Competitive Sorption and Transport - Transport and Fate of Chemicals in Soils: Principles and Applications - page 244

and complexation with humic acids (Al and Fe may form bridges between
organic ligands and P ions). Irreversible sorption is considered to involve
chemisorption and fixation within mineral structures. Scientists generally
agree that many types of P retention processes can take place simultane-
ously. Less is known as to whether these reactions operate in series or in
parallel. Experimental techniques are available in the literature to monitor
sorption and fixation reactions. Although a mathematical model to com-
pletely describe P reactions in soil doesn't exist, models that approximate
these reactions do. Multireaction sorption models constitute a class of such
approximations and offer a practical means of approximating P mobility dur-
ing water flow in soils. In general, the sorption behavior of vanadate in soils
is similar to inorganic phosphate. However, V also reduces acid phospha-
tase activity in soil, which alters the rate of mineralization of organic matter
and may reduce phosphate bioavailability (Tyler, 1976). The interactions of V
with other ions present in the soil solution (e.g., phosphate) and its potential
mobility in the soil profile have not been fully investigated (Mikkonen and
Tummavuori, 1994). For all three columns with an input pulse containing
both P and V BTCs for P arrived earlier and with higher peak concentrations
than those for V. In addition, a decrease in effluent concentration due to flow
interruption was observed in all BTCs associated with the third pulse in all
three columns, which indicates increases in the amounts of P or V sorbed
(Figures 7.37 to 7.39). These observations are consistent for both P and V and
show the kinetic nature of the retention mechanisms. For Sharkey clay soil,
miscible displacement results illustrated the extent of P as well as V retention
in this montmorillonitic soil (results are not shown). For all input V concen-
trations, the presence of P resulted in a decrease in the amount of V sorbed
at all reaction times. This finding was consistent with that obtained for the
kaolinitic Cecil soil as well as a montmorillonitic Sharkey soil.
7.8.5 Copper-Magnesium
Copper is a heavy metal exploited in large quantities for economic value
which often leaves many abandoned Cu mines around the world. Drainage
water from the abandoned mines often contains high Cu concentrations and
can be of environmental concern (Amacher et al., 1995). An understanding of
the retention and transport of Cu in mine soils is necessary for minimizing
possible adverse effects from Cu mining.
We present retention and transport studies for two soils: Cecil soil and
McLaren soil (with pH of 4.1, organic matter content of 3.03%, and CEC of
3.3 meq/100 g). The Cecil soil was chosen as a benchmark soil and was pre-
viously characterized for its affinity for retention of several heavy metals
(Buchter et al., 1989). McLaren soil was obtained from a site near an aban-
doned Cu mine on Fisher Mountain, Montana. Acid mine drainage from the
abandoned mine flows into Daisy Creek below the mine, which is located
about two miles from Cooke City, Montana (Amacher et al. 1995). Results