New Zealand Journal of Agricultural Research abstracts
Concentrations of arsenic, cadmium, copper, lead, and zinc in New Zealand
pastoral topsoils and herbage
R. D. Longhurst
A. H. C. Roberts*
J. E. Waller
AgResearch Limited
Ruakura Research Centre
Private Bag 3123
Hamilton, New Zealand
*Present address: Ravensdown Fertiliser Co-Op Ltd, P.O. Box 608, Pukekohe.
Abstract A national survey of agricultural topsoils
and pastures was undertaken in the early 1990s to establish benchmark heavy
metal concentrations. In total, 398 sites were sampled covering the major
soil groups throughout the North and South Islands of New Zealand. Both pastoral
farmed (312) and non-farmed (86) sites were sampled. Composite soil samples
were taken from two depths, as well as pasture samples from the same area,
and analysed for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and
zinc (Zn) concentrations. There was significant (P < 0.05) enrichment
of Cd at the 0-7.5 cm depth in five of the eight soil groups on farmed sites
(0.44 mg kg-1), over background non-farmed soils (0.20 mg kg-1).
Total soil Cd was highly correlated (P < 0.001) to total soil phosphate
(P) suggesting Cd enrichment in pastoral soils was related to fertiliser
P applications. There was no enrichment of As, Cu, Pb, or Zn at the 0-7.5
cm depth on farmed soils compared with non-farmed soils. Results showed that
soil concentrations of these elements were either typical of worldwide averages,
or at the lower end of these ranges. There was, however, a significant (P
< 0.05) increase in Cu concentrations in the 0-2.5 cm depth on most farmed
soils (14.3 mg kg-1), compared with non-farmed soils (11.4 mg
kg-1). The main difference in heavy metal concentrations between
non-farm and pastoral pasture species was in the weed component. In general,
the Cu, Zn, Pb, and As concentrations were essentially pedogenic in origin.
Keywords arsenic; cadmium; copper; zinc; lead; pastoral
agriculture; soil groups; pasture species; grass; legume; weed; heavy metals;
total phosphorus
A03018; Received 19 March 2003; accepted 7 August 2003; online publication
date 26 February 2004
New Zealand Journal of Agricultural Research, 2004, Vol. 47: 23-32
0028-8233/04/4701-0023 © The Royal Society of New Zealand 2004
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