Physico-Chemical Characteristics of the River Kulik of the Uttar Dinajpur District of West Bengal, India

. Abstract The river Kulik is an internationally important river between India and Bangladesh. Till date, no work has been done to understand the physico-chemical characteristics as well as the pollution status of the river Kulik at the Raiganj and Hemtabad blocks in the


Introduction
Water is considered one of the most important of all the natural resources present on earth.It is essential for most ecological systems, all living organisms, food production, human health, and economic development. 1Water is one of the principal natural resources for the survival of mankind and is abundant in the ecosystem. 2Nature contains water in a variety of forms, including lakes, rivers, oceans, clouds, rain, and fog.Nevertheless, in nature, chemically pure water does not remain for very long.Presently, our planet is highly polluted due to industrialization, increased human population, indiscriminate use of fertilizers in agricultural fields, and different anthropogenic activities. 3armers focus on cost-effective water, nutrients, and organic matter sources, neglecting harmful effects like chemical contamination and health issues in agriculture.
The river Kulik is a Bangladesh-India inter-border river that flows through Uttar Dinajpur, West Bengal, India.Kulik which is a short and narrow stream, comes from a marsh in Raipur, Baliadangi upazila, Thakurgaon district, Bangladesh.The Kulik acts as the India-Bangladesh border for a short distance from Haripur upazila before crossing into India.It enters the Uttar Dinajpur district of West Bengal from the south and weaves its way southwest through the lively city of Raiganj to join the Nagar, where fishing is done on a regular basis. 4On the banks of the river Kulik, different crops like paddy, mustard, jute, and wheat are cultivated throughout the year, depending totally on the irrigation water of the river Kulik.Even the water of the river Kulik is consumed by the tribal inhabitants of Sherpur.Although the river is the heart of Uttar Dinajpur District, West Bengal; it's water becomes gradually polluted day by day due to different anthropogenic activities like bathing of both humans and cattle, washing linens and utensils, and disposing of different solid wastes in the water of the river.
The physicochemical properties of the water of the Mouri river in Khulna, Bangladesh, were studied by Kamal et al. 5 Pal et al. and Pal and Talukdar examined the hydro-ecological changes related to damming across the rivers Tangon, Ganga-Padma, and Atreyee in India and Bangladesh. 6,7Different water quality parameters of the river Tangon were also investigated in Bangladesh by Roy et al.In India, many workers studied the physico-chemical properties of different water bodies. 9,10,11,12In West Bengal, Acharjee and Barat conducted research on the spatiotemporal dynamics of physical and chemical elements in the river Relli in the Darjeeling Himalaya. 13The identity crisis in habitat caused by the squeezing of the riparian wetland in the Tangon river basin in the Barind region of India was studied by Chakraborty. 14In the Radhikapur village of the Uttar Dinajpur district, the water quality parameters of the Tangon River were studied by Mondal and Sarkar. 15though the river Kulik is very important for the local inhabitants of the Uttar Dinajpur district of West Bengal, till date no information has been available on the physico-chemical characteristics of the river Kulik as well as the present pollution status of the river.Consequently, to understand the present status of pollution in the river, the primary objective of current research was aimed to investigate various physico-chemical characteristics of the river Kulik at the chosen locations in the district of Uttar Dinajpur, West Bengal, India.

Study Area
For the present investigation, five sampling sites were chosen based on the length of the river and the point and non-point sources of pollution to study the ichthyofauna diversity of the Kulik river in Uttar Dinajpur district, West Bengal (Table 1).

Methodology
Over the course of two years, from November 2019 to October 2021, various physico-chemical parameters of the river Kulik in the Uttar Dinajpur district were investigated.Every month, between the hours of 6 and 10 a.m., water samples were taken from the five designated sampling locations along the river.The air and water temperatures, pH, and transparency were recorded in the field with the help of an ACETEQ digital Celsius thermometer (Model KT-908) with an external sensing probe.The hydrogen Ion concentrations (pH) of water were determined with the help of a portable pH meter (Model-HI96107, HANNA Instrument, Italy).A Secchi disc was used to gauge the transparency and depth of the water following Boyd. 16The BOD samples were placed in the BOD incubator and incubated for five days at 20°C [O-CIS-6(D)] in the laboratory of Department of Zoology, Raiganj University.For the other physico-chemical factors like DO, Free CO 2 , Total Alkalinity (TA), Total Hardness (TH), Total Chloride (TC), water samples were collected and brought to the laboratory in plastic bottles (1500 mL) and analysed as early as possible following APHA. 17he values were compared with the standard values of WHO and CPCB. 18,19Long 88.240520 of Bangladesh and India.At this site, the Kulik River of Bangla -desh enters India (Fig. 1).The water level is quite low at this site.One military camp is present near the site to control the mobility of people from both countries.

