EVALUATION OF IONIC TOXICITY OF GROUNDWATER FOR IRRIGATION IN THE SELECTED AQUIFERS OF RANGPUR AREA

A Thesis By

Examination Roll No.: 10 Ag. Chem.JD-03 M Registration No.: 32171 Session: 2005-2006 Semester: July-December, 2011

MASTER OF SCIENCE (M. S.) IN AGRICULTURAL CHEMISTRY

DEPARTMENT OF AGRICULTURAL CHEMISTRY BANGLADESH AGRICULTURAL UNIVERSITY

NOVEMBER, 2011 EVALUATION OF IONIC TOXICITY OF GROUNDWATER FOR IRRIGATION IN THE SELECTED AQUIFERS OF GANGACHARA AREA UNDER THE DISTRICT OF RANGPUR

A Thesis By

Examination Roll No.: 10 Ag. Chem.JD-03 M Registration No.: 32171 Session: 2005-2006 Semester: July-December, 2011

Submitted to the Department of Agricultural Chemistry Bangladesh Agricultural University, Mymensingh In partial fulfillment of the requirements For the degree of

MASTER OF SCIENCE (M. S.) IN AGRICULTURAL CHEMISTRY

DEPARTMENT OF AGRICULTURAL CHEMISTRY BANGLADESH AGRICULTURAL UNIVERSITY MYMENSINGH

NOVEMBER, 2011 EVALUATION OF IONIC TOXICITY OF GROUNDWATER FOR IRRIGATION IN THE SELECTED AQUIFERS OF GANGACHARA AREA UNDER THE DISTRICT OF RANGPUR

A Thesis By

Examination Roll No.: 10 Ag. Chem.JD-03 M Registration No. 32171 Session: 2005-2006 Semester: July-December, 2011

Approved as to style and contents by

______(Prof. Dr. Md. Mokhlesur Rahman) Supervisor

______(Prof. Dr. Md. Abul Khair Chowdhury) Co-supervisor

______(Dr. Md. Zakir Hossen) Chairman, Examination Committee and Head, Department of Agricultural Chemistry Bangladesh Agricultural University, Mymensingh

NOVEMBER, 2011

EVALUATION OF IONIC TOXICITY OF GROUNDWATER FOR IRRIGATION IN THE SELECTED AQUIFERS OF GANGACHARA UNDER RANGPUR DISTRICT

A Thesis

Submitted to Bangladesh Agricultural University, Mymensingh In Partial Fulfillment of the Requirements for the Degree of Master of Science in Agricultural Chemistry

By Aktarunnahar

Approved as to style and contents by

______(Prof. Dr. Md. Mokhlesur Rahman) (Prof. Dr. Md. Abul Khair Chowdhury) Supervisor Co-supervisor

______(Dr. Md. Zakir Hossen) Chairman, BOS and Head

Department of Agricultural Chemistry Bangladesh Agricultural University Mymensingh

November, 2011

EVALUATION OF IONIC TOXICITY OF GROUNDWATER FOR IRRIGATION IN THE SELECTED AQUIFERS OF GANGACHARA UPAZILA UNDER RANGPUR DISTRICT

MS THESIS THESIS MS

A Thesis

TER Submitted to Bangladesh Agricultural University, Mymensingh In Partial Fulfillment of the Requirements for the Degree of

Master of Science in Agricultural Chemistry

IONIC TOXICITY IONIC OF GROUNDWA By

Aktarunnahar Roll No.: 10 Ag. Chem. JD 03 M Registration No.: 32171 Session: 2005-2006

AKTARUNNAHAR DEPARTMENT OF AGRICULTURAL CHEMISTRY BANGLADESH AGRICULTURAL UNIVERSITY MYMENSINGH

November, 2011 NOVEMBER 2011 2011 NOVEMBER ACKNOWLEDGEMENT

All praises are due to the Almighty Allah Whose divine blessing enabled the researcher to complete her research work and prepare the thesis successfully for the degree of MS in Agricultural Chemistry.

The author likes to express her gratefulness and indebtedness to her respected supervisor Prof. Dr. Md. Mokhlesur Rahman, Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh for his kind advice, valuable guidance and constructive suggestions to carry out the research work and preparation of this thesis.

The author acknowledges her heartiest gratification and sincere appreciation to her honorable co- supervisor, Prof. Dr. Md. Abul Khair Chowdhury, Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh for his sincere advice, planning, upgrading the quality of the research work and for help in preparing the manuscript of this thesis.

The author humbly desires to acknowledge her sincere gratitude to Prof. Dr. M. Wahid-U-Zzaman, Prof. Dr. Hari Pada Seal, Prof. Kartik Chandra Saha, Prof. Dr. Md. Akhter Hossain Chowdhury, Dr. Md. Zakir Hossen, Associate Professor and Head, Dr. Quazi Forhad Quadir, Associate Professor, Dr. Atiqur Rahman, Assistant Professor, Dr. Razia Sultana, Assistant Professor, Dr. K. M. Mohiuddin, Assistant Professor, Mrs. Mousumi Akter, Lecturer, Mosammat Hasina Akter, Lecturer and Mr. Md. Amdad Ali, Lecturer, Department of Agricultural Chemistry for their valuable teaching, inspiration and encouragement during the whole course of this study.

The author would express her special thanks to the staff members, Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh, for extending all laboratory facilities for completing research work.

The author is pleased to express her cordial thanks to all of her friends, classmates and well wishers for their immense inspiration, and kind co-operation during conducting experiment and writing of the thesis.

The author would like to express heartfelt indebtedness to her respected parents, sisters, friends and all other relatives for their never ending prayer, encouragement, sacrifice and dedicated efforts to educate me to this level which can never be forgotten.

The Author

ABSTRACT

Groundwater samples were collected from the selected aquifers of Gangachara upazila under the district of Rangpur to evaluate ionic toxicity for irrigation in relation to soil properties and crop growth. Thirty groundwater samples were collected to assess major ionic constituents in order to classify them on the basis of their suitability for irrigation usage. The chemical analyses included pH, EC, TDS, cations (Ca, Mg, K, Na, Mn and Fe) and anions (CO3, HCO3, Cl, SO4, PO4 and BO3). All groundwater samples were slightly acidic to neutral in nature (pH=6.01-7.00) and were not problematic for crop production. As regards to TDS values, all groundwater samples were rated as fresh water (TDS<1000 mg L-1) in quality. EC and SAR indicated that groundwater samples were low to medium salinity (C1 & C2) and low alkalinity (S1) hazards combinedly expressed as C1S1 and C2S1, which could be safely used for moderate salt tolerance crops growing on soils with moderate level of permeability and leaching. Groundwater samples were classified as excellent, good and permissible in quality based on SSP. All groundwater samples except one sample were free from RSC and belonged to suitable in category. As per hardness (HT), 1 sample was rated as soft, 16 samples were moderately hard and the rest 13 samples were hard in quality. In 11 groundwater samples, HCO3 ion was considered as problematic for irrigating soils and crops. The concentrations of Fe, BO3, SO4, PO4 and Cl ions were detected below the toxic levels and might not pose threat to soil system as irrigation water. The detected quantity of Mn ion in 28 samples was observed within the permissible limit (0.20 mg L-1) but its content in 2 samples exceeded the acceptable limit and this ion was treated as toxicant for irrigation. The relationship between different water quality criteria like pH, EC, TDS, SAR, SSP, RSC and HT were established and combinations such as pH vs EC, pH vs TDS, pH vs RSC, pH vs

HT, EC vs TDS, EC vs RSC, EC vs HT, TDS vs RSC, TDS vs HT, SAR vs SSP and RSC vs HT exhibited significant relationships. Among the major ions, Ca vs Mg, Ca vs Na, Ca vs K and Na vs K were significantly correlated.

CONTENTS

CHAPTER TITLE PAGE NO. ACKNOWLEDGEMENT iv ABSTRACT v LIST OF CONTENTS vi LIST OF TABLES ix LIST OF FIGURES ix LIST OF APPENDIX ix 1. INTRODUCTION 1 2. REVIEW OF LITERATURE 3 2.1 Groundwater quality on the basis of pH 3 2.2 Groundwater quality on the basis of electrical conductivity 4 2.3 Groundwater quality on the basis of total dissolved solids 6 2.4 Groundwater quality on the basis of calcium and 7 magnesium 2.5 Groundwater quality on the basis of potassium and 9 sodium 2.6 Groundwater quality on the basis of iron 10 2.7 Groundwater quality on the basis of manganese 10 2.8 Groundwater quality on the basis of boron 12 2.9 Groundwater quality on the basis of carbonate and 13 bicarbonate 2.10 Groundwater quality on the basis of phosphate 14 2.11 Groundwater quality on the basis of sulphate and chloride 15 2.12 Groundwater quality on the basis of hardness 17 2.13 Groundwater quality on the basis of sodium adsorption 18 ratio 2.14 Groundwater quality on the basis of soluble sodium 19 percentage 2.15 Groundwater quality on the basis of residual sodium 20 carbonate

CONTENTS (To be contd.)

CHAPTER TITLE PAGE NO.

3. MATERIALS AND METHODS 21

3.1 Collection and preparation of groundwater 21 samples

3.2 Analytical techniques 24

3.2.1 pH 24

3.2.2 Electrical conductivity 24

3.2.3 Total dissolved solids 25

3.2.4 Ionic constituents 25

3.2.4.1 Calcium 25

3.2.4.2 Magnesium 25

3.2.4.3 Potassium and sodium 25

3.2.4.4 Iron and manganese 26

3.2.4.5 Boron 26

3.2.4.6 Carbonate 26

3.2.4.7 Bicarbonate 26

3.2.4.8 Sulphate 26

3.2.4.9 Phosphate 27

3.2.4.10 Chloride 27

3.3 Evaluation of ionic toxicity of groundwater 27

3.4 Statistical analyses 28

CONTENTS (To be contd.)

CHAPTER TITLE PAGE NO. 4. RESULTS AND DISCUSSION 29 4.1 Assessment of ionic toxicity of groundwater 29 for irrigation 4.1.1 pH 29 4.1.2 Electrical conductivity 29 4.1.3 Total dissolved solids 30 4.2 Ionic constituents 30 4.2.1 Calcium 30 4.2.2 Magnesium 33 4.2.3 Potassium 33 4.2.4 Sodium 33 4.2.5 Iron 34 4.2.6 Manganese 34 4.2.7 Boron 34 4.2.8 Carbonate 35 4.2.9 Bicarbonate 35 4.2.10 Phosphate 35 4.2.11 Sulphate 35 4.2.12 Chloride 36 4.3 Groundwater quality determining indices 36 4.3.1 Sodium adsorption ratio 36 4.3.2 Soluble sodium percentage 36 4.3.3 Residual sodium carbonate 37 4.3.4 Hardness 37 4.4 Relationship between water quality factors 40

5. SUMMARY AND CONCLUSION 44 REFERENCES 46 APPENDICES 51

LIST OF TABLES

TABLE NO. TITLE PAGE NO. 3.1 Detailed information of groundwater sampling 23 4.1 pH, EC, TDS and anionic constituent of groundwater 31 samples 4.2 Cationic constituent of groundwater samples 32 4.3 Quality rating and suitability of groundwater used for 38 irrigation 4.4 Correlation matrix among water quality parameters 41

LIST OF FIGURES

FIGURE NO. TITLE PAGE NO. 3.1 Groundwater sampling sites of Gangchara upazila under 22 Rangpur district. 4.1 Diagram for classifying groundwater used for irrigation 39 (Richards, 1968) 4.2 Relationships between Ca vs Mg (a) and Na vs Ca (b) 42 4.3 Relationships between K vs Ca (a) and K vs Na (b) 43

LIST OF APPENDIX

APPENDIX NO. TITLE PAGE NO. 1 Water classification on the basis of EC and SSP 51 2 Water classification as per TDS 51 3 Water class rating based on SAR 51 4 Water classification according to RSC 52 5 Classification of water on the basis of hardness (HT) 52 6 Classification of water on the basis of B concentration 52 7 Recommended maximum concentration of different ions in 53 water used for irrigation

CHAPTER - 1

INTRODUCTION

Irrigation of plants is an essential prerequisite for attaining high yields but the quality of groundwater is an important criterion for long-term irrigation because it contains relatively high content of ions as dissolved chemical constituents as compared to surface water. The quantity and quality of various ions in water system affects its agricultural utilization. The quality of groundwater plays a vital role in assessing the availability of safe water for various agricultural usages. Water analyses are very important for the assessment of its quality for irrigation and understanding of soil and water management. If low quality of water is used for irrigation, toxic elements may accumulate in soil and create crop toxicity resulting reduction in yield. In determining the availability of water for irrigation, quality concern has often been neglected. But it is equally important as quantity is evaluation of water resources potentially for irrigation use in successful crop production.

