The effects of atmospheric aerosols on the atmosphere

The effects of atmospheric aerosols on the atmosphere

1.

Introduction

Nowadays, when human has a high level of living, our earth has exhausted of many kinds of environmental problems. Among these, the pollution has become a major threat to the very existence of mankind on this planet earth. The advancements of science and technology, on the one hand, have added to the human comforts by giving us automobiles, electrical appliances, better medicines, chemicals to control harmful insects and pests, etc., which have on the other hand, added a serious problem of pollution.

Air pollution is one of a variety of man-made environmental disasters that are currently taking place all over the world. It has a great impact on human health, climate change, agriculture, and the natural ecosystem (Decker et al., 2000; Mayer et al., 2000; Molina and Molina, 2004; Molina et al., 2004).

Because of the modernization and industrialization, developing countries are confronted with the great challenge of controlling the atmospheric pollution, specially in the rapidly growing megacities.

Concern about air pollution in urban regions is receiving increasingly importance worldwide, specially pollution by gaseous and particulate matter (Azad and Kitada, 1998; Salam et al., 2003; Begum et al., 2004; and Cachier et al., 2005). The particulate matters are commonly described by using a number of terms and the most common is “atmospheric aerosol�, which refers the colloidalsized atmospheric particles in gas.

Aerosol particles scatter and absorb solar and terrestrial radiation, they are involved in the formation of clouds and precipitation as cloud condensation and ice nuclei and thereby in hydrologic cycle and climate forcing, they affect the abundance and distribution of atmospheric trace gases by heterogeneous chemical reactions and other multiphase processes. (Penner et al., 2001; Ramanathan et al., 2001; Finlayson-Pitts et al.,2000). Moreover, airborne particles play an important role in the spreading of biological organisms, reproductive materials, and pathogens (pollen, bacteria, spores,

viruses, etc.), and they can cause or enhance respiratory, cardiovascular, infectious, and allergic diseases (Finlayson-Pitts et al.,2000; Bernstein et al., 2004; Hinds, 1999).

1.1. Background to Context Like different parts of the world, in Southeast Asia, the atmospheric pollution due to aerosols has already been documented. Recent large-scale field experiments in Southeast Asia (e.g. INDOEX) revealed the existence of widespread aerosol layers, including highly absorbing material (black carbon) and mineral dust (Satheesh and Ramanath, 2000).

Bangladesh, a developing country in South Asia where uncontrolled emission of gaseous pollutants and aerosols from motor vehicles and other anthropogenic activities related to extremely high population densities gives rise to severe atmospheric and other forms of pollution (Biswas et al., 2001). Dhaka, one of the mega cities of the world, witnessed a very fast growth of urban population in recent times. Air pollution in Dhaka city is reported to be serious and damaging to public health. In the winter of 1996-1997, air pollution of Dhaka city became the severest when lead in the air was reported higher than the other place of the world (Ahmed, 1997). Concern over air pollution rate of Dhaka city due to various toxic gases and articulate matters ultimately led to the promulgation of National Ambient Air Quality Standards in Bangladesh in 1997.

Besides mans and animals, air pollutant particularly atmospheric aerosols are detrimental to plants.

Plants are far more sensitive to pollution than animals or man. Therefore, plants are also used as indicators of pollution level. Soil is another important indicator of pollution. Various kinds of pollutants are deposited into the soil from air including the aerosol particles. Once the constituents of aerosols are introduced into the soil, they enter into the food chain, ultimately affecting human being and its cattle heads. Therefore, the air pollution due to aerosols along with other pollutants are not only coincides into the air but also causes soil pollution, poses threat to man, animal and also detrimental to water quality. As a whole, the constituents of atmospheric aerosols, beyond their reference level are a matter of great fact to the environment.

1.2.

Statement of the problem

The current study would like to know the composition and concentrations of the constituents of atmospheric aerosols in Dhaka city. This study evaluates the following questions: 1. What are the present concentrations of carbonaceous aerosols, inorganic ions and trace elements in the air of Dhaka city?

2. What are the concentrations of trace elements in soil, plant and humans during the study period?

3. What is the present air quality condition of the studied areas?

1.3.

Objectives

This study has four main objectives: First, to determine the contents of carbonaceous aerosols, inorganic ions and trace elements in the air, Second, to compare the contents of trace elements in soil, plant and human body, Third, to assess the level of toxicity of the determined trace elements present in soil, plant and human body, and Fourth, to evaluate the air quality situation based on the result.

1.4. Scope and Limitation The present study determined the different components of the aerosols and compared the concentrations of trace elements present in soil, plant and human blood with the contents of these elements in air. However, other parameters were not compared and the study area was only confined to six sites of Dhaka city and the effects of the constituents of aerosols on soil, plant and humans were compared by reviewing secondary data.

2. Review of Literature The effects of atmospheric aerosols on the atmosphere, climate and public health are among the central topics in current environmental research. Aerosol particles scatter and absorb solar and terrestrial radiation, they are involved in the formation of clouds and precipitation as cloud condensation and ice nuclei, and they affect the abundance and distribution of atmospheric trace gases by heterogeneous chemical reactions and other multiphase process (Finlayson-Pitts and Pitts, 2000 and Lohmann and Feichter, 2005). Moreover, airborneparticles play an important role in the spreading of biological organisms, reproductive materials, and pathogens (pollen, bacteria, spores, viruses, etc.), and they cancause or enhance respiratory, cardiovascular, infectious, and allergic diseases (Finlayson-Pitts et al.,2000; Bernstein et al., 2004; Hinds, 1999).

2.1. Atmospheric Aerosols 2.1.1. Definition Aerosols are ubiquitous and are an important feature of the earth’s atmosphere (Coe and Allan, 2006).

An aerosol can be defined as a dispersion of solid and liquid particles suspended in gas. Atmospheric aerosols, unsurprisingly, refer to solid and liquid particles suspended in air (Mészáros, 1981).

In most cases, this term is used to refer the particulate matter. But there is a slight difference between particulate matter and the atmospheric aerosol. Particulate matters (PM) are tiny subdivisions of solid matter suspended in a gas or liquid. In contrast, aerosol refers to particles and/or liquid droplets and the gas together. (http://en.wikipedia.org/wiki/Particulates).

2.1.2.

Classification

Aerosols are usually classified in terms of their origin and chemical composition ( Kokhanovsky, 2008). They are also classified into various subgroups based on the nature and size of the particles of which they are composed and, the manner of formation (Vallius, 2005).

2.1.2.1. Classification according to origin and chemical composition According to these criteria, the most important aerosol subgroups are (Kokhanovsky, 2008): a. Sea-salt aerosol - originates from the oceanic surface due to wave breaking phenomena. b. Dust aerosol – originates from the land surface. It is formed by the release of materials such as soil and sand, fertilizers, coal dust, cement dust, pollen, and fly ash into the atmosphere. It is composed of solid particles. c. Biological aerosol – Biological material is present in the atmosphere in the form of pollens, fungal spores, bacteria, viruses, insects, fragments of plants and animals, etc. d. Smoke aerosol – originates due to forest, grass and other types of fires. e. Volcanic aerosol – originates due to emissions of primary particles and gases (e.g., gaseous sulfur) by volcanic activity. Most of the particles ejected from volcanoes are water-insoluble mineral particles, silicates, and metallic oxides such as SiO 2, Al2O3 and Fe2O3, which remain mostly in the troposphere. f.

Anthropogenic aerosol – consists of both primary particles (e.g., diesel exhaust and dust) and secondary particles formed from gaseous anthropogenic emissions.

