Heavy metals in surface sediments of Waiwhetu Stream, Lower Hutt, New Zealand

Abstract

Surface sediment samples (60 µm-2 mm, and < 60 µm 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 are 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. M92020

Macrophytes in Urban Stream Rehabilitation: Establishment, Ecological Effects, and Public Perception

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A Nearest-Neighbour Gaussian Process Spatial Factor Model for Censored, Multi-Depth Geochemical Data

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Cu, Pb and Zn Fractionation in a Savannah Type Grassland Soil

“…Quantifying the geochemical phases of metals associated with soil is an important step in predicting the ultimate fate, bioavailability, and toxicity of metals Lu et al, 2005;Prusty et al, 1994). Easily soluble fractions that are bioavailable and most mobile in the environment are commonly investigated by single extraction procedures such as that of Deely et al (1992), while the partitioning of heavy metals between easily and sparingly soluble fractions in soils and sediments is investigated by sequential extraction procedures.…”