Principles and Problems of Environmental Pollution of Groundwater Resources with Case Examples from Developing Countries B

Exhibit HHHH Environmental Health Perspectives Vol. 83, pp. 39-68, 1989

Principles and Problems of Environmental Pollution of Groundwater Resources with Case Examples from Developing Countries B. C. E. Egboka,* G. 1. Nwankwor,t 1. P. Orajaka,* and A. 0. Ejiofor*

The principles and problems of environmental pollution and contamination are outlined. Emphasis is given to case examples from developing countries of Africa, Asia, and Latin America with a comparative analysis to developed countries. The problems of pollution/contamination are widespread in developed countries but are gradually spreading from the urban to rural areas in the developing countries. Great efforts in research and control programs to check pollution-loading into the environment have been made in the industrialized countries, but only negligible actions have been taken in developing countries. Pol- lutants emanate from both point and distributed sources and have adversely affected both surface water and groundwaters. The influences of the geologic and hydrologic cycles that exacerbate the incidences of pollution/contamination have not been well understood by environmental planners and managers. Profes- sionals in the different areas of pollution control projects, particularly in developing countries, lack the integrated multiobjective approaches and techniques in problem solving. Such countries as Nigeria, Kenya, Brazil, and India are now menaced by pollution hazards. Appropriate methods of control are hereby suggested.

Introduction for research to combat and control widespread pollutants and contaminants. Volumes of these pollutants/ Environmental pollution and contamination are be- contaminants are produced yearly through natural and coming a common occurrence in parts of the developing anthropogenic activities such as industrial activities, ag- world. It is difficult to distinguish precisely between ricultural practices, waste disposal systems, etc. High- pollution and contamination. In modern hydrogeologic level, medium-level, and low-level wastes in solid, liq- literature, pollution is regarded as occurring in such uid, or gaseous forms are released into the environment high dosages or concentrations that it renders the pol- at discrete intervals or on a continuous basis. These luted medium very hazardous or highly deleterious to pollutants may be physical, chemical, biochemical, bi- biota. Contamination may occur to a lesser magnitude ological, or microbiological in nature. They may have when compared to pollution, but it also may render the short or long half-lives in the environment. They have contaminated medium unusable or make it slightly haz- continued to damage many environments of the indus- ardous to life. Many urban and rural areas of the de- trialized countries, having defied many painstaking con- veloped or industrialized world have been adversely af- trol programs (1,2). Many urban centers of developing fected by large-scale pollution and contamination, countries are now also similarly threatened. Unfortu- resulting in losses of human, material and financial re- nately, these poor countries lack the necessary exper- sources. In many American, European, and Asiatic tise and funds to wage any meaningful war against pol- countries, huge amounts of money are spent annually lution, which continues to spread unabated. Parts of the environment currently being polluted *Water Resources and Environmental Pollution Unit, Department include the atmosphere, pedosphere, hydrosphere, lith- of Geological Sciences, Anambra State University of Technology, P.M.B. 5025, Awka Campus, Awka, Nigeria. osphere, and biosphere. This paper shall focus on pol- tSchool of Applied and Natural Sciences, Federal University of lution/contamination of the hydrosphere, with particu- Technology, P.M.B. 1526, Owerri, Nigeria. lar emphasis on the groundwater regime, and pollution tDepartment of Applied Microbiology, Anambra State University incidences in developing countries. The scope shall em- of Technology, P.M.B. 5025, Awka Campus, Awka, Nigeria. brace Address reprint requests to B. C. E. Egboka, Water Resources sources and types of pollution/contamination, and Environmental Pollution Unit, Department of Geological Sci- processes generating them, implications of geology/hy- ences, Anambra State University of Technology, P.M.B. 5025, Awka drogeology, and pollution dynamics and mechanisms. Campus, Awka, Nigeria. Potentials of groundwater pollution in developing coun- 40 EGBOKA ET AL. tries vis-a-vis the developed ones shall be outlined, high- Table 1. Point sources of pollution and contamination. lighting their health hazards. Relevant suggestions for combating pollution more effectively shall be made. The Type of pollution Examples Sewage disposal systems Sewage lagoons primary objective is to review the general incidences of Septic systems environmental pollution/contamination in relation to the Cesspools effects of pedology and geology in close association with Barnyards/feed lots the dynamics of the hydrologic cycle. Proper under- Surface waste disposal sites Landfills/garbage dumps Surface waste dumps standing of sources and types of pollutants/contami- Underground waste disposal sites Storage tanks (low-, medium-, nants and their genesis and hydrodynamics would help high-level wastes) determine the appropriate control measures to be con- Pit latrines, tunnels, trenches, sidered for the situation. The goal is to contribute to caves better control methods. It is believed that present con- Waste subsurface injections Spills, washings, and intrusions Oil/gas/waste spills trol methods in parts of the world lack the depth of Auto workshop washings understanding required. In addition, many ofthese con- Research/laboratory washings trol efforts seem to be uncoordinated. Developing na- Seawater/saltwater intrusions tions still at the threshold of widespread pollution/con- Mining sources Acid mine drainages tamination could learn from the costly mistakes of the Gas explosions/seepages Mine dumps and gangue deposits industrialized nations and hence take the necessary ac- Tunnels/excavations outflows tions to protect their environments. Natural mineral/ore deposits Saline ponds/lakes The natural processes and anthropogenic activities Hot springs/mineralized waters that generate pollutants/contaminants are many and Anhydrite/pyrite deposits/ varied, and so are their sources. The natural processes evaporites include products of soil and gully erosion, physicochemical weathering and mass wasting, sediment transport, floods, volcanic eruptions, seawater intrusions, etc. The Table 2. Distributed sources of pollution and contamination (1). manmade ones include industrial, agricultural, sewage Source Examples wastes and lagoons, garbage dumps and barnyards, Agriculture Cropland mining wastes, etc. Pasture and rangeland These pollutants/contaminants in one way or the Irrigated land other via the cycle reach the groundwater Wood land hydrologic Feed lots systems to pollute/contaminate them. Through the cir- Silviculture Growing stock culation of water within the hydrologic cycle, pollutants Logging on the ground surface are transferred through the soil Road building zone into the aquifer horizons where they damage po- Construction Urban development Highway construction table water supplies. To reduce degradation of these Mining Surface water supplies, a comprehensive management strategy Underground is required, as discussed later. The present control tech- Terrestrial (many and scattered) Landfills niques with regard to pollution and contamination haz- Dumps Utility maintenance Highways and streets ards, particularly in developing countries, need to be Deicing greatly improved. Priority and concern are not shown Urban run-off Floods and snowmelt adequately by government authorities, and hence, ap- Precipitation Rainfall, snowfall, etc. propriate planning and management strategies to check Background sources Native forests pollution are generally absent. The expertise or req- Prairie land, etc. uisite manpower may be lacking. Funds for basic research may not be provided. Environmental protection laws or edicts may be nonexistent and where available (4). Point sources of pollution can be geometrically de- are rarely enforced. These have exacerbated the fined and the dimensions amenable to mathematical spreading phenomenon of many pollutants/contami- analysis in assessing pollution loads and rates of dis- nants in many developing countries. In this review, nec- charge determined. Point sources of pollution may as- essary suggestions for improvement of this situation sume any geometrical shape such as circular, triangular, shall be given. spherical, etc. The areal sources of pollutants/contaminants or leachates are comparatively smaller, easily mappable, and readily distinguishable. However, where Sources and Types of Pollutants/ the input/output load functions from point sources into Contaminants the hydrogeologic environment are continuous, the polluted/contaminated area may eventually become wide- The two main sources of pollutants/contaminants are spread. Distributed sources of pollutants/contaminants point sources (Table 1) and distributed sources (2) (Ta- are much more widespread and can rarely be geomet- ble 2). Pollutants/contaminants from the two sources rically defined as precisely as a point source. Hence, it may be released continuously (3) or at discrete intervals is more difficult to subject the input/output source to GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 41

precise mathematical analysis. Rather, a measured and thereby posing problems for mathematical analysis. The intelligent assumption of the affected area is made for sources include acid-alkaline rain, floods, erosion, ag- use in modeling and analysis. In heavily polluted/con- ricultural fertilizer applications, and generated agricul- taminated areas, both point sources and distributed tural wastes, seasprays and intrusions, volcanoes, etc. sources may be occurring together or may be indepen- Acid rain is a major distributed source of pollution in dent of one another. Successful control methods or developed countries such as the United States, Canada, mathematical modeling of the affected/polluted area Germany, etc. Localized pollution of groundwater by must recognize this situation in order for the control acid rain in some developing countries such as Nigeria program to be effective. has been reported (10). Surface waters and shallow groundwater are polluted by atmospheric fallouts (3,11- 13). In urban, suburban, and rural areas of many de- Point Sources of Pollution/Contamination veloping countries, particularly in the tropics, soil and In the list of point sources given in Table 1, the pol- gully erosion produce heavy sediment loads carried by lutants or contaminants come from zones or areas of floods that pollute surface water and groundwater sys- known and definable boundaries that are easily ame- tems (14-19). Waste products in urban areas are trans- nable to mathematical analysis and modeling. The pol- ported away by runoff. In mining areas, gangue ma- lution loads can be controlled at the point ofinput before terials dumped about recklessly on ground surface, they can spread into the surrounding environment in a decay and liquid wastes are leached from them becoming time-discrete or continuous manner. Point sources in- components of the hydrogeologic environment (20-22). clude sewage lagoons (solid, gaseous, and liquid), in- In regions of intense geomorphic degradation and mass- dustrial wastes, landfills/garbage dumps/barnyards, liq- wasting, physicochemical and biological weathering dis- uid/gaseous spills (oil, chemicals, etc.), mining (pits, integrate pedologic and geologic materials to produce holes, excavations, wastes, and gangue minerals), saline sediments that provide great quantities and varieties lakes and deposits, evaporite sequences, etc. Through of pollutants. Fallouts from volcanic activities or at- the complex interplay ofvarious soil and geologic factors mospheric tests in one area may be spread into other and rain/water events of the hydrologic cycle, pollutant/ regions of the world; wind, wave action, seaspray, or contaminant substances reach the groundwater systems saltwater intrusion may drive contaminants inland and to pollute them. For example, buried refuse or garbage road salt application for de-icing during winter and undergoes biodegradational decay in the pedologic/soil widespread fertilizer usage, particularly in developed zone. The resulting leachates are released into the countries, are also major distributed sources of pollu- groundwater flow system where dissolved geochemical tion. Similar events are now becoming prevalent in de- constituents are transported in various distances and veloping countries, particulary the industrializing ones. directions. Piled up animal wastes in barnyards or liquid wastes in lagoons are similarly leached out and transported causing pollution of surface waters and ground- Biological Pollutant/Contaminants in water areas. In many developing countries today, in- Groundwaters dustrial and domestic wastes are indiscriminately dumped into rivers, lakes, streams, dry valleys, etc. Biological pollutants of groundwaters include dis- This was the case in many developed countries, and such solved organic constituents and microorganisms that practices still persist in some of them today. These seep or leach into groundwaters from polluted surface wastes damage surface waters and eventually destroy waters. Microorganisms may contribute to pollution in parts of the groundwater regime. Mining wastes and many ways, namely they may themselves be patho- gangue products and other point sources of pollutants/ genic; aesthetically they may produce undesirable bio- contaminants produce similar havoc for the environ- mass, or they may generate toxic metabolites in the ment (4-9). groundwater. The microorganisms may be either pathogenic or nonpathogenic. In both cases, they produce undesirable effects in the groundwater itself and in the Distributed Sources of Pollution/ distribution network (where water may be distributed Contamination for domestic uses) and the populations using it. Distributed sources of pollutants/contaminants given Pathogenic Microorganisms. Pathogenic microor- in Table 2 are those in which the pollutants or contam- ganisms are present in groundwaters, especially in the inants are spread through a large area of hydrogeologic vicinity of facilities that are discharging sewage ef- environment and in which they extend over the entire fluents or contaminated surface waters, and new septic source area. A distributed source is very widespread, tanks, agricultural wastes, and refuse tips. Microor- and the pollutants/contaminants may be introduced ganisms, however, must survive the tortuous task of from various sources and directions. Spreading is en- passing through the soil cover, which constitutes an hanced by wind, rain, and snowfall activities through excellent natural process for water filtration and treat- atmospheric circulation and precipitation. The areal ex- ment. Even with this barrier, it follows that the nearer tent or boundary conditions for the pollutants are dif- these sources of pollution are to groundwater sources, ficult to define because ofthe regional nature of sources, the greater the chance of successful seepage of these 42 EGBOKA ET AL.

