Global NEST Journal

A risk-based decision analysis methodology is presented, that can be used as a water policy tool in the
design of economic incentive instruments, under conditions of uncertainty. A contaminated groundwater
resource system with unknown hydrogeological parameters is used as a case study. The polluter
has to select the policy to be followed among a series of alternatives, ranging from the extreme and
environmentally risky scenario of paying pollution charges as long as the aquifer will remain polluted,
up to the conservative option in terms of reduced environmental risks policy of safely rehabilitating the
groundwater system. The full-cost price of water, including direct, opportunity, and environmental
costs, both actual and probabilistic, as well as the risks of failure of the alternative scenarios due to the
uncertainty, as they result from stochastic simulation, are embedded in a risk-cost-benefit decision
model, developed for the evaluation of the alternatives. The pollution charges to be imposed by the
local water authority are determined through the appropriate development of this model and the use
of a proposed algorithm, in a way that these charges can act as incentives to the polluters, forcing them,
or the authorities, to select the most environmentally sustainable water policy, namely that of safely
restoring the aquifer.

Field experiments have been conducted to investigate flow and dispersion through obstacle arrays.
Model obstacles which represent real structures at a nominal scale between 1/10 and 1/20 were used.
The main purpose of the experiments was to examine flow and dispersion of contaminants in the vicinity
of individual obstacles embedded in an array of cubes. Two array configurations were used, namely
the in-line and staggered array configurations. The field experiments were supported by flow visualisation
trials performed in the wind tunnel. In the light of the results of these wind tunnel trials, the field
experiments were carried out using an array spacing S/H = 1.5 (where S is the space between two consecutive
array elements). Dispersion around an isolated model building has already been investigated
in the field (Mavroidis and Griffiths, 1996). Thus comparison is allowed between dispersion around an
isolated obstacle and around the same obstacle embedded in an array of cubes.

Abstract is currently not available.

The vertical migration velocity of radionuclides and the ability of soils components to immobilise them,
as the most important parameters of natural-restoration, was studied. The Dose Equivalent Rate
(DER) reduction of external ã-radiation was studied in order to assess its impact on human health. The
vertical migration velocities of 137Cs and 90Sr in typical soils of contaminated regions in Ukraine
(Chernobyl 30-km zone) and Belarus (Gomel region) have been evaluated annually during the last 8
or 10 years since the accident. In most of these soils the migration rate of 90Sr was found to be higher
than this of 137Cs and ranged from 0.71 to 1.54 cm year-1 and 0 to 1.16 cm year-1 respectively. At present
the main part of radionuclides is located in the upper 10 cm soil layer. The ability of the soil components
to immobilise the radionuclides was also investigated from 1989 to 1994 and was found that
approximately 57% of 137Cs was converted in fixed forms. It is expected that this percentage will
increase to 80% in the next years. Finally, we studied how the DER of ã-radiation, which changes with
the migration of radionuclides in the soil, affects the human health. In comparison with 1986, when
100% of 137Cs was distributed on the soil surface, a significant reduction of DER occurred in the studied
areas and about ten years after the Chernobyl accident, it ranges from 17.5% to 45%, depending
mainly on the level of initial contamination of soils and its migration velocity.