Methods of Groundwater Vulnerability and Protectability Assessment - Groundwater Vulnerability: Chernobyl Nuclear Disaster - page 16

Zektser [2001] used the same approach to determine the contaminant
travel time in the unsaturated zone. The author also introduced the concepts of
the full residence time of a contaminant and the time of water exchange in the
groundwater system considered based on the balance of the groundwater
recharge and discharge. Considering a more general approach to the ground-
water protectability assessment, Zektser also gave a more generalized determi-
nation of groundwater protectability as the property of a natural system which
allows the groundwater composition and quality to be preserved as satisfying
the requirements of the groundwater practical use during a forecast period.
This means that requirements for groundwater protectability are different
depending on its use, e.g., for potable, technical, or industrial purposes.
For a groundwater protectability assessment in any groundwater sys-
tem (saturated or unsaturated), Zektser [2001] and Rogachevskaya [2002]
determined the full residence times T w and T c for nonsorbed and sorbed con-
taminants, respectively, by the formulas

TVQ

w = /,

(1.10)

TVRQ

c = /,

(1.11)

where V is the volume of the system, Q is the rate of groundwater flow passing
through the system, and R is the retardation factor determined by equation (1.9).
The geochemical aspects of groundwater were studied Kraynov and Shvets
[1987], Kraynov et al . [2004], Pityeva [1999], and Pityeva et al . [2006] based on the
concept of geochemical barriers of geological medium. This concept was first
proposed by Perelman [1961], who determined the geochemical barrier as a zone
in which a sharp change of hydrogeochemical conditions of chemical element
migration takes place at short distances, causing their precipitation to a solid phase.
Pityeva [1999] proposed the concept of “geochemical groundwater protect-
ability” determined by a series of physicochemical processes causing the removal
of contaminants from the groundwater, such as sorption in porous or fractured
media. According to Pityeva, geochemical groundwater protectability includes:
- identification and quantitative assessment of physicochemical processes
along the travel paths of contaminants to groundwater;
- their;
- assessment of the potential manifestation of these processes in different
conditions and objects determining the groundwater protectability.
Assessment of groundwater protectability is conducted the depending on
types and properties of water-bearing rocks, as well as the thickness of the unsat-
urated zone.
Further development of the hydrogeochemical aspects of groundwater vulner-
ability assessment is found in the work by Goman [2007] as related to the migration
of organic contaminants through low-permeable hydrogeological beds in areas of
common solid waste repositories.