Mud soils have developed in small depressions on the river floodplains of north-eastern Poland, these mud deposits being shallow, up to 50 cm, and have a 37-53% organic matter content. After drainage, they undergo a muck-forming process, the soil formations of dewatered sites not being abundant in nutrients or base compounds due to leaching connected to the muck-forming process. Higher amounts of Pb and Cd were reported in the surface layers of dewatered soils as a result of bioaccumulation and anthropogenic input.