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Ciência Rural

Print version ISSN 0103-8478

Cienc. Rural vol.44 no.7 Santa Maria July 2014

https://doi.org/10.1590/0103-8478cr20130712 

Rural Engineering

Assessing groundwater stoichiometric composition and its suitability in Northwestern Bangladesh

Avaliação de lençol de água quanto a composição estioquiométrica e a sua conveniência do Noroeste do Bangladesh

Jahidul Islam I  

Abdul Hakim I   II  * 

Mohamed Musa Hanafi III  

Abdul Shukor Juraimi III  

Ratna Rani Sarkar I  

AKM Mosharof Hossain IV  

Indira Chowdhury I  

Jafor Ali I  

Abul Kashem V  

(I)Department of Agricultural Chemistry, Hajee Mohammad Danesh Science and Technology University, Dinajpur-5200, Bangladesh.

(II)Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia. E-mail: ahakimupm@gmail.com.

(III)Department of Crop Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia.

(IV)Department of Soil Science, Hajee Mohammad Danesh Science and Technology University, Dinajpur-5200, Bangladesh.

(V)Bangladesh Institute of Nuclear Agriculture, Mymensingh, Bangladesh.


ABSTRACT

Groundwater quality analyses included pH, EC, cations (Ca2+, Mg2+, Na+, K+, Zn2+, Cu2+, Mn2+, Fe3+ and As3+), anions (CO32-, HCO3-, NO3-, SO42-, PO43- and Cl-) and TDS of northwestern Bangladesh. The samples contained Ca2+, Mg2+ and Na+ as the dominant cations and HCO3- and Cl- were the dominant anions. Ratios of major cations and anions of water samples suggest the predominance of Ca and Mg-containing minerals over Na-containing minerals. According to TDS and SAR values, all samples were classed as 'freshwater' and 'excellent' categories. The SSP of all waters was under 'excellent' and 'good' classes. All samples were within 'soft' class regarding hardness with 'suitable' RSC. Based on As3+, Zn2+, Mn2+, Fe3+, SO42-, NO3- and Cl- all groundwater samples were within the 'safe' limit for drinking but unsuitable for some industries for specific ions.

Key words: groundwater; suitability; northwestern Bangladesh

RESUMO

As análises de qualidade de Lençol de Água incluíram pH, EC, e os cations,(Ca2+, Mg2+, Na+, K+, Zn2+, Cu2+, Mn2+, Fe3+ e As3+), aníons ( CO32-, HCO3-, NO3-, SO42-, PO43- e Cl-e TDS do noroeste do Bangladesh. As amostras continham Ca2+, Mg2+ e Na+ e como o cations dominante HCO3- e Cl foram os aníons dominantes. Segundo o TDS e valores de SAR, todas as amostras foram classificadas como categorias 'de água doce' e 'excelentes'. O SSP de todas as águas foi nas classes 'excelentes' e 'boas'. Todas as amostras foram dentro da classe 'suave' quanto à dureza com RSC 'conveniente'. Baseado As3+, Zn2+, Mn2+, Fe3+, SO42-, NO3- e Cl- - todas as amostras de lençol de água foram dentro do limite 'seguro' como água de bebida mas impróprias para algumas indústrias que emprega íons específicos.

Palavras-Chave: lençol de água; conveniência; o Bangladesh do noroeste

INTRODUCTION

Groundwater resources support urban and rural communities in Bangladesh. As industrial and agricultural development of Bangladesh increases, the demand for water also steadily grows. Changes in groundwater quality are due to variation in climatic conditions, residence time of water, aquifer materials, and inputs from soil during percolation of water (KRISHNA KUMAR et al., 2009). Many hydrogeochemical processes have been highlighted in the control of the chemical composition of groundwater like carbonates and silicates weathering, and ion exchange (KRISHNA KUMAR et al., 2009; SUBBA RAO, 2008).

