Heavy metals in southern and central Queensland canelands

Total concentrations of a range of nutrient and contaminant heavy metals in Queensland caneland soils (0-250 mm and 250-500 mm depths) from Rocky Point to the Burdekin region are reported and discussed. The heavy· metals (includes metalloids and non-metals) examined were arsenic, cadmium, cobalt, copper, chromium, lead, mercury, molybdenum, nickel, selenium, thallium and zinc. Mean concentrations at both depths were typical. of levels found in soils worldwide. While concentrations of several of the heavy metals differed significantly with depth, Cd and Hg were the only heavy metals with higher (P<0.00l) concentrations following 10 or more years of cropping, relative to 'paired' uncropped sites. Mean Cd concentrations at 0-250 mm increased four-fold from a background concentration of 0.01 ± 0.02 mglkg, whereas the increase at 250-500 mm was two-fold from a similar background concentration. The increase for Hg was almost three-fold at 0-250 mm (background concentration of 0.024 mglkg) and two-fold at 250-500 mm. The findings suggest that strategies to minimise inputs and to better understand the cycling of Cd and Hg in cane production systems are needed.