New Zealand Journal of Marine and Freshwater Research abstracts
Heavy metals in surface sediments of Waiwhetu Stream, Lower Hutt, New Zealand
JOANNE M.DEELY J.CLAIRTUNNICLIFF C.JANE ORANGE WAYNE H. L. EDGERLEY
Institute of Environmental Health
and Forensic Sciences Ltd P. O. Box 30 547 Lower Hutt, New Zealand
Abstract
Surface sediment samples (60 nm-2 mm, and < 60
\im fractions) from the Waiwhetu Stream, Lower Hutt City, New Zealand, were leached with dilute HC1 to remove the mobile heavy-metal fraction. Cd, Cr, Cu, Pb, Zn, Al, Fe, and Mn analyses of the leachates show that sediments of the upper reaches area of the stream are generally uncontaminated. In contrast, sediments in the lower reaches area are highly contaminated, despite clean-up measures in the late 1970s. Lead and Zn aire the most significantly enriched metals with concentrations over 1000 mg kg"
1 adjacent to some drains. In the polluted zone, metals originate from either upward remobilisation from underlying sediment (contaminated in the early 1960s and 70s) or more recent industrial spillages. Similar trends exhibited by Cd, Cu, Cr, Zn, Pb, and Al indicate that a proportion of the metal enrichment downstream probably results from a naturally higher clay content of sediments near the mouth of the stream. Fe and Mn show reverse trends to the other metals, indicating that a high proportion of these two metals occurs in substrate different to that of the other metals. The orange brick-coloured sediments of the upper reaches of the stream indicate oxides upstream; the black sediments in the lower reaches indicate sulphides downstream.
Keywords Waiwhetu Stream; heavy metals; remobilisation; sediment; pollution; oxides; sulphides; industrial activity; bioavailability
New Zealand Journal of Marine and Freshwater Research, 1992, Vol. 26:417-427 The Royal Society of New Zealand 1992
Received 22 April 1992; accepted 23 September 1992
PDF file of entire paper: medium quality (834K); (scanned from paper original: notes about this process)
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