a re-appraisal of groundwater quality in parts of central...

International Journal of Advanced Materials Research

Vol. 1, No. 3, 2015, pp. 102-112

http://www.aiscience.org/journal/ijamr

* Corresponding author

E-mail address: [email protected]

A Re-Appraisal of Groundwater Quality in Parts of Central Benue Trough, Nigeria

Okonkwo Austin Chukwuemeka*

Department of Geology and Mining, Enugu State University of Science and Technology, Enugu, Nigeria

Abstract

A re-appraisal of groundwater quality in some parts of Central Benue Trough had been carried out. Areas sampled are within

the Lafia-Keana in the Central Benue Trough. Water wells in the area tap the shallow Lafia Formation which is made up of

whitish to brownish, feldsparthic and ferroginized sandstone. Physic-chemical analyses indicate pH range (4.7 – 8.20) from

acidic through neutral to moderate alkalinity. Total Dissolved Solids (TDS) values were high in most locations with their

corresponding high electrical conductivity (EC). Total hardness (TH) shows that 75% of the groundwater is classified as very

hard as a result of high calcium content. Piper Trilinear diagram show Calcium – Bicarbonate water type. High sulphate ion

enrichment may be due to the ionic reaction from coaly formation underlying the area. Sodium Adsorption Ration (SAR) show

excellent for irrigation purpose. Calcite saturation analysis shows that most of the wells are oversaturated with respect to

calcite. Generally the groundwater in the study area is greatly impaired when compared with the WHO standard limits for

drinking water. Possible ways of improving the groundwater quality are through aeration method and installing a workable

water treatment plant.

Keywords

Hydro Geochemistry, Sodium Absorption Ratio, Calcite Saturation index and Groundwater Quality

Received: April 3, 2015 / Accepted: May 21, 2015 / Published online: June 23, 2015

@ 2015 The Authors. Published by American Institute of Science. This Open Access article is under the CC BY-NC license.

http://creativecommons.org/licenses/by-nc/4.0/

1. Introduction

The Central Benue Trough is the Middle sequence in the

elongate, broad synclinal NE-SW stretching Benue Trough

(Figure 1). It is about 800km in length and 150km in width

(Obaje, et al, 1999). The area is characterized by many

human activities ranging from mining, quarry, indiscriminate

disposal of solid and liquid waste, poor landuse and huge

earthworks (boring) constructions. Previous studies in this

area include the petroleum potential of rocks in the area

(Obaje, et al, 1999), sedimentation, paleogeography and

geodynamic evaluation (Nwajide, 1990, Ojoh, 1992), the

geology with emphasis on the natural water system (Offodile,

1976) and the environmental implications of the mining

activities. However, based on the foregoing if appears that

the study area is environmentally degraded and this to an

extent will affect the natural water system. This study hopes

to re-appraise the geochemical characteristic of the Natural

water system for the benefit of the end-users (domestic

purposes).

2. Geology and Hydrogeology

The study area consists of six upper cretaceous lithogenetic

formation (Table 1).These include Albian Arufu, Uomba,

Gboko Formations, generally referred to as the Asu River

Group (Offodile, 1976 and Nwajide, 1990). These are

overlain by the cenomanian keana and Awe Formation and

the Cenomanian – Turonian Ezeaku Formation. The Ezeaku

Formation is coterminous with the Konshisha River Group

and the Wadata Limestone in the Makurdi area. The late

International Journal of Advanced Materials Research Vol. 1, No. 3, 2015, pp. 102-112 103

Turonian-Early Santonian coal-bearing Awgu Formation lies

conformably on the Ezeaku Formation. In the Makurdi area,

the Makurdi sandstone interfingers with the Awgu Formation.

The Mid-Santonian was a period of folding throughout the

Benue Trough. The post-folding Campano-Maastrichtian

Lafia Formation ended the sedimentation in the Central

Benue Trough, after which widespread volcanic activities

took over the Tertiary.

Figure 1. The Benue Trough of Nigeria (modified from Petters 1982).

Table 1. Stratigraphic succession of formation in the Central Benue Trough (Source: Modified from Offodile, 2000)

Geologic Age Formation Lithologic Description

Paleocene Volcanic Undifferentiated Granite

Maastrichtian Lafia Formation It consists of ferrogunized sandstones, red, loose sands, flaggy mudstones, clays and claystones

