Cadmium in ∼10% of root and leafy vegetables sold through the Sydney Market exceeds the maximum permitted concentration (MPC) set by the Australia New Zealand (ANZ) Food Authority (0.05 mg kg −1 fresh weight). The leafy vegetables are mostly produced in the Greater Sydney Region; therefore, we investigated Cd contamination in the soils and vegetables of the Region. The crops and topsoils (0–15 cm) from 29 farms and uncropped (background) top soils were sampled and analyzed. Fruit generally had the lowest Cd levels and leafy vegetables the highest, with 0 and 27% exceeding the MPC. Cadmium in cropped soils was 0.11 to 6.37 mg kg −1 (mean 1.33 mg kg −1 ) and in background soils averaged 0.36 mg ka −1 . Soils derived from shale had the highest background Cd levels. Additions of P, Zn, and Cd in fertilizer and poultry manure explained significant proportions of the increases in soil concentrations of P ( r 2 = 0.62, P < 0.001) and Zn ( r 2 = 0.29, P > 0.05), but not of Cd. Cadmium increases were more closely related to increases in Zn ( r 2 = 0.26) and exchangeable cations ( r 2 = 0.34), which result from a history of heavy, annual applications of poultry manure. Typical rates of Cd addition were about 10 times the sustainable rate. Finally, the ANZ environmental investigation guideline for soil Cd (3 mg ka −1 ), was a poor indicator of crop contamination, because ∼0.3 mg Cd kg −1 soil resulted in lettuce ( Lactuca sativa L.) and broccoli ( Brassica oleracea ) exceeding the MPC.
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Jinadasa et al. (1997) studied this question.