IMPACT OF POLLUTION ON THE CLAY MINERALOGICAL COMPOSITION OF SOME SOILS FROM ZLATNA AREA (ROMANIA)

Abstract

Zlatna area is a high polluted zone with heavy metals due to industrial activity (extraction and processing of non-ferrous area). In spite of the fact that industrial activity was stoped for 2-3 years, the effect of pollution are still obvious. The aim of this paper is to make evident some aspects concerning the impact of pollution on the mineralogical composition of the clay fraction (below 2µ) from some soils belonging to dystric cambisol and luvisol type. From the chemical point of view, the effect of pollution is the acidifiation and depletion of bases, reflected by the decrease of values of indices which express soil reaction (pH) and soil exchange properties, especially in the surface horizon. From mineralogical point of view, the acidifiation determines a strong alteration of primary minerals (micas and feldspars) and just of secondary minerals (illite), evolution beeing towards hydroxy interlayered minerals (intergrade) and kaolinite. As result of this alteration the content of kaolinite increases, achiving a double content in the surface horizon of some polluted soils. Sometimes kaolinite becomes the dominant mineral in the clay fraction of some strong polluted soil.