For Presentation at the Air & Waste Management Association's 90th Annual Meeting & Exhibition, June 8-13, 1997, Toronto, Ontario, Canada

A-WA92.01

Current State of Traffic Pollution in Bangladesh and Metropolitan Dhaka

Md. Masud Karim

Consulting Engineer, Dainichi Consultant Inc., 3-1-21 Yabuta Minami, Gifu 500, Japan.

Hiroshi Matsui

Professor, Department of Civil Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466, Japan.

Takashi Ohno

Nagoya City Environmental Science Research Institute, 16-8 Toyoda 5 Chome, Minami-ku, Nagoya 457, Japan.

Md. Shamsul Hoque

Associate Professor, Department of Civil Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh.

Abstract

Limited resources, invested for the development of transport facilities, such as infrastructure and vehicles, coupled with the rapid rise in transport demand, existence of a huge number of non-motorized vehicles on roads, lack of application of adequate and proper traffic management schemes are producing severe transport problems in almost all the urban areas of Bangladesh. Worsening situation of traffic congestion in the streets and sufferings of the inhabitants from vehicle emissions demand extensive research in this field. However, no detailed study concerning traffic congestion and pollution problems for urban areas of Bangladesh has yet been done. Therefore, it has become increasingly important to examine the present state of the problem.

This research is a preliminary evaluation of the current situation of traffic pollution problem in Bangladesh. The daily total emissions of NOx, HC, CO, PM, and SOx are estimated using the daily fuel consumption and total traffic flows in Dhaka city. Estimated daily emissions are 42, 39, 314, 14, and 42 t/d for NOx, HC, CO, PM, and SOx, respectively. The emissions estimated using two different methods revealed good correlation. Daily average concentration of NOx (NO2, NO) were measured at 28 street locations in Dhaka city during November, 1996. The results showed extremely high concentrations of NO2 and NO in these locations.

Introduction

Motor vehicles contribute significantly to emission inventories in certain regions specially on urban areas. The pollutant species most often of concern with respect to transportation facilities are carbon monoxide (CO), hydrocarbons (HC), photochemical oxidants e.g., ozone (O3), nitrogen oxides (NOx), particulate matter (PM), and lead (Pb). In spite of great improvements in most developed countries due to reduced use of leaded fuels, highway emissions of lead remain a persistent air quality problem. Recent studies indicate that motor vehicles are also a major or primary source of other toxic air pollutants including 1.3-butadiene, benzene and a number of carcinogens, associated with particulate matter. As the vehicle fleet continues to grow, motor vehicle emissions and the products of their transformation in the atmosphere are becoming increasingly important contributors to nearly every major air pollution problem facing the world today. In urban areas, where more than 70% of the population live, levels of motor-vehicle related pollutants frequently exceed internationally agreed air quality guidelines. Recent study found that pollutants concentration in micro-environments (vehicle inside, footpath, corridors etc.) are very much different from that in local monitoring stations. (1)

In developed countries, governments have fought for clean air by regulating all major and many minor sources of air pollution. Industrial emissions have been significantly reduced. As a result of new motor vehicle emission standards introduced in 1988, new vehicles in developed nations are 90% cleaner than those manufactured in the 1970s. However, despite those substantial efforts, we continue to be plagued with air pollution problems. A major issue is our continued and growing reliance on the private car. Growth in both the number of operating vehicles and in the usage of these vehicles, is a detriment to the technical progress being made as cleaner new cars replace older, high polluting vehicles.

For developing nations, however, pollution severity occur due to the high content of lead in gasoline, big number of high polluting vehicles, impure fuel, inefficient landuse, and overall poor traffic management. Even though the pollutants regulated by developed and developing nations should differ, it is possible to make gross generalizations. The pollutants of concern for developed countries would be volatile organic compounds, nitrogen oxides, and carbon monoxide; whereas leaded fuel, particulate matter, dust and sulfur dioxide would be targeted by developing nations.

Automotive lead emissions have declined sharply in most (Organization for Economic Development and Cooperation) OECD countries whereas in developing countries they are rising. The contribution of developing countries to lead emission already exceeds that of OECD countries and measures are urgently needed to reduce or eliminate lead in the gasoline marketed in developing countries. (2) Dhaka, Bangladesh has the highest lead pollution in the world for a part of the year, 1996, scientists at the Bangladesh Atomic Energy Commission (BAEC) observed (http://www.bangla.net/). A 17-month survey study by BAEC scientists detected 463 nanogram of lead in air over Dhaka, Bangladesh during the dry months (Novemberí95-Januaryí96). In Bangladesh, all vehicles use leaded fuel because the country's only refinery is not able to produce lead-free fuel.

