A hydrogeochemical study was carried out in the phreatic aquifer in two neighborhoods of Río Cuarto city, that do not have running water or sewer systems. The results show that 60 % of the water samples analyzed are unfit for human consumption due to the total and fecal coliform bacterial contents.
Furthermore, a large number of the samples show elevated amounts of salts, nitrates and chlorides. These results confirm for us that the source of contamination is the septic tank system (cesspools) that practically coexists at the same depths as the domestic water supplies.
Also being proposed is a different model of the behavior of the contaminants in each of the neighborhoods studied, as well as some measured steps of control and arrangement. At the present time more than 400 families are being given running water as a result of these investigations.
Blarasin, M., A. Cabrera, M. Villegas, C. Frigerio y S. Bettera. Contaminación del agua subterránea destinada a consumo humano en la cuenca del arroyo Del Bañado, Río Cuarto, Córdoba. Diagnóstico y pautas de control y ordenamiento. Actas de la I Reunión Nacional de Geología Ambiental y Ordenación del territorio. Río Cuarto, Córdoba, Argentina. Vol. I, pp. 23-41. Nov. 1995.
Contact:
M. Blarasin
Dpto. de Geología, Fac. Cs. Ex., Fco.-Qcas. y Nat.
UNRC
Enlace rutas 8 y 36, Km 601
(5800) Río Cuarto
Córdoba. Argentina.
The hydrologic cycle provides the structural concept for the subject of environmental hydrogeology. The study of the cycle allows the recognition of all water states, hydrodynamic laws, distinctive circulation environments, and so on. To avoid a dispersed acquisition of knowledge, a hydrologic investigation is developed in a determined geographic area during four months that includes field, laboratory and classroom work that favor the relationships between the hydrologic cycle and the geologic and anthropic factors. The work is carried out in the University surrounding area because it is the student´s social environment.
The following problem situation must be evaluated: our city needs water for industrial uses. The following items must be developed: a) a conceptual model of the hydrogeologic framework of the area b) the strategies to define whether surface water or groundwater will be used and the design of water abstractions. This proposal is based on system theory, with a holistic view of the hydrological subsystem, on inter- and trans-disciplinary works, on ecologic ethic and an environmental concept of the water resources due to their vulnerability and risk of contamination.
Blarasin, M., A. Cabrera y D. Caffaratti. Una experiencia pedagógica innovadora en la enseñanza de la Hidrogeología con alumnos de quinto año de la licenciatura en Geología. Aceptado para ser publicado en las Actas del I Taller Cubano de Hidrogeología, Noviembre de 1996. Topes de Collantes, Cuba.
Contact:
M. Blarasin
Dpto. de Geología, Fac. Cs. Ex., Fco.-Qcas. y Nat.
UNRC
Enlace rutas 8 y 36, Km 601
(5800) Río Cuarto
Córdoba. Argentina.
A geohydrological investigation was carried out in Cordoba province, Argentina, to assess the suitability and to plan the use of a phreatic aquifer which is subject to all types of uses (human, livestock and irrigation). The study area is an extensive plain (llanura) made up of alluvial and aeolian materials, crossed by a regional geological fault that divides it in two sectors (a lower and an elevated block), each with clear geomorphological, hydrodynamical and hydrochemical differences.
The lower block presents greatly evolved waters due to the collection of regional circulation flow. The waters are brackish and saline, of the sodium sulfate and chloride types. The suitability of the groundwater resource of this block turned out to be not for human consumption or for irrigation due to the high content of total dissolved solids, and from good to tolerable for livestock.
The elevated block, to the west of the fault, is a hill of regional magnitude, with the flow lines diverging from an area more topographically elevated which generates a local area of recharge that improves the water quality of the aquifer. Here, the waters are fresh, of the bicarbonate sodium type, although there exist high levels of arsenic and fluorine. This water is not suitable for human consumption due to its high content of As and F. It can be used for irrigation and is of good to excellent quality for livestock. The results of this study allowed it to be determined that the present use of the unconfined aquifer is not in accordance with the actual needs for use of the resource.
Cabrera, A. y M. Blarasin. Información de base para la planificación del uso de los recursos hídricos subterráneos en una zona con fuerte control estructural en la Llanura Argentina. Aceptado para ser publicado en las Actas del I Taller Cubano de Hidrogeología, Noviembre de 1996. Topes de Collantes, Cuba.
