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FTIR and XRD analysis of soil on Plitvice lakes area

The Plitvice Lakes National Park is located in the northwestern part of the Dinaric Karst in central Croatia. Hydrological system of 16 cascading lakes separated by tufa barriers and waterfalls covers about 1 % of the total surface area of the park. The Plitvice Lakes catchment is almost entirely within the boundaries of the National Park. The Plitvice Lakes National Park is a karst environment composed of Upper Triassic to Upper Cretaceous carbonate rocks (limestones and dolomites). Sediments present in this area are deposited during the Quaternary period. Unique geomorphological, hydrological, biogeochemical and biological phenomenon of the Plitvice Lakes attracts around 1 million visitors a year making this area very susceptible to anthropogenic influence. This area was added to UNESCO World Heritage list in 1979. Soils in the Plitvice Lakes area are classified as automorphic soil. Their main characteristic is wetting through precipitation only with no additional wetting. The dominant type of soil is calcocambisol or brown limestone soil (soil developed on limestones and dolomites). Along with the calcocambisol, there are also rendezines, calkomelanosols, luvisol and red soils (terra rosa). During May 2017, 10 samples of soil, peat and stream sediment were collected in Plitvice Lakes catchment and partly in the assumed zone of influence. After drying and milling, X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR) analysis of samples was performed. XRD analysis showed predominance of low-quartz, which was found in all samples, most often as dominant phase. Dolomite was found in half of the samples, almost always as a significant phase while calcite was dominant phase in one of the samples. In most of the samples members of the feldspars and chlorites groups, as well as muscovite were present as minor phases. The solid soil phase is a mixture of organic substances and minerals and makes up 30 to 60 % of the total soil content, the rest being air, water and living organisms. Unlike organic matter, minerals have smaller absorption bands of greater intensity. The intensity and position of the absorption bands depends on the chemical composition and origin of clays, especially the presence of impurities. The doublet band in the range 1008-1032 cm-1 corresponds is due to the Si-O-Al and Si-O-Si stretching in aluminosilicate minerals. The 1090 cm-1 band is due to normal-to-the-plane stretching of Si-O-Si. The obtained results, with fewer exceptions, are well matched with the absorption peak values of silicates and carbonates mentioned in the literature and the available FTIR spectrum databases. The organic matter, depending on the type of soil, makes on average 2-10 % of the solid phase content of the soil. The absorption bands in the range of 2800-3000 cm-1 due to the organic matter are visible in spectra of all samples.

Plitvice Lakes, soil, Fourier Transform Infrared spectroscopy, X-ray diffraction

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