The role of the North Sea in the cycling of persistent organic pollutants
Zusammenfassung der Projektergebnisse
The cycling of two selected POPs with very different properties, y-HCH and PCB 153, has been investigated with a fate and transport ocean model, FANTOM, for the North Sea system. The FANTOM has been combined with a high resolution version of the HAMSOM hydrodynamic model. The model domain includes the entire North Sea system and model simulations are for the 1996-2005 period. The FANTOM model is undergoing continual development. Recent improvements, such as the use of reasonable spatial and temporal distributions of POPs in the atmosphere, improved open boundary and initial conditions, and corrections to flux and conservation calculations, have led to a set of interesting new results not anticipated in previous FANTOM simulations. y-HCH is practically all dissolved in water. It displays a clear seasonal cycle with maximum values in the water column in August and minimum values in February, while sediment extreme lag behind by about two months. Total mass of y-HCH in 2005 is just 30% of that in 1996. Concentrations in the water column are greatest in the vicinity of Continental river sources, with large values seen close to southern British sources. Concentrations are also large to the west of Jutland, the Skagerrak and near the Norwegian coast. Concentrations in sediment are greatest surrounding Continental and British river sources with large values seen in most coastal regions. Dry gas deposition is the greatest source of y-HCH to the North Sea, and is more than an order of magnitude larger than wet deposition, the next greatest source. Degradation in water is the greatest sink of y-HCH while the net sink at the open boundaries is fairly negligible. Since dry gas deposition is greater than volatilization, the North Sea acts as a sink of Y-HCH. Nearly all PCB 153 in the North Sea is sorbed to POC and contained in the sediment. A clear seasonal cycle is seen with maximum values in the water column during the winter months. Concentrations decrease in spring before reaching minimum values in late summer. In sediment, minimum concentrations are seen during the winter months, again following the onset of winter storms, values increase in spring, and maximum concentrations are reached around August. Total mass of PCB 153 in 2005 is reduced to 80% of 1996 values. Concentrations in water are greatest near British and Continental river sources, with large values also around the Wadden Sea to the west of Jutland, the Skagerrak, and, to a lesser extent, offshore of the Norwegian coast. Similar patterns are seen in sediment. Input through rivers is the greatest source of PCB 153 for the North Sea, followed by wet and dry gas deposition and finally dry particle deposition. Volatilization is the greatest sink, followed by degradation in sediment and degradation in water, while the net sink at the open boundaries is relatively negligible. Since volatilization is at least an order of magnitude greater than the sum of all sources, the North Sea acts as a source of PCB 153 to the atmosphere. An in depth analysis of future POP scenarios is currently underway. A preliminary analysis shows that seasonal cycles for both POPs do not change from present day runs. The total mass of y-HCH in water increases by 5-10% for the period 2006-2014 relative to the two future runs which is attributed to increasing water temperature and volatilization. Total mass in sediment remains steady for all three runs. For PCB 153, total mass in water decreases substantially over the first three years of each of the three runs after which it remains steady. In sediment, the total mass decreases continually to the end of all three runs. The number and intensity of winter erosion events increase in the two future runs relative to the 2006-2014 run which result in more of the POP being resuspended into the water column and less remaining in sediment due to the predicted increase in storm intensity for the 21st century. Distributions of y-HCH do not change much from 2004. However, concentrations in the northern half of the North Sea are greater in winter than in summer, a reverse of what is seen in 1997 or 2004. For PCB 153 seasonal distributions are similar to those seen in 1997 and 2004 with reduced concentrations in the vicinity of British and Continental rivers.
Projektbezogene Publikationen (Auswahl)
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Modelling the role of air-sea exchange processes in the cycling of persistent organic pollutants (POPs) in the North Sea. SOLAS conference, Nov 2009, Barcelona
O'Driscoll, K., T. Ilyina, T. Pohlmann, B. Mayer, and P. Damm
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Modelling the fate of persistent organic pollutants (POPs) in the North Sea System. AIMES Open Science Conference, Earth System Science 2010. Edinburgh, May 2010
O'Driscoll, K., T. Pohlmann, T. Ilyina, B. Mayer, and P. Damm
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Modelling the fate of Polychlorinated biphenyls (PCBs) in the North Sea System with a Fate and Transport Ocean Model (FANTOM). International PCB Workshop in 2010. Visby, Sweden, May 2010
O'Driscoll, K., T. Pohlmann, T. Ilyina, B. Mayer, and P. Damm
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2011. Modelling the fate of persistent organic pollutants (POPs) in the North Sea System. Procedia Environmental Sciences, 6, Earth System Science 2010: Global Change, Climate and People, 159 - 169
O'Driscoll, K., T. Pohlmann, T. Ilyina, B. Mayer, and P. Damm
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Modelling the cycling of persistent organic pollutants (POPs) in shelf seas with a combined hydrodynamic and fate and transport ocean model: the North Sea system. SETAC Annual European Meeting, Milan, May 2011
O'Driscoll, K., B. Mayer, T. Pohlmann, T. Ilyina, and P. Damm
