AIR POLLUTION AND CONTRIBUTIONS OF PARTICULATE MATTER FROM DIFFERENT

TYPES OF DIESEL VEHICLES IN SRI LANKA

1 M.M.S.S.B. Yalegama 2N. Senanayake and 1Deputy Director, Air Resource Management Center, Battaramulla, Sri Lanka

2Additional Director, Natural Resource Management Center, Peradeniya, Sri Lanka

AbstractAtmospheric pollution within the country is caused mainly by transport, industries and fossil burning and contributions by minor industries like cement, mining and quarrying where large particulate emissions are observed. However, the air pollution was heavily felt in the major cities. Ambient air quality in Colombo is the worst as per data available whereas Kandy and the vicinity of the Puttalum Cement factory are the other two major concerns. Vehicle emissions by burning of diesel and petrol include suspended particulate matter, carbon monoxide, oxides of sulphur and nitrogen and benzene at higher rate than industrialized countries. In Colombo they are continuously been monitored and the major pollutant is identified as particulate matter from vehicle emissions. Therefore the main culprit is the Transport sector, and the levels increase around 7.00hrs. and 17.00hrs. PM10 is emitted mainly from diesel powered vehicles, which constitutes light duty vehicles, buses and trucks. The results of Urban Air Quality Management Project conducted by the Air Resource Management Center (AirMAC) indicate that the emission levels are highest in light duty diesel vehicles, which contributes 2/3rd of the total particulates emitted. An action plan -Clean Air 2000, was drawn up for Colombo, and surrounding areas under the Metropolitan Environment Improvement Programme in 1992 and the new plan of Clean Air 2009 is being developed by the AirMAC. A total of 50 recommendations of Clean Air 2000 Action Plan, only 10 of the recommendations either totally or partly implemented which is attributed to the absence of institutional mechanism for implementation.

Air pollution was not considered a serious problem as yet, even though in the Colombo metropolitan area, where 2/3rd of the urban population as well as over 60% of industries and registered vehicles are concentrated. Nevertheless, there is a definite increase in respiratory illnesses during the past decade where hospital admissions due to bronchial asthma has increased 240% from the year 1985 to year 1996.

Keywords: Clean Air Action Plans, Diesel vehicular emissions, Particulate Matter, Colombo City, Respiratory illnesses

1.1 IntroductionAir pollution can be broadly defined as the presence in the atmosphere of substances or energy is such quantities and of such duration liable to cause harm to human, plant or animal life. Air pollution has traditionally being studied by geographers and others in countries of urban and industrial growth, where it has been seen as a phenomenon concomitant with economic development. Until 1960’s pollutants were generally regarded as problems in the vicinity of individual emission sources or within or near urban areas, but subsequently, it showed pollutants are transported over long distances and were causing adverse effects on the environment in locations far away from the source (Elsum, 1987). Further, the focus on earlier pollution studies has been on occupational and public settings and lately on domestic and indoor settings was also considered (Ramakrishna, 1990). Most of the early sampling studies were carried out in rooftops and street corners and their validity became questionable. Therefore, today’s focus on these measurements are concentrated in various points such as emission from the source itself, pollution concentration in a specific environment and exposure, which is the concentration of pollution over time, and the dose. The major culprits on air pollution in developing countries are the emerging industries, emission of green house gases, vehicular emissions, burning of fossil fuel but miniscule in agriculture.

Last few decades of Sri Lanka have seen a sharp increase in human population which necessitated to produce more food and shelter and the growing economic demand and lifestyles, Sri Lanka today has grappled with a plethora of Environment problems associated with land water and atmosphere. The predominant meteorological conditions in tropics, where Sri Lanka is also a member country, generally considered favourable for minimizing the influence of air pollution though in some cases circumstances may actually worsen the problem (Sanhueza et al., 1982). Meteorological parameters such as wind direction, wind speed, vertical wind speed, solar radiation, barometric pressure, humidity, rainfall and ambient temperature play an important role in dispersion, dilution and transformation of air pollutants in the ambient air. Since Sri Lanka is situated closer to the equator within an altitude of 600 to 1000 N, it experience a typical tropical climate which is somewhat modified by the seasonal wind reversal of the Asiatic monsoons. When the wind speed is low, especially during Inter monsoons, the sea breeze during the daytime and the land breeze during the nighttime may be present. Since winds towards inland are regular air pollution in Colombo city, which is situated close to the coastal belt, could affect the interior-remote areas too. Further, the monsoon rains act as an effective cleansing agent, flushing particulate and other water-soluble gases out of the atmosphere.

