Combined effects of low-molecular-weight organic acids onmobilization of arsenic and lead from multi-contaminated soils

A batch experiment was conducted to examine the combined effects of three common low-molecularweightorganic acids (LMWOAs) on the mobilization of arsenic and lead in different types of multicontaminatedsoils. The capacity of individual LMWOAs (at a same molar concentration) to mobilizesoil-borne As and Pb varied significantly. The combination of the organic acids did not make a marked“additive” effect on the mobilization of the investigated three elements. An “antagonistic” effect onelement mobilizationwas clear in the treatments involving oxalic acid for some soils. The acid strength ofa LMWOA did not play an important role in controlling the mobilization of elements. While the mobilizationof As and Pb was closely associated with the dissolution of soil-borne Fe, soil properties such asoriginal soil pH, organic matter contents and the total amount of the element relative to the total Femarkedly complicated the mobility of that element. Aging led to continual consumption of protonintroduced from addition of LMWOAs and consequently caused dramatic changes in solution-borne Fe,which in turn resulted in change in As and Pb in the soil solution though different elements behaveddifferently