Marta Mileusnić

Conceptual model for groundwater status and risk assessment - case study of the Zagreb aquifer system

This paper presents a conceptual model of the Zagreb aquifer system. The conceptual model can be applied to groundwater status risk assessment and pollution risk assessment at the local scale, thus satisfying both environmental and preventative/limitation objectives of the Water Framework Directive (WFD) and Groundwater Directive (GWD). Its main purpose is to apply a risk assessment procedure, according to the WFD requirements, and to serve as a foundation for setting up a numerical model of flow in both the saturated and unsaturated zones in order to identify pressure and impact effects on groundwater quality. The model is divided into two parts, taking into account the WFD requirement to assess a risk for a wide range of source-pathway-receptor relationships. The Global Conceptual Model (GCM) provides insight into the processes and pressures at the level of the groundwater system. It contains the geological and hydrogeological characterization of the Zagreb aquifer system and the description of the most significant point and diffuse sources and pathways of pollution and processes influencing pollutant behaviour in saturated and unsaturated zone of the groundwater system. The main pollutants of the Zagreb aquifer system are potentially toxic metals, nitrates, pesticides, pharmaceuticals and chlorinated aliphatics. A Local Conceptual Model (LCM) supports parameterization of the whole groundwater system through the description of heterogeneities and flow and solute parameters of the system components at two sites representing local conditions in the saturated (Stara Loza) and unsaturated (Kosnica) zones. This concept can be regarded as an effective tool for groundwater management of the groundwater system and its compartments and for communicating the conditions in complex groundwater systems with experts, policy makers and general public in an understandable way.

The origin and composition of flysch deposits as an attribute to the excessive erosion of the Slani Potok valley („Salty Creek“), Croatia

Flysch deposits that crop out in the elongated coastal area of the Vinodol Valley (External Dinarides), and particularly in the Slani Potok (‘Salty Creek’) catchment, are characterized by excessive erosion. Formation of badlands, creeping and sliding processes have been related to crystallization of thenardite. Unusually intense erosion is caused by the dispersive effect of sodium on clay particles (derived from pelitic flysch intervals) in solution, as well as by expansion of thenardite during transformation into a deckahydrate (with a four fold increase in volume). The search for a sodium source required for thenardite crystallization has focused on a particular composition of Slani Potok Eocene fl ysch rock types. Slani Potok flysch is predominantly composed of pelitic intervals, with subordinate sandstones and biocalcirudites. Sandstones and biocalcirudites contain appreciable amounts of siliciclastic detritus. Lithic fragments are represented by volcanic rocks revealing porphyry structures - possibly andesite or altered volcanic glass fragments, quartzite, schists, shales, and carbonate grains. High amounts of sodium and barium (0.93–1.09 % and 267–276 mg/kg respectively), in marls and sandstones, is essentially ascribed to a particular composition of flysch, refl ecting its area of provenance. A Palaeozoic clastic complex with barite mineralization, (black shales, sandstones and conglomerates), as well as a Mesozoic hornblende andesite located near Fužinski Benkovac in the Gorski Kotar region, are interpreted as flysch source rocks. Sodium at least could be partly leached from the lithic and feldspar grains in clastic rocks, due to circulation of pore fluids. An increased amount of sulphur, barium and strontium in flysch can be related to that of a barite ore complex in the source area of the Gorski Kotar region. Transportation and deposition of material eroded from the hinterland (North of Slani Potok), suggests turbidity current flow was transverse to the main axis of the Eocene foreland basin striking NW-SE.

