Speciation

Glacial erosion processes suspected to enhance the lability of particulate iron, with a strong influence on the biological demand in the subantarctic waters

As part of the GEOTRACES process study HEOBI (GIpr05) van der Merwe and co-workers (2019, see reference below) conducted a thorough characterization of the labile and refractory iron phases of the particles discharged to the local seawater by the glacial erosion and rivers of Heard and Mc Donald islands (Southern Indian Ocean). They demonstrate that, together […]

Dec / 16 / 2019

Glacial erosion processes suspected to enhance the lability of particulate iron, with a strong influence on the biological demand in the subantarctic waters

As part of the GEOTRACES process study HEOBI (GIpr05) van der Merwe and co-workers (2019, see reference below) conducted a thorough characterization of the labile and refractory iron phases of the particles discharged to the local seawater by the glacial erosion and rivers of Heard and Mc Donald islands (Southern Indian Ocean). They demonstrate that, together […]

Oct / 08 / 2019

Up to four mercury species measured along the GEOTRACES East Pacific Zonal Transect

Total mercury (HgT), elemental mercury (Hg0), monomethyl-mercury (MMHg), and dimethyl-mercury (DMHg) were measured at an unprecedent resolution so far along the East Pacific Zonal Transect (EPZT) GEOTRACES cruise (GP16). Knowing that MMHg is a neurotoxin that accumulates in the trophic chain, establishing the full speciation of this element is required in order to better understand […]

Jan / 16 / 2017

Dealing with the chemical speciation of the elements in the different oceanic realms

First paper of the SCOR working group on modelling chemical speciation in seawater (WG145) The form in which a trace element or other component of seawater is present, and its tendency to react, depends on its activity which is a complex function of temperature, pressure, salinity and often pH. The most widely used equations that […]

Oct / 04 / 2016

All mercury species measured along the GEOTRACES-UK section, South Atlantic Ocean

Total mercury (THg), methylated mercury (MeHg), and dissolved gaseous mercury (DGM) concentrations were determined along 40°S in the Atlantic Ocean. All Hg species had higher concentrations in western than in eastern basin, although they are at the ultra-low femtomolar level. MeHg increases with lower oxygen concentration, substantiating that microbial respiration of organic matter stimulates MeHg […]

May / 13 / 2016

Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean

Understanding persistent high levels of mercury in arctic biota has been an elusive goal for nearly two decades. Little is known about where exactly inorganic Hg inputs into the Arctic generate the toxic methylmercury (MeHg) form that bioaccumulates in biota. Lars-Eric Heimbürger and colleagues (2015, see reference below) present the first full-depth high resolution profiles […]

May / 20 / 2015

Large amounts of soluble manganese(III) identified at the land-ocean interface

Soluble manganese(III) [Mn(III)] is a phase traditionally considered non important in aqueous redox reactions. However, applying a spectrophotometric method sensitive to Mn oxidation state, Madison and co-authors found that up 90% of the Mn in porewater collected from sediment cores in the St. Lawrence Estuary is soluble Mn(III). The authors conclude that the conceptual model […]

Oct / 28 / 2013

Arsenic detoxification by phytoplankton reveals that arsenic species could be good proxies of phosphorus limitation

Some phytoplankton species have the capacity to modify surface water arsenic speciation, inhibiting its toxicity. Such detoxification is operative in oligotrophic waters when phosphate concentrations are below those for arsenic (As). During the US GEOTRACES North Atlantic transect, fine determination of As speciation allowed establishing the potential use of these detoxification products as indicators of […]

Mar / 26 / 2013

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