Santonian Unconformity Unconformity

Coniacian Awgu Formation It consists of bluish-grey to dark-black carbonaceous shales, calcareous shales, shaley limestones,

limestones, sandstones, siltstones, and coal seams

104 Okonkwo Austin Chukwuemeka: A Re-Appraisal of Groundwater Quality in Parts of Central Benue Trough, Nigeria

Geologic Age Formation Lithologic Description

Turonian

Ezeaku/Makurdi Formation It mainly consists calcareous shales, micaceous fine to medium friable sandstones and beds of

limestones which are in places shelly

Keana Formation cross-beded coarse-grained feldsparthic sandstones occasional conglomerates, and bands of shales

and limestones towards the top

Cenomanian Awe Formation Flaggy, whitish, medium to coarse grained, carlcarous sandstone, carboneaceous shales and clays

Mid-Late Albian Asu River Formation Comprises mainly limestones, shales, micaceous siltstones mudstones and clays

BASEMENT COMPLEX

Hydrogeologically, the area is underlain by the following

potential aquifers, namely: the interbedded sandstones of

Awe Formation, Basal sandstones of the Lafia Formation,

sandstones of the Awgu Formation and the sandstones of the

Makurdi and Ezeaku Formations (Offordile, 2000). Of all the

potential aquifers mentioned above, the Makurdi Formation,

together with its equivalent Ezeaku, appears most important.

The sandstones are lenticular at the base of the formation and

overlie the calcareous Awgu Formation (Figure 2). They are

generally whitish to brownish, fine to coarse grained friable,

friable, ferrugenized and feldspartic and about 10m thick.

The sandstones are also highly permeable and where in

contact with the less permeable, older, Awgu Formation

yields several springs.

Groundwater disposition and flow direction is aptly

described (Figure 3). Predominant flow direction is towards

the southeastern, west of the keana anticline. A groundwater

divide running roughly NE – SW, cause the groundwater of

the basal sandstones flow NW –SE directions.

Figure 2. Geology of the Middle Benue Valley (Source: Offodile, 2000).


Figure 3

Table 2. Physico-chemical characteristics of Natural water in some parts of Central Benue Trough (Source: Offodile, 1976). Values in parts

S/No Location

1 River Ome, Paint N.E. Keana. HDW 1

2 Agwantashi Market. HDW 2

3 Well, Front of Chief’s house. HDW 3

4 Dedere Market. HDW 4

5 Akarekwu Market. HDW 5

6 Well behind Min. of Natural Resources, Lafia.

7 Akwunza Junction Lafia. HDW 7


9 Kadarko. HDW 9

10 Agyaragu. HDW 10

11 Sabo Urme Lafia. HDW 11

12 River Ome, Paint W. of Keana. HDW 12

13 Lafia Division (Asakio) HDW 13

14 Udei Town. HDW 14

15 Udei Railway Station

16 Obi Town HDW 14

17 Agaza Town HDW 17

18 Well at Giza HDW 18

19 Adudu. HDW 19

International Journal of Advanced Materials Research Vol. 1, No. 3, 2015, pp. 102

Figure 3. Water Table Contours in Lafia-Keana Area.

chemical characteristics of Natural water in some parts of Central Benue Trough (Source: Offodile, 1976). Values in parts

pH Temp oC Na+ k+ Ca2+ Mg

7.1 28 30.00 10.00 15.22 6.30

7.3 28 40.00 18.00 44.04 3.80

7.3 28 5.00 56.00 69.67 24.00

6.60 28.2 10.00 40.00 28.83 16.00

4.7 28.5 3.00 6.00 10.41 6.50

Well behind Min. of Natural Resources, Lafia. 6.6 27 2.00 2.00 6.90 0.25

7.0 28 33.00 11.00 65.70 9.50

5.7 27 3.00 4.00 4.00 5.00

6.70 27.5 3.00 6.00 16.00 6.00

7.00 27.5 7.00 12.50 29.00 14.30

6.80 30 44.00 11.00 35.20 2.90

6.85 28 7.00 8.00 4.81 4.50

7.50 - 33.00 16.00 108.90 4.45

7.60 27.5 17.00 5.00 5.60 1.30

6.35 28 7.00 2.00 4.40 0.30

6.3 28 0.20 3.40 5.61 0.50

7.7 28 128.00 11.00 63.26 22.00

7.6 28.5 130.00 3.40 48.45 24.30

8.20 28.5 53.00 100.00 181.38 50.00

102-112 105

chemical characteristics of Natural water in some parts of Central Benue Trough (Source: Offodile, 1976). Values in parts per million (ppm).

