S. Sharmasarkar et Gf. Vance, EXTRACTION AND DISTRIBUTION OF SOIL ORGANIC AND INORGANIC SELENIUM INCOAL-MINE ENVIRONMENTS OF WYOMING, USA, Environmental geology, 29(1-2), 1997, pp. 17-22
Citations number
16
Categorie Soggetti
Water Resources","Environmental Sciences","Geosciences, Interdisciplinary
Selenium (Se), an animal toxicant and aquifer contaminant, occurs in c
oal mine environments of Wyoming. There is a paucity of information on
solution-phase Se speciation in mine soils. The objectives of this st
udy were to compare Se extraction efficiencies of various reagents and
to characterize SeO32- (selenite), SeO42- (selenate) and 4 organic Se
components in these extracts. Forty coal mine soils were extracted us
ing DI (deionized) water, hot water (0.1% CaCl2), AB-DTPA, NaOH, and K
H2PO4. Each solution was analyzed for total dissolved Se, and inorgani
c and organic Se fractions. Both inorganic and organic Se fractions we
re detected in the soil extracts. The order of Se (total, inorganic, a
nd organic) extraction efficiency for different reagents was DI water
< hot water < AB-DTPA much less than NaOH much less than KH2PO4. The i
norganic-organic Se ratios in DI water, hot water, AB-DTPA, NaOH, and
KH2PO4 extracts were 60:40, 26:74, 61:39, 87:13, and 52:48, respective
ly, indicating predominance of inorganic Se in all but the hot water e
xtract. Selenite was the dominant inorganic species in AB-DTPA and KH2
PO4 extracts, while SeO42- was the major Se species in the DI water, h
ot water, and NaOH extracts. Significant correlations (P < 0.01) were
observed among extractable inorganic Se [NaOH and KH2PO4 (r=0.95); hot
water and AB-DTPA (r=0.89)], total soluble Se [DI water with hot wate
r (r=0.98) and AB-DTPA (r=0.95)], and Se species [SeO32- in AB-DTPA wi
th SeO42- in NaOH (r=0.94) and SeO32- in KH2PO4 (r=0.88)]. These corre
lations are indicative of Se extraction efficiency, thermodynamically
predicted chemical transformations (such as oxidation of SeO32- to SeO
42-), and probable interconversions between the organic and inorganic
Se fractions (r=0.70 in KH2PO4 extracts); as a whole the correlations
can be used as statistical validations of possible geochemical process
es.