microorganisms. Shallow wells and some deep boreholes followed by a confirmatory test which is specific for E. are prone to contamination by these pathogens. coli (26). The isolation of pathogenic microorganisms from Nonpathogenic Microorganisms. Many nonpatho- groundwaters is difficult but, when achieved, it serves genic bacteria are as important as the pathogenic ones as obvious proof of potential danger to the users, re- in the pollution of surface water and groundwater sup- gardless ofthe number ofpathogens present. Generally, plies. These include the sulfur and iron bacteria. Among however, the majority of waterborne pathogenic mi- the sulfur bacteria are the sulfate reducers such as De- croorganisms enter water supplies as a result of fecal sulfovibrio, Desulfomonas, and Desulfotomaculatum, contamination. Therefore, the ability to detect fecal con- which produce elemental sulfur from sulfates. On the tamination at low levels is the main safeguard in pre- other hand, some ofthe sulfur bacteria oxidize elemental serving the potability ofwater supplies (23). Pathogenic sulfur to sulfates, all ofwhich involve complex oxidation- microorganisms normally associated with water sup- reduction reactions. These include the ubiquitous chem- plies are shown in Table 3 (24). All of these have been olithotrophic Thiobacillus and the filamentous gliding isolated from contaminated shallow wells and deep bore- bacteria Beggiatoa and Achromatium. The sulfur-oxi- holes in Kaduna, Kano, Niger, and Plateau States of dizing bacteria normally associated with groundwaters Nigeria (25). In addition, Dracunculus medinesis (Gui- have been described by Trudinger (27), LeGall and Post- neaworm) was reported from wells in parts of Nigeria gate (28), and Ehrlich (29) (Table 4). such as in Kwara State (25). These parasites are wide- Iron bacteria are frequently present in groundwaters spread in many parts of Nigeria, sometimes occurring and in particular those subject to a degree of organic in epidemic proportions. pollution. They obtain energy for their metabolism by Fecal contamination in water is usually demonstrated the oxidation of ferrous and/or manganous ions. These by the detection of specific bacteria that are present in include the gliding bacteria Toxothrix; the sheathed bac- very large numbers in the intestines. The test normally teria, Spaethilus, Leptothrix, Crenothrix, and Clono- employed is the presumptive Coliform test, which in- thrix; the budding and/or appendage bacteria, Pedom- volves the most probable number (MPN) counts using icrobium, Gallionella, Metallogenium, and Kusnezovia liquid media. Coliform organisms include Escherichia and the gram-negative chemolithotrophic bacteria, coli, Citrobacter, Klebsiella, and Enterobacter spp., Thiobacillus (T. ferrooxidans), Siderocapsa, Nauman- which are members of the family Enterobacteriaceae. iella, Ochrobium, and Siderococcus (30). Pathogenic and They are gram-negative, oxidase-negative, nonspore- nonpathogenic microorganisms (bacteria, fungi, vi- forming rods that can grow aerobically in a medium ruses) are thus hazardous environmental pollutants to containing bile salts. They are able to ferment lactose the hydrogeologic environment. They enter this envi- within 48 hr, producing acid and gas at 37°C. A pre- ronment from waste disposal and treatment areas, sew- sumptive coliform test with a very high count is usually age lagoons, barnyards, landfills, and mine areas (31).

Table 3. Pathogens associated with water supplies. Pathogens Diseases caused Bacterial Salmonella typhis Typhoid fever Salmonella paratyphi A and B Paratyphoid fever Salmonella typhimurium Salmonellosis Shigella sonnei Shigella dysenteriae Bacillary dysentery Shigella flexneri Hycobacterium tuberculosis Tuberculosis Vibrio cholerae Cholera Francisella tularensis Tularaemia Enteropathogenic Esherichia coli Enteritis Leptospira icterohaemorrhagia Leptospirosis Viral Hepatitis A virus Viral hepatitis Type A Enteroviruses (polio, Coxsackie A and B and echo) Respiratory tract infection, nonbacterial Adenoviruses enteritis Parvoviruses Reoviruses Protozoan and metazoan Enteamoeba histolytica Amoebic dysentery Acanthamoeba spp. Amoebic meningoencephalitis Naegleria spp. Amoebic meningoencephalitis Giardia lamblia Giardiasis Ascaris lumbricoides Helminthiasis Thichuris trichura Taenia spp. GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 43

Table 4. Sulfur oxidizing bacteria in groundwaters. the life in the lake but also that of the groundwater system associated with the lake. Other problems that Genus or group Habitat can arise are the changing of physical, chemical, and Chemotrophs Sulfobacillus Mine tips biological characteristics of the hydrogeologic system, Thiobacillus Water, soil, marine thereby rendering the surface water and groundwater Sulfolobus Geothermal springs unusable. Thiobacferium Water In many parts of the world, the locations of geo- Macromonas Water Thiovulum Water thermal pollution hazards are known. Geothermal pol- Thiospira Water lution is much more common in tectonically unstable Beggiatoa Water, soil, marine environments where high temperature effluents and Thioploca Water, soil gases emanate from deep horizons or the core within Thiothrix Water, soil, marine the earth. They move up to the shallow hydrogeologic Achromatium Water Thiodendron Water, soil zones through fractures (joints, faults, shear zones) and Phototrophs heat up surrounding groundwaters to generate hot and Chromatiaceae (purple S bacteria) Water, marine warm springs. In addition to the hotness ofsuch waters, Chlorobiaceae (green S bacteria) Water, marine they are also highly mineralized because the high tem- Chloroflexaceae Geothermal springs peratures enhance the dissolution of soil and geologic Oscillatoria (Blue-green algae) Water materials.

They occur in varying degrees in both oxidizing and Geologic and Hydrologic- Cycles reducing environments. In the process ofcomplex redox activities that break down organic and inorganic ma- Pedologic, geologic, and hydrologic cycles have sev- terials to release energy for metabolic activities, poi- eral components and characteristics that enhance or ag- sonous substances are generated that may be fatal to gravate the incidences of pollutant/contaminant origin, the hosts that ingest them. These redox microbial ac- transport, and spread through hydrodynamic dispersion tivities may also degrade their habitats, rendering them (diffusion, advection and dispersion) into the hydrogeo- unusable. Such degraded states may remain so for a logic environments that embrace the atmosphere, pe- long time. dosphere, lithosphere, hydrosphere, and biosphere. Organic Pollutants in Groundwater Geologic Cycle Organic pollutants that may be found in groundwater Geologic rock units may be fractured, faulted, and through shallow wells and deep boreholes include dis- jointed during tectonic movements or may be layered solved organic carbon (DOC) and particulate organic during the deposition and consolidation of sediments. carbon (POC). They, in association with microorgan- Weathering disaggregates rocks into soils and sedi- isms, cause destructive pollution or contamination in ments that are transported away by wind, water, and/ hydrogeologic environments. They may serve as nu- or man. During these processes of the geologic cycle, trient/energy sources for microorganisms. Where they pollutants and contaminants may be formed or released. are heavily loaded into groundwaters, DOC and POC Figure 1 shows significant parts of the complex geologic enhance microbial multiplication and growth, thereby cycle that are relevant to groundwater pollution. Soil rendering the habitat anoxic. In such environments, and geologic characteristics vary in horizontal, lateral, denitrification, desulfurization, etc., are rampant, en- and vertical directions. Soil characteristics include grain gendering an abundant growth of bacteria, fungi, and size, porosity, permeability, stress-strength properties, viruses that may be highly pathogenic. Hence, serious cohesiveness, and other physical and chemical proper- organic pollution signals a potential heavy microbial pol- ties. The soil components of unconsolidated geologic lution of a groundwater system. units that form aquifers have similar physicochemical characteristics. Additionally, layering or stratification properties of both consolidated and unconsolidated geo- Thermal Pollution/Contamination logic units are factors that affect pollutant/contaminant Thermal pollution/contamination may result from two inputs, transport and dispersion. Stratigraphic prop- main sources, namely, industrial and geothermal pol- erties of directional lithologic changes, facies changes, lution. In industrialized countries and some developing stratification and stratal thicknesses, degrees of sedi- ones, heat generated by industries is discharged mentation, cementation, and diagenetic changes affect through wastewater into the environment. High tem- the life of pollutants/contaminants in groundwater perature waters eventually reach shallow aquifers and (Fig. 2) (14). The structural characteristics of fractures, adversely affect groundwater. Hot waters discharged faults, joints, and folds (Fig. 3) of igneous and meta- into lakes that are influent may form high temperature morphic rocks and consolidated sedimentary rocks are haloes that extend into the aquifers underlying the lake. also significant in groundwater pollution and contami- Unchecked thermal pollution not only negatively affects nation. 44 EGBOKA ET AL.

Anticline Anticline

(a) FOLD Syncline

Sand ----40 Shale - Gravelly ______Sand (b) JOINTS Sandstone e Limestone. o*. Joints Gravelly 10 A a 1 4- Sandstone 'a.' -O. PS - 'A:--c4-7'.4,6"

Fault Line/Face/Zone (C) FAULT Downthrown_,_...,:\ FIGURE 1. Geologic cycle. Sandstone - Shale -. (a) Horizontal Stratification and Facies Changes Gravelly - A. Sandstone >Upthrown Side -i - * DIRECTION OF MOVEMENT

Fault Lines

Igneous Roc Sandstone Aquiclude Aquifer

(b) Layering and Vertlcal Statification Ground Surface DIRECTION OF INPUT Water Table

i I I noIkMMSoil'I ZoneV r * * .W Sand .a ble Permeable Aquifer FIGURE 3. (a) Folds, (b) joints, (c) fault, (d) graben.

Impermeable --. Aqutard erties and characteristics in design and control pro- * ,' ' * , e * Sand *.* & s * * Aquifer Confined grams, thereby creating situations that frequently pro- Permeable * . . -. * duce failures in engineered structures.

Rock Aquiclude Impermeable Hydrologic Cycle FIGURE 2. Lithologic changes. The several processes as briefly outlined below that occur within the hydrologic cycle (Fig. 4) are the driving forces and agents of groundwater pollution. The at- Subsequent discussions of the geologic and hydro- mosphere serves as the gaseous envelope surrounding geologic settings shall explain further the obvious im- the earth. Precipitation through condensation of rain plications of these properties in the genesis, transport, clouds falls down to earth as rain, snow, hail, etc. At- and dispersion of pollutants/contaminants in ground- mospheric pollutants and contaminants may be washed water flow systems. It will then be clear that any suc- out of the atmosphere as fallout. Runoff carries pollu- cessful stoppage or control of groundwater pollutants tants into surface waters for possible evaporation back and contaminants must take into serious consideration into the atmosphere or storage in rivers, streams, lakes, the implications of geologic and hydrogeologic charac- and oceans, seas, etc. Some ofthe fallout or rainout may teristics of the particular polluted or threatened envi- infiltrate into the soil zone to be evapotranspired to the ronment. Currently, pollution/contamination planners atmosphere or percolate into the groundwater zone. and managers do not seriously consider geologic prop- Here moisture joins a complex hydrodynamic flow sys- GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 45

Surface Water Divide Groundwater / Divide Groundwate Recharge / \* * 9 1 * w \ DISCHARGE Watertable

U. * .. *-Groundwater Flow ~~.~~~~~~ Bedrock '.~~ i5E-~~(Aquiclude) ',

FIGURE 4. The hydrologic cycle. tem possibly to be transported to the oceans or other and hydrosphere) through the activities of air, water, surface waters where evaporation may return the water chemical, physical, and microbiological processes. These back to the atmosphere. In all these processes, pollu- complex and cyclic processes may be continuous with tants and contaminants may be produced and cyclically respect to distance and time and may be localized or dispersed from one point of the hydrologic cycle to an- regional in areal spread. Thus, pollution at one source other. This is graphically shown in the cyclic pollution/ or an area may threaten nearby or distant places unless contamination of the hydrogeologic system otherwise its spread is checked or controlled. called the hydrogeopollution cycle (Fig. 5). Pollutants The implications of the geologic and hydrologic cycles and contaminants may be generated through natural or are much more pronounced when one relates them to anthropogenic processes and circulated in the environ- the long half-lives and transport of high-level radioac- ment (atmosphere, pedosphere, lithosphere, biosphere, tive wastes from industries. These materials are being stockpiled in different parts ofthe industrialized nations and some developing countries waiting to be safely disposed of in secure geologic rock units. It is now known that even deep-seated geologic hard rock formations have cracks, joints, and even faults through which mov- ing groundwaters can transport pollutants/contaminants in many directions. It is also possible that the grain size and lattice structure of such rock units may permit widescale diffusion/dispersion of gaseous/liquid pollutants that may eventually threaten the biospheric environment with time. Hence, structural and stratigraphic characteristics of geologic units and the hydrodynamics of percolating or flowing groundwaters must prominently occupy the minds of planners, designers, and managers of waste disposal and management systems. Unfortunately, at present, this has not been the case, particularly in developing countries where pollution/contamination is becoming more commonplace. Even though those in developed countries now consider geologic and hydrogeologic effects, it has been late in coming, and pollution has ravaged many areas, precip- itating devastating losses in financial, water, land, and human resources. Even with graphic examples that il- FIGURE 5. The hydrogeopollution cycle. lustrate the consequences of poor planning, many plan- 46 EGBOKA ET AL.