In the former USSR, the relatively higher share of CO emissions from the transport sector is attributable to the large proportion of gasoline-powered trucks and buses with very high emission rates. (3) The higher share of SOx emissions from automobiles, in developing countries is due to the poor fuel quality and the extensive use of diesel-powered in some cases impure diesel vehicles. The share of motor vehicles in domestic emissions of fossil-fuel CO2 would be higher in Nigeria but lower in Bangladesh as a function of the percentage of petroleum fuel used in transport - 59% in the United States, versus 74% in Nigeria, and 28% in Bangladesh. (4) A study on emission source inventory performed in winter 1995 at Dhaka and found estimated total emissions for SO2 and NO2 to values 70 and 72 ton/day, respectively. (5)

This paper attempts to assess the total emissions from different energy consumption sectors and their factors to transportation energy use in Bangladesh. Total daily traffic emissions of NOx, HC, CO, PM, and SOx in Dhaka Metropolitan, estimated using two different methods: from daily fuel consumption and from traffic flow. Spatial distribution of NOx (NO, NO2) concentration done using the data collected from 28 street locations in Dhaka city during November of 1996. Daily average concentration of NOx calculated using a Box model for 7 road links in Dhaka and then compared them with the experimental results.

Methodology

The methodology would essentially involve extensive analysis of energy use, fuel consumption by type, traffic flows, daily average trips of transport modes, emission factors, meteorological parameters, and road geometry. These data are collected from different relevant departments, field survey, laboratory assessments, and experimental investigations. The following basic factors are incorporated into the technical specification of this work:

Air Pollution in Bangladesh

Bangladesh is a country located in between 20034' and 26038' north latitude and between 88001' and 92041' east longitude with an area of 148393 km2. The total population is approximately 130 million and a vehicle population of approximately 344500. The average winter temperature in November to February maximum 29 degree Celsius and minimum 9 degree Celsius and average summer maximum temperature in April 29 degree Celsius and minimum of 21 degree Celsius. Highest humidity in July 99% and lowest 36% in December.

Emission inventories of NOx and SOx have usually been made on national basis mainly for general administrative purposes and public information, systematic data published for the use of the scientific data is rather scarce. Nationwide SOx and NOx were calculated based on sulfur content and statistics of fuel consumption estimates of emission factors specific to individual source categories over time. Developing countries like Bangladesh is characterized by a rapid increase of energy consumption accompanied by a rapid growth of population and economic activities. Thus the increasing contribution of atmospheric loads of SO2 and NOx to global climate change is anticipated and it is really necessary to quantify these emissions in a hurried manner. Kato and Akimoto (7) suggested some relationships to estimate SO2 and NOx emission given in Equations 1 and 2. The fraction of 2 appearing in Equation 1 is for converting the weight of sulfur to that of SO2.

Six sectors, domestic, industrial, commercial, transport, other energy use, and non-energy use are accounted for in the calculation. The fuel types included as energy inputs in the calculation are coals and diesel. Table 1 presents final consumption of commercial energy in different sectors from 1981 to 1991 in Bangladesh.

Air Pollution in Dhaka

Dhaka, is the capital city of Bangladesh, has grown into a busy city of about 10.5 million people with an area of 815 km2. Dhaka city has heterogeneous traffic flows, as of 1996 an estimated total of 168,718 automobiles are on road. A substantial part of total traffic is non-motorized vehicles enhance severe congestion and pollution problem specially in road intersections. Table 2 presents total daily trips by different traffic modes in metropolitan Dhaka. Around 80% of total trips in Dhaka city is comprised of non-motorized transport (NMT) and only 5.9% trips are made by motorized transport (MT). Average trip length of MT is 27 minutes. Trips made by public transport specially buses are very low, only 0.9%. The maximum trips of vehicle modes are made by using rickshaw ( a special type of tri-cycle peddled by human) is 43%. Though it is very difficult to quantify pollution contribution from such heterogeneous traffic combinations, the influence of non-motorized transport on pollution are averaged upon the pollution considering the average speed of traffic flows. Based on data from different sources and road surveys conducted by the authors the traffic pollution contribution in greater Dhaka has been assessed and presented in the following sections. Equation 3 is used to estimate daily total emissions for traffic flows in metropolitan Dhaka.