1.2. Early studies on air pollution in Sri Lanka.Meteorological database of Sri Lanka is very wealthy and date back to more than 100 years. However, it is a physical database without any analytical data on different parameters such as composition and variation in atmospheric gases, rainfall intensities etc. as there were no facility due to lack of instrumentation. The earliest recorded pollution study in Sri Lanka was in the year 1983, where the Chemistry Department of University of Colombo initiated a programme to monitor Lead (Pb) in the air in Colombo metropolitan area as the fuels used by our vehicle fleet are high in Pb. During the period from 1989 to 1992 three Institutes namely; National Building Research Organization (NBRO), Central Environment Authority (CEA) and Ceylon Institute for Scientific and Industrial Research (CISIR) conducted some monitoring studies on air pollutants. In 1992, NBRO monitor air pollution in 49 locations in different parts of the country and was found that only 8 locations are critical and the rest either moderate (24) or excellent (17) and the critical areas are either main cities or near industrial areas. Again in 1994 they conducted quantitative assessment of sulphur dioxide (So2), nitrous oxide (No2), carbon monoxide (CO), suspended particulate matter (SPM) and Pb on seven locations. CEA during the same period studied the relationship of pollutant levels and volume of traffic movement in six roadside locations in Colombo city and found a good relationship. CISIR studies in 1991 at seven locations and showed that the results are comparable to developing ASEAN region country but the readings has higher total suspended particulate and fine dust. After receiving the Ambient Air Quality monitoring equipment in the year 1996 CEA contracted with NBRO to monitor air quality continuously in three fixed stations. After the establishment of Air Resource Management Center under the Ministry of Environment and Natural Resources with financial support from IDF several case studies and monitoring studies were undertaken in the country. 1.3. Sectors responsible for air pollution

Sri Lanka being a developing agricultural country several sectors, contribute to air pollution though not in a significant manner, unlike in developed countries, where the major contribution comes mainly from the Industrial sector. However, cumulative effect has reached critical levels in some locations. In Sri Lanka 60% of the industries are concentrated in main cities hence pollution is also concentrated mainly in cities. The major atmospheric polluting sectors are as follows.

1.3.1. Agriculture sector In

Agriculture sector emits pollutants to atmosphere in several ways. Agriculture practices releases pollutants such as pesticides vapour and dust to the atmosphere, from agriculture products and through emission of green house gases. Agriculture as an emitter of most prevalent green house gasses though not in large quantities it is important in the total picture. According to latest EPA inventory anthropogenic greenhouse gas emission contribute 7% of total carbon equivalent and about 28% methane and 70% of nitrous oxide (Schneider & Mc Carl, 2003). In terms of direct emissions agriculture is responsible for major pollutants such as

Methane emission by paddy fields and Livestock industry Nitrous oxide emission from fertilizer practices Carbon dioxide (CO2) emission from fossil fuels and product processing etc. (EPA, 1999).

During the last two decades agricultural production in Sri Lanka was increased by the use of fertilizer responsive high yielding varieties and by greater use of inorganic fertilizer, herbicides and insecticides. As farmers over use and/or misuse these chemicals they tend to pollute the environment. Sathaye & Reddy (1993) has indicated the cumulative share of CO2 emission from the developing countries between 1870 and 1986 is estimated to be only 15%, but with 76% of the global population living in developing countries, their share in energy related CO2 emission in 1986 was about 27%.

An important complicating factor in green house gases is their non-degradability. Atmospheric Concentration of carbon increase in the atmosphere due to green house gas emissions is never going to come back to its original concentration in the atmosphere but expected to reach new equilibrium levels where a fraction of some carbon remain in the atmosphere for several thousands of years (Joos et al ., 1999).

