@article{fdi:010061828,
  title = {{F}ate of colloids during estuarine mixing in the {A}rctic},
  author = {{P}okrovsky, {O}. {S}. and {S}hirokova, {L}. {S}. and {V}iers, {J}. and {G}ordeev, {V}. {V}. and {S}hevchenko, {V}. {P}. and {C}hupakov, {A}. {V}. and {V}orobieva, {T}. {Y}. and {C}andaudap, {F}. and {C}ausserand, {C}. and {L}anzanova, {A}ur{\'e}lie and {Z}ouiten, {C}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he estuarine behavior of organic carbon ({OC}) and trace elements ({TE}) was studied for the largest {E}uropean sub-{A}rctic river, which is the {S}evernaya {D}vina; this river has a deltaic estuary covered in ice during several hydrological seasons: summer ({J}uly 2010, 2012) and winter ({M}arch 2009) baseflow, and the {N}ovember-{D}ecember 2011 ice-free period. {C}olloidal forms of {OC} and {TE} were assessed for three pore size cutoffs (1, 10, and 50 k{D}a) using an in situ dialysis procedure. {C}onventionally dissolved (< 0.22 mu m) fractions demonstrated clear conservative behavior for {L}i, {B}, {N}a, {M}g, {K}, {C}a, {S}r, {M}o, {R}b, {C}s, and {U} during the mixing of freshwater with the {W}hite {S}ea; a significant (up to a factor of 10) concentration increase occurs with increases in salinity. {S}i and {OC} also displayed conservative behavior but with a pronounced decrease in concentration seawards. {R}ather conservative behavior, but with much smaller changes in concentration (variation within +/- 30%) over a full range of salinities, was observed for {T}i, {N}i, {C}r, {A}s, {C}o, {C}u, {G}a, {Y}, and heavy {REE}. {S}trong non-conservative behavior with coagulation/removal at low salinities (< 5 parts per thousand) was exhibited by {F}e, {A}l, {Z}r, {H}f, and light {REE}. {F}inally, certain divalent metals exhibited non-conservative behavior with a concentration gain at low (similar to 2-5 parts per thousand, {B}a, {M}n) or intermediate (similar to 10-15 parts per thousand, {B}a, {Z}n, {P}b, {C}d) salinities, which is most likely linked to {TE} desorption from suspended matter or sediment outflux. {T}he most important result of this study is the elucidation of the behavior of the 'truly' dissolved low molecular weight {LMW} < 1 k{D}a fraction containing {F}e, {OC}, and a number of insoluble elements. {T}he concentration of the {LMW} fraction either remains constant or increases its relative contribution to the overall dissolved (< 0.22 mu m) pool as the salinity increases. {S}imilarly, the relative proportion of colloidal (1 k{D}a-0.22 mu m) pool for the {OC} and insoluble {TE} bound to ferric colloids systematically decreased seaward, with the largest decrease occurring at low (< 5 parts per thousand) salinities. {O}verall, the observed decrease in the colloidal fraction may be related to the coagulation of organo-ferric colloids at the beginning of the mixing zone and therefore the replacement of the {HMW}1 k{D}a-0.22 mu m portion by the {LMW} < 1 k{D}a fraction. {T}hese patterns are highly reproducible across different sampling seasons, suggesting significant enrichment of the mixing zone by the most labile (and potentially bioavailable) fraction of the {OC}, {F}e and insoluble {TE}. {T}he size fractionation of the colloidal material during estuarine mixing reflects a number of inorganic and biological processes, the relative contribution of which to element speciation varies depending on the hydrological stage and time of year. {I}n particular, {LMW} < 1 k{D}a ligand production in the surface horizons of the mixing zone may be linked to heterotrophic mineralization of allochthonous {DOM} and/or photodestruction. {G}iven the relatively low concentration of particulate versus dissolved load of most trace elements, desorption from the river suspended material was less pronounced than in other rivers in the world. {A}s a result, the majority of dissolved components exhibited either conservative ({OC} and related elements such as divalent metals) or non-conservative, coagulation-controlled ({F}e, {A}l, and insoluble {TE} associated with organo-ferric colloids) behavior. {T}he climate warming at high latitudes is likely to intensify the production of {LMW} < 1 k{D}a organic ligands and the associated {TE}; therefore, the delivery of potentially bioavailable trace metal micronutrients from the land to the ocean may increase.},
  keywords = {{ARCTIQUE}},
  booktitle = {},
  journal = {{O}cean {S}cience},
  volume = {10},
  numero = {1},
  pages = {107--125},
  ISSN = {1812-0784},
  year = {2014},
  DOI = {10.5194/os-10-107-2014},
  URL = {https://www.documentation.ird.fr/hor/fdi:010061828},
}