Scholarly article on topic 'Study of the Behavior of Some Pollutants and the Vulnerability to Chemical Contamination of Groundwater in the Region of Ouargla (Southeast Algeria)'

Study of the Behavior of Some Pollutants and the Vulnerability to Chemical Contamination of Groundwater in the Region of Ouargla (Southeast Algeria) Academic research paper on "Agriculture, forestry, and fisheries"

CC BY-NC-ND
0
0
Share paper
Academic journal
Energy Procedia
OECD Field of science
Keywords
{"Pollutants behavior" / water / "contamination index" / Ouargla}

Abstract of research paper on Agriculture, forestry, and fisheries, author of scientific article — M. chaouki, A. Zeddouri, S. Hadj-Said

Abstract Over the recent years, the region of Ouargle has registered remarkable entropic and natural anarchy. This drastic evolution produced an important contamination of the shallow aquifer by pollutants. This region was being subjected to a large degree of vulnerability favorized by waste water discharges (domestic and irrigation). These factors expose the shallow aquifer water to a severe pollution. To assess this pollution, regular monitoring of water quality was conducted (February 2009, 2010, 2011 period). The obtained results show that the groundwater is non-potable for human consumption. Consequently a severe irrigation risk threatening plants and soil is then established. The determination of organic pollution index (OPI) has been evaluated by plotting its evolution map over the region of Ouargla. This study has enabled us repering the more vulnerable pollution site. In such environment the elimination of pollution sources becomes urgent.

Academic research paper on topic "Study of the Behavior of Some Pollutants and the Vulnerability to Chemical Contamination of Groundwater in the Region of Ouargla (Southeast Algeria)"

Available online at www.sciencedirect.com

ScienceDirect

Energy Procedia 36 (2013) 1043 - 1049

TerraGreen 13 International Conference 2013 - Advancements in Renewable Energy and Clean

Environment

Study of the behavior of some pollutants and the vulnerability to chemical contamination of groundwater in the region of Ouargla

(southeast Algeria).

M. CHAOUKIa, A. ZEDDOURIb, S. HADJ-SAIDb*

aUniversité Kasdi Merbah Ouargla, Département de Génie des Procédés, Faculté des Sciences et de la Technologie et des Sciences de la Matière,

Ouargla 30000 Algérie.

_bUniversitéKasdi Merbah Ouargla, Département de Géologie, Faculté des Sciences de la terre et de l'univers, Ouargla 30000 Algérie._

Abstract

Over the recent years, the region of Ouargle has registered remarkable entropic and natural anarchy. This drastic evolution produced an important contamination of the shallow aquifer by pollutants. This region was being subjected to a large degree of vulnerability favorized by waste water discharges (domestic and irrigation). These factors expose the shallow aquifer water to a severe pollution. To assess this pollution, regular monitoring of water quality was conducted (February 2009, 2010, 2011 period). The obtained results show that the groundwater is non-potable for human consumption. Consequently a severe irrigation risk threatening plants and soil is then established. The determination of organic pollution index (OPI) has been evaluated by plotting its evolution map over the region of Ouargla. This study has enabled us repering the more vulnerable pollution site. In such environment the elimination of pollution sources becomes urgent.

© 2013 The Authors. Published by Elsevier Ltd.

Selection and/or peer-review under responsibility of the TerraGreen Academy

Keywords: Pollutants behavior, water, contamination index, Ouargla;

1. Introduction

The pollution affects as well the industrialized countries as those in the process of development. The problem is particularly serious for the countries whose climate is arid. Because of a pronounced hydrous deficit, the concentration of the pollutants in water remains high whereas their capacity of recycling is very low.

In the case of the basin of Ouargla, the pollution generated by the discharge of wastewater has reached an alarming level due to the diversity of pollutants and the large quantity of wastewater (40906 m day-1 for the year 2005) [1]. The surface aquifer, is exploited by wells for agricultural and domestic purposes, crossed by a collecting in the open air canal, pollution deteriorates quality and limit its uses. Thus we make state of the contamination of the surface aquifer water by the anarchistic urban rejections. The main factor influence this situation is topography [2].

The analysis of the physico-chemical and organic parameters indicated a temporarily evolution of the concentration variation of the mineral and organic elements. The hydro-chemical study was based on the physic-chemical analysis of some samples from the studied region.

The determination of Organic Pollution Index (OPI), with the physicochemical study of waters coupled with the distribution of organic parameters in the aquifer's water, can draw some conclusions as to the biodegradation of organic matter and power self purification of the water.

1876-6102 © 2013 The Authors. Published by Elsevier Ltd.

Selection and/or peer-review under responsibility of the TerraGreen Academy

doi:10.1016/j.egypro.2013.07.119

On the basis of the previous results regarding nappe phréatique, we attempted_to evaluate the vulnerability of this latter to pollution. This step is mainly based on the determination of OPI. The map evolution is of great importance in the protection against pollution.