Mg2+ -3HCO Cl-

2-4SO

6.30 69.60 58.00 4.39

3.80 24.40 28.00 4.96

24.00 152.00 135.00 18.65

16.00 156.00 40.00 12.10

6.50 38.00 21.00 6.59

0.25 24.00 4.00 0.30

9.50 129.00 28.20 122.80

5.00 14.80 4.00 4.40

6.00 40.00 5.80 4.10

14.30 150.00 10.00 4.92

2.90 72.00 12.00 121.80

4.50 37.00 11.00 6.00

4.45 308.00 38.00 41.60

1.30 45.00 3.00 4.11

0.30 16.00 5.00 5.00

0.50 24.00 3.00 3.60

22.00 274.00 10.00 280.00

24.30 512.00 20.00 25.24

50.00 164.00 180.00 516.00


3. Methodology

A total of 19 (Nineteen) groundwater samples were collected

from different locations in the study area, for the re-appraisal

of the groundwater quality. All water samples are from Hand-

Dug Wells (HDW). The groundwater samples were collected

into sterilized polyethylene bottles. The water samples were

transferred to the laboratory for physical and chemical

analyses. The pH meter was used to determine the pH values

while the Atomic Absorption Spectrophotometer (AAS) and

Titration methods were used to determine the concentration

of Calcium, Magnesium, Potassium, Sodium, Bicarbonate

and Chloride ion (Table 2). The values were expressed in

parts per million (ppm). They were converted to milligram

per litre (Mg/L) for the purpose of other water quality

characterization (Table 3) using the relation (equation 1).

Mg/L = Density x ppm (1)

(Houlsow, 1995)

The cations Na2+

, and Mg2+

from all the analyzed water

samples have been used to determine the Sodium Absorption

Ratio (SAR) as parameter in classifying water for irrigation

purposes (Etu-Efeotor, 1981), according to the equation 2

12 2 2

2

NaSAR

Ca Mg

+

+ += +

(2)

with all the cations calculated in milliequivalent (meq/L)

Table 5.

Table 3. Physico-chemical characteristics of Natural water in some parts of Central Benue Trough. Values of Ionic species in Milligram per litre (Mg/L).

S/No Location pH

Temp oC

EC µs/cm TDS Na+

k+ Ca

2+ Mg

2+

-3HCO Cl

-

2-4SO

-3NO

TH

1 River Ome, Paint N.E. keana HDW 1

7.1 28 357.00 754.80 29.10 8.60 23.59 10.76 462.14 186.18 34.19 103.91

2 Agwantashi Market

HDW 2 7.3 28 604.00 419.70 38.80 15.48 68.26 6.61 162.02 89.88 38.64 197.75

3 Well, front of chief’s

house HDW 3 7.3 28 1027.00 1790.70 4.85 48.16 107.98 41.76 1009.28 433.35 145.28 441.17

4 Dedere Market.

HDW 4 6.6 28.2 653.00 1402.70 9.70 62.00 44.68 27.84 1035.84 128.40 94.26 225.84

5 Akarekwu Market.

HDW 5 4.7 28.5 200.00 406.60 2.91 5.16 16.14 11.31 252.32 67.41 51.34 86.72

6

Well behind Min. of

Natural Resources,

Lafia. HDW 6

6.6 27 69.00 189.30 1.94 1.72 10.69 0.47 159.36 12.84 2.34 28.53

7 Akwunza Junction

Lafia. HDW 7 7.0 28 807.00 2063.5 32.01 9.46 11.84 16.53 856.56 90.52 956.61 322.37


5.7 27 125.00 166.60 2.91 3.44 6.20 8.70 98.27 12.84 34.27 51.17

9 Kadarko. HDW 9 6.70 27.5 302.00 358.50 2.91 5.16 24.80 18.44 265.60 18.62 31.94 137.60

10 Agyaragu. HDW 10 7.00 27.5 487.00 1153.80 6.79 10.76 44.95 24.88 996.00 32.10 38.33 214.38

11 Sabo Urme Lafia.

HDW 11 6.80 30 524.00 1577.2 42.68 9.46 54.56 5.05 478.08 38.52 948.82 157.11

12 River Ome, Paint W.

of Keana. HDW 12 6.85 28 149.00 356.70 6.79 6.88 7.46 7.83 245.68 35.31 46.74 50.75

13 Lafia Division

(Asakio) HDW 13 7.50 - 1080.00 2713.50 32.01 13.76 168.80 7.74 2045.12 121.98 324.06 453.73

14 Udei town. HDW 14 7.60 27.5 145.00 372.20 16.49 4.30 8.68 2.26 298.80 9.63 32.02 30.97

15 Udei Railway Station. HDW 15

6.35 28 72.00 177.10 6.79 1.72 6.82 0.52 106.24 16.05 38.95 19.18

16 Obi Town. HDW 16 6.3 28 124.00 217.70 0.19 2.92 8.69 8.87 159.36 9.63 28.04 58.09

17 Agaza Town. HDW

17 7.7 28 1368.00 4302.60 124.16 9.46 98.05 38.28 1819.36 32.10 2181.20 402.07

18 Well at Giza. HDW

18 7.6 28.5 1279.00 3906.9 126.10 2.92 75.09 42.28 3399.68 64.20 196.62 361.07

19 Adudu. HDW 19 8.20 28.5 2563.00 6192.00 51.41 86.00 281.14 87.00 1088.96 577.80 4019.64 1059.55

Average 6.88 30 628.15 1501 28.34 16.17 60.96 19.33 786.24 104.07 486.48 231.68


Table 4. Ionic species expressed in milli equivalent per litre (Meq/L) and Ionic Balance in the Study Area.