When groundwater is applied for long-term irrigation, some ions are beneficial and few ions are more or less detrimental for soil ecosystem. Among the ions, Ca, Mg, Na, Cl, Fe, B, and

HCO3 are of prime importance in assessing the quality of water for irrigation ((Michael, 1978; Ayers and Westcot, 1985). The usual toxic ions such as B, Na and Cl in groundwater for irrigation are sensitive to plant at relatively low concentration (Bohn et al., 1985). The detection of ions such as Fe, Mn, B and Cl in water system is necessary, because if their concentrations attain level that are considered to be contaminants causing significant degradation of water quality.

Nowadays, the application of groundwater in Bangladesh is increasing more rapidly than surface water. In intensive agricultural practices towards the goal of food grain self- sufficiency to overcome the food crisis of over population, irrigated lands have expanded day by day during dry season. Intensive agriculture is heavily dependent on agricultural chemicals and as a result, impact of increased use of these chemicals lead to contamination of water sources. Water ecosystem is being contaminated due to the indiscriminate use of agrochemicals and the uncontrolled disposal of different industrial effluents. Water is considered as polluted when it is changed in its quality or composition, directly or indirectly as a result of human activities and naturally contamination. The polluted water contains undesirable toxic metals or ions. Water containing these toxic ions has a direct impact on the usable quality of water. Henceforth, it becomes less suitable for irrigation in relation to soil properties and crop growth. Recently, the increased attention has been drawn to some trouble ions in water for monitoring and management of these ions to environmental problems related safe use of water. In this aspect, it becomes a prime need to conduct field level investigations of the existing water management practices in rural areas of Bangladesh.

An investigation has been conducted to appraise groundwater quality for irrigation at Gangachara upazila under the district of Rangpur. This area is situated in the AEZ-02 viz., Active Tista Floodplain. In the dry season, groundwater has always been a major source of fresh water supply because most of the surface water sources become dry and only option left behind is the groundwater. Under intensive cultivation, irrigated lands have expanded rapidly during dry season. As a result, the exploitation of groundwater in Bangladesh is increased day by day. There is no systematic organization to appraise the extent of ionic toxicity of groundwater in the study area.

Keeping the above facts in mind, this area was selected to assess the ionic toxicity level of groundwater for irrigation purpose. Consequently, a research work was carried out at the Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh with the following objectives:

(i) To assess ionic toxicity of groundwater for irrigation in relation to soil properties and crop growth. (ii) To categorize groundwater on the basis of standard criteria as regards to suitability for irrigation usage. (iii) To suggest efficient groundwater management in the investigated area.

CHAPTER - 2

REVIEW OF LITERATURE

Water is one of the most valuable resources throughout the world and contains variable quantities of inorganic and organic substances. Its quality is equally or even more important than its quantity. It is necessary to evaluate the quality of groundwater for irrigation usage. For this reason, there is an urgent need to judge water quality for specific beneficial purpose. An attempt has been made to study the pertinent research information related to water pollution or quality. But a few research works have been conducted on this perspective at home and abroad. However, some relevant research findings are mentioned under the following sequences:

2.1 Groundwater quality on the basis of pH pH values of 35 groundwater samples collected from 6 unions of Faridpur sadar upazila under the district of Faridpur ranged from 6.97 to 7.62 indicating neutral to slightly alkaline nature (Shaik, 2010). Khanam (2009) found that pH values of ground water samples collected from 4 unions of Atpara upazila under the district of Netrakona area varied from 7.04 to 8.48 showing neutral to slightly alkaline in nature. Shaik (2009) found that pH values of all groundwater samples collected from Madhukhali upazila under ranged from 7.1 to 8.2 reflecting neutral to slightly alkaline in nature. pH values of groundwater samples collected from three unions of sadar upazila under the district of Rangpur ranged from 7.2 to 8.2 indicating neutral to slightly alkaline in nature (Chowdhury, 2007). Rahman and Rahman (2007) observed that pH values of groundwater samples collected from 4 unions of Sherpur upazila under district ranged from 7.1 to 8.4 showing neutral to moderately alkaline in nature.

Monem (2007) stated that pH values of groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari area varied from 7.2 to 7.8 reflecting neutral to slightly alkaline in nature. A study was conducted by Rahman and Rahman (2006) at 5 unions of Atrai upazila under Naogaon district and found that pH value ranged from 7.8 to 8.5 revealing slightly alkaline to alkaline in nature. pH values of groundwater of sadar upazila under Sherpur district, sadar upazila under Gaibandha district and Atrai upazila under Naogaon district varied from 7.4 to 8.3, 7.2 to 8.4 and 7.9 to 8.4, respectively (Rahman et al., 2005). Ahsan (2004) found that pH values of groundwater samples of division within the limit of 5.27 to 7.99 indicating strongly acidic to moderately alkaline. Uddin (2004) assessed that pH value of groundwater sample collected from district ranges from 5.32 to 7.00. pH value of groundwater from sadar varied from 7.50 to 8.20 reflecting slightly alkaline to alkaline in nature (Arefin, 2002). Zaman et al. (2001) measured that pH value of different villages of Dakatia and Kachina unions under Mymensingh district varied from 7.26 to 9.67 showing neutral to very strongly alkaline in nature. Rahman (2001) stated that in groundwater samples of Sherpur upazilla under Bogra district, pH values from 4.2 to 8.8 showing acidic to alkaline. pH values of water samples in Tongi aquifers were within the range of 6.69 to 7.63 indicating slightly acidic to alkaline in nature (Sen et al., 2000).

pH values of groundwater collected from Sherpur sadar under Old Brahmaputra Floodplain were within the limit of 7.64 to 8.90 indicating slightly alkaline to alkaline in nature (Hoque, 2000). Jesmin (2000) observed that pH values of groundwater in Gaibandha aquifers ranged from 6.73 to 8.66 reflecting slightly acidic to alkaline in nature. Rahman (2000) stated that pH of groundwater samples of Atrai upazila under Naogaon district was within the limit of 6.88 to 9.84. pH value of water samples collected from Bagmara, Mahadebpur and Nachoul upazila varied from 7.48 to 9.44, 6.74 to 9.33 and 6.8 to 8.22, respectively ( Zaman, 2000).

Nizam et al. (1999) analyzed 103 water samples from 11 unions of Bhaluka upazila under Mymensingh district and reported that pH values were within the range of 2.80 to 10.30 indicating acidic to alkaline in nature. Mitra and Gupta (1999) assessed that pH of tube well water during monsoon and winter seasons varied from 7.4 to 7.5 and 7.5 to 7.6, respectively.

2.2 Groundwater quality on the basis of electrical conductivity

Shaik (2010) reported that EC of groundwater samples collected from 6 unions of Faridpur sadar upazila under the district of Faridpur varied from 274 to 713 µS cm-1 with the mean value of 460.11 µS cm-1. Khanam (2009) found that EC values of groundwater samples collected from 4 unions of Atpara upazila under the district of Netrokona area were within the range of 140 to 578 µS cm-1 with the mean value of 357.95 µS cm-1. Shaik (2009) reported that EC values of all groundwater samples from Madhukhali upazila under Faridpur district area varied from 138 to 568 µS cm-1 with the mean value of 260.89 µS cm-1. Chowdhury (2007) observed that EC values of groundwater samples collected from three unions of sadar upazila under Rangpur district varied from 80 to 580 µS cm-1 with the mean value of 221.65 µS cm-1.

Rahman and Rahman (2007) explained that EC values of water samples collected from four unions viz., Sughat, Mirzapur, Kumbi and Garidaha under Sherpur upazila of Bogra district ranged from 363.3 to 670.8 µS cm-1 showing medium salinity hazards class and could be used for moderately salt tolerance plants with moderate level of permeability and leaching. Monem (2007) found that EC values of groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari area ranged from 90 to 245µS cm-1. A study was conducted by Rahman and Rahman (2006) at 5 unions of Atrai upazila under Naogaon district and obtained EC values ranging from 367.0 to 733.9 µS cm-1 which revealed medium salinity class. EC values of groundwater samples of sadar upazila under

Sherpur district, sadar upazila under Gaibandha district and Atrai upazila under Naogaon district varied from 275 to 1198 µS cm-1 denoting medium to high salinity classes (Rahman et al., 2005).

Ahsan (2004) analysed 136 groundwater samples collected from most of the areas of Sylhet division varied from 19.57 to 1655.40 µS cm-1. EC values of groundwater collected from Dinajpur districts ranged from 75.47 to 565.35 µS cm-1 (Uddin, 2004). Latha et al. (2002) collected 133 water samples from Avinashi, Pollachi, Palladam areas of Tamil Nadu and reported EC values of 0.45 to 4.5, 2.27 to 9.95 and 0.20 to 2.70 µS cm-1, which were unsuitable for irrigation as they liable to cause salinity and sodicity in soils. Zaman et al. (2001) observed that EC values of different villages of Dakatia and Kachina unions under Mymensingh district varied from 266.88 to 822.8 µS cm-1 showing medium to high salinity classes. EC values of water from groundwater collected from Sherpur sadar aupazila under Sherpur district varied from 174 to 522 µS cm-1 and all water under investigation were under low to medium salinity classes (Hoque, 2000).

Sen et al. (2000) investigated water quality for irrigation at Tongi aquifer under the district of Gazipur and found that EC values of groundwater samples varied from 185 to 992 µS cm-1 reflecting low to high salinity hazard classes. Jesmin (2000) found that EC values of groundwater samples in Gaibandha aquifers varied from 274 to 1465 µS cm-1 showing medium to high salinity hazard classes. Rahman (2000) stated that EC values of all samples from Atrai upazila under Naogaon district ranged from 366.96 to 733.92 µS cm-1 and all water samples under test were medium salinity hazard class. Nizam et al. (1999) stated that EC values of groundwater samples collected from 11 unions of Bhaluka upazila under Madhupur Tract ranged from 244.64 to 822.88 µS cm-1 indicating low to high salinity hazard classes.

2.3 Groundwater quality on the basis of total dissolved solids

Total dissolved solids of groundwater samples collected from 6 unions of Faridpur sadar upazila under the district of Faridpur ranged from 164 to 382 mg L-1 with mean value of 268.78 mg L-1 (Shaik, 2010). Khanam (2009) explained that TDS values of groundwater samples collected from 4 unions of Atpara upazila under the district of Netrakona area varied from 98.0 to 392.0 mg L-1 with a mean value of 239.1 mg L-1. Shaik (2009) found that the measured TDS values of groundwater samples in the Madhukhali upazila under Faridpur district area varied from 108 to 386 mg L-1 with mean value of 179.60 mg L-1. Monem (2007) obtained that TDS values of groundwater samples analyzed from four unions of Kishoreganj upazila under the district of Nilphamari area varied from 46.59 to 240.91 mg L-1. TDS values of groundwater collected from four unions of Sherpur upazila under Bogra district were within the limit of 275.4 to 440.7 mg L-I reflecting fresh water in quality (Rahman et al., 2007). Chowdhury (2007) stated that TDS values of all samples collected from three unions of sadar upazila under Rangpur district area were within the limit of 55.0 to 393.0 mg L-1.

