Acidification is a process during which acidity of abiotic components of the environment is increased. Acidification of soils includes several chemical processes. Soil reaction expresses the acidic-basic equilibrium and is determined by nature of acid-basic reactions. The value of pH must not be the only criterion for the evaluation of acidity and acidification. Penetration of acid ions or acid-forming products into soil can have adverse effect upon soil without changing the values of pH. Should carbonates are present in soils they are the first components, which inhibit penetration of acid ions into soil. Basic cations of the sorption complex are the main mechanism of inhibition in soils without carbonates. Monitoring of soils in the surroundings of Košice is under way at two levels: monitoring of soils within the framework or research tasks and monitoring of the soil component, which is part of the monitoring of health status of forests in Slovakia. Soil types, from which samples were taken for the evaluation of immission effects are represented by cambisol, fluvisol, inceptisol and luvisol. They are medium- to heavy-textured soils. Samples were taken in various distances from the emission source (ES) in VSŽ.

Values of pH in KCl ranging from 4.9 (in the northern part) to 7 (in the southern part) were measured in soils in the surroundings of VSŽ. The evaluated soils had medium to high content of phosphorus (P), medium to high content of potassium (K) and high content of magnesium (Mg). Some elements are accumulated in the VSŽ ES immission field over endurable level. The contents of iron (Fe) and aluminium (Al) exceed three times the quantities of these elements in soils in the surroundings of works processing iron ores. The contents of manganese (Mn) and zinc (Zn) are high, but very scattered. The content of copper (Cu) is medium to low pursuant to agronomical criteria. The contents of lead (Pb) are associated with automobile transportation in the surroundings. The contents of cadmium (Cd) exceeding the allowed levels have been ascertained in close proximity of VSŽ ES. The lower contents of cadmium were ascertained in more distant areas. Arsenic (As) was also found in the investigated areas.

Sensitivity of soils to acidification was also evaluated within the framework of monitoring the health status of forests. Indication values of available N, P, basic cations, and sensitivity to acidification and total relative indication values were evaluated for the monitored areas in the Košice region in five-year intervals. The values of available nitrogen are favourable in general, relatively little differentiated, and their action as a stress factor due to its deficit is not expected in the area of Kosice. The resulting indication value on permanently monitored areas, which lie in a larger distance from VSŽ ES, has pointed out to the most favourable conditions in comparison with other evaluated regions in Slovakia.