The main aerosol types with their annual emissions are given in table 2.1 as below: Table 2.1: Emissions of main aerosol types. Reported ranges correspond to estimations of different authors (Kokhanovsky, 2008) Aerosol Type Sea-salt aerosol Dust aerosol Biological aerosol Smoke from forest fires Volcanic aerosol Anthropogenic aerosol

Emission (106 tons per year) 500-2000 7-1800 80 5-150 4-90 181-396

2.1.2.2. Classification according to mechanism of formation Based on the mechanism of their formation aerosols can be classified into (Vallius, 2005; Kulkarni et al., 2011; Mészáros, 1981): a. primary and b. secondary.

Primary particles of aerosols are emitted directly as particles, whereas secondary particles are formed from precursor gases in the atmosphere via gas-to-particle conversion.

2.1.2.3. Classification according to particle size Particle size of the atmospheric aerosol is normally given as the aerodynamic diameter, which refers the diameter of a unit density sphere of the same settling velocity as the particle in question.

According to particle size aerosols are classified as (Vallius, 2005; Kulkarni et al., 2011; Mészáros, 1981; Reeve, 2002; EPA, 1982): a. Aerosol with coarse particle b. Aerosol with fine particle c. Aerosol with ultrafine particle Particles greater than 2.5 µm in diameter are generally referred to as coarse particles, and particles less than 2.5 µm and 100 nm in diameter as fine particles and ultrafine particles, respectively.

Very small, solid particles include carbon black, silver iodide, combustion nuclei, and sea-salt nuclei (see Figure 2.1). Larger particles include cement dust, wind-blown soil dust, foundry dust, and pulverized coal. Liquid particulate matter includes raindrops, fog, and sulfuric acid mist (Manahan, 2000).

Figure 2.1. Bursting bubbles in seawater form small liquid aerosol particles. Evaporation of water from aerosol particles results in the formation of small solid particles of sea-salt nuclei.

2.1.3.

Composition

The chemical composition of atmospheric particulate matter is quite diverse. Particles of atmospheric aerosols may be organic or inorganic (Manahan, 2000).

2.1.3.1. Inorganic constituents Among the constituents of inorganic particulate matter found in polluted atmospheres are salts, oxides, nitrogen compounds, sulfur compounds, various metals, and radio nuclides. In coastal areas, sodium and chlorine get into atmospheric particles as sodium chloride from sea spray. The major trace elements that typically occur at levels above 1 Îźg/m 3 in particulate matter are aluminum, calcium, carbon, iron, potassium, sodium, and silicon; note that most of these tend to originate from terrestrial sources. Lesser quantities of copper, lead, titanium, and zinc, and even lower levels of antimony, beryllium, bismuth, cadmium, cobalt, chromium, cesium, lithium, manganese, nickel, rubidium, selenium, strontium, and vanadium are commonly observed (Manahan, 2000).

2.1.3.2. Organic constituents Organic atmospheric particles occur in a wide variety of compounds. The neutral group contains predominantly hydrocarbons, including aliphatic, aromatic, and oxygenated fractions. The aliphatic fraction of the neutral group contains a high percentage of long-chain hydrocarbons, predominantly those with 16-28 carbon atoms. The aromatic fraction, however, contains carcinogenic polycyclic aromatic hydrocarbons( Williams, 2008, Mnahan, 2000)). Aldehydes, ketones, epoxides, peroxides, esters, quinones, and lactones are found among the oxygenated neutral components, some of which may be mutagenic or carcinogenic. The acidic group contains long-chain fatty acids and nonvolatile phenols. Among the acids recovered from air-pollutant particulate matter are lauric, myristic, palmitic, stearic, behenic, oleic, and linoleic acids. The basic group consists largely of alkaline Nheterocyclic hydrocarbons such as acridine (Manahan, 2000):

Figure 2.2. Acridine.

2.1.4. Sources of the constituents of aerosols Atmospheric aerosol particles may be emitted as particles (primary sources) or formed in the atmosphere from gaseous precursors (secondary sources) (Levin and Cotton, 2008). These sources can also be classified as natural and anthropogenic sources.

The likely sources of some of the inorganic constituents are given below (Manahan, 2000): • Al, Fe, Ca, Si: Soil erosion, rock dust, coal combustion • C: Incomplete combustion of carbonaceous fuels • Na, Cl: Marine aerosols, chloride from incineration of organohalide polymer wastes • Sb, Se: Very volatile elements, possibly from the combustion of oil, coal, or refuse • V: Combustion of residual petroleum (present at very high levels in residues from Venezuelan crude oil) • Zn: Tends to occur in small particles, probably from combustion • Pb: Combustion of leaded fuels and wastes containing lead • SO42-: Oxidation of sulphur-containing gases during fossil fuel combustion • NO3-: Gaseous nitrogen species Carbon originates as soot, carbon black, coke, and graphite originates from auto and truck exhausts, heating furnaces, incinerators, power plants, and steel and foundry operations.

2.1.4.3. Carbonate Carbon Less common carbonate minerals include dolomite (MgCa (CO3)2), aragonite, a calcite polymorph (mineral of the same composition as calcite but having a different atomic structure), azurite and malachite (copper hydroxycarbonate minerals), siderite (FeCO3) and rhodochrosite (MnCO3) which can be important spatially and economically.

2.1.5.

Sinks of atmospheric aerosols

Once aerosol is suspended in the atmosphere, it is altered, removed or destroyed. It cannot stay in the atmosphere indefinitely, and average lifetimes are of the order of a few days to a week. Clearly the lifetime of any particular particle depends on its size and location. Larger aerosol settle out of the atmosphere very quickly under gravity, and some surfaces are more efficient at capturing aerosol than

others. Some removal pathways of the particle to the surface are (Chandrasekar, 2010, http://cloudbase.phy.umist.ac.uk/people/dorsey/Aero.htm): Wet deposition- deposition pathways involving water. They include rainout, washout, sweep out and occult deposition.

Dry Deposition- deposition pathways are the group of deposition mechanisms that transport particles directly to the surface without the aid of precipitation. Gravitational Settling, Turbulent Deposition etc. are examples of dry deposition.

2.2.

Atmospheric Aerosols in Urban Areas

The majority of total particle emissions to the atmosphere that contribute to aerosol formation are attributable to natural sources, such as suspended terrestrial dust, oceans and seas, volcanoes, forest fires and natural gaseous emissions. However, these emissions are dispersed rather evenly into the atmosphere and, therefore, result in a relatively low tropospheric background particle concentration.

The natural sources that have the greatest impact on the urban particle concentrations in Europe include suspended terrestrial dust, sea salt spray (mainly at coastal sites) and biomass burning (forest fires) (Salaman et al., 2007).

The major sources of anthropogenic, i.e., man-made, particles include: a. Transportation, b. Stationary combustion, c. Space heating, d. Biomass burning, and e. Industrial and traffic-related fugitive emissions (street dust).

The major components of urban atmospheric aerosols are typically sulphate, ammonium, chloride, elemental carbon, organic carbon, crustal materials and biological materials (bacteria, spores, pollens, debris and plant fragments) (Harrison et al., 1997).

The distinction between anthropogenic and natural particle sources and the emitted particulate matter is sometimes difficult to make, for example, fugitive dust emissions and biomass burning (BĂŠruBĂŠ et al., 1997). In addition, there are large differences in the relative importance of different sources from one geographical area to another. For example, the greater part of emissions of primary particulate matter in eastern parts of Europe originates from stationary combustion sources and processes, whereas in western parts of Europe, emissions are more evenly distributed among all economic sectors, although transport emissions play the most significant role at many locations (ApSimon et al.,

2000). In urban areas Aerosol mass concentrations range from a few tens of μg/m3 to 1 mg/m 3 during air pollution episodes in heavily polluted cities in developing countries.