Sampling Methods to Measure Concentration

Simultaneous measurement of NO and NO2 is done using Ogawa Sampler. Ogawa passive sampler consists of the following:

1. Teflon Disk

2. Teflon Ring

3. Stainless Screen

4. Triethanolamine (TEA) Coated Collection Filter

5. Stainless Screen

6. Diffuser End Cap

After assembling like in Figure 1, the loaded sample is placed in the airtight vial.

Analytical Operation

Samples

Loaded 31 samples (28 for sampling and 3 unexposed blank samples) have placed into the orange airtight vials and then taken to the exposure sites, after exposed to the test environment for 24 hours the samples are then placed into the vials, sealed, and then taken to the laboratory of the Nagoya City Environmental Science Research Institute for analysis. It is not out of the subject to mention here that there are not enough laboratory facilities in Bangladesh to perform the analysis. In the laboratory in Nagoya, cellulose fiber filter are put into two 20 ml glass vials for NO2 and NOx, containing 8 ml water each. Vials are then stoppered shake occasionally for 30 minutes, cooled for another 30 minutes period at a temperature of 2-6 degree Celsius, then 2 ml color producing reagent are added. After adding the color producing reagent, vials are shaken quickly and continue to keep cool for additional 30 minutes. Vials are then allowed to equilibrate at room temperature, for about 20 minutes, and the amount of colored derivative is determined with spectrophotometer at a wavelength of 545 nm. Unexposed elements are put through the same procedure to obtain a blank value determination.

Standard Solutions

8 ml of nitrite working standard solutions each (containing 0-1.0 µg nitrite/ml) are mixed with 2 ml of color producing reagent to prepare a standard curve, known as the calibration curve. The sampling procedure performed in November 1996. The calibration curve is presented in Figure 2.

Calculation of Concentration

Ogawa Sampler

When the exposed NOx element is placed in a glass vial with 8 ml of water, nitrite ion is produced. When 2 ml of the color producing reagent is added, the reaction is allowed to take place at 2-6 degree Celsius, the amount of colored derivative produced is proportional to the amount of original nitrite. Equations 4 and 5 are used to estimate NO and NO2 concentration.

Fixed-Box Model

Box models assume uniform dispersion throughout a single road link. Considering the road links as rectangular, with dimensions W and L and with one side parallel to the wind direction. Only 7 road links geometry are available. Atmospheric turbulence produces complete and total mixing of pollutants up to the mixing height H. The wind blows in the longitudinal direction of road with velocity u. The velocity is constant and is independent of time, location, or elevation above the ground. The concentration of pollutant in the air entering in any road links is constant and is equal to bct-1 (background concentration). Assuming the general balance condition that flow rates in and flow rates out are the same for any road link box. Equation 6 is derived to present the concentration of any pollutants in ppm.

Results and Discussions

Trends in National Emissions

The primary objective of this section is to provide current estimates of nationwide emission for two major transportation pollutants: SOx and NOx. Estimates are presented for 1981 to 1991 to give trends for national air pollutant emissions. Figure 3 is the relationship between fuel consumption in transport and all other sectors in Bangladesh from 1981 to 1991. An average of about 15% energy consumed in transport sector. A maximum of 18% transport energy consumption occur in 1990. Figures 4 and 5 present the relationship between NOx/SOx emission from all energy sources to transport sector in different years. An average of 34% NOx emission exhausted from transportation system to total emissions. On the other hand, the contribution from transportation SOx emission averaged 47%. Such high share of SOx emissions from automobiles is due to the high content of sulfur in petroleum products and extensive use of diesel fuel. The principal objective of compiling these data is to identify probable overall changes in emissions on a national scale. It should be recognized that these estimated national trends in emissions are not meant to be representative of local trends in emission or air quality.