Contact:
A. Cabrera
Dpto. de Geología, Fac. Cs. Ex., Fco.-Qcas. y Nat.
UNRC
Enlace rutas 8 y 36, Km 601
(5800) Río Cuarto
Córdoba. Argentina.
Sarasota County, Florida, USA, is known to have high concentrations of radium-226 in the groundwater. The maximun permissible level of radium for water suppplies established by the U.S. Environmental Protection agency is 20 picocuries/liter (pCi/l). The State of Florica has a maximum of 5.0 pCi/l.
Groundwater discharges to surface water, and rivers and estuaries in this area become enriched in radium. The Gulf of Mexico also produces radium from geothermal springs, some with concentrations above 50 pCi/l.
In 1986-1987, grounwater samples were collected from private drinking water wells and a contour map of radium-226 was prepared for coastal Sarasota County. Several areas have concentrations above 5.0 and values exceed 20 pCi/l in two small areas. The relatively high concentrations appear to result from movement of groundwater through uranium rich geologic formations coupled with chloride and low pH.
Walters, M.O.; Radium in Coastal Sarasota County Ground Water, Ground Water Monitoring and Remediation, Vol. 15, No 4, Fall 1995, pp. 114-118.
Contact:
M.O. Walters
Dames & Moore, Inc.
1 N Dale Mabry Hwy Ste 700
Tampa FL 33609
USA
An aquifer remediation concept is prorosed where a well is used as an in ground "stripping tower". Air is injected at the bottom of a well causing the water column to fill with rising air bubbles. At the top of the well casing, the vapor is taken off and the stripped water is carried some distance away and allowed to percolate back to the water table.
A model was constructed and the concept was tested using three compounds: trichloroethylene (TCE), chloroform and toluene. The removal rates of these compounds were monitored using eight triple level observation wells.
The concentrations were reduced showing that this method holds promise for field application. The conitnuous circulating flow field between pumping well and the percolation area caused variation in remediation efficiency both in time and space.
Gvirtzman, H. and O. Gonen; Feasibility Study of In-Well Vapor Stripping Using Airlift Pumping, Ground Water Monitoring and Remediation, Vol. 15, No 4, Fall 1995, pp. 155-162.
Contact:
H. Gvirtzman
Institute of Earth Sciences
The Hebrew University of Jerusalem
Jerusalem 91904
Israel
Colloids in groundwater can adsorb and carry a variety of contaminants. This study looks at the transport of a cesium tracer, (137Cs), on colloidal kaolinite in sand columns.
The main cesium pulse decreased by more than one-half as the concentration of kaolinite in the inflowing water to the column increased from 0 to 200 mg/l. A small amount of cesium appears early, probably due to adsorption on the kaolinite that is controlled by kinetics.
The early breakthrough was unretarded compared to a retardation of 15 pore volumes with no kaolinite in the water. The study results show that there is a need to recognize the enhanced transport of contaminants on colloids and provide a method for quantifying this phenomenon.
Saiers, J.E. and G.M. Hornberger; The Role of Colloidal Kaolinite in the Transport of Cesium through Laboratory Columns, Water Resources Research, Vol. 32, No. 1, pp. 33-41, January 1996.
Contact:
J.E. Saiers
Dept. of Geology
Florida International University
Miami, FL 33199
USA
Contamination can spread from an area where chlorinated hydrocarbons have been spilled by transport of vapors in the unsaturated zone. Groundwater may become contaminated by vapor migration to the capillary fringe, a rising water table or infiltration of recharge through the vapor zone.
Field experiments were carried out to provide a detailed picture of the transport of trichloroethylene vapors in the unstaurated zone. Both winter and summer conditions were considered. Observed results were simulated using both diffusion and density driven advection.
Aa very good match was obtained between the experiment and simulations. Vapor plumes spread several meters from the spill and moved into the capillary fringe in just a few days. Transport was dominated by diffusion, and under summer conditions density driven advection was significant. Site geology caused transport to be insensitive to surface boundary conditions.
Conant, B.H., R.W. Gillham, and C.A. Mendoza; Vapor Transport of Trichloroethylene in the Unsaturated Zone: Field and Numerical Modeling Techniques, Water Resources Research, Vol. 32, No. 1, pp. 9-22, January 1996.
Contact:
B.H. Conant
636 Red Pine Dr.
Waterloo, Ontario
N2V 1S1, Canada
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