Arsenic contamination in surface and groundwater in major parts of Manikganj district , Bangladesh

The contamination of groundwater by arsenic (As) in Bangladesh is the largest poisoning of population in history, with millions of people exposed. Thirty (30) water samples were collected from 5 different Upazilas of Manikganj district in Bangladesh to determine the concentration of As as well as to assess the level of contamination. Concentrations of As in waters were within the range of 0.27 to 1.96; 0.43 to 5.09; trace to 6.69 mg L at Singair, Harirampur and Ghior Upazila, respectively. But the concentration of As in waters both of Manikganj sadar and Shivalaya Upazila were trace. All surface and groundwater samples of Singair and Harirampur, and 4 groundwater samples of Ghior Upazila’s exceeded Bangladesh standard value for As concentration (0.05 mgL). The highest As concentration (6.69 mgL) was found in groundwater of Baliakhora village of Ghior upazila in Manikganj district. The cation chemistry indicated that among 30 water samples, 15 showed dominance sequence as Mg > Ca > Na > K and 14 samples as Ca > Mg > Na > K. On the other hand, the dominant anion in water samples was Cl followed by HCO3 and SO4. Highly significant positive correlations were found in between the concentrations of As and SO 4 (r=712**), and As and Ca (r=581*), suggesting similar sources and/or similar geochemical processes controlling the occurrence of these ions in waters.


Introduction
Arsenic is a metalloid which is widely distributed in the environment.It is recognized as one of the world's greatest environmental hazards, threatening the lives of several hundred million people.However, in terms of population exposure the most severe case of such contamination is observed in Bangladesh where it is considered to be the largest mass poisoning in history.Evidences of high soil and plant arsenic levels have been found due to the introduction of arsenic-contaminated water in crop fields.Again, there is a possibility of using the contaminated water for cooking.As a result, even more people are exposed to toxic level of As through food chain (Imtiaz et al., 2009).
Data collected from different governmental bodies, NGOs and private organizations reveal that a large number of populations in Bangladesh are suffering from melanosis, leuco-melanosis, keratosis, hyperkeratosis, dorsum, non-petting oedema, gangrene and skin cancer (Karim, 2000).The occurrence of arsenic diseases depends on the ingestion of arsenic compounds and their excretion rate from the body.It has been reported that 40-60% arsenic can be retained by the human body after ingestion (Farmer and Johnson, 1990).Due to the widespread use of As contaminated ground water in drinking, cooking, agriculture, etc.As can reach to human body from many possible routes, by which the daily dietary intake of As may exceeds the WHO recommended limit (2.14 µg kg -1 of the body mass) (Imtiaz et al., 2009).Manikganj is one among the As contaminated districts of Bangladesh and thousands of peoples are affected over there by As contamination.Groundwater is the main source of As contamination in this district.If such condition prevails for long time peoples of that area will be affected seriously by arsenicosis.Considering the above facts, the research work has been carried out to determine the concentration of As and to assess the level of contamination in waters collected from five (5) different Upazilas of Manikganj district of Bangladesh.

Materials and Methods
A total of 30 water samples were collected from 30 locations of 5 different Upazila's of Manikganj district during the month of February, 2013 following the sampling techniques as outline by APHA (1995) and Sincero and Sincero (2004) (Table 1).The water samples were taken in 500 mL plastic bottles, which were cleaned in the laboratory with dilute HCl (1:1) and then rinsed twice with distilled water.Before sampling, bottles were also rinsed with the sampled water.The bottles containing water samples were sealed immediately to avoid exposure to air and marked with necessary information.
In the laboratory, the water samples were filtered through Whatman no.42 filter paper to separate undesirable solid and suspended materials.Then the samples were analyzed for pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), major cations (Ca 2+ , Mg 2+ , Na + and K + ) and major anions (Cl -, CO 3 2-, HCO 3 -, SO 4 2-and PO 4 3-) at the laboratories of the Department of Environmental Science and Resource Management, Mawlana Bhashani Science and Technology University, Tangail-1902 and the Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh-2202.Calcium and magnesium were determined titrimetrically using standard Na 2 EDTA (Ghosh et al., 1983;Page et al., 1989).Chloride was measured by titrimetrically using standard AgNO 3 solution.Carbonate and bicarbonate were also determined by titrimetrically using standard H 2 SO 4 solution (Ghosh et al., 1983;Singh et al., 1999).Sodium and potassium were measured by flame photometrically whereas sulphate and phosphate were determined by spectrophotometrically (Ghosh et al., 1983;Tandon, 1995;Singh et al., 1999).The concentration of arsenic in water samples were analyzed by atomic absorption spectrophotometer by using the single element hallow cathode lamp at the wavelength of 193 nm following the procedure as described by APHA (1995).

