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Study of No2 Concentration Level in Air of Selected Location of Sylhet City

M. A. I. Chowdhury
Department of Civil and Environmental Engineering, Shahjalal University of Science and Technology, Sylhet

B. K. Bani
Department of Civil and Environmental Engineering, Shahjalal University of Science and Technology, Sylhet

R. Alam
Department of Civil and Environmental Engineering, Shahjalal University of Science and Technology, Sylhet

M. J. Hossain
Department of Civil and Environmental Engineering, Shahjalal University of Science and Technology, Sylhet

M. B. Haque
Department of Civil and Environmental Engineering, Shahjalal University of Science and Technology, Sylhet

Abstract/ Executive Summary:

Sylhet City is one of the largest metropolitan city at the north east portion of Bangladesh with total gross area of 26.5 km² and a population load of 0.7million, estimated in 2001. Due to migration from other towns and rural areas, City population is increasing rapidly with resulting increase of vehicular load. Due to the rapid urbanization, city environment specially air quality is degrading for vehicular emission. This study evaluates the NO₂ concentration by chemical method specifically colorimetric method at 7 different locations of Sylhet city during morning and evening time through dry season and monsoon. The major findings are maximum concentration of NO₂ at dry season morning was 0.699μg/m³ at Ambar khana point and minimum concentration was found 0.258 μg / m³ at Modina market point. Maximum concentration of NO2 in dry season evening was 1.161 μg / m³ at Bonder point and minimum at Subhani ghat point was 0.7 μg / m³. Maximum concentration of NO₂ monsoon morning was 0.316 μg / m³ at Tilaghor point and minimum at Modina market point was 0.145 μg / m3. Maximum concentration of NO2 in monsoon evening was 0.814 μg / m³ at Ambarkhana point and minimum at Modina market point was 0.391 μg / m3. Maximum seasonal variation occurred at Bonder point was 61.29% and minimum variation occurred at Subhani ghat point was 35.69%. The concentration of NO₂ measured all several location were below the permissible limit ( below 100 μg / m³ ) based on DOE standard.

Keywords: NO2, Concentration , Atmosphere, Sylhet.

Location: Sylhet City

Start Date: 00-01-2007

End Date: 00-12-2007

Program Area: Risk Management in Agriculture

Non-commodity: Adoption of technology

Objectives:

1. To study of NO₂ Concentration Level in Air of Selected Location of Sylhet City

Methodology:

Sampling location were selected depending on daily traffic volume, traffic congestion, commercial activities around the site, availability of power supply, shelter from rain, perhaps a constant temperature environment and easy access for monitoring personnel. Residential sites were not specifically separated as most of the residential areas were combined with commercial areas due to unplanned urbanization of Sylhet City and most of these areas are near the highway or city road with heavy traffic. However there are some specific residential area growing recently. In the sampling site the sampling points were selected considering the basic requirement of air sampling that will give a representative sample for that location. To obtain a better representative sample the sampling were done at different side of the different road in a road intersection.Seven locations Tilaghar, Bandar court point, Naiorpol, Chauhatta, Subhani ghat, Ambar khana, Modina market, were selected for the study of NO₂ of Sylhet city . In order to determine NO₂ air were sucked from the atmosphere by a rotary compressor and passed through the midget impinger where the specific absorbing chemicals absorb the NO₂ and the absorbance of NO₂ pollutants were determined by UV Spectrophotometer. Finally using the calibration curve corresponding concentration was estimated. Then considering the total amount of air sampled at standard pressure and temperature concentration of NO₂pollutants were measured in μg/m3 of air sampled. The procedure followed in the experiment required different instrument like midget impinger, Rotary Compressor, Electronic balance and spectrophotometer. The samples were collected at the average nose level i.e. 4 to 5 ft height from the ground level specified by the air sampling standard requirement. Because NO₂ pollution at this height is most severe to human health as human breathes the polluted air at this height. The samples for the analysis NO₂ pollutants were collected 2 times for each day (9:30 A.M and 5: 30 P.M) and finally all the concentration for each specified sampling point’s concentrations were making an average. Sample were also collected from the exhaust point of different types of vehicle. Emission of NO₂ from different vehicle is determined. Five samples were taken for each vehicle and it is found that the NO₂ emission from different sample were not uniform. For different six types vehicles NO₂ were measured and it was found that the highest average concentration was measured from trucks is 84.04 μg / m³and the lowest average concentration measured from motor cycles is 1.806 μg / m3. Figure 3 shows the average different concentration for different vehicles. Average concentration of NO₂in dry season at 7 different locations were measured two times in each day. The difference between morning and evening concentration in percentage and was measured that the highest variation of concentration were at Modina market is 72.168% and the lowest variation were at Ambar khana point is 38.141%. In the same way in monsoon average concentration of NO₂ were measured.

Source of Information: J. Environ. Sci. & Natural Resources, 3(2): 151-154, 2010; ISSN 1999-7361

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The major findings are maximum concentration of NO₂ at dry season morning was 0.699μg/m³ at Ambar khana point and minimum concentration was found 0.258 μg / m³ at Modina market point. Maximum concentration of NO2 in dry season evening was 1.161 μg / m³ at Bonder point and minimum at Subhani ghat point was 0.7 μg / m³. Maximum concentration of NO₂ monsoon morning was 0.316 μg / m³ at Tilaghor point and minimum at Modina market point was 0.145 μg / m3. Maximum concentration of NO2 in monsoon evening was 0.814 μg / m³ at Ambarkhana point and minimum at Modina market point was 0.391 μg / m3. Maximum seasonal variation occurred at Bonder point was 61.29% and minimum variation occurred at Subhani ghat point was 35.69%. The concentration of NO₂ measured all several location were below the permissible limit ( below 100 μg / m³ ) based on DOE standard.

Knowledge Management: Journal