sb, Rb, and Na, not enriched in world oil shale averages, were determined to be enriched in the first group of plants. Results reveal that, in addition to rock geochemistry, biologic factors are still more dominant behind the observed element accumulations in plants.

Keywords: Çayırhan oil shales, major element contents, trace element contents, biogeochemistry, plants

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