Factors controlling methylmercury concentration in soils of Northern Poland

Soil acts as storage for many toxic substances, including mercury and its compounds. However, in addition to its storage function, soil can also be a source of many substances to the aquatic environment. Methylmercury (MeHg) is one of the most toxic form of mercury (Hg) present in the environment. Some studies consider Poland to be one of the major emitters of Hg into both the atmosphere and the Baltic Sea. The purpose of the study was to identify factors affecting the formation and retention of MeHg in the soil as well as it remobilization to the river. Fifteen soil core samples with a length of 200 cm were collected during the fall/winter of 2021-2022. The factors responsible for the inflow and formation of MeHg were precipitation, distance from the riverbank, soil moisture and age of organic matter. MeHg can be transported to topsoil with precipitation. An increase in MeHg concentration was also observed in moist soils located in the vicinity of riverbank. MeHg concentration was lower in soils with degraded organic matter than with fresh organic matter.