Bioavailability of Cu, As, Cd and Pb in soil to radishes

Sammanfattning

Metal contamination among the world is widespread, where the major concern is the occurrence of potentially toxic metals in agricultural soil. Metals are accumulative and persistent in soil and can thus increase the toxicity of soils. Certain plants, such as radish, can accumulate metals in their tissues where mobile metals can be taken up by plants roots system. Metal speciation determines their mobility and bioavailability in the environment, where the bioavailability of metals is strongly related to the distribution over solid and liquid phases of the environment. This study investigates the bioavailability of Cu, As, Cd and Pb from two different soils to radishes, where the radishes represent vegetables consumed by humans. To investigate the bioavailability, sequential extraction was performed on the soil and digestion was performed on both the soil and radish parts. Analysis was done by ICP-MS to determine the bioavailable fraction of the elements of interest. Results show that highest levels were detected for copper (28.6 mg/kg – 52.0 mg/kg and 5690 mg/kg – 8710 mg/kg) and lead (10.8 mg/kg – 16.6 mg/kg and 1070 mg/kg – 1850 mg/kg) in both the agricultural and contaminated soil. Extraction steps 1, 2 and 4 gave the highest extractability overall, meaning that most elements were released due to ion-exchangeable prosses and from manganese oxide phases. In regard to the uptake by the plants, all values were below LOD, probably due to the lack of plant material. Since all values were below LOD, previous studies and theory were the basis for discussion and conclusions drawn. Soil-to-plant transfer factor (TF) values decreased from Cd > Cu > As > Pb for the agricultural soil and from Cd > As > Cu > Pb for the contaminated soil.