ABSTRACT
Factors controlling ocean acidification and its temporal variations were studied over the 1995-2011 period at the Dyfamed site at 10 m depth, in the North Mediterranean Sea. The results indicated a mean annual decrease of 0.003 ± 0.001 pH units on the seawater scale. The seasonal variability was characterized by a pH decrease during springtime and a strong pH increase in late fall. Anthropogenic CO2 (CANT) absorption by the ocean was the key driver of seawater acidification in this region, accounting for about 70% of the observed drop in pH, followed by water temperature (about 30%). The total inorganic carbon (CT) data showed a CT increase of 30.0 ± 1.0 µmol kg(-1) per decade. This decadal increase is mainly due to the CANT penetration (43.2 µmol kg(-1) per decade) in surface waters, which is mitigated for by relatively small opposing changes in CT due to physical and biological processes.
Subject(s)
Environmental Monitoring , Seasons , Seawater/chemistry , Carbon Dioxide/metabolism , Hydrogen-Ion Concentration , Mediterranean Sea , Temperature , Time FactorsABSTRACT
We describe a new method for the spectroscopic determination of high calcium concentration using a fluorescent probe Rhod-5N. This method was investigated in order to be utilized in high ionic strength solution, such as seawater. The probe is fluorescent when bound to calcium, LM, but not as the free form L. The dissociation constant of the equilibrium (0.14mM) was determined at several ionic strengths, i.e. in the absence and in the presence of additional ions (0.7M NaCl). The influence of pH was studied. In order to correctly model the experimental data, we included a new fluorescent compound: LHM (calcium bound protonated probe). The first acidity constant (0.02muM) and the second dissociation constant (4.5mM) were calculated. A useful range for the determination of calcium concentration is provided. Such a method is fast and easy to carry out.
