Electrothermal atomic absorption spectrometric determination of Cr(VI) in soil after leaching of Cr(VI) species with carbon dioxide

The possibility of extraction of Cr(VI) from soil with CO 2 has been studied using electrothermal atomic absorption spectrometry. The presence of CO 2 at higher levels in the soil than those arising from atmospheric air may result in the natural leaching or weathering of Cr(VI) compounds from soil to ground waters. According to calculations, the amount of leached Cr(VI) is proportional to the partial pressure of CO 2 in the soil. Experimental results show that after the treatment of soil samples as a slurry with CO 2, the concentration of extracted Cr(VI) compounds increases 2.5-fold in comparison with that of a simple water fraction. This represents the amount of Cr(VI) which can be “naturally” leached from soil. The “total” Cr(VI) present in a given sample of soil can be released using a 0.1 M solution of Na 2CO 3. A good correlation ( R 2=0.9985, n=6) between the amount of Cr(VI) leached from soil and the concentration of dissolved CO 2 was obtained. Results for the determination of Cr(VI) have been confirmed by the analysis of CRM 545 with good agreement between certified (39.5±1.3 μg mg −1) and found (38.8±1.2 μg mg −1) values. A limit of detection (3 s) of 0.07 μg g −1 was estimated for Cr(VI) in soil samples.