INTRODUCTION:

With the population growth all over the world, rate of urbanization also increases. As a result of it quantity of surface water bodies decrease day by day due to encroachment for construction of houses, buildings, commercial areas, industrial areas etc. This leads to the more demand for ground water for human consumption, irrigation, industrial and many other purposes.

Ground water is about 0.6% of the total global water resources and out of this only 0.3% is extractable economically¹. However such ground waters are not always safe for drinking, other domestic, irrigation and industrial purposes. It is, therefore, necessary to monitor the ground water qualities from time to time just like that of regular monitoring of surface water qualities. With a view to this objective many researchers, all over the world had carried out extensive researches on ground water qualities so as to examine whether such ground waters are fit for human consumption, irrigation and many other purposes^2-6.In many states of India also, many researchers had carried out extensive researches on ground water qualities in addition to regular monitoring of surface water qualities so as to examine whether such ground waters as well as surface waters are fit for human consumption mainly, other domestic and irrigation purposes^7-13.

The present aim of this research work is to carry out physico-chemical studies on ground water qualities of some areas of Imphal East district of Manipur during post-monsoon of 2014. This research work is in continuation of my former research work on ground water qualities of some areas of Imphal West district of Manipur¹⁴.

MATERIALS AND METHODS:

All the chemicals were of AR grade and were used as received. Fifteen ground water samples were collected from hand pumps of different locations of Imphal East district during post-monsoon period (November) of 2014. They were collected in well sterilized polythene bottles of one litre capacity each. Guidelines of sampling and preservation were strictly followed¹⁵. The fifteen samples were analyzed for physico-chemical parameters such as temperature, pH, TDS (total dissolved solids), electrical conductivity(EC), total alkalinity (TA), CO₃^2-, HCO₃^-, total hardness (TH), Ca²⁺, Mg²⁺, Na⁺, K⁺ and Cl^-. The geographical locations (both longitudes and latitudes) of different sampling sites, were measured with the help of a GPS instrument and they are shown in table-1 given below:

Table-1: Locations (with geographical positions) of fifteen sampling sites

Sample code no. (with source)	Sampling sites (locations)	Longitude	Latitude
S-1 (Hand pump)	Keirao Khunou (1) ( near paddy field)	93⁰58^/57.35^//E	24⁰44^/54.60^//N
S-2 (Hand pump)	Keirao Khunou (2) (Near foothill)	93⁰59^/12.02^//E	24⁰44^/50.70^//N
S-3 (Hand pump)	Laipharok(Yaipharok) Maring(1) (near foothill)	93⁰59^/57.53^//E	24⁰44^/28.58^//N
S-4 (Hand pump)	Laipharok (Yaipharok) Maring tampak (2) (near foothill)	94⁰00^/11.59^//E	24⁰44^/29.87^//N
S-5 (Hand pump)	Keirao Wangkhem Bazar	94⁰00^/23.62^//E	24⁰43^/55.68^//N
S-6 (Hand pump)	Keirao Wangkhem Maning Leikai	94⁰00^/30.35^//E	24⁰44^/4.09^//N
S-7 (Hand pump)	Keirao Wangkhem Lairembi Leikai	94⁰00^/37.16^//E	24⁰44^/00.32^//N
S-8 (Hand pump)	Ngarian Mamang Leikai	94⁰01^/37.80^//E	24⁰42^/46.11^//N
S-9 (Hand pump)	Ngarian Maning Leikai	94⁰01^/34.68^//E	24⁰42^/57.43^//N
S-10 (Hand pump)	Huikap Makha Leikai(1) (near foothill)	94⁰01^/48.16^//E	24⁰43^/04.68^//N
S-11 (Hand pump)	Huikap Makha Leikai (2) (Near foothill)	94⁰01^/48.10^//E	24⁰43^/10.43^//N
S-12 (Hand pump)	Huikap Makha Leikai(3)	94⁰01^/45.00^//E	24⁰43^/16.76^//N
S-13 (Hand pump)	Uchol Makha Leikai	94⁰02^/10.08^//E	24⁰44^/05.63^//N
S-14 (Hand pump)	Uchol Mayai Leikai	94⁰02^/09.50^//E	24⁰44^/11.50^//N
S-15 (Hand pump)	Uchol Awang Leikai (near foothill)	94⁰02^/07.14^//E	24⁰44^/19.35^//N

