Journal of Environmental Science, Computer Science and Engineering & Technology

JECET; March 2020- May 2020; Sec. A; Vol.9. No.2, 327-341. E-ISSN: 2278–179X

[DOI: 10.24214/jecet.A.9.2.32741] Journal of Environmental Science, Computer Science and Engineering & Technology

An International Peer Review E-3 Journal of Sciences and Technology

Available online at www.jecet.org Section A: Environmental Science Research Article

Physicochemical characterization and evaluation of river water quality for its potability, Champhai District, Mizoram, NE India

Watitemsu Imchen1*, Pritam Panja2, Chonbenthung Yanthan3, Athili Elow1

1Geological Survey of India, NER, Dimapur, India 2Geological Survey of India, ER, Kolkata, India 3Geological Survey of India, NER, Agartala, India

Received: 11 April 2020; Revised: 23 April 2020; Accepted: 05 May 2020

Abstract: River water is the main source for drinking, irrigation, and other purposes in the mountainous region of Mizoram, NE India. Rainwater harvesting is a common practice and effectively utilized during the monsoon period; however, rivers or streams are the only sources of water during the lean period. Thus it is imperative to assess the water quality for public health and water resource management. Physicochemical parameters and quality of Changel Tui, Tuichang R. (Khawzawl), Chawngtlai and Chungte water sources, Champhai district have been analyzed using factor analysis (FA) and cluster analysis (CA) to assess the water quality and potential pollution sources. Water quality was monitored for six months during the lean period from October 2017 to March 2018 using 13 parameters such as pH, temperature (T), turbidity (Tb), total hardness (TH), total dissolved solids (TDS), dissolved oxygen (DO), total alkalinity (Alk), electrical conductivity (EC), chloride - - - (Cl ), fluoride (F ), total phosphorus (P), nitrate (NO3 ), and iron (Fe) were analyzed. The results indicate that all water quality parameters are well within the permissible limit with minor temporal variation barring turbidity in comparison to the Bureau of Indian Standards (BIS). Multivariate analysis indicates that the water quality has been largely affected by dissolved mineral salts leached from the underlying sandstone- siltstone-shale beds, and soil erosion and leaching due to agricultural activities have

327 JECET; JECET; March 2020- May 2020; Sec. A; Vol.9. No.2, 327-341. DOI:10.24214/jecet.A.9.2.32741.

Physicochemical… Imchen et al. influenced the water sources. However, water quality index (WQI) computed from physicochemical parameters qualify the water sources of Khawzawl, Chawngtlai, and Chungte as good quality suitable for use as potable water.

Keywords: Physicochemical properties; Water quality; Multivariate analysis; Mizoram.

INTRODUCTION

The river is one of the major sources of water used for human consumption, irrigation, and industrial purposes and is one of the most susceptible water bodies to pollutants by both natural processes as well as anthropogenic factors [1, 2]. The efficient management of drinking water resources requires information about its quality and variability. Water quality is indispensable for the health of all living beings [3, 4]. Physicochemical and biological contaminants of surface waters by anthropogenic activities is of paramount environmental concern. Mizoram, the landlocked state of Indian Union bordering Myanmar is characterized by parallel to sub-parallel N-S trending hill ranges and valleys. Myriads of northerly and southerly flowing rivers separate the steep hill ranges with the development of numerous gorges. The perennial, as well as few ephemeral rivers, are the main sources of water for domestic, small scale industrial and agricultural/irrigation purposes to the common populace of Mizoram. The present study falls in Khawzawl Sub-Division, Champhai, Mizoram. Khawzawl notified town is inhabited by about 2,306 households with more than 11 thousand population. Changel Tui, Tumkhuai, Tuichang, etc are the main water sources for drinking and other domestic purposes for Khawzawl notified town. Rapid urbanization, population explosion, and ever-increasing demand in domestic and agricultural sectors require good quality of water supply. In Mizoram State, rainwater is mostly harnessed and utilized during the monsoon period; however, during the lean period, spring or river waters are the only sources of water for domestic and other purposes. Therefore, it is felt imperative to gather reliable information on the characteristics of water quality for public health and water resource management. With this objective in mind, the physicochemical parameters of Changel Tui and Tuichang (water sources of Khawzawl town), Chawngtlai and Chungte drinking water sources have been monitored for six months from October 2017 to March 2018 and are analyzed using FA and CA to determine their quality, variability and latent pollutants.

