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A b s t r a c t. The comparison of particle size distributions measured by sedimentation methods and laser diffraction shows the underestimation of the fine (clay) fraction. This is attributed mainly to the shape of clay particles being different than spherical. The objective of this study was to demonstrate differences in the results of particle size distributions of soils determined with the method of laser diffraction using two different dispersion units of the Malvern Mastersizer 2000.K e y w o r d s: particle size distributions, sedimentation, laser diffraction, Mastersizer 2000 INTRODUCTIONParticle size distribution (PSD) of soils is one of the fundamental parameters permamently used in soil science (Brzeziñska et al., 2011; Joó et al., 2010; Nosalewicz and Nosalewicz, 2011; S³awiñski et al., 2011; Tóth et al., 2009). More and more often the determinations of that parameter is made with the use of the method of laser diffraction (Blott and Pye, 2006; Pye and Blott, 2004; Sperazza et al., 2004). The method consists in measuring the intensity of laser light scattered on the particles measured. The intensity of scattered light depends on the size of the particles in the measurement system. The smaller the particle, the greater the angle at which the light is scattered/refracted.The method of laser diffraction has been compared many times with the earlier methods of PSD determinationthe sedimentation methods (Arriaga et al., 2006; Beuselinck et al., 1998; Ry¿ak and Bieganowski, 2010; Tauber et al., 2008). In certain of such reports one can encounter information about underestimation of the fine (clay) fraction content in measurements performed with the method of laser diffraction as compared to the sedimentation methods (Beuselinck et al., 1998; Eshel et al., 2004; Konert and Vanderberghe, 1997). The underestimation of the clay fraction content is attributed mainly to the shape of clay particles being different than spherical (Konert and Vendenberghe, 1997). Those authors pointed out that the divergent results might be also related to problems with the selection of optical parameters for the clay fraction (Eshel et al., 2004) or with the limited measurement range, especially of the older types of apparatus (Beuselinck et al., 1998).Apart from the above potential causes of the underestimated clay content in soils studied careful analysis of the literature on the determination of PSD with the method of laser diffraction leads also to further conclusions. One of the more important reasons for the lack of comparability of results lies in the use of laser diffractometers of various manufacturers or various models (generations) of equipment of this type from a single manufacturer. Another problem is the frequent lack of information -in research publications -on the type/model of apparatus used and/or on its equipment.The objective of this study was to demonstrate differences in the results of PSD of soils determined with the method of laser diffraction using two different dispersion units of the Malvern Masters...

Radiocarbon-dated spring-fed fen deposits from the Komarów site (Volhynia Upland, SE Poland) with its multi-proxy data (macrofossils, molluscs, geochemistry, pollen, stable isotopes of oxygen and carbon) enable us (1) to distinguish four main stages of fen evolution, which reflected a distinct variability of water supply conditions and (2) to reconstruct the Holocene humidity–temperature changes. The beginning of peat–tufa deposition took place in a Boreal phase, after a significant cool fluctuation of climate occurring ca. 9.4 ka cal. BP. We suggest that climate was the most important factor conditioning the development of the spring-fed fen. Permafrost degradation, and then wet periods, intensified the activity of ascending springs. The impact of humans was possible since the Neolithic period and increased during the Middle Ages: therefore, the anthropogenic influence could have partially overlapped with the regional tendencies of climate changes. Autogenic development of deposit succession in the studied fen was definitely conditioned by hydrological changes induced by climate. Based on the multi-proxy data, 12 cold events of different ranks were identified. They are also recorded in other Polish and European sites. A record of distinct variability of depositional conditions at ca. 9.4, 8.2, 5.9, 4.6, 2.8, 1.4 and 0.55 ka cal. BP corresponds to quasi-periodical global climate changes in the Holocene named the Bond events. The majority of the cold events recorded in δ13C and δ18O of carbonates can be correlated to the Greenland oxygen isotope curve.

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