ners and managers are still skeptical about the role of nor vegetation contributes dissolved substances to the geology in environmental pollution. At the same time, groundwater it contains. Areas ofpure quartz sand dune the lack of consideration of geologic, pedologic, and hy- are few. Most surface soils and water-bearing forma- drologic/hydrogeopollution cycles has not been fully ap- tions are not pure quartz sandstone. A sandstone is preciated in developing countries. There does not seem made up of soil particles of different mineralogy. These to be enough consciousness given to understanding the particles are bound together by cementing materials, implications of these cycles. Because of this, no priority which are generally calcite, hematite, or silica. In con- is given to examining the impact of pollution incidences trast to quartz sand, surface materials of soils, lime- and the consequences of spread in the hydrogeologic stone, shale, and other lithologic types react with per- environments. colating and infiltrating water to produce dissolved materials that pollute groundwater (Figs. 4 and 5). Any groundwater system may be naturally polluted Processes and Activities Generating or contaminated to a certain degree at all times. The Pollutants/Contaminants concern of many water resource planners and managers is whether the amount ofmeasured pollutants are within Various processes, some of which may be manmade the acceptable limits of water quality. The number of or anthropogenic, generate pollutants and contaminants chemical pollutants and the degree ofchemical pollution/ that enter groundwater flow systems. These processes contamination of groundwater depend on the geology, include physicochemical weathering, mass wasting, ero- pedology, and the mineral composition of the soil and sion, sediment transport, and deposition; agricultural rock through which the water flows before reaching the activities; mining, mine-waste disposal, and acid mine aquifers. Groundwaters may have pollutants that not drainage problems; oil exploration, exploitation, and gas only depend on the pedology, geology, and mineralogy flaring; other industrial activities such as manufactur- of the formations it flows through but also on the con- ing, distribution of manufactured products, arms, and stituent pollutants/contaminants in the water that re- armaments, etc.; sewage treatment, disposal, and man- charges the groundwater. agement; runoff, floods, and snowmelt; biological pol- Recharge water, on the other hand, may be contam- lution of wetlands and impounded reservoirs; saline inated by atmospheric fallout, industrial and domestic lakes, ponds, and evaporite deposits; geothermal wastes, etc. The type of physical, economic, agricul- springs and mineralized waters; atmospheric fallout and tural, and social activities of the people living in a rainout; burial grounds, garbage dumps, landfills, etc. groundwater recharge area (Fig. 6) may affect its water Some pollution sources in rural environments that are quality. Thus, urban planners and managers must be usually ignored, even though they may be hazardous, wary of human activities that occur in recharge areas include pit latrines, open-space communal toilets, of aquifers in urban and rural areas. This is one of the widescale and indiscriminate uses of the bush for def- main avenues by which pollutants or contaminants enter ecation, personal hygienic uses of water for washings, the groundwater. Hydrogeologic maps of the areas are etc., microbiological activities (bacteria, virus, fungi, lacking or have not been produced, so the recharge worms, etc.), radioactive material, and thermal prod- areas are not identified. This problem affects both de- ucts, heavy metals, trace elements, ions, etc. veloped and developing countries. Massive pollution of groundwater systems is a common occurrence because Chemical Pollutants/Contaminants of wastes are recklessly deposited on top of recharge areas. Groundwater Groundwater pollution is an ever present risk in de- Many developing countries are witnessing a stage of veloping countries, particularly in areas of mining and development where groundwaters from shallow wells extensive industrial activities. This must constantly be and boreholes are gradually supplementing the original in the minds of those responsible for water supplies in source of drinking water (surface water). The prefer- these areas. Borehole waters must, as a rule, be ana- ence for groundwater to surface water is borne out of lyzed for chemical contaminants before the water is dis- the belief that when surface water has been distributed tributed and supplied to households. Unsatisfactory as tap water it must always be subjected to some pu- color and taste are easily detected and are good indi- rification prior to distribution. Although surface waters cators for groundwaters of poor quality. Some ground- are easily accessible where they exist in lakes, rivers, waters taste of iron, others may have a disagreeable streams, and springs, many people believe that water odor. Such groundwaters should be avoided and not wells produce water of excellent quality. Thus, ground- used for domestic purposes. Water containing only sev- water is not treated before use and is believed to be eral parts per million of sodium and chloride ions tastes free from pollution. slightly salty. Lead and sulfur are distasteful when pres- One place where one can find groundwater about as ent in appreciable quantities in water. Conversely, how- pure as rainwater is under a bare dune made of pure ever, some toxic elements have no taste, but when pres- quartz sand (32). The water under quartz sandstone is ent in very small quantities may be dangerous to health. clean and pure because quartz is so insoluble in water Very small concentrations of poisonous trace elements that for practical purposes, it is inert and neither soil such as lead, arsenic, mercury, cyanide, and boron must GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 47

removed through filtration in charcoal, through cation Pflollutant Source exchange, precipitation, dissolution, degassing, etc. (a) Recharge Zone The treatments may be expensive and may result in the creation of new pollutants and contaminants and their introduction into the treated waters. In developed coun- Zone of Groundwater tries, waters supplied for public use are routinely ana- Contamination lyzed to certify that the content of toxic elements or contaminants are below mandatory limits. In many de-

Surface Water veloping countries, groundwaters and even surface waters are often distributed to various communities untreated. In general, it is wrongly believed that exploited groundwaters are free of pollution. Emphasis is usually placed on water supply and quantity, and minimal prior- * . : e. . Aquifer ity is given to water quality and treatment. This is the main cause of outbreaks of epidemics of waterborne diseases in many developing countries because untreated surface water and groundwater are consumed by the people, particularly in rural areas, without water treatment. Since there are no monitoring programs, it (b) Discharge Zone is not possible to detect incidences of pollution. The most undesirable trace elements-pollutants in groundwater are mercury (Hg), lead (Pb), cadmium *\. \ \ ~~Pollutant Source Zone of Contamination (Cd), arsenic (As), barium (Ba), boron (B), cyanide (CN) selenium (Se), chromium (Cr), uranium (U), sulfur (S), Sce Water and nitrogen (N). The United States Food and Drug Administration has specified the lower mandatory limits of these elements in domestic water. In addition, there Aquifer are internationally accepted water quality guidelines for concentrations of these elements in water for various uses. Most groundwaters may also contain many major inorganic elements, compounds, and ions in excess of FIGURE 6. Schematic illustration of the extent of groundwater con- acceptable standards, such as iron oxide (Fe2O3), man- tamination for pollutants entering (a) recharge and (b) discharge ganese (Mn), calcium (Ca), magnesium (Mg), chloride zones. (Cl), aluminum (Al) and silica (SiO2). Anions and cations can be found in their dissolved states. Temperature, be carefully documented. Water sampling and monitor- where high, affects the properties of groundwater, es- ing may reveal their presence. pecially the solubility of minerals. Deep groundwaters The three components of water quality are bacterio- contain more chemical elements dissolved in them than logical quality, physical quality, and chemical quality. do shallow ones. Very deep, hot groundwaters may be Filtration and sedimentation processes take care of the objectionable because they contain very high concen- physical quality. In practice, groundwaters are filtered trations of these mineralized elements dissolved out of by natural processes as they pass through columns of rocks by the high temperatures. This is characteristic soils, sands, strata, or sedimentary layers of rocks. of hydrogeothermal regions. Groundwaters are usually clear of solid materials as Groundwaters in limestone or Karstic terrains may they come from the aquifer, particulary ifthey are deep- contain dissolved calcium and magnesium salts. These seated ones. The intricate pore spaces or water pas- salts make water hard. Hardness in excess affects taste sageways of the aquifer materials act as a fine filter and and soap consumption in laundry. Temporary hardness remove small particles of clay or any other fines. Or- is caused by carbonates and bicarbonates of calcium and ganic materials decay or are destroyed in transit. Thus, magnesium; permanent hardness is caused by sulfates, the dirtiest and most polluted sewage water may be- chlorides, nitrates, and silicates of calcium and mag- come clear of suspended/particulate solid materials once nesium. The combination of both ofthese groups of sub- it has gone through a thick bed of sand or geologic and stances gives total hardness. Hard water may also have pedologic units. As a result of this natural self-cleansing a slight taste that is caused by other ions in solution. of polluted water by deep-seated aquifers, physical and A few groundwaters naturally become softened as some biological aspects ofpollution may not pose serious they pass through and react with geologic formations problems in groundwaters. containing zeolite minerals, which remove calcium and Bacteriological quality of groundwater is taken care other ions. Zeolites and hydrous silicates chemically ex- of by treatment with various chemicals that kill bac- change certain ions from water for other ions bound in teria. Dissolved geochemical constituents, on the other the solids. If, for example, water carrying calcium ions hand, are difficult to remove entirely. They may be travels through a zeolite formation that exchanges Na+ 48 EGBOKA ET AL.

for Ca2", the water comes out with sodium instead of can leach pollutants from mine dumps, ore deposits, city calcium and the zeolite becomes richer in Ca and poorer dumps, and fertilizer applied to farm lands into the re- in Na. charge areas for groundwater supplies (Fig. 6). Iron in water gives a bitter taste and makes water Groundwaters recharged from polluted areas must reddish or brownish in color. It is found in the form of either be avoided or pollution sources checked and mon- bicarbonates and sulfates. Iron in groundwater is due itored very carefully. The geology of recharge areas of to the presence of hematite below the ground surface. aquifers influences the quality of groundwater. The Iron is soluble in water containing carbonic acid. Water number of pollutants and the degree of pollution in containing high iron is unsuitable for laundries, paper groundwaters depend on the geology and the minera- mills, film industries, etc. logical compositions of the rocks through which the Manganese acts in a manner similar to iron. It pro- water flows. Groundwaters may also acquire pollutants duces an undesirable taste, and white clothes washed and contaminants as they flow across difference geolog- in water containing manganese or iron turn yellow or ical and mineralogic zones or units of formations. Chem- brown. In small concentrations, Mn affects odor. Iron ical reactions between the water and rock fragments in and Mn in water precipitate and produce undesirable the soil and numerous chemical and physicochemical re- turbid yellow-brown water that stains laundry. These actions between water and rock in the groundwater elements support growth of microorganisms in distri- environment alter the composition of the groundwater. bution systems. These growths can accumulate and re- Surface waters recharged by surface water draining duce the carrying capacity of pipes and clog valves. through limestone areas may be hard and need consid- Small concentrations of Fe and Mn impart a metallic erable softening treatment before being supplied for taste to water. Groundwater supplies contain more Mn domestic and industrial use. Rainwater absorbs carbon and Fe than surface waters. dioxide in the air, forming carbonic acids, which react Excess carbon dioxide in water makes water corro- with limestone, liberating bicarbonates and carbonates sive to metals. It can be present in the form of carbonic which, when added to percolating groundwaters, make acid, bicarbonate, carbonate or as free carbon dioxide them hard. Surface materials of soils and shale react (CO2). Groundwaters drawn from great depths are de- with rain to produce dissolved materials that contribute ficient in dissolved oxygen (DO). Shallow groundwaters to the taste and color of groundwaters. The taste and are usually saturated with dissolved oxygen. Hydrogen color of such waters depend on the composition of the sulfide (H2S) makes water unpalatable because of bad rocks through which the water passes. Surface waters odor and taste. It is found in groundwaters where sul- draining metamorphic areas containing talc dissolve fide minerals such as galena, pyrite, sphalerite, etc., magnesium salts that contribute to the hardness of are present. Other dissolved gases in addition to CO2, groundwater. DO, and H2S that may cause pollution problems in Surface water draining areas of sulfide mineralization groundwater include nitrogen dioxide (4,33), methane introduce sulfur and many other metallic ions into (31), and sulfur dioxide. They cause degrees of hazard groundwaters. The chemical characteristics of ground- in hydrogeologic systems that are functions of concen- water vary greatly as a result of the diversity of rock tration but are hazards that can be removed during materials through which the water passes. Sedimentary water treatment processes. rocks provide the largest aquifers and water passing through such rocks acquire considerable concentrations ofchemical components ofthese rocks. Carbonate rocks, Geologic and Hydrogeologic such as limestone and dolomite dissolve easily in acid Settings water with the result that water in contact with these rocks are high in calcium and magnesium bicarbonates. Geologic Settings In igneous and metamorphic terrains, groundwater oc- Natural geological processes are primary contribu- curs in weathered parts ofthe basement rocks or faults, tors to groundwater pollution. In this regard, the rocks joints, and fissures. Rainwater percolating through of the earth's crust are the major contributors of these fissures dissolve many soluble elements. The groundwater pollutants (Figs. 1 and 5). These contam- groundwater in basement areas may be contaminated inants are mostly minerals, gases, and the toxic ele- by ions dissolved from the basement rocks (Fig. 3). ments they contain. A good understanding ofthe origin, Weathering and oxidation of basement rocks create occurrence, and distribution of these undesirable ele- a favorable acid environment for mobilization of many ments is essential for people concerned with the devel- metals. Weathering and fracturing of basement rocks opment of surface water and groundwater resources. also create porosity necessary for storing water. Con- Contaminants enter groundwaters from the recharge sider a granite containing about 5 ppm of uranium in areas ofaquifers. It is therefore very necessary to know solution. During weathering uranium will be oxidized the geology and mineral distribution in recharge areas to the soluble uranyl oxide in the near surface weath- of aquifers. Groundwater that is recharged from mining ering environment. The oxidized uranium is then mo- areas, fertilized agricultural farmlands, and industrial bilized and dissolved in shallow groundwater in the areas may not be safe for human consumption unless basement area. Data from Trenthan and Orajaka (34) the recharge area is protected. Rain and surface water and Orajaka (35) show that significant amounts of ura- GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 49