GHAT)
Most of the fish of the Kulik River are collected from this site.There are plenty of fish available at this site, and fishing is done here regularly due to the presence of the river buck.The water at this site is used mainly for domestic purposes, especially for bathing pet animals.Site 5 Lat 25.558380This site is located in Nichitpur, which is also a link between (NICHITPUR) Long 88.041977 Bengal and Bihar.This is the outlet of the Kulik River where it meets the river Nagar (Fig. 1).This site is very important for the villagers of the border area of Raiganj and Bihar.Fishing is the main profession of the villagers.

Results
In Figs.2.1 to Table 2.5).ANOVA analysis showed that the variation in Air temperature was significant in the case of seasons at the 1% level (P<0.01).The highest conductivity (0.32 mhos cm-1) was recorded at Site 5 throughout the study period, primarily in the month of April 2021.At Site 5, Electrical Conductivity (EC) was found to be at its highest during the summer (Fig. 2.6).EC was found to be lowest in the month of August, 2021 at Site 2. ANOVA analysis showed that the variation in Electric Conductivity was significant in the case of seasons at the 1% level (P<0.01).
The transparency of water depends on the amount of inorganic or organic particles present in the water.Throughout the duration of the investigation, the transparency of the river's water ranged from 12 cm to 57 cm.The transparency of water was highest in the month of August 2021 (57.00 cm) at Site 2 and lowest in the month of April 2021 (12.00cm) at the same Site (Fig. 2.7).ANOVA analysis showed that the variation in Transparency was significant in the case of seasons at the 5% level (P<0.05).Throughout the entire study period, Site 1 reported the highest DO (13.20mgL -1 ) in the month of December 2019.The lowest value of dissolved oxygen was observed (1.60mgL -1 ) at Site 5 (Fig. 2.9).At Sites 3 and 5, DO significantly correlated positively with both chloride and BOD (Table 2.3 and 2.5.).ANOVA analysis showed that the variation in DO of the river Kulik was significant in the case of seasons at the 1% level (P<0.01).(Fig. 2.10).Free CO 2 showed a positive correlation with chloride and BOD (Table 2.1.to 2.5).ANOVA analysis showed that the variation in Free CO 2 of the river Kulik was significant in the case of seasons at 5% level (P<0.05).
The maximum level of total alkalinity (52.00mgL -1 ) was observed in the month of June, 2020 at Site 4, while the lowest level (12.00mgL -1 ) was recorded in the month of November, 2019 at Site 3 (Fig. 2.

11).
During the study, Total Alkalinity had a significant positive correlation with BOD at sites 1 and Site 5 (Table 2.1 and 2.5).ANOVA analysis showed that the variation in Total Alkalinity of the river Kulik was significant in the case of seasons at 1% level (P<0.01).

Fig.2.12: Monthly variation in Total Hardness at five selected sampling Sites
Throughout the entire study period, Site 2 recorded the highest total hardness (107.00mgL - ) in the month of December 2019, while Site 4 recorded the lowest total hardness (34.00mgL -1 ) in the months of April and May 2020 (Fig. 2.12).The total hardness had a significant negative correlation with BOD (r = -0.3141)at Site 3 (Table 2.3).ANOVA analysis showed that the variation in Total Hardness of the river Kulik was significant in the case of seasons at the 1% level (P<0.01).

Fig. 2.13. Monthly variation in Total Chloride at five selected sampling Sites
Throughout the entire study period, Site 2 recorded the highest total hardness (107.00mgL - ) in the month of December 2019, while Site 4 recorded the lowest total hardness (34.00mgL -1 ) in the months of April and May 2020 (Fig. 2.12).The total hardness had a significant negative correlation with BOD (r = -0.3141)at Site 3 (Table 2.3).ANOVA analysis showed that the variation in Total Hardness of the river Kulik was significant in the case of seasons at the 1% level (P<0.01).

Fig. 2.14: Monthly variation in biological oxygen demand at five selected sampling Sites
In January 2020, the BOD value of Site-5 showed the lowest level ever (1.44 mgL -1 ).The highest BOD (7.68 mgL -1 ) was found in the month of April 2020 at Site 5 (Fig. 2.14).ANOVA analysis showed that the variation in BOD of the river Kulik was significant in the case of seasons at the 1% level (P<0.01).

