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Modeling the Density‐Driven Movement of Liquid Wastes in Deep Sloping Aquifers
Author(s) -
Dorgarten HansWilhelm,
Tsang ChinFu
Publication year - 1991
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1991.tb00556.x
Subject(s) - aquifer , plume , geology , groundwater , hydraulic conductivity , stratification (seeds) , permeability (electromagnetism) , soil science , aquifer properties , flow (mathematics) , geotechnical engineering , mechanics , hydrology (agriculture) , groundwater recharge , meteorology , chemistry , seed dormancy , biochemistry , physics , germination , botany , dormancy , membrane , biology , soil water
One method for the disposal of hazardous liquid wastes is by injection into deep aquifers. Although these aquifers may be separated from underground sources of drinking water by thick formations of low permeability, their mobility due to different migration mechanisms has to be studied carefully, since the injected wastes remain toxic over periods of thousands of years. One possible mechanism for waste movement is density‐driven flow and transport, due to density differences between the waste and the surrounding water in the injection zone. In the present paper the importance of this phenomenon is studied mathematically by means of analytical and numerical calculations for typical deep injection conditions. The analytical estimates reveal that density‐driven movement of liquid wastes in sloping aquifers can be much stronger than plume migration due to natural hydraulic gradients. This finding is emphasized by the results of a two‐dimensional vertical finite element model, which is applied for detailed numerical simulations. Results show that during the initial stage, waste can be expected to spread into all directions due to density‐induced stratification effects. Later on, it mainly moves laterally along the slope of either aquifer top or aquifer bottom, depending on the waste density. If regional ground‐water flow is directed the same way, transport is accelerated. If regional ground‐water flow is in the opposite direction, on the other hand, transport to both sides must be expected to occur. Thus, the aquifer slope and regional hydraulic gradient may be equally significant factors in estimating potential migration of disposed liquid wastes.