The CoastColour Round Robin datasets: a database to evaluate the performance of algorithms for the retrieval of water quality parameters in coastal waters

The CoastColour project Round Robin (CCRR) project (http://www.coastcolour.org) funded by the European Space Agency (ESA) was designed to bring together a variety of reference datasets and to use these to test algorithms and assess their accuracy for retrieving water quality parameters. This information was then developed to help end-users of remote sensing products to select the most accurate algorithms for their coastal region. To facilitate this, an inter-comparison of the performance of algorithms for the retrieval of in-water properties over coastal waters was carried out. The comparison used three types of datasets on which ocean colour algorithms were tested. The description and comparison of the three datasets are the focus of this paper, and include the Medium Resolution Imaging Spectrometer (MERIS) Level 2 match-ups, in situ reflectance measurements and data generated by a radiative transfer model (HydroLight). The datasets mainly consisted of 6,484 marine reflectance associated with various geometrical (sensor viewing and solar angles) and sky conditions and water constituents: Total Suspended Matter (TSM) and Chlorophyll-a (CHL) concentrations, and the absorption of Coloured Dissolved Organic Matter (CDOM). Inherent optical properties were also provided in the simulated datasets (5,000 simulations) and from 3,054 match-up locations. The distributions of reflectance at selected MERIS bands and band ratios, CHL and TSM as a function of reflectance, from the three datasets are compared. Match-up and in situ sites where deviations occur are identified. The distribution of the three reflectance datasets are also compared to the simulated and in situ reflectances used previously by the International Ocean Colour Coordinating Group (IOCCG, 2006) for algorithm testing, showing a clear extension of the CCRR data which covers more turbid waters.

(Table 6) Sulfate ion concentration and alkalinity in interstitial waters from bottom sediments of Core DM9-666, Gulf of California

New data on phosphorites collected by dredging and trawling at depths from 2700 to 520 m in the open Atlantic Ocean (i.e. outside of the shelf and the continental slope) are reported. Aphanitic, granular, brecciated, and conglomerate-like types are distinguished among the phosphorites. A comparison of the studied phosphorites with ones from the Atlantic shelf of Africa and from seamounts of other oceans is made.

Ion balance in waters through inductively coupled plasma optical emission spectrometry

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) has been employed to carry out the determination of both major anions and cations in water samples. The anion quantification has been performed by means of a new automatic accessory. In this device chloride has been determined by continuously adding a silver nitrate solution. As a result solid silver chloride particles are formed and retained on a nylon filter inserted in the line. The emission intensity is read at a silver characteristic wavelength. By plotting the drop in silver signal versus the chloride concentration, a straight line is obtained. As regards bicarbonate, this anion has been on-line transformed into carbon dioxide with the help of a 2.0 mol L−1 nitric acid stream. Carbon signal is linearly related with bicarbonate concentration. Finally, information about sulfate concentration has been achieved by means of the measurement of sulfur emission intensity. All the steps have been simultaneously and automatically performed. With this setup detection limits have been 1.0, 0.4 and 0.09 mg L−1 for chloride, bicarbonate and sulfate, respectively. Furthermore, it affords good precision with RSD below 6 %. Cation (Ca, Mg, Na and K) concentration, in turn, has been obtained by simultaneously reading the emission intensity at characteristic wavelengths. The obtained limits of detection have been 8 × 10−3, 2 × 10−3, 8 × 10−4 and 10−2 mg L−1 for sodium, potassium, magnesium and calcium, respectively. As regards sample throughput, about 30 samples h−1 can be analysed. Validation results have revealed that the obtained concentrations for these anions are not significantly different as compared to the data provided by conventional methods. Finally, by considering the data for anions and cations, precise ion balances have been obtained for well and mineral water samples.