nium are leached and mobilized from felsic igneous rock derstanding of contaminant processes. The various as- by carbonic acid water. A significant quantity of ura- pects ofthe groundwater environments, as well as strat- nium is leached from the albite-riebeckite-granite in igraphic factors that control or could influence Kaffo Valley, Northern Nigeria, during weathering of groundwater motion, are also of major consideration. the roof of the granite mass (36). This example illus- The hydrogeological environment is shown schemati- trates how abnormally high uranium and other major, cally in Figures 2 and 4. It consists mainly of the sat- minor, and trace elements are leached and introduced urated and unsaturated zones. The unsaturated zone into shallow groundwaters in the veins, fissures, and occurs above the capillary fringe where the soil pores porous parts of basement rocks. are partially saturated with water. This zone is impor- It is thus important to test all shallow groundwaters tant in waste management because in most cases, it is in basement or hard rock areas for metal contamination the burial zones for wastes. Consequently, a thick un- before supplying such water to homes and industries. saturated zone may sometimes be preferred for waste In many developing countries, rural dwellers obtain disposal since it would take a much longer time for con- their water from shallow, hand-dug wells (37). In most taminants to reach the water table. In the saturated cases where the water is tested, they are usually con- zone, the pores are saturated with water. When this taminated, particularly for shallow wells in urban cen- zone is capable of transmitting significant quantities of ters situated in basement rock areas. Toxic metals, no- water for economic use it is referred to as an aquifer. tably Pb from weathering products of ores in In most field situations, two or more aquifers occur, mineralized veins of faults and fissures, can enter nat- separated by impermeable strata or aquitards. In the ural water systems. The metal concentrations are ab- situation illustrated in Figure 2, the upper or unconfined normally high for water descending through fissures aquifer is much more prone to pollution than the lower exposed during mining operations. These contaminated confined aquifer. waters find their way into groundwaters, thereby pol- Fluid motion in saturated geological materials is de- luting them. Surface water and floods in the Pb-Zn min- pendent on the hydraulic gradient, porosity, and hy- eral belt of southeastern Nigeria contain high concen- draulic conductivity. Average groundwater velocity -v trations of Pb-Zn. These metal ions are also present in is obtained from the relation (38), shallow groundwaters in the area. The high Pb content K - Ki . dh of the shallow groundwater have posed some serious v = I = (1) health problems. Their implications and extent of haz- n ' dl ards are yet to be fully investigated. where i(dh/dl) is the hydraulic gradient, n is the porosity, K is the hydraulic conductivity, and dh/dl is the Structural Features and Sedimentary change in hydraulic head (h) with respect to the change Characteristics in distance (1). Porosity and hydraulic conductivity, in particular, are properties that are dependent on the The structural and sedimentary properties of rocks geologic conditions of the waste disposal site. Differ- that affect groundwater quality include layering, frac- ences in hydraulic conductivity values across a strati- tures, joints, faults, and shear zones (Figs. 2 and 3). graphic section could appreciably determine whether These structural features act as hosts for mineraliza- flow is upward, downward, or horizontal, as demon- tions and also serve as channel ways that conduct sur- strated by Freeze and Witherspoon (39). Thus, the ul- face waters to aquifers. Faults, shear zones, and joints timate fate of are often mineralized. The most common veins and fis- contaminants emanating from waste dis- sure-filling minerals are sulfides. Oxygen-laden surface posal sites can be strongly dependent on whether waters and carbonic acid waters entering these fissures groundwater flow is upward or downward. Therefore, oxidize and dissolve cations and anions from the sulfide the direction of flow of groundwater is an important minerals and introduce them into shallow groundwa- factor in the evaluation of sites for waste disposal. The ters. The toxic metallic elements introduced into the actual magnitude of groundwater velocity is also an im- groundwater by this method include As, Cs, Hg, Pb, portant factor. In low permeability geological materials, Ni, etc. Thus, in the surface or subsurface disposal of groundwater velocity can be as low as a few centimeters wastes, the structural, stratigraphic, and sedimento- per year. For such conditions, contaminants would be logical natures of the area must be mapped, described, transported over very short distances over a very long and known in order to produce a waste management time span and hence may not pose hazards to the en- design that would contain the wastes safely and keep vironment. these toxic elements from migrating into surrounding In contrast to the low velocity of groundwater that surface waters and groundwaters. occurs in low permeability materials such as shales, the velocity in permeable deposits or fractured media can be quite large. High groundwater velocity zones provide Hydrogeologic Settings a pathway through which water supply sources become Because contaminants are transported in large part quickly polluted. The search for and the evaluation of by the bulk motion of groundwater, the parameters of such high-velocity pathways is therefore an important groundwater flow are of major importance in the un- task in the groundwater pollution studies. The ease and 50 EGBOKA ET AL. extent to which contaminants can pollute an aquifer are Table 5. Representative ranges for various inorganic also dependent on whether the contaminants are intro- constituents in leachate from sanitary landfills (36). duced into the groundwater system at the recharge or Representative discharge areas. Figure 6 shows that a major portion Parameter concentration range, mg/L of an aquifer may become contaminated if the contam- K+ 200-1000 inant is introduced into the subsurface from an upland Na+ 200-1200 recharge site. Hence in designing or planning a waste Ca2+ 100-3000 disposal site, the entire hydrogeological properties of Mg2+ 100-1500 Cl- 300-3000 the area must be well established to ensure a safe and sO-2 10-1000 long-lasting disposal network. Alkalinity 500-10,000 Fe (total) 1-1000 Mn 0.01-100 Contaminant Pathways and Cu < 10 Processes in Groundwater Systems Ni 0.01-1 Zn 0.1-100 Pathways of entry of contaminants into groundwater Pb < 5 systems depend largely on patterns of waste disposal Hg < 0.2 and human interferences with the environment. An un- NO3 0.1-10 derstanding of the general methodologies of waste dis- NH4+ 10-1000 po4 1-100 posal is thus a prerequisite to any discussion of contam- Organic N 10-1000 inant pathways into the subsurface environment. The Total dissolved organic carbon 200-30,000 various waste disposal options currently in use include Chemical oxygen demand 1000-20,000 sanitary landfills, open dumps, septic tanks and cess- Total dissolved solids 5000-40,000 pools, and deep well injection systems. pH 4-8

Sanitary Landfills and Garbage Dumps PRECIPITATION Much of the solid waste that is now disposed of on land is placed in sanitary landfills. In humid areas, in particular, buried waste in sanitary landfills and dumps is subject to leaching by percolating rainwater. The Leachate Spring leaching process is accompanied by chemical reactions that tend to consume all available oxygen, while releasing carbon dioxide, methane, ammonium, bicarbonate, chloride, sulfate, and heavy metals. The liquid mix ofthese constituents is referred to as leachate. The total number and chemical concentrations of these constituents can be variable depending on the initial composition Groundwater Zone Contaminated by Leachate of the waste climatic conditions. Table 5 shows that leachates contain large numbers of inorganic contami- FIGURE 7. Water table mound beneath a landfill, causing migration nants and also have high total dissolved solids. Leach- of contaminants deeper into the groundwater zone (38). ates also contain many organic contaminants. Robertson et al. (40), for example, identified over 40 organic com- organisms before (the treated) sewage is released pounds in leachate samples (contaminated groundwater through a drainfield into the ground. A generalized dia- in a sandy aquifer in Oklahoma). Leachates emanating gram illustrating the layout of a septic tank waste-dis- from landfills contain contaminants and toxic constitu- posal system is shown in Figure 8. The figure demon- ents derived from solid wastes, as well as from liquid, strates that septic tank system effluents can quite easily industrial wastes placed in the landfill (41). reach and contaminate the groundwater system. Ac- Rain water percolation through refuse in the landfill cording to the United States Environmental Protection causes water table mounding, i.e., a rise in water table Agency (42), septic tanks and cesspools are the largest elevation within or below the landfill. The mounding contributors of wastewater to the ground and are the process, according to Freeze and Cherry (38) causes most frequently reported sources of groundwater con- leachate to flow downward and outward from the land- tamination in the United States. fill, as illustrated in Figure 7. Thus, for shallow aquifers, Apart from the effluent that is directly released into in particular, water table mounding provides a pathway the ground, there are large volumes of solid residual for the entry of contaminants into the groundwater sys- materials known as sewage sludge. In many parts of tem as a result of the buildup in hydraulic gradient and the world, this sludge, which contains a large number pressure head. of potential contaminants, is applied on agricultural lands to enhance crop nutrients such as nitrogen, phos- Septic Tanks and Cesspools phorous, and heavy metals that are needed for plant Septic tanks are designed to remove settleable solids, growth. Although this practice actually improves soil reduce biochemical oxygen demand, eliminate micro- fertility, it has been observed that one of the potential GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 51

_ PRODUCTION PRETREATMENT DISPOSAL structural stability, isolation from fractured bedrock, absence of subsurface flowlines that lead directly to the biosphere or to subsurface zones of potable water, low measured or predicted radionuclide velocities, and water table conditions that are deep enough to permit waste burial to remain entirely in the unsaturated zone.

DitibtonB x A ie/il Deep-Well Disposal Disposal of liquid wastes of industrial origin by in- i ~~~VdoseZone BDDgcI jection into the deep underground is a widely accepted EVAPOANSITRATION practice. The growing acceptance of this waste disposal option is mainly due to the numerous problems of pollution in near surface hydrologic environments (44). The growing acceptance of this option is suggested by the results of a survey conducted by Warner and Orcutt (45), which showed that waste injection wells increased from 30 in 1964 to at least 280 in 1973 in the United FIGURE 8. Contamination from a septic field (57). States. There are now more than 100,000 of these wells in North America. Although deep-well injection ofliquid negative impacts of this type of sewage disposal is deg- wastes is meant to minimize the problem of pollution in radation of groundwater quality (38). Contaminants in the near surface hydrologic environment as suggested the sewage sludge/effluent reach and contaminate by Piper (44), the potential for pollution of deep-seated groundwater through infiltrating water from rain or aquifers is still obvious. If the pollution of deep-lying aquifers is to be avoided, the disposal option requires snow. the isolation of formations receiving waste injections from permeable contact with other elements of the hy- Radioactive Waste Disposal drologic environment. Radioactive wastes are generated at various stages in the nuclear industry. Mining and milling of radioac- Human Activities and Pollution/ tive ores result in the production of large volumes of waste rock and tailings. Nuclear plant operation gen- Contamination erates radioactive fission products, reactor cooling Contaminants can be introduced into the groundwa- waters, irradiated fuel rods, and other by-products. ter system as a result of myriads of human activities. Figure 9 illustrates several types of waste burial al- This category of contamination of groundwater systems ternatives. In all cases, the wastes are stored in strong, differs from the ones described earlier in that such hu- engineered concrete containers. In the option illus- man activities do not ab initio introduce wastes into the trated by Figure 9a, the containers are placed on the subsurface. The major human activities that eventually surface of the ground and then covered with earth ma- end up polluting groundwater systems include agricul- terials. Figures 9b and 9c illustrate the options in which tural activities, storage of gasoline tanks in the sub- the containers are placed a few meters below the surface surface, pipe lines, road deicing, mining and pumpage of the ground either below or above the water table. of aquifers, etc. The difference between these two options is that in the Nitrate loading of shallow groundwater systems aris- latter (Fig. 9c) the fill in the excavation is designed to ing from fertilizer application occurs mainly through provide enhanced containment capability for the sys- leaching. Where there is significant downward flow, tem. A large number of burial options for radioactive deep-seated aquifers can become affected. According to wastes in Canada and the United States are in the cat- Freeze and Cherry (38), widespread nitrate contami- egory represented by Figure 9b (38). In Figures 9d and nation of aquifers through fertilizer application is rare. 9e, the containers are buried in large holes about 10 to Numerous investigators including Grisak (46) and Cus- 20 m deeper than in the previous examples. ter (47) have shown from case studies in various parts Because of the highly lethal nature of radioactive of the United States and Canada that nitrate derived wastes, particularly for those with long half-lives, it is by oxidation and leaching of natural organic nitrogen in necessary that these wastes are disposed of in systems the soil is more often responsible for extensive nitrate that have high containment capability. Failure of the contamination of shallow groundwaters. The pathway burial sites could result in the leakage of radioactive down to the water table of those contaminants gener- materials into the groundwater environment or into the ated through mining activities and road salt application biosphere. To avoid problems of subsurface radionuclide is similar to that for nitrates, i.e., they reach the water migration, numerous reported investigations including table through leaching and flushing through the unsat- Cherry et al. (43) have suggested that burial sites should urated zone by infiltration of percolating water from have the following characteristics: geomorphic and rain and snowmelt. 52 EGBOKA ET AL.

(a) - - Specially Designed Earth Material

...... _ *_ (c)

Zone of _ Water TableI Fluctuation M._ Backfill Protecttive Geolog)ic Materials

(e) FIGURE 9. Schematic diagrams illustrating methods of disposal of radioactive wastes (38).

Petroleum leakage from underground storage tanks the groundwater system are illustrated in Figure 10. A and oil pipe lines, as well as spills from oil-producing simple hydrogeologic condition is assumed. According wells, constitute an increasing threat to groundwater to Freeze and Cherry (38), in the initial migration stage quality (Fig. 10). Petroleum contaminant pathways into (seepage stage), the oil moves primarily in a downward

Leaky Storage Tank or Oil Spill /

* Vadose 2Zone @OilPhase* X **D > @

*Vapor Zone . . *.i ~ Capillary Fringe . _ Watertable

GROUND WATER FLOW DIRECTION . . . * . .; :. Dissolved Contaminants I

I Ik Hundreds of- Th4ousands of- Meters 14

FIGURE 10. Contamination from a leaky storage tank or oil spill (57). GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 53 direction under the influence of gravitational forces. On Pumping Well reaching the water table, the oil zone spreads laterally, first under the influence ofgravity-related gradients and subsequently in response to capillary forces. Capillary spreading becomes very slow, and eventually a rela- Original tively stable condition is attained. Figure 11 summa- Water Table-t., rizes the movement of mining wastes and pollutants Contaminated / .<..Pumping.. within the total environment. At each state and posi- Surface Water water Level tion, metal-rich mine materials may get into the air, surface water, soils, and groundwater to possibly pollute them. *: S.:.IQnduced Rec ag Figures 12a and 12b illustrate pathways by which contaminants in polluted surface waters and saline (a) water can enter groundwater zones. In Figure 12a, contaminated surface water reaches the groundwater zone Pumping Well as induced by water recharge under the influence of the gradients set up by the well. Instances of polluted surface waters are common, particularly in industrial areas where effluents are discharged untreated or partially treated into streams and lagoons. Figure 12b shows a Fresh-Water Aquifer '.. possible effect of overpumping that is often observed in coastal areas. Overpumping can cause contaminants from sea water to enter a freshwater aquifer.

