Evaluation of the total concentration of iron, manganese, cadmium and nickel and their DTPA extractable forms in the common dandelion rhizospheric and non-rhizospheric soil of the lower Vistula river floodplain grasslands / Ocena całkowitej zawartości żelaza, manganu, kadmu i niklu oraz ich form ekstrahowanych DTPA w glebie ryzosferowej mniszka lekarskiego oraz glebie pozaryzosferowej użytków zielonych z terenów zalewowych Doliny Dolnej Wisły

Rhizospheric and non-rhizospheric soils were collected from six topsoils of grasslands in the Lower Vistula River Valley. The research covered the areas of the floodplains between the stream channel of the Vistula River and the flood embankment within the mesoregions of the Fordon Valley and the Grudziądz Basin. The research area, found in the Chełmiński and Nadwiślański Complex of Landscape Parks, is exposed to annual floods. The fluvial sediments are deposited during short-term and, most frequently spring, high discharges of the Vistula River. The amount of the material deposited in the floodplain valleys depends on the range of the flood and landscape-specific local conditions. In the rhizospheric soil of the common dandelion, a higher content of the clay fraction and organic matter was found, as compared with the non-rhizospheric soil material. The total content of Fe, Mn, Cd and Ni and their forms extractable with the DTPA solution differed between the rhizospheric and non-rhizospheric soil. A lower total concentration of the metals was noted in the rhizospheric soil at all the sampling sites. The concentrations of Fe_DTPA and Mn_DTPA forms in Fluvisols were much higher than the concentration defined as the deficit one. A relatively high content of organic matter and the clay fraction in rhizospheric soil makes the metals bound by the sorption complex, thus limiting their bioavailability. Under Regulation of Minister of the Environment of 9 September 2002, concerning soil quality standards for protected areas compliant with nature protection laws, the total concentration of Cd and Ni in non-rhizospheric soil was slightly higher than the admissible value (1.0 and 35.0 mg • kg⁻¹, respectively). Since no unfavourable effect of trace elements on the environment was demonstrated and as the floodplain areas are under agricultural use, to evaluate the pollution, the standards applicable for agricultural land were assumed. According to those criteria, the soils are not classified as polluted with cadmium and nickel.