Deberes formales de las instituciones de carácter privado sin fines de

Recently, changing acliv1ties at the soil surface have tnnuenced the quality of groundwater These activ!Ues range from waste disposal, oil and chemical spllls and polluUon due ^lo

agricultural usage ol soils (Forslund, 1986).

In recent years. groundwater pollution has becOme Increasingly fell in Nigeria and In the v.or1d 1n general Studies have revealed that these waters are prone to pollullon lrom ftuorida, nilrates. heavy metals, pesbcides and a host of other chemicals Depending on the tJpe of soil, lhe distance from lho source ol poltubeln and the prevat1ing sanitary eood1bons ol

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the water source, the pollutants move into the groundwater Agricultural activities, soak­

away pits, refuse dumps, open drains contribute lo the nilrates and phosphates and other mineral matter in the groundwater (Sridhar, 1997b)

The contamination and pollution of groundwater emanates from two main sources: - ground surface and under-ground sources. The former is due to activities or nature and human population, whlle lhe latter is as a result of the geological nature of the watershed or

underground aquifer (lfeadi, 1982). As water moves through the hydrologlc cycle, its quahly changes. Practically all groundwater contain lmpunties and the nature and quantities may greaUy hinder their use. The pollution of groundwater may be described as lhe artificial (unnatural) Induced degradation of lhe quality of naturally occurring groundwater. This pollution has lhe ability or not only being able to hinder lhe use of such water, but can create hazards to public health through the spread of diseases or by its toxicity (Todd, 1980).

In the developlng ccuntries, contamination of water supplies by organic chemical Is less significant than biological pollutants. The major causes of pollulion lo groundwater sources anse from the varying use to which man puts water Thus, there arise a large number of sources and causes of pollullon that can modify the quality of the water derived from such sources (Todd, 1980) These coniaminallon have been on the Increase due to pollullon consequent upon human acti'llbes such as dolllesllc, lndustnal and agricultural, produang such poautant, as chlorinaled organic solvents, aromalJC compounds,, heavy metals, mtrales, cianldes and human and other waslBS (Park, 1991: Nash and McCal, 1995),

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Pollution and contamination from ground surface sources may include entrance of surface waters, drainage from refuse dump sites, seepage from septic drain fields and oil spill

migration, etc. They consist largely of solids, microbial organisms and in some cases, chemicals. Contamination or pollution from underground sources results from perforation of the underground aquifer by mineral salts of the surrounding bedrock In which the aquifer is located. The sail and mineral constituents of the surrounding bedrock are mineralized as the water percolates through the geological strata. The major constituents of the pollution due to these mineralization processes may take the form or high dissolved solids, high alkalinity or salinity, high presence of hardness contributing substances, sulphates, nitrates, and heavy metals such as Iron, lead, etc. (lfeadi, 1982). Table 3 presents a hsl of the quality problems associated with groundwater polluUon from different sources.

Although, "point sources" such as waste disposal sites, oil and chemical spills can ^be serious threat to the local groundwater source; emphasis should be on poUuUon or contamination due to the agricullural usage of soils. Important determinants of groundwater quality are the load of pollutants applied ^to the soil, the degradallon of these pollutants; the absorption processes and the amount of precipitates, which will dissolve the pollutants and transport them ^to the groundwater (Forslund, 1986) .

•

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Table 3

Some common groundwater quality problems

From land surfaces Above water· table Below water· table

Infiltration of polluted surface Septic tanks, cesspools and Waste disposal in wet excavations

water privies

Land disposal of solid and liquid Surface impoundment Agricultural drainage wells and

wastes Landfills canals

Stockpiles and tailings Waste disposal in excavations Well disposal of wastes Dumps Leakage from underground Underground storage Sewage and water treatment Leakage from underground Secondary recovery

Mines

sludges pipelines

Animal feedlots ArtJficial recharge Exploratory wells and recovery Agrochemicals Sumps and dry wells Abandoned wells

Accidental spllls Graveyards Water supply wells and

Particulate mauer (air-borne) aroundwater development

Source: Forslund, 1986; Nash and McCall, 1995; Ademorotl, 1996 and Sridhar, 1997c.

