| dc.description.abstract | Cadmium is a potentially toxic trace element present, at low
concentrations, in a variety of environmental media. The processing of
waste-waters produces sewage sludge, in which cadmium may be
present at high concentrations. Sewage sludge applied to soils used for
the production of food crops represents a means for the elevation of
human dietary exposure to cadmium. This study has examined aspects
of the bioavailability of cadmium from sludge-amended soils.
A number of sludge-amended and control soils were sampled and
placed in tubs in the field. Duplicates of each soil were limed to a mean
pH(H 20) of 6.9. Concentrations of cadmium in the edible tissues of
cabbages and lettuces were lower for those plants grown on limed soils.
Concentrations of cadmium in peeled potato tubers were not always
reduced by the application of lime. Cadmium bioavailability was
estimated by four soil test reagents, DTPA, EDTA-(Na) 2 , CaCl2 and
NH4NO3 . The DTPA test proved to be the best indicator of plant cadmium
concentrations. Multivariate statistics were used to develop models,
based upon soil variables, for the prediction of plant cadmium
concentrations and CF-values. Models were tested against an
independent data set.
Data quality for cadmium analyses was assessed by the routine use of
certified reference materials. Methods of ETA-AAS analysis were
developed and optimised for the control of interferences.
Preliminary cadmium speciation studies, using SEC-ICP-MS, are
described. Cadmium-binding species in the cytosol extract of potato
tubers do not appear to survive in vitro gastro-intestinal enzymolysis.
Cadmium- binding species in aqueous extracts of both intrinsically and
extrinsically labelled samples of cooked potato tuber have molecular
weights of < 2 x 10 3 daltons.
An iterative model was written to examine the influence of soil and plant
variables on the cadmium burden of the plough layer through time | en_US |
