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Evaluation of Groundwater Salinity and Arsenic Contamination and Its Environmental Impact in Shyamnagar Thana of Satkhira District, Bangladesh

S.M. Shafiuzzaman
Institute of Environmental Science (IES), University of Rajshahi Rajshahi-6205. Bangladesh.

Abstract/ Executive Summary:

Groundwater quality is rapidly decreasing in alarming rate due to surface water pollution by the tremendous pressure of human activities. Groundwater in the study area is generally high salinity contaminated and peoples are facing drinkable safe water crisis. There are 12 groundwater samples have been collected from the different well locations of Shaymnagar Thana for hydrochemical analysis. The result shows that salinity and arsenic level are objectionable in most of the samples. Salinity is high which ranges from 0.4 ‰ to 3.5 ‰ with an average of 2.35 ‰. The average EC is 5912.25µS/cm exceed the WHO permissible limit, 2006 and DoE, 1997). High TDS, Na+ , Cl- indicate high salinity in groundwater of the study area. Concentration of arsenic ranges from 0.009 to 0.078 mg/l, with an average of 0.052 mg/l which exceeds only the DoE permissible limit, but well above the WHO’s limit. To know the behavior of salinity and arsenic, few parameters especially pH, Ca2+, Mg2+, K+ , HCO3 2+, NO3 + , SO4 2+ and Fe value have also been used, most of which were within the limits of WHO’s standard except HCO3 2+. High salinity adversely affects the flora, fauna including human and infrastructures in the study area. Groundwater quality is unsuitable for drinking and agricultural purposes in most of the area and could be allowed alternative water resources.

Keywords: Groundwater, Salinity, Arsenic, Environmental Impact, Bangladesh.

Location: A part of Bengal basin and lies in the southwestern portion of Satkhira district of Bangladesh

Start Date: 00-05-2011

End Date:

Program Area: Risk Management in Agriculture

Commodity: Groundwater, Water salinity, Arsenic

Objectives:

In the study, arsenic and salinity effect on the local environment have been assessed based on the field observation.

Methodology:

2.1 STUDY AREA The study area is a part of Bengal basin and lies in the southwestern portion of Satkhira district of Bangladesh and is located between latitude 22°10´ and 22°26´ N and longitude 89°00´ and 89°18´E. The area is a coastal adjoining area covering an area of about1968.28 sq.km. and is bounded by Kaligonj and Assasuni Thana on the north, Sundarbans and Bay of Bengal on the south, Koyra and Assasuni Thana on the east and west Bengal of India on the west. The area is economically important and rich in biodiversity, because part of the world largest mangrove forest Sundarbon is in this area. Moreover, numerous activities such as fish cultivation in saline water Ghair (Local name), Agriculture and industry especially fish production and fish processing industry etc go on in the region.

2.2 SAMPLE COLLECTION AND PROCEDURE Groundwater samples were collected from 12 well locations in the Shyamnagar Thana during May 2011. These wells are used either for domestic and/or agricultural purposes. The wells were chosen to represent all the area on the basis of their suitable geographical location and different well depth. Samples were collected manually and stored in 500 ml clean plastic bottles with air-tight screw cork. Two bottles of groundwater samples of each station have been collected. One bottle of water sample for arsenic analysis in which HNO3 (.01 N) was used for maintains pH within the limit of 2 to 3 to control the changing characteristics of water and another bottle of water sample was freshly collected from tube well without any type of acid to detect other chemical parameters specially major cations and anions and few trace element. After collection of water samples that were brought to the research Laboratory immediately for hydrochemical analysis. Environmental impact in the area has assessed from the collection of direct field observation data and interview information from local peoples.

2.3 METHODS OF ANALYSIS Keeping consistency with objectives in the present research of arsenic and salinity determination are a normal phenomena. But the determination of other physical and chemical parameters of groundwater samples is also important to know the behavior of arsenic and salinity with them. The study is conducted to apply field observation data and chemical analysis data from laboratory. Salinity is usually reported as electrical conductance (EC) which is measured in each station of the field by using potable electro conductivity (EC) meter (HANNA HI 7039 P). Salinity was also measured in parts per thousands(‰) by using Eco Scan instrument from the Isotope Hydrology division, Atomic Energy Research Establishment, Savar Dhaka. TDS is another important parameter to measure salinity of water which is measured as a calculated value by using the Aqua Chem. (Version 3.70) software in the study. Arsenic concentration in groundwater have been measured with Atomic Absorption Spectrophotometer (Model: ZEEnit 700, Analytik Jena, Germany) by using standard methods form the Isotope Hydrology division, Atomic Energy Research Establishment, Savar Dhaka. Ca2+, Mg2+ and Fe also measured to apply same methods and instruments, but Na+ , K+ is measured by Flame Photometer (Model: PFP 7, ZENWAY, UK). The major anions (Cl- , NO3 - , SO4 2- , HCO3 - ) is measured with Ion Chromatography (Model: ICS -3000, DIONEX, USA) from the same laboratory. The pH is measured in each station by using potable HANNA Pocket pH meter during the water sample collection.

Source of Information: Rajshahi University journal of environmental science, Vol. 2, 12-22, December 2012

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

In this study groundwater quality especially salinity and arsenic contamination was evaluated using groundwater chemistry data. The chemical result denoted that groundwater is highly saline content and unusable for drinking and agricultural purposes. Salinity is closely related to the Na+, Cl-, EC, and TDS. High concentrations of these parameters are the simplest indicators for the salinization process and high salinity groundwater. Arsenic in groundwater varies from place to place between 0.009 mg/l and 0.078 mg/l with an average of 0.052 mg/l which is just above the Bangladesh standard limit (DoE, 1997), but its impact does not found remarkably in the area. It may be the additional burden in future for the living peoples. Due to high salinity there are number of flora such as, papaya, banana, guava, berry-berry, jackfruit, palm etc and fauna such as fox, mongoose, squirrel, snake, buffalos, goats, sheep and koi, shole fiches are on the way of extinction. Crop production is also decreasing rapidly in the study area. Water born diseases diarrhoea, dysentery, typhoid, jaundice patients were found significantly. So keeping in view the greater welfare of the people in the area should be taken proper steps in nationally to keep free from the harmful effect of arsenic and salinity effects. Locally instant peoples have to avoid such contaminated groundwater from the identified wells. Instead of it, harvesting rainwater, pond water with proper treatment may be used for drinking purposes in temporarily. For long term, responsible departments have to be proper planning to find out the saline and arsenic-free aquifer. In addition, proper management and maintenance of surface water may helpful to reduce the drinking water crisis.

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