Resumo

VALLES-ARAGON, María Cecilia  e  ALARCON-HERRERA, María Teresa. Arsenic retention in a wetland constructed with Eleocharis macrostachya and Schoenoplectus americanus. Rev. Int. Contam. Ambient [online]. 2014, vol.30, n.2, pp.143-148. ISSN 0188-4999.

Arsenic can be removed from water via rhizofiltration using macrophytes that have arsenic accumulation phenotypes. The aim of this study was to investigate the performance of Eleocharis macrostachya and Schoenoplectus americanus in subsurface constructed wetland, as well as the system arsenic mass retention. Experiments were carried out in constructed wetland prototypes, two planted, one with E. macrostachya (HA) another with S. americanus (HB) and one without plants (HC). Samples of water were taken at the inlet and outlet of the wetlands during the 343 days 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 arsenic mass retention capacity (76 % HA 69 % HB of the total arsenic inflow) than prototypes without plants (32 % HC). Arsenic mass balance in the planted wetlands revealed that 73 % HA and 66 % HB of the total inflowing arsenic was retained in the soil bed. Nearly 1 % was absorbed in the plant roots, 24 % in HA and 31 % in HB was flushed as outflow, and the fate of the remaining 2 % is unknown. The prototype with E. macrostachya retained 7 % more arsenic than the one with S. americanus, although both performed much better than the prototype without plants. This confirms the importance of plants in the operation of constructed wetlands.

Palavras-chave : water; rhizofiltration; macrophytes; mass balance.