GEOLOGY AND HYDROGEOLOGY

The study area forms a part of Neogene-Paleogene Accretionary Belt in the eastern fringe of Mizoram State lying within the latitudes of 23°22′06′′N−23°38′18′′N and longitudes of 93°04′27′′ E−93°20′6.6′ ′E in parts of Survey of India toposheet 84E/2,3, 6 and 7. The Laisong, Jenam, and Renji formations of the Barail Group forms the older units overlain by the Middle and Upper unit of the Bhuban Formation (Surma Group) (Fig. 1). Laisong Formation constitutes an interbedded sequence of sandstone and shale with occasional siltstone and conglomerate horizons (arenite/argillite ratio= 60:40). The overlying Jenam Formation is predominantly greenish-grey shale in the lower part and interbedded shale siltstone and fine-grained sandstone in the uppermost part (arenite/argillite ratio= 15:85) while the younger Renji Formation is characterized by medium to thickly bedded grey sandstone with subordinate mudstone (arenite/argillite ratio= 80:20 ratio); they form the higher reaches (synclinal hills) reflecting second-order topography. The contact between these formations is conformable and gradational. The overlying Bhuban Formation constitute predominantly of shale with subordinate siltstone and sandstone on the lower horizon while the rocks on the upper horizon vary from brown hard and compact, bedded, fine-grained sandstone with minor grey laminated shale

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Physicochemical… Imchen et al. as lower unit and yellowish-brown, friable, well-bedded to massive, fine to medium-grained sandstone with minor greyish brown shale with ubiquitous ferruginisation in sandstones.

Figure 1: Geological map vis-à-vis sampling stations of the study area

The physiography of the Champhai district can be broadly divided into hills, valleys, and flatlands. The soils of different physiographic units are homogenous in terms of genetic aspects as they are the product of chemical weathering of sandstones, shales, and siltstones. In the hills, the soil is light- colored, highly leached, poor in bases, rich in iron, and has a low pH value (highly acidic) due to excessive leaching. They are well-drained, moderately rich in organic carbon, deficient in phosphate, potassium, phosphorous, nitrogen, and even in humus content [5]. The soils on the top of barren ridges, however, are mostly shallow or underlaid by weathered rock and only thin veneer of soil is developed. The valley's flatlands exhibit heavy texture, poorly permeable, or poorly drained soils with high groundwater table. They are alluvial and colluvial, most fertile and productive soils. The soil thickness is more in the valley due to constant erosion from high altitudes. The soil developed along the narrow valley is young, light-color, coarse-texture, well-drained, and well-aerated. The soil cover of the dissected low hills/hillocks is comparable to the soil that is developed along the ridges and hill slopes at the higher reaches. The terrain is extremely rugged and undulating baring Champhai town with low lying valleys. Champhai district is occupied by semi-consolidated formations of denudo-structural hills of Barail and Surma rocks. Low linear ridges have low permeability and infiltration capacity and act as a runoff zone. The moderate linear ridges, which occupy the major portion of the district, comprised of

329 JECET; JECET; March 2020- May 2020; Sec. A; Vol.9. No.2, 327-341 . DOI:10.24214/jecet.A.9.2.32741.

Physicochemical… Imchen et al. predominantly hard and compact sandstone-shale-siltstones intercalations of the Barail group of rocks with relatively low groundwater potential [5]. The occurrence of groundwater in such terrain is predominantly confined along weak zones such as fracture, lineament, weathered zones, and Quaternary deposits. These tectonic elements facilitate conduit for water seepages in the form of spring. North-South trending valleys between the adjoining linear ridges have at places developed small pond like structures with shallow water level (2.0 m bgl). Broadly, groundwater potential is relatively higher in the Champhai valley fill area although with limited areal extent however, the groundwater potential decreases along higher reaches [5]. Surface water is the main source of potable water for the adjoining areas, tapped through the gravity method. The discharge of water increases with a decrease in altitude downslope. Water discharge of the spring varies between 3,000 to 20,000 ltr/day from January to March [5].

