Status of Ambient Air Quality in the Urban and Rural Areas of Chittagong, Bangladesh

Key words: Status, Ambient air, major zones, prescribed limit, Chittagong region.

Introduction

The relationship between environment and the development is one of the most important issues of the present time. Developmental activities e.g., industrial, agricultural, transportation, constructional work, etc. cause degradation and drastic changes in every component of environment namely, hydrosphere (water), lithosphere (soil) and atmosphere (air) and even biosphere through pollution. Population explosion along with urbanization and industrialization greatly increased the intensity of pollution.

In order to recognize and predict hazardous effects of pollutants, the scientific monitoring of these environmental components is essential. For this purpose, the quantitative characterization of air, water and soil is the prerequisite. It gives us an idea about the seriousness of pollution problem in these three environmental components. This would also help in focusing on the extent to which pollution control is required and generate real concern among policy planners (Pandey, 1999).

The atmosphere is used as a natural sink for gaseous pollutants. The contamination of this atmosphere is so severe that is was recognized as the top most issue among the ten major environmental issues identified by the latest UNEP report (Kumar, 1999).

Sources of air pollution can be categorized as natural sources (volcanic eruption, forest fire, tornado, living plants, sea salts, natural radio-activity, ozone and natural hazes) and anthropogenic or man made sources (the thermo-power plant, the nuclear power plant, industry, refrigerator, sewage treatment plant, household combustion, and all sort of transportation means) (Kumar, 1999). Air pollution is termed as „the price of Industrialization”.

Growing cities, increasing traffic, rapid economic development and higher levels of energy consumption lead to the pollution of air. Air pollution caused by automobiles has been described as the „disease of wealth”. Around the world, five major types of materials are released directly into the atmosphere in their unmodified forms and in sufficient quantities to pose a health risk. They are carbon monoxide, hydro-carbons, particulates, sulfur dioxide and nitrogen compounds. This group of pollutants is known as primary air pollutants. These materials may interact with one another in the presence of an energy source to form new secondary air pollutants such as Ozone and other very reactive materials. Secondary air pollutants also form from reactions with natural chemicals in the atmosphere (Miller, 2002).

Air pollution may cause different disease to man, animal and plant, contribute to the general deterioration of both our cities and country-side, damage to materials, cause intangible losses to historical monuments and thus bring about vast economic losses. It also has a direct or indirect effect on climate. Significant and sometimes devastating effects of air pollutants have been recognized on plants. Thick smog has killed more than a million trees in southern California. The visible injury symptoms on plants and leaves are tissue collapse and necrotic patterns, chlorosis, color patterns and growth alterations (Chhatwal, 1997).

In our country the growth of both industrial and residential areas is unplanned, unstructured and unzoned. This leads to housing being built alongside factories and industries, increasing the risk of industrial accidents. Rapid and unplanned development often results in growing levels of air pollution, more pollution-related health problems, lost working days and economic dysfunction. Bangladesh through industrial process has already emitted a total of 23359 thousand metric tons of CO₂ (WRI, 2002). Again use of motor vehicles is growing rapidly which mostly leads to city pollution. Chittagong, the commercial capital of Bangladesh is a major area of environmental concern because of heavy industrial pollution, oil spills and pollution from reconditioned and old vehicles. All these leads to different severe pollution related problem in this region but sufficient steps were not been taken to control and reduce them (Gain, 2002).

Atmospheric pollution in urban and rural area generally thought to be of different level and condition. No study so far carried out solely on the assessment of ambient air quality status in the rural and urban areas of Chittagong region. Considering the fact the present study was conducted with a view to monitor the air quality, to identify the seasonal variation of ambient air quality and finally to evaluate the status of overall air pollutions situation in urban and rural areas of Chittagong region for dry season.

Materials and Methods

Being a port city of the country, Chittagong attracts lots of people from other places of the country in search of business, job and other commercial activities and thus it has become one of the busiest city of the country with a total population of 2348428 (GOB, 1998) and with a large no. of vehicles to support the movement of this huge number of city dwellers.

The present work was carried out in Chittagong City (as urban site) and Hathazari Upazila (as rural site) over a period of 6 months from August 2004 to March 2004. For air pollution status Chittagong City and Hathazari Upazila were selected purposively as air pollution of Chittagong City represent an ideal feature of air quality status in Chittagong region and Hathazari Upazila, an ideal feature of the rural area as it is still far away from vast industrial and commercial development compare to the urban area and moreover these areas are situated in the distances convenience and permissible for carrying the High Volume Sampler from DOE, Chittagong.

Chittagong is situated on the Right Bank of the river Karnafuli and lies within 22°-14´N to 22°-24´-30´´N Latitude and between 91°-46´E to 91°-53´E Longitude (Banglapedia, 2004). Hathazari upazila is situated on the middle portion of Chittagong district. The upazilla is with an area of 251.28 sq km and is bounded Fatikchhari upazila to the north, Panchlaish and Pahartoli thanas to the south, Raozan upazila to the east, Sitakunda upazila on the west. The upazila lies between 22°22´ N to 22°38´N Latitudes and 91°41´E to 91°53´E Longitude (SRDI, 1991).

