Effect of humic acids on species and activity of cadmium and lead in red soil
腐殖酸对红壤中铅镉赋存形态及活性的影响

Effect of various fractions of humic acids on form speciation and activity of Cd and Pb in red soil was discussed intensively in this paper. Results showed that the addition of humic acids promoted residual Cd and Pb transfer to organic form. The higher amount and the lower temperature, the more remarkable this transformation efficacy. The acute change of the most bioavailable Cd and Pb dominantly occurred within 1 hour after the addition of humic acids and the contents tended to become stable as time went by. Fulvic acid (FA) enhanced available metals, while humic acid (HA) exhibited certain inhibition and inactivation. The effect strength of the two fractions of HA was in the sequence of GHA>BHA. Thus, to add red soil with the organic materials with the high proportion of HA especially GHA could decrease the harm of Cd and Pb to crops.