MATERIALS AND METHOD

To evaluate the physicochemical parameters of river waters of the Khawzawl notified town, Chawngtlai and Chungte hamlets, Champhai district, Mizoram, their water sources were identified and studied. Changel Tui and Tuichang R. are water sources for Khawzawl notified town and water from tributaries of Khuai Lui and Saikah Lui are drawn for Chawngtlai and Chungte hamlet respectively with a total of four sampling stations (Fig. 1). The load of the utilization of river waters increases exponentially during the post-monsoon period. Rivers are the only source of water available during the lean period for use as potable water and other domestic purposes. Consequently, four hydrological monitoring stations were identified from the water sources drawn for Khawzawl town, Chawngtlai, and Chungte, and 13 physicochemical parameters were monitored every fortnight from these 4 monitoring stations (n= 52) for a period six months from October 2017 to March 2018 to determine the temporal quality variability and latent pollutants. Water samples were collected in a 250 ml cleaned polyethylene bottles using a collection vessel immersion technique at a maximum depth of 30 cm from the water surface in the forenoon hours to minimize the effects of temperature. T, pH, and EC were measured on-site. T was measured using a mercury thermometer and noted in °C. The pH and EC of the water sample were measured by electronic portable pH and EC meter. Water samples collected in the field were analyzed for the major ions following the methods recommended by the American Public Health Association [6]. The Tb of the water was measured using a turbidity tube. DO was estimated by carefully collecting water samples in the DO bottle avoiding bubbles. The DO was then fixed at the station itself by adding 1 ml each of manganese sulfate and alkaline potassium iodide and brought to the laboratory. The precipitates formed were dissolved by adding 2 ml of phosphoric acid. 10 ml sample was titrated against sodium thiosulphate. Starch is used as an indicator to estimate iodine generated and the endpoint is noted as the solution turns from blue to colorless. TH of the water was estimated following EDTA titrimetric method, Cl- by the argentometric titrimetric method, phosphate by using ammonium molybdate and stannous chloride [6]. Alk (IS 3025, 23), Fe (IS 3025, 53), and F- (IS 3025, 60) were analyzed following BIS [7]. Due to the insignificant variability of parameter values within a month, the average value has been utilized for statistical computation. Normal distribution of data is essential for multivariate analyses such as FA and CA because the analyses will be valid only if the standard deviations are low. If the data are not normalized, the parameters with the highest variances tend to influence the analysis [8]. Due to wide variations in data dimensionality in the present study, the standard z-scale transformation

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Physicochemical… Imchen et al. was applied to eliminate the influence of different units of water quality parameters before multivariate analysis (Table 1). The z-scores were calculated as:

z = (x – μ) / σ

where x - data point, μ- mean, σ – standard deviation Factor analysis entails three stages [9]. The first stage involves the determination of the correlation matrix for all the variables to account for the degree of mutually shared variability between individual pairs of water quality variables. Secondly, the extraction of factors (eigenvalue and factor loadings) from the correlation matrix based on the correlation coefficients of the variables. Eigenvalues correspond to an eigen-factor which identifies groups of variables that are highly correlated among them; lower eigenvalue contribute little to the explanatory ability of the data, and thirdly rotation of factors (varimax rotation) was used to yield a simpler factor structure and to maximize the relationship between some of the factors and variables. Factor loading is classified as ‘strong’, ‘moderate’, and ‘weak’ corresponding to absolute loading values (+ve or -ve) of >0.75, 0.75-0.50, and 0.50-0.30 respectively. The correlation coefficient (r) for various elements and ratios was calculated using Karl Pearson’s formula, r=Σdxdy/√(Σdx2) (Σdy2).

RESULTS AND DISCUSSION

Physicochemical properties: Temperature regulates water chemistry, especially DO, solubility, pH, conductivity, and biodegradation rate [10]. It plays a vital role in the physicochemical and biological behavior of an aquatic system [11]. Besides, aquatic organisms require a certain temperature range for their optimal growth and a change in temperature can trigger photosynthesis by aquatic plants [6]. The range of temperature in these water sources is lower than the value (25°) recommended by the World Health Organization [12]. The temperature of the water is lowest during December and gradually increases thereafter. The mean temperature is relatively higher in Chungte relative to other water sources (Table 1).

The variability in carbonate-bicarbonate-CO2 is the function of pH in natural waters. The pH severely affects the water quality by changing the Alk, the solubility of metals, and TH of the water, and is toxic to animals and vegetations of the water ecosystem [13]. WHO [12], Indian Council of Medical Research (ICMR) [14], and BIS [7] proposed the permissible range of pH from 6.5 to 8.5. In the present study, pH value is more or less neutral; however, slight alkaline nature is evident during January and February in all the water sources; such higher pH values would turn the water salty and cause eye irritation. Lower pH values of 6.0 are recorded during October 2017 in Tuichang and Chungte; such acidic pH values (<6.5) affects the production of vitamins and minerals in the human body [15]. Tb of water is due to suspended particles (clay, silt, plankton), dissolved compounds, or microscopic organisms that scatter light making the water appear murky. High Tb has a significant effect on the quality of the river water and can harm aquatic life [16]. WHO[12]. ICMR [14] and BIS [7] have prescribed a maximum range of 2.5, 5, and 5 NTU respectively depending upon the processes used for the treatment of wastewater [17, 18]. Tb is relatively higher in all the water sources, exceeding the prescribed maximum range (>5 NTU) (Table 1). It is also interesting to note that Tb is highest during October 2017 and gradually decreases till March 2018 barring Changel water source. The values indicate that Chungte shows relatively higher Tb than other water sources (Table 1). Such high Tb