The most common way to present particle size distribution data for the urban aerosol is in terms of the three modes: nuclei mode (particle size< 0.1 μm, usually found near highways and other sources of combustion), accumulation mode (0.1 μm< particle size < 2.5 μm, includes combustion particles, smog particles, and coagulated nuclei-mode particles), and coarse particle mode (particle size>2.5, consists of windblown dust, large salt particles from sea spray, and mechanically generated anthropogenic particles) (Sakulyanontvittaya, 2008).

Table2.2

summarizes

the

three

modes

of

urban

aerosols

and

their

corresponding

characterization(http://www.aerosols.wustl.edu/education/atmos_aerosol/section04.html).

Table 2.2. Modes of Urban Aerosol Modes of urban aerosol Nuclei Mode

Sources Combustion particles; gas-toparticle conversion

Accumulation Mode

Combustion particles; smog particles; coagulated nuclei-mode particles

Coarse Particle Mode

Windblown dusts; salt particles from sea spray; volcanic eruption anthropogenic particles from agriculture and surface mining

Characterization 0.001-0.1 μm; high concentration; rapid coagulation; short lifetime 0.1-2.5 μm; slow coagulation; long lifetime; accounting for most of visibility effects 2.5-100 μm; readily settle down on surface; short lifetime

Average composition of fine and coarse particles in urban air is given in table 2.3 ( Pitts and Pitts, 1986).

Table 2.3. Average composition of fine and coarse particles in µg/m 3 at an urban site.

Total Mass SO42NO3NH4+ H+ C Al Si S Ca Fe Pb

Urban Fine 42 17 0.25 4.3 0.067 7.6 0.095 0.2 0.15 0.17 0.48

Coarse 27 1.1 1.8 <0.19 <0.01 3.3 1.4 3.8 3.1 0.73 0.13

2.3.

Impact of Atmospheric Aerosols on Soil, Plant and Human

2.3.1. Effects on Soil Atmospheric aerosols are deposited on different parts of the environment including the soil. Different constituents of aerosols are then accumulated in the soil with the course of time. This accumulation causes pollution of soil. The pollution of soil from the accumulation of trace elements is a matter of great concern as these elements are required by plants in a relatively very small quantity.

2.3.1.1. Aerosol Vs Soil Pollution 2.3.1.1. Definition of Soil Pollution Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents, which have adverse effects on plant growth and animal health.

2.3.1.2. Sources of soil pollutant from Aerosols The most common chemicals involved in causing the soil pollution are: • Petroleum hydrocarbons • Heavy metals • Pesticides • Solvents 2.3.2.

Effects on Plant

The attenuation of radiation by Aerosols results in less photosynthetically active radiation (PAR), which is the radiation between 400-700 nm, reaching the surface. The resultant decrease in PAR may significantly decrease crop production in these regions (Sakimoto, 1997). Particulate matter can clog stomatal openings of plants and interfere with photosynthesis functions. In this manner high particulate matter concencentrations in the atmosphere can lead to growth stunting or mortality in some plant species.

The following figure shows the relationship between τ500 and PAR corrected for the solar zenith angle (μ = cosine of the solar zenith angle) based on measurements during cloud-free conditions in an agricultural region of China(Chameideset al., 1999).

Figure 2.5. Relationship between down welling PAR and Ď&#x201E;500 during cloud-free conditions in the Yangtze delta region of China during Nov.-Dec., 1999.

2.3.3.

Effects on Human Health

The atmospheric aerosol has significant influences on our health. They can cause reduced lung functions, increased respiratory symptoms, cardiovascular diseases, and so forth.

Inhalation of particulate matters (PMs) in the atmosphere can directly or indirectly lead to or deteriorate various symptoms/diseases. They include asthma, hay fever, increased respiratory symptoms, pulmonary inflammation, reduced lung function, and cardiovascular diseases. Recent evidence suggests that small PMs may be related to increased lung cancer risk. It is also suggested that long-term exposures to PMs have larger and more persistent cumulative effects than short-term exposures.

The following graph shows that increased PM concentrations in the atmosphere are associated with an increased mortality.

Figure 2.6. Concentration of atmospheric aerosol versus the mortality (http://www.aerosols.wustl.edu/education/atmos_aerosol/section07-2.html) Bangladesh is a developing country in Southeast Asia with a rapid growing population of about 150 million. Pollution of the environment in some areas is a major problem in Bangladesh threatening environmental quality and ecosystem. Air, soil and water pollution problem is particularly serious in the rapidly urbanized and industrialized cities of South and East Asia especially in the mega cities (Faiz and Sturn, 2000).

3. Methodology Aerosol, soil, plant and human blood samples were collected from different places of Dhaka city to evaluate the chemical composition of atmospheric aerosols in air and their concentrations in soil, plant and human body. To produce a usable output, required secondary data such as meteorological data, statistical data etc. were collected from relevant departments/literature. Present research design and data analysis arrangement have been illustrated in

Figure 3.1.

Research Design Objectives 1. To determine the contents of carbonaceous aerosols and trace elements in the air.

2. To compare the contents of trace elements in soil, plant and human body.

3. To assess the level of toxicity of the determined trace elements present in soil, plant and human body.

4. To evaluate the air quality situation based on the result.

Sample Analysis Laboratory analysis of sample

Data Analysis and Interpretation Microsoft Excel

Descriptive Statistics

Microsoft Excel

Descriptive Statistics Outp ut Air quality situation of the investigated areas of Dhaka city Fig-3.1. Flowchart of research design

3.1. Study Area Dhaka is the capital of Bangladesh and one of the major cities of South Asia. Dhaka, along with its metropolitan area, had a population of over 16 million in 2011, making it the largest city in Bangladesh ("Statistical Pocket Book, 2008"(PDF). Bangladesh Bureau of Statistics). It is not only the capital of Bangladesh; it is also the center of commerce and industry of Bangladesh. It is located in central Bangladesh at 23°42′0″N 90°22′30″E, on the eastern banks of the Buriganga River (Fig. 3.1.1).

The city is congested with a large number of motor vehicles, including both public and private transportation. Moreover, construction of roads and buildings are taken place continuously throughout the city. The sampling locations were selected to reflect different influences form mobile sources in

the highly populated central part of Dhaka. The sampling sites are Curzon Hall (Dhaka University Campus), Dhanmondi, Farmgate, Mirpur, Mohalhali and Mohammadpur (Fig. 3.1.2).

3.1.1. Sampling Sites Site I: The location of the first sampling site was Curzon Hall which is a part of the school of science of the University of Dhaka. It is located between 23ยบ43'33.62'' N longitude and 90ยบ24'16.43'' E latitude (Apendix). Dwell Chattar is in front of the Curzon Hall. Bangladesh Shishu Academy is straightforward to Curzon Hall. Motsho Bhaban and Press club are in the right corner of this place. It is only about 500 yards close to Chankharpul from the east and a quarter km away from Shahbag.

Although too much vehicles are not allowed in this place but three roads beside the Curzon Hall are running to press club, Chankharpul and Bangabazar have moderate load of vehicles. Buses, auto rickshaws, tempos, cars and other types of motor vehicles pass through these roads for almost twentyfour hours.

Fig-3.1.1. Map of Dhaka City.