Rahman et al. (2006) found that TDS values of groundwater samples collected from five unions under Atrai upazila of Naogaon district varied from 242.0 to 479.2 mg L-1 indicating fresh water. Rahman et al. (2005) measured TDS values of groundwater collected from three districts namely Sherpur, Gaibanda and Naogaon and obtained TDS values varied from 172.0 to 806.0 mg L-1 reflecting freshwater in quality. Ahsan (2004) found that TDS values in groundwater samples of Sylhet division varied from 13.87 to 1036.87 mg L-1 revealing fresh water to brackish water in quality. TDS values of groundwater samples from Dinajpur district ranged from 52.02 to 422.51 mg L-1 (Uddin, 2004) and that of Kushtia and Chuadanga district ranged from 247.78 to 870.45 mg L-1 (Azad, 2004 ). TDS values of groundwater of sadar upazila under Pabna district ranged from 336.26 to 671.89 mg L-1 (Arefin, 2002) and that of Sherpur under Bogra district ranged from 194.85 to 458.48 mg L-1

(Rahman, 2001). Zaman et al. (2001) found that TDS values of different villages of Dakatia and Kachina unions under Mymensingh district varied from 200.00 to 550.31 mg L-1 indicating fresh water in quality.

Sen et al. (2000) stated that TDS values of some groundwater collected from Tongi aquifers varied from 123 to 675 mg L-1 indicating fresh water in quality. TDS values of groundwater collected from Sherpur sadar under Sherpur district varied from 112 to 358 mg L-1 reflecting fresh water in quality (Hoque, 2000). In groundwater samples of Gaibandha aquifers, TDS values varied from 192.0 to 1000.0 mg L-1 (Jesmin, 2000) Rahman (2000) revealed that TDS values of groundwater samples at Atrai upazila under the district of Naogaon ranged from 242.19 to 479.17 mg L-1. TDS values of groundwater samples collected from 11 unions of Bhaluka upazila under Mymensingh district were within the range of 26.0 to 660.0 mg L-1 (Nizam et al., 1999). TDS values of groundwater samples at Tripur in India ranged from 1500.0 to 8000.0 mg L-1 (Senthilnathan and Azeez, 1999).

2.4 Groundwater quality on the basis of calcium and magnesium

Shaik (2010) reported that the concentrations of Ca and Mg in groundwater samples collected from 6 unions of sadar upazila under the district of Faridpur ranged from 0.25 to 1.25 me L-1 with mean value of 0.49 me L-1 and 0.50 to 1.67 me L-1 with the mean value of 0.89 me L-1, respectively. Khanam (2009) reported that the contents of Ca and Mg in groundwater samples collected from 4 unions of Atpara upazila under the district of Netrokona area ranged from 0.20 to 3.80 me L-1 with the average value of 2.22 me L-1and 0.56 to 3.94 me L-1 with the average value of 2.65 me L-1, respectively. Shaik (2009) found that in groundwater samples collected from Madhukhali upazila under Faridpur district, the concentrations of Ca and Mg ranged from 0.50 to 3.35 me L-1 with the average value of 1.46 me L-1 and 0.50 to 2.75 me L-1 with the average value of 1.35 me L-1, respectively.

Chowdhury (2007) expressed that the concentrations of Ca and Mg in groundwater samples collected from three unions of sadar upazila under Rangpur district area ranged from 0.26 to 3.09 me L-1 and 0.15 to 1.60 me L-1, respectively.

Rahman and Rahman (2007) reported that Ca and Mg contents in groundwater samples collected from 4 unions of Sherpur upazila under Bogra district ranged from 1.1 to 2.8 me L- 1 and 1.2 to 3.1 me L-1, respectively. Monem (2007) found that the concentrations of Ca and Mg in groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari area were within the limit of 0.20 to 1.00 me L-1 and 0.10 to 1.59 me L- 1 with the average values of 0.51 me L-1 and 0.74 me L-1 , respectively. A study was conducted by Rahman and Rahman (2006) at 5 unions of Atrai upazila under Naogaon district and found that Ca and Mg contents ranged from 0.6 to 2.2 me L-1 and 1.6 to 4.0 me L-1, respectively. The contents of Ca and Mg in groundwater of sadar upazila under Sherpur district, sadar upazila under Gaibandha district and Atrai upazila under Naogaon district varied from 0.7 to 3.0 me L-1 and 0.6 to 6.1 me L-1, respectively (Rahman et al., 2005).

Uddin (2004) measured that Ca and Mg contents of groundwater samples collected from Dinajpur district ranged from 4.21 to 72.54 me L-1 and 0.85 to 18.60 me L-1, respectively. Zaman et al. (2001) found that the concentrations of Ca and Mg in groundwater samples of different villages of Dakatia and Kachina unions under Mymensingh district ranged from 0.30 to 1.70 me L-1 and 0.40 to 3.50 me L-1, respectively. Sen et al. (2000) found that in Tongi aquifers, the concentrations of Ca and Mg in water samples varied from 0.50 to 3.21 me L-1 and 0.70 to 5.13 me L-1, respectively. The amounts of Ca and Mg in groundwater samples collected from Gaibandha sadar under Gaibandha district varied from 0.72 to 3.01 me L-1 and 1.80 to 6.80 me L-1, respectively (Jesmin, 2000).

Hoque (2000) observed that Ca and Mg contents in all the water samples of Sherpur sadar under Sherpur district ranged from 0.5 to 2.0 me L-1 and 0.4 to 2.0 me L-1, respectively. Rahman (2000) collected 88 groundwater samples from Atrai upazila under Naogaon district and recorded that the amounts of Ca and Mg ranged from 0.50 to 2.20 me L-1 and 0.70 to 4.10 me L-1, respectively. Nizam et al. (1999) assessed that Ca and Mg contents in ground water samples collected from Bhaluka upazila under Mymensingh district varied from 0.10 to 2.80 me L-1 and 0.40 to 4.40 me L-1, respectively. During monsoon season, Ca and Mg contents of tube well waters in vegetables growing area around Calcutta were 8.0 and 3.4 me L-1, respectively (Mitra and Gupta, 1999).

2.5 Groundwater quality on the basis of sodium and potassium

The concentrations of Na and K in groundwater samples collected from 4 unions of Atpara upazila under the district of Netrakona area ranged from 0.35 to 0.91 me L-1 with the mean value of 0.54 me L-1 and 0.034 to 0.103 me L-1 with the mean value of 0.061 me L-1, respectively (Khanam, 2009). Shaik (2009) measured that concentrations of Na and K in all groundwater samples collected from Madhukhali upazila under Faridpur district ranged from 0.04 to 0.85 me L-1 with the mean value of 0.42 me L-1 and 0.04 to 0.51 me L-1 with the mean value of 0.24 me L-1, respectively. The contents of Na and K in water samples collected from four unions of Sherpur upazila under Bogra district ranged from 0.10 to 1.36 me L-1 and 0.02 to 0.16 me L-1, respectively (Rahman and Rahman, 2007). Chowdhury (2007) reported that the concentrations of Na and K in groundwater samples collected from three unions of Sadar upazila under Rangpur district area ranged from 0.30 to 1.83 me L-1 and 0.02 to 1.11 me L-1, respectively. Momen (2007) assessed that the concentrations of Na and K in groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari area were within the limit of 0.07 to 0.31 me L-1 and 0.04 to 0.30 me L- 1 , resectively. The concentrations of Na and K in groundwater samples collected from five

unions under Atrai upazila of Naogaon district varied from 0.52 to 1.13 me L-1 and 0.10 to 0.80 me L-1, respectively (Rahman and Rahman, 2006).

The contents of Na and K in groundwater samples collected from three districts namely Sherpur, Gaibanda and Naogaon varied from 0.16 to 4.25 me L-1 and 0.01 to 0.74 me L-1, respectively (Rahman et al., 2005). Azad (2004) carried out a study by collecting water samples from different villages of Kushtia and Chuadanga districts and reported that the concentrations of Na and K ranged from 2.76 to 56.33 me L-1 and o.43 to 17.60 mg L-1, respectively. Zaman et al. (2001) carried out a study by collecting groundwater samples from different villages of Mymensingh district and assessed that concentrations of Na and K ranged from 0.108 to 0.315 me L-1 and 0.003 to 0.022 me L-1, respectively. Sen et al. (2000) found that in Tongi aquifers, the concentrations of Na and K in groundwater samples varied from of 0.20 to 2.28 me L-1 and 0.12 to 0.59 me L-1, respectively. The contents of Na and K in all groundwater samples collected from sadar upazila under Gaibandha district ranged from 0.06 to 0.74 me L-1 and 0.45 to 6.47 me L-1, respectively (Jesmin, 2000). Hoque (2000) reported that Na and K contents in all groundwater samples of Sherpur sadar under Sherpur district ranged from 0.006 to 0.421 me L-1 and 0.097 to 2.260 me L-1, respectively.

2.6 Groundwater quality on the basis of iron

Shaik (2010) found that the content of Fe in groundwater samples collected from 6 unions of Faridpur sadar upazila under the district of Faridpur ranged from 0.007 to 0.028 mg L-1 with mean value of 0.018 mg L-1. Khanam (2009) observed that the concentration of Fe in groundwater samples collected from 4 unions of Atpara upazila under the district of Netrakona area was within the range of 0.030 to 0.085 mg L-1 with the mean value of 0.052 mg L-1. Uddin (2004) stated that the concentration of Fe in groundwater collected from Dinajpur district ranged from 0.01 to 1.27 mg L-1.

Arefin (2002) obtained that Fe concentration in groundwater samples of Pabna sadar upazila varied from 0.028 to 0.488 mg L-1. The concentration of Fe in groundwater samples collected from Sherpur aquifers under Bogra district varied from 0.07 to 1.25 mg L-1 (Rahman, 2000). Sen et al. (2000) stated that in Tongi aquifers, the content of Fe in groundwater samples varied from trace to 0.09 mg L-1. Jesmin (2000) found that the concentration of iron in groundwater collected from Gaibandha aquifer ranged from 0.15 to 1.00 mg L-1.

2.7 Groundwater quality on the basis of manganese

The content of Mn in groundwater samples collected from 6 unions of Faridpur sadar upazila under the district of Faridpur was within the limit of 0.012 to 0.59 mg L-1 with average of 0.051 mg L-1. Khanam (2009) analyzed 45 groundwater samples collected from 4 unions of Atpara upazila under the district of Netrakona area and found that all groundwater samples contained Mn ranging from 0.005 to 0.050 mg L-1 with average value of 0.019 mg L-1. Shaik (2009) assessed that all groundwater samples of Madhukhali upazila under Faridpur district contained Mn ranging from trace to 0.087 mg L-1 with average value of 0.023 mg L-1. Chowdhury (2007) evaluated that the concentration of Mn in groundwater samples collected from three unions of sadar upazila under Rangpur district area varied from 0.02 to 0.55 mg L-1. Monem (2007) revealed that the concentration of Mn in groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari area were within the limit of 0.03 to 0.90 mg L-1. Rahman and Rahman (2007) assessed that the concentration of Mn in groundwater samples analysed from 4 unions of Sherpur upazila under Bogra district ranged from 0.02 to 0.18 mg L-1. A study conducted by Rahman and Rahman (2006) at 5 unions of Atrai upazila under Naogaon district and found that the content of Mn ranged from 0.05 to 0.22 mg L-1. The amount of Mn in groundwater of sadar upazila under Sherpur district, sadar upazila under

Gaibandha district and Atrai upazila under Naogaon district varied from 0.04 to 0.50 mg L-1 (Rahman et al., 2005).

Zaman et al. (2001) revealed that the content of Mn in different villages of Dakatia and Kachina unions under Mymensingh district ranged from 0.014 to 0.205 mg L-1. In Tongi aquifers, the concentration of Mn in groundwater samples ranged from trace to 0.30 mg L-1 (Sen et al., 2000). An experiment was conducted by Hoque (2000) to evaluate groundwater quality in Sherpur upazila under the district of Bogra. He found that the concentration of Mn in this area ranged from 0.05 to 0.58 mg L-1. Jesmin (2000) obtained that the content of Mn in groundwater samples collected from Gaibandha aquifers varied from 0.03 to 0.10 mg L-1. Rahman (2000) assessed that amount of Mn in groundwater samples collected from Atrai upazila under Naogaon district ranged from trace to 0.24 mg L-1. Nizam et al. (1999) analysed 20 groundwater samples collected from different sources of two unions of Bhaluka upazila under Mymensingh district and reported that groundwater samples contained Mn ranging from 0.091 to 0.347 mg L-1. Zaman et al. (2000) conducted a study at three upazila (Bagmara, Mahadebpur and Nachoul) in Barind area and observed that the mean values of Mn in groundwater samples were 0.11, 0.134 and 0.0478 mg L-1, respectively. The concentration of Mn in groundwater samples of Madhupur Tract was within the range of 0.70 to 0.22 mg L-1 (Alamgir et al., 1999).

