Lq. Ma et al., EFFECTS OF INCUBATION AND PHOSPHATE ROCK ON LEAD EXTRACTABILITY AND SPECIATION IN CONTAMINATED SOILS, Journal of environmental quality, 26(3), 1997, pp. 801-807
Lead distribution in 11 contaminated soils among five physical size fr
actions was studied. Lead was present in elevated concentrations in th
ese soils, ranging from 198 to 12 523 mg kg(-1). Although Pb in these
soils was randomly distributed among the five size fractions studied,
it was slightly concentrated in the silt and clay (< 53 mu m) fraction
with some exceptions, Several single chemical extractants were used t
o evaluate Pb availability in the contaminated soils. The effects of i
ncubation and phosphate rock on Pb availability were also investigated
. Significant amounts of Pb were extracted with all the extractants, T
he extractability increased in the order: H2O < Ca(NO3)(2) < HOAc < ED
TA-NH4OAc. The percentage of Pb extracted generally decreased with inc
reasing incubation time as the soils gradually lost moisture during in
cubation, Net extractable Pb reduction with incubation time was not co
rrelated with soil pH, organic matter, or total Fe and Mn contents in
soils. Reduced Pb extractability with incubation may be attributed to
precipitation/adsorption of Pb, rendering Pb less available. Addition
of phosphate rock reduced Ca(NO3)(2) and HOAc extractable Pb from Pb-c
ontaminated soils, but had little effect on EDTA-NH4OAc extractable Pb
. Net extractable Pb reduction by phosphate rock was not correlated wi
th soil pH, organic matter, or other metals such as Zn, Cu, Ni, and Cd
in soils, but it was highly correlated with total Pb (r = 0.7). Our r
esults indicate that physical-chemical speciation of Pb-contaminated s
oils can be a useful tool in evaluating Pb availability.