1.3.2. Power sectorSri Lanka has a relatively low rate of energy consumption of 1361kg of oil equivalent on per capita basis. The three principal sources of primary energy used in Sri Lanka constitute 57.1% from biomass, 11.4 % from hydropower and 31.5% from petroleum oil products. Power generation in Sri Lanka is mainly through hydropower before 1995, where in most years it accounted to 95%, which is suppose to be low in terms of pollution. This has reduced to 65% in the year 2000 (Perera, 2000). With the increase in demand for electrical energy, which is 6-8% in 1996 expected to rise to 9-10 % in next 20 years, hydropower generation alone cannot meet the demand and therefore other sources need to be used such as thermal power based on diesel and coal. The forecast for annual power consumption during the period 1998-2017 indicates a heavy shortfall between demand and supply, which is expected to meet by thermal power. This has risen sharply in recent years and in the year 2001 it accountant to more than half of gross production. Therefore in the future this sector will be a major source of air pollution and with green house gases emissions will have significant effect on air pollution (Wijesinghe, 2001). However abatement to some extent may be achieved by the use of high quality fuels and by suitable technologies.

1.3.3. Industrial sectorIn developed countries Industrial sector is the main source of air pollution. However, in Sri Lanka the most industries are concentrated in main cities while some are spread sporadically but sparsely in the country and therefore localized (NARESA, 1991) ex. Puttalam Cement Factory. Therefore, air pollution by this sector is partly masked by other polluting agents in main cities. In Sri Lanka air pollution to some significant extent is found in Colombo and Kandy cities and cement factory in Puttalam. Puttalam cement factory emits several tons of particulate matter causing considerable health hazard and economic loss to agriculture. However, air pollution due to industries is considered low and localized but due to dearth of data some argues that actual levels should be much higher than envisaged at present. The major pollutant in industrial sector is SO2 and Suspended particulate matter.

1.3.4. Domestic sector 2

The domestic sector is the least polluting in the country except in very exceptional cases where some localized effects from firewood and kerosene may occur. The contribution for air pollution in this sector comes from cooking and lighting with wood, kerosene and liquid petroleum gases (LPG). In near future the cooking in main cities where 60% of the population is residing has changed to LPG use curtailing the pollutant load to air significantly.

1.3.5. Transport sectorMain source of air pollution in Sri Lanka is by this sector especially in major cities worst of which is Colombo. This is supported by the fact that pollutant levels increase at 9.00hours and 17.00hours when people open and close workplaces for the day. Therefore mainly attributed to petroleum combustion. The Table 1 shows the contribution of this sector to the common pollutants though data for Pb is not given. The Pb contribution to air pollution is 100% from the fuel combustion (Anon., 1998)

Table 1: Estimated emissions from petroleum combustion

Source Suspended Particulate Matter

SO2 NOx Hydrocarbons CO

Transport % 88.2 4.3 81.6 99.78 99.9Industry % 9.2 93.5 17.1 <1 <1Power and commercial % <1 <1 <1 <1 <1Household % 2.5 <1 <1 <1 <1

Source :Metropolitan Environment Improvement Programme 1992

Since remarkable air pollution was observed in Colombo metropolitan area under Clean Air 2000, several research studies were undertaken during past few years. High correlation between SPM and traffic density in Colombo city while much of Pb in ambient air is derived from leaded petrol from petrol vehicles. Vehicular emission has immense contribution for rising pollution in Colombo. The annual average growth of diesel and petrol consumption has been 10 and 3.5 % respectively during the period 1991-1995 (MOFE, 1998).

In Sri Lanka diesel powered vehicle are popular and mostly used by the people, though vehicular emissions contribute more to air pollution. Chandrasiri & Jayasinghe (1988) indicated diesel engine exhausts contain less toxic gases but it has much higher particulate matter concentration. The observed levels of TSP, SO2, O3 and Pb in diesel smoke are significantly higher than air quality standards recommended by World Health Organization and Central Environment Authority (CEA), Sri Lanka. However, fuel economy is lower in petrol-powered vehicles as per Table 2 because of the fact that the number of vehicles includes tricycles and motor cycles which has a higher mileage per liter of gasoline. This vehicle fleet is expected to increase tremendously by the year 2010 thereby the potential for air pollution to reach critical levels is very significant. Further based on the emission rates of vehicles and the number and capacities of vehicles it has been predicted that the pollutant load will increase four fold by the year 2010 ( MOFE, 1998; Anon, 1990)

Table 2: Expected reductions in emission levels due to Liquid Petroleum Gas (LPG)

Percentage of Petrol Cars

Emission due to Petrol (mt)

Emission due to LPG (mt)

Reduction (mt)