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Physicochemical… Imchen et al. value is ascribed to the availability of abundant material for erosion in the vicinity and the lower Tb in Changel water source is due to thick forest cover in the catchment area. WHO [12] classified TH as soft (0-75 mg/l), medium-hard (75-150 mg/l), hard (150-300 mg/l) and very hard (>300 mg/l). The TH of Chawngtlai water source varies from soft to medium-hard, medium-hard in Changel, medium-hard to hard in Tuichang, and soft to hard in Chungte (Table 1). The prescribed permissible TDS range is 500-1500 mg/l [19, 14, 12, 7]. According to USGS [20], those water with values >1000 mg/l of TDS is not palatable as drinking water. Consequently, high TDS contents are of inferior potability and may induce an unfavorable physiological response on the body of the consumer [21]. In contrast, a high concentration of TDS beyond the permissible limit may enhance eutrophication and even unsuitable for many industrialized applications [22, 6]. TDS value in these water sources are well within the prescribed limit (Table 1). DO influence the biological parameters due to the aerobic or anaerobic phenomenon and determines the quality of river/stream waters suitable for aquatic as well as human life [23]. The depletion of DO in water bodies is mostly related to water pollution and their deficiency affects aquatic life [24]. The DO in water increases with the decreases in temperature [25]. The standard DO value range between 4 to 6 mg/l [19, 7], is conducive for thriving aquatic life. DO values in all the water sources are higher than the prescribed value (Table 1). The Alk of water may be attributed to the presence of bicarbonate, carbonates, and hydroxides of calcium, magnesium, sodium, and potassium. If present in excess, water becomes bitter, harmful for irrigation, and reduces crop yield [26]. Alk of water is categorized into three classes: 1-15 mg/l as nutrient-poor, 16-60 mg/l as moderately nutrient-rich and >60 mg/l as nutrient-rich [27]. The values indicate Chawngtlai water source as moderately nutrient-rich, Changel as moderate to nutrient-rich while Tuichang Lui and Chungte as nutrient-rich (Table 1). EC is a measure of the capacity of water to conduct electrical current and thus its overall concentration of dissolved salts in water. The presence and concentration levels of Na and Mg ions and to some extent Ca ions determine the EC in water. Thus EC of water indicates the salinity or total salt content. In Tuichang and Chungte water sources, EC show an incremental increase in tandem with TDS values which indicate a gradual concentration of dissolved natural salts with further falling in the water quantity. The high positive correlation of EC and TDS (r= 0.9) in all the four water sources suggest their intimate association. In the present study, EC values are within the permissible limit of 1000 μS/cm proposed by the Federal Environmental Protection Agency [28]. Water with higher Cl- indicates the predominance of organic pollution [29]. Cl- concentration in seawater is around 20,000 mg/l, 2-10 mg/l in unpolluted rivers and 2 mg/l in rainwater. The maximum permissible limit of Cl- in natural freshwaters is 250 mg/l [7, 14]. Cl- concentration in drinking water is largely attributed to natural sources, sewage, industrial effluents, and urban runoff. In natural water, excessive Cl- ions are associated with Na+, K+, and Ca++ making water salty when the concentration is about 100 mg/l [30]. In the present study, Cl- concentration in all the water sources falls well within the permissible limit (Table 1). P is a minor constituent in natural water due to absorption by aquatic plants [31]. It also depends on the amount of P in the catchment soils, topography, vegetative cover, climate, land use, and pollution. It is an important constituent for regulating the reproduction and growth of the aquatic organism. However, only an insignificant concentration of total P is recorded in the study area (Table 1).

- [7] NO3 concentration in these water sources is very low and within the threshold value of 45 mg/l and 50 mg/l [12] (Table 1). Only traces of F- (≤0.3 mg/l) are recorded in all the water sources which are

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Physicochemical… Imchen et al. well within the permissible limit of BIS (1 mg/l), suggesting no contamination. Similarly, Fe values are also found to be ≤0.3 mg/l, is considered desirable water quality as per the BIS guideline.

