Scientists have found particularly high concentrations of mercury in the Mediterranean Basin. Marine animals found in the Mediterranean Basin have high mercury levels compared to similar species from most parts of the Atlantic because of the natural presence of mercury from volcanic activity. About half of world mercury resources are located in the Mediterranean area. Mining in the area has increased the release of mercury into the environment. The process of biomagnification in the Mediterranean Basin is evident (http://www.westonaprice.org/envtoxins/mercury.html). High levels of mercury are found in the Mediterranean tuna compared to similar species in most parts of the Atlantic, as well as in smaller species such as anchovy and sardines, and also in local marine birds and their eggs. An investigation of fishermen and their families in coastal villages on the north Tyrrhenian Sea found a correlation between the number of seafood meals and the mercury levels from hair samples.

The following document presents major findings of four ELOISE projects (MAMCS, MOE) and the MED-OCEANOR programme funded by the Italian National Research Council (CNR) to support part of field investigations of the MAMCS project. The projects provide major results of these projects on different patterns involved in the dynamics of atmospheric pollutants in the Marine Boundary Layer (MBL) of e.g. the Mediterranean Sea, chemical and physical mechanisms in the lower atmosphere and sea water, atmospheric transport and deposition as well as gaseous exchanges at the air–water interface with changing meteorological conditions, and sampling and analytical techniques used to determine ambient levels of trace contaminants in the air and water samples.

The vertical profiles of DGM measured in the Mediterranean basin revealed that the concentration generally increases with depth (Ferrara et al. 2003). This finding indicates that DGM is produced not only in surface water as a consequence of photo-induced reactions, but also in deep water as a consequence of bacterial and/or geochemical activity. Volatile forms of mercury diffuse from the deep to the surface waters and then partially pass to the atmosphere. DGM concentrations and mercury evasion in surface water in the Western Mediterranean basin were lower than that observed in the Eastern basin. The maximum was found in the Strait of Sicily. The observed differences between the two basins may be explained by different biochemical scenarios. (Ferrara et al. 2003, Gårdfeldt et al. 2003).

Measurements performed during summer and early spring season at off shore as well as coastal sites consistently demonstrated that maximum solar radiation at midday coincided with maximum DGM concentration. During nights DGM concentrations were generally lower compared to the concentrations measured during daylight. Hence, a diurnal variation has been demonstrated in the off shore waters as well as the coastal sites investigated during the cruises (Andersson et al., 2004).

Results from MAMCS and MOE on simultaneous measurements on mercury in Europe, showed that observed concentrations of total gaseous mercury (TGM), particulate mercury (TPM), and reactive gaseous mercury (RGM) were generally slightly higher in the Mediterranean region than in Northwest Europe (Wangeberg et al., 2001).

The RGM formation in the Marine Boundary Layer (Sprovieri et al. 2003; Hedgecock et al. 2003; Hedgecock and Pirrone, 2001) is:

• driving the deposition processes of RGM to the sea
• affecting the cycling/exchange of Hg species between the atmosphere and the seawater
• the key to all chemical processes in gaseous, aqueous and heterogeneous phases that may drive the formation of oxidized mercury and transform elemental Hg to oxidized Hg

Also physical processes are very important with reference to the gas-particle partitioning of gaseous mercury with suspended particulate matter in the atmosphere. Obviously this process depends very much by meteorology (temperature, relative humidity, radiation) and particle composition Enriched particles with EC are certainly the main factor that brings gaseous elemental mercury onto the particle and therefore is deposited faster to the surface.

As a part of the MED-OCEANOR project the spatial and temporal distributions of mercury species along a 6000 km cruise path in the western and eastern sector of the Mediterranean Sea were studied for the first time. Simultaneous measurements of two atmospheric mercury species Hg0 and RGM were performed in order to investigate the dynamic patterns of mercury in the Marine Boundary Layer. Hg0 ranged between 0.4 and 11.2 ng m −3 with an average of 1.9±1.02 ng m −3 over the entire period. Higher concentrations were observed in the Gulf of Naples due primarily to air masses transported from the mainland reflecting the contribution from anthropogenic sources. RGM concentrations varied from 0.2 to 30.1 pg m −3 with an average of 7.9 pg m −3. A diurnal cycle of the RGM concentration was observed during the entire sampling period with the maximum around midday and the minimum during the night; the oxidation by daytime oxidants, i.e., OH, may have determined the observed diurnal cycle of RGM concentration in the MBL. The data set has been used by Hedgecock et al. to validate the mercury chemical model developed in MAMCS. The model has aimed to evaluate the dynamics of mercury in the MBL of the Mediterranean Sea.