Results and Discussion
The results of the analysis of water samples collected from 5 different Upazila's of Manikganj district, Bangladesh is given in Tables 2 (a-e) and in Figs. 1 (a-c).

Physicochemical properties of water
The pH of water samples collected from 5 different Upazila's of Manikganj district were slightly alkaline in nature (7.04 to 7.99) and data are presented in Tables 2(a-e).These might be due to the dominance of ions such as Ca , Mg and Na in water (Rao et al., 1982).
The acceptable range of pH for drinking water is 6.5 to 8.5; recreational water is 6.0 to 9.5; industrial water is 6.0 to 9.5; livestock water is 5.5 to 9.0 (ADB, 1994).On the basis of measured pH most of the samples were within the acceptable range.
Electrical conductivity (EC) represents the total concentration of soluble salts in water.The EC of all collected water samples from different Upazila's of Manikganj district were within the range of 27 to 82 µScm -1 (Tables 2a-e).The acceptable range of EC for recreational water is 500 µS cm -1 , irrigation water is 750 µS cm -1 and fishing water is 800 to 1000 µS cm -1 (ADB, 1994).And the measured EC of all samples collected from different Upazila's of Manikganj district were below the acceptable range.The DO of all water samples varied from 3.2 to 8.0 mgL -1 (Tables 2a-e).According to the United States Public Health (USPH) and Indian Standard Institution (ISI), the acceptable range of DO for domestic water supplies is 4.0 to 6.0 mgL -1 and 3.0 mgL -1 , respectively (De, 2005).The acceptable range of DO for fish culture is from 5 mgL -1 to saturation (Meade, 1998) and more than 5.00 mgL -1 (Chowdhury, 2007).TDS values of water samples collected from different Upazila's of Manikganj district were within the range of 173 to 529 mgL -1 (Tables 2a-e).The acceptable standards of TDS for drinking water is 1000 mg L -1 , industrial water is 1500 mg L -1 , livestock water is 5000 mg L -1 and irrigation water is 2000 mg L -1 (ADB, 1994).On the basis of measured TDS all samples collected from Manikganj district were within the acceptable range.

Relationship between arsenic and other ionic constituents
Correlation matrix for analyzed parameters of water were calculated to see whether some of the parameters were interrelated with each other and the significant results are presented in Figures 2(a & b).
Examination of the matrix also provides clues about the carrier substances and the chemical association of ionic constituents in the study area (Jaquet et al., 1982).Among the relationships between the concentration of As and other physicochemical parameters of water, highly significant positive correlations were found with SO (r=712**) and

Conclusion
Concentrations of As in waters collected from Singair, Harirampur and Ghior Upazila of Manikganj district were within the range of 0.27 to 1.96; 0.43 to 5.09; trace to 6.69 mg L -1 , respectively.But the concentration of As in waters both of Manikganj sadar and Shivalaya Upazila were trace.The present study also revealed that among the 30 water samples studied, 18 samples collected from Singair, Harirampur and Ghior Upazilas of Manikganj district had arsenic, which exceeded Bangladesh standard limit for arsenic concentration (0.05 mgL -1 ).The highest arsenic concentration (6.69 mgL -1 ) in water was found in the Baliakhora village of Ghior upazila in Manikganj district.So, arsenic concentration in these waters are harmful for human health and livestock.On the other hand, the observed arsenic values of water of 3 villages of Ghior Upazila, 5 villages of Manikganj Sadar Upazila and 4 villages of Shivalaya Upazila in Manikganj district were negligible.However, the population exposed to the arsenic contamination should be advised about the arsenic in drinking water, the sources of arsenic-free water and the importance of compliance with treatment programs.

Fig. 1a .
Fig. 1a.Arsenic concentrations in water samples collected from different villages of Singair Upazila of Manikganj district.

Fig. 1c .
Fig. 1c.Arsenic concentrations in water samples collected from different villages of Ghior Upazila of Manikganj district.

Fig. 2 .
Fig. 2. Relationship between arsenic vs sulphate (a) and arsenic vs calcium (b) obtained for water samples collected from different locations of Manikganj district