2.8 Groundwater quality on the basis of boron

The concentration of B in groundwater samples collected from 6 unions of Faridpur sadar upazila under the district of Faridpur was within the limit from 0.012 to 0.75 mg L-1 with mean value of 0.48 mg L-1 (Shaik, 2010). Khanam (2009) stated that B concentration in groundwater samples collected from 4 unions of Atpara upazila under the district of Netrakona area varied from 0.03 to 0.19 mg L-1 with the mean value of 0.10 mg L-1. Shaik (2009) assessed that B concentration of all groundwater samples collected from Madhukhali upazila under Faridpur district area ranged from 0.08 to 0.42 mg L-1 with the

mean value of 0.21 mg L-1. Chowdhury (2007) found that the concentration of B in groundwater samples collected from three unions of sadar upazila under Rangpur district was within the limit of 0.01 to 0.36 mg L-1.

Monem (2007) revealed that the concentration of B in groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari was within the limit of 0.10 to 0.39 mg L-1. Rahman and Rahman (2007) opined that the concentration of B in groundwater samples collected from 4 unions of Sherpur upazila under Bogra district ranged from 0.10 to 0.52 mg L-1. A study was conducted by Rahman and Rahman (2006) at 5 unions of Atrai upazila under Naogaon district and found that the concentration of B ranged from 0.20 to 0.54 mg L-1. The content of B in groundwater samples of sadar upazila under Sherpur district, sadar upazila under Gaibandha district and Atrai upazila under Naogaon district varied from 0.04 to 0.62 mg L-1 (Rahman et al., 2005). Ahsan (2004) reported that B content of groundwater collected from Sylhet division varied from 0.01 to 0.30 mg L-1. Boron contents in groundwater samples of Pabna sadar upazila varied from trace to 0.39 mg L-1 (Arefin, 2002).

Zaman et al. (2001) measured that the concentration of B in different villages of Dakatia and Kachina unions under Mymensingh district ranged from 0. 080 to 0.540 mg L-1. Nizam et al. (1999) reported that B content of groundwater collected from Bhaluka upazila under Mymensingh district varied from 0.062 to 1.10 mg L-1. All the groundwater samples collected from Gaibandha aquifers contained considerable amount of B (0.042 to 1.19 mg L-1) as reported by Jesmin (2000). Hoque (2000) stated that the concentration of B in groundwater collected from Brahmaputra Floodplain varied from 0.02 to 0.45 mg L-1. The concentration of B in groundwater of Nachol upazila under High Barind area was within the range of 0.003 to 0.53 mg L-1 as reported by Ali (1997).

Sarker (1997) found that B content of Narayangonj aquifers ranged from 0.06 to 0.62 mg L-1. Quddus and Zaman (1996) revealed that B content in groundwater in some villages of Meherpur sadar under Meherpur district ranged from 0.10 to 0.63 mg L-1. The amount of B in groundwater samples of Shahzadpur upazila under the district of Sirajgonj ranged from 0.10 to 0.40 mg L-1 and all groundwater samples under test were safe for irrigation (Rahman and Zaman, 1995). Zaman and Mohiuddin (1995) showed that B content in groundwater samples of thana under varied from 0.08 to 0.45 mg L-1. An investigation was conducted by Quayum (1995) to observe the quality of groundwater collected from sadar upazila under and showed that B concentration varied from 0.15 to 0.54 mg L-1. The content of B in groundwater samples collected from under was within the range of 0.01 to 0.45 mg L-1 and all water samples were excellent to good in quality for irrigation usage (Razzaque, 1995).

2.9 Groundwater quality on the basis of carbonate and bicarbonate

- Shaik (2010) reported that the concentration of HCO3 in groundwater samples collected from 6 unions of sadar upazila under the district of Faridpur was within the limit of 0.30 to -1 -1 - 1.69 me L with average of 0.84 me L . Khanam (2009) stated that HCO3 concentration of groundwater samples collected from 4 unions of Atpara upazila under the district of Netrakona area varied from 0.40 to 4.40 me L-1 with the mean value of 2.27 me L-1. Shaik - (2009) asessed that the concentration of HCO3 in all groundwater samples collected from Madhukhali upazila under Faridpur district ranged from 0.50 to 4.50 me L-1 with the mean -1 - value of 1.89 me L . Chowdhury (2007) concluded that the concentration of HCO3 in groundwater samples collected from three unions of Sadar upazila under Rangpur district area was within the limit of 0.46 to 4.36 me L-1. Monem (2007) reported that the - concentration of HCO3 in groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari area was within the limit of 0.50 to 3.50 me L-1.

- The concentration of HCO3 in groundwater samples collected from four unions Sherpur upazila under Bogra district ranged from 2.50 to 4.50 me L-1 (Rahman et al., 2007). Rahman and Rahman (2007) investigated groundwater samples collected from 4 unions of Sherpur 2- upazila under Bogra district and CO3 was not detected in the ground water and found that - -1 - the concentration of HCO3 ranged from 2.5 to 4.5 me L . The content of HCO3 in groundwater samples collected from five unions under Atrai upazila of Naogaon district varied from 2.40 to 5.50 me L-1 (Rahman et al., 2006).

- The concentration of HCO3 in groundwater samples collected from three districts namely Sherpur, Gaibanda and Naogaon ranged from 1.50 to 6.00 me L-1 (Rahman et al., 2005). The - content of HCO3 in groundwater samples collected from different villages of Mymensingh -1 - district varied from 2.50 to 8.00 me L (Zaman et al., 2001). The concentration of HCO3 ranged from 0.80 to 6.20 me L-1 and this anion was dominant in groundwater as compared to surface water in Tongi aquifer under Gazipur district (Sen et al., 2000). The 2- - concentrations of CO3 and HCO3 in groundwater samples ranged from 0.05 to 1.50 and 0.60 to 3.50 me L-1, respectively (Hoque, 2000).

2- Jesmin (2000) observed that in Gaibandha aquifers, the amount of CO3 groundwater - samples was not detected groundwater samples and HCO3 concentration was within the range of 1.50 to 6.00 me L-1. Siddique (2000) carried out an experiment by collecting from Lower Atrai Basin and found that only 3 samples contained small amount of carbonate 2- -1 - (CO3 = 0.50 - 0.80 me L ) and HCO3 content of all groundwater samples ranged from 0.50 -1 2- to 5.50 me L . In Madhupur Tract, the concentration of CO3 in water varied from trace to -1 -2 -1 2.00 me L and HCO3 content ranged from 0.50 to 8.00 me L (Nizam et al., 1999).

2.10 Groundwater quality on the basis of phosphate

Khanam (2009) observed that the concentration of phosphate in groundwater samples collected from 4 union of Atpara upazila under the district of Netrokona ranged from 0.005 -1 to 0.290 mg L . Rahman (2007) found that groundwater samples collected from 4 unions of sherpur upazila under Bogra district contained phosphate ranging from trace to 2.19 mg L-1. Rahman et al. (2006) recorded that the content of phosphate in groundwater samples collected from 5 unions under Atrai upazila of Naogaon district varied from trace to 59.4 mg L-1. The concentration of phosphate in groundwater samples collected from 3 districts namely Sherpur, Gaibanda and Naogaon ranged from trace to 0.144 mg L-1 (Rahman et al., 2005). The content of phosphate in groundwater samples collected from different villages of Mymensingh district varied from trace to 0.20 mg L-1. Zaman et al. (2001) found that the concentration of phosphate ranged from trace to 0.05 mg L-1 and this anion was dominant in groundwater as compared to surface water in Tongi aquifer under Gazipur district (Sen et al., 2000). Jesmin (2000) observed that in Gaibandha aquifers, the amount of phosphate in all groundwater samples ranged from (trace to 1.10 mg L-1). Siddique (2000) carried out an experiment by collecting groundwater samples from Lower Atrai Basin and found that the content of phosphate varied from trace to 2.19 mg L-1. Nizam et al. (1999) reported that phosphate content of groundwater samples collected from Bhaluka upazila under Mymensingh district varied from 0.001 to 0.012 mg L-1. Helaluddin (1996) analyzed 88 groundwater samples of Khagrachari district and found that the content of phosphate ranged from trace to 0.11 mg L-1. Groundwater samples of Madhupur under Tangail district contained phosphate within the limit from 0.02 to 0.09 mg L-1 (Zaman and Majid, 1995). Inverarity et al. (1983) measured some groundwater samples collected in two seasons from Great Britain and reported that concentration of phosphate varied from 0.01 to 0.02 mg L-1.

2.11 Groundwater quality on the basis of sulphate and chloride

The concentrations of sulphate and chloride in groundwater samples collected from 6 unions of sadar upazila under the district of Faridpur were within the limit from 0.09 to 13.61 mg -1 with average of 1.30 mg L-1 and 0.10 to 0.28 me L-1 with the mean value of 0.18 me L-1, respectively (Shaik, 2010). Khanam (2009) reported that in all groundwater samples 2- - collected from 4 unions of Atpara upazila under the district of Netrakona area, SO4 and Cl contents varied from 0.10 to 2.83 mg L-1 with the mean value of 1.03 mg L-1 and 0.10 to 0.60 me L-1 with the mean value of 0.30 me L-1, respectively. Shaik (2009) reported that in all the groundwater samples collected from Madhukhali upazila under Faridpur district 2- - -1 area, SO4 and Cl contents varied from 0.10 to 5.40 mg L with the mean value of 1.68 mg L-1 and 0.28 to 1.25 me L-1 with the mean value of 0.59 me L-1, respectively. The 2- - concentrations of SO4 and Cl in groundwater samples collected from four unions of Sherpur upazila under Bogra district ranged from 0.14 to 10.30 mg L-1 and 0.40 to 1.80 me L- 1, respectively (Rahman et al., 2007). Chowdhury (2007) revealed that the concentrations of -2 SO4 and Cl in groundwater samples collected from three unions of sadar upazila under Rangpur district area ranged from 0.02 to 9.30 mg L-1 and 0.20 to 1.49 me L-1, respectively.

2- - Monem (2007) reported that the concentrations of SO4 and Cl in groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari were within the limit of 0.25 to 7.90 mg L-1 and 0.21 to 0.92 me L-1, respectively. A study was conducted by Rahman and Rahman (2006) at 5 unions of Atrai upazila under Naogaon 2- -1 -1 district and found that the concentrations of SO4 and Cl ranged from 1.40 to 12.00 mg L -1 2- - and 0.80 to 2.20 me L , respectively. The contents of SO4 and Cl in groundwater samples of sadar upazila under Sherpur district, sadar upazila under Gaibandha district and Atrai upazila under Naogaon district varied from 1.9 to 59.4 mg L-1 and 0.20 to 4.59 me L-1, 2- respectively (Rahman et al., 2005). Ahsan (2004) reported that the concentrations of SO4

and Cl- in groundwater samples of Sylhet division were found within the range of 0.01 to -1 -1 2- 18.00 mg L and 0.40 to 156.70 mg L , respectively. Arefin (2002) reported that SO4 and Cl- contents of groundwater samples of Pabna sadar aquifers varied from 0.14 to 5.48 mg L-1 and 0.80 to 4.80 me L-1.

Sen et al. (2000) found that groundwater samples in Tongi aquifers under the district of 2- -1 - Gazipur contained SO4 within the limit of trace to 11.00 mg L and also contained Cl -1 2- ranging from 0.80 to 4.80 me L . In all groundwater samples, SO4 content varied from trace to 61.00 mg L-1 and Cl- content ranged from 0.50 to 7.60 me L-1 at Gaibandha aquifers (Jesmin, 2000). Rahman (2000) conducted an experiment for assessing groundwater quality in Lower Atrai 2- - -1 Basin and reported that SO4 and Cl contents ranged from trace to 0.40 mg L and 0.40 to 2.20 me L-1, respectively. Mitra and Gupta (1999) reported that Cl- content of tubewell water used for irrigation during monsoon and winter seasons were 45.6 and 55.2 mg L-1, respectively. Hossain and Ahmed (1999) stated that concentration of Cl- in groundwater samples of Muktagacha aquifers ranged from 0.20 to 0.70 me L-1 having the mean value of 0.44 me L-1. Islam et al. (1998) recorded Cl- content within the range of 21.30 to 85.20 me L-1 in most of the groundwater samples collected - 2- from city. Alamgir et al. (1999) reported that the concentrations of Cl and SO4 in groundwater of Madhupuer Tract were within the limit of 8.50 to 5.10 me L-1 and 14.50 to 40.40 mg L-1, respectively.

