Sequential extraction analysis of heavy metals in sediments of variable composition using nitrilotriacetic acid to counteract resorption

Artificial sediments were made that contained variable amounts (up to 20% b y weight) of feldspar, calcite, Fe-oxide or organic matter. Analysis of sam ples spiked with Pb and Zn in the presence and absence of nitrilotriacetic acid (NTA) showed that 400 mg l(-1) of chelating agent greatly reduced or e liminated sorption in each case. Further study showed that this NTA concent ration did not cause significant mineral dissolution. Resorption during seq uential extraction analysis of artificial sediments is indicated by the fac t that with NTA, levels of metals are higher in the first step and lower du ring subsequent steps, compared with levels obtained without NTA. However, the addition of 400 mg l(-1) of NTA to each extracting solution in the sequ ence appears to be effective for counteracting resorption in feldspathic, c alcareous, ferruginous and carbonaceous sediments. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.