International Journal of Scientific & Engineering Research, Volume 4, Issue 12, December-2013 1616
ISSN 2229-5518
Assessing Inorganic Pollution in Ground Waters within an Agricultural Area of Northeastern Algeria
Labar Sofiane, Djidel Mohamed, Hamilton C. Mei-Ling, Benslimane Farida, Hani Azzedine
Abstract— El-Tarf City, which situated in the north east of Algeria, has mostly focused its economic development on agricultural activities.
+),
The principal objective of this study is to assess in a particular context, the impact of inorganic pollution induced by ammonium (NH 4
-), nitrites (NO -), and dissolved oxygen, on the quality of ground waters. The samples studied to that end are those taken in
nitrates (NO 3 2
2012 and 2013 from the groundwaters of the Bounamoussa basin in far north-east Algeria. Results shows that the degree of pollution varies by zone, as well as by month to month with contents often exceeding recommendations made by the World Health Organization (W HO). The protection of water quality and the reduction of the risk contamination are of great importance in the region to a reliable and sustainable water supply.
Index Terms— Coastal aquifer, Agro-hydrobiology, Water quality, Nitrate, Nitrie, Ammonium, Phosphate, El-Tarf region..
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HE Contaminant increase within aquatic systems meas- ured in recent years, as well as the progressive nature of pollutants and the subsequent chemical transformations
Groundwater is one of the most precious natural resources in northeastern Algeria, as it is the principal source of drink- ing water for the majority of the population.
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leading to toxicity in both the short and long term have made
groundwater monitoring and water quality assessment of
foremost concern in hydro-ecological research [1]. Nitrates
constitute the main parameter of inorganic pollution. These
nitrogenous compounds are essentially found in chemical fer-
tilizers, and manures; and constitute the major source of nitro-
gen to crops.
Farmers have augmented fertilizer use up to 500 kg/ha so
as to assure successful crop production. However, if too much
fertilizer is used, an excess of nitrates will result. This excess
may become a potential contaminant to the ground water sys-
tem, via nitrate infiltration through amended soils to the groundwater table.
Inorganic contaminants are responsible for the “bad taste” aggravated by chlorination, stimulate the proliferation of mi- crobes, molds and algae resulting in eutrophication [2]; and high level of nitrates have also been linked to detrimental ef- fects in human health [3], [ 4], [ 5].
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• Djidel Mohamed is currently an associate professor in department of geol- ogy in Kasdi Merbah University, Ouargla, Algeria, Country, PH-
+21329711902. E-mail: djidelm@yahoo.fr
• Hamilton C. Mei-Ling is currently an associate professor in Department of
Geological Sciences California State University Bakersfield 9001 Stockdale
Highway, Bakersfield, CA 93311-1022 USA,Country, PH-+21329711902.
E-mail: c.meilinghamilton@gmail.com
• Benslimane Farida is currently a Phd student in department of biology,
in faculty of natural and life sciences in Badji Mokhtar Annaba University
, Algeria , Country, E-mail: benslimane2405@yahoo.fr
• Hani Azzedine is currently a professor in department of geology, in faculty
of earth sciences in Badji Mokhtar Annaba, University , Algeria , Country,
PH-+21338876562. E-mail: haniazzedine@yahoo.fr
The groundwater aquifer of Annaba-El-Tarf region is ex-
tremely susceptible to surface-derived contamination because
of the high permeability of sands and gravels that compose the
soil profile of West El-Tarf region [6].
Several studies in El-Tarf region reported various degrada-
tions levels of groundwater as one of the major concerns
among the public and governmental decision makers [7], [8],
[9] but these studies did not include an evaluation of inorganic
pollution of groundwater contrary the surface waters.
Groudwater contamination can occur if input of (NO3 -) into soil exceeds the consumption of plants and denitrification pro-
cesses [10]. Nitrate (NO3-) and nitrite (NO2-) are naturally oc- curring inorganic ions, which are produced in the Nitrogen (N) cycle [11], [12]. Microbial action in soil or water decom- poses wastes containing organic nitrogen first into ammonia, which is then oxidized to (NO2 -) and (NO3 -) [10]. Because (NO2 -) is easily oxidized to (NO3 -), (NO3 -) is the compound predominantly found in groundwater and surface waters un- der oxidizing conditions. Contamination with N containing fertilizers, including anhydrous ammonia, as well as animal or human natural organic wastes, can raise the concentration of (NO3 -) in groundwater [13], as nitrate (NO3 -) containing com- pounds within the soil matrix are generally soluble and readi- ly migrate into groundwater systems [14], [15]. The main ob- jectives of this study were: (1) to determine the average levels and distribution of NO3-, NO2 -, NH4 +, and PO4 3- in the groundwater of the El-Tarf region (Bounamoussa basin), and (2) to assess during all the year the temporal evolution of inor- ganic pollution parameters.
