SUITABILITY OF DIFFERENT EXTRACTION AGENT S FOR THE DETERMINATION OF PLANT-AVAILABLE PART OF SOIL ARSENIC

Several soil-extraction agents were tested for the deter mination of p lant-available As showing the following decreasing order of As extract ability from soil: 2 mol.l(-1) HNO3 > 0.43 mol.l(-1) CH3COOH > 0.5 mol .l(-1) NaHCO3 > 0.01 mol.l(-1) CaCl2 greater than or equal to 0.005 mo l.l(-1) DTPA > 0.1 mol.l(-1) NaNO3 > I mol.l(-1) NH4NO3. The relations hip between As released by the individual extraction agents and As con centrations in radishes was obtained by linear-regression analysis. Th e As concentrations in leaves seem to more closely correlate with the soil-extractable As than the concentrations in roots. The 0.01 mol.l(- 1) CaCl2 proved the suitable extraction agent for the evaluation of av ailability of the soil As by plants.