For the collection of sampling data the urban area is divided into 3 different zones viz, Industrial, Commercial, Residential and from each zone 3 different locations (Nasirabad, Sagarica and Kalughat under the Industrial zone, Agrabad, Khatungang and New Market under Commercial zone, Khulsi, Chandgao and Agrabad Residential area under Residential zone) were selected purposively to get representative air quality samples in terms of three non-carbonic pollutants (Suspended Particulate Matter, Oxides of Sulphur, specially SO₂ and Oxides of Nitrogen, specially NO₂). The rural area was divided into 4 different locations viz, Brick field, IFESCU campus, Homestead area and Village road purposively to represent the whole area. The study was conducted with direct support from the Department of Environment, Chittagong, using their assistance and lab facilities as required. In selecting the locations, initially opinion from the concerned authorities of the DOE were taken and then physical verification were made to overview the air status by examining associated phenomenon viz. intensity of the traffic congestion, smoke, fog, dust, fumes etc.

The instrument used to assess the ambient air quality and pollution is named as High Volume Sampler (HVS) 415. It is in widespread use all over the world to measure air pollution. In this sampler, air born particulates were measured by passing air at aha high flow-rate of 1 to 1.3 cubic meters per minute through a high efficiency filter paper which retain the particles. The instrument measures the volume of air sampled, while the amount of particulates collected was determined by measuring the change in weight of the filter paper. HVS were also fitted with absorbers which sample gaseous pollutants. Here the air was passed through chemical that absorb specific gases, and the atmospheric concentration of gaseous pollutants were determined by chemical analysis of the absorbing solutions.

The collected data were then compared with respect to the Ambient Air Quality Standard (prescribed limit) set by the Department of Environment (DOE) in 1995 (Table 1) to determine the level of pollution. Later significance of variations among the concentration of parameter and among the major zones was tested on monthly basis.

1. Air quality status in urban area

The ambient air quality state in the urban area in dry season (Table 2) depicts that the monthly average concentration of all three parameter was highest for commercial zone (SPM- 492.06µg/m³, SOx-171.85µg/m³, NOx- 185.81µg/m³) and the lowest value for the residential zone (SPM- 283.69µg/m³, SOx-38.61µg/m³, NOx- 45.08µg/m³). This may because of frequent and intense movement of all types of vehicles in this zone specially the truck, wagon, bus, taxi, car etc., heavy traffic jam and presence of a no. of car servicing center, parking center and also the existence of a huge no. of slum. In industrial location the resultant lower value than the commercial zone (SPM- 487.20µg/m³, SOx-93.37µg/m³, NOx- 97.57µg/m³) may because of lack of continuation of industrial activity, even laying off of some industries from the industrial location such as from Kalurghat and moreover having support from the adjacent good green coverage of the city hillside. Comparatively less movement of traffic in the Residential zone than the other zone may be the main reason for the lowest concentration of all the parameter here.

Moreover it was found that the concentration of all three parameter was much higher in Dhaka city (Alam et al, 2000) in comparison with Chittagong city. Thus it is usually agreed that ambient air pollution of Chittagong city is still less severe than Dhaka city.

2. Air quality status in rural area

Pollutant level in the four sites of the rural area varies in structure, social and atmospheric environment. A selection of four rural sites was made from the Hathazari thana to represent the rural area of the Chittagong region. Monthly variation along with the significance among the pollutant concentrations for each of the sites was assessed to evaluate the nature of pollution. Variation among the sites for a particular pollutant was also determined. The result obtained from the collected data on three non-carbonic pollutants during the period October” 2004 to March” 2005 are given and described in the following.

Table 3 describes that the maximum concentration of SPM was found for the Brick field site. This may because of the use of huge amount of fuel wood instead of coal, the use of smaller sized chimney (15 ft) instead of 100 ft high chimney as standard set by the law and not using filter and scrubber attached to the chimney. On the other hand concentration of SOx and NOx was maximum in the Village road. This may mainly by the fact that the vehicle that is declared unsuitable to move in the metropolitan area (urban area) have been shifted to rural area to perform further activities. Thus this backdated unfit vehicles seriously deteriorating the air of the village area by emitting unburned petrol. The minimum value for all the parameter was found in the homestead. The result may because of the cleansing activity of the homestead vegetation, Halda river beside and also the absence of polluting source like industry, heavy traffic pollution. This result clearly confirms that the homestead area still safe and sound compare to other locations.

2.1 Variation for SPM

Figure 1 (a) depicted that in rural area the monthly level for SPM of brick field site is quite higher than the other there. Even the monthly highest value for the rural area recorded here in the brick field (716.20µg/m³ in January) was the highest among all the monthly value recorded both in the urban and rural area.

(a) Monthly variation of SPM

(b) Monthly variation of SOx

(c) Monthly variation of NOx

Figure 1. Monthly variations on concentrations of (a) SPM, (b) SOx and (c) NOx in four different sites of the rural area.

