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Transport of trace metals in the Magela Creek system, Northern Territory: II Trace metals in the Magela Creek billabongs at the end of the 1978 Dry season

Technical Memoranda 2
Davies SHR and Hart BT
Supervising Scientist, 1981
ISSN 0810-9532
ISBN 0 642 06087 8

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Transport of trace metals in the Magela Creek system, Northern Territory: II Trace metals in the Magela Creek billabongs at the end of the 1978 Dry season (PDF - 373 KB)

About this document

The concentrations of the trace metals Fe, Mn, Zn, Cd, Cu and Pb were determined in six Magela Creek billabongs near the end of the 1978 dry season (November, 1978). The billabongs selected for study represented backflow, channel and flood plain environments. There were significant limnological differences between, in particular, the backflow and flood plain billabongs, and the channel billabongs.

Compared with the total trace metal concentrations recorded during the wet season of 1978-79 (42 samples), there was an increase in the concentrations of total Fe, Zn, Cd and Cu in the backflow and flood plain billabongs. The increase was most noticeable for Fe, where the change was generally in excess of one order of magnitude; for Zn there was a two- to threefold increase, for Cd a four- to sevenfold increase and for Cu a three- to fivefold increase. An appreciable increase in the total Mn levels was only noted in Georgetown Billabong. There was no significant increase in the trace metal levels in the two channel billabongs.

The increase in total metal levels appears to be largely due to increases in suspended material. An additional increase in filterable metal levels possibly results from evaporative concentration occurring over the dry season. A model incorporating both these contributions was used with limited success to calculate the expected trace metal levels for Fe, Mn and Zn.

Variable amounts of the total trace metal concentrations were found to be in the filterable fraction. This ranged from <10% in the case of Fe, to over 90% of the Zn in some billabong waters. The proportion of this filterable fraction that is biologically available is not known.