当前世界环境

Introduction

孟加拉国主要是一个农业的基础country within the south Asian region. Chittagong is the second largest and commercial capital in respect of developing and expanding among the cities of Bangladesh. Due to expedition of these city industrial activities, population growth, Agricultural practices, other manufactures, industrial effluents and oil and gas are discharged in a river named Karnafuly. Different estuary of river present in Bangladesh and among them Karnafully is the most important one of them. This estuary is the meeting point in where salt water from sea and upstream fresh water is continuously mixing. Not only for the purpose of drinking but also for the household activities as well as livelihood people of this area mainly depend on Karnaphuli River. In most of the developing countries their industrial wastewater and contaminated effluents routinely discharge in either nearby river, drains or increase sewage sludge contamination level¹．Like this a large of number of garments factories, different public and private fertilizer factories, many national and international chemical industries have been established after the independence of Bangladesh on both side of Karnafuli river. As a result wastewater and contaminated byproduct of these river bank industries are directly discharged into Karnafully River through Mazirghat, Chaktai, Noakhal, Sundari, Gupta, Shikalbhaha, Ferighat and Mohesh and result pollutant load in this important river is increasing day by day. But water is the most remarkable commodity and essential to all life, both animals and plants²．Man can go nearly two months without foods, but can live only three or four days without water³．Contaminants of factories either urban or agriculture sources is continuously entering the food chain and decreasing the water quality⁴．Many works on heavy metal concentration in water, soil, fish has been done but works on water quality parameters variability of Karnafully River is not perform yet. Keeping this in mind our present research work has been conducted to examine the variation of the water quality parameters during winter to summer season of Karnafully River.

Materials and Methods

Sampling Area

Three sampling area in Karnafully River was selected as Shah Amanat Bridge (22°19'34.4"N 91°51'12.0"E), Firingi Bazaar (22°19'32.9"N 91°50'13.2"E) and Kalurghat (22°23'46.1"N 91°53'19.1"E). Map of sampling area of Karnafully River are shown fig. 1

Figure 1: Sample collections area in Karnafully River of Chittagong city in Bangladesh. Click here to View figure

Sample Collection

Water samples from three selected points of Karnafully River were collected. Samples were collected in month of January 05, 2014 to June 05, 2014. Total three samples from three points of 5^thday of every (January to June) month were collected and in that way total eighteen water samples in six month were collected. The samples were tightly caped without any air gap. Then water samples brought to laboratory and analyzed by different prescribed method.

Sample Analysis

Total eight water parameters were determined for analysis of water parameters variation. Parameters were pH, EC, Cl^-, As, Fe, Total Hardness, and Turbidity. Arsenic and Iron were determined by Atomic Absorption Spectrophotometer (AAS) and pH, EC, Cl^-, Total Hardness, Turbidity were determined by prescribed method of Huq and Didar⁵．

Statistical analyses

For the data analysis Microsoft Excel 2007 and SPSS 16.0 has been used.

Result and Discussion

Variations of pH, Conductivity (mS/cm), Fe (mg/L), As (mg/L)

