The aim of the study was to determine the influence of lithogenic and pedogenic processes on the distribution of iron forms in soils formed from glaciolimnic sediments, in basins of ice-dammed lakes in north-eastern Poland. The examined soils contained high amounts of clay minerals. However, when they are dry, they shrink and may form large deep cracks, which is unfavourable from the environmental point of view. Therefore, observation and recognition of processes occurring in these soils is crucial. The redox potential and oxygen diffusion rate were measured with a redox potentiometer. The free iron oxides were analysed in sodium citrate and dithionite extract, while amorphous iron oxides were analysed in ammonium oxalate according to the Tamm method. The content of crystalline iron oxides, crystallinity index and weathering index were calculated on the basis of the iron content. Total amounts of iron and manganese were measured after mineralisation in aqua regia. Redox potential results suggest anaerobic conditions in the soils studied. Correlation coefficients revealed statistically positive relationships between the content of total iron and manganese (r = 0.295) as well as manganese and redox potential values (r = 0.262). The soil parent material contained considerably more iron silicates, which suggests less intensive weathering, and was also distinguished by lower amounts of free iron. The results of the iron content determinations and calculated indices suggest that the analysed soils are young and the features of soil forming processes are merely marked.

23.2.2018