Concentrations of heavy metals (Cu, Cd, Cr, Zn, Mn, Fe and Pb) in the water columns,
aquatic plants and sediments of fourteen lakes of varied levels of pollution were
measured.
Correlation analysis was carried out between heavy metal concentrations in aquatic
plants and heavy metal concentrations in water and sediment. The aquatic plants
which accumulated heavy metals in their tissues in proportion to that in water and
sediments were identified.
The aquatic plants studied were: 8/yxa auberti Rich, Cabomba caroliniana Gray,
Ceratophyllum demersum L, Ceratopteris thalictroides (L.) Bron, Chara globularis,
Eichhornia crassipes Solmn, Hydrilla verticillata Royle, Ipomoea aquatica Forsk,
Limnophila aromatica (Lam.) Merr., Ludwigia adscendens (L) Hara, Nelumbo nucifera
Gaertn, Nymphaea stallata Linn, Nymphoides indica (L.) Kuntze, Typha angustata
Bony & Chaub and Utricularia aurea Lour.
Metal uptake by aquatic plants varied between different species and within the same
species depending on lake water contamination levels. The level of metal uptake to a
great extent was a function of the environment water metal concentration.
Results showed that Utricularia accumulated Mn, Zn, Cr, Cd and Pb in direct proportion
to the overlying waters (r2 = 0.69, 0.63, 0.69, 0.65 and 0.39 respectively). Hydrilla
accumulated Cu, Mn, Zn, Fe, Cr, Cd and Pb in direct proportion to the overlying waters
(r2 = 0.65, 0.66, 0.44, 0.72, 0.38, 0.63, and 0.73 respectively). Blyxa leaves
accumulated Zn, Fe, Cr, Cd and Pb in direct proportion to the overlying waters (r2 =
0.74, 0.74, 0.72, 0.60 and 0.82 respectively). Echhornia leaf accumulated only Cr in
direct proportion to the overlying waters r2 = 0.81. Nymphaea leaf and Chara did not
accumulate any metal in direct proportion to the overlying waters.
Roots of Blyxa auberti, Ceratopteris thalictroides, and Eichhornia crassipes contained
higher concentrations of heavy metals than their leaves. Roots of Blyxa accumulated
Cr, Cd and Pb in direct proportion to the overlying waters (r2 = 0.91, 0.65 and 0.69
respectively). Echhornia root accumulated Cd in direct proportion to the overlying
waters with r2 = 0.90. Nymphaea stem showed no significant correlations between the
metal concentrations in the waters and in the plant.
Utricularia accumulated Zn, Fe, Cr, Cd and Pb in direct proportion to the metals in the
underlying sediment extracted by cold hydrochloric acid (r2 = 0.84, 0.51, 0.47, 0.68 and
0.80 respectively). Hydrilla accumulated Cu, Zn, Cr, Cd and Pb in direct proportion to
the underlying sediment (r2 = 0.34, 0.37, 0.91, 0.49 and 0.96 respectively). Blyxa
accumulated Zn, Fe, Cr, Cd and Pb in direct proportion to the underlying sediments (r2
= 0.99, 0.61, 0.82, 0.75 and 0.64 respectively) . Echhornia leaf showed significant
correlation between the Cu (r2 = 0.83) and Cr (i2 = 0.88) concentration in underlying
sediment and the plant. Nymphaea leaf showed a significant correlation between the
Zn (r2 = 0.83) concentration in the plant and the underlying sediments.
Roots of Blyxa showed significant correlation between concentrations of Cu, Cr and Pb
in sediment extracted by hydrochloric acid and plant (r2 = 0.9, 0.7 and 0.9
respectively). Roots of Echhornia had no significant correlation with the sediment
metal concentrations (hydrochloric acid extractable).
Two techniques (cold hydrochloric acid extractable and nitric acid extractable) to
extract metals from sediment were compared. Based on correlations of metal
concentrations in plant tissue and metal extracted from the sediment, it was concluded
that the cold hydrochloric acid extractable metal technique is more suitable for
determining bioavailable sediment metal concentration in environmental studies.
Laboratory studies investigations on the bioaccumulation of Zn and Cu in Hydrilla
confirmed that Hydrilla is a good bioindicator of Cu as it accumulated 20360 ug/g dry
weight of Cu in 72 hours. Hydrilla showed higher bioaccumulation factor with low
concentration of Cu in the solution, in the laboratory studies.
Hydrilla was determined to be the best indicator species as it reflected the heavy metal
concentration in the environment which was supported by the laboratory studies.
| Identifer | oai:union.ndltd.org:ADTP/219306 |
| Date | January 1997 |
| Creators | Sabet, Mitra Deliri, n/a |
| Publisher | University of Canberra. Resource, Environmental & Heritage Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | ), Copyright Mitra Deliri Sabet |
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