THE TRANSFER OF CADMIUM FROM SEWAGE-SLUDGE AMENDED SOILS INTO THE EDIBLE COMPONENTS OF FOOD CROPS

The application of sewage sludge to soils used for the production of food crops represents a potential means by which human dietary exposures to Cd may be elevated. Three crops (lettuce, cabbage and potato) were grown on a range of sewage sludge-amended soils in large tubs in the field. Liming, to increase the pH, reduced the mean concentration of Cd in lettuce and cabbage but not in potato tubers. Four soil tests were evaluated as a means of predicting crop Cd concentrations; DTPA proved to be the most accurate. Multivariate equations were derived to predict crop Cd concentrations and CF-values (Plant concentration DW/Soil concentration DW); these equations tended to underestimate observed values from an independent greenhouse experiment.