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Biogeochemistry of nutrients, metals and organic micropollutants in the North Sea

Research project MN/DD1/001 (Research action MN)


Persons :


Description :

There can be no doubt that men and their activities have weighed heavily on coastal areas in the last fifty years. In some respects, the situation may even continue to deteriorate which will further reduce their attraction. The discharge of waste, their carriage by the Scheldt and the deposit of atmospheric pollutants all constitute threats. There is, on the one hand, increasing eutrophication and a proliferation of algae resulting from the increased carriage by water of nitrogen and phosphorus and, on the other, the threat that the life of animals and plants will be reduced by contamination by heavy metals and micropollutants. The so-called "red tides", the dramatic proliferation of certain colonies of algae and mercury and cadmium pollution are already universally recognised. The purpose of this research project is to examine the principle means by which pollutants are carried to the North Sea and to track them once they reach it.


The Project

The atmosphere

Atmospheric flows of certain toxic metals, polychlorobiphenyls, polycyclic aromatic hydrocarbons and pesticides have already been studied for some time. However, with other significant groups of inorganic and organic pollutants and data on the interaction between the air and the sea currently either do not exist or else are unreliable. Everybody realises that atmospheric transport to the oceans is one of the principal sources of nutrients on a world-wide scale (such as nitrogen and bioavailable trace elements of which silicium is one) which play a vital part in primary production. Extremely high levels of deposit can have a profound effect on the ecosystem of the North Sea and, locally, in certain atmospheric conditions, produce excesses of algae. So far, no one has given it any thought in mathematical models. Consequently detailed and reliable data on the quantities of the main nutrients deposited by the atmosphere have to be gathered. This will involve monitoring based on location, season and the origins of the atmospheric mass above the North Sea.

A very significant part of organic contaminants is Volatile Organic Compounds (VOC), a large group of chemically different substances which have multiple and diverse effects. VOC affects atmospheric processes, some types are carcinogenic, others are persistent and have the effect of causing bioaccumulation. Nine types of VOC, all of them chlorinated, have been included in the list of the 36 priority toxic pollutants presented at the Third Conference on the North Sea. Consequently there will have to be research into their sources, concentrations and flows in the marine environment. A first monitoring campaign has shown that the Scheldt is a significant source of VOC in the marine environment. As regards these composites, it seems that there is a flow from the water into the air with the various places located in the centre of the continental plateau. On the occasion of outbreaks of algae, high concentrations of certain hydrocarbons were measured. Whatever causal relationship may exist between the proliferation of algae, increased concentrations and air/sea flows will have to be studied.

Where heavy metals are concerned, the level of atmospheric pollution above the North Sea seemed to rise when the wind was from the Southeast, for example, from Belgium. Airborne deposits of cadmium and lead equal those from rivers or direct outflows of industrial waste and wastewater. Quantities of zinc and lead, unlike other elements, seem to be decreasing. The great variations in concentrations and deposits have required taking a large series of measurements in order to establish reliable and accurate averages.
Another significant observation is that the main differences in the flow of deposits modelled and those measured are caused by particles which are relatively among the largest (>4µm) which are responsible for from 85 to 99% of dry deposits. Such particles settle rapidly and do not fly far. Since virtually all of the North Sea is close to their continental sources, special attention is paid to such particles in the project.


The aquatic phase

- As regards the aquatic phase in the North Sea, the research is intended, within the general context of the problems involved in eutrophication, to give a qualitative and quantitative description of how nitrogen is absorbed. This is determined by (1) the availability of nutrients, (2) the relationships between the various nutrients (covering, among others, those between nitrogen and phosphorus and nitrogen and silicates) and the various forms of nitrogen and (3) species of phytoplankton.

The description will have to be drawn from the study of two aspects: (1) the sequestration of carbon through primary productivity, and, (2) the quality aspect underlying the food chain in the form of the relationships between the different types of plankton (diatom and non-diatom).

- The study of trace elements in the water, both those which are essential and those which are toxic, will focus on their bioavailability and the biogeochemical cycles. This will include rates of adsorption, assimilation and chemical speciation. Such studies of speciation in the waters of the North Sea are of crucial importance in gaining a better understanding of transport mechanisms and conversion and the contrast between bioavailability and toxicity. The study will concentrate chiefly on parasite elements such as mercury and cadmium and on those which are essential such as iron and manganese.

- Additionally, a number of volatile organic compounds will be measured in water and sediment of the North Sea and the Scheldt estuary. Also, possible natural production of certain VOC in sediment will be studied.


The partners

- Thanks to the experience acquired in the course of the Programme for the Encouragement of Marine Science of the OSTC, the Centre for Analysis of Micro- and Trace Elements at UIA (Universitaire Instelling Antwerpen,Professor R. Van Grieken) and the Laboratory for Organic Chemistry of the University of Ghent (Professor H. Van Langenhove), the focus in the project will be on research into air/sea flows of certain new organic composites (UG) and nutrients (UIA) and refining our quantitative understanding of the behaviour of heavy metals (UIA) by reducing uncertainties and studying speciation in atmospheric transport.

- The contribution of the Laboratory for Analytical Chemistry of VUB (the Flemish Free University of Brussels, VUB, Prof. W. BAEYENS), consists of analyzing the distribution of nutrients, the relocation of nitrogen and the dissemination of trace elements such as aluminium, iron, manganese, copper, zinc, nickel, cadmium and lead, with particular attention to the dissolution phase, the mechanics and the kinetics of trace elements using stable isotopes. Special attention will also be paid to mercury in the air and in water. The main objective of the contribution of the Chemical Oceanography Laboratory (Prof. R. Wollast) of the U.L.B. (French-speaking Free University of Brussels) is to gain a better understanding of the biogeochemical behaviour of trace metals such as manganese, copper, zinc, nickel, cadmium and lead.
To achieve this aim, attempts have to be made to better define the speciation of the particulate trace metals and the physico-chemical properties of the suspended matter.


Documentation :

For further information please contact:

Centre for analysis of micro- and trace elements - Universitaire Instelling Antwerpen
Universiteitsplein 1, 2610 Antwerpen-Wilrijk
Tel: +32-3-820 23 62 - Fax:+32-3-820 23 76 - E-mail: vgrieken@uia.ua.ac.be

Biogeochemistry of nutrients, metals and organic micropollutants in the North Sea : final report  Van Grieken, R. - Baeyens, W. - Van Langenhove, H. ... et al  Brussels : Federale Science Policy, 2004 (SP1381)
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Bibliografic references :

Contrasting nitrogen uptake by diatom and Phaeocystis-dominated phytoplankton assemblages in the North Sea  TUNGARAZA, C; ROUSSEAU, V; BRION, N; LANCELOT, C; GICHUKI, J; BAEYENS, W; GOEYENS, L. JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, 292 (1), 2003 

Influence of bacterial activities on nitrogen uptake rates determined by the application of antibiotics  TUNGARAZA, C., BRION, N., ROUSSEAU, V., BAEYENS W. AND L. GOEYENS Oceanologia. 45(3), 2003 


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