2. Materials and methods

The area of Ouargla is situated north-east of the Great Algerian Sahara, it is distant 850 km from the capital Algiers. It is limited to the north by Djelfa and El-Oued departments, to the south by Illizi and Tamanrasset departments, to the west by Ghardaia department and east by Tunisia. The Basin of Ouargla corresponding to a great depression (a big Oasis of the Algerian Sahara), which covers an area

Its natural limits are defined males: it is limited to the west by a calcareous plate, to the east by a plate whose boundaries are not clear; to the south by a massive dune covers the ruins of Sedrata and the North by Zabret Bouaroua.

The appearance climate of the region is desert or hyper arid: precipitations are low and erratic, ranging from 0.01 and 17.2 mm by exceptional year [4]. Temperatures vary greatly between night and day. The average annual temperature ranges from 06°C (January) and 43°C (July). The evapotranspiration, also varies between 380 (July) and 112 mm (January).

The lithology of the aquifer consists of fine to medium sand clay, rarely coarse south of Ouargla and more to the North (N'goussa) sands are rich in gypsum, which becomes dominant Sebkhet Safioune [5]. At the basin of Ouargla the surface aquifer is not exploited because of the rate of salt contained in its waters. It is thick from 1 to 8 m and is based on a tight impermeable level, which occupies the bottom of the valley of Ouargla and isolates it from the underlying aquifers. The aquifer is recharged by: . Wastewater discharges of domestic origin . Excess water tied to a palm irrigation irrational

. Runoff from the upper sections and the input of the three Wadis flooding in the bassin (N'sa, M'zab and M'ya) The harmful effects of the rising water in the basin are mitigated by the existence of the drainage systems (canals), including those of palm (total length 80 km) and the crossing of Sebkha Bamendil and the entire northern part of Ouargla (10.5 km). All these effluent water is pumped evacuated to the Sebkha Oum-Raneb (Fig. 1) located 8 km north of the town of Ouargla. The total flow of wastewater is 29900 m3 day-1 forthe year 2005, with 61% network and 39% individual assainissement,12900 m3 day-1 deversed in the aquifer and 17000 m3day-1 in the surface (drains and chotts)

Fig. 1. Localization of the studied area.

In order to monitor the behavior of pollution in the aquifer and the canal, we used physico-chemical complemented by measures of organic parameters in the piezometers (aquifer). The analyses are carried out according to standard AFNOR. Eight sampling campaign were made in 2009, 2010, 2011 with a time interval of 25-30 days.

The methods developed in the interpretation of data are based on the use of Surfer 9 program, resulting in the calculation of Organic Pollution Index (OPI). The principle of the OPI is to spread the values of polluting elements in 5 classes (Table 1) and then determine, from its own measures, the number of corresponding class for each parameter and then to make the average [2].

Table 1. Classes of organic pollution

Parameters classes Nitrates Nitrites Phosphates

(mg-N L-1) (re-N L-1) (^g-P L-1)

Classe 5 < 0,1 < 6 < 16

Classe 4 0,1 - 0,9 6- 10 16 - 75

Classe 3 1,0 - 2,4 11 - 50 76 - 250

Classe 2 2,5 - 6,0 51 -150 251 - 900

Classe 1 >6 > 150 > 900

OPI = average number of classes of 3 parameters (at best):

• 5.0-4.6: Null organic pollution

• 4.5-4.0: Low organic pollution

• 3.9-3.0: Moderate organic pollution

• 2.9-2.0: High organic pollution

• 1.9-1.0: Very high organic pollution

Fig. 2. Inventory map of the studied water points.

To perform our objective, eight samples have been selected from Ouargla region as indicated in table 2.

Table 2. Codification of water points

P1 Matmora

P2 Mekhadma

P3 Said Otba

P4 N'goussa

P5 Sidi khouilde

P6 Bour El haicha

P7 El bour

P8 Bamendil

2.1. Behavior of some mineral pollutants (TH, SO4~2, Cl)

Fig. 3. Concentrations evolution (in ppm) of mineral pollutants

The total durty (TH) present an important variation. This can be explained by both lithologie nature of aquifar formation and particularly the composition of magnesium and calcium (natural pollution). Sulfates (SO4-2) presence reflects the dissolution of gypsus formation and the presence of pesticides coming from water of irrigation. Chloride (Cl-) origins are essentially salifere formation and waste water (entropic pollution).

2.2. Behavior of some organic pollutants (NO3~, NO2~, PO4'3):

Fig. 4. Concentrations evolution (in ppm) of organic pollutants

Nitrates (NO3-) represent the most oxygenated nitrogen soluble form. Their presence in groundwater is related to the intensive use of chemical fertilizers. Nitrites (NO2-) have completely the contrary behavior. They represent the intermediate toxic form between nitrates and ammonium. The nitrogen and phosphorus are also indicative parameters of eutrophication. The fragility of the environment study was taken into account by tracking mineral nutrients in the water (NO3, NH4 and PO4) [7]. Phosphate (PO4-3) coming from drainage and leaching of farmland contaminate groundwater. Agricultural fertilizers have roughly the same effect as organic waste [8].

