title: Performance of Eleocharis macrostachya and its importance for arsenic retention in constructed wetlands.
abstract: BACKGROUND
  Arsenic (As) can be removed from water via rhizofiltration using phytostabilizing plants. The aim of this study was to investigate the performance of Eleocharis macrostachya in constructed wetland prototypes, as well as the plant's arsenic mass retention and the distribution of As along the wetland flow gradient and the soil in the wetland mesocosmos.
  
  
  METHODS
  Experiments were carried out in laboratory-scale wetland prototypes, two planted with E. macrostachya and one without plants. Samples of water were taken at the inlet and outlet of the wetlands during the 33-week test period. At the end of the experiment, plants and soil (silty-sand) from each prototype were divided in three equal segments (entrance, middle and exit) and analyzed for their arsenic content. Results revealed that the planted wetlands have a higher As-mass retention capacity (87-90% of the total As inflow) than prototypes without plants (27%).
  
  
  RESULTS
  As mass balance in the planted wetlands revealed that 78% of the total inflowing As was retained in the soil bed. Nearly 2% was absorbed in the plant roots, 11% was flushed as outflow, and the fate of the remaining 9% is unknown. In the prototype without plants, the soil retained 16% of As mass, 72% of the arsenic was accounted for in the outflow, and 12% was considered unknown. Although E. macrostachya retained only 2% of the total arsenic mass in their roots, its presence was a determining factor for arsenic retention in the wetland soil medium.
  
  
  CONCLUSIONS
  Hence, planted wetlands might be a suitable option for treating As-contaminated water.
authors.affiliation: Renewable Energy and Environmental Protection Department, Advanced Materials Research Center (CIMAV), Ave. Miguel de Cervantes #120, C.P. 31109, Chihuahua, Chihuahua, Mexico.
authors.forename: Mario Alberto
authors.initials: MA
authors.lastname: Olmos-Márquez
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Alarcón-Herrera
authors.forename: Ignacio Ramiro
authors.initials: IR
authors.lastname: Martín-Domínguez
mesh_terms: D001151:Arsenic / Q000032:analysis / Q000378:metabolism*; D018053:Arsenites / Q000032:analysis / Q000378:metabolism; D001673:Biodegradation, Environmental; D001692:Biological Transport; D031256:Eleocharis / Q000254:growth & development* / Q000378:metabolism*; D004785:Environmental Pollutants / Q000032:analysis / Q000378:metabolism*; D005618:Fresh Water / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008800:Mexico; D010084:Oxidation-Reduction; D018517:Plant Roots / Q000737:chemistry / Q000378:metabolism; D017670:Sodium Compounds / Q000032:analysis / Q000378:metabolism; D012987:Soil / Q000737:chemistry; D013997:Time Factors; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
chemical_list: D018053:Arsenites; D004785:Environmental Pollutants; D017670:Sodium Compounds; D012987:Soil; C017947:sodium arsenite; D001151:Arsenic