Temporal changes in the content of labile and stabile mercury forms in soil and their inflow to the southern Baltic Sea

Variation in the Content of Different Forms of Mercury in River Catchments of the Southern Baltic Sea – Case Study

“…Rivers are the main source of mercury to the Baltic Sea environment, accounting for 85% of the introduced load [23]. Studies conducted by a number of scientists have shown that the highest Hg load is introduced during periods of heavy rainfall, when river water flow increases [13,16,18]. Furthermore, heavy rainfall and snowmelt, which determine surface runoff, contribute to the erosion and leaching of mercury deposited on land, which directly affects the load and form of Hg entering the southern Baltic Sea [15,34,35].…”

“…Nevertheless, irrespective of the season and meteorological/hydrological conditions, the load, which mainly consists of labile forms of mercury, is carried into the sea along with the sediment. Moreover, during snowmelt, which is one of the shortest periods of the year, the load most enriched in labile mercury associated with halides is introduced to the Baltic Sea [18]. This is a direct response to the leaching of mercury from fossil fuel combustion with surface runoff caused by thaw.…”

“…Much of the mercury associated with terrestrial organic matter due to remobilisation from land also enriches riverine suspended solids. Suspended solids (SPM) carry a variety of pollutants including mercury [18,21]. Although the highest loads of suspended Hg are carried into the Puck Bay by the main rivers i.e.…”

“…This indicates a significant impact of coal burning on environmental mercury concentrations. Moreover, despite the introduction of legal restrictions that have led to a reduction in anthropogenic sources of mercury, the metal that has been deposited over decades is now being remobilised from land into river water [13,16,17,18]. The process of Hg leaching into rivers is stimulated by surface runoff, which in turn is amplified by heavy rains.…”

“…the form in which it occurs [16,21,22]. Mercury that is bioavailable to organisms is easily transformed and transported in the environment, which directly affects the form of mercury delivered by rivers to the sea [15,16,18]. This is particularly important because rivers are the main source of mercury to the Baltic coastal zone [23].…”