Table 1: Descriptive statistics, weight and relative weight of the analyzed parameters

- - - T F TH Cl DO Alk EC TDS Tb NO Fe P Parameter pH 3 (̊ C) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (μS) (mg/L) (NTU) (mg/L) (mg/L) (mg/L) Desirable value 8.5 - 1 300 250 6 - 1400 500 - 45 0.3 10 (BIS, 2012)

Weight (wi) 4 - 5 2 1 2 - 4 5 - 5 4 1

Relative Weight (Wi) 0.12 - 0.15 0.06 0.03 0.06 - 0.12 0.15 - 0.15 0.12 0.03

Mean 8.0 18.1 0.22 89.3 50.27 9.8 62.0 76 35.2 6.4 0.23 0.22 0.33

Std. dev 0.6 1.65 0.07 11.0 29.3 1.8 9.9 6.23 3.3 1.2 0.08 0.07 0.12

Max 8.7 20.5 0.3 112 106 12.4 70 85 41 8 0.4 0.3 0.5

Changel Min 7.0 16.4 0.1 80 28.36 7.6 40 65 31 5 0.1 0.1 0.2

Mean 7.7 19.6 0.23 82 33.8 7.7 48.5 75 36.7 10.7 0.2 0.16 0.3

Std. dev 0.3 2.6 0.07 26.3 2.4 0.75 4.8 10.11 5.3 1.8 0.06 0.06 0.07

Max 8.1 25 0.3 112 35.5 9.2 56 84 44 14 0.3 0.2 0.4

Chawngtlai Min 7.3 17 0.1 40 28.4 6.8 40 56 27 8 0.1 0.1 0.1

Mean 7.9 20.2 0.19 127 36.9 8.7 96.12 132 64 10.3 0.28 0.20 0.25

Std. dev 0.94 1.13 0.07 18 2.65 1.2 24 30.5 14.4 1.6 0.11 0.06 0.07

Max 8.7 23.4 0.3 160 42.54 10.6 120 176 86 15 0.5 0.3 0.3

Tuichang Min 6 19.7 0.1 104 35 6.4 64 88 43 8 0.2 0.1 0.2

Mean 7.85 20.3 0.20 102.8 30.5 9 98.2 141 70.7 13.3 0.3 0.21 0.23

Std. dev 0.95 1.23 0.06 43.6 9.2 0.60 17 39.3 16.5 5.7 0.06 0.05 0.09

Max 8.7 22.9 0.3 192 49.63 9.7 120 179 86 25 0.4 0.3 0.4

Chungte Min 6 19.2 0.1 44 22 8 72 82 40 10 0.2 0.1 0.1

Factor analysis: FA explains the correlations between the observations in terms of the latent variables, which are not directly observable in a large set of data [32]. The scree plot of the eigenvalues of FA was used to identify the number of factors to unravel the latent data structure. Eigenvalues of ≥1 were considered significant [33]. The scree plot in this study exhibit a marked break in slope after the third eigenvalues in Changel and Chawngtlai, while in Tuichang and Chungte change in slope is evident after fourth eigenvalues (Fig. 2). Consequently, the factors with eigenvalues greater than or close to unity were considered for further analysis. The extracted factors explain 91.31%, 93.76%, 97.88%, and 98.68% of the total variance of information contained in the original dataset for Changel, Chawngtlai, Tuichang, and Chungte water sources respectively (Table 2). In Changel, Factor 1 accounting for 42.33% of the total variance is dominated by chemical parameters such as pH, Alk, EC and TDS, and negative loadings of T and Cl- (Fig. 3a). This is ascribed to an increase in the ionic concentration of dissolved mineral salts from the sandstone-siltstone-shale

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Physicochemical… Imchen et al. interbeds and soil, and in turn, affects pH values. This is further corroborated by the high positive correlation of TDS, EC, and Alk with pH (r= 0.91, 0.95, 0.62). The negative correlation of pH, EC, TDS, and Alk with temperature (r= -0.59, -0.69, -0.78, -0.61) suggests the nominal role of evaporation in the concentration of ions. The strong negative loadings of Cl- indicate no influence from anthropogenic sources.

Table 2: Loadings of the physicochemical parameters on significant factors

Changel Chawngtlai Tuichang Chungte Variables F1 F2 F3 F1 F2 F3 F1 F2 F3 F4 F1 F2 F3 F4 pH 0.91 0.28 -0.15 0.77 0.28 0.55 0.91 0.04 -0.04 -0.34 0.90 -0.08 0.40 0.01

