Calculation of Quality Indices and Correlation Factors at Some Effluents Entry Points of the Mansagar Lake, Jaipur

With this article, impact of effluent mixed water with the quality of the Mansagar Lake has been established by evaluating the physico-chemical parameters and the heavy-metal contents experimentally. The process of calculating water quality and the metal pollution quality indices is also explained in brief with respect to selected sample locations and varied environmental conditions (Pre- and Post-Monsoon season). Distribution trends of Pearson‘s correlation factor have also been discussed to establish their relation among the physico-chemical parameters and the heavy-metal contents for varied environmental conditions. In the end, detailed discussion on observations made during this study and useful recommendations are also elaborated in details. With this article, we intend to present a document for better understanding of the water quality of this lake in view of futuristic management strategies to be adopted to maintain it heritage values.


GENERAL CONCEPTS ABOUT POLLUTANTS IN URBAN LAKES AND THE STUDIED LAKE:
The survival and multiplication of microorganisms in urban lakes is influenced by various factors of which nutrients and Oxygen are the most important one. Perhaps, presence of ammonia in excess also generates pollution threats for lakes and ponds. The temperature, pH, light suspended matter, total dissolved solids (TDS), toxic inorganic and organic compounds are other important factors influencing growth of microorganisms. The types of organic compound available as well as nitrogen and phosphorus play important role in the biomass formation and depletion of oxygen. Other water contaminants also accumulate in the soil over the period of time and turn the soil unfit for agriculture. Most of the water bodies in the city of Jaipur and nearby regions have been facing problems of ever-increasing levels of the nitrate and phosphate from other sources. The studied lake; Mansagar Lake with a palace in the middle is situated in the north part of the Jaipur City was built in the year 1610 [7].
As shown in the figure 1(a), the lake is surrounded by hills from three sides. It can be defined by its depth (1.5-4.5 in meters), surface area (139 hectares) and the catchment area, which is 23.5 sq. km [4][5]. The state Government and local municipal agencies have been working hard to manage its heritage value and to maintain the quality of its water since last 2 decades. Even then, excess tourism activities, uncontrolled waste mixing and untreated sewage from nearby residents and local industries have been challenging issues since long. Continuous variation in physico-chemical parameters and constituent metal pollutants water make its uses difficult for domestic purposes and posing serious health hazard to living beings. Its water quality deteriorate more often due to nearby effluents especially in rainy days, whereby the pollutants and hazardous metallic contents mixed with it via rainy water from adjoining rough areas and the roads. Also rain on nearby hills has been a primary cause for the soil erosion and to transfer the silt deposit in the lake thereby reduces its coverage area and affect the water quality severely [7]. This is a continuous phenomena going with the studied lake since long. The location (station: E 3 ) was also suitable in view to check the soil erosion effects and its impact on the lake environment. As discussed in [4][5][6][7], standard processes and methodologies were applied to evaluate the physico-chemical parameters and metal constituents for samples collected from stations; E 1 , E 2 , and E 3 . Table 1 depicts evaluated physicochemical parameters, organic effluents and other pollution contents for these chosen locations. The table is reproduced from earlier reported work [4] with some parameters close to their two decimal values only. Large variations were observed within the physico-chemical, biological and bacteriological parameters, which also indicate that the Jalmahal (Mansagar) lake prevailing a non-uniform nature of the water quality. Tabulated parameters also confirm presence of contaminations at all sample locations due to higher chemical Oxygen demand (COD) levels, while dissolved Oxygen (DO) levels remains at lower side at E 1 station. We also observed slight variation in the pH values in a range 6.70 to 7.58, which is suitable range for fishes to grow in the water. The observed variation in pH can be due to atmosphere, biological activities and temperature changes.
Similarly, the observed DO levels can be used to determine that the changes in the biological properties of water and it should be 4mg/l for aquatic water. The dissolved oxygen of water is introduced through air or photosynthesis. The oxygen contains reduced due to organic matter, rise in temperature and due to inorganic compounds like H 2 S, NH 3 , NO 3 and ferrous Iron. In most observed samples, the DO value is found low, which may impacting the WQI of the aquatic water. Other physico-chemical parameters, which were evaluated from the collected samples, were conductivity, total organic carbon (TOC), Ammonical Nitrogen, Nitrate (NO 3 ) and Phosphate (PO 4 ). Chloride is the most common inorganic compound and is found in practically in all natural sources of water. Man and animals excrete high quantity of Chloride. Also, the higher values of the Biological Oxygen demand (BOD) at stations at the edges impacting the WQI values, while the turbidity is not found as the impactful factor on calculation of WQI as compared to the measured values of TDS. The discharging of impurities from anthropogenic activities and run off from rain water and closing of tertiary treatment plant is the main factor for contamination. As compared to our previously reported work [4], we extended the work by evaluating additional performance parameters such as Phosphate, Nitrate and Total Kjeldahl Nitrogen (TKN) contents to define quality characteristics parameters. Usually typical range is 35 to 60 mg/L for TKN in urban water bodies, which defines organic nitrogen and ammonia presence with their surface water. For our study with the Mansagar Lake, the TKN values found in the prescribed range only, with a little increasing pattern during post-monsoon sampling time. The chloride contents found more in pre-monsoon days, which may react with Mn to form MnCl 2 and other dangerous mixtures, which may becan be detrimental. The coliform bacteria (E. coli) are present in all water bodies and its higher concentration indicates more contaminated water quality. Its high value is not suitable aquatic species and thereby increases the possibility of disease spreading among them. This may enter into the lakes through waste produced by the municipal, farm, animal and human and other outdoor activities. With our study, we also observed that most of the nonpoint sources create significant effects on bacterial level in the water.
We also noticed presence of micro-organisms, indicating coliform bacteria existence within the lake water. In our study, we recoded the fecal coliform density as the number of organisms less than 23 per 100 ml. It is clear, that traced presence of Coliform bacteria are not creating life threatening situations, however its presence may be an indication of pathogens, which may cause water borne diseases. We also noticed that the Ammoniacal nitrogen quantity is in permissible limit for outlets of nearby sewage treatment plant, however harmful for fishes. On the contradictory, levels of the Phosphate and TKN were found relatively high. The maximum level of phosphorous needs to be at 0.03 mg/l, naturally in water phosphate lies in the range of 0.005 to 0.05 mg/l. We also noticed increase in the levels of phosphorus and nitrogen increases during post-monsoon days/months. Mn and Na resulted in aquatic living beings in huge numbers, which attracted many environmentalists to study causes to alarm the bell. On the other hand, higher levels of Na also have impact on lake bed soil quality. With the experimental exercises, we noticed variation in the range from 121 mg/L -252 mg/L and in the range 10 mg/L -60 mg/L for evaluated Na and K respectively, which may be due to runoff from the sewage lines, washing activities and flooded rain water in the lake. We observe higher concentration levels of Na & K, which eventually affecting the aquatic animals and plants We have analysed the overall water quality using important parameters; temperature, Nitrate, Phosphate, DO, pH, TOC, turbidity, etc. by associating the water quality (Q) and weighing factor (w). Detailed weighted arithmetic index method to calculate the WQI can be referred from our previous work [7] and theories mentioned with [8][9]. With this work, we also focused on demonstrating the WQI values describing the spatial and temporal water quality information. The metal pollution index (MPI) is calculated to determine the quality of the water and its suitability for aquatic purposes [16][17][18]. We have calculated the MPI as per the standard model in use [11][12], while taking in consideration various inorganic and metal constituents such as Iron, manganese, lead, copper, nickel, cadmium, chromium, zinc, etc. These performance (WQI and MPI) facts may also be utilized to narrate requisite concrete planning for restoration of the lake. The standard values for common heavy metal constituents in lake water are listed in the table 3. This table is prepared with the report released by WHO and BIS in past [14][15], [19][20][21][22]. The values for some parameters may vary in accordance to the intended use of the water such as for drinking and irrigation purposes, aquatic life and as per the level of the water: surface or ground water [23][24][25][26]. The metal pollution index has been calculated by; Where M i , M s and M id are monitored, standard and ideal values of i th parameter respectively. A comparision between the evaluated metal concentrations with their maximum permissible limit (M s ) defines the quality [23][24][25][26]. Metal quality index (MQI) value >1 is a threshold of warning [13]. According to [14][15], the MQI is calculated by;

