Development and optimization of an underwater in-situ cerium bromide spectrometer for radioactivity measurements in the aquatic environment.

A new medium resolution gamma-ray spectrometer consisting of a cerium bromide (CeBr3) crystal (2˝ x 2˝), is developed and optimized for radioactivity measurements in aquatic environments. This apparatus named GeoMAREA (Gamma-ray spectrometer for in-situ Marine Environmental Applications) is designed to control and prevent radio-contaminants in aquatic environments as well as to estimate the variation of natural radionuclides in marine systems for studying oceanographic processes. The system offers activity concentrations in Bq/m3 for detected gamma-ray emitters in the energy range from 150 to 2600 keV, and can provide sequential continuous monitoring data in a stand-alone mode or it can be integrated in stationary/mobile platforms for (near) real-time applications. The photopeak efficiency values were estimated via the MCNPΧ code. Two experimental points were used to validate the theoretical estimations by deploying the system in a water tank with diluted reference sources such us Caesium-137 (137Cs) and Potassium-40 (40K). The system was subsequently deployed in the field along with a conductivity-temperature (CT) sensor, to measure 40K and radon daughters in a region where submarine groundwater discharges (Anavalos, Kiveri, Greece) are present. The experimental calibration data was utilized to provide a first estimation for the background contribution around the photopeak of 40K, attributed to the Cerium Bromide (CeBr3) intrinsic activity.

Shipping routes through core habitat of endangered sperm whales along the Hellenic Trench, Greece: Can we reduce collision risks?

The Mediterranean sperm whale population is listed as 'Endangered". The Hellenic Trench is the core habitat of the eastern Mediterranean sperm whale sub-population that numbers two to three hundred individuals. Major shipping routes running on or very close to the 1000 m depth contour along the Hellenic Trench are causing an unsustainable number of ship-strikes with sperm whales reviewed in this paper. Sperm whale sighting and density data were combined with specific information on the vessel traffic in the area (e.g., types of vessels, traffic patterns, speed and traffic density), in order to estimate the risk of a whale/ship interaction. Routing options to significantly reduce ship strike risk by a small offshore shift in shipping routes were identified. The overall collision risk for sperm whales in the study area would be reduced by around 70%, while a maximum of 11 nautical miles would be added to major routes and only around 5 nautical miles for the majority of ships. No negative impacts were associated with re-routing by shipping away from sperm whale habitat and there would be additional shipping safety and environmental benefits. A significant contribution to the overall conservation status of the marine Natura2000 sites in the area and very important population units of threatened species such as Cuvier's beaked whales, monk seals and loggerhead turtles would be achieved, by the reduction of shipping noise and reduced risk of any oil spills reaching the coasts, which are also important touristic destinations in Greece.

Mobile underwater in situ gamma-ray spectroscopy to localize groundwater emanation from pockmarks in the Eckernförde bay, Germany.

Eckernförde Bay in the Baltic Sea is well-known for the pockmarks areas which are located in the centre and off the southern shore-line of the bay emanating groundwater in a non-continuous but episodic way. Mobile underwater in situ gamma-ray spectroscopy is exploited proving that both 214Bi and 40K are efficient radiotracers for localization of seepage areas whenever either sediment is in mixture with the emanating fluid or resuspension of surface sediment occurs as a side effect of the fluid emanation.

Integration of Underwater Radioactivity and Acoustic Sensors into an Open Sea Near Real-Time Multi-Parametric Observation System.

This work deals with the installation of two smart in-situ sensors (for underwater radioactivity and underwater sound monitoring) on the Western 1-Mediterranean Moored Multisensor Array (W1-M3A) ocean observing system that is equipped with all appropriate modules for continuous, long-term and real-time operation. All necessary tasks for their integration are described such as, the upgrade of the sensors for interoperable and power-efficient operation, the conversion of data in homogeneous and standard format, the automated pre-process of the raw data, the real-time integration of data and metadata (related to data processing and calibration procedure) into the controller of the observing system, the test and debugging of the developed algorithms in the laboratory, and the obtained quality-controlled data. The integration allowed the transmission of the acquired data in near-real time along with a complete set of typical ocean and atmospheric parameters. Preliminary analysis of the data is presented, providing qualitative information during rainfall periods, and combine gamma-ray detection rates with passive acoustic data. The analysis exhibits a satisfactory identification of rainfall events by both sensors according to the estimates obtained by the rain gauge operating on the observatory and the remote observations collected by meteorological radars.

Automated quantitative analysis of in-situ NaI measured spectra in the marine environment using a wavelet-based smoothing technique.

An algorithm for automated analysis of in-situ NaI γ-ray spectra in the marine environment is presented. A standard wavelet denoising technique is implemented for obtaining a smoothed spectrum, while the stability of the energy spectrum is achieved by taking advantage of the permanent presence of two energy lines in the marine environment. The automated analysis provides peak detection, net area calculation, energy autocalibration, radionuclide identification and activity calculation. The results of the algorithm performance, presented for two different cases, show that analysis of short-term spectra with poor statistical information is considerably improved and that incorporation of further advancements could allow the use of the algorithm in early-warning marine radioactivity systems.