Geochemistry studies processes, contents and distribution of chemical elements in natural materials. Recently, geochemistry has gained in importance with studies of environmental changes as consequences of anthropogenisation. Interesting are comparisons of chemical composition of sampling media between natural unpolluted environments and the polluted ones, which were changed by human activity. The results of geochemical research are represented as geochemical maps in various scales. A geochemical map is the basis for understanding chemical characteristics of an area, and it is a tool for monitoring changes induced by human activity. Information collected on geochemical maps reveal some basic characteristics of an area, which are often not represented by other geological and geophysical data. They also help recognise the difference between natural and altered state of the environment. Sometimes they enable direct limitation of a polluted area and at the same time the assessment of local background of the investigated chemical elements. The total information is the basis for the assessment of the source and extension of pollution, planning further investigations and planning remediation measures.
A sampling medium has to be present all over the researched area; it has to determine geochemical characteristics of an area and has adequate spatial influence. Materials that can be used as sampling media are: rocks, soils, stream sediments, surface waters, waters from springs and wells, even plants and dust. Different sampling materials describe the land from various aspects: rocks show the distribution of chemical elements in geological basis, soils and stream sediments show portions of those chemical elements that remain subsequent to weathering processes, water mostly soluble chemical elements, plants those portions that are accessible to plants, etc. In each sampling medium, however, portions of chemical elements and compounds that are directly or indirectly introduced by human activity are also present.
We usually use the following sampling media:
- Stream sediment is a representative sampling medium for determination of chemical composition of an area upstream from a sampling point, which makes it the most widely used sampling medium in geochemical mapping.
- Overbank sediment is homogenous fine-grained material that was deposited on flood plains during high water events. Samples taken in deeper parts of overbank sediment reflect chemical composition as it was before the appearance of any human activity.
- Soil can be used as sampling medium in areas with poorly developed (carbonate basis) or completely absent (karst) hydrological network. Elements in traces are present in resistant primary materials originating in base rock, in secondary newly formed minerals, and bound to clay minerals and organic matter. Apart from geological and pedological characteristics, they provide information on aerial pollutants and are therefore widely used sampling medium.
- Household dust is a type of dust that is deposited on surfaces inside the houses far from the influence of weather conditions. It consists of particles from the air that originate in soil dusting and household activities. Attic dust is a type of household dust that is deposited in attics - rooms in which house inhabitants only rarely stay – and is not influenced by everyday activity of the inhabitants of a house.
A book produced by the geochemical research group "Geochemical Atlas of Ljubljana and Environs" is a good example of a collection of geochemical maps.
Numerous geochemical investigations are conducted with a purpose of environmental research and assessment of heavy metal load in the environment. In Slovenia, research is conducted with a purpose of determination of distribution of heavy metals as a consequence of natural conditions (mineralization) or in combination with the influence of human activity, especially hundreds of years of mining (Idrija, Mežica, Sv. Ana, Podljubelj, etc.), metallurgy (Jesenice, Celje, etc.) and industries as well as traffic emissions (Ljubljana).
We have been successfully using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), which enables morphological surface analysis and qualitative to semi-quantitative chemical microanalysis of materials, in geochemical investigations since 2008. SEM/EDS is being used for the analysis of different sampling media from metal-polluted environments. Morphology and chemical and mineral composition of micron-sized solid metal-bearing particles, which are potentially harmful to human health and the environment, are being studied. Results of SEM/EDS analyses help us determine the solid forms of metals. Based on morphological and chemical properties of particles, which are dependent on processes involved in their formation and chemical composition of source material, we can assess potential natural or anthropogenic sources these particles emanate from.
Special attention is also devoted to improvement and development of sophisticated data processing methods based on linear and non-linear modelling such as multivariate statistical methods, universal kriging, segment kriging, multiple polynomial regression and artificial intelligence - multilayer perceptron. The preliminary results obtained by the artificial intelligence are very promising due to the fact that various attributive parameters (such as geospatial data and climatic factors) can be used for predictions of concentrations of chemical elements.
Our other activities are:
- Soil pollution assessment in smaller areas for a purpose of land sale, building, changes of land function, etc.
- Reports on environmental impacts (soil and vegetation)
- Inventory of abandoned mines and mining wastes in Slovenia
- Co-operation in the production of maps of geohazard
- Co-operation in structure – geological mapping for highway construction programme in Slovenia
- Co-operation in deep geothermal borehole siting