The Bounamousa watershed is situated in the extreme north- east of Algeria and adjoins the Mediterranean Sea with the
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“Kebir Est” river in the East by a unique release: the Mafragh river (fig. 1) [16], [17].
The region of study is subjected to a Mediterranean climate characterized by two different seasons: one wet, marked by high rainfall and low temperatures from October to May, and other dry and warm with high temperatures reaching their maximum in August with low rainfall. Prevailing southernly winds blow off of the sea during the winter; and in summer, the hot Sirocco blows in a south-southwesternly direction, carrying with it a drying effect that is strongly felt during a one month period of time [18], [19].
The region of study is a part of the geologic whole north- oriental Algerian Tell. This group extends of the region of Constantine on the border between Algeria and Tunisia. In general, the study region includes the following units [16], [17] (Fig. 1) :
hydrological data of most stations in the east of Algeria shows the extreme spatial variety of the specific discharges (0.32 -
16.1 L/s/km2 caused by the decisive role of the climate, particularly that of rainfall [19].
The Bounamoussa catchment basin has a surface area of
1158 km2 and an average annual streamflow of 4.45 m3/s.
This surface water flow is characterized by a period of high
stream discharge from November to April, and a second
period of low stream discharge from May to October. Its
annual fresh water contribution varies between 36 and 369
hm3 with an average of 140 hm3/year [18].
The hydrogeology of this study region is defined by a deep layer of gravels surmounted by an unconfined layer covering the entire plain. This layer is limited by two separate superficial or surface water tables: one to the South composed of gravel and pebble terraces, and the other to the North of Cordon dune composed of dune sands based on clayey substratum [6], [18].
Water samples were collected from the Bounamoussa catch- ment basin downstream during the period from June 2012 to
May 2013.
Groundwater samples were filtered through 0.45 μm (Sartori- us filter); the first few milliliters were used for rinsing and were discarded. The filtrate was transferred to clean polyeth- ylene bottles and stored at 4 °C.
The temperatures (T), electrical conductivity (EC), (pH) were measured in situ using a multi parameter conduct a (pH) me- ter. Dissolved oxygen and turbidity were also measured at the same time. The concentration of Nitrate (NO3 -), Nitrite (NO2 -),
Fig. 1. Geographic and geologic situation of Annaba-ElTarf re- gion [16] (modified).
Legend : 1 : Current and recent alluvium; 2 : Dunes; 3 : Old alluvium; 4 : Swamp or lake; 5 : Numidian sandstone and clay ;
6 : Metamorphic facies ; 7 : Fault ; 8 : Axis pits; 9 : Cutting alignment caption.
- The Triassic formation located in the South of the region of
Ammonium (NH4 +) and phosphate (PO4 3-) were measured using the UV spectrophotometric screening method according
to standard examination methods of water and wastewater from the American Public Health Association (APHA), Ameri- can Water Works Association (AWWA), and the Water Envi- ronment Federation (WEF), [20].
study (Triassic diapirs, vermiculated limestone and pelitic4 4 RESULTS AND DISCUSSION
sandstone formation);
- The metamorphic formations situated in the massif of
Edough (Annaba city) are dominated by schist, gneiss, marble and amphibolites;
- The sedimentary rocks of Oligocene to lower Burdigalian age are dominated by sandstone, clays and marls;
- The Quaternary formation, composed of sedimentary rocks of marine origin (e.g., alluvial deposits and beach sandstone), and continental origin (e.g., red land sand dunes, fluvial allu- vium, and colluviums).
Eastern Algeria, with its highly contrasted semi-arid climate, is drained by opposing hydrographic systems trending from North to South: the tributary watersheds of the Mediterranean sea to the north, and a riverine system connected to closed drainage basins to the south. The
The groundwater table is characterized by shallow depths which are generally inferior to 5m with a minimum of
0.5 to -3m (fig. 2) [9], [18], [21]. These depths were observed down the gradient of the drainage river and in the coastal zone. The over flow direction of the aquifer is SW-NE [9], [18], [21]. The presence of a shallow depth piezometric level within the coastal area indicates another potential source of pollution: seawater intrusion in the north of the region study [9], [21]. So, the piezometric monitoring (fig. 2) [9] allows to highlight a general decline in levels and the following conclusions:
- The presence of some depressions with less than the sea level ratings and the decline in the general level of the water causes mainly an increase in the fresh and salt-water,
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- The permanent extension of the curve of zero rat- ing caused by pumping reflects an intrusion of sea water into fresh water through a transition zone,
- The significant decline of groundwater levels es- pecially in times of low water and low seasonal fluctuations in the water leads to a reduction of freshwater flow and penetration of marine waters under the fresh water from the aquifer.