T -0.83 0.41 -0.34 -0.36 -0.75 -0.52 -0.96 -0.05 0.20 0.13 -0.09 0.06 -0.74 0.81

F- -0.54 -0.59 0.25 -0.87 0.19 -0.43 0.09 -0.98 -0.07 0.08 -0.01 -0.94 -0.23 -0.23

TH -0.04 0.65 -0.73 0.55 0.23 0.72 0.76 0.63 -0.02 0.01 0.94 0.24 -0.14 -0.04

Cl- -0.84 -0.22 0.43 0.58 0.21 0.78 0.40 0.86 -0.04 0.29 0.79 0.36 -0.08 -0.32

DO -0.14 0.91 -0.27 0.89 0.40 0.11 -0.05 -0.80 0.35 -0.07 0.47 -0.55 0.50 0.27

Alk 0.78 -0.19 -0.37 0.41 -0.23 0.83 0.91 0.09 0.23 0.24 0.96 -0.07 -0.14 0.27

EC 0.95 0.28 0.03 0.06 0.99 -0.03 0.89 0.40 0.17 0.07 0.96 0.06 0.16 0.18

TDS 0.95 0.12 0.14 0.07 0.96 0.04 0.87 0.46 0.14 0.02 0.96 -0.14 0.10 0.06

Tb 0.48 0.71 -0.49 -0.55 0.14 -0.81 -0.89 0.23 0.14 0.21 -0.91 0.34 -0.17 0.09

- N03 0.12 -0.07 0.83 -0.75 -0.63 0.05 0.30 -0.11 0.64 0.68 0.03 0.10 0.97 -0.06

Fe -0.14 -0.26 0.90 -0.31 -0.57 -0.37 -0.14 0.08 0.85 -0.47 0.04 0.92 0.30 0.21

P -0.47 -0.82 0.09 -0.16 0.28 0.93 0.32 0.73 0.42 -0.29 -0.02 0.99 0.04 0.10

Eigenvalue 6.62 3.75 1.36 7.74 3.03 1.40 6.92 2.84 1.82 1.12 6.40 3.40 1.99 1.03

Variability (%) 42.3 25.4 22.5 31.8 28.9 32.9 45.9 29.1 14.2 8.68 47.7 26.2 16.7 7.93

Cumulative % 42.3 68.7 91.3 31.8 60.7 93.7 45.9 75.0 89.2 97.8 47.7 73.9 90.7 98.6

Factor 2 explains 25.43% of the total variance, and largely contributed by DO, Tb, and TH with strong negative loadings of P. The TH (medium-hard) of the water indicates their contribution from carbonate rocks/soil from the catchment area through erosional activities as evident by positive moderate loading of Tb. The enriched DO (av. 9.8 mg/l) indicates the health of the water body and their enrichment is attributed to the photosynthesis process. The strong negative loadings of P indicate no influence of any anthropogenic pollutants in the vicinity. Factor 3 shows positive loadings of Fe - and NO3 reflecting their contribution from natural sources i.e. underlying bedrock and soil as such low levels of these elements are commonly known in freshwater (0–18mg/l) [12]. Factor 1 in Chawngtlai explains 31.85% of the total variance with strong positive loadings of pH, DO, and moderate TH and Cl- loadings (Fig. 3b). This is further corroborated by soft to medium hardness, minor Cl- content (av. 34mg/l), and weak alkalinity (av. 48.5mg/l) reflecting the influence of dissolution of natural mineral salts. pH values are largely regulated by TH, Cl- and Alk (r= 0.91, 0.94, 0.87). The higher DO (av. 7.7mg/l) reflects biochemical activities. Factor 2 explains 28.94% of the total variance with strong positive loadings of EC and TDS showing effects of dissolution of natural mineral salts. The strong to moderate negative loadings of T and Fe respectively indicate an 334 JECET; JECET; March 2020- May 2020; Sec. A; Vol.9. No.2, 327-341 . DOI:10.24214/jecet.A.9.2.32741.

Physicochemical… Imchen et al. insignificant influence of the former in the dissolution of mineral salts and the latter indicate the absence of ferruginized bedrock/soil in the vicinity. Factor 3 accounts for 32.97% of the total variance

7 100 8 100

6 Changel 7 Chawngtlai 80 80 6 5 5 60 4 60 4 3

40 3 40

Eigenvalue Eigenvalue 2 2 20 20

1 1

Cumulative variability (%) variability Cumulative Cumulative variability (%) variability Cumulative

0 0 0 0 F1 F2 F3 F4 F5 F1 F2 F3 F4 F5

8 100 7 100 Chungte 7 Tuichang 6 80 80 6 5 5 60 4 60 4 3 40 40

3 Eigenvalue Eigenvalue 2 2 20 20

1 1

Cumulative variability (%) variability Cumulative Cumulative variability (%) variability Cumulative 0 0 0 0 F1 F2 F3 F4 F5 F1 F2 F3 F4 F5