DETERMINITATION OF WATER QUALITY INDEX:
As described in previous paragraph, the calculation of WQI using the evaluated physico-chemical parameters has been completed. The lake water has been subjected for analysis of various physiochemical parameters such as pH, turbidity, water management techniques to be adopted for taken care of its water quality.         In urban areas with random environmental conditions, heavy metals constituents of water bodies can interact with each other and may subsequently transformed in different phases [27][28]. Such phase transform can alter biogeochemical behaviors of the metal's constituents of a water body due to their changed response to environmental variations [29].   On the other hand, the association of the Cr with Cu, K, Mn, and Ni is very strongly negative; almost inversely proportional to each other. To best of our knowledge, first time a detailed study has been done for the correlation analysis of metal pollutants (i.e., Cr, Cu, Na, K, Ca, Fe, Mn, Ni, Pb and Zn) for varied environmental conditions for the Mansagar lake water quality. This interpretation of associationship among evaluated parameters from collected samples during pre-monsoon season can also be defined for data given in the table 8. We may also notice interesting observations by comparing and correlating the values of ‗r' from table 7 and 8, some of which are listed below;  The associationship of the Cr with Cu remain same (very strong positive), while with Mn and Ni, the associationship is very strong negative irrespective of changes in the environmental conditions.
 The association of Cu with Fe is very strong positive and with Mn always above string positive in both seasons.
 The associationship of K with Ca and Zn remains very strong negative irrespective of seasonal variations.
Similarly, the relationship of Ca with Mn and Ni remains very strong negative in all whether situations.

CONCLUSION:
With this article, we have discussed calculation of quality indices (water quality index, metal quality index) and Pearson's correlation factors. A detailed description for calculation of quality indices and correlations among the physicochemical parameters and constituent metal contents has also been presented. The evaluated quality indices may help to define guidelines to manage and maintain the lake and surrounding environment. On the other hand, evaluated correlation factors can be used to predict associationship between various physico-chemical parameters and among the metal constituents. We emphasized to study these objectives for a satisfactory period considering current situation of the water body and the transboundary waters by taking into account the water quality flowing through its catchment area. We also observed that many chemical substances emitted into the surrounding environment including the Lake from anthropogenic sources posing threats on the aquatic habitats. The need of the hour is to take tough steps to control the discharge of such pollutants into the lake. ACKNOWLEDGEMENT: We are grateful to the Labs of MNIT Jaipur and the Department of ESE, IIT-ISM Dhanbad for technical support and to the Rajasthan Government agencies for permitting us to carry out this study.