30 9,506 1,819 7,68740 12,674 2,476 10,24850 15,843 3,032 12,81160 19,012 3,639 15,572

Source : Chandrasiri, 2003

It has been found that emission load could be reduced if the petrol vehicles could be converted to LPG use and is significant as shown in Table 2. Advantage in LPG is that it contain moderate levels of hydrocarbons (HC) very little CO and near zero SPM, more specifically PM10

1.4. Major air pollutantsMajor air pollutants are oxides of sulphur, nitrogen and carbon, ozone (O3), HC, Pb, and particulate matter etc. These air pollutants are emitted from vehicular emissions and well as from green house gas emissions. There are several of them, which are monitored in the country, namely, CO, NO x, SO2, SPM, Pb and HC including Benzene. The Central Environment Authority has formulated standards for different pollutants in the country and is given in Table 3.

Table 3: Standards for main air pollutants

Pollutant Average Concentration (ppm)1 hr 8 hr 24 hr 1 year

CO 40.00 10 - -CO2 0.40 - 0.15 -So2 0.35 - 0.10 -SPM - - 0.30 0.100O3 0.20 - - -Pb - - - 0.001

Source : CEA Report 1991

Based on these values a study was undertaken to monitor pollutant levels in 6 different sites in Colombo city and the concentration of CO is below standards whereas NO2 either reached the proposed standards or gone above.

Table 4: Concentration of pollutants in six different sites in the Colombo metropolitan

Site Concentration (ppm)CO NO2 Total Hydrocarbon

Panchikawatte 13.69 1.36 11.39Mattakkuliya 11.19 1.44 8.18Peliyagoda 15.75 1.64 9.81Town Hall 13.26 1.24 10.50Thummulla junction 14.98 1.59 10.22Wellawatte 16.90 2.03 9.64

Source : CEA Report 1991

The ambient air quality levels in the Colombo city were in general within the national standards but SO 2

is likely to exceed the national Standards. A study conducted in Colombo on pollutant concentrations due to vehicle emissions are given in Table 5.

Vehicular emission also causes heavy impact on human health. In Sri Lanka import and use of reconditioned vehicles and improper management of vehicle engines aggravate the bad quality of emissions causing increased hazards on human health. Though the institutional framework to mitigate such excessive vehicular emission is developed in the country their implementation has some problems and has therefore become impractical. Senanayake et al. (1999) has indicated that there is a strong association between ambient air pollution with respect to SO2 and oxides of nitrogen and acute childhood wheezing episodes in Colombo. Data from hospital admissions shows a definite increase in respiratory illnesses in the last decade. The number of bronchial asthma cases has increased from 62,574 in 1985 to 149,258 in 1996, which is an increase of 240%.

Table 5: Status of air pollution due to vehicle emission in Colombo

Pollutant Mean ConcentrationT.S.P 404 µg /m3 (9 h)

Pb 0.415 µg/ m3 (9 h)CO 4 ppm )3 h)SO2 0.019 ppm (3 h)

THC 2.7 ppm (3 h)CH4 1.9 ppm (3 h)

Source : Mathes et al. (1993)

Notable feature in Sri Lanka scenario on air pollution is that the geographical positioning of the country. Since the country is surrounded by the sea and the tropical monsoon winds, which provide rains to the country, and the sea breeze and the land breeze during the inter-monsoon period help the country to lower the concentration of atmospheric pollutants and disperse them thereby reaching critical levels are hampered. Raindrops can also combine with NO2 and SO2 to yield acid droplets. Although acid rains were not considered a problem in the country, recent research indicates that it occurs in some parts of the country. Illeperuma & Premakeerthi (1998) have monitored acid rains in several parts of the Island and the data obtained are given in Table 6.

Table 6: Incidence and quality of acid rains in different parts of Sri Lanka

Location pH Cl - (ppm) NO3 (ppm) SO4 (ppm)Colombo 5.89 2.22 0.57 2.95Galle 6.45 18.06 0.90 2.44Hambantota 5.89 10.00 1.89 2.00Peradeniya 6.26 2.77 0.19 0.76Puttalama 7.00 2.56 0.43 2.47Anuradhapura 6.00 1.63 0.74 0.05

High levels of sulphur and nitrogen interception by fog in Horton plains supports the suspicion that forest die back at the site is due to acid rains. However it may also possible because of the country’s position that the pollutants reaching Horton plains are not from national sources but from cross national boundaries due to wind effects.

