Cheize M. auteur aut IRD Sarthou G. auteur aut IRD Croot P. L. auteur aut IRD Bucciarelli Eva auteur aut IRD Baudoux A. C. auteur aut IRD Baker A. R. auteur aut IRD text journalArticle eng text/pdf born digital access A sensitive method using Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-ACSV) has been developed to determine for the first time iron (Fe) organic speciation in rainwater over the typical natural range of pH. We have adapted techniques previously developed in other natural waters to rainwater samples, using the competing ligand 1-nitroso-2-naphthol (NN). The blank was equal to 0.17 +/- 0.05 nM (n = 14) and the detection limit (DL) for labile Fe was 0.15 nM which is 10-70 times lower than that of previously published methods. The conditional stability constant for NN under rainwater conditions was calibrated over the pH range 5.52-6.20 through competition with ethylenediaminetetraacetic acid (EDTA). The calculated value of the logarithm of beta'(FE3+(NN)3) increased linearly with increasing pH according to log beta'(FE3+(NN)3) = 2.4 +/- 0.6 x pH + 11.9 +/- 3.5 (salinity =2.9, T= 20 degrees C). The validation of the method was carried out using desferrioxamine mesylate B (DFOB) as a natural model ligand for Fe. Adequate detection windows were defined to detect this class of ligands in rainwater with 40 mu M of NN from pH 5.52 to 6.20. The concentration of Fe-complexing natural ligands was determined for the first time in three unfiltered and one filtered rainwater samples. Organic Fe-complexing ligand concentrations varied from 104.2 +/- 4.1 nM equivalent of Fe(III) to 336.2 +/- 19.0 nM equivalent of Fe(III) and the logarithm of the conditional stability constants, with respect to Fe3+, varied from 21.1 +/- 0.2 to 22.8 +/- 0.3. This method will provide important data for improving our understanding of the role of wet deposition in the biogeochemical cycling of iron. specialized Iron organic speciation Natural rainwater Voltammetry Iron-complexing natural ligand concentrations Conditional stability constants 032 062 020 736 45-54 2012 0003-2670 https://www.documentation.ird.fr/hor/fdi:010057073 10.1016/j.aca.2012.05.011 0003-2670 [F B010057073] https://www.documentation.ird.fr/hor/fdi:010057073 https://www.documentation.ird.fr/intranet/publi/2012/08/010057073.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2012-09-03 2017-08-23 fdi:010057073 fre