J. Thoming et W. Calmano, Applicability of single and sequential extractions for assessing the potential mobility of heavy metals in contaminated soils, ACT HYDR HY, 26(6), 1998, pp. 338-343
Heavy metal polluted sites are bearing an acute hazardous risk for the grou
ndwater, but also a potential one. While the acute risk can be assessed dir
ectly via seepage water measurements, determination of the potential risk i
s much more complex. It results from the sum of all reactions that are capa
ble to mobilize heavy metals under worst case environmental conditions. Usi
ng a fourfold sequential extraction (SE4) such a worst case was simulated f
or four soils highly contaminated with Pb, Zn, and Cu. The resulting potent
ial mobilizable amounts phi(pm) have been compared with those derived from
6 single extractions. By means of variance analyses, it is shown that phi(p
m) of lead can be represented by a single extraction with NH2OH. In contrar
y, phi(pm) of zinc can be represented using the pH(stat) test or an extract
ion with aqua regia, while phi(pm) of copper can be represented only by aqu
a regia extraction. The water-soluble amounts deriving from the DEV-S4 test
do not correlate with the potential mobilizable amounts of any metal. Ther
efore, an assessment of contaminated sites should include an aqua regia ext
raction additionally to the seepage water analysis.