S/No Location Na+ k+ Ca2+ Mg2+ -3HCO Cl-

2-4SO

Ion Balance

(Cation/Anion)%


1.27 0.22 1.18 0.90 7.57 5.25 0.71 0.3

2 Agwantashi Market. HDW 2 1.69 0.40 3.41 0.54 2.66 2.54 0.80 1.0


0.21 1.23 5.39 3.44 16.54 12.22 3.02 0.3

4 Dedere Market. HDW 4 0.42 1.59 2.23 2.29 16.98 3.62 1.96 0.3

5 Akarekwu Market. HDW 5 0.13 0.13 0.81 0.93 4.14 1.90 1.07 0.3

6 Well behind Min. of Natural

Resources, Lafia. HDW 6 0.08 0.04 0.53 0.04 2.61 0.36 0.05 0.2

7 Akwunza Junction Lafia. HDW 7 1.39 0.24 5.08 1.36 14.04 2.55 19.92 0.2

8 Akwunza Junction Lafia. HDW 8 0.13 0.09 0.31 0.72 1.61 0.36 0.75 0.5

9 Kadarko. HDW 9 0.13 0.13 1.24 1.52 4.21 0.53 0.66 0.6

10 Agyaragu. HDW 10 0.30 0.28 2.24 2.05 16.32 0.91 0.80 0.3

11 Sabo Urme Lafia. HDW 11 1.86 0.24 2.72 0.42 7.84 1.09 19.75 0.2

12 River Ome, Paint W. of Keana.

HDW 12 0.30 0.18 0.37 0.64 4.03 1.00 0.97 0.2

13 Lafia Division (Asakio). HDW

13 1.39 0.35 8.42 0.64 33.52 3.44 6.75 0.2

14 Udei Town. HDW 14 0.72 0.11 0.43 0.19 4.90 0.27 0.67 0.2

15 Udei Railway Station. HDW 15 0.30 0.04 0.34 0.04 1.74 0.45 0.81 0.2

16 Obi Town. HDW 16 0.01 0.07 0.43 0.73 2.61 0.27 0.58 0.4

17 Agaza Town. HDW 17 5.40 0.24 4.89 3.15 29.82 0.91 45.41 0.2

18 Well at Giza. HDW 18 5.49 0.07 3.75 3.48 55.72 1.81 4.09 0.2

19 Adudu. HDW 19 2.24 2.20 14.03 7.16 17.85 16.30 83.69 0.2

Table 5. Sodium Absorption Ratio (SAR) of water samples in the study area.

S/No Location/Handdugged Well No. SAR calculated Water classification

1 River Ome, Paint N.E. Keana. HDW 1 1.24 Excellent

2 Agwantashi Market. HDW 2 1.20 Excellent

3 Well, Front of Chief’s house. HDW 3 0.09 Excellent

4 Dedere Market. HDW 4 0.27 Excellent

5 Akarekwu Market. HDW 5 0.13 Excellent

6 Well behind Min. of Natural Resources, Lafia. HDW 6 0.14 Excellent

7 Akwunza Junction Lafia. HDW 7 0.77 “

8 Akwunza Junction Lafia, HDW 8 0.18 “

9 Kadarko. HDW 9 0.11 “

10 Agyaragu. HDW 10 0.20 “

11 Sabo Urme Lafia. HDW 11 1.48 “

12 River Ome, Paint W. of Keana. HDW 12 0.42 “

13 LAfia Division (Asakio). HDW 13 0.65 “

14 Udei Town. HDW 14 1.29 “

15 Udei Railway Station. HDW 15 0.68 “

16 Obi Town. HDW 16 0.01 “

17 Agaza Town. HDW 17 2.69 “

18 Well at Giza. HDW 18 2.88 “

19 Adudu. HDW 19 0.68 “

4. Results of Geochemical Studies

Table 3 shows the results of the geochemical analysis of the

waters. pH values range from 4.7 to 8.2. This can be

described as mildly acidic to alkaline. Presence of carbonate

is suspected at HDW 19 because pH

of 8.2 and above possibly

indicates carbonate presence (Oteze, 1991). Temperature (oC)

ranges from 27oC to 30

oC with average of 30

oC. This could

be described as high in all the HDWs.

