[Aging process of Cr(III) in 22 typical soils of China and influence factors Analysis]

Aging process is a key factor influencing the availability and toxicity of heavy metals in soil. However, the aging of chromium (Cr) in soils and its influence factors are still unclear, as a result of complexity of soils in China. This study was conducted to investigate the aging process of Cr(Ill) in 22 typical soils of China by using 0.01 mol.L-1 CaCl2 as the extractant for available Cr. The results manifested that Cr spiked in the soil was time-dependently transferred from the available fraction into less labile fractions. Two regions could be distinguished: the first one for short extraction time (t <21 days), corresponding to a faster transformation of metals and the second for longer extraction time (t >21 days) where the transformation was relatively slower. The decrease of Cr in available fraction during the incubation could be simulated by the Elovich equation, and decrease rates were applied to reflect the transformation rates of aging process among various soils. Multiple regression analysis showed that decrease rates might be related to the organic matter, pH and amorphous Fe oxides of soil, and organic matter was the key factor to the aging process.