Mercury in the bottom sediments of the ship channel and river mouths: the Vistula lagoon

The control of mercury in the biosphere is of lasting importance, as it is a toxicant of the first hazard class.Bottom sediments, as a depositing medium, are an important indicator of the long-term ecological state of a water body. In Russia, the hygienic standards for the content of pollutants in bottom sediments of surface water bodies within populated areas have not been approved. To diagnose Hg accumulation, we used comparisons of our results with the background content and threshold levels of hazardous concentrations.These are the domestic regional and Norwegian standards, the Dutch lists of pollutants. The distribution of mercury in bottom silt-pelit and fine and fine-grained sands of dynamically heterogeneous zones of the KaliningradGulf, in the Kaliningrad Sea Canal (KSC) is olated from the open water area and in river mouths that flow into this Russian sector of the Vistula Lagoon of the Baltic Sea, was investigated. Peculiarities of accumulation - mercury scattering are traced for the period 2000-2019. Hg determinations were carried out by accredited laboratories using metrologically certified, but different in accuracy methods: 1) highly sensitive flameless atomic absorption spectrometry (AAS) using the “cold steam” technique (Julia-5K instrument with a detection limit of 0.005 mg/g), 2) using a modified scheme of the Zeeman effect and mercury spectrometers (detection limits Hg = 0.001-0.005 mg/kg). It has been established: from spring to autumn, the activation of storms and surges in the lagoon, the strengthening of the leaching regime of the channels provide a significant decrease in river mouths, and in the dynamically weakened conditions of the KaliningradSeaCanal, an increase in the amount of mercury. The use of the IVA method has led to significant overestimation of the mercury content. In bays of the navigable sea channel, in dynamically problematic areas of the estuary of the gulf and the Primorskaya Bay, and also against the background (alluvium of the Daima River) over a 20-year period, metal accumulated in bottom sediments (up to 0.155- 0.261 mg/kg; determination method - AAS). Against the background, the concentration increased by 3.6 times (from 0.023 to 0.082 mg/kg). In the dynamically weakened and active zones of the estuary - 1.7 and 1.4 times, respectively (from 0.90 to 0.155 mg/kg and from 0.050 to 0.070 mg/kg, respectively). The process ensured a transition from predominantly background accumulation of mercury (<0.15 mg/kg) to satisfactory conditions of a weak level of their pollution with the toxicant of bottom sediments. However, the safe target level of Hg = 0.3 mg/kg is still not exceeded and the current environmental and epidemiological situation regarding the mercury content in the component of surface water bodies that deposit pollutants in the region can be considered successful. Comparison of the results of mercury determinations by different methods indicates the inadmissibility of using low-sensitivity analysis methods for this purpose (inversion voltammetry). The indisputable priority in analytics belongs to the high-precision method of atomic absorption spectrometry using the technique of “cold vapor” and mercury spectrometers.

Keywords

Authors

References