Adudu, HDW 19 shows very high total dissolved solids

(TDS) value of 6192mg/L which corresponds to the high

electrical Conductivity (EC) value of 2563µs/cm. other high

EC values occur in HDW 18, HDW 17, HDW 13, HDW 11,

HDW 10, HDW 7, HDW 4 and HDW 3. The lowest EC

value is found at the HDW 15 as 177.10µs/cm.


Sodium (Na+) concentration ranges from 0.19mg/L in HDW 16 to 126.10mg/L in HDW 18 with of 28.34mg/L.

Table 6. Ionic Species in the Study Area expressed in molarity (Mol).

S/No Location Na+ K+ Ca2+ Mg2+ -3HCO Cl- 2-

4SO

1 River Ome, Paint N.E. Keana. HDW 1 0.00126 0.00022 0.00058 0.00045 0.00757 0.00524 0.00035

2 Agwantashi Market. HDW 2 0.00168 0.00039 0.00170 0.00027 0.00265 0.00253 0.00040

3 Well, Front of Chief’s house. HDW 3 0.00021 0.00123 0.00269 0.00174 0.01654 0.01220 0.00151

4 Dedere Market. HDW 4 0.00042 0.00158 0.00111 0.00116 0.01698 0.00361 0.00098

5 Akarekwu Market. HDW 5 0.00012 0.00013 0.00040 0.00047 0.00413 0.00189 0.00053

6 Well behind Min. of Natural Resources, Lafia.

HDW 6 0.00008 0.00004 0.00026 0.00002 0.00261 0.00036 0.00002

7 Akwunza Junction Lafia. HDW 7 0.00139 0.00024 0.00254 0.00068 0.01404 0.00254 0.00996

8 Akwunza Junction Lafia, HDW 8 0.00012 0.00008 0.00015 0.00036 0.00161 0.00036 0.00035

9 Kadarko. HDW 9 0.00012 0.00013 0.00062 0.00076 0.00435 0.00052 0.00033

10 Agyaragu. HDW 10 0.00029 0.00027 0.00112 0.00103 0.01632 0.0090 0.00039

11 Sabo Urme Lafia. HDW 11 0.00185 0.00024 0.00136 0.00021 0.00783 0.00108 0.00988

12 River Ome, Paint W. of Keana. HDW 12 0.00029 0.00017 0.00018 0.00032 0.00402 0.00099 0.00048

13 LAfia Division (Asakio). HDW 13 0.00139 0.00035 0.00422 0.00032 0.03352 0.00343 0.00337

14 Udei Town. HDW 14 0.00071 0.00011 0.00021 0.00009 0.00489 0.00027 0.00033

15 Udei Railway Station. HDW 15 0.00029 0.00004 0.00017 0.00002 0.00174 0.00045 0.00040

16 Obi Town. HDW 16 0.00001 0.00007 0.00021 0.00036 0.00261 0.00027 0.00029

17 Agaza Town. HDW 17 0.00539 0.00024 0.00245 0.00159 0.02982 0.00090 0.02272

18 Well at Giza. HDW 18 0.00548 0.00007 0.00187 0.00176 0.05573 0.00180 0.00204

19 Adudu. HDW 19 0.00222 0.00220 0.00702 0.00362 0.01785 0.01627 0.04187

Table 7. Values of Calcite Saturation Index in the Study Area.

S/No Location Ionic Strength Kiap/Ksp S.I. Calcite Remarks

1 River Ome, Paint N.E. Keana. HDW 1 0.0099 10-1.53 0.03 Under saturated

2 Agwantashi Market. HDW 2 0.0083 10-0.18 0.70 Slightly under saturated

3 Well, Front of Chief’s house. HDW 3 0.0269 10+0.78 6.02 Over saturated

4 Dedere Market. HDW 4 0.0096 10-0.08 0.83 Slightly under saturated

5 Akarekwu Market. HDW 5 0.0059 10-3.19 0.0006 Very under saturated

6 Well behind Min. of Natural Resources, Lafia. HDW 6 0.0021 10-1.62 0.02 Under saturated

7 Akwunza Junction Lafia. HDW 7 0.0354 10+0.26 1.81 Over saturated

8 Akwunza Junction Lafia, HDW 8 0.0003 10-2.90 0.001 Very under saturated

9 Kadarko. HDW 9 0.0059 10-1.88 0.01 Under saturated

10 Agyaragu. HDW 10 0.0133 10+0.19 1.54 Over saturated

11 Sabo Urme Lafia. HDW 11 0.0135 10-0.36 0.43 Under saturated

12 River Ome, Paint W. of Keana. HDW 12 0.0046 10-1.38 0.04 Under saturated

13 LAfia Division (Asakio). HDW 13 0.0351 10+1.35 22.38 Over saturated

14 Udei Town. HDW 14 0.0042 10-0.48 0.33 Under saturated

15 Udei Railway Station. HDW 15 0.0024 10-2.24 0.005 Very under saturated

16 Obi Town. HDW 16 0.0034 10-2.04 0.009 Very under saturated

17 Agaza Town. HDW 17 0.0716 10+1.15 14.22 Over saturated

18 Well at Giza. HDW 18 0.0428 10+1.29 19.61 Over saturated

19 Adudu. HDW 19 0.1242 10+1.79 62.83 Over saturated


Table 8. Water Classification based on Sodium Absorption Ratio (SAR).