The figure also depicts that in the month of January the level of SPM for brick field and IFESCU campus rose up suddenly. This may because of full starting of the brick field activity. In the homestead the parameter level is conspicuously the lowest among all the locations.

2.2 Variation for SOx

The monthly level of SOx in the village road occupied the highest level in comparison with the other locations. The cause of which has been descried earlier. Moreover the pollution from the market places likes from hotel and tea stalls also contribute in this respect. Brick field occupied the second largest level which is followed by the level in IFESCU campus. In homestead the level of the parameter is far below from the other site of the rural location.The absence of highly polluting substances and the cleansing effect of homestead vegetation play a great role in abating the air pollution.

2.3 Variation for NOx

The village road occupied the highest monthly level of NOx in comparison with the other locations. The reason of such fact may be as for the case of the variation for SOx. IFESCU campus, village road and homestead occupied the successive level of SOx in the rural area. 

3. Comparative Study of the Two Major Area

As the data was available for collection from the rural area only for the dry season (October” 2004 to March” 2005) the comparison was made between urban and rural area only for the dry season. In representing the monthly average of urban area the average of all the sites under three major locations (i.e. the average value of 27 sites) was considered and for rural area the average of the four sites was taken into consideration. The significance among the parameter and the area was assessed to determine the alarming pollutant state and to take necessary actions thereby.

(a) Average Monthly variation of SPM

(b) Average Monthly variation of SOx

(c) Average Monthly variation of NOx

Figure 2. Average Monthly variations on Concentrations of SPM, SOx and NOx between urban and rural area.

3.1 Variation for SPM

Figure 3. Total Average variations on Concentrations of SPM, SOx and NOx
between urban and rural area

The monthly average value for the SPM level was high in the urban area all the season (dry) round except in the month of January (figure-2a). In the month of December, February and March the level of the both the areas were more or less equivalent. This may mainly because of the starting of heavy emission from the brick field, their use of logs, smaller sized chimney and also the hill burning. After all the total average value for the concentration of SPM was higher in the urban area (420.98µg/m³) than in rural area (382.85µg/m³) (figure-3). The difference seems to be smaller may because of that the selected rural area is in the adjacent position of the Chittagong City Corporation area.

3.2 Variation for SOx

The monthly average value for the SOx level was much higher in the urban area all the season (dry) round (figure-2b). As a consequent the total average value was also higher. This may mainly because of heavy pollution in the urban area from the emission of the heavy traffic, traffic jam, industrial pollution etc.

3.3 Variation for NOx

The monthly average value for the SOx level was also much higher in the urban area all the season (dry) round (figure-2c). Consequently the total average value was also higher. This may mainly because of heavy pollution in the urban area from the emission of the heavy traffic, traffic jam, industrial pollution etc. like as in case of variation of SOx.

3.4 Significance of variation

General Linear Models Procedure of the SAS system analysis showed that the variation among the concentration of parameter between the area was found significant at 5% level of significance except SPM for rural area (Table 4).

Conclusion

The quality of ambient air within the Chittagong City has been deteriorated mainly due to uncontrolled emission of pollutants by motorized traffic. This is conspicuous from the study that the monthly average concentration of all the three parameter (SPM., SOx, NOx) in the Commercial location was far above the prescribed limit stated by the DOE. One astonishing fact is that the levels of all the parameters in the industrial area were found below the prescribed limit. This may because of the abating quality of vegetation in and near the industrial location and may be the effect of sea air from the coast. Except the level of SPM the level of other two pollutants was found below the prescribed in the residential area. Actually the emissions caused by the adjacent location do not remain static rather it mixes in the total mass of air and dispersed by the event of wind flow and other natural phenomena.

The deterioration of air quality in the rural area of Hathazari thana is also alarming mainly due to the emissions from the enormous brick – kilns available in the vicinity of the hill. Hill cutting soil is the main source of soil in these brick - field. As a result in the dry season the air quality in this area deteriorated severely. Moreover the brick field authority does not use coal and standard sized chimney. Thus the households in the vicinity of the brick – field suffers a lot in this season. However the ambient air pollution in the rural area is still less severe than the urban area.

The management of air quality of Chittagong region both in the urban and rural areas requires an active survey, monitoring and surveillance program supported by rational effluent and emission quality standards and legislation to enforce remedial action. The quality of air is of utmost concern. Lack of skill manpower and sophisticated instruments are the main obstructing factor for the DOE, Chittagong. Considering the above fact a continuous monitoring scheme is essential to evaluate air quality and for the development of any plan for mitigating of health risks caused by polluted air. This study promotes a green agenda for the citizen of Chittagong region and identified that an integrated approach is required to improve environmental quality of Chittagong. Further work is required to implement more stringent emission standards. Added research in setting up pollution management and control criteria are also warranted. These efforts will benefit the well being of humans, the environment and our natural resources.

Acknowledgements

We would like to thank Mr. Mustafuzur Rahman and Mr. Asadul Haque who are working as the chemist in the laboratory of Department of Environment, Chittagong, Bangladesh.

Reference

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