Table-3: Values of physico-chemical parameters of ground water samples from different sampling sites
Sample code no.	Temper-ature (^oC)	pH	TDS (mg/L)	Electrical Conducti-vity (EC) (µS/cm)	Total alkalinity (TA) (as CaCO₃) (mg/L)	HCO₃^- (mg/L)	Total hardness (TH) (as CaCO₃) (mg/L)	Ca²⁺ (mg/L)	Mg²⁺ (mg/L)	Na⁺ (mg/L)	K⁺ (mg/L)	Cl^- (mg/L)
S-1	24	7.4	1030	2346	260	317.2	242	44.1	32.1	338.9	2.2	632.4
S-2	24.9	7.5	259	554	310	378.2	220	43.3	27.2	44.1	1	4.3
S-3	25.1	7.4	281	597	310	378.2	210	36.1	29.2	54.3	1.1	5.7
S-4	22.9	7.3	255	554	300	366	236	42.5	31.6	39	1.1	7.1
S-5	23.6	7.3	272	569	305	372.1	230	44.9	28.7	43.6	1.1	5.7
S-6	23.1	7.3	256	538	300	366	228	40.1	31.1	39.3	1.1	4.3
S-7	23.5	7.6	317	664	360	439.2	76	12.8	10.7	115.4	1.2	7.1
S-8	23.1	7.4	256	546	295	359.9	216	44.9	25.3	43.2	1.4	5.7
S-9	22.3	7.3	225	494	270	329.4	218	48.1	23.8	31.7	0.9	5.7
S-10	23.4	7.4	247	526	260	317.2	128	27.3	14.6	70.1	1.3	8.5
S-11	21.8	7.3	231	485	260	317.2	174	35.3	20.9	45.5	1.7	7.1
S-12	22	7.4	232	492	275	335.5	204	43.3	23.3	37.5	1.2	4.3
S-13	22	7.4	225	494	260	317.2	136	24.8	18	39.7	0.9	4.3
S-14	21.8	7.7	237	522	275	335.5	80	18.4	8.3	58.7	1.5	4.3
S-15	22	7.5	232	504	275	335.5	216	48.9	22.8	24	0.9	5.7

Based on the above experimental results of various physico-chemical parameters of different ground water samples, the following discussion has been made:

Temperature:

The temperature of fifteen ground water samples (S-1 to S-15) are in the range 21.8-25.1⁰C (table-3). S-3 has the highest temperature (25.1⁰C) while those of S-11 and S-14 are the least (21.8⁰C).

pH Values :

The pH values for the ground water samples (S-1 to S-15) range from 7.3 to 7.7 (table-3). S-14 has highest pH value (7.7) while that of S-4 to S-6, S-9 and S-11 are the least one (7.3).

All the pH values for the fifteen ground water samples are within the acceptable limits (6.5-8.5) of BIS standard for drinking water as well as that of WHO^18-19.

TDS (Total dissolved solids):

The TDS values for the ground water samples (S-1 to S-15) are in the range 225-1030 mg/L (table-3). S-1 has highest TDS value (1030 mg/L) while that of S-9 and S-13 are the lowest (225 mg/L). Except S-1, remaining fourteen ground water samples (S-2 to S-15) have their TDS values below the acceptable limit (500 mg/L) of BIS standard for drinking water ¹⁸. Except S-1, TDS values for S-2 to S-15 are below 1000 mg/L and hence they are suitable for other domestic purposes²⁰.

Electrical conductivity (EC):

The electrical conductivity values for the fifteen ground water samples (S-1 to S-15) range from 485-2346 µS/cm (table-3). S-1 has the highest value (2346 µS /cm) while S-11 has the least value (485 µS /cm).

Total alkalinity (TA):

The values of total alkalinity for the fifteen ground water samples (S-1 to S-15) range from 260 mg/L to 360 mg/L (table-3). S-7 has the highest value (360 mg/L) of total alkalinity while those of S-1, S-10, S-11 and S-13 have the lowest value (260mg/L). All the total alkalinity values for the fifteen ground water samples are above the acceptable limit (200 mg/L) but below the permissible limit (600 mg/L) of BIS standard for drinking water¹⁸.

CO₃^2- and HCO^-₃:

The phenolphthalein alkalinity (P-alkalinity) values for the fifteen ground water samples are found to be zero and hence CO₃^2- is almost absent or beyond detectable limit. Therefore, total alkalinity for different ground water samples is due to the presence of HCO^-₃ions only. The concentrations of HCO₃^- for different ground waters range from 317.2 mg/L to 439.2 mg/L (table-3). S-7 has highest value while that of S-1, S-10, S-11 and S-13 is the least one.

