Civil Engineering Reference
In-Depth Information
upper groundwater can never be “well protected” or “protected enough” but
only “relatively” or “conditionally.”
Thus, although the groundwater protectability assessment by water perco-
lation time from the land surface to the groundwater table accounts for the
hydraulic conductivity of covering deposits, this method does not account for
the presence of geochemical barriers as well as the hydraulic and geochemical
capacity properties of the assessed aquifer itself.
After Goldberg, the development of groundwater protectability assessment
methods in the former USSR is associated with the works of
Mironenko and
Rumynin
[1990, 1999],
Pashkovskiy
[2002],
Pityeva
[1999], and
Zektser
[2001].
Their efforts were directed at accounting not only for hydraulic properties but
also for physicochemical properties of soil, in both unsaturated and saturated
zones.
In particular,
Mironenko and Rumynin
[1990] determined the percolation
time
t
w
of a conservative contaminant from the soil surface to the groundwater by
the balance equation
m
A
=
∫
0
() ,
wt
θ
z dz
(1.7)
w
where
θ(z)
is the volumetric water content that can in turn be related to
infiltration
w
, full moisture saturation
θ
m
(equal to effective porosity), field
capacity
θ
0
of soil (water content held in soil after excess water has drained) and
hydraulic conductivity
k
by the formula
w
k
.
(
)
θθθθ
=+ −
(1.8)
4
0
m
0
Rumynin
[2003] studied the sorption properties of groundwater geological
medium and their effect on radionuclide migration.
Pashkovskiy
[2002] proposed to assess the
contaminant travel time t
c
taking
into account sorption in soil and the unsaturated zone:
mR
w
RK
δ
ϑ
t
=
,
= +
1
,
(1.9)
c
d
where
m
(m) is the thickness of the unsaturated zone,
K
d
(dm
3
/kg) the distribu-
tion coefficient,
δ
(kg/dm
3
) the volume (specific) weight of rock,
θ
the volumetric
water content (usually substituted by effective porosity
n
),
w
(m/day) the infiltra-
tion velocity, and
R
the retardation factor determined as the ratio of water and
contaminant velocities.
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