Contaminant Transport: ''Saline-Water Aquier* Hydrogeochemical Processes The migration of contaminants in groundwater flow (b) systems is due mainly to groundwater motion. Trans- port rates, however, are moderated by a variety of geo- FIGURE 12. Contaminant pathways into an aquifer (a) through in- chemical and biochemical processes that include com- duced infiltration from contaminated surface water and (b) through plexation, acid-base reactions, oxidation-reduction over pumping near saline water aquifers (89). processes, precipitation-desorption reactions, and microbial reactions. According to Jackson and Inch (48), precipitation-dissolution, adsorption-desorption, and microbial reactions can lead to the removal of contaminants from solution, whereas the other processes affect the availability of the contaminant for adsorption or precipitation. Appropriate instrumentation, sampling, and monitoring would make these hydrogeochemical species veritable environmental tracers. Complex-Ion Formation Complex-ion formation is important in the study of groundwater pollution because the concentration and mobility of most contaminants are governed by the concentration and nature of the complexes they form. For example, hydroxide and carbonate complexes appreciably affect the mobility ofuranium and the heavy metals in groundwater flow systems. It has also been observed by Jackson and Inch (48) that when heavy metals (e.g., Pb2+, Cd2+) are complexed by inorganic or organic ligands (e.g., Cl-, EDTA), the contaminants may not be immediately available for adsorption or precipitation, and consequently the mobility of heavy metal contaminants may be increased in the groundwater flow sys- FIGURE 11. Movements of mining pollutants within the total envi- tem. On the other hand, contaminants may become as- ronment. Modified from Press and Siever (32). sociated with adsorbed complexing ligands such as 54 EGBOKA ET AL. humic acids. In that case, their mobility will be reduced. high dissolved oxygen content. Along the flow system, It is thus concluded that adsorbing and nonadsorbing the tendency is toward oxygen depletion. The first stage ligands may compete for contaminant ions and thus de- in the oxygen depletion process is the oxidation of or- termine, on the basis of the relevant formation con- ganic matter (CH20): stants, the distribution of complexed contaminants between adsorbed and solution states. 02+ CH20 = C02 + H20 (7) Reaction 7 is catalyzed by bacteria or isolated enzymes. Acid-Base Reactions They derive energy by facilitating the process of elec- Acid-base reactions are those chemical reactions in- tron transfer. Organic matter oxidation of the type il- volving the transfer of protons. Proton activity, H+, lustrated in Eq. (7) is a major redox reaction occurring expressed as -log H+, is referred to as pH. The nu- in landfills and other similar waste disposal sites. Thus, merical value of pH gives an indication of the acidity of leachates emanating from landfills have much lower re- natural waters. The pH of natural waters is controlled dox potential. The leachates also have elevated concen- by calcite (CaCO3) dissolution and the CO2 in the soil trations of NH, H2S, Fe2+, Mn2+, and FeS. zone according to the following equations: As the leachate enters the groundwater system, the following sequence of redox processes would occur (38): CO2 + H20 = H2C03 (2) (i) Oxidation of Sulfide to Sulfate, H2C03 + CaCO3 = Ca+2 + 2HC03 (3) -2 (8) According to Stumm and Morgan (49), CaCO3 is an 202+HS-=S04 +H+ efficient pH buffer only in the neutral and acid pH range. (ii) Oxidation of Ferrous Iron, In the pH range of 9 and above, the incongruent dissolution of aluminosilicate minerals provides a greater 02 + 4Fe+2 + 4H+ = 4Fe+3 + 2H20 (9) buffer capacity. In pollution studies, it is important to know the pH of the groundwater and its buffering and the precipitation of Fe+3 as Fe(OH)3 agents since the solubility of many minerals as potential contaminant sources and sinks are dependent on pH. (iii) Nitrification Acid-base reactions become prominent in environmental (10) pollution and degradation where situations create ex- 202 + NH4 = N03 + 2H+ + H20 tremes of acidity or alkalinity. Thus, in acid mine drainage areas, acid rain, alkalinity, or alkaline rain situa- (iv) Manganese Oxidation tions, the hydrogeological processes such as oxidation- (11) reduction, cation exchange, adsorption-desorption, etc., 02 + 2Mn+2 + 2H20 = 2MnO2 + 4H+ may result in the ultimate release of pollutant and contaminants into these systems to damage them. When all the dissolved oxygen in the groundwater is consumed, oxidation of organic matter can still occur as Oxidation-Reduction Processes indicated in the following reaction equations (38): Oxidation-reduction (or redox) processes are of a ma- (i) Denitrification jor importance in governing the geochemical behavior (12) of those elements that may gain or lose electrons in 5CH20 + 4N03 = 2N2 + 5HC03 + H+ + 2H20 groundwaters. By definition, oxidation is the loss of electrons and reduction is the gain in electrons, as (ii) Manganese (iv) Reduction shown in the following illustrated examples for the oxidation of iron: (13)- - I CH20 + 2MnO2 + 4H+ = 2Mn+2 + 3H20 + CO2 + 4H+ + 4e- = 2H20 (reduction) (4) 02 (iii) Iron (iii) Reduction 4Fe+2 = 4Fe+3 + 4e- (oxidation) (5) (14) CH20 + 4Fe(OH)3 + 8H+ = 4Fe+2 + 11H20 + C02 In reality, a reduction reaction is coupled to the cor- responding oxidation reaction, so that the overall redox reaction for the oxidation of iron, for example, is of the (iv) Sulfate Reduction (15) form: -2 2CH20 + S04 = HS- + 2CH03 + H+ 02 + 4Fe+2 + 4H+ = 4Fe+3 + 2H20 (6) The redox state of groundwater is described by the (v) Methane Fermentation redox potential pE (or Eh). Water infiltrating into shal- (16) low groundwaters has high redox potential due to its 2CH20 + H20 = 'I4 + H+ + HCO3 GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 55

It is clear from these reaction sequences that ade- by the number of milliequivalents of that ion per mil- quate knowledge of the redox environment is needed liliter remaining in solution at equilibrium" (48). The for the purpose of predicting the mobility of those ele- magnitude of the distribution coefficient is a measure ments that have variable valences and which form low of the extent of partitioning of a contaminant species water-solubility oxides. For example, oxidized forms of between the solid and liquid phases along a groundwater iron [Fe(OH)3] and manganese (MnO2) are highly in- flow system. soluble; the reduced forms (Fe2+; Mn2"), however, are soluble in water and thus move with the groundwater. Uranium, selenium, arsenic, and molybdenum are in- Microbial Reactions soluble under reducing conditions and soluble under ox- Most of the geochemical reactions leading to the idizing conditions. Thus, depending on the physical, breakdown and transformation of complex molecules in chemical, and biological conditions within the hydro- groundwater systems are microbially mediated. These geochemical environment, contaminants may exist in microorganisms derive energy and constituents needed polluted groundwater systems in various concentrations for survival from these reactions. For bacteria to func- and forms. Detailed instrumentation and closely spaced tion and proliferate, it is also important for suitable monitoring programs easily delineate the geochemical temperatures and pH conditions to prevail in the me- zones (4,7,33,41). dium (48). In the investigations carried out by Jackson and Inch (48), it was also observed that bacterially mediated chemical processes may have either beneficial or Precipitation-Dissolution Reactions detrimental effects on particular pollutants. The bene- Precipitation-dissolution reactions are a set of reac- ficial effects include purification of contaminated water tions by which contaminants may be removed from so- as organic pollutants are broken down into substances lution either by direct precipitation or by isomorphous such as CO2, H20, NO , and SO2P-. Elements such as substitution with an ion of similar atomic radius in a N, S, C, and P are used in the synthesis of microbial crystal that is forming or that has formed (48). The protoplasm and are thereby removed from the ground- formation of metal carbonates, e.g., Sr(C03)2, water system. Among the detrimental effects is the Cd(CO3)2, provide good examples ofremoval of contam- depletion of dissolved oxygen. inants from solution in groundwater by precipitation Two phases are involved in the infiltration of unpol- reactions. Saturation index calculations may be em- luted groundwaters by polluted surface waters. These ployed to determine whether a mineral species is likely are associated with the oxygen-rich unsaturated zone to dissolve or precipitate in a groundwater flow system and the oxygen-deficient zone which is usually satu- (38). rated. Organic pollutants are usually removed by fl- tration in the unsaturated zone where an effective biological filter can be formed. By these processes some Adsorption-Desorption Reactions soils constitute an efficient filter for water treatment. Adsorption occurs when a dissolved ion becomes at- Most microorganisms are not adapted to this tortuous tached to the surface of a preexisting solid substrate and highly competitive environment, which limits their (50). In porous media, contaminants can become ad- movement to no more than 3 m in depth (51). For this sorbed onto colloidal-size particles. The adsorption ca- reason, any well or borehole not properly lined for its pacity of colloids is thought to be due to their ability to entire length stands a chance of being polluted by mi- generate a charged solid-solution interface. The pres- croorganisms from surface waters. ence of a solid surface charge arises from imperfections Adsorption is the main mechanism by which micro- or ionic substitutions within the crystal lattice of the organisms are removed from the oxygen-depleted sat- colloids. The charge imbalance arising from the accu- urated zone. Under this condition, microorganisms may mulation of charge on the colloid surface, however, is be carried passively in groundwaters up to a distance compensated for by a surface accumulation of ions of of 30 m horizontally (51). In view of this, a minimum opposite charge known as counterions. Ion exchange protection zone of 30 m is essential in siting boreholes occurs when the ions in the counterion layer become and wells if contamination from polluted surface water exchanged for other ions. Cation exchange capacity has from septic tanks, agricultural wastes, and refuse tips been defined by Jackson and Inch (48) as the excess of is to be avoided. Fissured rock strata constitute an ad- counterions which can be exchanged for other cations ditional problem. Where they exist, the extent of pas- in the bulk of the solution. It is usually expressed as sive travel by microorganisms is unlimited, as natural the number of milliequivalents of cations that can be purification through soil is almost nonexistent (52). exchanged in a sample with a dry mass of 100 g. Cation During hydrogeomicrobiological processes, the activ- exchange reactions are important in the predictive ities of nonpathogenic bacteria in groundwaters could analysis of the mobility of contaminants in geological be beneficial because they are involved in the degra- media. A measure of the mobility of contaminants that dation of detergents, herbicides, pesticides, and general is used in predictive analysis is the distribution coeffi- mineralization, including cycling of essential elements, cient (Kd). It is defined as "the number of milliequiva- nitrogen, phosphorus, and sulfur. When pollution is in lents of an ion adsorbed per gram of exchanger divided excess, these beneficial processes could lead to problems 56 EGBOKA ET AL. for groundwaters, such as depletion of dissolved oxy- C(x,O) = 0; x > O (19) gen, reduction of nitrate to nitrite or ammonia, reduction of sulfate to sulfide with attendant offensive odors C(O,t) = co; t > 0 (20) and growth of filamentous bacteria, reaction of sulfide with iron to form an insoluble precipitate that can re- C(oo,t) = 0; t > 0 strict groundwater flow, and mobilization of iron from (21) soil under conditions of reduced oxygen tension only to the solution to Eq. (18) for a saturated homogeneous be oxidized and precipitated in other regions ofthe aqui- porous medium is given by Ogata (53) as fer either by chemical or microbiological means (24). Under anoxic conditions, gram-negative chemolitho- Co = 0.5 )f trophic bacteria utilize nitrates, sulfates, and iron/man- CIO 42 ganese oxides as terminal hydrogen acceptors in res- (22) piration and other physiological processes. + exp (Dx) erfc tJ] Contaminant Transport: Physical Processes where erfc represents the complementary error func- tion and all other terms are as previously defined. An accurate description of the spatial and temporal Figure 13 illustrates the concentration profiles ob- distribution of contaminants in groundwater systems is tained with Eq. (22) and what is normally referred to of major importance in groundwater pollution studies. as a breakthrough curve for contaminants migrating The model widely applied in the evaluation of contam- through a porous medium. The figure demonstrates the inant migration is based on the advection-dispersion effect of mechanical dispersion and molecular diffusion, equation. It is derived from considerations of mass flux namely that of causing some of the contaminants to into and out of a fixed elemental volume within the flow move faster and others to move slower than the average domain. The physical processes that control these fluxes linear groundwater velocity. This causes a spreading are advection (i.e., contaminant transport due to bulk out of the concentration proffle along the direction of movement of groundwater) and hydrodynamic disper- flow and to some extent in directions transverse to it. sion that accounts for the mechanical mixing and mo- In the absence of dispersion and diffusion, the contam- lecular diffusion within the flow system. Loss or gain inant front will move as plug flow, and its position along of contaminant mass in the elemental volume results a flow system will be entirely determined by the average from chemical or biochemical reactions, radioactive de- linear groundwater velocity. cay, or combinations of these. The exact form of the In the case of reactive contaminants, a sorption term advection-dispersion equation depends on whether the is added to Eq. (22) to account for the transfer to or contaminants under consideration are nonreactive or from the solids in the elemental volume. The advection- reactive. dispersion equation then takes the form (38): For nonreactive constituents, the one-dimensional form of the advection-dispersion equation in saturated, ac Pbas a2c ac homogeneous, isotropic materials under steady-state at n+a-t =D2 a x (23) uniform flow is (38): ac a2C aC (17) where Pb is the bulk density of the porous medium, n a t ax ax is the porosity, and s is the mass of the chemical con- stituent adsorbed on the solid part ofthe porous medium where x is a curvilinear coordinate direction taken along per unit mass ofsolids; as/at represents the rate at which the flowline, v is the average linear groundwater velocity, D, is the coefficient of hydrodynamic dispersion along the x direction, C is the contaminant concentra- Contaminant Front Position of tion, and t is time. The coefficient of hydrodynamic dis- if Diffusion Only Groundwater persion is of the form: a 1 Dx= axl vl+DD (18) where txx is the dispersivity, a characteristic property o 05. of the porous medium, and D* is the coefficient of mo- 0 lecular diffusion. The term axjIVI expresses the mechanical mixing component of the dispersion process, U 0A which is the result of velocity variations within the po- Distance X rous medium. The advection-dispersion equation is solved under FIGURE 13. Schematic diagram showing the contribution of molec- prescribed boundary conditions. For the following ular diffusion and mechanical dispersion in causing spreading dur- boundary conditions: ing contaminant migration (38). GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 57 the contaminant is adsorbed, and the term (pbjn) (as/at) Field Application of Advection-Dispersion represents the changes in concentration in the fluid phase caused by adsorption or desorption. If biochem- Equation ical processes are ignored, the sorption term then de- An example of the application of the advection-dis- pends only on ion exchange, precipitation and coprecip- persion equation in the solution of problems in contam- itation. inant migration is provided by a field study carried out When a contaminant is adsorbed by a solid, it mi- by Egboka et al. (41). In the study, an analytical solution grates at a rate slower than if there was no adsorption. to the one-dimensional form of the advection-dispersion Assuming a fast and reversible adsorption-desorption equation was used to simulate the distribution oftritium (cation-exchange) process, and if the concentration of (a nonreactive species) produced during atmospheric the adsorbed contaminant is small compared with the testing and use of nuclear weapons along a contaminant total concentration of cations in solution, the rate of plume under a landfill site in Borden, Ontario, Canada. advance of the contaminant front is given by (50): Field values ofradioactive bomb tritium were correctly simulated by using longitudinal dispersivity values of v v between 30 and 60 m and groundwater velocity values PbKd (24) of about 10 m/year (Fig. 15). These aquifer parameters n were used to predict the movement, spread, and dis- where Vc is the velocity of the adsorbed contaminant persion of contaminants in the polluted groundwater and Kd is the distribution coefficient. The terms in the such as sulfate (Fig. 16), chloride, etc. While Egboka denominator are referred to as the retardation factor, et al. (41) investigated dispersion of contaminants in- which can be used to estimate how rapidly a contami- troduced into the hydrogeologic system under natural nant would migrate through the flow system. The effect conditions, Sudicky et al. (54) introduced artificial of retardation on contaminant migration is schemati- tracers into the same area and arrived at similar results cally shown in Figure 14. The contaminant front in the usable for the planning and management oflandfills and case of the adsorbed species, A', moves at a much garbage dumps. slower rate than that of the nonadsorbed species, B+. An important implication of this condition is that com- 28011 pared with a nonadsorbed species, it will take a much Velocity=12.5m yr-' _ 24 longer time for the adsorbed contaminant species to 00 <><\ | ~~~~~19533H Plug Flow Front reach and pollute a groundwater supply source, and 20 hence is less of a threat or hazard to the environment. gj 16 30 - (. 12 E a Time t1 i 440 Detection Limit 0 UCs 040 80120160200240280320 36400440480520560004 0