Groundwater contains a variety of chemical constituents at different concentrations. The greater part of the soluble constituents in groundwater comes from soluble minerals in soils and sedimentary rocks (WANTM, 2005). A much smaller part has its origin in the atmosphere and surface water bodies. For most groundwaters, 95% of the ions are represented by only a few major ionic species: the positively charged cations sodium (Na+), potassium (K+), calcium (Ca2+) and magnesium (Mg2+), and the negatively charged anions chloride (Cl-), sulfate (SO4 2-), bicarbonate (HCO3 -) and nitrate (NO3 -). TODD & MAYS (2005) suggested that, among the many ions which might be considered important as related to groundwater quality, Cl-, Fe3+, SO4 2-, NO3 -, Mn2+, pH, TDS and hardness are the important chemical constituents to assess the suitability of water for industrial purposes. Therefore, the objective of the present research was to examine the concentrations of selected dissolved ions in groundwater and classify the waters according to their suitability for irrigation, drinking and industrial uses.

MATERIAL AND METHODS

Water sampling and analysis

Well water samples were collected in March and April 2012. Our sampling sites were 14 shallow tubewells, 15 hand tubewells and 15 deep tubewells. Samples were collected in two liter plastic bottles that had been cleaned with hydrochloric acid (1:1) and then rinsed with distilled water. Before collecting each sample, bottles were rinsed 3 to 4 times with sample. All reagents used in chemical analysis were of analytical grade. Samples were analyzed in Department of Agricultural Chemistry, Hajee Mohammad Danesh Science and Technology University, Dinajpur. For assessing the suitability classes for irrigation, domestic and industrial uses, we measured pH, EC, TDS, Ca2+, Mg2+, Na+, K+, Zn2+, Cu2+, Mn2+, Fe3+, PO4 3-, As3+, CO3 2-, HCO3 -, SO4 2-, NO3 - and Cl-All measured by the method of APHA, 1998 in the Soil Resources Development Institute, Dinajpur, Bangladesh. The ion-balance-error was computed, taking the relationship between the total cations (Ca2+, Mg2+, Na+ and K+) and the total anions (HCO3 -, Cl-, SO4 2-) for each set of complete analysis of water samples. Only samples which fall within ±5% were reported in this work.

Equations used in calculating water class rating parameters

The following formulae related to the irrigation water classes rating were used to classify water samples using the chemical data.

a) Sodium Adsorption Ratio (SAR),

b)Soluble Sodium Percentage (SSP),

c) Residual Sodium Carbonate (RSC) , RSC = (CO3 2- + HCO3 -) - (Ca2+ + Mg2+)

d) Hardness or Total Hardness (HT), HT = 2.5 × Ca2+ + 4.1 × Mg2+

e) Potential Salinity (PS) = Cl- + (SO4 2-/2)

f) Permeabili ty index

RESULTS

Chemical composition of water samples

Some summary results from our survey of groundwater are shown in tables 2A and 2B. Details of the sampling sites are presented in table 1. Groundwater pH is a fundamental property that describes the acidity and alkalinity and largely controls the amount and chemical form of many organic and inorganic substances dissolved in groundwater. The pH of samples ranged from 5.4 to 5.9 (Table 2A). The EC and TDS ranged from 160 to 460 µS/cm and 95 to 287 mg/L, respectively. Concentrations of Na+ and K+ ranged from 0.36 to 1.17 meq/L and 0.17 to 0.48 meq/L, respectively. K+ concentrations were generally lower than Na+ concentrations. Ca2+ and Mg2+ were major cations in groundwater and ranged from 0.64 to 2.32 meq/L and 1.05 to 3.81 meq/L, respectively. NO3 - and SO4 2- concentrations were 0.10 to 1.65 mg/L and 0.007 to 0.096 meq/L, respectively. An appreciable amount of HCO3 - was present in all water samples, though CO3 2- was negligible in most cases. The range for HCO3 - were 1.50 to 3.48 meq/L while Cl- concentrations ranged from 0.65 to 2.25 meq/L. The order of the relative abundance of major cations, expressed in percent of meq/L, was Mg2+(47.52%) > Ca2+(30.63%) > Na+(15.22%) > K+(6.64%) while that of the anions was HCO3 -(63.13%) > Cl-(35.83%) > SO4 2-(1.04%). The concentration of earth alkalis elements (Ca and Mg) represents 78.15% of total cations; this shows a high rock/water interaction in dry season. Fe3+, Cu2+, Zn2+ and Mn2+ concentrations varied from 0.0006 to 1.31 mg/L, 0.072 to 0.21 mg/L, 0.0006 to 0.048 mg/L and 0.0017 to 2.02 mg/L, respectively (Table 2B). The computed variable, hardness, varied from 100 to 300 mg/L. The potential salinity and permeability index values ranged from 0.66 to 2.30 meq/L and 0.37 to 0.74, respectively (Table 2A).

