Abstracts
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.
groundwater; suitability; northwestern Bangladesh
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.
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., 2009KRISHNA KUMAR, S. et al. Assessment of groundwater quality and
hydrogeochemistry of Manimuktha River basin, Tamil Nadu, India. Environmental
Monitoring and Assessment v.159, p.341-351, 2009. Available from:
<http://download.springer.com/static/pdf/807/art%253A10.1007%252Fs1066100806337.pdf?auth66=1393993415_53c010db21cf18baafdc08ae081203e6&ext=.pdf>.
doi 10.1007/s10661-008-0633-7.
http://download.springer.com/static/pdf/...
). 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., 2009KRISHNA KUMAR, S. et al. Assessment of groundwater quality and
hydrogeochemistry of Manimuktha River basin, Tamil Nadu, India. Environmental
Monitoring and Assessment v.159, p.341-351, 2009. Available from:
<http://download.springer.com/static/pdf/807/art%253A10.1007%252Fs1066100806337.pdf?auth66=1393993415_53c010db21cf18baafdc08ae081203e6&ext=.pdf>.
doi 10.1007/s10661-008-0633-7.
http://download.springer.com/static/pdf/...
; SUBBA RAO, 2008SUBBA RAO, N. Environmental impact of industrial effluents in
groundwater regions of Visakhapatnam Industrial Complex. Indian. J. Geol. v. 65, p.
35-43, 1993. Available from:
<http://www.connectjournals.com/subscription_info.php?bookmark=CJ-003054>.
http://www.connectjournals.com/subscript...
).
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, 2005WANTM (Waterwatch Australia National Technical Manual). Module 6 Groundwater Monitoring. Department of the Environment and Heritage, Canberra, 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)TODD, D.K.; MAYS, L. Groundwater Hydrology. Wiley, USA, 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, 1998APHA (American Public Health Association).Standard Methods for the Examination of Water and Wastewater, 20th Edition, American Public Health Association, 1015 FifteenthStreet, NW, Washington, DC 20005-2605, 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).
The Na-Cl relationship has often been used to identify the mechanisms for acquiring
salinity and saline intrusions (JALALI, 2007JALALI, M. Hydrochemical identification of groundwater resources and
their changes under the impacts of human activity in the Chah Basin in Western Iran.
Environmental Monitoring and Assessment, v.130, p.347-364, 2007. Available from:
<http://link.springer.com/article/10.1007%2Fs10661-006-9402-7>
http://link.springer.com/article/10.1007...
).
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, 2008SUBBA RAO, N. Environmental impact of industrial effluents in
groundwater regions of Visakhapatnam Industrial Complex. Indian. J. Geol. v. 65, p.
35-43, 1993. Available from:
<http://www.connectjournals.com/subscription_info.php?bookmark=CJ-003054>.
http://www.connectjournals.com/subscript...
), 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)
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, 1968RICHARDS, L.A. (ed). Diagnosis and Improvement of Saline and Alkali Soils. Agricultural Handbook 60, USDA and IBH. Publishing Co. Ltd. New Delhi, India, 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.
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., 2009KRISHNA KUMAR, S. et al. Assessment of groundwater quality and
hydrogeochemistry of Manimuktha River basin, Tamil Nadu, India. Environmental
Monitoring and Assessment v.159, p.341-351, 2009. Available from:
<http://download.springer.com/static/pdf/807/art%253A10.1007%252Fs1066100806337.pdf?auth66=1393993415_53c010db21cf18baafdc08ae081203e6&ext=.pdf>.
doi 10.1007/s10661-008-0633-7.
http://download.springer.com/static/pdf/...
). In the areas of
increased clay-rich soil dispersed and where Na+ concentration is higher
(YOUSAF et al., 1987YOUSAF, M. et al. Dispersion of clay from some salt-affected, and land
soil aggregates. Soil Sci. Soc. Am. J., v.51, n.4, p.920-924, 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., 2009KRISHNA KUMAR, S. et al. Assessment of groundwater quality and
hydrogeochemistry of Manimuktha River basin, Tamil Nadu, India. Environmental
Monitoring and Assessment v.159, p.341-351, 2009. Available from:
<http://download.springer.com/static/pdf/807/art%253A10.1007%252Fs1066100806337.pdf?auth66=1393993415_53c010db21cf18baafdc08ae081203e6&ext=.pdf>.
doi 10.1007/s10661-008-0633-7.
http://download.springer.com/static/pdf/...
) 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, 2008SUBBA RAO, N. Environmental impact of industrial effluents in
groundwater regions of Visakhapatnam Industrial Complex. Indian. J. Geol. v. 65, p.
35-43, 1993. Available from:
<http://www.connectjournals.com/subscription_info.php?bookmark=CJ-003054>.
http://www.connectjournals.com/subscript...
). 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., 2009GUPTA, S.et al. Geochemical Assessment of groundwater around
Macherla-Karempudi Area, Guntur District, Andhra Pradesh. J. Geol. Society of India,
v. 73, p. 202-212, 2009. Available from:
<http://link.springer.com/article/10.1007%2Fs12594-009-0076-y> Doi:
10.1007/s12594-009-0076-y.
http://link.springer.com/article/10.1007...
). 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, 2005TODD, D.K.; MAYS, L. Groundwater Hydrology. Wiley, USA,
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, 1964DONEEN, L. D. Notes on water quality in agriculture. Davis: Univ.
California, 1964. (Published in Water Science and Engineering).), 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.
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, 1993SUBBA RAO, N. Environmental impact of industrial effluents in
groundwater regions of Visakhapatnam Industrial Complex. Indian. J. Geol. v. 65, p.
35-43, 1993. Available from:
<http://www.connectjournals.com/subscription_info.php?bookmark=CJ-003054>.
http://www.connectjournals.com/subscript...
). 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, 2005TODD, D.K.; MAYS, L. Groundwater Hydrology. Wiley, USA, 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, 1975USEPA (US Environmental Protection Agency). Federal Register, v.40, p. 59566-59588,1975.). 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, 2005TODD, D.K.; MAYS, L. Groundwater Hydrology. Wiley, USA, 2005.).
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)USEPA (US Environmental Protection Agency). Federal Register, v.40, p. 59566-59588,1975.. 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.
REFERENCES
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» https://doi.org/10.1007/s12594-009-0076-y» http://link.springer.com/article/10.1007%2Fs12594-009-0076-y - JALALI, M. Hydrochemical identification of groundwater resources and their changes under the impacts of human activity in the Chah Basin in Western Iran. Environmental Monitoring and Assessment, v.130, p.347-364, 2007. Available from: <http://link.springer.com/article/10.1007%2Fs10661-006-9402-7>
» http://link.springer.com/article/10.1007%2Fs10661-006-9402-7 - KRISHNA KUMAR, S. et al. Assessment of groundwater quality and hydrogeochemistry of Manimuktha River basin, Tamil Nadu, India. Environmental Monitoring and Assessment v.159, p.341-351, 2009. Available from: <http://download.springer.com/static/pdf/807/art%253A10.1007%252Fs1066100806337.pdf?auth66=1393993415_53c010db21cf18baafdc08ae081203e6&ext=.pdf>. doi 10.1007/s10661-008-0633-7.
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Publication Dates
-
Publication in this collection
July 2014
History
-
Received
21 May 2013 -
Accepted
21 Nov 2013