5

4

6 3

2

1

LEGEND Sampling sites

Fig-3.1.2. Map of Dhaka city showing the sampling sites represented by 1,2,3,4,5 and 6 that pointed Curzon hall, Dhanmondi, Farmgate, Mohakhali, mirpur and Mohammadpur respectively.

Site II: The second sampling site was Dhanmondi, located between 23º44'47.27'' N latitude and 90º22'33.64'' E longitude (Apendix). It has been traditionally known as a residential area. However, nowadays it is more of a commercial area than a residential area. The increasing number of commercial establishments, such as schools, universities, hospitals, restaurants and shopping centers has given rise to a tremendous amount of traffic congestion, especially during the mornings and afternoons. Different types of vehicles such as cars, auto rickshaws, buses, mini-buses and other types of motor vehicles pass through the roads of Dhanmondi.

Site III: Farmgate an important place of Dhaka was the third sampling site. It is located between 23º45'21.99'' N longitudes and 90º23'13.91'' E latitude (Apendix). This is one of the busiest and most crowded areas of Dhaka city. From the early 1990s, the area has seen massive building and construction boom. Consequently, the area has got commercial importance and nowadays it has become one of the major transportation hub of Dhaka from where anyone can travel all other parts of the city as well as throughout the country. Today Farmgate has become a more commercial area than a residential area. Neighboring places of Farmgate are Kawran Bazar, Pantapath, National Parliament, Rajabazar etc. As a transportation hub of Dhaka, the area is most often remains crowded and thousands of cars, rickshaws, minibus, bus, trucks remain stranded for even hours in the roads and streets of Farmgate.

Site IV: The forth-sampling site was Mohakhali. It is an important and busy area of Dhaka city. It is located between 23º46'39.46'' N longitudes and 90º24'19.62'' E latitude (Appendix). Many important offices and institutions are based in Mohakhali. Mohakhali Bus terminal is one of the most important terminals of Dhaka city. Every day thousands of people, particularly from greater Mymensingh region, travel by this bus terminal. It also has several gas stations. On its north there is Banani. On its south, there is Moghbazaar. The area is most often remains crowded and thousands of cars, rickshaws, minibus, bus, trucks remain stranded for even hours in the roads and streets of Mohakhali.

Site V: Mirpur was the fifth sampling site. It is located at 23º47'33.41'' N longitude and 90º21'38.57'' E latitude (Appendix). Historically it is known as residential area. However, with the increase of population many commercial infrastructures were established here during eighty’s. Nowadays it is more of a commercial area than a residential area. The increasing number of commercial establishments, such as schools, universities, hospitals, restaurants and shopping centers has given rise to a tremendous amount of traffic congestion. Different types of vehicles such as cars, auto rickshaws, buses, mini-buses, tracks, tempos and other types of motor vehicles pass through the roads of Mirpur.

Site VI: Sixth site was the Mohammadpur. It is located at 23º45'48.46'' N longitude and 90º22'06.47'' E latitude (Appendix). Though initially Mohammadpur has grown as a residential area, nowadays

many commercial places can be found here. It is connected to both Sadar Ghat and Gabtali by the city protection dam. Mohammadpur borders Shyamoli and Adabar on the north, Sher-E-Bangla Nagar on the east and Lalmatia on the south. Because of its position in the Dhaka city, it is now becoming busier area day by day and this gives rise to the pollution of the environment of that are. Until now, this area has moderate traffic load in comparison to other sites of Dhaka. Different types of vehicles such as cars, auto rickshaws, buses, mini-buses and other types of motor vehicles pass through the roads of Mohammadpur.

3.2. Sampling Period Meteorologically, the year of Bangladesh is divided into four seasons, pre-monsoon (March–May), Monsoon (June-September), post-monsoon (October-November) and winter (December-February).

Aerosol, soil, plant and human blood samples were collected in the months of October and November, i.e. in the post monsoon season. During the sampling period, the average temperature variation was 27-32ºC. Moderately higher temperatures were observed in the afternoon. Sunny days were observed during the sampling period with an average wind speed of 3 Km/hr (source: Bangladesh Meteorological department).

3.3. Sample Collection 3.3.1. Aerosol Sample Aerosol samples were collected by two sets of low volume samplers. The samplers were equipped with poly-carbonate open-face filter holders. One sampler was supported with PTFE filters (Pall Corp., Gelman Lab., Zefluor, 1.0 µm pore size, 47mm diameter) applying an averaged sampled air volume of 25 m3, and the other sampler was with quartz fiber filters (Gelman, Membrane Filters, Type TISSUQUARTZ 2500QA-UP, 47 mm diameter) applying an averaged sampled air volume of 22 m3. Sampling periods were around 8 hour (daytime, 10.00 a.m. 18.00 p.m.). To collect the aerosol samples sampling heads were placed 3m above the ground as the open-face filter sampling heads faced downwards and for protection from rains, sampling heads were sheltered by 10 L polyethylenebuckets, which were mounted on a pile the open side down. This yielded an aerosol fraction equivalent to “Total Suspended Particles” (TSP).Field blanks were determined for each sampling site and considered for the calculation procedures. The loaded filters were stored in clean Millipore Petri dishes and kept under refrigeration during the sampling. The total replication numbers of the samples were divided into two. Half of the replications were transported to Vienna, Austria, by air luggage for some chemical analysis and from the other half of the sample’s replication the analysis of trace elements were conducted in the Advanced Laboratory of the Department of Soil, Water and Environment of Dhaka University.

3.3.2. Soil Sample Soil samples were collected from each sampling site. Soils at 0-15 cm depth were collected by using spade and trowel. Soil samples from three points were collected from open bare ground near each airsampling site and mixed thoroughly. The collected soil were packed by polyethylene bag and labeled properly with a marker pen.

3.3.3. Plant Sample Plant Samples (grasses) were collected from the same three points of each sampling site, from where the soil samples were collected. The collected samples were packed by polythene bag and labeled properly with a marker pen and were taken to the laboratory as soon as possible for their analysis.

3.3.4. Human Blood Sample Blood Samples of humans were collected from the traffic police working at the each sampling site. 5 CC blood samples were collected and stored in test tubes having caps. These samples were then kept in the refrigerator of pathology for their preservation until analysis.

3.4. Processing of Samples 3.4.1. Processing/Preservation of Aerosol sample Before the refrigeration of aerosol sample, the weight of loaded material in the filter was recorded and also the weight of empty filter paper. From the difference of these two weights the weight of collected particles were measured and then stored in refrigerator. Aerosol samples did not require further processing. But, during the analysis the samples were treated in different ways according to the requirements of analysis.

3.4.2. Processing of Soil Sample Each of the collected soil samples was dried in air by spreading on separate sheet of paper after it was transported to the laboratory. For hastening drying, it was exposed to the sunlight. After air drying, the larger and massive aggregates and gravel were broken by crushing them gently with a wooden mortar. Dry roots, grasses and scrubs were discarded from the sample. A portion of the ground samples were screened to pass through a 0.5 mm sieve and then mixed thoroughly to make a composite sample was kept in a plastic container and labeled properly.

3.4.3. Processing of Plant Sample The collected plant samples were washed with de-ionized distilled water to remove the soil particles.

Roots, leaves and shoots were separated by cutting it after transporting to the laboratory. The collected plant samples were initially dried in air and ten cut into small pieces. The plant samples were then put into an envelope with – proper labeling and kept in an oven at 654ºC for 48 hours. After oven drying, the plant samples were cooled and then ground in an electric grinder. The ground plant samples were mixed thoroughly. The samples were kept in a plastic bag with proper labeling and stored in desiccators for further analysis.

