Toxicity and bioaccumulation of Cu in an accumulator crop (Lactuca sativa L.) in different Australian agricultural soils

Abstract

The toxicity and bioaccumulation of Cu in lettuce (Lactuca sativa L. var. Romaine cv. Long Green) grown in different Australian agricultural soils is assessed in this paper. We evaluate the effect of Cu and its interaction with soil properties on biomass production, through the establishment of the effective concentrations of Cu in soil that reduces biomass production by 50% (EC50) and 10% (EC10), and its accumulation in the different parts of the plant. Two biomass assays were conducted in three types of Australian agricultural soils contaminated with different Cu concentrations (no added Cu, 65.9, 659.0, 1977.0, 3295.0 and 6590.0 mgCu/kg). Results show that the levels of Cu tested significantly affected plant biomass production in all the soils assayed. No biomass was produced after the second dose (65.9 mg/kg) for Soil 1 (a Chromic Luvisol), after the third dose (659 mg/kg) for Soil 2 (an Eutric Planosol) and after the fourth dose (1977 mg/kg) for Soil 3 (a Pellic Vertisol). Toxicity was greater in soils with low pH and with smaller clay contents. The concentration of Cu in the lettuce leaves never exceeded 10 mgCu/kg fresh weight, which is the maximum Cu concentration allowed in the edible part of this crop by Australian legislation. According to the results obtained, lettuce could grow in Cu contaminated Australian agricultural soil having a Cu concentration between those that correspond to their EC50 and the EC10. The specific concentrations lay between 103.96 and 728.88 mgCu/kg, and between 49.03 and 443.10 mg/kg, respectively, although they are dependent on soil type. At these concentrations, potential yield production would be acceptable and the quality of crops, in terms of Cu concentration in the edible part of the plant, would not be compromised. The results achieved broaden the knowledge on the effect of high Cu concentrations in Australian agricultural soils, which can help when proposing adequate soil quality standards and management strategies in this type of soils.