Table 1- Information regarding of sampling sites of the Dinajpur Sadar Upazilla under the District of Dinajpur, Bangladesh; location, well type, depth, and the duration of use 

Sample No. -------------------------------Sampling sites------------------------------- Depth of sink (m) Well type Duration of uses (year)
Location Union (Small administrative unit)
1 Daksin Balubari Sadar 18 STW 10
2 Uttar Gobindapur Chehelgazi 23 STW 15
3 Uttar Mohespur Fazilpur 50 STW 12
4 Raniganj Fazilpur 60 STW 14
5 Godabari Sundarban 45 STW 20
6 Dighon Sekhpura 73 STW 22
7 Nayanpur Sadar 23 STW 14
8 Kismat Madhabpur Shashara 43 STW 9
9 Masimpur Auliapur 40 STW 15
10 Karimullapur Auliapur 45 STW 14
11 Daksin Gosaipur Uthrail 30 STW 20
12 Maligram Uthrail 43 STW 24
13 Mollapara Kamalpur 35 STW 17
14 Purba Mohonpur Shankarpur 40 STW 18
15 Pourashova Sadar 125 DTW 20
16 Daksinnagar Sekhpura 125 DTW 15
17 Uttar Bhabanipur Chehelgazi 125 DTW 17
18 Belbari Sundarban 125 DTW 20
19 North Fazilpur Fazilpur 110 DTW 14
20 Mahatulyapur Shashara 135 DTW 10
21 Kaugan Shashara 113 DTW 15
22 Mohabbatpur Auliapur 110 DTW 17
23 Saidpur Auliapur 85 DTW 20
24 Mohorampur Auliapur 110 DTW 14
25 Gauripur Askarpur 113 DTW 20
26 Daksin Gobindapur Askarpur 155 DTW 15
27 Ramchandrapur Uthrail 115 DTW 14
28 Daksin Bhabanipur Kamalpur 115 DTW 10
29 Shankarpur Shankarpur 125 DTW 18
30 Auliapur Auliapur 75 HTW 19
31 Daskin Auliapur Auliapur 70 HTW 15
32 Deotair Sekhpura 60 HTW 14
33 North Chehelgazi Chehelgazi 50 HTW 12
34 South Chehelgazi Chehelgazi 48 HTW 9
35 East Sundarban Sundarban 60 HTW 7
36 East Fazilpur Fazilpur 53 HTW 14
37 West Fazilpur Fazilpur 65 HTW 12
38 South Shashara Shashara 50 HTW 13
39 Daksin Sadipur Uthrail 30 HTW 14
40 East Shankarpur Shankarpur 45 HTW 10
41 Muradpur Uthrail 75 HTW 11
42 Jamalpur Askarpur 60 HTW 12
43 Baragram Kamalpur 62 HTW 14
44 West Shankarpur Shankarpur 20 HTW 8

STW=Shallow tubewell, DTW= Deep tubewell, HTW= Hand tubewell

Table 2 - A. pH, EC, TDS, hardness, potential salinity (PS), permeability index (PI) and anionic constituents of groundwater. B. Concentrations of cationic constituents of groundwater. C. Stoichiometric ratios of different major ions 