Figure 2: Scree plot of the eigenvalues of factors in Changel, Chawngtlai, Tuichang, and Chungte and shows strong positive loadings of TH, Cl-, Alk, and P which is ascribed to natural sources. Very strong loadings of P are evident from FA, however, their values (av. 0.6 mg/l) are well within the permissible limit. In the Tuichang water source, Factor 1 explains 45.94% of the total variance of the data and shows moderate to strong influence of pH, Alk, TH, EC and TDS, and T and Tb show strong negative loadings (Fig. 3c). The moderate to strong loadings of pH, Alk, EC, and TDS is ascribed to the presence of carbonate and bicarbonate derived from the calcareous sandstone bands as dissolved solvents, also corroborated by their high correlation coefficient with TH (r= 0.72, 0.75, 0.93, 0.95). The high negative loadings of T and Tb indicate that the former is regulated by the latter as a consequence of erosional activity as evidenced by higher values of T (av. 20.5C) and Tb (av. 10.25 NTU) respectively. Factor 2 accounts for 29.1% of the total variance with strong Cl- positive loadings and moderate TH and P loadings. Factor 3 accounts for 14.16% of the total variance with strong Fe - - and moderate NO3 loadings reflect soil-derived Fe (av. 0.20%) and NO3 (av. 0.28%) which are well - within the permissible limit and common in freshwater. Similarly, Factor 4 also shows moderate NO3 loadings which are attributed to cross-loadings. The pH, TH, Cl-, Alk, EC, and TDS are largely influential parameters in the Chungte water source explaining the total variance of 47.75% of the data in Factor 1 (Fig. 3d). pH is largely affected by the

335 JECET; JECET; March 2020- May 2020; Sec. A; Vol.9. No.2, 327-341 . DOI:10.24214/jecet.A.9.2.32741.

Physicochemical… Imchen et al. presence of higher Cl-, Alk, EC and TDS, and TH of the water is attributed to leaching of bicarbonates and carbonates from soil/bedrocks and show a positive correlation with TDS, Cl-, Alk, EC, and pH, (r= 0.86, 0.89, 0.87, 0.87, 0.76). There exists a strong influence of Tb and exhibits the highest Tb value (av. 13.3 NTU) relative to other water sources, reflecting high erosional activities in the catchment area. It is intriguing to note here that the strong negative loadings of Tb, however, suggest that the dissolution of natural salt decreases with an increase in Tb and T.

Factor loadings (axes F1 and F2: 67.76 %) Factor loadings (axes F1 and F2: 60.80 %) 1.5 1.5

1 DO 1 TDS EC TH Tb 0.5 0.5 DO T EC P pH F Tb Cl pH TDS TH 0 0 Cl NO3 Alk Alk

Fe F2 (28.95 %) (28.95 F2 F2 (25.44 %) (25.44 F2 -0.5 -0.5 Fe F NO3 T P -1 -1 (a (b -1.5 -1.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 ) 2 -2 -1.5 -1 -0.5 0 0.5 1 1.5 ) 2 F1 (42.33 %) F1 (31.85 %)

Factor loadings (axes F1 and F2: 75.05 %) Factor loadings (axes F1 and F2: 73.99 %)

1.5 1.5

1 1 P F Cl Fe P TH 0.5 TDS 0.5 Cl EC Tb Tb TH Fe Alk T NO3 0 0 EC T pH pH Alk

NO3 TDS F2 (29.11 %) (29.11 F2 -0.5 %) (26.23 F2 -0.5 DO DO -1 -1 F (c (d -1.5 -1.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 ) 2 -2 -1.5 -1 -0.5 0 0.5 1 1.5 ) 2 F1 (45.94 %) F1 (47.76 %)

Figure 3: Varimax rotated factors (a) Changel, (b) Chawngtlai (c) Tuichang, and (d) Chungte

Factor 2 explains 26.23% of the total variance of the data with strong positive loadings of Fe and P. Fe concentration is rather very low (av. 0.21 mg/l) and is akin to normal river water concentrations (0.5-1 ppm). P is normally derived from both non-point (dissolution from rocks, stormwater runoff, agricultural runoff, erosion, and sedimentation, etc) as well as from point sources (wastewater treatment plants and industrial discharges). The presence of P in traces (av. 0.23 mg/l), in this case, is attributed to non-point source as their contribution from point source seems very unlikely in the - present study area. Factor 3 shows the influence of NO3 which accounts for 16.77% of the total - variance. However, low concentrations of NO3 along with insignificant temporal variations in Chungte water source indicate their source as geogenic with more or less no pollution from point 336 JECET; JECET; March 2020- May 2020; Sec. A; Vol.9. No.2, 327-341 . DOI:10.24214/jecet.A.9.2.32741.

Physicochemical… Imchen et al. sources such as sewer system, fertilized agriculture, etc. Factor 4 explains 7.93% of the total variance with strong positive loading of T reflects the influence of temperature as T is relatively higher (av. 20.3oC) in this water source. Cluster analysis: CA identifies groups or clusters of a similar entity based on similarities within a class and dissimilarities between different classes. Dendrogram, based on R-mode CA distinguishes two significant clusters for the analyzed water quality parameters (Fig. 4). Elements belonging to the same cluster are likely to have originated from a common source. Cluster 1 includes TH, EC, Cl-, Alk, - - and TDS, while cluster 2 consists of T, Tb, pH, DO, NO3 , P, F , and Fe. Cluster 1 represents the geogenic source due to the dissolution of mineral salts leached from the underlying sandstone- siltstone-shale interbeds and soil in the catchment area. TH of water is generally due to Ca, Mg, bicarbonates, and sulfates; although these parameters have not been analyzed in the present study, others have reported appreciable concentrations of bicarbonates (12-158 mg/l), Ca (4-22 mg/l) and Mg (1-10 mg/l) from groundwater [5].

