2949775648

44

H. Maruszczak, M. Wilgat

an index considerably exceeding 50%. The lowest percentage of municipal and industrial wastewater is typical for the Sola, Raba and Dunajec river catchments; in these catchments the percentage of this component is many times lower than of that coming from precipitation. This is connected not only with their weak industrialization but also with forest cover, and above all probably with a very high Chemical denudation of the lithosphere. In the Wieprz river catchment, with the absolute ąuantity of the solute yield coming from municipal and industrial wastewater similar to that in the Sola and Raba river catchments, the percentage of this component is distinctly higher in relation to a considerably lower index of Chemical denudation, as well as lower total solute yield.

The differences between the physico-geographical regions are also distinct. If we disregard the strongly-industrialized regions, the following picture of the differentiation is obtained:

The regions of the Carpathians and their foothills are characterized by high indices of total solute yield, usually in the rangę 70-100 t km^-2^¹. The component of Chemical denudation prevails here, and even predominates in some places; in the Dunajec river catchment it is as high as 77%. The intensity of Chemical denudation is here the highest in the whole Vistula river basin and amounts to 50-85 t km^_2y^_1; above all this is connected with very high indices for solute yield.

The regions ofthe Carpathian Foredeep basins. Nonę of the catchments we examined represents this type; as a matter of fact there are no catchments of an area of 1000-2000 km² entirely situated within this belt. Therefore, only on the basis of our map of solute yield from rural areas can we assume that the indices for total solute yield here are in the interval 40-60 t km^y^-1. The percentage of the component coming from Chemical denudation is lower than in the former belt, and over large areas it amounts to about 50%.

The regions of the Southern Polish Uplands are very differentiated in regard to the specific river discharges and geological structure (susceptibility of the bedrock to leaching). Of the analyzed catchments, those of the Nida and Kamienna rivers are typical for this belt. The indices for the total solute yield here are in the interval 40-100 t km^y^-1. The component coming from Chemical denudation usually exceeds 50%.

The regions ofthe Central Polish Lowlands are less differentiated. Among the catchments analyzed only those of the Radomka and Bzura rivers are entirely situated within this belt, and the latter is strongly polluted by municipal and industrial wastewater. Indices for total solute yield here are the lowest in the whole Vistula river basin; in lowlands of the Polesiye type they even fali below 20 t km^y^-1, and on heights built of glacial sediments of the Middle-Polish glaciation they only slightly exceed 40 t km^-2y^-1. The component coming from Chemical denudation falls distinctly below 50%; in the Bzura river catchment its percentage is slightly higher than that from precipitation, amounting to 27%. The intensity of Chemical denudation is