The results presented in the study shows that low level of mercury in the environment is safe for human health. However, systematic and thoughtful monitoring is necessary, as it would allow the prediction of the consequences of climate change on the Hg cycle in the environment.
Mercury (Hg) is one of the most toxic substances for humans, animals, plants and microorganisms, alike. It has mutagenic properties and can be accumulated in the human body. Mercury is a contaminant introduced into the environment from natural sources, including volcanoes and forest fires, re-emission from the ocean and terrestrial surfaces, and anthropogenic activities in the energy production, metallurgy, waste incineration, and other industrial processes. It was estimated that, as a result of anthropogenic activity over the past century, the Hg concentration in the atmosphere has increased by 3 to 5 times and tripled in the surface ocean water (UNEP 2019). Human-caused emission significantly increased the global Hg pool in the environment and resulted in its elevated concentration in air, water, soil and sediments, often exceeding the geochemical background level.
As indicated in HELCOM (2018) and EMEP (2018) reports, Poland is one of the main emitters of Hg to the atmosphere among the Baltic Sea region countries. It is also the country where the reduction of Hg emission is least effective compared to most of Europe (EEA 2019), which proves the urgent need for modernisation and transformations in the energy and industry sectors.
The research and monitoring of current status and trends of THg contamination in terrestrial organisms in Poland are still insufficient, especially when compared with countries such as Sweden or Canada, where regular monitoring of Hg pollution, including the use of bioindicators, began already in the 1960s. The authors selected organisms that can be bioindicators of THg pollution and be useful for identification of Hg ‘hot-spots’, namely brown birch bolete mushroom (Luccinum scabrum) and herbivorous wild animals, mainly deer (Cervidae).
The results of studies of organisms inhabiting both the terrestrial and aquatic environment indicated a moderate or low THg concentration level compared to other places on the globe.Low mercury concentration in fish and wild animals from Poland poses no risk to consumers. Mercury deposited on Polish territory is retained in a less mobile form, mainly bound in organic-rich soils. Environmental conditions in Poland indicate that in soils, its dominant form is inorganic Hg, which is only slightly transformed into MeHg. Consequently, this limits the Hg uptake by terrestrial biota and makes the organic-rich topsoil the main Hg storage in Poland. However, considering the direction of environmental changes, related mainly to the climate, it is forecast that as a result of remobilisation, the Hg outflow from the soil to rivers and consequently into the sea may intensify in the next few years. It is crucial for inland and coastal waters, for which rivers constitute a major source of Hg.