Jane Sanjuan

Tin contamination in Arcachon Bay: Effects on oyster shell anomalies

Abstract Total tin and organotin levels in both sea water and in oysters (C. gigas) from Arcachon Bay, and the frequency of shell anomalies have been monitored since the ban, in January 1982, of organotin compounds in antifouling paints. The results show that at the end of the survey period in November 1985, tin levels in areas of organotin input were 5 to 10 times lower than those found in 1982. The decrease in contamination of cultivated oysters has been particularly obvious since August 1984, when organotin concentrations found in oyster samples were less than 0.2 μg kg−1. The decrease in the incidence and extent of anomalies in calcification mechanisms in oysters (chambers) was particularly notable during this period and seemed to be correlated with the decrease in tin contamination of the waters of Arcachon Bay.

Monitoring and assessement of butyltins in Atlantic coastal waters

Tributyltin and its degradation products were measured in seawater samples in 1986–1987 at different locations of the French Atlantic coast, including marinas and oyster culture areas. Concentrations were in the range of <2-1 500 ng TBT l−1, <1–194 ng DBT l−1, and <1–200 ng MBT l−1. In Arcachon Bay, the results showed that there was a good agreement between TBT levels in seawater and the frequency of oyster shells anomalies monitored at the same time.

The distribution and cycling of mercury species in the western Mediterranean

Total mercury concentrations were determined in water samples from ten vertical profiles in the western Mediterranean. Most Hg concentrations ranged from 0.5 to 4 pM, with a geometric mean of 2.26 pM. Such concentrations are in the same range as those measured in the North Atlantic and equatorial Pacific waters. There is no indication that the presence of geothermal activity or cinnabar deposits around the Mediterranean basin induces higher mercury concentrations in waters. Vertical concentration profiles were characterized by a maximum just below the thermocline, which is mainly developed in regions with relatively high primary production in the overlying waters. These observations support the remobilization model according to which, the mercury, associated with degradable organic matter, is solubilized from the particles accumulated in the thermocline layer. Additional measurements of certain mercury species, including reactive mercury (HgR) and gaseous species [elemental mercury (Hg°) and dimethylmercury (DMHg)], were performed on three profiles in the Alboran Sea and the Strait of Gibraltar. While 50% of the total mercury consisted of unidentified organic association, a maximum of the three determined species were observed below the thermocline: up to 0.71 pM, 0.43 pM and 0.30 pM for HgR, Hg° and DMHg, respectively. DMHg and Hg° appear to be formed in the low oxygen zone. A specific methylation rate of 3 × 10−9 s−1 can be estimated, which is six times higher than the values proposed for the North Atlantic waters (Mason et al., 1995a, Water, Air and Soil Pollution, 80, 665–677). The mass balance budget in the western Mediterranean shows that, while the total mercury exchanges at the straits are not unbalanced, mercury enters the Mediterranean as inorganic mercury and is exported to the Atlantic Ocean partially as methylated species. Riverine input is mainly composed by particulate mercury which is readily accumulated in coastal sediments. The dissolved mercury flux from non-marine sources is largely dominated by atmospheric deposition, which is one order of magnitude higher than riverine input. The mercury accumulation rate in the sediments is quantitatively equivalent to the atmospheric inputs, but mainly constituted by terrestrial material deposited nearshore. On the basis of ☐-core analyses and the global model of Mason et al. (1994a, Geochimica et Cosmochimica Acta, 58, 3191–3198) and present results the pre-industrial Hg riverine, atmospheric and sedimentation fluxes are estimated to have been about one-third the current one.

