The present study broadened the research on the effect of the intensive physical disintegration of clay minerals (kaolinite and "Otay" montmorillonite) and mica (ripidolite), carried out by high-energy ball milling (HEBM), on their surface physicochemical characteristics, i.e., the specific surface area (SSA), the cation exchange capacity (CEC), and the electrokinetic properties. The mechanical disintegration of clay minerals occurred in two consecutive processes. Significant changes of the size, morphology and structure were followed by the change of the physico-chemical properties. The decrease of the particle size of the clay minerals resulted in significant increases in the SSA and CEC values, and in the exposure of new, amphoteric surfaces, significantly changing the electrophoretic mobility (EPM).Prolonged milling produced amorphous alumina-silicate aggregates. These solids exhibited the same morphological properties, SSA and CEC, despite the fact that they were formed from initially different clay minerals. In contrast, the electrophoretic mobility of these samples was significantly changed, exemplifying the significance of the initial chemical composition and the formation of different types of surface structures on the physico-chemical processes at amorphous solid-surface-liquid interfaces.

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Purpose Suspended particulate matter (SPM) plays a crucial role in the transport of natural and anthropogenic substances. However, obtaining a representative sample and a substantial amount of SPM in rivers, where the flux and quantity of SPM are highly episodic, can be a challenging task. To collect a sufficient quantity of SPM for detailed sedimentological and geochemical analysis, a time-integrated mass flux sampler (TIMS) was used for the sampling in a medium size river (the Sava River, Croatia). Materials and methods Sampling was conducted in August and October 2014, and February and May 2015 under different discharge conditions. The SPM collected by TIMS was characterized with respect to its particle size distribution (PSD), mineral content, and geochemical composition. Results and discussion PSD analysis identified silt as a dominant size fraction in all samples except in May 2015 when sand prevailed; subsequent chemical dispersion of samples revealed flocculation as the main factor responsible for the resulting PSD. The mineralogical composition of the SPM was quite constant (quartz, calcite, dolomite, feldspar, illite/muscovite, kaolinite), but the contribution of particular mineral varied depending on the sampling period. In May 2015, unusually high calcite content was determined. Though the dominant source is still uncertain, a portion of calcite is likely detrital in origin. Geochemical analyses of collected material revealed significant anthropogenic input of ecotoxic elements (Ni, As, Cr, Pb, Bi, Cd, Zn, Sb) primarily associated with the fine fraction of the Sava River SPM. Conclusions A considerable amount of the SPM was collected by TIMS, both during high and low river discharge. Sedimentological analyses of the Sava River SPM suggested the input of material from various sources during different river regimes. Geochemical composition of the SPM followed its sedimentological characteristics-preferential adsorption of trace elements to fine-grained clay mineral particles was documented. Some processes inside TIMS were observed during this investigation-the suspended material captured inside the sampler underwent additional changes. The flocculation of the colloidal material instigated by algal bloom was observed.

The activity concentrations and the distribution of manmade '^'Cs and naturally occurring radionuclides'^''K, ^^'U and -^-Th in surface and core sediments of the semi-enclosed, river-dominated marine environment of the Neretva Channel were investigated in relation to the sedimentological characteristics and the total organic carbon (TOC) content. The activity concentrations of radionuclides were determined by gamma spectrometry. Distinct interrelationships between sediment properties and the spatial distribution of radionuclides were observed. The highest accumulation of '^^Cs occurs close to the river mouth, in the region of intensive deposition of organic matter of terrestrial origin. This discovery implies that the river-borne organic material and its deposition processes should be considered as the most important factor controlling distribution of '"Cs in this transitional terrestrial-marine environment. Sediment accumulation rates, estimated from the distribution of '^^Cs in core sediments, were approximately 6 mm y ' in front of the Neretva River mouth and 4 mm y"' in the channel area. The spatial distribution of natural ''"K and -^^Th radionuclides indicates their distinct association with fine-grained sediments. The interrelationship of ^^^U with fine-grained particles was somewhat weaker but still present. The results obtained indicate that the accumulation pattern of natural radionuclides in the Neretva Channel sediments is mainly governed by the deposition of fine-grained material. This study scrutinizes the baseline level for the occurring radionuclides and should be used for monitoring and assessing the radionuclide pollution record in the investigated transitional terrestrial-marine environment of the Adriatic.

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