3.4.4. Processing/Preservation of Blood Sample After the collection of blood samples, the samples were preserved in refrigerator in test tubes with caps. These samples did not require further processing and were analyzed within a very short time after the collection.

3.5. Laboratory Analysis 3.5.1. Analysis of Aerosol Sample Analysis of aerosol samples were conducted both in the laboratory of the Department of Soil, Water and Environment of the university of Dhaka, Bangladesh and in Vienna. The trace element contents were determined in Bangladesh and the contents of carbonaceous aerosols and soluble ions were determined in the Laboratory of Vienna, Austria. a) Total Carbon (TC) Total carbon was determined by combustion method in a set up originally described by Puzbausm and Rendl (1983). One aliquot of the quartz fiber filter (a punch of 12 mm ∅) was combusted in an oven at 1000ºC in a pure oxygen stream. The resulting CO2 was detected using a Maihak Unor 6N Nondisperisvie Infrared (NDIR) analyszer. The area of the CO2 peaks was calibrated using phthalic acid standards corresponding to 1-100μg C. TC can be described as “ noncarbonated carbon” (e.e. sum of elemental and organic carbon), as carbonate carbon determined with the thermo graphic method from a selected set of samples was about 1% of TC.

b)

Elemental Carbon (EC)

Elemental carbon was determined with two-step thermal method of Cachier et al. (1989) following exactly the prescribed procedure. The filter (a punch of 10 mm ∅) was pre-treated thermally for two hours in a muffle oven at 340ºC in a pure oxygen atmosphere (flow 3 L/min). By this treatment,

according to Cachier et al. (1989), the organic material is removed, whereas the elemental carbon remains on the filter punch. Then it was introduced into the above described combustion unit for TC -0 yielding the EC value after “Cachier”. A round robin test of EC/OC methods on urban samples from Berlin showed good agreement of the “Cachier” method with other methods considered reliable in the test (Schmid et al., 2001).

c)

Organic Carbon (OC)

Organic carbon was determined by Sunset OC/EC analyzer and for the analysis NIOSH protocol was used. d) Carbonate Carbon (CC) The carbonate carbon was determined from the difference between Total carbon and the sum of elemental and organic carbon: CC=TC – (EC+OC). e) Ion analysis Quartz fiber filter aliquots (3 punches of 10 mm Ø) were extracted for 20 minutes ultrasonically in 3.5 ml ultra pure water. Anions (chloride, nitrate and sulfate) and cations (Na +, K+, NH4+, Mg2+, Ca2+) were analyzed with ion chromatography. Details of the analytical method were given by Löflund et al., 2001) with the exception, that an auto sampler (Spark Holland Marathon) was used to deliver the samples instead of trace concentrator columns. Field blanks were determined for each sampling site and considered for the calculation procedures. f) Trace Elements (Pb, Cd, Zn and Cu) The whole PTFE membrane filters were extracted with 5 ml of 10% HNO 3 (V/V) about 40 minutes in an ultrasonic bath and then analyzed for the trace elements. Cadmium, copper and lead were determined by Atomic Absorption Spectroscopy (AAS), Perkin Elmer, and Model 370 with a graphic furnace HGA 74. Zinc was determined by AAS with a Perkin Elmer, Model 403 with an acetylene air flame. Iron was determined by AAS with a Perkin Elmer, Model 4100 ZI with a graphite furnace and with Zeeman background correction. Calibration was done with three standard solutions of different concentrations.

3.5.2. Analysis of Soil Sample In the laboratory, two main groups of analyses were done for soil sample. One was physical and physico-chemical analysis and the other was the analysis of trace elements in soil.

3.5.2.1. Physical Analyses of Soil a) Soil Moisture Content The percentage of moisture present in the air dried soil sample was determined by drying a known amount of soil in an electric oven at 05ºC for 24 hours until constant weight and the moisture percentage was calculated from the loss of moisture from the sample as described by Black ( 1965).

B) Particle Size Analysis The particle size distribution of the soil sample was determined by Hydrometer methods as described

by Black (1965). One the portion of sample was sieved through 2.0 mm size and the textural classes were determined from the Marshall’s Triangular Coordinates as outlined by the United States Department of Agriculture (USDA, 1951).

3.5.2.2. Physico-chemical and Trace Element Analyses of Soil a) Soil Reaction (pH) The pH of the soil was measured electrochemically by using a JENWAY PHM10 combined electrode digital pH meter. The ration of soil to water was 1:2.5 as outline by Jackson (1973).

b) Electrical Conductivity (EC) Electrical conductivity of the soil was measured at soil to water ratio of 1:5 using a NENWAY PC M1 EC meter as described by USSL Staff (1954).

c) Organic Carbon (OC) Soil organic carbon was determined volumetrically by Walkley and Black’s wet oxidation method as outlined by Jackson (1962).

d) Extractable Heavy metals (Pb, Cd, Zn and Cu) Heavy metals of soils were extracted by hydrochloric acid and nitric acid (3:1) mixture. The elements present in the extract were determined by using a VARIAN AA240 Atomic Absorption Spectrometer (AAS).

3.5.3. Analysis of Plant Sample a) Heavy Metals (Pb, Cd, Zn and Cu) Heavy metals of plant samples were digested with nitric acid and perchloric acid (5:1) mixture. The elements present in the extract were determined by using a VARIAN AA240 Atomic Absorption Spectrometer (AAS).

3.5.4. Analysis of Blood Sample a) Heavy Metals (Pb, Cd, Zn and Cu) Heavy metals of blood samples were digested with nitric acid and perchloric acid (5:1) mixture. The elements present in the extract were determined by using a VARIAN AA240 Atomic Absorption Spectrometer (AAS).

4. Results and Discussion

4.1. Analyses Result of Aerosol Sample Carbonaceous aerosol, soluble ions and trace elements were determined from the suspended particles (TSP) collected from the six sites of Dhaka city. Average concentrations of the determined components of the urban sites are summarized in table 4.1.1, 4.1.2 and 4.1.3.

4.1.1. Elemental carbon Elemental carbon (EC), also called black carbon (BC), was determined at Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur (Dhaka city) in Bangladesh. The average concentrations of elementary carbon ranged from 0.29-0.78 μg/m 3 in these sites (Table 4.1.1.). The highest

EC

of

these

sites

was

observed

at

Mohakhali

followed

by

Mirpur,

Mohammadpur,Dhanmondi, Curzon Hall and Farmgate. The average value of EC in urban sites of Dhaka are 0.46 μg/m3.

There are no international air quality standards for elemental carbon. But there is alternative guideline value of 8 μg/m3 in Germany ( TA – Luf, 1995). It has to be pointed out, that inter-comparison of EC (and OC) value between different studies bear uncertainties as results are quite dependent on the method used for EC/OC determination (Schmid et al., 2001). It appears that the EC levels in European, US and East Asian cities (e.g. Tokyo, Japan) are below 10 μg/m 3, whereas at large cities in the Indian sub-continent EC levels were above 10 μg/m3.

Elemental carbon in the air has different sources such as diesel engine emissions. Fossil fuel combustion at low burning efficiency and biomass burning (Salam et al., 2003). Emission from diesel engines, as well as from oil and coal fired stationary sourcres, exhibit EC/TC ratios around 0.1 – 0.2 have been reported (Cachier et al., 1995; Novakov et al., 2000), although for fuel wood combustion in India, quite higher values e.g. 0.6 have been observed (Reddy and Venkataraman, 2002), yielding an averaged EC/TC ratio of 0.25 for total biomass combustion emissions of India. The EC/TC ratio might also be shifted to lower values by admixture of OC from non-pyrogenic sources. Thus, it can be concluded that biomass fuel combustion is a major source of EC in the atmosphere of Dhaka.