1- Distance X E. (a) E

Time t2 >tl S t

E 0 A \ Distance X (b) Distance Along Pollutant Plume Path (Meters)

FIGURE 14. Schematic diagram showing the effect of retardation. The migration of an adsorbed species (A+); the position of non- FIGURE 15. Simulated bomb 3H versus distance in a landfill aquifer adsorbed species (B + ) (50). using varied velocities and longitudinal dispersivities (41). 58 EGBOKA ET AL.

Pollution Situation in Developed The ever-increasing use of organic pesticides and herbicides has constituted another source of groundwater and Developing Countries contamination. Various investigators in the southwest- As a result of the ever-increasing industrial estab- ern United States have observed that pollution by pes- lishments and man's general activities, physical, chem- ticides must be listed as an important potential hazard. ical, and biological substances are being fed into the Croll (56) arrived at a similar conclusion on the basis of groundwater environment on a daily basis. This section a literature review and field studies in Kent, England. summarizes the pollution situation in both developed In Canada, numerous cases of groundwater pollution and developing countries. Emphasis is focused on the have been reported. A comprehensive coverage ofthese developing countries. cases has been presented by Cherry (57). Shallow groundwaters that have been contaminated by leach- Developed Countries ates from landfills include those that occur below three large landfills in the outskirts of the city of North Bay Groundwater literature is filled with incidences of and near Alliston and Kitchenor-Waterloo in Ontario. groundwater pollution in many parts of the developed Severe groundwater contamination from chlorophenols countries including the United States, Canada, USSR, has been reported from Pentritton, British Columbia and various parts of Europe. Table 6 presents a sum- (57). Mine tailings are another major source of ground- mary of groundwater contamination incidents in parts water contamination in the mining districts of Canada. of the United States as reported by Lindorff (55). The Extensive nitrate contamination of shallow aquifers number and percentage of incidents affecting or threat- have been observed in the Canadian prairies. This has ening groundwater supplies is shown in the second col- been attributed to the use of agricultural fertilizers. umn. The third column shows the number and per- Similar widespread occurrence of nitrate has been re- centage of the cases that threatened or produced fires ported in a large regional carbonate-rock aquifer in Eng- or explosions. land and the United States. Leakages in nuclear power plants constitute another Table 6. Summary of groundwater contamination incidents (46). source of groundwater contamination. This is because No. of Water Fire or the radiation would eventually be returned to the Contaminant incidents supplies, % explosion, % groundwater environment. Recent nuclear leakages in- Industrial wastes 50 31 (62) 2 (4) clude the Chernobyl incident in the Soviet Union. The Landfill leachate 46 7 (15) 0 impact of these leakages on the groundwater environ- Petroleum products 27 18 (57) 10 (37) ment has, however, not been fully investigated. No Organic wastes 21 15 (71) 0 doubt, a large number of cases of groundwater contam- Chlorides 16 13 (81) 0 disposal sites Radioactive wastes 7 2 (29) 0 ination have been reported. However, Pesticides 4 2 (50) 0 that are known contamination sources probably account Fertilizer 3 3 (100) 0 for only a small fraction of the total number of sites Mine drainage 3 1 (33) 0 where groundwater contamination now occurs (57). It 173 92 (53) 12 (7) should, in addition, be expected that more severe cases

-I Ica IC..

Unpolluted Groundwater Tritiated and Non-Tritiated (Low Sulfate) Groundwater Boundary -250- Conc. SO4-2 (mgl-') 100 50 0 lOOm Vert. Exag = 10

FIGURE 16. Sulfate pollution of ground with tritiated tritium boundary (41). GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 59 ofpollution could arise in the future as technology brings The specter of widescale pollution of environments of new and more hazardous chemical compounds into pro- developing countries is becoming more threatening for duction and use. At the moment, great amounts of fi- many other reasons. More and more urban, suburban, nancial and material resources have been spent on the and rural communities are being polluted or exposed to control of pollution. Health and environmental hazards pollution. Few of these countries have plans or man- posed by pollutants and contaminants are immense as agement programs to combat pollution. Pollution prob- many pollution-related diseases continue to emerge. lems are thus tolerated and given no priority. There is Great losses in human and animal life and property have little or no public or government awareness because the continued. As the developed countries are engrossed in dangers seem to be ignored or overlooked. There are these problems, it is unfortunate that the developing no Environmental Protection Laws and where avail- countries are becoming equally affected because no ar- able, they are rarely enforced. When these poor coun- ticulated control programs exist to any extent. tries soon reach the level of pollutant/contaminant generation as the rich industrialized countries, they shall be much worse off. Already various health hazards and Developing Countries polluted waters with waterborne diseases and epidem- Information on environmental pollution situations of ics ravage these countries from time to time. Even developed countries such as the United States, Canada, though it is known that many of these pollutants are and parts of Europe abound in the hydrogeologic lit- produced through industrialization and urbanization ac- erature (20,58-65). Acid rain has obliterated many an- tivities, governments, groups, and individuals have not cient forests, acidified both surface water and shallow been doing anything to control their emission or pro- groundwaters, and defaced many buildings and monu- duction. Even in rural environments where agricul- ments. Industrial wastes dumped as solids or dis- tural, mining, and urbanizing programs continue to gen- charged as liquids into surface waters have destroyed erate pollutants and contaminants, no one seems to the fauna and flora of these waters. Many landfills and show much concern. sewage lagoons dotted all over these industrialized na- Some developed countries, as a result of their stiff tions have damaged the hydrogeologic environments. Environmental Protection Laws, indirectly encourage Many medium-level and high-level wastes from nuclear the export of waste products. This practice is either industries are stockpiled, waiting for safe disposal sites carried out directly because these materials cannot be yet to be located in any part of the world. These pol- disposed of economically or safely in their home coun- lutant/contaminant materials and their attendant prob- tries or indirectly through establishment of industries lems have devoured huge funds for research and control in developing countries. These industries produce haz- activities. -Despite the available manpower and exper- ardous wastes that are carelessly dumped or dis- tise and the adequate financial resources in these coun- charged. Such exported industries lack adequate safety tries, minimal successes in combating pollution have devices and efficient monitoring systems. Finally, in the been achieved, so pollution threats so far seem to have drinking water supply program, emphasis is placed only defied man's efforts. on water quantity and little or none on quality. Because The fate of developed countries magnifies the help- of this emphasis water potability is questionable most lessness of some developing countries that have now of the time. Typical pollution case examples from some exposed parts of their hydrogeologic environments to developing countries shall be given below to provide pollution. Many of these countries in their race to be- more credence to these unfortunate observations. come industrialized have accumulated waste products that now pollute the environment. Many of these countries have copied the developed countries in their sci- Environmental/Health Hazards and ence and technology, packaged and acquired the re- Implications sulting technological outputs, and transplanted them into their countries without the necessary checks and Various environmental problems can arise as a result balances such as an appropriate adaptation to the needs of groundwater pollution. A major consequence of of their environments. These countries produce huge groundwater pollution includes the potential contami- volumes of pollutants and contaminants from industries nation of surface waters. This can happen if the rivers, and urban centers and dispose of them into surface streams, or lakes in the area are recharged by a polluted waters or dump them at the outskirts of their cities. aquifer. The converse becomes the case if contaminated They do not have enough pollution management experts surface waters recharge an aquifer. These cases are and the necessary finances to control the spread of pol- illustrated in Figures 17a and 17b, respectively. Water lutants. Outbreaks of diseases that are pollution based pollution can result in a reduction in economic and ag- occur from time to time. It is strongly believed that ricultural activities. For example, when surface waters unless these developing countries do something to stop are contaminated, they can result in higher fish mor- the present pollution trends that are fast growing, many tality. In third world countries, in particular, where of their environments shall be worse off than those now fishing on a subsistence level provides a means of live- prevalent in parts ofthe developed world. Already some lihood, a significant drop in fish productivity due to pol- countries are closely approaching this stage. lution can have unpleasant consequences on the eco- 60 EGBOKA ET AL.

