Scenarios of Nutrient-Related Solute Loading and Transport Fate from Different Land Catchments and Coasts into the Baltic Sea

Yuanying Chen,Georgia Destouni,Vladimir Cvetkovic

doi:10.3390/w11071407

Abstract

This study uses controlled numerical experimentation to comparatively simulate and investigate solute transport and concentration responses and patterns in the Baltic Sea for various solute releases from the land through two different coastal cases. These cases are the Swedish Kalmar County coast and the Polish coast of the Vistula River outlet. For equivalent solute releases, the coastal flow conditions and their interactions with main marine currents determine the local coastal solute spreading, while the overall spreading over the Baltic Sea is similar for the two coastal cases, despite their large local differences. For nutrient-proportional solute release scenarios, the highly-populated Vistula catchment yields much greater total, but smaller per-capita nutrient impacts, in the Baltic Sea than the Kalmar County catchment. To be as low as from the Vistula catchment, the per-capita nutrient contribution from Kalmar County would have to be reduced much more than required on average per Swedish inhabitant by the Baltic Sea Action Plan. This highlights an unfairness issue in the per-capita distribution of nutrient load allowance among the Baltic countries, which needs to be considered and handled in further research and international efforts aimed to combat the Baltic Sea eutrophication.

Highlights

The Baltic Sea is an important semi-enclosed sea environment in northern Europe
This paper contributes to such advancement by using an adapted, tested and validated hydrodynamic model [13] for controlled numerical experimentation aimed at advancing our understanding of physical solute transport through different coastal conditions and further into the Baltic Sea
Field experimentation require release Vistula of solute from the inhabitant, butcomparable only 3.4 kg/year for total nitrogen (TN) and 0.005would kg/year for TPcontrolled from the average catchment coastal location, with the solute tagged to act as a tracer for the subsequent physical transport from a inhabitant

Summary

Introduction

The Baltic Sea is an important semi-enclosed sea environment in northern Europe. Surrounded by several countries that span a total drainage basin of around 1,739,400 km2 [1], the Baltic Sea receives large nutrient loads from land and suffers severe eutrophication problems [2]. Most transport studies have focused on the local scale of a certain part or marine basin of the Baltic Sea [5,6,7,8,9], with few studies considering the full-scale range of transport from land loading into and through local estuaries and coasts to the whole Baltic Sea [10,11]. Such studies are needed for advancing our ability to accurately assess the contributions of different countries to the eutrophication (and pollution) of the Baltic Sea [12].

Methods

Results

Conclusion