A pH EC TDS Hardness Cl- PS PI HCO3 - SO4 -2 NO3 - PO4 3-
μS /cm mg/L mg/L meq/L meq/L meq/L meq/L mg/L mg/L
Min 5.4 160 95 100 0.65 0.66 0.37 1.5 0.007 0.10 0.004
Max 5.9 460 287 300 2.25 2.30 0.74 3.48 0.096 1.65 0.275
Mean 5.6 280 171 177 1.40 1.42 0.56 2.46 0.040 0.57 0.057
SD 0.12 75 51 60 0.49 0.50 0.11 0.53 0.024 0.46 0.049
B --------Ca 2+-------- Mg 2+ Na + K + Cu 2+ Zn 2+ Mn 2+ Fe 3+ As 5+
meq/L meq/L meq/L meq/L mg/L mg/L mg/L mg/L mg/L
Min 0.64 1.05 0.36 0.17 0.072 0.0006 0.0017 0.0006 0.005
Max 2.32 3.81 1.13 0.48 0.21 0.05 2.02 1.31 0.032
Mean 1.40 2.18 0.70 0.30 0.14 0.02 0.26 0.06 0.018
SD 0.52 0.74 0.18 0.07 0.03 0.01 0.38 0.20 0.007
C
Ratios Min Max Mean SD
(Ca2++Mg2+)/Tcations 0.63 0.88 0.77 0.06
(Na++K+)/Tcations 0.12 0.36 0.23 0.06
Ca2+/Mg2+ 0.46 1.91 0.66 0.22
Na+/Ca2+ 0.20 1.08 0.55 0.21
Na+/(Na+ + Cl-) 0.19 0.51 0.34 0.34
HCO3 -/Na+ 1.92 7.42 3.70 3.69
(HCO3 - + SO4 2-)/Tanions 0.55 0.73 0.65 0.05
Cl-/Tanions 0.26 0.45 0.35 0.06

Stoichiometric relations

The Na-Cl relationship has often been used to identify the mechanisms for acquiring salinity and saline intrusions (JALALI, 2007). Most groundwater samples in this study had Na+:Cl- ratio lower than unity, while a few had Na+:Cl- ratio equal to one (Figure 1c). The weathering of silicates with carbonic acid (H2CO3) formed from interaction of atmospheric CO2 with water or CO2 coming from the decomposition of organic matter in the soil (SUBBA RAO, 2008), can be written as follows:(Na+, Mg2+, Ca2+, K+) silicates + H2O → H4SiO4 + HCO3 - + Na+ + Mg2+ + Ca2+ + K+ + clays (1). In this study, all the groundwater samples had a ratio of Ca2+: HCO3 - + CO3 2- and Mg2+: HCO3 - + CO3 2- greater than unity while the ratio of Na+: HCO3 - + CO3 2- were far below the unity suggesting the predominance of Ca and Mg-containing minerals over Na-containing minerals in the study area. As a result, the ratios of Ca2+ + Mg2+: total cations of most of the water samples had ratios approaching unity while the ratios of Na+ + K+: total cations were far below unity (Figure 1a, 1b). In order to confirm the ion exchange process taking place, Na+/Ca2+ and Na+/(Na+ + Cl-) ratios are also computed. In the study area, the groundwater showed Na+/Ca2+ ratio between 0.20-1.08. The ratio of Na+/(Na+ + Cl-) varied in the range of 0.19-0.51 (Table 2C)

Figure 1 Ratios of the major anions and cations in groundwater from Dinajpur Sadar Upazilla, Bangladesh 

Water class ratings

Table 3 shows that out of 44 samples, 27 were rated as 'good' and 17 were as 'excellent' for irrigation purposes based on Wilcox requirement. According to Richards (RICHARDS, 1968), all irrigation waters were classified as C2S1 (27 samples) and C1S1 (17 samples) categories. C1 indicated 'low' salinity (EC < 250 µS/cm), C2 indicated 'medium' salinity (EC= 250-750 µS/cm), and S1 indicated 'low sodium' with respect to SAR. Irrigation with C1 and C2 class waters is unlikely to affect the osmotic pressure of the soil solution and the cell sap of the crop plants. Among the groundwater samples we collected, 39 were rated as 'excellent' and 5 were rated as 'good' according to Wilcox. Among the samples, 25 samples were classified as 'hard' and 19 samples were grouped as 'moderately hard' waters.

