Low-molecular-weight organic acids (LMWOAs) and humic acids have great effects on the availability of cadmium in the soils. LMWOAs, which was excreted by the plant roots, can increase the extractability, transportation and bio-availability of soil cadmium while the organic acids with higher molecular weight such as EDTA prohibits its adsorption by plant. Humic acids promote the solubility of soil cadmium. Depending on the different fractions of humic acids and environmental factors, humic acids can increase...