(Source: Etu-Efeofor, 1981).

SAR Water classification

0 – 10 Excellent

10 – 18 Good

18 – 26 Fair

>26 Poor

Table 9. Water classification based on Total Hardness as CaCo3. (Source:

Hem, 1970).

Hardness, Mg/L as CaCo3 Class of water

0 – 60 Soft

61 – 120 Moderately hard

121 – 180 Hard

>180 Very hard

Calcium (Ca2+

) values range from 6.20mg/L at HDW 8 to

281mg/L at HDW 19. Calcium is a major contributor to the

hardness of water (Ozoko, 2004). High Ca2+

values in HDW

19 may be due to dissolution of clay material in sandstones

of Lafia Formation. Magnesium (Mg2+

) values range from

0.44mg/L at HDW 6 to 87mg/L at HDW 19 with an average

of 19.33 mg/L. The general low concentration of Mg2+

may

be attributed to the fact that dolomite contribute is absent in

the area.

Bicarbonate ( 3HCO−) values are generally high in most

locations sampled. It ranges from 3399.68mg/L at HDW 18

to 106.24mg/L at HDW 15 with an average of 786.24mg/L.

Possible sources of sulphate in the HDW may not be

anthropogenic but may be referred as a result of calcite

reduction in the waters.

Sulphate ion (2

4SO −) is very high in Adudu HDW 19 with a

value of 4019.64mg/L. Others are at HDW 17, HDW 13,

HDW 11, HDW 7. The high concentration in these HDW

may be due to the contact of the underlying coaly Awgu

Formation.

Chloride ion (Cl-) values range from 9.63mg/L in HDW 14

and HDW 16 to 577.80mg/L in HDW 19. The reason for the

high chloride concentration may be not clear.

The Total Hardness of all the investigated water samples as

CaCo3 was determined using the following relation (equation

3) Hem (1970).

TH 2.5Ca2+ + 4.1Mg2+ (3)

On this basis, 75% of the waters can be described as very

hard, 15% are described as soft water while 10% can be

described as moderately hard.

The SAR calculated range from 0.01 to 2.88 in all location

(HDW) and are classified as excellent for irrigation purposes.

5. Classification of Groundwater

It is important to classify the entire waters so as to obtain the

broad groupings. The basis of the classification here is the

major ion percent ages (Table 10). The groupings are also

confirmed by using the piper’s trilinear diagram (Fig. 4a, b).

The basic deduction is that Hand dug well water are mainly

calcium – bicarbonate type of groundwater in which calcium

(Ca2+

) and bicarbonate 3( )HCO− are the dominant ions.

6. Calcite Saturation Analysis

Equilibrium calculation can provide information on whether

a mineral or gas will dissolve or precipitate in a particular

aqueous environment. In addition to providing information

on saturation indices, these calculations can define masses of

elements that may not have been directly analyzed. The

relevant equations employed in such calculations are found in

the works of Freeze and Cherry (1979), Knobel and Philips

(1988) and Hem (1989).

Equilibrium calculations are useful in predicting calcite

saturation in groundwater systems. Information on calcite

saturation is particularly necessary because calcite is one of

the commonest minerals in aquifers and to an extent

predicting its contribution to Borehole failure geochemically.

When the saturation indices (S.I) are greater than unity, super

saturation is indicated but S.I. values of less than unity show

under saturation. An S.I. value of unity (1) means the water is

in equilibrium with the calcite.

Table 7 shows the values of calcite saturation index in the

Study Area. Two locations; HDW 2 and HDW 4 with S.I.

values of 0.70 and 0.83 respectively indicate closeness to

calcite equilibrium when approximated. While HDW 1,

HDW 5, HDW 6, HDW 8, HDW 9, HDW 11, HDW 12,

HDW 14, HDW 15, and HDW 16 are under saturated with

respect to calcite. Locations strongly over saturated with

respect to calcite are HDW 3, HDW 7, HDW 10, HDW 13,

HDW 16, HDW 17 and HDW 19.

Calcite equilibrium is given as

�� ⇌ Ca�+ CO�

��

When the reaction proceeds to the right it indicates mineral

dissolution and S.I. is less than unity. While to the left

indicates mineral precipitation and S.I. is greater than unity.

