An agricultural soil in Southern England was amended with two annual applic
ations of sewage sludge at rates of 0, 10 and 15 t ha(-1) dry solids, Soil
concentrations of Zn reached 31.1 mu g g(-1) and the subsequent uptake was
measured in wheat plants (Triticum aestivum), grain aphids (Sitobion avenae
) and a predatory carabid beetle (Bembidion lampros) in order to test the h
ypothesis that Zn was transferred through this tri-trophic food chain. Conc
entrations of Zn in the wheat plants, aphids and predatory beetles reached
31.7, 116.0 and 242.2 mu g g(-1) dry wt., respectively. A potential exposur
e pathway from soil --> plant --> herbivore --> predator was identified, th
e concentration of Zn in the predatory beetle being related to the amount o
f aphids eaten and sewage sludge application rate. The concentrations of Zn
in the sludge-amended soils were all well within current UK regulation lim
its and the relevance of exposure pathways at sub-critical concentrations w
hen considering metal loading rates for sewage sludge amended soils is disc
ussed. (C) 1999 Elsevier Science B.V. All rights reserved.