Department of Geology
Eastern Washington University

Recent Masters theses in Geology

THE UPTAKE OF HEAVY METALS AND ASSOCIATED ELEMENTS BY SELECTED PLANTS ON
TAILINGS-CONTAMINATED SOILS:  AN EXAMPLE FROM THE COEUR D'ALENE RIVER
BASIN, IDAHO

Nikolaos Condoyannis

Abstract

During the summer of 1994, 38 samples of soils and 66 vegetation samples
were collected from the floodplain of the Coeur d'Alene River basin as part
of a U.S. Geological Survey project.  The samples were analyzed for 23
major and trace elements which include Ag, Al, As, Ba, Be, Ca, Cd, Cr, Cu,
Fe, Mg, Mn, Mo, Ni, Pb, Sb, Sr, Th, Ti, Tl, U, V, and Zn.  All the analyses
were performed by ICP-MS and ICP-AES.

The soil samples consist of 36 heavy metal contaminated and 2
uncontaminated soils.  Enrichment of Ag, As, Cd, Cu, Fe, Mn, Pb, Sb, and Zn
is present in floodplain soil and overlying plant samples, when compared to
an unimpacted control area.  These enrichments result from downstream
dispersal of mining and milling wastes from the Coeur d'Alene mining
district, a major Ag-Pb-Zn mining district.

The vegetation samples include 33 washed and 33 unwashed plants,
representing the following four plant species:  common reed (Phragmites
australis), marsh horsetail (Equisetum palustre), pondweed species
(Potamogeton spp.), and redtop grass (Agrostis stolonifera).  This study of
plant uptake of heavy metals from contaminated soils is based on the
analysis of washed plant samples ashed at 500° C.  Generally, the unwashed
vegetation samples have higher metal contents than the washed plants.

The relative uptake of heavy metals by plants from the floodplain soils was
also determined.  The accumulation of Cd, Sr, and Zn in Potamogeton (spp.)
is higher than in the underlying soil, while Mo is elevated in both
Potamogeton (spp.) and Equisetum palustre.  The uptake of remaining trace
elements is variable with concentrations ranging from 93% to less than 0.1%
of the underlying soil contents.  Plant-soil metal ratios in the examined
plant species are found to decrease in the following order:
Potamogeton(spp.) > Equisetum palustre > Phragmites australis > Agrostis
stolonifera.  This pattern indicates a progression from wet to relatively
dry growing conditions.  The solubility and consequent bioavailability of
metals in soils in the present study show a decrease as follows:  Ca > Mg >
Mn > Fe > Al > Ti for major elements and Cd „ Zn > Cu > As > Ag > Pb for
trace elements.  Submerged plants of Potamogeton (spp.) have the ability to
take up a relatively large amount of metals.