Geochemical implications of Hand dug wells oversaturated

with respect to calcite is that, if surface pumps are installed,

110 Okonkwo Austin Chukwuemeka: A Re

there may be tendency of scaling on the wal

connected to the pump. This conclusion was based on the

analytical approach used.

7. Conclusions

In all the sampled and the analytical approach utilized, the

Table 10. Classification of the Natural

S/No Location/Hand dugged well No


2 Agwantashi Market. HDW 2


4 Dedere Market. HDW 4

5 Akarekwu Market. HDW 5

6 Well behind Min. of Natural Resources, Lafia. HDW 6


8 Akwunza Junction Lafia, HDW 8

9 Kadarko. HDW 9

10 Agyaragu. HDW 10

11 Sabo Urme Lafia. HDW 11

12 River Ome, Paint W. of Keana. HDW 12

13 LAfia Division (Asakio). HDW 13

14 Udei Town. HDW 14

15 Udei Railway Station. HDW 15

16 Obi Town. HDW 16

17 Agaza Town. HDW 17

18 Well at Giza. HDW 18

19 Adudu. HDW 19

Figure 4a. Hydrochemical Analysis Groundwater (Piper Trilinear Diagram)

Okonkwo Austin Chukwuemeka: A Re-Appraisal of Groundwater Quality in Parts of Central Benue Trough, Nigeria

aling on the walls of the pipe

connected to the pump. This conclusion was based on the

In all the sampled and the analytical approach utilized, the

elemental concentration were compared with WHO standard

limits for drinking water purpose. And ionic concentrations

in most of the Hand dug wells largely exceed the WHO limits,

therefore may not be portable for

be suitable for domestic use.

Classification of the Natural water system in the study area on the basis of their major ion percentages

Major Cation Type Major Anion Type

No dominant type HCO

Ca2+ type No dominant type

Ca2+ type HCO



Well behind Min. of Natural Resources, Lafia. HDW 6 Ca2+ type HCO

Ca2+ type SO

Mg2+ type HCO

Mg2+ type HCO


Ca2+ type SO

River Ome, Paint W. of Keana. HDW 12 No dominant type HCO

Ca2+ type HCO

Na+ or k+ type HCO


Mg2+ type HCO

Ca2+ type HCO

Ca2+ type HCO

Ca2+ type SO

Hydrochemical Analysis Groundwater (Piper Trilinear Diagram).

of Central Benue Trough, Nigeria

elemental concentration were compared with WHO standard

urpose. And ionic concentrations

in most of the Hand dug wells largely exceed the WHO limits,

table for drinking purposes but may

water system in the study area on the basis of their major ion percentages.

Major Anion Type

3HCO

− type

No dominant type

3HCO

− type

3HCO

− type

3HCO

− type

3HCO

− type 2

4SO

− type

3HCO

− type

3HCO

− type

3HCO

− type 2

4SO

− type

3HCO

− type

3HCO

− type

3HCO

− type

3HCO

− type

3HCO

− type

3HCO

− type

3HCO

− type 2

4SO

− type


Figure 4b. Hydrochemical Analysis Groundwater (Piper Trilinear Diagram)

However, they are excellent for irrigation purposes (Table 5).

Offodile (1976) had classified the waters in these areas as

medium mineralized because the wells are near the boundary

of the Lafia and Coaly Awgu Formations, where water from

the two formations appear to mix.

The natural groundwater in the study areas bel

−+ −3

2 HCOCa type. The quality of any groundwater is due to

the mineralogic composition of the aquifer. Rock water

reaction helps to define the geochemical environment within

an aquifer. An environment may be acidic or reducing or may

change from acidic to reducing within the same aquifer

thereby producing a complex hydrochemical framework

(Ozoko, 2004).

The pH range (4.7 – 8.20) shows acidic through neutral to

moderate alkaline. The high sulphate ion ( )

may be attributed to the mixing of water from the underlying

coaly Awgu formation.

Finally, general study of the cation concentrations shows that

calcium is a more significant contributor to the water

hardness than magnesium.

Recommendation

The hand dug wells in the study area should

International Journal of Advanced Materials Research Vol. 1, No. 3, 2015, pp. 102

Hydrochemical Analysis Groundwater (Piper Trilinear Diagram).

However, they are excellent for irrigation purposes (Table 5).

