Heavy metals: their pathway from the ground, groundwater and springs to Lake Góreckie (Poland).

The migration pathways of heavy metals derived from an area previously in agricultural use was investigated in the Wielkopolski National Park (mid-western Poland). The heavy metals involved (Cd, Cu, Cr, Pb, Ni and Zn) were determined in groundwater, the springs that feed Lake Góreckie and the lake itself. In order to show how the heavy metals may be set free and what is their biological availability, soil and sediment samples were subjected to single-stage extraction, using 0.01 M CaCl(2), 0.02 M EDTA, 0.005 M DTPA, 0.1 M HCl, 1 M HCl and de-ionised water. Varying metal concentrations were recorded in the water samples during the study period (from November 2009 to July 2010), usually with higher values in winter and lower ones in summer. The seasonal changes may be ascribed to natural processes taking place in the ground- and surface waters of Lake Góreckie. On the other hand, the concentration levels (mostly of Cd, Pb and Cr) are indicative of anthropogenic activity. It should be mentioned in this context that the highest metal concentrations were found in the soil layer. The concentrations were also found to exceed both the Polish and the World Health Organization water-quality standards. It appears that the soils are highly contaminated, mostly with cadmium. The long-lasting effect of acid precipitation in the area makes it possible for immobile forms to become mobile, thus facilitating further migration into the environment.