Table 3 - Quality classification of water samples for irrigation 

Sl EC Hardness TDS SAR SSP RSC ---------------------Water class based on--------------------- Alkalinity-
No μS /cm mg/L mg/L EC TDS SAR SSP RSC salinity class
1 310 200 174 0.70 17 -2.83 Good Hard Fre Ex Ex Suit C2-S1
2 160 120 98 0.59 15 -1.87 Ex MH Fre Ex Ex Suit C1-S1
3 180 116 126 0.54 11 -4.27 Ex MH Fre Ex Ex Suit C1-S1
4 190 132 106 0.98 18 -1.41 Ex MH Fre Ex Ex Suit C1-S1
5 300 272 186 0.34 13 -4.49 Good Hard Fre Ex Ex Suit C2-S1
6 240 172 168 0.57 11 -2.17 Ex Hard Fre Ex Ex Suit C1-S1
7 200 148 116 0.82 16 -2.34 Ex MH Fre Ex Ex Suit C1-S1
8 210 116 130 0.33 5 -1.06 Ex MH Fre Ex Ex Suit C1-S1
9 190 120 95 0.41 6 -0.77 Ex MH Fre Ex Ex Suit C1-S1
10 340 260 163 0.40 8 -3.79 Good Hard Fre Ex Ex Suit C2-S1
11 310 284 161 0.32 8 -4.48 Good Hard Fre Ex Ex Suit C2-S1
12 310 232 174 0.25 5 -3.68 Good Hard Fre Ex Ex Suit C2-S1
13 380 260 247 0.40 12 -4.27 Good Hard Fre Ex Ex Suit C2-S1
14 450 300 284 0.43 13 -5.40 Good Hard Fre Ex Ex Suit C2-S1
15 280 116 172 0.79 22 -1.79 Good MH Fre Ex Good Suit C2-S1
16 260 100 179 0.69 23 -1.37 Good MH Fre Ex Good Suit C2-S1
17 320 128 202 0.50 8 -1.35 Good MH Fre Ex Ex Suit C2-S1
18 180 100 103 0.37 5 -0.64 Ex MH Fre Ex Ex Suit C1-S1
19 310 276 208 0.32 7 -4.04 Good Hard Fre Ex Ex Suit C2-S1
20 390 260 269 0.59 9 -4.26 Good Hard Fre Ex Ex Suit C2-S1
21 300 108 204 0.55 6 -0.63 Good MH Fre Ex Ex Suit C2-S1
22 210 160 118 0.67 23 -2.65 Ex Hard Fre Ex Good Suit C1-S1
23 200 144 128 0.68 10 -2.15 Ex MH Fre Ex Ex Suit C1-S1
24 390 164 245 0.58 13 -2.35 Good Hard Fre Ex Ex Suit C2-S1
25 270 132 153 0.55 13 -1.66 Good MH Fre Ex Ex Suit C2-S1
26 310 180 175 0.41 10 -2.55 Good Hard Fre Ex Ex Suit C2-S1
27 330 216 191 0.53 14 -3.71 Good Hard Fre Ex Ex Suit C2-S1
28 270 136 162 0.55 8 -1.46 Good MH Fre Ex Ex Suit C2-S1
29 220 100 142 0.48 6 -0.77 Ex MH Fre Ex Ex Suit C1-S1
30 260 156 148 0.52 9 -1.60 Good Hard Fre Ex Ex Suit C2-S1
31 230 148 122 0.62 11 -1.54 Ex MH Fre Ex Ex Suit C1-S1
32 240 200 163 0.67 14 -3.19 Ex Hard Fre Ex Ex Suit C1-S1
33 220 148 146 0.56 12 -2.04 Ex MH Fre Ex Ex Suit C1-S1
34 230 136 147 0.50 7 -2.09 Ex MH Fre Ex Ex Suit C1-S1
35 290 188 203 0.54 23 -3.14 Good Hard Fre Ex Good Suit C2-S1
36 370 248 237 0.53 29 -4.35 Good Hard Fre Ex Good Suit C2-S1
37 260 192 159 0.45 7 -2.31 Good Hard Fre Ex Ex Suit C2-S1
38 360 260 205 0.62 14 -3.86 Good Hard Fre Ex Ex Suit C2-S1
39 460 258 287 0.53 14 -3.96 Good Hard Fre Ex Ex Suit C2-S1
40 180 100 115 0.55 6 -1.04 Ex MH Fre Ex Ex Suit C1-S1
41 340 220 238 0.48 9 -3.19 Good Hard Fre Ex Ex Suit C2-S1
42 250 164 130 0.54 17 -2.73 Good Hard Fre Ex Ex Suit C2-S1
43 210 160 111 0.51 12 -2.25 Ex Hard Fre Ex Ex Suit C1-S1
44 390 188 222 0.42 11 -2.81 Good Hard Fre Ex Ex Suit C2-S1