Speciation and sorption of mercury in two macro-tidal estuaries

Mercury speciation and partition were determined in two macro-tidal estuaries, the Loire and the Seine estuaries (France) during several cruises covering various hydrological conditions. Additional measurements were performed in freshwaters in order to assess temporal variations of mercury inputs to the estuaries during an annual cycle. In freshwater, average total ‘dissolved’ (< 0.8 μm) mercury concentration [(HgT)D] was 4.1 ± 2.1 pM in the Loire and 11.5 ± 9.7 pM in the Seine. Mean particulate mercury concentration [(HgT)p] was 0.95 ± 0.63 nmol g−1 in the Loire and 5.4 ± 2.6 nmol g−1 in the Seine. The seasonal variation in the mercury concentrations in the two rivers are interpreted in terms of changes in the various water sources during flood events and variable contribution of colloidal materials. In the estuarine parts, (HgT)D concentrations generally varied from 2 to 6 pM in the Seine and from 1 to 3 pM in the Loire, while (HgT)P concentrations varied between 0.5 and 5 nmol g−1 in the Loire and between 2.5 and 10 nmol g−1 in the Seine. Because of its high distribution coefficient (log Kd = 5–6) and the high turbidity of these environments, mercury is mainly transported in particulate form in freshwaters as well as in mixing zones. Relationships between Kd and concentrations of suspended particles, dissolved and particulate organic carbon allow to describe the partition of mercury between solid and dissolved phases in terms of colloids, organic complexation in solution and sorption processes. Chlorocomplex formation does not play the major role in the speciation of Hg during the estuarine mixing. Organic associations, through sulphydryl groups, seems to be the dominant processes governing mercury distribution and partition in the two macro-tidal estuaries studied. Primary production appears to play an important role in the mercury dynamic. (HgT)P is correlated with the chlorophyll content of the particles in high flow regime of the Loire river, while elemental mercury (Hg0) was found to be related to the oxygen saturation rate in both estuaries. The production of Hg0 was sufficient to sustain a significant evasion flux to the atmosphere. Dimethylmercury was detected at fentomolar level during one cruise in the Baie de la Seine during an hypoxia episode. Highest monomethylmercury concentrations (up to 4% of the HgT) were associated with warmer and organic rich freshwater. Candidate sources for methylated mercury species are discussed. Both estuaries appear to be affected by local anthropogenic inputs. However, the Seine river is more deeply impacted by human activities. Watershed yields of the total Hg were calculated for the two drainage basins. The Seine yield (41 mmol km−2 a−1) is in the range of what is found in other urban areas, while for the Loire (9 mmol km−2 a−1) it is close to values found for agricultural watersheds. In spite of the anthropogenic inputs within the two estuaries, the riverine dissolved mercury inputs to the adjacent coastal waters (la Baie de la Seine and le Grand estuaire de la Loire) have been estimated to be half of the corresponding atmospheric depositions.

Dimethylmercury formation in the Alboran Sea

Abstract The distribution of dissolved gaseous dimethylmercury (DMHg) was studied in three vertical profiles in the waters of the Alboran Sea and the adjacent Strait of Gibraltar. The shape of these profiles suggests a sub-thermocline source of this species in the low oxygen region of the Alboran Sea. Methylation of mercury apparently occurs as a result of bacterial activity. Unstable and volatile DMHg is advected toward the Gibraltar Strait with outflowing Mediterranean waters and then decomposes and/or escapes into the atmosphere. The existence of this sub-thermocline reservoir of DMHg could lead to the accumulation of methyl-mercury in deep pelagic fish.

Mercury transport in waters of the strait of dover

The purpose of this work as part of the FluxManche EC Project (MAST-1) was to obtain accurate data on the concentrations and distributions of dissolved and particulate mercury which, together with determinations of suspended matter and water transport, can provide estimates of fluxes through the Strait of Dover. Samples were collected every other month between September 1990 and December 1991 at six stations, two depths being sampled at each station, on a transect between Folkestone and Cap Griz-Nez. Data concentrations were log-normal distributed. Geometric means were 2.65 and 3.36 pM for dissolved and particulate mercury, respectively. Mercury linked to particles constituted between 20 and 97% of total mercury, with the highest proportions being found near the coast similarly to the distribution pattern of particulate matter along the transect. On the basis of water and suspended particulate matter transports, estimated mercury fluxes from the English Channel to the North Sea were 1.8 and 2.3 t a−1 for dissolved and particulate mercury, respectively.

Automated technique for mercury determination at sub-nanogram per litre levels in natural waters

A sensitive and automatic technique for dissolved mercury determination has been developed in order to produce rapid and accurate dissolved mercury determinations in natural waters at ambient levels. This is needed for building realistic mass balance budgets and providing more accurate data in monitoring programmes for this metal. The detection limit obtained with a 45 ml sample was 0.1 ng l–1. The precision of the method over the range 0.5–50 ng l–1 was found to be approximately 5%. Eight samples per hour can be analysed without carryover effects. The instrumentation is very robust but strict control measures are required to ensure a mercury-free environment around the instrumentation.