Figure 4: Dendrogram showing the hierarchical clusters of the analyzed parameters

Similar values of bicarbonates (70-280 mg/l), Ca (6-66 mg/l), Mg (3.3-37 mg/l), and sulphate (9-50 mg/l) are also reported from Champhai valley [34]. Carbonate rocks commonly occur in these sediments as small bands intercalated with sandstones, and concentrations of EC, Cl-, Alk, and TDS are due to the dissolution of natural mineral salts from sandstone-siltstone-shale in the catchment area. Cluster 2 indicates a contribution from surface runoff and soil erosion from the cultivated lands in the catchment area. Agricultural fields such as jhum/shifting cultivation and orchards are commonly practiced in the higher reaches in the area. This indicates the input of suspended particles and thereby increasing turbidity affecting T, DO, and pH values. The turbidity is relatively higher in all the water - - sources barring Changel. Parameters such as NO3 , P, F , and Fe, although of insignificant quantities is correlatable with the composition of the soil of the study area characterized by higher Fe content, acidic, and deficient in phosphate, phosphorous and nitrogen. The anthropogenic inputs such as chemical wastes from industries, fertilization, and sewages seem to be rather unlikely, as there is no industrial installation and human habitation in the catchment area and the area is mostly under thick vegetation cover. Moreover, the concentrations of these parameters are very low and in conformity

337 JECET; JECET; March 2020- May 2020; Sec. A; Vol.9. No.2, 327-341 . DOI:10.24214/jecet.A.9.2.32741.

Physicochemical… Imchen et al. with the values reported from freshwaters from various parts of the world. CA conforms with the FA results. Water quality index: WQI evaluates and ranks the quality of water for use in different purposes. WQI for drinking purpose was computed using 10 physicochemical parameters in mg/l (n=10) such as - - - [35, 36] pH, TH, Cl , DO, NO3 , F , Fe, EC, TDS, and P following weighted arithmetic WQI formula . [7] - BIS values have been used for the computation of WQI. TDS, NO3 , and F were assigned the highest weight of 5 followed by pH, EC, and Fe with a weight of 4 because of their importance in the water quality assessment [37]. The minimum weight of 1 was assigned to Cl- and P. The computed WQI values are classified into five categories: excellent (<50), good (50–100), poor (100–200), very poor (200–300) and unsuitable for drinking (>300) [38]. The WQI of these water sources falls mostly under good quality category baring excellent quality during November 2017 and March 2018 in Chawngtlai, and October in Tuichang water source (Table 3). Table 3: Computed WQI values

Range of WQI & type of Month Changel Chawngtlai Tuichang Chungte water October 56.48 51.70 38.19 52.62 < 50 – Excellent November 58.39 44.89 50.51 56.35 50–100 – Good December 50.52 56.32 58.79 67.30 100–200 – Poor January 60.18 54.90 61.85 70.52 200–300 - Very poor February 57.25 51.86 61.61 81.42 > 300 - Unsuitable for March 50.48 46.24 67.05 74.71 drinking

CONCLUSION

The study concludes that two major sources have largely affected the physicochemical properties and the variability of the surface water i.e. dissolution of mineral salts from the sandstone-siltstone-shale underlying bedrocks, and agricultural activities especially shifting cultivation has enhanced the soil erosion and thereby mineral ions were leached into the surface water along with suspended particles. Besides relatively high turbidity, no anthropogenic pollutants from point source has affected the quality of these water sources. Turbidity treatment through a conventional and cost-effective technique such as settling/filtration/flocculation is warranted. Biological parameters have not been considered in this study; however, WQI computed from physicochemical parameters qualifies the water sources of Khawzawl, Chawngtlai, Tuichang, and Chungte as good to excellent quality suitable for use as potable water. The present work would form a reliable surface water database indispensable for the researchers and stakeholders toward defining adaptive measures and better management of water resources.

ACKNOWLEDGMENT

The authors gratefully acknowledge the authority of the GSI, State Unit: Tripura-Mizoram, Agartala for logistic supports during the course of the study.

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Corresponding author: Imchen, W.

Geological Survey of India, Dimapur, India Date of publication on line 05.05.2020

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