4.1.2. Organic Carbon Oranic carbon (OC) is a complex mixture of several hundreds of organic compounds. The average organic carbon (OC) at the six areas of Dhaka was in the range of 3.32-10.36 μg/m 3 (Table 4.1.1). The highest OC of these sites was observed at Mohakhali with very high traffic congestion followed by Mirpur, Dhanmondi, Mohmmadpur, Farmgate and Curzon Hall.

Organic carbon (OC) has potentially even more sources than EC, as in addition to diesel engine emissions, fossil fuel combustion at low burning efficiency, biomass burning, also gasoline driven cars emit OC; but also cooking contribute OC emission (Salam et al., 2003). The grand average value of urban sites is 5.24 μg/m 3. A value of around 6 μg/m 3 has been attributed in the South African Savanna originating from natural vegetative sources (Puxbaum et al., 2000). High OC values as observed in Dhaka, up to 10.36 μg/m3 as site average, can be only explained because of anthropogenic activities. There is the possibility that a certain function of the OC is derived from biogenic sources.

4.1.3. Carbonate Carbon The average concentrations of carbonate carbon (CC) ranged from 0.02-0.35 μg/m 3 in the investigated six sites of Dhaka city (Table 4.1.1.). The highest CC of these sites was observed at Farmgate, followed by Dhanmondi, Mohakhali, Mirpur, Mohammadpur and Curzon Hall. The average

values of CC in urban sites of Dhaka are 0.10 μg/m3.

4.1.4. Soluble ions The soluble ions of urban Dhaka exhibited principle promotions of sulphate and calcium. The remarkable presence of nitrate was also observed in a few places

4.1.5. Trace Elements The highest average concentrations for measured trace elements were observed for zinc followed by lead copper and cadmium (Table 4.1.3). The highest lead concentration of urban sites was observed at the site with very high traffic Farmgate, followed by Mmohakhali, Curzon Hall, Dhanmonadi, Mirpur and Mohammadpur.

The highest cadmimum concentration of urban sites was observed at the site with high traffic Dhanmondi, followed by Curzon Hall, Mirpur, Farmgate, Mmohakhali, and Mohammadpur (Table 4.1.3) The highest zinc concentration of these sites was observed at the site with highly trafficked Mohakhali, followed by Dhanmondi, Curzon Hall, Farmgate, Mirpur and Mohammadpur. The average zinc concentration at urban areas of Dhaka was 462.85 ng/m 3. Zinc was correlated with Pb, Cu and NO3-.

The copper levels at the urban areas of Dhaka varied from 72.29-397.05 μg/m 3 air. It was correlated with Na and Zn (Table 4.1.4) Table 4.1.1. Carbonaceous aerosol in Dhaka city. All units are in µg/m 3.

Parameter

OC EC CC TC OC (%) EC (%) CC (%) Na+

Location Curzon Hall SizeTSP 3.32 0.35 0.02 3.69 82.73 16.48 0.79 0.9

Dhanmondi

Farmgate

Mohakhali

Mirpur

Mohammad pur

Size-TSP

Size-TSP

Size-TSP

Size-TSP

Size-TSP

5.43 0.36 0.08 5.87 90.1 8.75 1.15 0.18

3.39 0.29 0.35 4.03 88.8 9.95 1.25 0.14

10.36 0.78 0.07 11.21 88.23 11.12 0.65 0.24

5.5 0.51 0.04 6.05 87.72 11.1 1.18 0.29

3.46 0.47 0.04 3.97 81.25 11.80 0.95 0.11

Table 4.1.2. Soluble ions in the air sample of Dhaka city. All units are in µg/m 3.

Parameter

NH4+ K+ Mg2+ Ca2+ ClNO3-

Location Curzon Hall

Dhanmondi

Farmgate

Mohakhali Mirpur

Mohamma dpur

Size-TSP 0.48 0.26 0.05 2.54 0.29 2.08

Size-TSP 0.32 0.29 0.07 5.00 0.48 2.46

Size-TSP 0.29 0.23 0.08 4.53 0.46 2.52

Size-TSP 0.87 0.39 0.09 4.73 0.53 3.12

Size-TSP 0.29 0.24 0.06 3.58 0.31 1.32

Size-TSP 0.91 0.58 0.12 5.44 1.07 1.78

1.0

Na+

K+

.458

1.0

.835

.626

.414

1.0

.758

.952

.943

.719

1.0

-.044

.304

.142

-.011

.262

.073

.064

.615

.233

-.06

.182

.895

.679

.832

-.25

-.02

.861 -.026

.971 -.260

.897

-.052

-.368

.530

.038

Pb

.15 -.252 Size-TSP

201.02 11.35 481.93 371.84 149.23 14.18 553.18 153.79 287.01 7.65 438.16 100.61 282.88 6.42 631.48 397.05

SizeTSP 114.73 9.41 364.07 196.71

1.0

Size-TSP

.666

Size-TSP

1.0

Size-TSP

.155

.425

.345

.528

Mirpur

.368

.633

.187

.921

Mohakhali

1.0

-.135

.173

.188

.097 -.157 -.026

.096

-.097 -.044 -.009

.238

.607

.665

Farmgate

Cu

.248

.140

Dhanmondi

Zn

.556

.15

Cu

.009 -.416

.445

.63

Zn

.050 -.039

-.102

.389

-.14

-.441

.783

Cd

Location Curzon Hall

Cd

1.0

1.0

.892

.748

-042

.344

.422

.39

NO3- SO42-

Pb

1.0

.884

.230

.221 -.093

.278

.149 -.189

Cl-

-.378 -.684 -.213

.071

.397

-.268

Mg2+ Ca2+

1.0 -.161

1.0

.128 -.052

-.39 -.358

.733

-.202 -.164

NH4+

SO42-

NO3-

Cl-

Ca2+

Mg2+

K+

NH4+

1.0 -.389

CC

.052

1.0 -.364 -.176

1.0 -.090 -.219

Na+

EC

OC

CC

Pb Cd Zn Cu

EC

Parameter

OC

Table 4.1.4. Correlation between the measured aerosol components in Dhaka city, Bangladesh (r2 > 0.65 in bold)

SO421.86 2.42 1.57 3.09 4.02 Table 4.1.3. Trace elements in the air sample of Dhaka city. All units are in ng/m 3.

1.48

Mohammad pur Size-TSP

102.82 4.48 308.30 72.29

4.2. General Characteristics of Soil The soil samples were collected from six locations of Dhaka city. They were analyzed for their physical, physico-chemical properties and trace element contents, in order to characterize them. The results of the physical, physic-chemical properties and trace element contents of the soils are presented in Table 4.2.1, 4.2.2 and 4.2.3.

4.2.1. Textural class The Textural classes and the particle size distribution of the collected soils are shown in Table 4.2.1.

In urban Dhaka, the textural classes of soils collected from Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were silty Clay loam, silty clay loam, silty clay, silty clay loam, silty clay loam and silty clay loam respectively. Sand, Silt and Clay contents in the soils of urban Dhaka ranged from 2.72-46.01%, 20.02-54.55% and 33.97-50.54%, respectively.

The textural classes influenced the moisture contents of the soils. Silty clay loam to silt loam showed the higher moisture content (MC).

4.2.2. Electrical Conductivity (EC) The EC values of soil samples were presented in Table 4.2.1. The EC values of the soils varied from 78.3 to 221.0 μS. The highest value was observed at Mohakhali (221 μS) and the lowest at Farmgate (78.3 μS). These values indicate that the soils are non –saline in character.