Emissions in Dhaka Metropolitan

The average daily traffic emissions of NOx, HC, CO, PM, and SOx are presented for Dhaka city. They are estimated based on the emission factors and total daily fuel consumption from 1981 to 1996. Data for fuel consumption available till 1992, on the other hand total daily trips are available till 1996, an average growth rate equals to that of daily trips are taken to estimate current trends in fuel consumption. The average daily trips of all modes of transport, average trip duration, mean running speed, and emission factors of kilometerage travel are also accounted for in estimating daily emission. Emission factors for kilometerage travel are always considered for 5 to 6 years old model vehicles. Because most of the vehicles imported in Bangladesh are reconditioned automobiles. Bangladesh only allow to import maximum 5 years old vehicles. As for example, in estimating emission in 1988, we used emission factors for 1981 vehicles. The estimated daily emissions of NOx, HC, CO, PM, and SOx are presented in Figures 6, 7, 8, 9, and 10 for the period of 1981 to 1996. There is a fall in trends of fuel consumption in 1989, as a result sharp fall in emissions observed. In 1987 and 1988 there are severe floods affected about two-thirds of the total area inflicting severe damages. Capital stock losses were well over US $100 billion which seriously affected the national growth as well as the economy.

Emissions of nitrogen oxides are produced largely by transportation sources. Emissions of NOx have steadily increased over the period from 1989 to 1996 as the result of increased fuel combustion. From 1981 to 1988, the size of the change in emissions fluctuated. Transportation sources are the largest emitters of carbon monoxide. Major increase in emissions occur in pre-1989 period was in 1986, about 91 thousand tons of CO emitted from transportation systems as the result of increased motor vehicle travel.

Ambient NO2 Concentration in Dhaka

Interest in ambient NOx concentration has increased over recent year, both because of concern over the health effects of this pollutant and because of its important role in the formation of photochemical oxidants; NO2 is also a precursor to species such as nitric acid and nitrate aerosols which contribute to acidification of the environment. In November of 1996, we performed field studies to measure ambient NOx (NO, NO2) concentration in 28 street locations in Dhaka city. We divided two zones to identify the severance of the problem of NOx. The high concentration locations (black spots), zone I and less polluted areas, zone II. Zone I is identified as the locations where NO2 concentration exceeded 40 ppb, and consequently zone II is those locations less than this level. Among 28 street locations 16 of them identified as the black spots, where NO2 concentration observed more than 40 ppb. Maximum concentration observed 64 ppb at Malibag area, followed by Bijoynagar 63 ppb, and then Shapla Chattar 57 ppb. Figure 11 presents spatial distribution of NO2 concentration over Dhaka, in 28 road locations. The highest concentration location Malibag is a street intersection where motorized and non-motorized vehicles are allowed to travel, a very congested road in Dhaka. The hourly average traffic flow from Mogbazar to Malibag link is 2613 veh/h with an average speed 22 km/h, Paltan to Bijoynagar link 2920 with an average speed 22.85 km/h, and Bijoynagar to Kakrail link 2711 veh/h and mean vehicle speed 24.62 km/h. Figure 12 presents estimated ambient concentration to that of experimental data in seven road links in Dhaka. Observed concentrations in all locations show good correlation with estimated NO2 concentrations.

Conclusions

Bangladesh has yet to be implemented a National Air Quality Standard, there are no detail air quality regulations based on which Environmental Impact Assessment could be done. Very few works has been done on air quality measurements and national air pollutants estimates. The current study found the following results:

Acknowledgment

The authors wish to confer their thanks to Mr. Nowshad Bin Asheque and Mr. Rayhanul Islam for their cooperation in collecting data from Bangladesh.

Reference

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  2. Faiz, A. "Automobiles Emissions in Developing Countries - Relative Implications for Global Warming, Acidification and Urban Air Quality," Transportation Research, 1993,27A(3):167.
  3. Makela, K. "Lorries Dominate in Emissions", Nordic Road and Transport Research, 1991,1, 8 - 11.
  4. Taylor, G. "Global Warming and Transport in Developing Countries". Infrastructure Division, Professional Service Branch, Canadian International Development Agency (CIDA), Ottawa, Canada, 1991.
  5. Azad, A. K. and Kitada, T. ìStudy on the Concentration Distributions of SO2 and NO2 in the City of Dhaka, Bangladesh in Winter 1995-1996î Proceedings of the 4th JSCE Symposium on Global Environment, Tokyo, July 4 - 5, 1996, pp. 99-104.
  6. Ogawa & Company, USA, Inc., NO - NO2 Simultaneous Sampling Protocol, Using Ogawa Sampler, 1230 S. E. 7th Avenue, Pompano Beach, Florida 33060, USA.
  7. Kato, N. and Akimoto, H. ìAnthropogenic Emissions of SO2 and NOx in Asia: Emission Inventoriesî Atmospheric Environment, Pergamon Press Ltd., 1992, Vol. 26A, No, 16, pp. 2997 -3017.
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