2.12 Groundwater quality on the basis of hardness

Shaik (2010) observed that the hardness of groundwater samples collected from 6 unions of sadar upazila under the district of Faridpur were within the range of 100.18 to 285.98 mg L-1 with average of 147.65 mg L-1. Khanam (2009) computed that the hardness of groundwater samples collected from 4 unions of Atpara upazila under the district of Netrakona area ranged from 68.34 to 511.04 mg L-1 with the mean value of 265.32 mg L-1. Shaik (2009)

calculated that the hardness of all samples collected from Madhukhali upazila under Faridpur district varied from 54.60 to 255.30 mg L-1 with the mean value of 135.84 mg L-1 reflecting soft to hard classes. Chowdhury (2007) reported that the hardness value in groundwater samples collected from three unions of sadar upazila under Rangpur district ranged from 20.61 to 235.15 mg L-1. Monem (2007) revealed that the hardness values of all groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari were within the limit of 35.05 to 99.84 mg L-1 reflecting soft to medium hard classes. Rahman et al. (2007) observed that the hardness (HT) values of groundwater samples in four unions of Sherpur upazila under Bogra district ranged from 129.90 to -1 259.60 mg L showing moderately hard to hard classes. The hardness (HT) values of groundwater samples collected from five unions under Atrai upazila of Naogaon district varied from 139.6 to 299.5 mg L-1 indicating moderately hard to hard classes (Rahman et al., 2006).

Hardness values of groundwater of sadar upazila under Sherpur district, sadar upazila under Gaibandha district and Atrai upazila under Naogaon district ranged from 70.0 to 454.2 mg L- 1 revealing soft to very hard quality (Rahman et al., 2005). Ahsan (2004) stated that the hardness values of groundwater samples ranged from 3.71 to 322.35 mg L-1 in different districts of Sylhet division. Zaman et al. (2001) assessed the hardness values in different villages of Dakatia and Kachina unions under Mymensingh district ranged from 34.97 to 259.52 mg L-1. Hoque (2000) revealed that hardness values of groundwater collected from sadar upazila under the district of Sherpur ranged from 36.96 to 159.91 mg L-1. Jesmin (2000) found that in 55 groundwater samples collected from Gaibandha aquifers, the -1 hardness (HT) was within the limit of 109.64 to 459.24 mg L showing moderately hard to very hard in quality. Rahman (2000) stated that the hardness values of groundwater samples ranged from 64.90 to 299.49 mg L-1 in Lower Atrai Basin. In groundwater samples collected from 11 unions of Bhaluka upazila under Madhupur Tract, the hardness of groundwater samples ranged from 29.94 to 304.39 mg L-1 indicating soft to very hard water in category (Nizam et al., 1999).

2.13 Groundwater quality on the basis of sodium adsorption ratio

Shaik (2010) found that sodium adsorption ratio (SAR) of groundwater samples collected from 6 unions of sadar upazila under the district of Faridpur was within the range of 0.45 to 1.25 with the mean value of 0.76. Khanam (2009) calculated that sodium adsorption ratio (SAR) of groundwater samples collected from 4 unions of Atpara upazila under the district of Netrakona ranged from 0.16 to 0.68 with the mean value of 0.36. Shaik (2009) calculated sodium adsorption ratio of groundwater samples collected from Madhukhali upazila under Faridpur district area ranging from 0.05 to 1.08 with the mean value of 0.38. Chowdhury (2007) stated that the values of SAR in groundwater samples collected from three unions of Sadar upazila under Rangpur district ranged from 0.37 to 3.29. Monem (2007) revealed that the values of SAR of all groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari area were within the limit of 0.10 to 0.95.

SAR values of groundwater samples collected from four unions of Sherpur upazila under Bogra district ranged from 0.07 to 0.90 (Rahman et al., 2007). SAR values of groundwater samples collected from five unions under Atrai upazila of Naogaon district varied from 0.41 to 0.90 (Rahman et al., 2006). SAR values of groundwater samples collected from three districts namely Sherpur, Gaibanda and Naogaon ranged from 0.15 to 2.00 (Rahman et al., 2005). Ahsan (2004) found that SAR values of groundwater collected from different areas of Sylhet division varied from 0.082 to 35.79. SAR values in groundwater samples of sadar upazila under the district of Pabna varied from 0.38 to 1.05 (Arefin, 2002). SAR values of groundwater samples collected from different villages of Mymensingh district varied from 0.13 to 0.29 (Zaman et al., 2001). Hoque (2000) analyzed groundwater samples of sadar upazila under the district of Sherpur and found that SAR values ranged from 0.07 to 2.69 reflecting low alkalinity hazard (S1). The values of SAR varied from 0.12 to 0.89 in groundwater samples of Lower Atrai Basin in Naogaon district (Siddique, 2000).

2.14 Groundwater quality on the basis of soluble sodium percentage

Shaik (2010) observed that soluble sodium percentage (SSP) value of groundwater samples collected from 6 unions of sadar upazila under the district of Faridpur was within the range of 26.60 to 53.77% with average of 36.95%. Khanam (2009) calculated that SSP values of groundwater samples collected from 4 unions of Atpara upazila under the district of Netrokona varied from 4.51 to 27.12% with the mean value of 12.39%. Shaik (2009) reported that SSP values of all groundwater samples collected from Madhukhali upazila under Faridpur district area varied from 6.36 to 45.27% with the mean value of 21.79%. Chowdhury (2007) stated that SSP value in groundwater samples collected from three unions of sadar upazila under Rangpur district ranged from 18.90 to 78.20%. Monem (2007) revealed that SSP value of all groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari was within the limit of 9.23 to 32.88% with the mean value of 17.65%. Rahman and Rahman (2007) observed that SSP values of groundwater samples collected from 4 unions of Sherpur upazila under Bogra district ranged from 5.3 to 30.5%.

An investigation was conducted by Rahman and Rahman (2006) at 5 unions of Atrai upazila under Naogaon district and found that SSP values ranged from 9.5 to 34.9%. SSP values of groundwater samples collected from sadar upazila under Sherpur district, sadar upazila under Gaibandha district and Atrai upazila under Naogaon district ranged from 8.7 to 51.0% (Rahman et al., 2005). Ahsan (2004) found that SSP values of groundwater samples collected from different districts of Sylhet division ranged from 6.43 to 98.61%. Zaman et al. (2001) assessed SSP values of groundwater in different villages of Dakatia and Kachina unions under Mymensingh district and found that SSP values ranged from 4.54 to 13.17%. Nizam et al. (1999) reported that SSP values of groundwater samples collected from 11 unions of Bhaluka upazila under Mymensingh district ranged from 2.38 to 17.41%. In Gaibandha aquifers, SSP values of groundwater samples varied from 9.20 to 45.75% and all samples under test were excellent, good and permissible classes (Jesmin, 2000).

2.15 Groundwater quality on the basis of residual sodium carbonate

Residual sodium carbonate (RSC) of groundwater samples collected from 6 unions of sadar upazila under the district of Faridpur was within the limit of -2.08 to 1.11 me L-1 (Shaik, 2010). Khanam (2009) computed that RSC value of groundwater samples collected from 4 unions of Atpara upazila under the district of Netrokona area ranged from -6.54 to 1.91 me L-1. Shaik (2009) calculated RSC values of groundwater samples collected from Madhukhali upazila under Faridpur district and the values ranged from -4.10 to 3.25 me L-1. Chowdhury (2007) calculated RSC value in groundwater samples collected from three unions of Rangpur sadar upazila under Rangpur district and obtained that RSC values varied from -0.02 to 1.08 me L-1. An investigation was conducted by Monem (2007) which revealed that RSC value in groundwater samples collected from four unions of Kishoreganj upazila under the district of Nilphamari was within the limit of-1.39 to 2.51 me L-1. RSC values of groundwater samples collected from four unions of Sherpur upazila under Bogra district ranged from 1.40 to 0.40 me L-1 (Rahman et al., 2007).

RSC values of groundwater samples collected from five unions under Atrai upazila of Naogaon district varied from -1.80 to 0.30 me L-1 (Rahman et al., 2006). RSC values of groundwater samples collected from three districts namely Sherpur, Gaibanda and Naogaon ranged from -4.20 to 0.90 me L-1 (Rahman et al., 2005). Arefin (2002) reported that RSC varied from -1.8 to 0.10 me L-1 in groundwater samples of sadar upazila under the district of Pabna. Siddique (2000) reported that in all groundwater samples collected from Lower Atrai Basin, RSC values varied from -1.80 to 0.15 me L-1 and these water samples were rated as suitable and marginal classes. Hoque (2000) analyzed groundwater samples of Sherpur sadar under Sherpur district and reported that RSC values ranged from -1.10 to -

0.10 and 0.00 to 1.90 me L-1showing suitable and marginal water classes. Nizam et al. (1999) stated that in groundwater samples collected from Madhupur Tract, RSC values fluctuated between -0.30 to 5.8 me L-1 and these water samples were suitable and unsuitable classes. Lal et al. (1998) carried out an experiment with 173 groundwater samples collected from different locations of Bikaner district of Rajasthan Pradesh in India to evaluate its suitability for irrigation and reported that 75.70, 21.20 and 3.00% samples contained <2.50, 2.50 to 5.00 and >5.00 mmol L-1 RSC, respectively.

CHAPTER - 3

MATERIALS AND METHODS

Water is a universal solvent and different types of ions or elements are dissolved in it. The concentration of a particular element beyond the tolerance limit for specific use is treated as pollutant or toxicant. Water samples for quality assessment were collected from three unions of Gangachara upazila under the district of Rangpur. The chemical analyses included pH, electrical conductivity (EC), total dissolved solids (TDS) and major ionic constituents like

Ca, Mg, K, Na, Mn, Fe, B, PO4, CO3, HCO3, SO4 and Cl.

3.1 Collection and preparation of groundwater samples

Groundwater sampling sites consisted of three unions of Gangachara upazila under the district of Rangpur. Exactly 30 groundwater samples were randomly collected to cover most of the investigated area during 15 March to 20 April, 2011 following the sampling techniques as outlined by Hunt and Wilson (1986) and APHA (2005). The detailed sampling sites of groundwater used for irrigation usage have been presented in Fig. 3.1. The information regarding groundwater sampling sites has been reported in Table 3.1. All groundwater samples were collected in 1 L plastic bottle previously washed with distilled water and sealed immediately to avoid air exposure. Groundwater samples were collected at running conditions of shallow tube well after pumping sufficient quantity of water. During groundwater sampling, all water samples were colorless, odorless, tasteless and also free from turbidity. Samples were brought to the Postgraduate Laboratory of Department of Agricultural Chemistry for testing and were kept in a clean, cool and dry place. Groundwater samples were filtered through filter paper (Whatman No. 1) to remove undesirable solids and suspended materials before chemical analysis. The chemical analyses of groundwater samples were performed as soon as possible on arrival at laboratory.

•27 Study area •26 •23 •30 •24 •22 •25 •28

•29

•12 •3 •13 •11 •16 •1 •18 •14 •7 •17 •20 •2 •4 •10 •15 •6 •19 •5 •21 •8 •9

Fig. 3.1 Goundwater sampling sites of Gangachara upazila under Rangpur district.