with long half-lives. Because of this property, they remain hazardous for long times within the hydrogeologic environment and are very difficult to remove. In the hydrogeomicrobiologic literature, cases of microbial pollution and hazards abound that are a threat Water Table to both surface water and groundwater systems. Under Aquifer certain circumstances, the pathogenic microorganisms listed in Table 3 escape the purification processes ac- Confining Layer companying percolation of polluted surface waters into groundwaters where they constitute a dangerous health hazard. Salmonellosis, bacillary dysentery, schistoso- miasis, helminthiasis, and viral infections are known to have been transmitted through drinking groundwaters polluted by surface waters and sewage in this way (66). Public interest in nitrogen oxides arises from the toxic effects of nitrite when nitrite ions enter the blood stream and react with hemoglobin, leading to an im- pairment of oxygen transport, particularly in infants. The disease is almost always attributable to high levels of nitrates in drinking water supplies including polluted groundwaters (23,31,35). Under certain conditions nitrate may be reduced to ammonia by some ofthe nitrate reducers. The ammonia can react with chlorine to produce chloramines, which can lead to undesirable tastes and odors. The presence of sulfides produced by sulfates FIGURE 17. A schematic diagram showing the potential for contam- reducers in groundwaters also impart unacceptable ination of (a) surface waters when an aquifer is polluted and (b) tastes and odors. Iron bacteria have caused problems contamination of groundwaters when surface waters are polluted. in water supplies since the dawn of civilization, and there are many references in history to "red" water, undrinkable water covered with slime, and plugged nomic life of the community. Polluted irrigation water wells (67). poses health risks. It can also result in reduced crop In wells and boreholes, the major problems are a) productivity. Thus, water pollution can have serious growths that plug the screens; b) coatings on piping negative effects on the agricultural sector too. systems, impellers and motors, that reduce flow rates; Other environmental hazards arising from water pol- c) reduced potability of water; and d) total plugging of lution include the presence of odor and color in the af- the well. The iron and manganese bacteria that cause fected water. Pollution of surface waters (lakes, dams, these problems are thought to be introduced into the rivers) may affect groundwater adversely. Water sup- wells and boreholes from their soil habitat during initial plies are contaminated resulting in health risks and in- boring operations or by seepage into the aquifer feeding creased load on water treatment plants; increased costs the well (68). on water treatment plants; fish kills or decline in pro- Groundwaters drawn from wells and boreholes conductivity, quality and quantity; polluted irrigation stitute a major source of water supply in many African water, posing health risks or inhibiting crop productiv- countries including Nigeria. In these circumstances, the ity; degradation of recreational and aesthetic charac- water is usually untreated. The inadequate practices of teristics of waters; etc. (1). Sometimes poisonous ions, waste disposal in these countries lend themselves as dissolved gases, trace elements, heavy metals, and ra- being a large source of pollution for groundwaters. dioactive materials in water endanger the biospheric In Nigeria, feces are disposed of by one or more of parts of the environments. Hence waterborne diseases the following ways, depending on the locality: disposal are ofepidemic occurrence in many developing countries on ordinary dry ground, bucket latrines, the pit-latrine where they form debilitating scourges to humans. Also or pit-privy, and septic tank latrine (aqua privy). Do- major physiological ailments such as cancer, that may mestic and industrial wastes are disposed of either by sometimes be caused by water or food have become composting, sewage, or open drainage systems (66). The rampant in both developed and developing countries. content of these waste products are usually organic and Many surface water and groundwater bodies are dead inorganic matter as well as microorganisms, some of and remain anoxic as a result of heavy inputs of pollu- which are pathogenic. Some of the wastes in refuse tips tants and contaminants. Many pollutants from one are washed into surface waters leading to eutrophica- source can move for long distances through ground- tion. In most circumstances in Nigeria, parts of Lagos, water flow systems to polluted faraway areas, precip- Ibadan, Benin, Enugu, Onitsha, Kaduna, Kano, Jos, itating large-scale environmental destruction. Some Abakaliki, etc., adequate hydrological data are not high-level wastes have pollutants and contaminants sought on soil strata and the direction and rate of flow GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 61 of groundwaters before wells are sunk (37). The result logic units, no safe disposal environments have yet been is that sometimes wells are sunk less than 5 m away found for waste products that have long half-lives. It from obvious sources ofpollution like pit latrines (69,70). seems that until a safe and more reliable disposal Worse still, the wells are usually not lined at all, with method is found, both the developed and developing the result that the groundwaters easily get contami- countries, have no option but to reduce the volume of nated by seepage from pollute surface waters. wastes both societies are now generating and abandon- Cases of guinea worm infestation in parts of Ilorin ing or storing within hydrogeologic environments. and Abakaliki have continually been linked to the drinking of groundwaters contaminated by heavily polluted surface waters. The outbreak of cholera in Ohaozara Pollution Case Examples from area of Nigeria in 1981-1984 was also linked to poorly Some Developing Countries sited wells in the area (25). It is obvious that, if sys- Parts of urban and rural environments of many de- tematically investigated, most outbreaks of waterborne veloping countries such as India, Kenya, Nigeria, Su- diseases could be linked to pollution of groundwaters dan, Egypt, Iraq, and Brazil are being polluted with a from surface waters, septic tanks, pit latrines, and com- wide variety of hazardous substances. Such countries post heaps. It is in recognition of this danger that the are struggling to become industrialized without ade- Federal and State governments of Nigeria as well as quate plans to contain the spread and hazards of pol- many international organizations like the WHO and lution. There are many sources of pollution in devel- UNICEF are currently tackling health problems in Ni- oping countries. Some of those related to mining, geria by the provision of properly sited boreholes in all mineralization, agricultural, domestic, municipal, hu- the rural communities. man, and animal wastes shall be discussed. Typical case In 1977 the Food and Drug Administration Unit of examples shall also be briefly described, and these shall the Federal Ministry of Health in Kaduna Nigeria (25) be generally related and at some instances specific to reported a widespread occurrence of iron bacteria in up some developing countries that are now industrializing to 60% of the boreholes in the Funtua, Bida, Malum- at a rapid rate. fashi, Dutsi-ma, Daura, Katsina, and Kano areas (23). Except in the Kano areas, the genera of iron bacteria encountered were Siderocapse and Siderococcus. These Mining Pollution microbial pollutants have caused many groundwater Contamination of groundwater due to mining activity supplies problems, resulting in loss ofwell yields, water is a major problem in many developing countries. Pre- contamination, and increased costs of water supplies. vious or present mining activities result in contamina- These problems are worsened by the absence of contin- tion from waste dumps, mine workings, fragments, and uous monitoring programs. dust from ore and rock piles and smelter operations. In the Kano area, the filamentous iron bacteria Lep- Sulfides (usually pyrite, galena, and sphalerite) in mine tothrix and Crenothrix were found abundantly in nearly dumps are especially susceptible to oxidation and pro- all the boreholes in the Bompai area, on the outskirts duce acid mine waters that can be leached out in varying of Kano municipality. The pollution was traced to the volumes and amounts. The ore minerals are not com- myriad of refuse tips made up of the waste products pletely recovered during the beneficiation processes. from the sugar, sweets, and biscuit factories in Kano. The acid mine waters that also contain trace metals The global distribution of iron bacterial problems in make their way into groundwater flow systems. groundwater was reported by Cullimore and McCann Acid mine waters from an abandoned mine in the (67). Among the developing countries included in the Charcas District, San Luis Potosi, resulted in high metal draft are El Salvador, Guyana, India, Malaya, Nigeria, values in drainage systems and groundwaters (71). The Singapore, and Sri Lanka. Crenothrix was found to be acid mine drainage problems in Enugu coal mines of plugging water supply systems in Sri Lanka; Clonothrix Nigeria and their effects on groundwater pollution were reduced flow rates and potability of water in the Cal- highlighted by Egboka and Uma (21). Many coal beds cutta area of India. In all others, the offensive iron may contain up to 10% sulfur, chiefly in the form of bacteria were not specified, but the damage they caused pyrite and marcasite. As the coal deposit is worked, air was observed. and water gain access to the seams that contain sulfur The industrialized world has accumulated great minerals, oxidizing the sulfide minerals. This results in amounts of pollutants and contaminants within their the formation of enormous amounts of sulfuric acid. environments. Many of these pollutants have spread Groundwater recharged by water from the mine needs widely and in such a complex manner that their control considerable treatment with lime before it can be used will be a most difficult and costly venture. Many wastes to supply domestic homes and industries. In the acid are now piled up in storage tanks above and below the mine drainage problems in the Enugu coal mines of ground surface, while painstaking research efforts are Nigeria, about 18.1 million liters ofacid water with high being made to scout out possible safe geologic environ- iron content is pumped out daily into nearby rivers. ments for their disposal. Unfortunately, so far, as a Some of this acid water eventually enters groundwater result ofthe structural, stratigraphic, sedimentological, flow systems. The acid waters also attack and corrode and geotechnical properties of the pedologic and geo- mining equipment causing great financial losses. Some 62 EGBOKA ET AL. mine waters are colored brown by tannins from bark of undesirable compounds into groundwaters (18,69, trees. They have an objectionable taste and they render 70,72). the water unfit for drinking. Sometimes the waters ac- In many cities all kinds of waste materials are strewn tually are sterile enough for use even though they are about on the outskirts of towns or are thrown into colored and may have a bad taste. Phenols are abundant streams, lakes, and rivers as most of those cities origin waters in coal swamps. Phenols are poisonous to inated and developed close to major rivers. Aerosol many bacteria and are capable of making mine waters cans, drug containers, hospitals, and research labora- sterile if they are present in large quantities. tories, washings or wastewaters that may contain heavy In most developing countries there is no legislation metals such as mercury, lead, zinc, etc., may eventually guiding the safe disposal ofmine wastes and mine dumps decay or spread and become transported into ground- or their proper management. Most of the mining com- water flow domains. Underground and surface storage panies involved are mostly foreign firms. The companies tanks, septic systems/fields, etc., washings from motor do not show much interest in tackling environmental mechanic sheds and garages produce contaminating pollution problems associated with the mining wastes leachates (Fig. 7). These types ofpollutants have threat- they produce annually. Little or no money is spent on ened hydrogeologic systems in parts of Nigeria wastes research and management in many parts of Ni- (69,70,72). In some urban areas of developing countries geria and other countries. The uneducated rural people such as India in temperate climates, large quantities of often use polluted waters discharged from mines. Many road salt (NaCl and CaCI) are used for deicing the road people from Abakaliki Mining district of Anambra in winter. Leachates from these activities will eventu- State, Nigeria, suffer from lead poisoning resulting ally contaminate aquifers. Egboka (15) briefly described from the contamination of their water sources by lead. the traditional habit ofusing the bush for toilet purposes The area is also ravaged by guinea worm and other in many rural areas and suburban centers. It is believed waterborne diseases. that defecation of this type contributes to widespread and prevalent waterborne diseases in such areas. It also accelerates large-scale incidences of eutrophication in Domestic, Municipal, Human, and Animal lakes. Unfortunately, it is yet to be estimated the de- Waste Contamination gree and extent of environmental pollution through def- Domestic wastes contribute a large number of ele- ecation in the rural areas. ments to groundwater systems, all with unpleasant ramifications. The most common contaminants from Agricultural Contamination household products include phosphates and boron in laundry detergents, copper and other elements as or- The use of pesticides, herbicides, fertilizers, and ganometallic compounds in garbage; metals in urine and other materials to increase agricultural yields has some excreta; copper, lead, zinc, and asbestos from pipes; great negative effects on groundwater quality. Pesti- nickel from stainless-steel and well Mu- cides and herbicides applied to fields or orchards may pipes casings. find their way into groundwater when rain or irrigation nicipalities that treat sewage and garbage reduce metal water leaches the dissolved constituents downward into concentration in drinking waters, but the recent ten- the soil. Nitrate from its fertilizer, one of the most dency to dispose of the treated material on land even- widely used agricultural fertilizers, is harmful in drink- tually yields metals to the drainage basin. Such metals ing waters even in relatively small quantities. The ni- may eventually reach the surface water and ground- trate is very soluble and although some may be used by water flow systems and pollute them. Similarly, metals plants, much of the dissolved nitrate escapes unused are introduced into the hydrogeologic environment from into deeper parts ofthe soil and into groundwater. Sew- the resultant ashes when garbage or solid wastes are age and fertilizer can increase nitrate levels in some composted as is commonly done in developing countries. aquifers (4). Nitrate is toxic to humans even in amounts The tremendous increase in the use of septic tanks as small as 10 to 15 ppm. for home sewage disposal has contributed a great deal Uranium and fluorine in phosphate fertilizers and ofdissolved polluting materials to groundwater (Fig. 8). probably rubidium in potash fertilizer are soluble under The septic tank waters seep into the soil and where most conditions and will eventually find their way into water supply aquifers are shallow, will contaminate the groundwater regimes. The use of lime for the pro- groundwater with phosphate and boron from detergents duction of fertilizer may result in lead and zinc contam- and a variety of other substances such as nitrates that ination, if the lime is produced from metal-containing are undesirable or harmful to health. In many rural limestones. Mississippi-type lead-zinc deposits are com- communities in developing countries shallow pit latrines mon in limestones. Some limestone deposit used for pro- are used for disposal of human exereta. Other undesir- duction of lime may contain appreciable quantities of able materials like expired drugs and unwanted chem- lead-zinc minerals. icals are also dumped into pit latrines or shallow water- In developing countries, the people and governments ways. Human exereta collected in bucket toilets are also place their priorities on food production in enough quan- emptied into the pit latrines. Water infiltration into the tities to stem the tide of hunger and mass deprivation ground through the pit latrines introduces a number of and little or no consideration is given to the pollution GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 63 implications. The poor farmers, most of whom practice developing countries have nuclear capabilities and subsistence agriculture, are highly encouraged to apply hence are generating high-level radioactive wastes, it fertilizer and use insecticides/herbicides for maximum becomes a matter of great concern to conjecture how crop yields. The prices for these chemicals are very low these wastes are being isolated from the biospheric en- and affordable as the governments have subsidized the vironment. So far, it is a top secret matter and those costs. Thus, the chemicals may be used indiscrimi- few developing countries that have nuclear capability nately. A large amount is released to the environment hardly provide any information to the public. to pollute surface water and shallow groundwaters. This practice is common in many developing countries. Pollution/Contamination from Natural Radioactive Contamination of Sources Groundwater Pollution and contamination may come from natural sources such as during physicochemical