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A Laboratory Approach for Determining Effects of Potential Oil Spillage on Water Quality of Sundarbans Mangrove Forest, Bangladesh

H. Ara
Chemistry Discipline, Khulna University, Khulna 9208

M. S. Rahaman
Chemistry Discipline, Khulna University, Khulna 9208

M. M. Islam
Department of Chemistry, Bangladesh University of Engineering and Technology, Dhaka

A. Mallick
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna 9208, Bangladesh

M. S. Hossain
Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna 9208, Bangladesh

Abstract/ Executive Summary:

This study was conducted in laboratory as a microcosm approach in order to know the effect of oil (diesel) spillage on water quality of Sundarbans Mangrove Forest (SMF), Bangladesh. A series of laboratory tanks were filled with water of SMF with different concentrations of oils dispersed onto the waters. The water quality parameters viz. alkalinity, free CO₂, dissolved oxygen, chemical oxygen demand, hardness, major anions (sulfate and chloride) and major cations (Na+, K+, Ca+2 and Mg+2) were determined three times at nearly weekly intervals. Results indicate the degradation of oil followed by reduction of dissolved oxygen and evolution of free CO₂, coupled with depletion of the concentration of Ca²+ and Mg²+ in tank waters. This might be due the complex formation of Ca²+ and Mg²+ with hydrocarbons which were insoluble in water. The water quality parameters of different laboratory tanks were also compared with those of different locations of SMF determined before the microcosm approach, suggesting that oil spillage deteriorates the water quality of SMF.

Keywords: Water quality, Simulation, Oil spillage, Sundarbans mangrove forest (SRF)

Location: Dangmari station of SMF located adjacent to the Mongla Port, Khulna

Start Date: 00-11-2004

End Date:

Program Area: Risk Management in Agriculture

Commodity: Contamination

Objectives:

Keeping the above mentioned information in mind, an oil dispersion experiment was conducted at Karamjal Wildlife Breeding Centre and Mangrove Park under Chandpai range in August 2001 (JOECLA 2002). As a consequence of oil spillage, we hypothesize that there is effect on the ions regulation between water-sediment interfaces that were not possible to study at field levels because of large sensitive aquatic ecosystem. To test this hypothesis, we conducted a simulated response for oil spillage into the laboratory as a microcosm approach.

Methodology:

Sampling and analytical techniques: Water samples were collected in November 2004 from Dangmari station of SMF located adjacent to the Mongla Port, Khulna. Salinity and pH of the water were measured in situ by Salinity Meter (AtagoRefractometer) and Hanna-pH Meter, respectively. Alkalinity, dissolved oxygen (DO), and free CO₂ were determined by titrimetric method (APHA 1992). Water samples were transported into the Water Chemistry Laboratory, Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna, and analyzed for different parameters. Water samples preserved with 1 mL HNO₃/L were analyzed for hardness and Ca^₂+ by EDTA titrimetric method from which Mg²+ was determined through calculation method (APHA 1992). While water samples preserved with 1 mL H₂SO₄/L were analyzed for chemical oxygen demand (COD) by open-reflux titrimetric method (APHA 1992). Na+ and K+ were determined by flame photometry with a Jenway PF7 flame photometer. Such anionic species as SO₄ 2- and Cl- were determined by gravimetric method with drying residue and argentometric method, respectively (APHA 1992). Laboratory simulations: Oil dispersion studies were conducted in four glass made tanks numbered A, B, C, and D each with a surface area of 3.5 sqft. Each tank was filled with 24L SMF water. Then 3mL, 9mL, 15mL, and 21mL oil (Diesel) were added to each of the four tanks. After spilling oil, pH, alkalinity, free CO₂, DO, hardness, Ca²+, Mg²+, Na+ , K+ , SO₄ 2- and Cl- of each tank were measured three times. The observed data were compared with those determined before spilling at nearly weekly intervals.

Source of Information: J. Life Earth Sci., Vols. 3-4: 23-28, 2009, ISSN 1990-4827

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Although Bangladesh has not yet experienced large-scale oil spill incidents, it is to be noted that the country has two international marine ports with potential oil spill risks. One of them is the Mongla Port, situated only 3 km north of the Sundarbans Reserved Forest (SRF) and is reached mainly by a 100 km long navigation channel through the Passur-Sibsa River system that runs through the SRF, implying that there is a possibility of deterioration of the aquatic environment due to oil spillage. It is apparent from this investigation that spillage might result in biodegradation of hydrocarbons and some forms of chemical reactions which in turn regulate the chemical composition of SMF. It is therefore necessary to monitor the changes in water quality status associated with oil spills. Moreover, to sustain the productivity of the natural environment, strategic plans need to be developed for the protection of the water environment from the harmful effects of any oil spills.

Knowledge Management: Journal