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The paper presents research on filtration characteristics of the alluvial sediments of the Stip aquifer in order to determine the degree of protection from ground water pollution. Previous studies determined that alluvial sediments of the Stip aquifer are built of two layers of different granulometric and filtration characteristics. The water-bearing layer is a coarse-grained porous media built of sand and gravel with hydraulic conductivity ranging from 48 to 280 m/day. This layer is overlaid with fine-grained sediments having low filtration characteristics. Overburden consists of dusty and clayey dusty sands with hydraulic conductivity ranging from 2×100 - 1.5×10-3 m/day. This research showed that overlay sediments don’t provide sufficient natural protection for ground water of the Stip aquifer and that they pertain to susceptible geological environment.

This paper presents the results of hydrochemical investigations of groundwater from the Prilep part of the Pelagonia valley - Republic of Macedonia. These investigations were carried out by analyzing 12 samples of groundwater, taken from the exploitation wells. Samples are taken once a season, during August 2013. Values of the pH were determined with the field digital pH meter, while cations are determined by inductively coupled plasma-atomic emission spectrometry (ICP – AES). For the determination of the anions are used standard EPA methods (gravimetric - TDS, volumetric - Cl-, spectrophotometric - NO3-, NO2-, NH4+ and turbidimetric - SO42- with the spectrophotometer 6715 UV / VIS, Jenway). Тhe maps with spatial distribution of the hydrochemical components were prepared using the IDW (Inwerse Distance Weighting) method for map generation (Geographic Information System software (GIS) ESRI® ArcGis™ 9.2 and its extension Geostatistical Analyst). Spatial distribution maps were constructed according to the coordinates and sample content of each analyzed sample. Samples were taken from the wells which are divided into 3 groups: wells with free level with depth up to 10 m, wells with free level with depth up to 100 m and artesian wells. The graphical methods, Piper diagram and Chadha’s diagram, were applied in order to determine the hydrochemical properties of the groundwater. The results indicate that the groundwater samples have different hydrochemical properties. Ca 2+ >Na+>Mg2+ for the cations and HCO3- >Cl- >SO42- for the anions were dominantly dissolved ions in the majority of the water samples. Generally, increased values of Ca2+, Mg2+, Na+, K+, HCO3-, K+ and Cl- occur in the groundwater from deeper artesian wells, as a result of the longer retention time of water in the underground and its interaction with the geological environment. Dominant groundwater in Prilep field, in all three types of wells, are waters from hydrocarbonate class (HCO3¯), calcium group (Ca), the first type of water. Groundwater from the shallow wells show the increasing content of K+, NO3- and PO43-which indicates water pollution from fertilization of the cultivated areas, livestock farms as well as communal wastewater. Although hydrochemical data are obtained on the basis of water samples taken only once, they provide an indicative insight into the hydrochemical composition of the water. To obtain more reliable data, taking groundwater samples from wells should be performed multiple times in different seasons.

Hydrochemical properties of water samples from the Slatinski Izvor spring and Solenica spring were analyzed during the period between December 2011 – November 2013. The wider area around the springs belongs to two tectonic units. The first is the Pelagonian horst-anticlinorium and is composed of carbonate rocks. The second is the Western Macedonian zone, and it is composed of non-carbonate rocks. The Slatinski Izvor spring is located on the Pelagonian horst anticlinorium, and the Solenica spring is situated on a fault which separates the two tectonic units. The measurements of the temperature, conductivity and the hydrochemical analysis indicate that both springs have different hydrochemical properties. The major cations in the Slatinski Izvor spring were Ca2+ and Mg2+, and anions were HCO3- and SO42-, the water had temporary hardness and it belongs to calcium hydrogencarbonate water type. The Slatinski Izvor spring had typical shallow and fresh water. The major cations in the Solenica spring were Na+ and Ca2+, and anions were Cl- and HCO3-. The water belongs to NaCl water type which is typical of deep ancient ground water. Hidrokemijske lastnosti izvirov Slatinski izvor in Solenica (Republika Makedonija) Hidrokemijske lastnosti vodnih vzorcev iz izvirov Slatinski izvor in Solenica so bili analizirani v obdobju od decembra 2011 do novembra 2013. Širše območje izvirov pripada dvema tektonskima enotama. Prvi je Pelagonijski horst-antiklinorij in je sestavljen iz karbonatnih kamnin. Druga je Zahodno-makedonska cona in je sestavljena iz nekarbonatnih kamnin. Slatinski izvor se nahaja v Pelagonijskem horst-antiklinoriju, Solenica pa na prelomu, ki ločuje obe tektonski enoti. Merjene temperature in električne prevodnosti ter hidrokemijske analize kažejo na razlike v hidrokemijskih lastnostih obeh izvirov. Glavna kationa v izviru Slatinski izvor sta bila Ca2+ in Mg2+, aniona pa HCO3- in SO42-, voda je imela karbonatno trdoto in pripada kalcij hidrogenkarbonatnemu tipu. Slatinski izvor je imel tipično plitvo in sladko vodo. Glavna kationa v izviru Solenica sta bila Na+ in Ca2+, aniona pa Cl- in HCO3-. Voda pripada NaCl tipu, ki je značilen za globoko, staro podzemno vodo.

In order to investigate the pollution with hexavalent chromium (Cr6+) of the groundwater and surface water around the industrial dump Jugohrom – Jegunovce, hydrogeological investigations were carried out during November 2019, where 16 samples of groundwater and 3 samples of surface water were taken. In most of the analyzed samples of groundwater and surface water, the concentration of Cr6+ exceeds the maximal allowed concentrations (MAC) of Cr6+ (0.01 mg/l) according to the Macedonian and European standards in drinking water. The highest contamination with Cr6+ which is in the range of 0.052 – 132.98 mg/l is registered near the dump in the shallow groundwater, i.e. in the unconfined aquifers. Cr6+ pollution ranging from 0.017 to 0.041 mg/l has also been registered in some of the samples at artesian aquifers with a sub-artesian level. Two tests were carried out on the surface water of the Vardar River, before and after the dump. A sevenfold increase in Cr6+ concentration of 0.069 was observed after the dump. Cr6+ content of 725 mg/l was found in the drainage of overflow water in the discharge. Pollution of the groundwater and surface water with Cr6+ is anthropogenic and is a result of the operation of the Metallurgical Plant Jugohrom in the period from 1955 to 1994.