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Study on the Lead Pollution Caused by Automobile Exhaust in Sylhet City

SHAMSHAD B. QURAISHI
Chemistry Division, Atomic Energy Centre, P.O. 164. Ramna, Dhaka-1000

SHAHIDUL ISLAM AND
Department of Chemistry, Shahjalal University of Science and Technology, Sylhet

MUHAMMAD YOUNUS
Department of Chemistry, Shahjalal University of Science and Technology, Sylhet

Abstract/ Executive Summary:

Environmental pollution is a major concern nowadays in all over the world. As Bangladesh is a densely populated country, environmental pollution phenomena have a great impact here. The main sources of air pollution in Bangladesh are automobile engines including two-stock and four-stock engines (i.e. bus, truck, tempo, auto rickshaws, motor cycles etc.), uncontrolled industrialization, fertilizer industry, chemical plants, garments, brick-fields and other industries(1,2). It is notable that the concentration of Pb in the ambient air of Dhaka city has decreased by two-three times as a result of the introduction of unleaded gasoline by the Energy Ministry from July 1, 1999.(2) However, Pb is still being used in an uncontrolled manner in different industries. Sylhet city is an old and congested city and roads in the town are very narrow and highly traffic dense. Unfortunately, no study has been carried out yet on atmospheric pollution of Sylhet city. In the present study the Pb levels in the leaf and soil samples collected from six heavy traffic dense areas of Sylhet city are reported to get an overview of lead pollution phenomena and its relation to environment.

Keywords: Lead pollution, Caused by automobile exhaust, Sylhet city

Location: Sylhet city, Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Non-commodity: Pollution

Objectives:

In the present study the Pb levels in the leaf and soil samples collected from six heavy traffic dense areas of Sylhet city are reported to get an overview of lead pollution phenomena and its relation to environment.

Methodology:

Leaf and soil samples were collected from different locations of Sylhet city where traffic density is generally very high due to Tempo, Bus and Truck stands. The samples were collected from 1) West Kadamtoli Bus stand, 2) East Kadamtoli Bus stand, 3) Lauai Bus stand, 4) Bandarbazar Point Tempo stand, 5) East Bandarbazar Point Tempo stand, 6) Supanighat Truck stand, and 7) Ambarkhana point area of the Sylhet city in January. One soil and one leaf sample were also collected from the Borgul Village. Akhalia of the Sylhet city that was used to compare the pollution status.

Collection and Preservation of Leaf sample: Vegetation and soils are important sinks for atmospheric pollutants. Indeed, the vegetative components are useful bio-monitor of atmospheric pollutant deposition. Therefore, leaves from different Tempo and Bus Stands trees were collected from the tree and cut into small pieces according to published procedure (3.4) and mixed up very well and a portion of them was selected as sample. For each location only one kind of tree was selected. The selected trees were Jackfruit, Rain tree, Teak, Mango, and Banyan tree. The leaf samples were dried in oven at 105°C and then ground to powder with aluminum carbide mortar and were preserved in previously cleaned polythene bags. Soil sample: The collected soil samples were oven dried at 105°C until constant weight was obtained. The soil samples were homogenized using an agate mortar and passed through 1 mm sieves. The dried samples were preserved in previously cleaned polythene bags.

Leaf sample digestion process : The leaf sample (1g) was ashed by heating in a muffle furnace at 450°C for 6 hours in a 25ml pyrex beaker. To the ash 4ml of analytical grade nitric acid was added (one ml at a time) and digested to nearly dryness for at least 5 hours on water bath. Further one ml of aqua regia (3:1 of HCI and HNO3) was added and continued digestion and evaporated to dryness5 . Finally, 2-3 drops of concentrated nitric acid was added and then warmed with 5ml of de-ionized water. The solution was filtered with Whatman-41 filter paper, diluted to 10ml in 10ml volumetric flask using de-ionized water.

Soil sample digestion process: To 0.5g of finely ground soil sample 3ml of aqua regia was added and the sample was kept overnight. The mixture was digested on a water bath and 7ml of aqua regia was gradually added (one ml at time) and the sample was digested for 7 hours at 90°C and the solution was evaporated nearly to dryness. Ten ml of 0.1M Na-EDTA solution was added and adjusted the pH at 5 to 6 by using hydrochloric acid or sodium hydroxide solution. The solution was allowed to stand for two hours and then filtered through Whatman-41 filter paper. The filtrate was evaporated to some extent so as to make a 10 ml solution with distilled deionised water. Samples ware then analyzed for metals by FAAS. In every case a duplicate and a parallel blank experiment were carried out for the accurate determination of lead. The quantitation limit for the Pb was calculated as 2.1 ppm in leaf and 4.0 ppm in soil, respectively.

Source of Information: Journal of Bangladesh Academy of Sciences, Vol. 32, No. 2, 117-120, 2008

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The lead levels obtained from the study (5.72-121ppm) were considerably lower compared to reported lead concentrations in Dhaka(7) (leaves 8.432 ppm), Benin3 (vegetable 243 ppm) and Bagdad(8) (palm leaves 28-1000 ppm). It can be said that the air of Sylhet city is not much lead polluted and not an immediate threat to the environment but getting polluted in some areas of the city.

Knowledge Management: Journal