[Effect of dissolved organic matter from landfill-leachates on dissolution of Pb in soils]

Dissolution of lead in two contaminated soils facilitated by dissolved organic matter(DOM) from the different ages of landfill leachate (0 a, 4 - 5 a, 12 a) were studied with a batch desorption trial. The results show that landfill leachate DOM obviously facilitated dissolution of Pb in the contaminated soils. Moreover, the shorter landfill ages, the higher dissolution rate. It was found that the content of the higher molecular weight fraction of landfill leachate DOM was increased with the increase of landfill ages. Generally, lower molecular weight fraction (M(r) < 1 000) would lead to soil Pb mobilization easier than the higher molecular weight fraction (M(r) > 25 000) . For example, the average net dissolution rates of Pb in a contaminated acidic red soil were enhanced by 123.8% in the presence of lower molecular weight fraction of DOM, with comparison to than that in the presence of a higher molecular weight fraction. Similar results were also observed in the contaminated calcareous soil. The average dissolution rates of Pb in the contaminated soils amended with landfill leachate was increased with pH increase in comparison with in the absence of landfill-leachate.