El pasado mes de Diciembre, dentro del marco del Proyecto EACFe, se presentó un trabajo en el congreso AGU FALL MEETING, celebrado en San Francisco (USA). El trabajo se tituló: Kinetic model to explain the effect of ocean warming and acidification on the Fe(II) oxidation rate in oligotrophic and eutrophic natural waters.
Este trabajo presenta el comportamiento
del Fe(II) en diversos escenarios de acidificación oceánica y calentamiento
global. Asi, se presentaron las contribuciones de las especies cinéticamente
activas de Fe(II) a la constante de oxidación global de Fe(II) en agua de mar.
A continuación se muestra el resumen del
trabajo (en inglés).
The
speciation of inorganic Fe(II) as a function of the pH and temperature have
been modeled in order to elucidate the inorganic Fe(II) redox behavior over a
wide range of scenarios of acidification and global warming of the upper ocean,
as well as, changes due to natural ambient fluctuations of pH and temperature.
In addition, a kinetic modeling approach has been carried out to elucidate the
fractional contribution of most kinetically active Fe(II) species to the overall
oxidation rate to improve our future and present knowledge with respect to redox
iron chemistry in the marine systems. The kinetic model considers the
interactions of Fe(II) with the major ions in seawater, including phosphate and
silicate and the competition with copper with the ROS. The model has been
applied to the experimental results in order to describe the effect of
temperature and pH in the speciation of Fe(II) and to compute the fractional
contribution of each Fe(II)specie to the overall oxidation rate.
The
oxidation rates (kapp) of
nanomolar levels of Fe(II) have been studied in seawater enriched with
nutrients (SWEN) in air saturated conditions. The nutrient effect (nitrate,
phosphate and silicate), on the oxidation of Fe(II), has been evaluated as a
function of pH (7.2-8.2), temperature (5-35 ºC) and salinity (10-37.09). The
oxidation of Fe(II) was faster in the presence of nutrient with the change in
the Fe(II) oxidation rates (Δlogkapp) more intensive at
higher temperatures over the entire pH range studied.
From
the model it can be observed that the inorganic speciation of Fe(II) is
controlled largely by pH, either in SW or in SWEN. A greater presence of Fe-nutrient
reactive species (FeH3SiO4+ and FePO4-)
in SWEN at higher temperatures explained
the changes in the oxidation process. The individual oxidation rates by oxygen,
for the Fe(II) most kinetically
active species (Fe2+, FeOH+, Fe(OH)2, FeCO3(OH)-,
FeCO3, Fe(CO3)22-, FeH3SiO3+,
FePO4-), were fitted as a function of the temperature.