VARIABILITY OF CHEMICAL WEATHERING INDICES IN MODERN SEDIMENTS OF THE VISTULA AND ODRA RIVERS (POLAND)

The survey was conducted to determine chemical weathering indices in modern river sediments in Poland. Weathering Index of Parker (WIP), Chemical Index of Alteration (CIA), Vogt's Residual Index (V), Harnois's Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA) was calculated for 178 sediment samples taken from the Vistula River and its tributaries as well as for 114 samples from the Odra River and its tributaries. The indices values were in the ranges: WIP 0.5-20; CIA 4-80; V 0.1-2.8; CIW 4-82; and PIA 3-81.7. The observed variation of values resulted from a varied sample lithology and varied climatic conditions in the Poland area. Sediments from the upper parts of the Odra and the Vistula drainage basins (southwestern part of the country), where pre-Quaternary rocks are exposed, are more resistant to chemical weathering and characteristic for lower susceptibility to leaching of elements. The highest elements losses due to leaching are characteristic for samples taken from the lower parts of the Odra and the Vistula drainage basins, dominated by Quaternary deposits. Additionally, it was found that larger indices values, reflecting effects of stronger weathering, are observed in the southwestern part of the country (with the warmer and more humid climate) comparing to the northeastern part (with prevailed colder and drier climatic conditions).