Gregory Messiaen

Atmospheric concentrations, occurrence and deposition of persistent organic pollutants (POPs) in a Mediterranean coastal site (Etang de Thau, France)

Atmospheric concentrations and deposition fluxes of PCDD/F and PCB have been evaluated over a 1-year period in a Mediterranean coastal lagoon (Etang de Thau, France). Indicative PBDE air concentrations in the hot season are also reported in this work. ∑2,3,7,8-PCDD/Fs and ∑18PCBs (gas+particulate) air concentrations ranged from 67 to 1700 fg m(-3) and from 13 to 95 pg m(-3), respectively whereas ∑8PBDEs (gas+particulate) summer time levels varied from 158 to 230 pg m(-3). The PCDD/F and PCB atmospheric occurrence over Thau lagoon and subsequent inputs to the surface waters are determined by an assemble of factors, being the seasonality of atmospheric concentration, the air mass origin and meteorological conditions important drivers. Total (wet+dry) ∑2,3,7,8-PCDD/Fs and ∑18PCBs deposition fluxes to Thau Lagoon waters are 117 and 715 pg m(-2)d(-1), respectively.

Evaluation of the lake model FLake over a coastal lagoon during the THAUMEX field campaign

The THAUMEX measurement campaign, carried out during the summer of 2011 in Thau, a coastal lagoon in southern France, focused on episodes of marine breezes. During the campaign, three intensive observation periods (IOPs) were conducted and a large amount of data were collected. Subsequently, standalone modelling using the FLake lake model was used, first to assess the surface temperature and the surface energy balance, and second to determine the energy budget of the water column at the measurement site. Surface fluxes were validated against in situ measurements, and it was determined that heat exchanges are dominated by evaporation. We also demonstrated that the model was sensitive to the light extinction coefficient at Thau, due to its shallowness and clarity nature. A heat balance was calculated, and the inclusion of a radiative temperature has improved it, especially by reducing the nocturnal evaporation. The FLake lake model was then evaluated in three-dimensional numerical simulations performed with the Meso-NH mesoscale model, in order to assess the changing structure of the boundary layer above the lagoon during the IOPs more accurately. We highlighted the first time ever when Meso-NH and FLake were coupled and proved the ability of the coupled system to forecast a complex phenomenon but also the importance of the use of the FLake model was pointed out. We demonstrated the impact of the lagoon and more precisely the Lido, a sandy strip of land between the lagoon and the Mediterranean Sea, on the vertical distribution of turbulent kinetic energy, evidence of the turbulence induced by the breeze. This study showed the complementarities between standalone and coupled simulations.

Marine environmental station database of Thau lagoon

On oyster table in the Thau lagoon, Ifremer measures hydrological parameters (temperature, salinity) at high-frequency .Data loggers (NKE: SMATCH and STPS) measure every 15 minutes. To limit biofouling, there is a localized chlorination at the sensor (SMATCH) and a regular rotation of data loggers (STPS). The brand of sensors is WTW. These devices are calibrated regularly with a connection to ITS90 for temperature and IAPSO standards for salinity. The data are qualified by calibrations in the laboratory. For salinity, calibrations in-situ (since 2015) and comparisons between sensors are also conducted. A maximum permissible deviation (EMT) is calculated with the data, taking into account the error of accuracy and the measurement uncertainty (k=2).