Total hardness (TH):

The values of total hardness for the fifteen ground water samples (S-1 to S-15) are in the range 76-242 mg/L (table -3). S-1 has highest value of total hardness (242 mg/L) while that of S-7 is the lowest one (76 mg/L). The total hardness values for S-7, S-10, S-11, S-13 and S-14 are below the acceptable limit (200 mg/L) while that of remaining samples- S-1 to S-6, S-8 to S-9, S-12 and S-15 have their values below the permissible limit (600 mg/L) of BIS standard for drinking water¹⁸. Further, it is clearly seen from table-3 that S-7, S-10, S-13 and S-14 belong to moderately hard water category (75-150 mg/L) while remaining ground water samples (S-1 to S-6, S-8 to S-9, S-11 to S-12 and S-15 belong to hard water category (150-300 mg/L)²⁰.

Calcium (Ca²⁺):

Concentrations of Ca²⁺ for the fifteen ground water samples (S-1 to S-15) are in the range 12.8-48.9 mg/L (table-3). S-7 has the lowest concentration of Ca²⁺ (12.8 mg/L) while that of S-15 is the highest (48.9 mg/L). All the concentrations of Ca²⁺ for the fifteen ground water samples, are below the acceptable limit (75 mg/L) of BIS standard for drinking water¹⁸.

Magnesium (Mg²⁺):

Regarding magnesium contents for the fifteen ground water samples (S-1 to S-15), the concentration values range from 8.3 mg/L to 32.1 mg/L (table-3). S-14 has the lowest concentration of Mg²⁺ (8.3 mg/L) while S-1has highest concentration of Mg²⁺(32.1 mg/L). Ground waters represented by S-2 to S-3, S-5 and S-7 to S-15 have their concentrations of Mg²⁺ below the acceptable limit (30mg/L) while those of S-1, S-4 and S-6, are below the permissible limit (100mg/L) of BIS standard for drinking water¹⁸.

Sodium (Na⁺):

The concentrations of sodium for the fifteen ground water samples (S-1 to S-15) are in the range 24-338.9 mg/L (table-3). S-1 has highest concentration of Na⁺ (338.9 mg/L) while S-15 has lowest concentration of Na⁺ (24 mg/L). Except S-1, other remaining ground water samples (S-2 to S-15) have their concentrations of Na⁺ below the threshold limit (200 mg/L) of WHO¹⁹.

Potassium (K⁺):

All the fifteen ground water samples (S-1 to S-15) have low concentrations of K⁺ ranging from 0.9 mg/L to 2.2 mg/L (table-3). S-1 has highest concentration of K⁺ (2.2 mg/L) while those of S-9, S-13 and S-15, are the lowest (0.9 mg/L).

Chloride (Cl^-):

For the fifteen ground water samples (S-1 to S-15), the concentrations of Cl^- range from 4.3 mg/L to 632.4 mg/L (table-3).Except S-1, other remaining ground water samples (S-2 to S-15) have their concentrations of Cl^- below the acceptable limit (250 mg/L) while that of S-1,is below the permissible limit (1000 mg/L) of BIS standard for drinking water¹⁸.

Ground water quality for irrigation:

The values of RSC (residual sodium carbonate) and SAR (sodium adsorption ratio) for the fifteen ground water samples (S-1 to S-15), are detailed below in table-4:

Table-4: Values of RSC and SAR for ground water samples
Sample code no.	S-1	S-2	S-3	S-4	S-5	S-6	S-7	S-8	S-9	S-10	S-11	S-12	S-13	S-14	S-15
RSC values (meq/L)	0.35	1.80	1.99	1.27	1.49	1.44	5.68	1.57	1.04	2.63	1.72	1.42	2.48	3.89	1.18
SAR values	9.5	1.3	1.6	1.1	1.3	1.1	5.8	1.3	0.9	2.7	1.5	1.1	1.5	2.9	0.7

Table-5: Correlation co-efficient( r) values between different variable pairs of physico-chemical parameters for different ground water samples

	Temp.	pH	TDS	EC	TA	HCO₃^-	TH	Ca²⁺	Mg²⁺	Na⁺	K⁺	Cl^-
Temp.	1
pH	-0.026	1
TDS	0.328	-0.003	1
EC	0.314	-0.001	0.999	1
TA	0.508	0.260	-0.165	-0.184	1
HCO₃^-	0.508	0.260	-0.165	-0.184	1	1
TH	0.288	-0.683	0.247	0.248	-0.120	-0.120	1
Ca²⁺	0.102	-0.604	0.134	0.138	-0.246	-0.246	0.947	1
Mg²⁺	0.432	-0.693	0.328	0.325	0.004	0.004	0.956	0.811	1
Na⁺	0.316	0.108	0.979	0.977	-0.105	-0.105	0.063	-0.048	0.159	1
K⁺	0.046	0.072	0.753	0.751	-0.295	-0.295	-0.033	-0.087	0.021	0.783	1
Cl^-	0.249	-0.032	0.993	0.995	-0.276	-0.276	0.269	0.175	0.329	0.962	0.760	1