2. Contribution of Different kinds of diesel Vehicles to the Particulate Matter in Sri Lanka

This part of the paper presents an analysis of the contribution of different kinds diesel vehicles to the total pollution load from diesel vehicles. Objective of the study is to identify the major polluter vehicle groups and assist policy makers make decisions accordingly.

2.1 Significance of StudyParticulate Matter less than 10µm (PM10) is a key pollutant that poses a significant threat in urban areas of Sri Lanka. Exposure to PM10 can result in both short and long term reductions in lung function because the particles are too small to be trapped by the nose and large enough that some deposition in the lungs occurs. PM10 is the pollutant that causes most of the air-pollution-induced reduction in visibility. The key health effect categories associated with PM include premature death; aggravation of respiratory and cardiovascular disease, as indicated by increased hospital admissions and emergency room visits, school absences, work loss days, and restricted activity days; changes in lung functions and increased respiratory symptoms; changes to lung tissues and structure; and altered respiratory defense mechanisms. Most of these effects have been consistently associated with ambient PM concentrations, which have been used as a measure of population exposure in a large number of community epidemiological studies. The estimated contribution of diesel smoke to the PM 10 in Colombo ambient air is around 70%. USEPA has concluded that diesel particulate is a probable human carcinogen based largely on the consistent association that has been observed between increased lung cancer and diesel exhaust exposure in certain occupationally exposed workers. Approximately 30 individual epidemiological studies show increased lung cancer risks of 20 to 89% within the study populations depending on the study. Analytical results of pooling the positive study results show that on average, the lung cancer risks were increased by 33% to 47%. While not all studies have demonstrated an increased risk (6 of 34 epidemiological studies summarized by the Health Effects Institute reported relative risks of less than 1.0), the fact that an increased risk has been consistently noted in the majority of epidemiological studies strongly supports the determination that exposure to diesel exhaust is likely to pose a carcinogenic hazard to humans. The concern for the carcinogenic health hazard resulting from diesel exhaust exposures is widespread, and several national and international agencies have designated diesel exhaust or diesel particulate matter as a “potential” or “probable” human carcinogen. The International Agency for Research on Cancer (IARC) in the late 1980s concluded that diesel exhaust is a “probable” human carcinogen. Based on IARC findings, the State of California identified diesel exhaust in 1990 as a chemical known to the state to cause cancer, and after an extensive review in 1998, listed diesel exhaust as a toxic air contaminant. The National Institute for Occupational Safety and Health has classified diesel exhaust as a “potential occupational carcinogen”. The World Health Organization recommends that “urgent efforts should be made to reduce [diesel engine] emissions, specifically of particulates, by changing exhaust train techniques, engine design and fuel composition”. Another aspect of diesel particulate that is a cause for concern is its size. Approximately 80-95% of diesel particle mass is in the 0.05 to 1.0 micron size range with a mean particle diameter of 0.2 microns. These fine particles have a very large surface area per gram of mass, which makes them excellent carriers for adsorbed inorganic and organic compounds that can effectively reach the lowest airways of the lung. Approximately 50 – 90% of diesel exhaust particles are in the ultrafine size range from 0.005-0.05 microns, averaging about 0.02 microns. While accounting for the majority of the number of particles, ultrafine diesel particulate matter accounts for 1-20% of the mass of diesel particulate matter.White, blue, and black smoke may be emitted from IC engines. Liquid particulates appear as white smoke in the exhaust during an engine cold start, idling, or low load operation. These are formed in the quench layer adjacent to the cylinder walls, where the temperature is not high enough to ignite the fuel. They consist primarily of raw fuel with some partially burned hydrocarbons and lubricating oil. White smoke emissions are generally associated with older gasoline engines and are rarely seen in the exhaust from diesel or gas-fueled units. They cease when the engine reaches its normal operating temperature and can be minimized during low demand situations by proper idle adjustment. Blue smoke is emitted when lubricating oil leaks, often past worn piston rings, into the combustion chamber and is partially burned. Proper maintenance is the most effective method of preventing these emissions from all types of IC engines.