2.3. Vulnerability to chemical pollution

The groundwater vulnerability to these pollutants is related to different factors. The filtering power, the thickness of the non saturated zone and the reservoir nature (captive and free) are among those parameters.

2.4. The Organic Pollution Index (OPI) evolution:

The index values of organic pollution indicate the variation of the pollution classes by decomposition or autopurification water (Figure 5). Shows families relating to the wastewater indices ranged from 2-2.9, showing a single class of organic pollution high, corresponding to Sidi Kuouiled region.

3560000

3555000

3550000

3545000

3540000

3535000

3530000

710000 715000 720000 725000 730000

Fig. 5. OPI map evolution in the region of Ouargla

3. Conclusion

Monitoring of physico-chemical parameters and organic which is based on physicochemical analysis of a number of samples allowed us to detect a change in a temporary increase in the concentrations of all elements (chemical and organic). The spatio-temporal evolution shows a high nutritional and mineral concentration (pollution), this is mainly due to intense evaporation and pollution (agricultural and domestic), and biodegradation of organic matter.

Waters of the basin Ouargla have a very strong mineral pollution especially in the region of Ngoussa. Water quality of the shallow aquifer of the basin Ouargla shows non-potable water for human consumption with a severe risk for the soil and plants. Having analyzed the water after the water table we discussed the vulnerability of groundwater water pollution, the vulnerability map is of paramount importance for protection against pollution. The results of analyzes carried out showed:

We remark 4 levels of contamination index:

• level null where the value of OPI is very low, with a very low vulnerability to pollution which corresponds to the region of Ain El Beiada

• the low level when the IPO value is low, with low vulnerability to pollution, which corresponds to the region, and N'goussa El-Bour

• A moderate level which corresponds to the region Matmora, Mekhadma, Frane and Hassi Ben Abdallah.

• The region where the IPO value is large with a high vulnerability to pollution corresponds to the region of Sidi Khouiled.

To remedy the problems of groundwater harmful to the environment it is necessary to undertake companions awareness related to protection against any kind of pollution we water resources (groundwater, Senonian ... etc.) professionals in the community (agriculture and industry), Great public and school.

References

[1] Slimani, R. Contribution à l'évaluation d'indicateurs de pollution environnementaux dans la région de Ouargla: Cas des eaux de rejets (agricoles et urbaines). Mémoire de Magister, Université de Ouargla, 2006 pp. 95.

[2] Djidel, M. Pollution minérale et organique des eaux de la nappe superficielle de la cuvette de Ouargla (Sahara septentrional, Algérie). Thèse de doctorat, Université Badji Mokhtar d'Annaba, 2008, pp. 01.

[3] Zeddouri, A. Caracterisation hydrogéologique et hydrochimique des nappes de complexe terminal dans la région de Ouargla Sud-Est Algérien. Thèse de doctorat, Université Badji Mokhtar d'Annaba, 2010, pp. 04.

[4] Bonnard and Gardel. Vallée de Ouargla. Etudes d'assainissement des eaux résiduaires, pluviales et d'irrigation. «Mesures complémentaires de lutte contre la remontée de la nappe phréatique». Mission IA Reconnaissances et diagnostic de l'assainissement, 2001, pp. 156.

[5] Nezli, I. Mécanismes d'acquisition de la salinité et de la fluoruration des eaux de la nappe phréatique de la basse Vallée de l'Oued Mya (Ouargla). Mémoire. Magister, Université Badji Mokhtar d'Annaba, 2004, pp. 152.

[6] Bonnard and Gardel. La Vallée d'Ouargla. Etudes d'assainissement des eaux résiduaires, pluviales et d'irrigation Mesures complémentaires de lutte contre la remontée de la nappe phréatique. Investigations, essais de pompage et bilans d'eau, établissement des cartes piézométriques, diagnostic des captages d'eau et mesures de réhabilitation, de protection des ressources en eau. Mission II, Rapp. Final, 2004, pp. 110.

[7] Cornaz, P. Evaluation du statut trophique d'un canal de drainage sous l'impact des pollutions d'origines diffuses et ponctuelles: Le cas du Grand Canal de la plaine du Rhône. Mémoire. Magister, Unil, 2004, pp. 152.

[8] Klepper, S. La pollution par les phosphates. Cours MSE, 1999, pp. 44.

[9] Kherici, N. Vulnérabilité a' la pollution chimique des eaux souterraines d'un système de nappes superposées en milieu industriel et agricole (Annaba - la Mafragh) N-E algérien. Thèse de doctorat, Université Badji Mokhtar d'Annaba, 1993, pp. 98.