Influence of weathering processes on the shear strength of siltstones from a flysch rock mass along the northern Adriatic coast of Croatia

Weathering processes cause significant changes in the engineering properties of rocks. Slope instability in flysch rock formations along the northern Adriatic coast of Croatia is related to the effects of weathering on the shear strength of siltstones from the flysch rock mass. Therefore, changes in geotechnical properties according to weathering grade are of immense importance in relation to instability processes. In this work, we investigated siltstones from flysch rock masses in the study area, and evaluated changes in engineering properties due to weathering. The research began with field observations and determination of the strength of different weathering grades of siltstones in the area. Mineralogical and laboratory studies were subsequently conducted, and mineral content was determined for siltstones of different weathering grades. We also performed a series of drying–wetting cycles to simulate natural conditions of the weathering process involved in the disintegration of the rock material into sand-sized and smaller particles. This weathering process resulted in disintegration of the siltstone rock mass into smaller particles that were not a unique rock block, with the soil-like material consisting of unbound particles of rock. Laboratory tests were also carried out on the soil-like material to determine the specific gravity, grain size distribution, Atterberg limits and residual shear strength for the different weathering grades of siltstones. Based on this research, we determined the changes in engineering properties for different weathering grades. Our results underscore the significant influence of the weathering process on mineral content, cation exchange capacity, liquid limit and residual shear strength, thus affecting slope stability in siltstones in flysch rock masses.

Magmatic provenance and diagenesis of Miocene tuffs from the Dinaride Lake System (the Sinj Basin, Croatia)

This study presents new insights on the provenance, genesis, and post-depositional history of the Miocene pyroclastic tuffaceous layers (~18 and ~15 Ma) preserved in argillaceous sediments and interbedded within the lacustrine sedimentary succession of the Sinj Basin in central Dalmatia (Dinaride Lake System, Croatia). Analysed tuffs are classified as smectitic tuffs composed of three main lithotypes: (a) vitriclastic tuffs, (b) altered vitriclastic tuff, and (c) tuffaceous clays. The high field strength element (HFSE) contents of the tuffs, as well as the major- element chemistry of the vitric glass, suggests that parental magmas were high-K calc-alkaline trachyandesites. This is consistent with the distinctive heavy-mineral assemblages including clinopyroxene, zircon and apatite, identified in less evolved parental magmas, and biotite in more evolved ones. The regional geological data imply the placement of the parent volcano(es) outside the Dinaric Alps region, most probably in an area corresponding to the present-day southern margin of the Pannonian Basin where volcanic rock suites of analogous age and geochemistry are reported. Minor compaction and high permeability of coarse ash-sized pyroclastic material allowed for extensive in situ diagenetic clay mineral formation dominated by smectite. Following discrete smectite formation, the illite-smectite mixed-layering took place as a result of mica/illite alteration or surface illitization processes. On the basis of the very-low grade alteration of volcanic materials, it is suggested that diagenesis operated in an open hydrologic system of a lacustrine environment.

Urban geochemistry: Sisak in Croatia, a long - lasting historical, urban and industrial city

A soil geochemical survey of the city of Sisak, Croatia, and its surroundings was done to determine the concentration, spatial distribution and sources of the elements in the soil. Factor analysis indicates 8 factors describe the geochemical variations in the topsoil: 4 anthropogenic, 2 geogenic and 2 mixed ones. The main influence in the urban and rural soils was parent material and anthropogenic inputs in the old part of the city, along roads and railways, and in the industrial areas. The results indicate that soils are a very good media for accumulating trace elements in urban and industrial areas.

Environmental geology and hydrology

Abstract Environmental geology is scientific discipline dealing with the interactions between humans and the geologic environment. Many natural hazards, which have great impact on humans and their environment, are caused by geological settings. On the other hand, human activities have great impact on the physical environment, especially in the last decades due to dramatic human population growth. Natural disasters often hit densely populated areas causing tremendous death toll and material damage. Demand for resources enhanced remarkably, as well as waste production. Exploitation of mineral resources deteriorate huge areas of land, produce enormous mine waste and pollute soil, water and air. Environmental geology is a broad discipline and only selected themes will be presented in the following subchapters: (1) floods as natural hazard, (2) water as geological resource and (3) the mining and mineral processing as types of human activities dealing with geological materials that affect the environment and human health.