Simultaneous determination of soluble manganese(III), manganese(II) and total manganese in natural (pore)waters

Application of the electronic spectra of porphyrins for analytical purposes: The effects of metal ions and structural distortions

“…Some methods are based on the simple measurement of UV-Vis absorption of porphyrins (which belong to the strongest light-absorbing chelate ligands [30]), e.g. for mercury(II) [31], other post-transition metal ions (Cd 2+ , Zn 2+ , Pb 2+ , Cu 2+ ) [32], manganese(II) and (III) [33], cobalt(II) (using photolabile cadmium(II) porphyrin) [34]. For detection of platinoid metal ions in trace amounts, an indirect spectrophotometric process was developed by the degradation of water-soluble porphyrins in the reaction with oxidants, catalysed by noble metal ions [35,36].…”

Anammox, denitrification and fixed-nitrogen removal in sediments from the Lower St. Lawrence Estuary

“…Nitrification and denitrification are often tightly coupled near the oxic-anoxic boundary of the sediment with little loss of fixed nitrogen (NO x and NH + 4 ) to the overlying water (Thamdrup and Dalsgaard, 2008). With the recent discovery of anammox in natural environments, the classical view needs to be amended because anammox may serve as a sink for both NH (Luther et al, 1997;Hulth et al, 1999;Madison et al, 2011). These reactions are thermodynamically favorable under a variety of environmental conditions and could be globally important contributors to N cycling (Luther et al, 1997).…”

“…It is unlikely therefore that the supply of reactive Mn(IV) and Fe(III) would have limited Mn(IV) and Fe(III) dependent NH + 4 oxidation during our experiments. We also tested the hypothesis that organically-complexed Mn(III) species, which have recently been discovered in the Black Sea and Chesapeake Bay (Trouwborst et al, 2006) and quantitatively measured in the LSLE sediment porewaters (Madison et al, 2011), could serve as oxidants for NH As with treatment A, neither 29 N 2 nor 30 N 2 were generated during the incubation (Fig. 4), demonstrating that Mn(III)-pyrophosphate is not an effective oxidant of NH + 4 in the LSLE sediments, even at relatively high Mn(III) concentrations.…”

“…More recently, Fe-dependent NH + 4 oxidation has been reported in wetland soils (Clement et al, 2005;Shrestha et al, 2009) and wastewaters (Park et al, 2009), but the veracity of these reports remains untested and their significance is unknown. Porewater profiles in deep Indian Ocean sediments have recently provided indirect evidence for the oxidation of NH Mn(III) species in the anoxic waters of the Black Sea and Chesapeake Bay (Trouwborst et al, 2006) and in the porewaters of the LSLE (Madison et al, 2011) raises the possibility that an additional oxidant, with the thermodynamic potential to oxidize NH + 4 to N 2 , NO − 2 or NO − 3 in the absence of O 2 , may play a role in the N-cycle. Overall, the available evidence for alternative pathways of fixed-N conversion to N 2 is inconclusive and warrants further investigation.…”

A kinetic approach to assess the strengths of ligands bound to soluble Mn(III)

“…During the last decade, there have been several reports of the presence of soluble Mn(III) in the suboxic water column of the Black Sea, the Baltic Sea and the Chesapeake Bay Schnetger and Dellwig, 2012;Trouwborst et al, 2006;Yakushev et al, 2009) as well as in the sediment porewaters of the Laurentian Trough (Madison et al, 2011 and2013). Soluble Mn(III), stabilized by complexation to unknown, natural organic ligands, can potentially serve as both oxidant and reductant in one-electron transfer reactions with other redox species.…”