Offodile (1976) had classified the waters in these areas as

medium mineralized because the wells are near the boundary

of the Lafia and Coaly Awgu Formations, where water from

The natural groundwater in the study areas belongs to

type. The quality of any groundwater is due to

the mineralogic composition of the aquifer. Rock water

reaction helps to define the geochemical environment within

an aquifer. An environment may be acidic or reducing or may

nge from acidic to reducing within the same aquifer

thereby producing a complex hydrochemical framework

8.20) shows acidic through neutral to 2

4( )SO −in the wells

may be attributed to the mixing of water from the underlying

Finally, general study of the cation concentrations shows that

calcium is a more significant contributor to the water

wells in the study area should be properly

treated to reduce its hardness properties to increase its

portability for domestic use. Pipes of installed pumps should

be checked often to avoid s

oversaturation with respect to calcite.

References

[1] Etu-Efeotor, J.O., 1981. Preliminary hydrogeochemical investigations of the sub-surface waters in parts of the Niger Delta. Journ. Min. Geol. Vol. 18. No. 1. P. 103

[2] Freeze, R.A. and Cherry, J.A., 1979. Groundwater. Prentice Hall, Inc. New Jersey.

[3] Houlsow, A.W., 1995. Water Quality: Data Analysis and interpretation. Lewis Publishers, Flordia. 386p.

[4] Hein, J.D., 1970. Study and Interpretation of Chemical characteristics of natural waters. Water supply papers. Publication of U.S. Geological1473, p. 254 – 255.

[5] Hein, J.D., 1989. Study and Interpretation of the Chemical Characteristics of natural waters. 4Water – Supply paper 2254.

[6] Knobel, L.L., and Philips, S.W., 1988. Aqueous geochemistof the Magothy Aquifer, Maryland. U.S. Geol. Surv. Paper 2323.

[7] Nwajide, C.S., 1990. Sedimentation and Paleogeography of the Central Benue Trough, Nigeria, in C.O. Ofoegbu, edition. The Benue Trough Structure and Evolution. Viewer Braunschwaig, p. 19 – 38.

102-112 111

treated to reduce its hardness properties to increase its

Pipes of installed pumps should

be checked often to avoid scaling as a result of the

oversaturation with respect to calcite.

Efeotor, J.O., 1981. Preliminary hydrogeochemical surface waters in parts of the Niger

Delta. Journ. Min. Geol. Vol. 18. No. 1. P. 103 – 105.

Freeze, R.A. and Cherry, J.A., 1979. Groundwater. Prentice –

Houlsow, A.W., 1995. Water Quality: Data Analysis and interpretation. Lewis Publishers, Flordia. 386p.

Hein, J.D., 1970. Study and Interpretation of Chemical characteristics of natural waters. Water supply papers. Publication of U.S. Geological survey, Washington DC. No.

Hein, J.D., 1989. Study and Interpretation of the Chemical Characteristics of natural waters. 4th Edition. U.S. Geol. Surv.

Knobel, L.L., and Philips, S.W., 1988. Aqueous geochemistry of the Magothy Aquifer, Maryland. U.S. Geol. Surv. Paper

Nwajide, C.S., 1990. Sedimentation and Paleogeography of the Central Benue Trough, Nigeria, in C.O. Ofoegbu, edition. The Benue Trough Structure and Evolution. Viewer


[8] Offodile, M.E., 1976. The Geology of the Middle Benue of Nigeria. University of Uppasala, Paleo. Inst., Special Vol. 4 p. 146 – 160.

[9] Offodile, M.E. 2000. Groundwater Study and Development in Nigeria. Mecon Geology & Eng. Services Ltd. 453p.

[10] Oteze, G.E., 1991. Portability of Groundwater from the Rima Group in the Sokoto Basin. Nigeria. Journ. Min. and Geology. Vol. 27. No. 1. p. 17 – 23.

[11] Ojoh, K.A., 1992. The southern part of the Benue, Trough (Nigeria) cretaceous stratigraphy, Basin Analysis, Paleo-oceanography and geodynamic evaluation in the equatorial domain of the South Atlantic: NAPE Bulletin. Vol. 7. No. 2. p. 131 – 152.

[12] Obaje, N.G., Ulu, O.K. and Petters, S.W., 1999. Biostratigraphic and geochemical controls of hydrogcarbon prospects in the Benue Trough and the Anambra Basin, Nigeria. NAPE Bulletin, Vol. 14. No. 1. p. 18 – 54.

[13] Ozoko, D.C., 2004. Geochemical and Microbial Studies of the natural water system in Agila, Benue State, Nigeria. NAH water resources Jour. Vol. 15, No. 2. p. 60 – 64.

[14] Petters, S.W. and Ekweozor, C.M., 1982. Origin of Mid-cretaceous black shales in the Benue Trough, Nigeria. Paleogeography, Paleoclimatology, Paleoecology, vol. 40, p. 311 – 319.

[15] Stednick, J.D., 1991. Wildland Water Quality Sampling and Analysis. Academic Press Inc. San Daigo, 216p.

a re-appraisal of groundwater quality in parts of central...

Documents