Table 3.1 Detailed information of groundwater (shallow tube well) sampling sites

Sampling sites Depth of Duration of Sample Well usage No. Union Village (m) ( yrs)

1 Gangachara 9 8 2 Dhamur 11 9 3 Chandmari 22 7 4 Taraziniamat 23 3 5 Nogunidas 25 4 Gangachara 6 Khutipara 29 9 7 Moulavibazar 25 3 8 Poshim Nobonidas 28 8 9 Nilkandhi 25 3 10 Vukta 22 7 11 Barabeel 23 10 12 Monthana 21 5 13 Pakuria 25 5 14 Bagpur 27 7 15 Uttar panapukur 30 25 16 Barabil Dokkhin panapukur 25 20 17 Kumarpara 22 5 18 Fokirtari 30 4 19 Malikerbazar 23 4 20 Chotapara 31 25 21 Bullaiabeel 32 5 22 Kolkonda uttar 30 2 23 Kolkonda Kolkonda dokkhin 30 2 24 Alekishamat 30 1

25 Uribisha 32 2 26 Motukpur 25 11 27 Chilakhal 32 11 28 Bondina 30 5 29 Masterpara 31 8 30 Kuthipara 24 7

3.2 Analytical techniques

The major chemical constituents of groundwater and its quality factors were considered for analyses as follows:

1) pH 2) Electrical Conductivity (EC) 3) Total Dissolved Solids (TDS) 4) Ionic Constituents i. Calcium ii. Magnesium iii. Potassium iv. Sodium v. Iron vi. Manganese vii. Boron viii. Carbonate ix. Bicarbonate x. Sulphate xi. Phosphate xii. Chloride

The chemical analyses of groundwater samples were performed in the Departmental Laboratory of Agricultural Chemistry and Professor Muhammad Hussain Central Laboratory of Bangladesh Agricultural University, Mymensingh and Soil Resource Development Institute (SRDI), Dhaka.

3.2.1 pH pH values of water samples were determined by taking 50 mL groundwater in a beaker and then placing the electrode of the pH meter (Model: WTW pH 522) into water samples as mentioned by Singh et al. (1999).

3.2.2 Electrical conductivity

Electrical conductivity (EC) of water was measured by taking 100 mL groundwater samples in a beaker and then immersing the electrode of conductivity meter (Model: WTW LF 521) into water sample (Ghosh et al., 1983).

3.2.3 Total dissolved solids

Total dissolved solids (TDS) were measured by evaporating 100 mL groundwater sample to dryness and then were weighed following the method as described by Chopra and Kanwar (1980).

3.2.4 Ionic constituents

3.2.4.1 Calcium

Calcium content of groundwater samples was determined by EDTA titrimetric method at pH 12 in the presence of calcon indicator. Exactly 25 mL water sample was taken in 250 mL conical flask followed by the addition of 25 mL distilled water, 3 mL NaOH solution and 10 drops each of masking agents such as hydroxylamine hydrochloride, potassium ferrocyanide and triethanol amine. After the addition of 5 drops of calcon indicator solution, water sample was titrated against Na2-EDTA (0.01M) solution from a burette until pink color completely turned to blue color. This analytical technique was described by Page et al. (1982) and Singh et al. (1999).

3.2.4.2 Magnesium

The concentration of magnesium in groundwater samples was determined by EDTA titrimetric method at pH 10 in the presence of eriochrome black T (EBT) indicator (Page et al., 1982; Singh et al., 1999). Exactly 25 mL water sample was taken in 250 mL conical flask followed by the addition 25 mL distilled water, 5 mL NH3-NH4 buffer solution and 10 drops each of masking agents like sodium tungstate, hydroxylamine hydrochloride, potassium ferrocyanide and triethanolamine . After the addition of 5 drops of EBT indicator solution, the sample was titrated against Na2-EDTA (0.01M) solution from burette until pink color completely turned to blue color.

3.2.4.3 Potassium and sodium

The contents of potassium and sodium were analysed from groundwater samples separately by flame photometric method using potassium and sodium filters, respectively. Water sample was aspirated into a flame and the intensity of light emitted by K at 766 nm or Na at 589 nm wavelengths was directly proportional to the concentration of these ions present in groundwater samples, respectively. The per cent of emissions was recorded following the method as stated by Golterman (1971) and Ghosh et al. (1983).

3.2.4.4 Iron and manganese

The concentrations of iron and manganese were analysed by atomic absorption spectrophotometer (Model: HITACHI, Z-2300) at the wavelengths of 248.3 and 279.5 nm, respectively following the procedure as described by APHA (2005).

3.2.4.5 Boron

The content of B in groundwater samples was determined by spectrophotometric method using azomethine-H as the reagent to form a stable colored complex at pH 5.1 in aqueous media. Exactly 20 mL groundwater was taken in a 25 mL volumetric flask. Then, 4 mL buffer solution and 4 mL azomethine-H reagent were added to water sample. The absorbance was read at 420 nm wavelength after 30 minutes using spectrophotometer (Model: Labtronics LT- 31) as outlined by Tandon (1995).

3.2.4.6 Carbonate

The content of carbonate in groundwater samples was estimated by acidimetric titration using phenolphthalein as indicator. Exactly 25 mL water sample was taken in a clean porcelain dish followed by the addition of 25 mL distilled water and 2-3 drops phenolphthalein. The formation of red color indicated the presence of carbonate then the titration was continued with standard sulphuric acid till red color disappeared. This titrimetric analysis was done according to the procedure as mentioned by Tandon (1995).

3.2.4.7 Bicarbonate

Bicarbonate content of groundwater samples was analysed by acidimetric titration using methyl orange as indicator. Exactly 25 mL water sample was taken in a porcelain dish followed by the addition of 25 mL distilled water. Then, 2-3 drops methyl orange was added in this solution and it was titrated with standard sulphuric acid till the yellow color changed into rosy red following the method as described by Ghosh et al. (1983) and Tandon (1995).

3.2.4.8 Sulphate

Sulphate content of groundwater samples was determind turbidimetrically. Exactly 10 mL water sample was taken in a 25 mL volumetric flask followed by the addition of 10 mL sodium acetate-acetic acid buffer solution, 1 mL gum acacia and 1 g barium chloride crystal. After uniform mixing, it was allowed to stand for 30 minutes. The color intensity was measured at 425 nm wavelength with the help of a spectrophotometer (Model: Labtronics LT-31) following the analytical method of Tandon (1995).

3.2.4.9 Phosphate

The concentration of phosphate in groundwater samples was determined by colorimetric method as per Jackson (1973). In this method, stannous chloride was used as a reducing agent which developed molybdophosphate blue color. Exactly 50 mL groundwater sample was taken in a 100 mL volumetric flask followed by the addition of 4 mL sulphomolybdic acid and 5 drops stannous chloride solution. The color intensity was measured at 660 nm wavelength with the help of a spectophotometer (Model: Labtronics LT-31) within 15 minutes after the addition of stannous chloride.

3.2.4.10 Chloride

Chloride concentration of groundwater sample was estimated by argentometric method of titration (Tandon, 1995 and APHA, 2005). Exactly 25 mL groundwater sample was taken in a porcelain dish followed by the addition of 5 to 6 drops potassium chromate as indicator. The test sample was titrated against silver nitrate (0.02N) solution. In neutral or slightly alkaline solution (pH=7-10), silver chloride (AgCI) was quantitatively precipitated before red silver chromate was formed.

3.3 Evaluation of ionic toxicity of groundwater

The concentrations of major ions present in groundwater samples affect water quality. The following water quality factors were considered in assessing ionic toxicity groundwater by the interpretation of analytical result:

i) Sodium adsorption ratio (SAR)

Na  SAR= Ca 2  Mg2 2

ii) Soluble sodium percentage (SSP)

Na   K SSP = 100 Ca 2  Mg2  Na   K

iii) Residual sodium carbonate (RSC)

2- - 2+ 2+ RSC = (CO3 + HCO3 ) – (Ca + Mg )

iv) Hardness (HT)

2+ 2+ HT = 2.5 × Ca + 4.1 × Mg

Whereas, all ionic concentrations were expressed as me L-1 but in case of hardness, cationic concentrations were expressed as mg L-1.

3.4 Statistical analyses

The statistical analyses of the analytical results obtained from groundwater samples were performed (Gomez and Gomez, 1984). Correlation studies were also done following the standard method of Computer Programme (SPSS).

CHAPTER - 4

RESULTS AND DISCUSSION

The major ionic constituents of groundwater samples collected from three unions of Gangachara upazila under the district of Rangpur were analyzed and the results obtained from chemical analyses have been described in this chapter. In the collected samples, ionic constituents such as Ca, Mg, Na, K, Fe, Mn, BO3, PO4, SO4 HCO3 and Cl were analyzed and these elements were present in variable amounts in the collected groundwater samples. The salient features of the experimental findings have been discussed in the foregoing chapter under appropriate headings in the light and support of relevant available research findings whenever applicable in the following sequences:

4.1 Assessment of ionic toxicity of groundwater for irrigation

4.1.1 pH pH values of all groundwater samples ranged from 6.01 to 7.00 reflecting slightly acidic to neutral in nature (Table 4.1). These might be due to the presence of major ions in water (Rao et al., 1982). According to Ayers and Westcot (1985), the acceptable pH range for irrigation water is from 6.0 to 8.4. The measured pH of all groundwater samples did not exceed this acceptable range. As per this limit, these water samples might not be harmful for successful crop production.

4.1.2 Electrical conductivity

Electrical conductivity (EC) values of all groundwater samples were within the limit of 110 to 748 µS cm-1 with the mean value of 293.27 µS cm-1 (Table 4.1). EC values of 22 samples were less than the mean value and the rest 8 samples were higher than the average value. According to Richards (1968) as illustrated in Fig. 4.1, 15 water samples under test were rated as low salinity (C1, EC<250 µS cm-1) and 15 samples were classified as medium salinity (C2, EC = 250-750 µS cm-1) water classes. Considering EC, groundwater of low salinity class could be used for irrigation purpose without harmful impacts on soils and groundwater of medium salinity could be safely used for moderate salt tolerance crops growing on soils with moderate level of permeability and leaching.

4.1.3 Total dissolved solids

The measured total dissolved solids (TDS) of groundwater samples in the investigated area varied from 39.00 to 396.00 mg L-1 with mean value of 126.73 mg L-1 (Table 4.1). Out of 30 samples, TDS values of 20 samples were found below the mean value and the remaining 10 samples were found above the average value. The computed standard deviation (SD) and co-efficient of variation were 78.71 and 62.11%, respectively. A sufficient quality of bicarbonate, sulphate and chloride of Ca, Mg and Na caused high TDS values (Karanth, 1994). According to Freeze and Cherry (1979) as reported in Appendix 2, all water samples under investigation contained less than 1000 mg L-1 TDS and were classified as fresh water in quality. These waters would not affect the osmotic pressure of soil solution and cell sap of the plants when applied to soil as irrigation water. The results on TDS in water quality corroborated the findings of Bikash et al. (2000) and Rahman et al. (2005).

4.2 Ionic constituents

In the present study, major ions like Ca, Mg, K, Na, HCO3 and Cl were found in significant quantities but the remaining detected ions were also recorded in minor amounts in the collected groundwater samples. The detected amounts of these ions present in all samples in relation to groundwater quality for irrigation have been discussed as follows:

4.2.1 Calcium

The concentration of Ca in water samples was found within the range of 0.75 to 3.31 me L-1 with the average value of 1.75 me L-1 (Table 4.2). Out of 30 samples, 13 samples were found above the mean value and 17 were below the average concentration. The standard deviation (SD) and co-efficient of variation (CV) were 0.34 and 19.43%, respectively. The contribution of Ca content in water was largely dependent on the solubility of CaCO3, CaSO4 -1 and rarely on CaCl2 (Karanth, 1994). Irrigation water containing less than 20 me L Ca was suitable for irrigating crop plants (Ayers and Westcot, 1985). On the basis this ion content, all water samples could safely be used for irrigation and would not affect soil system.

