Dynamics of Zn in an urban wetland soil–plant system: Coupling isotopic and EXAFS approaches

Abstract : Due  to  its  rapid  movement,  preferential  flow  (PF)  in  the  vadose  zone  allows  much  faster  contami-­‐ nant  transport,  which  may  have  a  significant  impact  on  ground-­‐water  quality.  PF  can  occur  in  he-­‐ terogeneous  vadose  zones  and  it  strongly  depends  on  hydric  and  hydraulic  conditions  like  enter-­‐ ing   flow   rates   at   surface.   This   study   deals   with   the   modeling   of   the   establishment   of   PF,   and   re-­‐ lated  solute  transfer  during  the  infiltration  phase  in  a  strongly  heterogeneous  glaciofluvial  deposit.   This   deposit   is   made   of   four   contrasting   lithofacies   (sand,   gravel,   bimodal   gravel   and   matrix-­‐free   gravel)  and  lies  underneath  an  urban  infiltration  basin  (Lyon,  France).  Previous  studies  have  been   carried   out   on   this   site   and   linked   the   regionalization   of   soil   pollution   with   the   lithological   hete-­‐ rogeneity.  But  none  of  them  clearly  demonstrated  how  heterogeneity  could  impact  flow  and  solute   transfer  and  may  explain  such  a  regionalization.  In  this  study,  we  model  flow  and  solute  transfer  at   the  trench  scale  for  both  uniform  and  heterogeneous  profiles  in  order  to  characterize  the  effect  of   lithological  heterogeneity.  In  addition,  such  a  modeling  was  performed  for  two  different  entering   flow   rates   to   depict   the   influence   of   condition   at   surface   on   PF.   A   key   result   is   that   heterogeneity   clearly  impacts  unsaturated  flow  and  solute  transfer.  Numerical  modeling  permitted  pointing  out   the  existence  of  PF  paths  associated  with  the  sedimentary  heterogeneity  of  the  glaciofluvial  depo-­‐ sit.   For   lower   surface   fluxes,   the   sand   lens   and   matrix-­‐free   gravel   were   the   sources   of   capillary   barrier   effects,   leading   to   a   funneled   flow   and   a   groundwater   recharge   characterized   by   earlier   and  more  dispersed  wetting  fronts.  Such  a  flow  pattern  enhances  solutes  transfer  and  reduces  so-­‐ lute  retention  by  soil.  Thus,  the  effect  of  heterogeneity  on  solute  transfer  is  significant,  especially   for  the  most  reactive  solutes.
Type de document :
Article dans une revue
Journal of Water Resource and Protection, Scientific research, 2015, 7, pp.1017-­1028 〈10.4236/jwarp.2015.713083   〉
Liste complète des métadonnées

https://hal-sde.archives-ouvertes.fr/hal-01324917
Contributeur : Nathalie Lyvet <>
Soumis le : mercredi 1 juin 2016 - 16:00:31
Dernière modification le : mardi 16 janvier 2018 - 16:12:46

Identifiants

Collections

Citation

Erij Ben Slimène, Laurent Lassabatere, Thierry Winiarski, . Dynamics of Zn in an urban wetland soil–plant system: Coupling isotopic and EXAFS approaches. Journal of Water Resource and Protection, Scientific research, 2015, 7, pp.1017-­1028 〈10.4236/jwarp.2015.713083   〉. 〈hal-01324917〉

Partager

Métriques

Consultations de la notice

152