The pseudometallophyte Schoenoplectus californicus: a potential heavy metal freshwater bioremediator.

GERPE, MS; CHIODI BOUDET, LN; ESCALANTE, A; VON HAEFTEN, G; MORENO, VJ

Maryland, Baltimore, USA

Simposio; The Ninth International In situ and On-site bioremediation; 2006

Batelle

Se presenta en este periodo ya que fue aceptado en noviembre 2006, por eso y debido a que no el sistema no acepta años mas alla de 2005 y 2006, se cita como año de reunion 2006, pero quiero aclarar que sera 2007. Some higher plants have developed tolerance strategies to heavy metal which enable them to survive and reproduce in contaminated soils. In general macrophytes, and particularly bulrush, have high capacity to assimilate heavy metals from sediments. This matrix constitutes the principal reservoir and source of this contaminant to biota in the aquatic environment. In the present study, we analysed the capacity to accumulate zinc, copper and cadmium of bulrush (Schoenoplectus californicus) in a freshwater body of Argentina, and its utilisation as a possible metal bioremediator for impacted aquatic environments. Metal concentrations distribution was studied at Nahuel Rucá lagoon (37º 37?S - 57º 25?W, Argentina). It belongs to the Mar Chiquita coastal lagoon basin, which is connected to the sea. It?s a shallow water body without stratification and sediments are mainly formed by clay and silt. The surrounding fields are destined to agricultural and stockbreeding practices. Roots and shoots samples were taken from bulrush, complemented with sediment samples from superficial (SS) and near root (NRS) areas. Metal determinations were performed by Atomic Absorption Spectrophotometry with air/acetylene flame (FAAS), with proper acid mineralization. From sediment, both total and labile fractions were determined. Control quality of data was checked by analyses of Certificated Reference Material (CRM) under same mineralization and determination conditions. For all studied metals labile concentrations were lower than total ones, and positive correlations (r= 0,9177 - 0,9981, p < 0,05) between both studied sediments were found. Schoenoplectus californicus presented lower levels than total fraction, while higher to labile one. Highest levels of metals were found in sediments (SS and NRS) with highest percentages of total organic matter (TOC) and very fine grain size. Moreover, metal levels in roots showed positive correlations with those found in labile fraction of NRS. These situations point out the role of both mentioned parameters in binding or mobilizing of metals and consequently their bioavailability to bulrush. The low concentrations found in sediments and the presence of metals in S. californicus indicates their high capacity to accumulate them. Shoots presented lower levels of Zn and Cu than roots, while for Cd both tissues showed concentrations in equal magnitude order. This suggests that S. californicus is using an exclusion strategy for Zn and Cu, essential metals, and an accumulation strategy for Cd, non essential ones. The capacity to accumulate Zn, Cu and Cd by S. californicus as of very low labile levels in sediments let consider this species as a pseudometallophyte. For that reason, it?s possible to use to bioremediate freshwater environments impacted by heavy metals.