Inhibition of ethylenediaminetetraacetic acid ferric sodium salt (EDTA-Fe) and calcium peroxide (CaO2) on arsenic uptake by vegetables in arsenic-rich agricultural soil

Abstract

Chemical immobilization of arsenic (As) in contaminated sites may be achieved through the use of inorganic and organic soil amendments to reduce its bioavailability. The chemical immobilization of As-rich soil by using ethylenediaminetetraacetic acid ferric sodium salt (EDTA-Fe) and calcium peroxide (CaO2) as stabilizing agents was investigated in Chianan plain of southwestern Taiwan. The As-rich soil was amended with EDTA-Fe, at the rates of 0, 0.35, 0.7 and 1.4Mgha−1, or with CaO2, at the rates of 0, 0.38, 0.76 and 1.52Mgha−1, and grown with radish (Raphanus sativus L.), lettuce (Lactuca sativa), Chinese cabbage (Brassica rapa) and Arden lettuce (Lactuca sativa L.). Results showed that those amended with EDTA-Fe at 0.35 and 0.7Mgha−1 can significantly reduce As accumulation in vegetables. Moreover, the uptake of As in vegetables decreased more in soil amended with CaO2 relative to that amended with EDTA-Fe. The topsoil amended with EDTA-Fe and CaO2 can significantly increase As chemisorption by oxides and hydroxides of Fe and Al on the soil surface. As indicated, applications of EDTA-Fe at the rate of 0.7Mgha−1 and CaO2 at the rate of 1.52Mgha−1 can obtain optimal effect on suppressing As uptake by vegetables. As a result, both EDTA-Fe and CaO2 proved to be effective in immobilizing As in the soil and thus can maintain nutrient balance of vegetables grown in As-rich soil, though CaO2 application obtained a better result.