4.2.3. pH pH of the soils of six areas of Dhaka city was found to be moderately acidic to alkaline (6.37-8.17.

The highest pH value was found at Mohakhali (8.17).

4.2.4. Organic Carbon The values of organic carbon (OC) of the soil samples were presented in Table 4.2.2. The OC values of the soils varied from .39% to 1.11%. The highest value was observed at Curzon Hall (1.11%) and the lowest at Dhanmondi (0.39%). These values indicate that the decomposition of organic matter is very low in those soils.

4.2.5. Organic Matter The values of organic matter (OM) of the soil samples were presented in Table 4.2.2. The OM values of the soils varied from 0.67% to 1.92%. The highest value was observed at Curzon Hall (1.92%) and the lowest at Dhanmondi (0.67%). These values indicate that the accumulation of organic matter is very low in those soils.

Table 4.2.1. Electrical conductivity (EC), Moisture content and particle size distribution of the investigated soils.

Location

Curzon Hall Dhanmondi Farmgate Mohakhali Mirpur Mohammadpur

Parameter EC Moisture (ÎźS) Content (%) 106.6 21.20 82.50 20.27 78.3 16.86 221.0 12.82 120.3 18.32 108.0 25.6

Particle Size Analysis Sand (%) Silt (%) 8.18 46.01 2.72 17.35 10.57 10.05

54.55 20.02 46.74 47.96 52.50 52.42

Textural Class Clay (%) 37.27 33.97 50.54 34.69 36.93 37.53

Table 4.2.2. Some Physico-chemical properties of the soil Location Curzon Hall Dhanmondi Farmgate Mohakhali Mirpur Mohammadpur

Parameter pH 6.37 7.51 6.52 8.17 6.45 6.67

4.2.6. Trace Element Content of the Soil a)Lead

OC (%) 1.11 0.39 1.08 1.02 0.63 0.39

OM (%) 1.92 0.67 1.86 1.76 1.09 0.67

Silty Clay loam Silty Clay loam Silty Clay Silty Clay loam Silty Clay loam Silty Clay loam

Lead contents in the soil are shown in Table 4.2.3. In Dhaka, the Pb contents in the soils of Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were 23.6, 9.45, 15.83, 5.79, 11.68 and 13.69 mg/kg, respectively. The highest value of lead was found at Curzon Hall.

Such high concentrations of lead in the six areas of Dhaka were due to the emission of lead from fossil fuel burning particularly from vehicles of the city. All these values of lead in soils are well below the permissible limit of 100 mg/kg.

b) Cadmium The Cd contents in the soils of Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were 0.1, 0.25, 0.23, 0.41, 0.27 and 0.21 mg/kg, respectively (Table 4.2.3). The highest value of Cd was found at Mohakhali.

c) Zinc The Zn contents in the soils of Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were 38.69, 56.02, 27.25, 42.4, 31.47 and 48.02mg/kg, respectively (Table 4.2.3). The highest value of zinc was found at Dhanmondi. d) Copper Copper contents in the soil are shown in Table 4.2.3. In Dhaka, the Cu contents in the soils of Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were 23.83, 15.40, 13.83, 4.37, 12.32 and 18.67 mg/kg, respectively. The highest value of copper was found at Curzon Hall.

Table 4.2.3. Contents of Pb, Cd, Zn and Cu (mg/kg) in the investigated soils Location Curzon Hall Dhanmondi Farmgate Mohakhali Mirpur Mohammadpur

Parameter Pb 23.6 9.75 15.83 5.79 11.68 13.69

Cd 0.1 0.25 0.23 0.41 0.27 0.21

Zn 38.69 56.02 27.25 42.4 31.47 48.02

Cu 23.83 15.40 13.83 4.37 12.32 18.67

4.3. Trace Element Contents of Plant Naturally growing plant samples (grass: Poa bulbosa) were collected from six different sites. The results of the trace element contents of the investigated plant samples are presented in Table 4.3.1. a)Lead

Lead contents in the grass of six locations are shown in Table 4.3.1. In Dhaka, the Pb contents in the grass of Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were 0.010, 0.102, 0.158, 0.063, 0.160 and 0.130 mg/kg, respectively. The highest value of lead was found at the grass of Mirpur.

b) Cadmium The Cd contents in the grass of Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were 1.01, 1.20, 1.25, 1.76, 1.29 and 1.17 mg/kg, respectively (Table 4.3.1). The highest value of Cd was found at Mohakhali.

c) Zinc The Zn contents of the grass of Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were 47.85, 48.83, 78.92, 35.09, 39.35 and 41.09 mg/kg, respectively (Table 4.3.1).

The highest value of zinc was found at Farmgate. d) Copper Copper contents of the grass of six locations are shown in Table 4.3.1. In Dhaka, the Cu contents in the grass of Curzon Hall, Dhanmondi, Farmgate, Mohakhali, Mirpur and Mohammadpur were 9.60, 3.12, 13.25, 3.56, 9.50 and 7.43 mg/kg, respectively. The highest value of copper was found at Farmgate.

Table 4.2.4. Contents of Pb, Cd, Zn and Cu (mg/kg) in grass Location Curzon Hall Dhanmondi Farmgate Mohakhali Mirpur Mohammadpur

Parameter Pb 0.010 0.102 0.158 0.063 0.16 0.13

Cd 1.01 1.20 1.25 1.76 1.29 1.17

Zn 47.85 48.83 78.92 35.09 39.35 41.09

Cu 9.60 3.12 13.25 3.56 9.50 7.43

4.4. Trace Element Contents of Human Blood Sample a) Lead Lead contents of the blood of six Traffic police working at the six sampling sites are shown in Table 4.4.1. In Dhaka, the Pb contents in the blood samples from six representative persons were 0.00ng/cc.

b) Cadmium Cadmium contents of the blood of six Traffic police working at the six sampling sites are shown in Table 4.4.1. In Dhaka, the Cd contents in the blood samples from six representative persons were 40.00, 40.02, 41.00, 40.01, 44.00 and 39.89ng/cc, respectively.

c) Zinc Zinc contents of the blood of six Traffic police working at the six sampling sites are shown in Table 4.4.1. In Dhaka, the Zn contents in the blood samples from six representative persons were 4.399, 4.563, 4.691, 5.293, 5.032, 4.721 ng/cc, respectively. d) Copper Copper contents of the blood of six Traffic police working at the six sampling sites are shown in Table 4.4.1. In Dhaka, the Cu contents in the blood samples from six representative persons were 490,570, 620, 650, 540 and 470ng/cc, respectively.

Table 4.2.5. Contents of Pb, Cd, Zn and Cu (ng/cc) in Human Blood Location Curzon Hall Dhanmondi Farmgate Mohakhali Mirpur Mohammadpur

Parameter Pb 0.00 0.00 0.00 0.00 0.00 0.00

Cd 40.00 40.02 41.00 40.01 40.00 39.89

Zn 4.399 4.563 4.691 5.293 5.032 4.721

Cu 490 570 620 650 540 470

4.5. Discussions

4.5.1. Comparison of Trace Element Contents in Soil, Plant and Human with that of Air

a)

Lead (Pb)

In the present study it was observed that concentrations of Pb in soils along the roadsides of the urban of Dhaka varied from 9.75-23.6 mg/kg (Table 4.2.3 and Fig. 4.1 â&#x20AC;&#x201C; 4.45). In urban areas of Dhaka, the higher contents of Pb were found at Curzon Hall and the lower at Mohakhali. As the average concentration of Pb in soil is 0.1 â&#x20AC;&#x201C; 20 mg/kg (Sauerbeck, 1985). It indicated that the collected soil samples were not contaminated due to Pb, except Curzon Hall. Among the sampling sites, Curzon Hall showed the higherst level of Pb followed by Farmage. Considereing Pb accumulation in soils, the

following sequence of Pb pollution was observed: Curzon Hall > Farmgate > Mohammadpur>Mirpur > Dhanmondi >Mohakhali.