Table 4.1 pH, EC, TDS and anionic constituent of groundwater samples

EC TDS BO3 PO4 SO4 HCO3 Cl Sl. No. pH -1 µS cm ------mg L-1 ------me L-1 ---

1 6.01 606 304 0.12 0.06 4.21 1.20 1.69 2 6.01 392 184 0.07 0.91 0.41 1.60 1.90 3 6.05 399 188 0.09 0.03 0.12 1.60 1.24 4 6.04 452 218 0.09 0.03 6.83 1.40 0.22 5 6.19 748 396 0.07 0.05 7.45 1.00 1.18 6 6.06 450 92 0.15 0.04 0.62 1.00 0.23 7 6.02 530 56 0.08 0.05 0.14 1.80 0.32 8 6.18 380 151 0.07 0.08 0.12 0.80 0.98 9 6.05 370 105 0.12 0.81 2.03 1.10 0.20 10 6.80 405 140 0.88 0.53 8.08 1.60 0.22 11 7.00 148 67 0.06 0.52 Trace 1.20 0.33

12 6.63 180 83 0.09 0.10 Trace 1.40 0.22 13 6.53 145 58 0.08 Trace Trace 1.20 0.98 14 6.80 135 57 0.07 0.01 4.43 0.80 0.39 15 6.56 145 66 0.07 Trace Trace 1.40 0.39 16 6.01 349 166 0.06 0.11 6.4 1.60 0.45 17 6.90 150 78 0.08 Trace 4.43 1.80 0.82 18 6.91 165 56 0.06 0.12 6.40 1.60 0.75 19 6.66 170 73 0.07 0.01 Trace 1.00 1.29 20 6.70 162 92 0.06 Trace Trace 1.60 1.28 21 6.13 110 39 0.08 Trace Trace 1.40 0.33 22 6.01 237 110 0.08 0.01 1.94 0.80 0.90 23 6.04 269 125 0.08 Trace 4.28 1.60 1.07 24 6.20 230 121 0.08 0.01 2.38 1.40 1.07 25 6.20 233 110 0.08 Trace 3.62 1.20 0.78 26 6.01 250 124 0.05 0.44 1.80 1.00 1.01 27 6.11 255 185 0.06 0.48 1.94 1.80 0.90 28 6.21 263 190 0.05 Trace 2.34 1.80 0.82 29 6.25 220 54 0.07 0.01 1.73 0.90 0.33 30 6.28 260 114 0.05 0.23 1.83 0.80 0.90 Min. 6.01 110 39 0.05 Trace Trace 0.80 0.20

Max. 7.00 748 396 0.88 0.91 8.08 1.80 1.90

Mean 293.27 126.73 0.10 0.15 3.20 1.31 0.77 SD 156.25 78.71 0.15 0.25 2.56 0.34 0.46 CV (%) 187.69 62.11 150.00 166.67 104.49 25.95 59.74

Table 4.2 Cationic constituent of groundwater samples

Sl. Ca Mg K Na Fe Mn No. -1 -1 ------me L ------mg L ------

1 2.51 1.72 1.11 1.94 0.03 Trace 2 2.11 1.28 0.69 0.99 0.02 0.70 3 1.95 1.32 0.80 1.07 0.02 0.50 4 3.31 2.16 0.75 2.20 0.02 Trace 5 2.91 2.16 0.24 0.84 0.02 Trace 6 1.83 1.28 0.73 0.84 0.02 0.11 7 2.83 1.32 0.83 0.73 0.03 Trace 8 2.53 1.72 0.59 1.07 0.03 0.09 9 1.90 1.83 0.63 0.99 0.02 0.17 10 2.83 0.97 1.12 1.83 0.03 0.02 11 1.71 1.28 0.01 0.49 0.02 Trace 12 1.23 0.80 0.01 0.61 0.02 0.04 13 0.83 0.84 0.01 0.53 0.02 Trace 14 0.99 0.93 0.01 0.48 0.02 Trace 15 0.75 0.80 0.01 0.51 0.03 Trace 16 1.55 1.12 0.51 1.03 0.03 0.04 17 0.75 0.73 0.43 1.52 0.03 Trace 18 1.55 1.83 0.44 0.52 0.03 0.02 19 0.98 0.99 0.25 0.63 0.03 Trace 20 1.07 0.80 0.51 0.66 0.03 Trace 21 1.47 0.72 0.06 0.23 0.03 Trace 22 1.47 1.04 0.31 0.78 0.02 0.05 23 1.55 1.12 0.18 0.72 0.03 Trace 24 1.39 1.04 0.98 0.83 0.03 Trace 25 1.07 0.80 0.33 0.68 0.03 Trace 26 1.31 0.88 0.17 0.96 0.03 Trace 27 1.98 0.94 0.34 0.73 0.03 Trace 28 1.88 1.23 0.17 0.83 0.03 Trace 29 2.34 0.88 0.18 0.98 0.03 Trace 30 1.83 0.73 0.06 0.73 0.03 Trace Max. 0.75 0.72 0.01 0.23 Trace Trace

Min. 3.31 2.16 1.12 2.20 0.03 0.70

Mean 1.75 1.18 0.42 0.90 0.03 0.17 SD 0.34 0.42 0.34 0.45 0.01 0.15 CV (%) 19.43 35.59 80.95 50.00 33.33 88.82

4.2.2 Magnesium

In groundwater samples collected from Gangachara upazila under Rangpur district, the amount of Mg was detected within the range of 0.72 to 2.16 me L-1 with the average value of 1.18 me L-1 (Table 4.2). Out of 30 samples, 19 samples were found below the average value and the rest 11 samples were recorded above the average value. The calculated standard deviation (SD) and co-efficient of variation (CV) were 0.42 and 35.59%, respectively. According to Ayers and Westcot (1985), irrigation water contains less than 5.0 me L-1 Mg. In the study area, not a single sample exceeded this limit (Table 4.2). Therefore, all groundwater samples were suitable for irrigation considering Mg content.

4.2.3 Potassium

Potassium content of all groundwater samples was within the range of 0.01 to 1.12 with the mean value of 0.42 me L-1 (Table 4.2). Out of 30 water samples, 14 were lower than the mean value and 16 samples were higher than the mean value. The standard deviation (SD) and co-efficient of variation (CV) were 0.34 and 80.95%, respectively (Table 4.2). The presence of lower quantity of K in some water samples might be due to some potash bearing minerals like sylvite (KCI) and nitre (KNO3) in the aquifers (Karanth, 1994). The recorded quantity of K in the collected water samples had no significant influence on water quality for irrigation.

4.2.4 Sodium

The content of Na in the groundwater samples was within the range of 0.23 to 2.20 me L-1 with the mean value of 0.90 me L-1 (Table 4.2). Out of 30 samples, 19 samples were lower than the average value and the rest 11 samples were higher than the average value. The respective standard deviation (SD) and co-efficient of variation (CV) were 0.45 and 50%, respectively. Water generally contained less than 40 me L-1 Na (Ayers and Westcot, 1985). The recorded content of Na in all groundwater samples under investigation was far below this acceptable limit. Considering the content of this ion, all samples of the study area could safely be used for long-term irrigation without harmful effect on soils and crops.

4.2.5 Iron

The concentration of Fe in all groundwater samples was within the limit of 0.02 to 0.03 mg L-1 with the mean value of 0.03 mg L-1 (Table 4.2). Out of 30 samples, 11 samples were less than the mean value and 19 samples were higher than the mean value. The standard deviation (SD) and co-efficient of variation (CV) were 0.01 and 33.33%, respectively (Table 4.2). Therefore, Fe content of all groundwater samples in the study area was detected below the permissible limit (5.0 mg L-1) as shown in Appendix 7 and might be safely used for irrigation purpose.

4.2.6 Manganese

Groundwater samples of the investigated area contained Mn in fluctuating from trace to 0.70 mg L-1 with average value of 0.17 mg L-1 (Table 4.2). Out of 30 samples, 2 samples indicated higher than the average value and 28 samples were less than the average value. The standard deviation and co-efficient of variation were 0.15 and 88.82%, respectively.

According to Ayers and Westcot (1985), maximum permissible limit of Mn in water used for irrigation is 0.20 mg L-1 (Appendix 7). Considering this limit, Mn content of all groundwater samples except two samples was not hazardous for irrigation purpose. The detected quantity of Mn in 28 samples was observed within the legal limit (0.20 mg L-1) but its content in 2 samples (Sample nos. - 2 and 3) exceeded the acceptable limit and this ion was treated as toxicant for irrigation purpose.

4.2.7 Boron

Boron concentration of all groundwater samples ranged from 0.05 to 0.88 mg L-1 with the mean value of 0.10 mg L-1 (Table 4.1). About 26 samples were less than the mean value and the rest 4 samples were higher than the mean value. The computed standard deviation (SD) and co-efficient of variation (CV) were 0.15 and 150%, respectively. The recommended maximum concentration of B for irrigation water used continuously on soil is less than 0.75 mg L-1 (Ayers and Westcot, 1985) as shown in Appendix 7. As per this acceptable range, B status of the collected groundwater samples was not problematic for irrigating crops.

4.2.8 Carbonate

The amount of carbonate was not detected in all groundwater samples in the study area. This anion was not considered as troublesome for irrigating crops.

4.2.9 Bicarbonate

-1 The concentration of HCO3 ion in all groundwater samples ranged from 0.80 to 1.80 me L with the mean value of 1.31 me L-1 (Table 4.1). Among the 30 samples, 14 samples were below the average value and the rest 16 samples were above the average content of HCO3. The calculated standard deviation (SD) and co-efficient of variation CV) were 0.34 and 25.95%, respectively. Bicarbonate content was recorded comparatively higher among the

ionic constituents. In respect of HCO3 content, 11 water samples were problematic for irrigation because HCO3 content of these water samples exceeded the recommended limit (1.5 me L-1), as reported in Appendix 7.

4.2.10 Phosphate

-1 The concentration of PO4 ion in all groundwater samples ranged from trace to 0.91 mg L with the mean value of 0.15 mg L-1 (Table 4.1). Among the 30 samples, 7 samples were below the average value and the rest 23 samples were above the average content of PO4. The calculated standard deviation (SD) and co-efficient of variation (CV) were 0.25 and

166.67%, respectively. According to Ayers and Westcot (1985), the permissible limit of PO4 in irrigation water is less than 2.00 mg L-1 (Appendix 7). On the basis of this limit, all groundwater samples under investigation were suitable for irrigation without harmful effect on soils and crops grown in the investigated area.

4.2.11 Sulphate

-1 In all groundwater samples, SO4 content varied from trace to 7.45 mg L with the mean value of 3.20 mg L-1 (Table 4.1). Out of 30 samples, 8 samples were below the average value and the rest 22 samples were above the average value. The standard deviation (SD) and co- efficient of variation (CV) were 2.56 and 104.49%, respectively. According to Ayers and -1 Westcot (1985), the acceptable limit of SO4 in irrigation water is less than 20 mg L . On the basis of this limit, all groundwater samples under investigation were not problematic for irrigating soils and crops grown in the study area.

4.2.12 Chloride

Water sample collected from the study area contained Cl ranging from 0.20 to 1.90 me L-1 with the mean value of 0.77 me L-1 (Table 4.2). Out of 30 samples, 14 samples were above the mean value and 16 samples were below the mean value. The standard deviation (SD) and co-efficient of variation (CV) were 0.46 and 59.74, respectively. Chloride content of all water samples was not problematic for irrigation because this detected anionic concentration was below the recommended limit (4.0 me L-1) as mentioned in Appendix 7. Most of the chloride in water was present as sodium chloride (NaCl) but chloride content may exceed sodium due to the base exchange phenomena (Karanth, 1994).

4.3 Groundwater quality determining indices

4.3.1 Sodium adsorption ratio (SAR)

Sodium adsorption ratio of groundwater samples was within the range 0.21 to 1.76 with the mean value of 0.72 (Table 4.3). Out of 30 samples, 11 samples were above the mean value and 19 samples were below the mean value. The standard deviation (SD) and co-efficient of variation (CV) were 0.31 and 43.05%, respectively. The present investigation revealed that a balance proportion of Ca and Mg existed in water which was suitable for good structure and tilth condition of soil. Water used for irrigation with SAR less than 10 might not be harmful for agricultural crops (Todd, 1980). Considering this classification, all samples were excellent for irrigation and rated as low alkalinity hazard (S1) class as per SAR value (Fig. 4.1).

4.3.2 Soluble sodium percentage

Soluble sodium percentage (SSP) value of the collected groundwater samples varied from 11.69 to 56.85% with the mean value of 30.43% (Table 4.3). Among the 30 water samples, 17 samples were below the mean value and the rest 13 samples were higher than the mean

value. The standard deviation (SD) and co-efficient of variation (CV) were 9.71 and 31.91%, respectively. According to water classification proposed by Wilcox (1955), 4 samples were classified as excellent (SSP<20%), 21 samples were rated as good classes (SSP = 21-40%) and the rest 5 samples were graded as permissible classes (SSP = 41-60%) as reported in Appendix 1. In the investigated area, water samples might safely be applied for irrigation without any harmful impact on soils and crops.