2.8.1 Pollution In relation to use of water

As a result of a diversity of human activ,Ues Impinging on the hydrological cycle, a complex and interrelated series of changes Is created in the natural quality of groundwater There is a limitless range of substances that can act as sources or causes or groundwater pollution, Their presence however, is a luncUon of being components of human acbv1ties in the Immediate environment of these water sources. These substances range from organic and inorganic chemicals to biological, physical and radlologlcal substances (Todd, 1980).

users of such water sources often contaminate them by introducing dirt into it. direcUy by the use or dirty contalners and staodmg In the water, ^0< lnd,recUy by allowing the occumulat,on of d,rty water at the surfaco This then percolates back Into the wator wtien not adequately pta!eciOO (Ha� and McCall, 1995) Other ways or polluting groundwatl'r soorces might

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include: lhe indiscriminate disposal and stockpiling of solid waste al factory sites and the poor handling of many industrial chemicals which results in leaching of such chemicals into

groundwater sources. Other sources of pollution include leaking storage tanks and pipelines especially of light hydrocarbons such as gasoline and diesel fuel, and leaching or landfill sites in urban seltlemenls

2.8.2 Types and sources of pollution of groundwater sources

Alt sources and causes of pollution of groundwater sources can be sub-divided as lo their geometry: whether point source (originating from a singular location), fine source (having predominately linear alignment) or a diffuse soun:e (occupying an extensive area that may or may not be clearly defined (Todd, 1980).

According to Todd, (1980), the major sources or groundwater pollubon include:

(a) Municipal-Sewer leakage; liquid waste; and solid waste

(b) Industrial -Liquid waste, tank and pipeline leakage, mining acbvites; and 01lrield bnnes (c) Agriculture -lrrigabon reform Hows; animal waste; lerblizers and soil amendments; and

pesllcldes

(d) Miscellaneous- Spills and surface discharges, stockpiles, septlc tanks and cesspools;

roadway de-Icing, saline water Intrusion; and Interchange through wells and surface water

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2.8.3 Effects of pollution on groundwater sources

Drinking water obtained from springs and other sources are liable to pollution. The hazards are increased as induslrial activities are intensified, and as new chemicals are developed, many of which are toxic, or have mutagenic or carcinogenic effects (Nash and McCall, 1995). The most significant groundwater pollution problems are associated with the presence of nltrates, pesllcides and organic solvents. The nitrate situation for example, is a

typical illustration of the manner in which a hitherto cheap (relative to surface water) and reliable potable water source can be affected by contemporary situation (ISCV, 1990).

For quite sorneUme now, the pollution of drinking water by nitrates has been on the increase.

This has been associated with the occurrence of methaemoglobinaemla In Infants (Sridhar, 1997c), and present knowtedge about the in-vrvo transfonnalion of nitrates and the fonnalion of N-nltros<XOmpounds justifies the assumpuon that nitrate may be active in the aetiology of stomach cancer {Forslund, 1980 and Packham, 1990).

The acidlficatiOn of groundwater due to dissolution of gases in the atmosphere and their subsequent percolation can result in lnaeased levels of melals In dnnklng water, and probably also ^to increased deposits of heavy metals In the human body The metal content of groundwater can be reduced lo acceplable levels wtlh appropriate water troalmenl II groundwater rnmalns untreated, Yiiilch is usually the case for private groundwater supplies

In rural ^8'C3S, the natural dissolved metals wtll bo present ^In such water, and at

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unacceptable levels or concentrations, intestinal problems such as diarmoea have been noted as well as hair coloration (Forslund, 1986).

Numerous studies have shown lhat water contaminated by biological pollutanls such as bacteria and viruses derived from human faeces and olher wastes are lhe principal agenls In the transmission of cholera, diarrhoea, infective hepatibs, skin lnreclion and dysentery (World Bank, 1976 and Park, 1991). Similarly, studies have shown lhat groundwater can be contaminated lhrough seepage by leacheates arising from solid waste dumped on lhe ground near such water sources. Case studies have been conducted on three shallow weUs sited near dumps or some solid wastes. Results arising from the sludy revealed that the groundwater beneath is generally polluted by the contaminants migrating from the dumpsltes or lhe solid wastes. The results also revealed that groundwater sources could be contaminated by surface contaminants migrating through the soils (AdemoroU, 1987).

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In document Análisis del impacto de las exenciones en el pago del impuesto a la renta, de la ciudad de Loja, año 2013. (página 113-120)