Laboratory and field experiments have been conducted to study mobility of chromium and lead in floodplain sediments. The main goal of the research was to verify a hypothesis whether changes of chromium and lead concentration could be used to estimate the relative age of floodplain deposits. The basis for undertaking such research was the presence of weaving industry centers in the Obra River valley between the 16th and the 19th century and using Cr and Pb compounds in paint recipes. The Cr and Pb contents were also analyzed in three vertical profiles unaffected by the field experiments. The age of organic sediments in each of the profiles was determined using the radiocarbon analysis. The results of the laboratory experiments have shown that the highest contents of the elements were noted in the surface layer of the sediments placed in the column. However, the contents decreased during the last phase of the experiments and both vertical and horizontal migration of both elements was observed. A more intensive mobility was observed in the field test. Its cause could be the changes of the groundwater level, floodplain inundation and pH conditions in alluvial deposits. Such processes may have influenced migration of the compounds originating from the weaving industry production; Cr and Pb contents detected in the profiles unaffected by the field experiment were too small to be used for relative dating of alluvial deposits. Moreover, the alluvial deposits with increased contents of the studied elements may be older than the period of the weaving industry development. Cr and Pb mobility was especially intensive in the profiles situated within the near bed zone of the floodplain due to regular inundation, and the activity of erosion and accumulation processes entraining the studied elements back to transport in the river bed.
The research was conducted at the Kwiatków site,1 in the Koło Basin (Central Poland). It included a fragment of a low terrace and the valley floor of the Warta river valley. The archaeological investigation documented over 100 wells that archaeological material indicates are associated with the Przeworsk culture. Geomorphological, lithological and geochemical studies were carried out at the archaeological sites and their surroundings. Selected for the presentation were two wells whose fillings were carefully tested and subjected to geochemical and lithological analyses. The wells showed a slightly different content of artifacts, as well as differences in their grain-size distributions, the structure of their filling deposits, and their geochemistry. This allows us to conclude that the two wells were used differently, but also probably about a different course for how each well was filled after the end of its operation.