Quality Of Groundwaters In The Area Of The Łódź Basin

Abstract

The Łódź basin, and particularly its north-eastern fragment, has a very high economic importance in terms of abundance, still good quality of groundwaters, and their availability in the watershed zone. More than 150 years of anthropogenic pressure is currently only recorded in the qualitative aspect of groundwaters, affected by both the anthropopressure factors and geogenic conditions. The re sults of the regional monitoring, supplemented with own research of the Laboratory of Geology of the University of Łódź, show substan tial pollution of shallow aquifers. This is determined by a number of factors, not always related to urban landscape. Due to their nat ural conditions, deeper Cretaceous aquifers are much less polluted, although the pressure is higher within the small Łódź basin than outside of it. This relates to the forms and intensity of land manage ment, particularly in zones of alimentation of aquifers. The quality of groundwaters of the Łódź basin is also determined by geogenic factors, as exemplified by the Lower Cretaceous aquifer, locally of geothermal character. Contaminants penetrating groundwaters lead to the hydro chemical differentiation of waters in the same aquifer, particularly distinguishing its uppermost layer. Moreover, they cause the degra dation of other elements of the hydrosphere used by man, such as rivers right from their springs, and waters retained in usually small reservoirs. A change in the conditions of transport of pollutants re sults in the activation of some of their forms, e.g. biogenic substanc es, and leads to secondary changes in the quality of stagnant waters. From the perspective of time and area in which the Laboratory of Geology of the University of Łódź conducted research on ground waters in the years 1993–2013, a diminishment of old threats within cities, and activation of new ones outside of cities is observed, often in areas of alimentation of Cretaceous aquifers in the eastern part of the Łódź agglomeration. In the conditions of limited possibilities of registration of groundwater quality by the currently functioning regional monitoring system, and total withdrawal of elements of the national monitoring from the Łódź region, the functioning of our unit is supplemented by the system of identification and registra tion of groundwater quality in the region of the small Łódź basin. An example is the recording in summer of the current year of pollution with petroleum derivatives of a usable aquifer in the southern sub urbs of Łódź. Works on the determination of the scale of the threat for the surrounding intakes have been undertaken.