Differentiation of Concentration Level of Iron Compounds in Water Reservoirs in Subsidence Depressions in the Katowice Upland

The aim of investigations was to evaluate the influence of varied anthropopression on the concentration of iron compounds in water reservoirs located in subsidence depressions treated as geosystems. Investigations were carried out during period of three hydrological years 2003-2005 within 10 reservoirs located in the Katowice Upland. The presence of iron was systematically measured in water and one time in bottom deposits. Measurements in taken samples were made by means of spectrometer of atomic absorption SOLAAR M6. Results confirmed varied influence of anthropopression on concentration of iron compounds in described reservoirs. It refers to waters and bottom deposits as well. Large differences between reservoirs occurred in a case of iron concentration in bottom deposits. The smallest amounts of it (3.10 g kg⁻¹) were stated in transfer (flow-through) reservoir in Sosnowiec. Maximum values occurred also in reservoir in Sosnowiec, and the level of iron concentration in its deposits amounted to 44.28 g kg^-1. Waters were also characterized by varied level of iron concentration. The lowest average values (0.0437 mg Fe l⁻¹) were typical for one of reservoirs in Sosnowiec, whereas the maximum average iron concentration in amount of 0.4331 mg Fe l⁻¹ referred to one of reservoirs in Zabrze. In the described reservoirs dynamic temporal changes in iron concentration in limnic waters was also stated. In every reservoir periods of complete disappearance of this metal occurred, whereas the maximum amounts of it in particular objects changed from 0.1132 mg Fe l⁻¹ in reservoir in the borderland of Bytom and Chorzów up to 1.3744 mg Fe l⁻¹ in reservoir located in Zabrze. The presence of iron compounds in the described water reservoirs on the one hand is shaped by environmental conditions, but on the other hand varied influence of anthropopression decides significantly of their spatial and temporal cycle in the nature.