Ex = Excellent, Fre = Fresh, Suit = Suitable, MH=moderately hard

DISCUSSION

Stoichiometric evaluation of water samples

The sources of major cations, such as Ca2+ and Mg2+, in groundwater can be the weathering of calcium and magnesium minerals (KRISHNA KUMAR et al., 2009). In the areas of increased clay-rich soil dispersed and where Na+ concentration is higher (YOUSAF et al., 1987), the Mg2+ concentration is relatively higher than that of Ca2+. The ratio HCO3 -: Na+ can also be used to assess the weathering process (KRISHNA KUMAR et al., 2009) that occurs in groundwater. When the HCO3 -: Na+ ratio is greater than 1, carbonate weathering occurs, while a ratio A ratio of Na+/(Na+ + Cl-) higher than 0.5 had only one samples, suggesting that ion exchange process is very low. On the whole, the groundwater samples have the concentration of Na+ higher than that of K+ (Table 2A), because of the greater resistance of K+ to chemical weathering and its adsorption on clay minerals (SUBBA RAO, 2008). This suggests that when there is lack of rain, the decomposition of organic matter by bacterial organisms in the soil would not provide the appropriate CO2 to the rock/water interaction in dry season.

Suitability for irrigation

Plants intake water from soil by osmosis and osmotic pressure is proportional to the salt content, which affects the growth of plants, soil structure and permeability (GUPTA et al., 2009). SAR is an im­portant parameter for the determination of the suit­ability of irrigation water because it is responsible for the sodium hazard (TODD AND MAYS, 2005). In our study, all water samples were suitable for growing crops according to TDS values (Table 2C). In addition to TDS, the relative abundance of sodium with respect to alkaline earths, and the quantity of bicarbonate and car­bonate in excess of alkaline earths also influence the suitability of water for irrigation. This excess is de­noted by 'Residual sodium carbonate' (RSC). A negative RSC value indicates that the total concentration of CO3 2- and HCO3 - is lower than the sum of the Ca2+ and Mg2+ concentrations, reflecting that there is no residual carbonate to react with Na+ to increase the Na hazard in the soil. Trace metals including Cu2+, Zn2+, Fe3+, As3+, Mn2+ were concentrations were low and considered to be suitable for crop production and the soil environment (AYERS AND WESTCOT, 1985). Based on permeability index (DONEEN, 1964), all waters were under Class I and Class II orders. Class I and Class II waters are categorized as good for irrigation with 75% or more of maximum permeability.

Correlations among the parameters

The correlation matrix of 12 parameters, for the 44 samples in the study area is indicated in table 2C. The high correlations between Cl- and HCO3 - (r= 0.75), and between Mg2+ and HCO3 - (r= 0.90), between Mg2+ and Cl- (r= 0.85) and between Ca2+ and Cl- (r= 0.92) indicating that they most likely derive from the same source of water (Table 4). There was a good correlation between the conductivity and, Ca2+, Mg2+, Cl- and HCO3 -. The high correlation between EC and TDS reflects the interdependency of these measurements as general measures of the amount of total dissolved solutes.