The primary constituent of black smoke is agglomerated carbon particles (soot). These form in a two-step process in regions of the combustion mixture that are oxygen deficient. First the hydrocarbons decompose into acetylene and hydrogen in the high temperature regions of the cylinder. Then, when the local gas temperature drops as the piston moves down and the gases expand, the acetylene condenses and releases its hydrogen atoms. As a result, pure carbon particles are created. This mechanism of formation is associated with the low air/fuel ratio conditions that commonly exist at the core of the injected fuel spray, in the center of large individual fuel droplets, and in fuel layers along the walls. The formation of particles from this source can be reduced by designing the fuel injector to provide for an even distribution of fine fuel droplets such that they do not impinge on the cylinder walls. Once formed, the carbon will combine with oxygen to form CO and CO2 if it is still at an elevated temperature. Since the temperature of the exhaust system is too low for this oxidation to occur, soot exiting the combustion chamber before it has had the opportunity to oxidize completely will be discharged as visible particles. Because soot formation is very sensitive to the need for oxygen, its discharge is greatest when the engine is operating at rich air/fuel ratios, such as at rated power and speed. Therefore, naturally aspirated engines are likely to have higher smoke levels than turbocharged engines, which operate at leaner air/fuel ratios.

2.2 Particulate Pollution Level in Colombo CityMost of the urban areas of Sri Lanka are affected adversely by the emissions of diesel vehicles. The color of filter papers used to collect PM10 provides evidence for the level of particulate pollution caused by vehicles. The filter papers are carbon black. However, Colombo is the only city in Sri Lanka where the air pollution is monitored continuously. The PM10 levels recorded in Colombo are given in Graph 1.

Source: Central Environmental Authority

2.2.1 Comparison with WHO dose response relationships

Graph 1

Figure 1:

Source: World Health Organization

Figure 2:Source : World Health Organization

According to the Figure the mean PM10 level of 100µgm-3 causes an increase of about 7% in the daily mortality. The Figure shows the percentages by which daily mortality, hospital admissions, bronchiodialatory use, symptom exacerbation and peak expiratory flow increase with PM10 levels. However, Sri Lanka does not have this type of dose response relationship studies.

2.3 Fuel ConsumptionSri Lanka has a distorted fuel consumption pattern with use of diesel far exceeding the level of petrol. The fuel consumption pattern in million liters is given in Graph 2.

0

200

400

600

800

1000

1200

10,522 12,85313,952

15,45415,715

14,94715,267 17,805

21,56818,267

Mill

ions

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999

Diesel Petrol

Fuel Consumption by the Road Transport (1991 - 2000)

Graph 2

Source: Ministry of Transport, Sri Lanka

2.4 Vehicle Fleet in Sri LankaIn year 2000, the estimated total active vehicle fleet is about 1,165,000, which is about 1.9 times that in 1991. However, the vehicle ownership ratio has reduced from 28:1 in 1991 to 20:1 in 2000. The per capita petrol consumption has increased from 12.7 liters to 15.9 liters and that of diesel from 28.7 liters to 54.7 liters, from 1991 to 2000. This shows that per capital diesel consumption has increased by 91% but per capital petrol consumption has increased only by 25%, indicating a sharp changes in the fleet mix. The major changes are the rapid increase of three wheelers (as well as two wheelers) and the small diesel vehicles (due to pricing policy of diesel vs petrol and vehicle importation policies). These trends have aggravated the air pollution problems in the urban sector.The growth of total active vehicle population during last two decade is presented in the Figure 3.

Figure 3: Total active vehicle population

Source: Ministry of Transport, Sri LankaThe estimated active vehicle fleet characteristics of road transport in Sri Lanka in year 2000 are presented in the following Table 1.

Table 1: Active vehicle fleet characteristics in year 2000

Vehicle Type Fuel No. of Vehicles Average km/y Fuel Economy (Urban)

liters/100kmCars and light vehicles Gasoline 142,661 8,000 13.4Cars and light vehicles Diesel 18,267 15,000 9.2Taxis Gasoline 4,607 22,000 13.4Pick-up & Dual purpose Gasoline 9,418 8,000 16.6Pick-up & Dual purpose Diesel 110,236 21,000 12.1Minibuses Gasoline 1,389 30,000 16.6Minibuses Diesel 8,405 30,000 12.1Medium buses Diesel 15,717 30,000 38.1Heavy buses Diesel 10,311 63,000 43.84-wheel-drive Diesel 12,378 10,000 12.1Trucks Diesel 73,341 52,000 28.6Land Vehicles Diesel 59,937 12,000 28.6Motor-cycles 2-Stroke Gasoline 375,929 5,000 4.7Motor-cycles 4-Stroke Gasoline 200,495 7,450 3.9Motor-tricycles Gasoline 120,086 12,000 5.2

In addition to the road vehicles, other modes of transport in Sri Lanka include Railways (with effective fleet of about 200 diesel locomotives and 46 power sets), Navigation (which includes international marine transport and coastal shipping & fishing boats) and Aviation (with few organizations operating the local air transport).

