S. Sharmasarkar et Gf. Vance, KINETICS OF SELENOMETHIONINE DISAPPEARANCE FROM RECLAIMED COAL-MINE SOILS OF WYOMING, USA, Environmental geology, 29(3-4), 1997, pp. 202-208
Citations number
31
Categorie Soggetti
Water Resources","Environmental Sciences","Geosciences, Interdisciplinary
Selenomethionine (SeM) is an organic toxicant that is present in selen
iferous environments. No kinetic data is yet available regarding SeM r
eactions in coal mine environments, where selenium (Se) toxicity is a
potential concern. A kinetic study was conducted on two reclaimed coal
mine soils (Typic Torriorthents) from Wyoming having sandy and clayey
textures. Four levels of SeM treatments (0, 50, 100 mu M, and plant a
mendment from the mine vegetation) were reacted with the soils for 4,
7, 14, 28, 42, 56, and 84 days to characterize the kinetic behavior of
overall SeM disappearance from soil solutions. Detection of SeM in so
il solutions at the control level (0 mu M SeM) indicated occurrence of
indigenous SeM in the soils. In the plant-amended soil solutions, muc
h greater concentrations of SeM were observed as compared with the soi
l-only systems. This indicated the plant material was a more potential
source of SeM than the mine soils. A time-dependent loss in solution
SeM concentrations was observed for both soils under 0, 50, 100 mu M S
eM treatments. For the soil-plant mixtures, the solution SeM concentra
tion increased initially, reached a maximum after 14 days, and then de
creased thereafter. In the plant-amended soil solutions, SeM concentra
tions at all time intervals were higher for the sandy as compared to t
he clayey soil. At 50 and 100 mu M Sem treatments, the solution pH was
linearly related to the percentages of SeM disappeared from the solut
ions; greater percentage of SeM was removed from solutions at comparat
ively lower pH levels, which was greater than or equal to 90% at pH 7.
7 for both soils. Solution SeM concentrations decreased exponentially
with time following first-order kinetic reactions. Under all applicati
ons (except for the control), C-0 (SeM concentration at t=0) values fo
r the sandy soil were greater than those determined for the clayey soi
l, indicating higher solution SeM availability for the former and more
SeM retention by the latter at t=0. Comparison of C-0 in controls (0
mu M SeM addition) suggested greater indigenous SeM in the clayey soil
. For both soils, C-0 values under different treatments followed the o
rder, (soil+100 mu M) > (soil+50 mu M) > (soil+0 mu M). The specific r
eaction rate constants (K-r) of SeM for both soils were similar (0.031
and 0.029 day(-1) for sandy and clayey soils, respectively); low K-r
values indicated that SeM loss from our reclaimed coal mine soil solut
ions would follow rather slow kinetics. The half-life (t(0.5)) of SeM
varied from 15 to 55 days depending on treatment level. The knowledge
obtained from this study should contribute in developing time-based Se
reclamation strategies in coal mine environments.