The main aim of this study was to determine the sorption and biodegradation parameters of trichloroethene (TCE) and tetrachloroethene (PCE) as input data required for their fate and transport modelling in a Quaternary sandy aquifer. Sorption was determined based on batch and column experiments, while biodegradation was investigated using the compound-specific isotope analysis (CSIA). The aquifer materials medium (soil 1) to fine (soil 2) sands and groundwater samples came from the representative profile of the contaminated site (south-east Poland). The sorption isotherms were approximately linear (TCE, soil 1, Kd = 0.0016; PCE, soil 1, Kd = 0.0051; PCE, soil 2, Kd = 0.0069) except for one case in which the best fitting was for the Langmuir isotherm (TCE, soil 2, Kf = 0.6493 and Smax = 0.0145). The results indicate low retardation coefficients (R) of TCE and PCE; however, somewhat lower values were obtained in batch compared to column experiments. In the column experiments with the presence of both contaminants, TCE influenced sorption of PCE, so that the R values for both compounds were almost two times higher. Non-significant differences in isotope compositions of TCE and PCE measured in the observation points (δ13C values within the range of −23.6 ÷ −24.3 ‰ and −26.3 ÷−27.7 ‰, respectively) indicate that biodegradation apparently is not an important process contributing to the natural attenuation of these contaminants in the studied sandy aquifer.
Abstract. Groundwater-dependent ecosystems (GDEs) have important functions in all climatic zones as they contribute to biological and landscape diversity and provide important economic and social services. Steadily growing anthropogenic pressure on groundwater resources creates a conflict situation between nature and man which are competing for clean and safe sources of water. Such conflicts are particularly noticeable in GDEs located in densely populated regions. A dedicated study was launched in 2010 with the main aim to better understand the functioning of a groundwaterdependent terrestrial ecosystem (GDTE) located in southern Poland. The GDTE consists of a valuable forest stand (Niepolomice Forest) and associated wetland (Wielkie Błoto fen). It relies mostly on groundwater from the shallow Quaternary aquifer and possibly from the deeper Neogene (Bogucice Sands) aquifer. In July 2009 a cluster of new pumping wells abstracting water from the Neogene aquifer was set up 1 km to the northern border of the fen. A conceptual model of the Wielkie Błoto fen area for the natural, pre-exploitation state and for the envisaged future status resulting from intense abstraction of groundwater through the new well field was developed. The main aim of the reported study was to probe the validity of the conceptual model and to quantify the expected anthropogenic impact on the studied GDTE. A wide range of research tools was used. The results obtained through combined geologic, geophysical, geochemical, hydrometric and isotope investigations provide strong evidence for the existence of upward seepage of groundwater from the deeper Neogene aquifer to the shallow Quaternary aquifer supporting the studied GDTE. Simulations of the groundwater flow field in the study area with the aid of a 3-D flow and transport model developed for Bogucice Sands (Neogene) aquifer and calibrated using environmental tracer data and observations of hydraulic head in three different locations on the study area, allowed us to quantify the transient response of the aquifer to operation of the newly established Wola Batorska well field. The model runs reveal the presence of upward groundwater seepage to the shallow Quaternary aquifer of the order of 440 m 3 d −1 . By the end of the simulation period (2029), with continuous operation of the Wola Batorska well field at maximum permissible capacity (ca. 10 000 m 3 d −1 ), the direction of groundwater seepage will change sign (total change of the order of 900 m 3 d −1 ). The water table drawdown in the study area will reach ca. 30 cm. This may have significant adverse effects on functioning of the studied GDTE.
Long-term extensive mining of Zn–Pb ores in the Olkusz area resulted in significant changes of water table levels and chemical composition of water in all aquifers in this area. Within the Permian aquifer, hydrochemical type of water evolved in two general stages. Short-term effect was freshening in the zones of contact with overlying the Triassic limestones and dolomites. Long-term effect was a change in flow pattern and, as a consequence, an inflow of naturally altered and antropogenically contaminated water from the Triassic aquifer into the Permian complex. This was especially intensive in densely fissured and fault zones. As a result of all these processes, hydrochemical type of water shifted from multi-ion types with various combinations of ions towards higher shares of sulphates, calcium and magnesium.
The extensive mining of Zn-Pb ores in the Olkusz region resulted in significant changes of both water table level and chemical composition of water in all aquifers in the area. This was caused by intensive dewatering of mining excavations and development of a thick aeration zone reaching 150 m in a central part of the area. That created favorable conditions for oxidation of metal sulfides occurring in the ore-bearing dolomites (Middle Triassic) and started the process of forming readily soluble hydroxysulphates which then migrated to lower aquifers, including the Permian. As a result of those processes, various metals and other elements toxic to the water environment appeared in leaks observed in mine galleries. Changes in concentrations of selected elements (Fe, Mn, Zn, Pb, Cu, Ba, Ni, Co, As, Cr, Hg, Tl, Ag, Cd, B) in mine waters over the period of the last nearly 50 years were described. Water samples were collected from exploratory boreholes, piezometers, and wells located in investigated area inflows and seepages occurring in shafts and drifts excavated in Permian conglomerates. Mean concentrations of metals (Pb, Cd, Cr, Hg, Tl) and other toxic elements were surprisingly low; Pb, 3.94 μg/L; Cd, 0.2 μg/L; Cr, up to 2.26 μg/L; Hg, 0.25 μg/L; Tl, 3.59 μg/L; and As, 6.31 μg/L. However, the observed concentrations varied significantly over time, reaching respectively up to 190 μg Pb/L, 60 μg Cd/L, 15.6 μg Cr/L, 2.67 μg Hg/L, 81.3 μg Tl/L, and 155 μg As/L.
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