ABSTRACT
Experimental field research was carried out to obtain pore water in three sites located within a closed depression basin developed in loess on the top part of the Sandomierska Upland: water divide, slope and in the bottom of the depression. At each experimental site the pore water was sampled from the unsaturated zone, from depths of 1.5 and 4 m with the use of a system of soil moisture samplers equipped with a teflon-quartz cube. The concentration of Ca and Mg in the pore water was determined using the ICP MS method. The concentration of Ca in the pore water is the highest and is stable over time: the highest values were found in the slope and the watershed (approximately 500 mg/l on average), while concentrations for ‘bottom’ were 10-times lower and reached up to 50 mg/l. The Mg concentration is about 15% of Ca on the slope and the water divide sites, however, it rises up to 20% in the ‘bottom’. Variation in chemistry between the experimental sites is related to the pH of the pore water and the mineral components in the loess. Intensity of geochemical reactions is closely related to water circulation within the loesses: intensive surface runoff and low effective porosity cause preferential accumulation of water in the ‘bottom’ which favours leaching of carbonate compounds (CaCO3). In addition a high concentration of Ca and Mg in all locations is a result of a strong porous water binding effect by the rock matrix which in turn is a consequence of a recharge deficit.