From table-5 above, it is clearly seen that strong positive correlation (r=0.999) is there between TDS and electrical conductivity (EC). Both Ca²⁺ and Mg²⁺ show strong positive correlations with total hardness (TH) having r values 0.947 and 0.956 respectively, establishing the fact that high concentrations of Ca²⁺ and Mg²⁺ attribute to more hardness of different waters. Strong negative correlation (r=-0.683) between pH and total hardness, indicates that with increase of pH, the total hardness for different ground water samples decreases and vice-versa. Cl^- shows strong positive correlations with both Na⁺ and K⁺ having r values 0.962 and 0.760 respectively showing that both Na⁺ and K⁺ exist as chlorides in the different ground waters represented by S-1 to S-15. Further, Na⁺, K⁺ and Cl^- show strong positive correlations with TDS having r values equal 0.979, 0.753 and 0.993 respectively. Similarly, Na⁺, K⁺ and Cl^- show strong positive correlations with EC (r=0.977, 0.751 and 0.995 respectively).

The above strong positive correlations of Na⁺, K⁺ and Cl^- with TDS and EC respectively, establish the fact that high values of TDS (and hence EC) are due to presence of NaCl and KCl salts mainly in the different ground waters represented by S-1 to S-15.

CONCLUSIONS:

On the basis of the above discussions based on various experimental data and various correlation co-efficient (r) values of different pairs of physico-chemical parameters for fifteen different ground waters (S-1 to S-15), the following conclusions are drawn:

(i) Ground water represented by S-1 is unfit for drinking purpose as many of the parameters have their values far above the acceptable limits of BIS standard for drinking water and that of WHO respectively.

(ii) Ground waters represented by S-2 to S-15 may be used for drinking and other domestic purposes in absence of alternate sources.

However, some suitable treatments are necessary so as to keep the high values of the following parameters below the corresponding acceptable limits of BIS standard for drinking water –

a) treatment of high values of total alkalinity for S-2 to S-15

b) treatment of high values of total hardness for S-2 to S-6, S-8 to S-9, S-12 and S-15

c) treatment of high values of Mg²⁺ for S-1, S-4 and S-6.

(iii) Ground waters represented by S-1 to S-15 are fit for irrigation purpose.

(iv) Strong positive correlations of Cl^- with Na⁺ and K⁺ respectively, show the presence of NaCl and KCl salts in the different ground waters and further these two salts are mainly responsible for high values of TDS (and consequently high values of EC) of the different ground water samples.

ACKNOWLEDGEMENTS:

The author is thankful to the principal, D.M. college of Science, Imphal for the laboratory facilities provided for this research work and also to those local people of different sampling sites, for the co-operation extended by them.

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Received on 04.12.2015 Modified on 10.12.2015

Asian J. Research Chem. 8(12): December 2015; Page 733-738

DOI: 10.5958/0974-4150.2015.00118.2

Table-2 : Instruments and methods used for measurement / determination of physico-chemical parameters of ground water samples
Physico-chemical paramaters measured / determined	Instruments and methods used
Temperature	TDS Meter (TDS-3) (TDS/Temp.) (HIMEDIA, India)
pH	pHep® Pocket-sized pH Meter (HI98107) (HANNA Instruments, Romania)
TDS (Total dissolved solids)	TDS Meter (TDS-3) (TDS/Temp.) (HIMEDIA, India)
Electrical conductivity (EC)	Conductivity Tester (Dist 3: HI 98303) (HANNA Instruments, Romania)
Total alkalinity (TA)	Titrimetric method with standard HCI solution using phenolphthalein and methyl orange indicators
CO₃^2- and HCO₃^-	By calculation method from total alkalinity values
Total hardness (TH)	EDTA titrimetric method (using Eriochrome Black T Indicator)
Calcium (Ca²⁺)	EDTA titrimetric method (using Murexide indicator)
Magnesium (Mg²⁺)	By calculation method
Sodium (Na⁺) and Potassium (K⁺)	Flame Photometer 128 (Systronics, India)
Chloride (Cl^-)	Argentometric titrimetric method (Using K₂CrO₄ indicator solution)