Interpretation of the diagrams representing the various pa- rameters concerning inorganic groundwater pollution gives rise to possible contamination of this particular groundwater system [22].
The evolution (dissolved O2- nitrates) of the surfacial wa- ter table in the Bounamoussa basin (fig. 3) shows a decline in nitrate concentration during the period from April to Septem- ber most likely due to the) lack of precipitation, and an en- richment of the environment in dissolved O2 between Sep- tember and January which is confirmed by the presence of nitrates.
Fig. 4 (O2-Ammonium) shows an oxidized enough envi- ronment marked by small quantities of NH4 +.
The ammonium of ground waters may originate from the fol-
lowing sources:
- Stream vegetation;
- Animal or Human organic wastes (Man eliminates 15 - 30 g
of urea a day);
- Industrial discharges;
- Chemical fertilizers, manures etc.
Its presence is relatively similar to the others Nitrogenous
compounds identified in the water: Nitrites and nitrates.
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1,4
8 O2 NH4
7
6
5
4
3
2
1
1,2
1
0,8
0,6
0,4
0,2
0 0
Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May
Fig. 2. Evolution of the piezometric level from 1978 to 1996 [9]
Fig. 4. Evolution of dissolved oxygen and ammonium of ground waters
100
90
80
70
60
50
40
30
20
10
0
O2 bO3
Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May
The figure below (fig.5) illustrates high concentrations in ammonium, nitrate and nitrite ions in groundwater, as opposed to an evident decrease in dissolved oxygen content during the dry period between June and November, where lack of precipitation is common. It follows that nitrates decrease to be transformed nitrites (NO2-) and to be finally reduced to NH4+. We therefore bear witness to the natural microbial respiration process of denitrification, which most likely led to the consumption of dissolved O2 in the groundwater [23]. Nitrites result from the incomplete oxidation of ammonia in water. Therefore, either the nitrification process is not driven to completion, or nitrite
production is a direct result of nitrate reduction during the
Fig. 3. Evolution of dissolved oxygen and nitrate of ground waters.
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denitrification process. Water which contains nitrites is to be considered as suspect because a deterioration of the biological quality is often associated with it.
Fig. 5 Evolution of nitrite, nitrate and ammonium of ground waters.
The pollution represents a severe problem for the environment because of discharges in the rivers of Kébir East and Boun- amoussa [23] due to the excessive use of fertilizers in agricul- ture.
The degree of pollution varies by zone, as well as by month to month with contents often exceeding recommendations made by the World Health Organization (WHO) [24]. We can note a significant agreement between pluvio-thermal variations and dissolved oxygen in groundwater.
In this region of study, even if groundwater concentration of inorganic contaminants (especially NO3 -) does not exceed ac- cepted standard limits, the situation still poses serious risk. The current state of groundwater pollution is the reflection of nitrated substances infiltrated a few years before - the im- portance of the transfer time dependent on the depth of the groundwater and on the structure of the rock [25].
In spite of efforts made to raise awareness to nitrate ground-
water pollution, nitrate fertilizer use has not decreased, but
has increased due to surface tilling practices linked to in-
creased crop production and progressive agricultural devel-
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All this is confirmed by the agreement or correspondence
between the evolution of the pluvio-thermal diagram and dis- solved oxygen (Fig. 6) during the dry and wet periods previ- ously discussed.
The evolution of the concentrations in ammonium, nitrates and nitrites of the ground water in the down of Bounamoussa basin (Fig. 5) shows between January and April an increase of NO3 -, NO2 -, and NH 4 + provoked by the contribution of ferti- lizer. The presence of organic matters is due to the washing.
Indeed, the migration of nitrates is increases rapidly on cul- tivable surfaces left naked exposed during winter. Communal and, in some instances, industrial discharges of chemical ferti- lizers and explosives may also contribute to nitrate enrichment of the superficial groundwater table.
The pluvio-thermal and dissolved oxygen diagram (Fig. 6)
are in agreement. We note an increase of dissolved O2 during
the dry period (from May to November) and a decrease be-
tween November and May (wet period).
opment.
Finally we recommend:
– Several studies should be conducted mainly on the health
risk assessment and water toxicology.
– An integrated monitoring program should be conducted.
The municipal wells should be sampled 2–4 times a year for
the analysis of anions, cations, heavy metals and pesticides.
The data of the groundwater quality should be centralized in a data bank or a water archive.
– The objective of the Algerian water institutions should be how to safeguard the water resources system from pollution. The protection of water quality and the reduction of the risk contamination are of great importance to a reliable and sus- tainable water supply [26].
We are grateful to the staff of the direction of environment of El-Tarf department. The ground and field works have con- ducted in collaboration with them.
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Fig. 6 Graphical representation of climate diagram and dissolved oxygen.
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