Discussion
Water quality is generally defined as the chemical, physical, and biological properties of water based on the criteria of its utilization.Temperature fluctuations play an important role in climate variability, necessitating the need to continue tracking temperature patterns even in places where a temperature pattern has been identified by Oyewole. 20Water temperature is significant for its influence on chemical and biological processes in organisms. 21Water temperature is one of the most crucial environmental elements impacting aquatic ecosystems and physico-chemical parameters, according to Bellos and Sawidis. 22Ahipathy and Puttaiah noted that the season, location, sample duration, and temperature of effluents entering the stream all play a significant role in the variation in the temperature of the river. 23Both the minimum air and water temperatures were found during the winter, and the maximum was recorded during the summer months (Figs.2.1 and 2.2) At each location, there was a sizable positive association between air and water temperatures: r= 0.9481 (Site.1), r= 0.9425 (Site.2), r=0.9578 (Site.3), r=0.9632 (Site.4), and r=0.9774 (Site.5).The air temperature and water temperature were positively and significantly correlated at each location (Tables 2.1, 2.2, 2.3, 2.4, and 2.5).Similar findings were recorded by Mondal et al. in the Mirik Lake of the Darjeeling Hills. 24At all locations, water temperature had a negative correlation with pH (Tables 2.1, 2.2, 2.3, 2.4, and 2.5), like Mondal. 25e pH values of the present study varied from 5.90 to 7.86, indicating a slightly acidic to slightly alkaline nature of the water (Fig. 2.4).The pH showed a significant negative correlation with BOD at Sites 2, 3, 4, and 5. Tajmunnaher et al. also observed a negative correlation between pH and BOD in the Kushiyara river, Sylhet, Bangladesh. 26During the summer, the pH value was found to be higher, which corroborates the findings of Krishnaram et al. 27 The pH showed a positive correlation with electrical conductivity (Tables 2   Total Dissolved solids are a nutrient that regulates the biological and physical quality of water. 29A rise in TDS indicates contamination by extraneous sources, which has a negative impact on the quality of natural water. 30TDS and total alkalinity displayed a strong and positive association at Site. 1 (r = 0.6306), Site. 2 (r=0.5825), and Site. 5 (r=0.4345)(Table 2 The highest conductivity reading recorded at Site 5 in the summer months (Fig. 2.6) might be attributed to human influence.Tripathi et al. also found higher values of conductivity in the summer months. 32n the current research, the EC of water exhibited a strong positive correlation with total hardness (Tables 2.1 and 2.2) and chloride (Table 2.4) An analogous observation was also recorded by Kumar  et al. in the middle of the Gangetic Plain. 33At every site, transparency and DO showed a substantial positive association throughout the whole study period (Tables 2.1, 2.2, 2.3, 2.4, and 2.5).A similar observation was also recorded by Zhenghu et al. at Shahu Lake in China. 34At every study site, depth significantly positively correlated with total alkalinity.Similar findings were recorded in the river Kushiyara of Bangladesh by Tajmunnaher and Chowdhury. 26 a result, oxygen availability is considered a key component in hydrobiology, impacting organism function, community organization, and local diversity. 35According to Ansari and Raja, fluctuations in DO levels were caused by the solubility of oxygen in water, the intensity of light, and photosynthesis. 36According to Banerjee, an annual DO concentration of around 5.00 mgL -1 was determined to be appropriate for fish culture. 37he highest DO (13.20 mgL -1 ) was recorded from Site 1 in the month of December, 2019.Alam et al. also observed the highest DO values in December in the case of Hilnabeel, Bangladesh. 38The quantity of oxygen in the river Kulik is determined by the area of water-air contact, water circulation, and the amounts generated and consumed within each site.The lowest values of DO at Site 5 (1.60 mgL -1 ) were much lower than the drinking (Fig. 2.9) and bathing water standards set by the CPCB and the drinking water standards set by the WHO. 19,18At Sites 3 and 5, DO significantly correlated positively with both chloride and BOD (Fig. 2.9).Similar findings were made by Bose and Gorai at Dhanbad and Pillai et al. in the coastal waters of the South-West coast of India. 39,40rbon dioxide is present in water as dissolved gas.
For aquaculture, the limits of free carbon dioxide are 1-10 mgL -1 , according to Boyd and Tucker. 19Free CO 2 showed a positive correlation with the chloride and BOD of water in the present investigation.Similar observations were recorded by Huq at Kumari Beel, Bangladesh. 41tal alkalinity limitations for aquaculture are 50-300 mgL -1. 16The total alkalinity values of the present study (12.00 mgL -1 to 52.00 mgL -1 ) were within the limit (Fig. 2.11).The lowest alkalinity (12.00 mgL -1 ) was recorded during the winter months (Fig. 2.11), which may be due to the 'dilution effect'. 42Alkalinity and BOD had a strong positive association in the current study.Sharma and Jindal also found similar observations in the river Sultej of Ludhiana. 43cording to Boyd and Tucker, TH levels of 50-200 mgL -1 are appropriate for aquaculture. 16Over the course of the investigation, the highest total hardness value (107.00 mgL -1 ) recorded at Site 2 in the month of December 2019 might be linked to a combination of elements such as the minimal water level of the river, the higher temperature, and the salts of calcium and magnesium added by soap and detergents utilized for laundry and bathing.The lowest value (34.00 mgL -1 ) of the total hardness was recorded in the months of April and May 2020 (Fig. 2.9), which could be attributed to lesser human activities during the Lockdown period due to the COVID-19 pandemic situation.The total hardness had a significant negative correlation with BOD (r = -0.3141)at Site 3. Similar findings were recorded by Risner at the Albama and Dog River Watersheds. 44loride concentration indicates the level of pollution. 45igher chloride concentrations are linked to higher levels of pollution. 46,47Chloride is expelled as nitrogenous chemicals in water bodies. 48The most significant source of chloride in naturally occurring freshwater is the outflow of household sewage, and a high chloride concentration indicates sewage contamination. 49Chloride had a significant positive correlation with BOD (r = 0.3012) in Site 4 (Table 2.4) and (r = 0.3005) at Site 5 (Table 2.5).A similar type of positive correlation was recorded by Tripathi et al. from the river Ganga at Holy Place Shringverpur, Allahabad, and by Bhandari and Nayal at the Kosi river, Uttarakhand. 32,50e highest BOD (7.68 mgL -1 ) was found in the month of April, 2020 at Site 5 (Fig. 2.12), which was much greater than the drinking and bathing water standards set by CPCB. 19The higher BOD values may be associated with organic pollution caused by sewage contamination through incoming drains.
According to Wahid et al., a BOD value greater than 7.00 mgL -1 is indicative of pollution. 51BOD levels between 2.00 mgL-1 and 4.00 mgL -1 are acceptable, while levels above 5.00 mgL -1 indicate serious pollution. 52