weathering and Another source of groundwater contamination is ra- mass wasting, soil and gully erosion, flooding, snowfall, dioactive wastes from power plants and mine dumps. wind activities, and seawater intrusion through wave One of the serious long-range problems associated with action, volcanic or gas eruptions, geochemical evolution the use of nuclear power plants is the disposal of highly through groundwater infiltration, and percolation. A radioactive nuclear wastes. These highly toxic wastes large quantity of pollutants and contaminants are re- are by-products of nuclear power plants and the man- leased from these sources but it is very difficult to quan- ufacture of nuclear weapons. These radioactive wastes tify and control release by natural processes. During are temporarily stored as liquids in tanks. Despite the weathering, geologic units are corroded, weathered, fact that the waste must be isolated from humans and disintegrated, and disaggregated, thereby releasing other organisms for many centuries before it is safe, it dissolved geochemical constituents into the hydrogeo- has not been possible to store the wastes for even a few logic systems. During sediment transport and deposi- decades without mishap. Several thousand gallons of tion, geochemical reactions (38,49) may result in the waste do seep into groundwater from storage tanks be- release of more ions and dissolved gases that may before anyone realizes there is a leak. Radioactive ma- come concentrated enough to be hazardous. In addition, terials in water even in very small amounts are harmful soil and gully erosion (16,17) may remove volumes of to all forms of life. Some developing countries are be- sediments with potential pollutants and contaminants lieved to have nuclear power. that may threaten the environment. In some situations The problem of disposal of radioactive wastes is es- deep gullying that intersects the watertable and shaley pecially common in industrialized countries, but the dis- terrains may result in hydrogeomicrobiological reac- posal of radioactive wastes in uranium mines is a prob- tions that may release deleterious pollutants into lem that occurs more in developing countries. Some groundwater (17). developing countries are producers of uranium and Snowmelt and rainfall and anthropogenic activities other raw materials needed for nuclear power plants. such as farming, excavation, and mining accelerate the In most of these countries, there are no regulations transport of sediments and enhance their pollution po- governing the disposal of mine wastes. They are tentials. Thus, in parts ofthe humid tropics, floodwaters dumped around and abandoned by the operators in the are densely brownish in color, reflecting high sediment mine environment. loads. Wind activities in areas at the fringes of deserts Uranium is usually present in the tetravalent state also transport sediments that pollute the environment. (U4+). In this valence state, uranium is not soluble, and Nigeria, Chad, Sudan, Niger, and other countries that is immobile. When exposed during mining and dumped are close to the Sahara Desert suffer from these prob- in mine waste, uranium is oxidized to the hexavalent lems. These types of pollutants are very serious, par- (U6+) state occurring as uranyl ion (UO"+). Uranium ticularly in developing countries because there does not then moves from an oxygen-rich surface environment, exist any plan to combat them. Some of these countries in which uranium is in the hexavalent state or com- may not even recognize their existence or just ignore plexed with carbonate into the subsurface groundwater them. Meanwhile the pollutants continue to ravage their environment. The problem of contamination of ground- environments. water in uranium mining areas by uranium and its daughter products in active and abandoned mines is as serious as those associated with nuclear wastes. In nu- Case Examples: Review of Pollution/ clear power plants, adequate precautionary measures Contamination in Some Developing are always taken in handling the radioactive wastes. In uranium mining areas no such precautions are taken Countries and the danger of contamination of groundwater by ra- India has emerged as an industrial nation and a major dioactive materials leached from mine dumps is great. producer of manufactured and agricultural products The problem is most serious in those developing coun- within the last 20 years. Because the population is large tries where the inhabitants of mining areas are not and industrial activities are intense, large volumes of aware of the problems. When it is realized that some gaseous, liquid, and solid wastes are continuously re- 64 EGBOKA ET AL. leased into the environment. Surface waters and shal- munities are equally not spared as present attempts to low and deep groundwaters have been polluted in urban develop rural areas have introduced many pollutants and rural areas (73-75). Neighboring countries of Pak- and contaminants into the environment. Soil and gully istan and Bangladesh are equally polluted or threat- erosion and flooding have become rampant and pollute ened. The excessive withdrawal of groundwater in the surface waters and groundwater. Outbreaks of water- Saurashtra area of India has resulted in sea-water in- borne disease such as cholera, yellow fever, dysentery, trusion. Parts of the groundwater in Gujarat State are diarrhea, and Guineaworm occur periodically, resulting mineralized and polluted by high temperature waters. in fatalities. Mining companies in Jos, Abakaliki, En- The groundwaters from the Khetri copper mines in Ra- ugu, Nkalagu, and the Port Harcourt areas pollute the jasthan, Mahakali coal field area of Maharashtra, and environments without restraint. Flaring of gases and the Panandhro lignite field pose geotechnical and pol- oil spills have contaminated surface waters and ground- lution problems. Currently, as a result of tourist activ- waters (10). There is yet no effective legislation to check ities, many ancient forest lands, hills, valleys, and even these problems. mountains are being strewn with garbage thrown away In a geochemical study of the Otamiri and Aba river by tourists thereby polluting the environments. watershed in southeastern Nigeria by Nwankwor and Kenya is a typical industrializing East African coun- Okpala (81), nitrate concentrations in the order of 100 try producing varying degrees ofpollution. Other neigh- mg/L were found in the groundwater and surface water boring countries of Uganda, Zimbabwe, Tanzania, Ma- systems of the Otamiri watershed. Nitrate loading of lawi, and Botswana are not spared. In a water resources the waters in the Otamiri watershed were attributed to quality survey by Nair et al. (76) from 1286 boreholes intensive use of fertilizer by various government-spon- from parts of Kenya, the majority of the samples sored agricultural establishments in the basin. Results (61.4%) have fluoride values above 1.0 ppm while 19.5% from the Aba River, which drains the largely industrial had above 5.0 ppm and sometimes in even greater city of Aba, showed abnormally high concentrations of amounts (76). Table 7 lists the summary of maximum Co + and gave values for pH that varied between 4.0 fluoride levels taken from each province and in different and 6.5 (81). locations in Kenya. The high fluoride areas coincided Egypt and the neighboring countries of Sudan and with volcanic rock areas. The high fluoride water caused Libya have polluted surface waters and groundwaters. extensive public health hazards such as deformity in Primary sources of pollution are industrial/sewage children. In Malawi, localized pollution of groundwater wastes, agricultural/irrigation activities, and saliniza- affects the quality adversely. Waters of up to 4000 to tion processes. Volumes of waste products are drained 7000 ,umhos/cm of electrical conductivity occur. High into the River Nile and eventually into the sea through sulfate iron and magnesium concentrations are common a complex network of canals. Some of the irrigation (77). Foster et al. (78) reported serious nitrate and fecal waters react with soil water/groundwater and with soil pollution of shallow groundwaters in parts of Botswana materials dissolving the soluble salts, salinizing the soil, through pit latrines. and increasing the salt concentration in irrigation canals Many hydrogeologic environments in Nigeria are pol- and groundwaters (82). luted (10,15,18,19,22,69,70). Saline lakes and hot Alexandria, with a population of about 3 million peo- springs occur (79,80). Coastal towns such as Lagos and ple, is the main industrial center and is burdened with Port Harcourt suffer from saltwater intrusions from the pollutants and contaminants from many sources. Parts Atlantic ocean. Inland waters such as rivers (Kaduna, of Meryut Lake have been destroyed by sewage, Niger, Anambra) and lakes (Chad, Agulu) have received thereby contaminating fish. According to Preul (82), pollutants in varying degrees. Industrial wastes are in- groundwater levels in lower Egypt rose considerably discriminately disposed of on land or into surface with the building of the Aswan dam in 1965. The re- waters. Sewage is similarly disposed of. Mineralized gional rise in water levels of shallow aquifers com- waters attack and destroy borehole networks in the pounded the problems of pollution spread through sub- Maiduguri areas of northern Nigeria. The rural com- surface disposal of wastewaters and irrigation water. Villages "are experiencing considerable difficulties with wastewater disposal due to subsurface saturation, high Table 7. Maximum fluoride concentrations in Kenyan water groundwater, emerging surface pools of septic waters, samples taken from each province (76). gross groundwater pollution, deterioration of buildings Flouride concentration, and structures due to moisture absorption, and other Province District ppm related problems. A further complication in certain Nairobi 30.2 areas is the existence of a large irrigation canal which Central Nurang'a 22.0 usually carries a level of flow above the general eleva- Coast Taita Taveta 15.0 tion of the village and therefore creates a hydraulic Eastern Machakos 19.3 gradient of seepage through the dykes towards the vil- Northeastern Wajir 38.2 Nyanza Kisumu 10.4 lage" (82). Rift Valley Nakuru 57.0 Even though the government of Egypt has environ- Western Bungoma 7.1 mental protection laws, their enforcement, particularly Nationally 57.0 in the rural areas, needs to be encouraged. These rural GROUNDWATER POLLUTION IN DEVELOPING COUNTRIES 65 communities continue to be exposed to increasing soil, problems will be one of the outstanding issues relating surface water and groundwater pollution. to the protection and conservation of the national stock Al-Jabari and Al-Ansari (83) described the dissolution of water in each country ... The rapid aggregation of of geological outcrops and soils in Iraq. These are rich population in major urban centers, the polarization of with calcium carbonate and gypsiferous deposits. Water industries, and the heavy dependence of chemical prod- inputs from flood plains and valleys with organic matter ucts, particularly in the agricultural sector, are leading contents reaching up to 20%, high suspended sediments, to a serious deterioration of water quality in developing inputs from springs (Table 8), and human activities pol- countries." Already parts of the environments of many lute the environment. Their pollution potentials are en- industrialized nations are highly polluted. The problems hanced by erosion. Tremendous amounts of dust gen- are being tackled with available manpower, expertise, erate fallouts from sediments in central Iraq at the rate and financial resources in these countries. Encouraging of 2.1 cm/yr (83-85). The sediments contain pollutants successes are yet to be achieved, as the pollutants con- and contaminants in the form of carbonates (calcite, tinue to diffuse and disperse into the hydrogeologic en- dolomite grains) quartz, feldspars, gypsum, chert, mus- vironment, and several tons of high-level wastes are covite, heavy minerals (pyroxenes, zircon, biotite, horn- piling up in storage tanks while desperate efforts are blende, epidote, rutile, garnet, chlorite, staurolite and being made to locate geologic formations for safe waste Kyanite), and pyrites (83-85). The heavy minerals as- disposal. semblage in the outfalls have been correlated with the de- heavy mineral content of the Tigris and Euphrates Riv- Unfortunately, in an obvious attempt by many ers flood plains and older dune deposits (Table 8). Sal- veloping countries to industrialize and compete with the man et al. (84), in their investigation ofbacterial density developed nations, waste products are being generated in Tigris River within Bagdad, measured a high density in large quantities. These countries have neither the of coliform bacteria and Escherchia coli, suggestive of manpower, expertise, nor the financial resources to con- fecal pollution from sewage disposal. The bacterial den- trol or safely dispose of these deleterious wastes. As a sity correlated well with high suspended sediment result, their environments are becoming heavily pol- loads, which are believed to transport the bacteria in luted at an alarming rate. The leadership of these coun- water. The high sediment concentration is accelerated tries seem to lack the will or the serious understanding by anthropogenic activities such as dredging, swim- to recognize and mount a control program. Because of ming, and solid/liquid disposal on land and water. this, pollution continues to spread unabated with its Pollution of surface water and groundwater in the attendant hazards and problems. In the next 10 years, developing countries of South America have also been unless something is done quickly, pollution levels in reported. Argentina, Brazil, Chile, Cuba, Nicaragua, many developing countries' hydrogeologic environ- etc., have been equally exposed. Brinkman (86) dis- ments would have reached such destructive levels that cussed the hydrogeochemistry of groundwater re- they may become uncontrollable. Destruction of plants, sources in the central Amazonian area ofBrazil. Ducloux animals, and humans through pollution-caused epidem- (87) also treated the central zone of La Pampa Province ics/diseases would have become commonplace as req- of Argentina. Other countries in Africa such as Ghana, uisite funds and materials for their control may not be Zaire, Sudan, Mauritania, Ivory Coast, etc., have been available. unduly exposed to the destructive hazards of environ- Developing countries must now learn from the mis- mental pollution (88,89). takes of the developed nations vis-a-vis pollutants and contaminants, to save their environments from pollution Summary and Suggestions damages for future generations. Some of the following pollution-control programs being pursued or imple- According to Fano et al. (1), "it may be expected that mented in many industrialized countries should be of over the next decade the management of water quality worldwide application. The present consciousness about the hazards ofpollutants and contaminants in developed Table 8. Water discharge and solute concentration of springs on River Euphrates (83). nations must be highly encouraged. Every effort must be made to reduce pollutant/contaminant loads into the Average discharge, Average TDS, environment through improvements in manufacturing Spring no. L/sec ppm techniques that could recycle waste products. More ef- 1 3110 ficient techniques for the destruction of high-level pol- 2 24 3272 lutants and contaminants before they can reach the hy- 3 3378 4 3700 3927 drospheric zones should be found through more 5 4 3002 research. Through more intense investigations, safe pe- 6 100 3880 dologic, and geologic formations for disposal of wastes 7 26 27910 can be located. The present careless dumping of wastes 8 360 3662 9 into surface waters or the poorly engineered subsurface 10 100 3445 burial of wastes must be stopped. These practices have 11 3662 damaged many hydrogeologic environments as these 12 4 2690 materials spread locally and regionally. The effects of 13 29 3080 geologic and pedologic structures and characteristics on 66 EGBOKA ET AL. the dispersion of pollution must be recognized in order Research programs in both developed and developing to be able to apply the correct engineered control meth- countries must give attention to sources and types of ods. pollution, modes of occurrence and spread, dynamics of At the moment, there is a loose/poorly coordinated, transport and dispersion, pollutants-life-expectancy, nonintegrated approach in the control of pollutants and and means of disposal of wastes. Development of effec- contaminants by various professionals involved in pol- tive control technology should be continuously and ade- lution research and control. Hydrogeologists, chemical quately funded. engineers, civil engineers, soil scientists, etc., do not The authors are grateful to The Anambra State University ofTech- seem to work together. The multidisciplinary and mul- nology, Nigeria and Federal University of Technology, Owerri, for tiobjective techniques are not appreciated by pollution their moral and financial support; Dr. K. 0. Uma, Dr. I. C. I. Okafor, control planners and managers, particularly in devel- and G. Onwuemesi for their various contributions; C. Nwokolo, Emer- oping countries. This unfortunate behavioral tendency itus Professor of Internal Medicine, University of Nigeria Teaching may result from poor training or professional pride and Hospital, Enugu, Nigeria, for his fatherly and academic encourage- hence must be discarded. Professionals working in pol- ments; and Bessie Nri for typing the manuscript. lution control must appreciate the contributions of others to maximize their successes. This could be achieved REFERENCES by proper training through improved curricula in higher 1. Fano, E., Brewster, M., and Thompson, T. 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