Cadmium concentrations in CaCl2 extracting solutions at various concentrations were determined by graphite furnace atomic absorption using two background correctors: the deuterium and the high-speed self-reversal background correction systems. Under- and overestimation of the Cd absorbance signals in CaCl2 solutions were observed for concentrations greater than 0.005？M using the deuterium lamp while no important effect was observed using the other background correction system. The analytical performance of the spectrometer for the determination of Cd was studied in 0.01？M CaCl2 solution and single extractions were performed using reference materials and contaminated soil samples. Cadmium was determined using the two background correction systems and a third method, which consists of the use of the deuterium lamp without any chemical modifier, was added to the study. The results showed that the third method was unable to determine Cd concentrations in the CaCl2 solution due to the presence of extractable arsenic and iron. For solutions without any dilution or diluted with a very low dilution factor, the CaCl2-extractable Cd concentrations measured using the deuterium lamp were systematically below those found using the high-speed self-reversal method. These differences were explained by the presence of chloride ions in the atomization step. 1. Introduction Cadmium uptake by organisms is poorly related to the total Cd concentrations in contaminated soils [1]. Many studies pointed out that the chemical behavior and the potential toxicity of metals (often related to their environmental availability to organisms) depended on the binding of metals with ligands [2–6]. Depending on the physicochemical parameters of the soils, the soluble metals usually react with organic (humic and fulvic acids) as well as inorganic (sulfate, sulfide, phosphate, carbonate, oxide and hydroxide, and chloride) ligands. The most-studied ligand is probably the chloride ion because salinity increases Cd-uptake by plants by forming environmentally available Cd-chloro complexes as and CdCl2 [5, 7–13]. The prediction of metal bioavailability is of crucial importance for the assessment of environmental quality of contaminated soils. Thus, to understand the processes involved in metal uptake by plants (phytoavailability), the use of extracting solutions rather than the total metal contents is so recommended [13–16]. Among salt solutions used in single extractions, calcium chloride (CaCl2) appears as the most widely used extractant to assess plant-available Cd concentrations in soils
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