Conclusion
The present investigation revealed the current physico-chemical status of the water in the river Kulik of the Uttar Dinajpur District.Although the values of different parameters of water quality such as pH, chloride, TA, and TH of all five sampling sites in the Uttar Dinajpur district are within the recommended limits (drinking water standard) set by WHO, most of the time the dissolved oxygen values of Site 5 were lower than the drinking and bathing water standards set by CPCB and the drinking water Standard set by WHO.The highest BOD was recorded from Site 5, which was much greater than the drinking and bathing water standards set by CPCB.From the overall study, it can be concluded that Sites 3, 4, and 5 were more polluted than the other sites.The higher pollution levels at these sites may be due to higher levels of anthropogenic activities and poor maintenance of the water.Nonetheless, it is imperative to explore more chemical compounds to find out the overall water quality of the river Kulik.
To control the discharge of garbage from homes and agricultural fields next to the river, public awareness is crucial.In order to protect the water quality of the river, sand lifting from the river should be reduced.This research can be helpful in developing strategies for ecological management, conservation, and restoration.

Fig. 2 . 2 :
Fig. 2.2: Monthly variations of water temperature at five selected sampling Sites.The months of May 2021 and January 2021, respectively, showed the highest (32.10°C) and lowest (12.0°C) recorded water temperatures (Fig. 2.2) from Site 4. At three sites, water temperature significantly correlated negatively with pH and positively with depth, r = -0.4154(Site 1), r = -0.6069(Site 2), r = -0.5311(Site 4) (Tables 2.1, 2.2 and 2.4).ANOVA analysis showed that the variation in Water temperature was significant in the case of sites at the 5% significance level (P<0.05) and seasons at the level of 1% (P<0.01).

Table 1 : Brief descriptions of the five sampling sites of the river Kulik
The human population is lower at this site.Only some agricultural fields and different plants are present near the site.Fishing is done at this site.
31).Similar observations were recorded by Kothari et al. at different water bodies in Uttarakhand.31