Table 4 - Correlation matrix of different chemical constituents of groundwater, n=50, units of each parameter are in Table 2 and Table 3  

EC TDS Cl- HCO3 - NO3 - Ca2+ Mg2+ Na+ K+ SAR SSP HT
EC 1.00
TDS 0.95 1.00
Cl- 0.70 0.64 1.00
HCO3 - 0.66 0.60 0.75 1.00
NO3 - 0.02 0.06 -0.11 -0.06 1.00
Ca2+ 0.77 0.69 0.92 0.81 -0.11 1.00
Mg2+ 0.67 0.59 0.85 0.90 -0.02 0.82 1.00
Na+ 0.13 0.16 0.34 0.32 -0.03 0.19 0.14 1.00
K+ 0.03 0.11 -0.10 -0.16 -0.29 -0.09 -0.20 -0.08 1.00
SAR -0.26 -0.21 -0.20 -0.15 0.00 -0.30 -0.39 0.81 0.05 1.00
SSP 0.10 0.13 0.14 0.18 -0.04 0.08 0.05 0.61 -0.02 0.57 1.00
HT 0.74 0.66 0.92 0.90 -0.06 0.94 0.97 0.17 -0.16 -0.37 0.07 1.00

Italic values are significant at p =0.05 where r ( 0.29

Suitability for drinking and domestic uses

The pH of all groundwater samples was not within the safe limits prescribed for drinking water by WHO (2004). Higher concentration of SO4 2- in drinking water is associated with respiratory problems (SUBBA RAO, 1993). Excess NO3 - can cause methemoglobinemia, gastric cancer, birth malformations and hypertension. However, the concentrations of Na, Cl- , SO4 2- and NO3 - of the studied groundwater samples were far below the recommended limits (Na+= 200 mg/L, Cl- =250 mg/L, SO4 2-=150 mg/L, NO3 -=10 mg/L) for drinking according to WHO (2004). In this study, all waters were under 'moderately hard' (43%) and 'hard' categories (57%).

Industrial rating of groundwater samples

The waters of the study area might not be suitable for brewing, tanning and laundering, where the recommended limits of pH are 6.5-7.0, 6.0-6.8 and 6.0-8.0, respectively (TODD AND MAYS, 2005). Based on chloride concentration, the percent suitability for brewing, carbonated beverage, dairy, sugar and textile industries were 100, 100, 9, 0 and 100, respectively. The TDS concentrations were not suitable for confectionery as the recommended limits of TDS for the above industry is 50-100 mg/L (USEPA, 1975). However, for confectionary and paper and pulp industries, the percent suitability were 5 and 70, respectively (Figure 2) while for brewing, carbonated beverage, dairy and ice manufacture industries, all waters were suitable. The allowable limits of Mn for various industries range from 0.05 to 1.0 mg/L except for sugar manufacture (TODD AND MAYS, 2005).

Figure 2 Relative suitability of studied water samples for various industries based on a) chloride concentrations, b) hardness, c) TDS, and d) manganese concentrations. In X axis, the recommended concentrations for different industries are shown according to USEPA (1975). Abbreviations used are: AC=Air-conditioning, BR=Brewing, CB=Carbonated beverage, CF=Confectionary, DA=Dairy, IM=Ice manufacture, LA=Laundering, PP=Paper & pulp, SU=Sugar, TA=Tanning, TE=Textile, RM=Rayon manufacture 

CONCLUSION

The water in the study area shows enrichment of magnesium and calcium among cations and of bicarbonate among anions. Based on the patterns we observed, it can be concluded that all the shallow tube well and deep tube well water samples of the Dinajpur Sadar Upazilla in the district of Dinajpur, Bangladesh were suitable for irrigation, drinking, domestic and industrial uses; although some samples were rated to be unsuitable for some specific industries for some specific ions.

AKNOWLEDGEMENTS

The authors are sincerely acknowledged to Hajee Mohammad Danesh Science & Technology University for conducting this research.

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Received: May 21, 2013; Accepted: November 21, 2013

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