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Falling lead levels in Mediterranean

GEODYME, a project supported by the European Community's RTD programme in the field of Marine Science and Technologies (MAST), has detected falling lead levels in the Mediterranean, due primarily to fewer lead additives in petrol and the increased use of green fuels.

The main...
GEODYME, a project supported by the European Community's RTD programme in the field of Marine Science and Technologies (MAST), has detected falling lead levels in the Mediterranean, due primarily to fewer lead additives in petrol and the increased use of green fuels.

The main aim of GEODYME (Geochemistry and dynamics of the Mediterranean) was to obtain physical and chemical data in order to detect changes in the deep water characteristics. From this, the project team hoped to be able to gain greater knowledge of the impact of changes in climate and the environment on the sea. Parameters such as temperature, salt concentration or salinity, nutrient, oxygen and trace-metal content of the water were monitored.

The main research-gathering undertaken by the project team was carried out during two oceanographic cruises in 1994 and 1995, in the Western and Eastern Mediterranean. The main objectives included quantifying the major species of phytoplankton. Two new complementary methods for analysing phytoplankton were used by the GEODYME project.

Among the results of the comparison of the GEODYME results with earlier results is an indication that both temperature and salinity of the Mediterranean is increasing. The researchers suggest that this is due, respectively, to the greenhouse effect and to a reduction in the freshwater discharged by rivers, because of damming, for example.

Nutrient levels have also increased, with the survey showing that phosphate and nitrate concentrations in the water are increasing by 0.4 to 0.5% per year. This corresponds to a 3% increase per year in atmospheric or terrestrial discharge into the sea since the 1960s. The researchers fear that, if this rate of increase continues, oxygen levels will be depleted, leading to losses in marine life.

Analysis of trace metal profiles in the Mediterranean shows an annual increase of 6% for zinc and lead, and 2% for copper and cadmium between 1960 and 1985. Since then, however, the concentration of lead in the surface water has reduced by half. This is the result of the increased use of unleaded fuels.

The results obtained by the project to date demonstrate the importance of the Mediterranean in assessing the marine biosphere's response to environmental changes. These results will extend understanding of the processes involved. Furthermore, the Mediterranean could be used as an early-warning device to detect possible consequences from global changes before they become apparent worldwide.

Source: VIPS Scientific Press Service

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