pH of collected water samples varied from 6.86±0.007 to 7.20±0.12 from January to June (Figure 2[A]). With time the pH of Karnafully River increased from January to June that might be due to the receipt industrial discharge in which present more bicarbonates as well as carbonates and attenuating the discharge from sweater factory. The results showed that water was slightly acidic to slightly basic and which is very beneficial for fresh water fauna and flora. Variation of pH values during winter to summer season were attributed to factors like as consumption of CO₂by photosynthesis, OM degradation, dilution effects of waste water with fresh water, temperature and salinity attenuation⁶．In Chittagong city has large number of garments factory mainly sweater factory but in winter season its production increased five times more than other season and at that time the basic chemical used are mostly acid types as a result the effluents are acidic that might be the reason for decreasing of water pH in winter. The pH values for all collected water samples were within the standard pH values recommended by WHO⁷and the pH ranges from 6.5 - 8.5. Electric conductivity of the Karnafully River water samples were differed from 0.6±0.03 mS to 24.58±0.67 mS (Figure 2[B]) from January to June respectively and the highest values was obtained in January that might be due to the increased the volume of industrial discharge in winter but volume of water transportation in river is decreased at that time. The result obtained for EC in this study exceeds the recommended limit of DoE (Department of Environment) standard of Bangladesh in most of the month from January to June 2014⁸．Conductivity of water in Karnafully was decreased significantly (Table 1). Iron range varied from 3.05±0.07 mg/L to 0.16±0.02 mg/L (Figure 2[C]). Among the above three parameters, pH did not make vigorous change but other two parameters attenuated during January to June (Figure 2[D]). Another parameter As concentration, which was nil throughout the all month. WHO⁷recommended limit for arsenic is 10μg/L and it’s safe for drinking purpose. Ground water of Bangladesh is very arsenic contaminated⁹so river water should be the alternative source of drinking water and agricultural use for the people of Chittagong after purification.

Figure 2: Fluctuation of pH (A), EC(B), Fe(C) and comparison among these parameters (D) during January to June 2014 of Karnafully River. Errors bars indicate the standard deviation of mean value. (n=3) Click here to View figure

Variations of Turbidity (NTU), Total Hardness (mg/L),Cl^-(mg/L),TDS (mg/L)

increa Karnafully河流水的浊度sed from January to June and ranged from 2.56±0.28 NTU to 711±24.04 NTU from January to June, 2014 (Figure 3[E]). In case of inland surface water, for Bangladesh Standard, TDS is 1000 mg/L. TDS of Karnafully river water samples was found to decrease in order throughout the month from January to June of 2014 (Figure 3[F]) which ranged from 7630±2036.5 to 270±70.71 mg/L. Higher values of TDS might be due to not only waste particles but also the presence of silt, clay in the river water from different sources. TDS values of Karnafully River water samples exceed the standard limit for inland surface water and the result was significant (Table 1). Hardness (Figure 3[H]) was measured highest in January (1781.2±482.53mg/L) and lowest in June (102±5.66mg/L), Kaur and Sharma¹⁰reported maximum hardness in summer which contradicted with our findings that might be due to least flow of water in Karnafully in compare to summer but discharge from industry was higher than that of other season. Total Hardness of water samples from January to March exceeds the permissible limit (300mg/L) by WHO⁷．Rajagopal¹¹suggested that decreasing water volume in river, presence of detergent and chloride, improving load of organic substances and other pollutant might be reason of improving hardness level. Concentration of Cl^-in water indicates animal origin organic substances¹²．Chloride concentration was decreased from month as January to June and the value of chloride was significant. Highest chloride concentration was obtained in January (5485.89±1351.11mg/L) but least was observed in April (79.76±2.52mg/L). Chloride concentration increased in winter due to more discharge of garments and different industrial waste has been reported¹³．Only for month of January, March and May, Chloride concentration (Figure 3[G]) exceeds the permissible limit recommended by WHO⁷(250 mg/L). In figure 3[I] showed that comparative fluctuation of different water quality parameters from month of January to June in 2014.

Figure 3: Variation of Turbidity [E], TDS [F], Total Hardness [H], Cl-[G] concentration and comparison among these parameters [I] of Karnafully River of Chittagong, Bangladesh during January to June 2014. Errors bars indicate the standard deviation of mean value. (n=3) Click here to View figure

Table 1: Pearson correlations co-efficient among the water quality parameters of Karnafully River

*Correlation is significant at the 0.05 level
**Correlation is significant at the 0.01 level

Conclusion

All the parameters except pH were decreased throughout the month from January to June in 2014. In winter low turbulence and velocity in Karnafully River and carry low volume of water compare to other season but no change of discharge from industry of Chittagong city which might be the possible reason of fluctuation of the water quality parameters.

Acknowledgement

We are grateful to BCSIR Laboratories Chittagong for the logistic support to conduct our current research work.

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