2.5 Scope of the StudyThe study limits its scope to only the three main categories of diesel vehicles that are traveling in urban areas of Sri Lanka. These categories of vehicles are supposed to be contributing more than 90% of PM10 emitted from diesel vehicles. The vehicle categories so selected are diesel buses, diesel lorries and diesel light duty vehicles.

2.5.1 Methodology and AssumptionsThe methodology adopted in the study assumes that the k factor of diesel vehicles measured using the snap acceleration technique is directly proportional to the emission load from that particular vehicle. The differences in emission load due to different traffic conditions were considered similar in case of all types of vehicles. Contributions from more polluting vehicles were assumed to be compensated by less polluting vehicles so that making the average pollution level the same. The emission levels of a randomly selected sample of each vehicle type (minimum 30 vehicles from each vehicle category) were measured using the Opaci-meter. Mean k factors were calculated for each category and relative emission loads from each category were calculated multiplying the mean k factors by total number of vehicles in each category and number of kilometers traveled by those vehicle types.

2.5.2 Results & Analysis

Figure 4: Emissions of a bus

Figure 5: Emissions from a light duty vehicle

The

Patterns of k-factor distribution for the buses, lorries and light-duty vehicles are given in the Figures 6, 7 and 8 respectively.

Figure 6: Distribution of k factors for buses

Figure 7: Distribution of k factors for lorries

Figure 8: Distribution of k factors for light duty vehicles

Calculations of mean k factors

Mean k factor of light duty vehicles = 12.12 Standard Deviation 9.504Mean k factor of lorries = 5.72 Standard Deviation 5.57Mean k factor of buses = 5.89 Standard Deviation 7.52

Pollution loads from each vehicle types

(Calculated by multiplying mean k factor * number of vehicle * number of kilometers traveled per annum)

For light duty vehicles = 51451981560 (63.24%)For buses = 8088460170 (9.94%)For lorries = 21454704918 (26.81%)

2.5.3 DiscussionThe Standard Deviations for all three types of vehicles are very high compared to the mean. Therefore, this mean is not a very good measure to indicate the average k factor for a particular kind of a vehicle. However, since this is a comparative study, the impact to the total result has been minimized. Also the number of kilometers traveled is usually lesser in case of old vehicles and higher in case of new vehicles. Therefore, the multiplication by mean k factor does have an impact on the total calculated emission load. Here again the impact is minimized since this is a comparative study. Anyway, it shows around two-third contribution to particulate matter pollution from light duty vehicles. It should have the attention of the government on giving subsidies to diesel with the intention of facilitating the passenger and goods transportation. Who are really benefited by the government subsidy and who has had to bear the cost including cost of air pollution should be seriously considered and necessary fiscal policy measures should be taken.

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AcknowledgementsWe wish to acknowledge the financial assistance and continuous guidance given by the World Bank in implementing the Urban Air Quality Management Project in Sri Lanka. The assistance given by Task Manager Kseniya Lvovsky, Specialist Masami Kojima, Senior Engineer Dr. Sumith Pilapitiya and Ms. Eashwary Ramachandran is specially acknowledged.

The support given by the International Consultant Mr. Christopher Weaver, National Consultant Dr. Sugathapala and his team is greatly appreciated. In conducting the vehicle survey the assistance given by the Officers of the Ministry of Transport especially Dr. D.S. Jayaweera, the Secretary to the Ministry, Officers of the Department of Motor Traffic, especially Mr. A.W. Dissanayake, Assistant Commissioner, The Traffic Police, especially Mr. S.M. Wickremasinghe, S.S.P., and the AirMAC staff led by the Project Director Dr. B.M.S. Batagoda are highly appreciated.

The assistance given by the Programme Officers of AirMAC especially Mr. Ruwan Weerasooriya is greatly appreciated.