Abstract
Mercury (Hg) can be introduced into the marine environment in many different ways. In the case of the Baltic Sea, rivers and atmospheric deposition are the predominant ones. However, in the face of ongoing climate change, a new potential source, coastal erosion, is starting to become more important and is currently considered to be the third largest source of Hg in the Gdansk Basin region. It is especially significant along sections of coastline where, due to the higher frequency of extreme natural phenomena such as storms, heavy rains, and floods, increased erosion processes have already been noted. Cliffs, which account for about 20% of the Polish coastline, are particularly vulnerable. The aim of the study was to estimate the annual load of labile Hg entering the Gdansk Basin as a result of coastal erosion. Samples of down-core sediments (0–65 cm) were collected in the years 2016–2017 from selected cliffs situated in the Gulf of Gdansk area. The thermodesorption method was used to distinguish between labile and stable fractions of Hg. Considering the mean total Hg concentrations in the collected sediments (9.7 ng g−1) and the mean share of labile (64%), bioavailable mercury, it was estimated that the load of labile Hg originating from coastal erosion entering the Gdansk Basin is 10.0 kg per year. The load can increase by up to 50% in the case of episodic abrasion events during heavy storms and rains.
Highlights
Mercury (Hg) is one of the most dangerous environmental pollutants
The values measured in the cliffs were several times higher than the HgTOT concentrations measured in the surface sediments of the Gulf of Gdansk coastal zone (Jędruch et al 2018b)
The different compositions of the Puck cliff are confirmed by the results for concentrations of other metals (Ti, V, Cr, Mn, Fe, Cu, Zn, Rb, Zr), measured in parallel studies conducted by the authors (Kwasigroch et al 2016), which were statistically significant different (Kruskal-Wallis test, p < 0.05) compared to the results obtained for other cliffs
Summary
Mercury (Hg) is one of the most dangerous environmental pollutants. This is primarily associated with its toxicity, which depends on the chemical form. Hg enters the sea mainly via rivers transporting pollution from the catchment area and through atmospheric deposition (Bełdowska et al 2014). An important role is played by Hg washed out of land as a result of coastal erosion. The research carried out by the authors in previous years showed that the share of this source in the Hg load to the Gulf of Gdansk is over 5%, which makes coastal erosion
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