4.3.3 Residual sodium carbonate

Residual sodium carbonate (RSC) value as obtained from the data generated out of chemical analyses of groundwater samples ranged from -4.07 to 0.32 me L-1 with mean value of -1.61 me L-1 (Table 4.3). Out of 30 water samples, 15 samples were below the mean value and the rest 15 samples were above the mean value. Among the water samples under test, 29 samples gave negative value and only 1 sample gave positive value of RSC According to Ghosh et al. (1983), 29 water samples were found as suitable class (RSC<1.25 me L-1) 1 and only 1 sample was rated as marginal class (RSC = 1.25 - 2.5 me L-1) as mentioned in Appendix 4. For this reason, all samples might not be problematic for irrigation usage.

4.3.4 Hardness

-1 The calculated hardness (HT) of all groundwater samples varied from 73.97 to 273.51 mg L with the mean value of 145.41 mg L-1 (Table 4.3). Out of the 30 samples, 17 samples were below the mean value and the rest 13 samples were above the mean value. The standard deviation (SD) and co-efficient of variation (CV) were 24.89 and 16.50%, respectively. Sawyer and McCarty (1967) suggested a classification for irrigation water based on hardness as reported in Appendix 5. As per this classification, 1 sample was soft, 16 samples were moderately hard and the rest 13 samples were hard in quality. The hardness indicated the presence of higher amounts of Ca and Mg in groundwater samples (Todd, 1980).

Table 4.3 Quality rating and suitability of groundwater used for irrigation

Water class based on Alkalinity and Sample SSP RSC Hardness salinity hazard SAR -1 -1 5 No. % me L mg L 1 2 3 4 classes SAR SSP RSC HT

1 0.94 41.95 -3.02 211.50 Ex. Per. Suit. Hard C2S1 2 0.76 33.14 -1.79 169.53 Ex. Good Suit. Hard C2S1 3 0.84 36.42 -1.67 163.50 Ex. Good Suit. Hard C2S1 4 1.33 35.03 -4.07 273.51 Ex. Good Suit. Hard C2S1 5 0.53 17.56 -4.07 253.48 Ex. Ex. Suit. Hard C2S1 6 0.67 33.55 -2.11 155.49 Ex. Good Suit. Hard C2S1 7 0.44 42.04 -2.35 207.59 Ex. Per. Suit. Hard C2S1 8 0.73 28.08 -3.45 212.50 Ex. Good Suit. Hard C2S1 9 0.72 30.28 -2.63 186.43 Ex. Good Suit. Hard C2S1 10 1.33 43.70 -2.2 190.14 Ex. Per. Mar. Hard C2S1 11 0.4 14.32 -1.79 149.48 Ex. Ex. Suit. MH C1S1 12 0.43 23.40 -0.63 101.50 Ex. Good Suit. MH C1S1 13 0.58 24.44 -0.47 83.46 Ex. Good Suit. MH C1S1 14 0.49 20.33 -1.12 95.96 Ex. Ex. Suit. MH C1S1 15 0.58 25.12 -0.15 77.46 Ex. Good Suit. MH C1S1 16 0.89 37.01 -1.07 133.49 Ex. Good Suit. MH C2S1 17 1.76 56.85 0.32 73.97 Ex. Per. Mar. Soft C1S1 18 0.4 22.11 -1.78 168.89 Ex. Good Suit. Hard C1S1 19 0.63 30.88 -0.97 98.46 Ex. Good Suit. MH C1S1 20 0.68 38.48 -0.27 93.49 Ex. Good Suit. MH C1S1 21 0.21 11.69 -0.79 109.54 Ex. Ex. Suit. MH C1S1 22 0.69 30.28 -1.71 110.47 Ex. Good Suit. MH C1S1 23 0.62 25.20 -1.07 133.49 Ex. Good Suit. MH C2S1 24 0.75 42.69 -1.03 121.49 Ex. Per. Suit. MH C1S1 25 0.7 35.07 -0.67 93.49 Ex. Good Suit. MH C1S1 26 0.91 34.04 -1.19 109.50 Ex. Good Suit. MH C1S1 27 0.6 24.74 -1.12 140.06 Ex. Good Suit. MH C2S1 28 0.66 24.33 -1.31 155.51 Ex. Good Suit. Hard C2S1 29 0.77 26.48 -2.32 161.10 Ex. Good Suit. Hard C1S1 30 0.65 23.58 -1.76 128.08 Ex. Good Suit. MH C2S1

Max. 0.21 11.69 4.07 73.97

Min. 1.76 56.85 0.32 273.51

Mean 0.72 30.43 -1.61 145.41 SD 0.31 9.71 1.08 24.89 CV (%) 43.05 31.91 0.67 16.50

Legend: Ex. = Excellent; Suit. = Suitable; Per.= Permissible; MH = Moderately Hard; C1 = Low Salinity; C2 = Medium Salinity & S1 = Low alkalinity.

1, 2 ,3& 4Classification based on Appendix 3, 1, 4 & 5, respectively.

5Classification based on Fig. 4.1.

 

Fig. 4.1 Diagram for classifying groundwater used for irrigation (Richards, 1968)

4.4 Relationship between water quality factors

The relationships between water quality factors viz., pH, EC, TDS, SAR, SSP, RSC and HT were studied. The calculated r values for 21 combinations of seven factors such as pH vs EC, pH vs

TDS, pH vs SAR, pH vs SSP, pH vs RSC, pH vs HT, EC vs TDS, EC vs SAR, EC vs SSP, EC vs RSC,

EC vs HT, TDS vs SAR, TDS vs SSP, TDS vs RSC, TDS vs HT, SAR vs SSP, SAR vs RSC, SAR vs HT,

SSP vs RSC, SSP vs HT and RSC vs HT, were 0.479, 0.442, 0.070, 0.021, -0.422, 0.385, 0.580, 0.192, 0.236, -0.786, 0.822, 0.350, 0.152, -0.0541, 0.594, 0.779, -0.068, 0.141, -0.090, 0.020 and -0.946, respectively.

Among the combinations, pH vs EC, pH vs TDS, pH vs HT, EC vs TDS, EC vs HT, TDS vs HT and SAR vs SSP relations showed positive significant correlation (Table 4.4). These findings reflected synergistic relationships between the above mentioned quality factors. On the contrary, the combinations such as pH vs RSC, EC vs RSC, TDS vs RSC, and RSC vs HT relationships showed negative significant correlation. The combinations between pH vs

SAR, pH vs SSP, EC vs SAR, EC vs SSP, TDS vs SSR and TDS vs SSP, SAR vs RSC, SAR vs HT, SSP vs RSC and SSP vs HT showed insignificant correlations because the respective calculated r values were below the tabulated value of r at 1% and 5% levels of significance (Table 4.4). Among the major ionic constituents, the remarkable significant correlations existed between Ca vs Mg, Na vs Ca, K vs Ca and K vs Na. The significant relationships between these major ions in groundwater samples have been illustrated in Figs. 4.2 and 4.3.

Table 4.4 Correlation matrix among groundwater quality parameters

Parameters EC TDS SAR SSP RSC Hardness

pH 0.479** 0.442* 0.070NS 0.021NS - 0.422* 0.385*

EC - 0.580** 0.192NS 0.236NS - 0.786** 0.822**

TDS - - 0.350NS 0.152NS - 0.541** 0.594**

SAR - - - 0.779** - 0.068NS 0.141NS

SSP - - - - - 0.090NS 0.020NS

RSC ------0.946**

Legend: NS = Not significant; *Significant at 5% level & ** Significant at 1% level. Tabulated values of r with 28 df were 0.361 at 5% and 0.463 at 1% level of significance, respectively.

2.5 y = 0.4196x + 0.4423 r = 0.4689**

2 )

-1

1.5

) 1 -

1 Ca (me L Ca(me

L (me a C 0.5 (a) 0 0 1 2 3 4

Mg (me L-1)

Mg (me L-1) y = 0.3776x + 0.2387 2.5 r = 0.583**

2

) 1

- 1.5

) 1

1

- Na (me L Na

0.5

(b) Na (me L (me Na 0 0 1 2 3 4

Ca (me L-1)

Ca (me L-1 )

Fig. 4.2 Relationships between Ca vs Mg (a) and Na vs Ca (b)

y = 0.2683x - 0.0534 1.2 r = 0.540**

1 0.8

)

1 0.6 -

K (meK L-1) 0.4

(me L (me

K 0.2 (a) 0 0 1 2 3 4

Ca (me L-1)

Ca (me L-1)

2.5 y = 0.8852x + 0.5307

r = 0.679**

)

1

- 2 )

L (me

-1 1.5 K

1 (b) K (me L (me K

0.5

0 0 0.2 0.4 0.6 0.8 1 1.2

Na (me L-1)

Na (me L-1)

Fig. 4.3 Relationships between K vs Ca (a) and K vs Na (b)

CHAPTER - 5

SUMMARY AND CONCLUSION

A research work was performed to evaluate major ionic toxicity of groundwater for irrigation of Gangachara upazila under the district of Rangpur. Exactly thirty groundwater samples collected from the study area were classified according to their comparative suitability for irrigation purpose. The classification of water samples was accomplished on the basis of pH, electrical conductivity (EC), total dissolved solids (TDS), sodium adsorption ratio (SAR), soluble sodium percentage (SSP), residual sodium carbonate (RSC) and hardness

(HT). pH values of all groundwater samples were within the range of 6.01 to 7.00 indicating slightly acidic to neutral in nature and were not problematic for irrigation The obtained EC values of groundwater samples were within the range of 110 to 748 µScm-1 and all samples were low to medium salinity (C1 and C2) and alkalinity (S1) hazards combinedly expressed as C1S1 and C2S1. In respect of TDS values, all groundwater samples were categorized as fresh water in quality. The collected water samples were of excellent class regarding SAR values. Among 30 water samples, 4 samples were excellent, 21 samples belonged to good and the rest 5 samples were permissible classes based on SSP. According to RSC, all groundwater samples except one sample were categorized as suitable in quality for irrigation. As regards to hardness (HT), 1 sample was soft, 16 samples were moderately hard and the rest 13 samples were hard in quality.

The concentration of B in groundwater samples ranged from 0.05 to 0.88 mg L-1, which were considered as safe limit (<1.0 mg L-1). Considering boron tolerance crops, all groundwater samples were excellent for sensitive to tolerant crops. On the basis of Mn content, all ground water samples except two were below the permissible limit (0.20 mg L- 1 ) for irrigation. Considering Cl and SO4 ions, all samples were not problematic for

irrigation and those ions would not create harmful effect on soils and crops. In the study area, HCO3 ion was treated as toxicant in 11 groundwater samples for irrigation usage -1 because its content exceeded the recommended limit (1.5 me L ). As regards to PO4 content, all groundwater samples had not remarkable influence on its quality for irrigation. The concentration of Fe in the investigated area was observed within the safe limit (5.0 mg L-1). The recorded quantities of K and Na ions in all samples had no significant impact on quality for irrigation. On the basis of Ca and Mg contents, all groundwater samples could safely be used for irrigation and would not affect soil system. The ionic concentration of the collected groundwater samples was detected as per the following order of magnitude as: Ca>HCO3>Mg>Na>Cl>K>SO4>PO4>B>Mn>Fe.

The relationship between different water quality criteria like pH, EC, TDS, SAR, SSP, RSC and

HT were established and combinations such as pH vs EC, pH vs TDS, pH vs RSC, pH vs HT, EC vs TDS, EC vs RSC, EC vs HT, TDS vs RSC, TDS vs HT, SAR vs SSP, SAR vs HT and RSC vs HT exhibited significant relationships. Among the major ions, Ca vs Mg, Ca vs Na, Ca vs K and Na vs K were significantly correlated.

From the present study, it is concluded that all groundwater samples under investigation would not create problem for irrigating soils and crops grown in the study area except HCO3 ion. It may be suggested that some groundwater samples should be treated to remove troublesome ion before specific beneficial use. In addition to the chemical quality, biological and radiological qualities of groundwater should also be taken into consideration.

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