As the highest numbers of automobiles (Truck, bus, taxi et.) moved through the Curzon Hall and Farmgate of Dhaka city, the soils of the at sites were highly contaminated and as the less number of motor vehicles is used in Dhanmondi and Mohammadpur route the soils of these areas were found to be least contaminated. But one of the exception was Mohakhali, this may be due to experimental error. Davison and Osborn (1986) mentioned that, the transport of Pb, As and Cd depends on their physical â&#x20AC;&#x201C; Chemical prosperities, the particle size distribution and meterological conditions such as rate of turbulent, vertical air exchange and wind speed and the former two parameters are dominant in the long range transport of Pb, As and Cd. Rahn, (1976) mentioned that the residence time of Pb, As and Cd in the atmosphere are found to be about 7 days, which is sufficient for transport over thousands of kilometers.

When plant samples were analysed for Pb content, the concentrations of the metal varied from 0.010 Pb concentrations in Air (mg/m3), Soil (mg/kg), Plant (mg/kg) and Human Blood (mg/cc)

to 0.16 mg/kg (Tables 4.2.3 and Figure 4.1), whereas the average concentration of Pb in plant samples is 0.1 â&#x20AC;&#x201C; 2.0 mg/kg (Sauerbeck, 1985). It was found that all the plant accumulated concentration of Pb within the permissible limit.

Again, in case of blood sample no Pb was determined, indication no contamination due to lead. The comparison of lead content in soil, plant and blood sample with that of air is shown in figure 4.1.

M oh ak hal Mi i rp M ur oh am ma dp ur

Far mga te

Dha nm ondi

HAll

Curzon Hall

Figure 4.1. Concentration of Pb in Air, Soil, Plant and Human Blood.

Location

The regression analysis of the concentrations of Pb in soil, plant and human blood with air are shown in Figure 4.2, 4.3 and 4.4. These statistical analysis shows that in every case the values are scatteredly

Soil Pb (mg/kg)

distributed. Some are only closely related to the linear lines.

Air Pb (ng/m3)

Plant Pb

Figure 4.2. Regression analysis of soil Pb on air Pb.

b) Cadmium (Cd) The concentrations of Cd in soils collected from the six sites of Dhaka varied from 0.1 to 0.41 27

Air Pb

mg/kg (Table 4.2.3 and Fig. 4.4), whereas the average concentration of Cd in soil is 14 mg/kg

4.3. .ofRegression of plant (Sauerbeck, 1985).Figure In six sites Dhaka city,analysis all the soils from every site has Cd content within the Pb on air Pb.

range. The Cd concentration was higher in soils of Mohakhali due to heavy traffic passing through the area. It also indicated that motor wastes and fumes play a vital reole in adding Cd to the soils.

Lagerweff and Specht (1970) mentioned that, Zn and Cd might also be added to soils adjacent to highways and the sources being tyres and lubricants. Ardakani (1984) stated that, Zinc and Cadmium

are added to lubricating oils and also present in tyers and gavvanized parts of the vehicles.

Sanchidrian and Marino ( 1980) mentioned that there was high degree of heavy metals such as Cd, Pb, Zn and Cr contamination of soils surrounding six motorways in Madrid and it was assumed that motor exhausts was the source of these metals. Considering Cd accumulation in soils, the following sequences of Cd pollution intensity was observed.

Mohakhali > Mirpur > Dhanmondi> Farmgate> Mohammadpur> Curzon Hall.

The Cd concentration in the plant samples collected from the six sites of Dhaka city varied from 1.01 to 1.76 mg/kg (Tables 4.2.4. and Fig 4.4) whereas , the average concentration of Zn in plant sample is 20 â&#x20AC;&#x201C; 100 mg/kg (Sauerbeck, 1985). In some spots, it accumulated in the normal range. It was found that difgference in Zn accumulation by the same plant species form one spot to another could be related to the soil condition collected from the roadside which was influenced by automobile exhausts and spillage being continuously added to the soils and on the plants foliages. Fytianos et at., (1985) observed contamination of roadside vegetation with Zn and Cd in Thessaloniki area in Greece. Das et al., (1989) found significantly higher contents of Zn along with Pb, Cu, Cd and Fe in the plants exposed to vehicle pollution than in control nursery plants. Moreover, Maskina and Randhawa (19893) stated that poultry manure, farmyard manure and other organic manure increased the Zn concentration in plant. Atmospheric transport of air borne Zn particles exhausted from motor vehicles and their deposition on plant surface might be the cause of this high Zn concentration. Moreover, agricultural inputs such as might contribute to high Zn content in soils, which was taken up by plants entering fertilizers, pesticides and farmyard manure, etc. into food chain and polluting the environment.

c) Zinc (Zn) Soil samples collected from the different spots at urban and rural areas Dhaka division and Bhola (Island), which analyzed for Fe and its concentration in soil varied from 202250 to 35000 mg/kg (Table 4.3.3 and Fig. 4.3 – 4.45) whereas the normal concentration of Fe in soil is 7000 – 55000 mg/kg (Bowen, 1966). It was found that the collected soils contained Fe within normal range.

In urban areas of Dhaka, Farmgate showed the highest level of Fe followed by Science laboratory crossing. Considering Fe accumulation in soils, the following sequence of Fe pollution was observed.

Farmgate > Science laboratory crossing > Shahbagh crossing > Nilkhet > Mohammadpur.

Rural areas Dhaka division showed that the concentrations of Fe varied from 28375 to 34375 mg/kg soil and the highest value was observed at Bhola (35000 mg/kg soil, Table 4.3.3 and Fig. 4.3 – 4.45).

The Fe content was higher in agricultural soils. The highest value was observed in agricultural soils of Bhola, which indicated that fertilizers, pesticides and organic manure, etc. contribute a high content of Fe to the soil. On the other hand, rural areas of Dhaka division also showed higher Fe concentration than the normal roadside of urban areas of Dhaka that might be due to the addition of sewage sludge, garbage, etc. containing high amounts of Fe. The following sequence of Fe contamination in soil was observed: Bhola > Manikgonj > Munshigonj > Zinzera > Sonargoan.

Plant samples were investigated for heavy metals. It was found that Fe content in plant did not follow any definite pattern. It varied form 75 – 1085 mg/kg (Tables 4.4.2 – 4.11.2 and Fig. 4.3 – 4.45) plant, whereas the average concentration of Fe in plant is 140 mg/kg (Allaway, 1970). As Fe chelates with organic matter, becomes available to plant. Plants growing on high Fe and organic matter containing soils take up higher amounts of Fe into plants might have often – interfere with plant biochemistry.

Moreover, consumption of plants with such high Fe might have adverse effect on animal and human begins. It was observed that almost all the concentrations were above the normal range of plant. The accumulation of this heavy metal in plant is regulated by plant is regulated by plant through some mechanisms, which were dependent on the plant species or variety. The difference in accumulation of Fe by the same species form one spot to another could be related variations in soil conditions, plant growth stages and plant parts. Das et al., (1989) showed that, significantly higher content of Pb, Zn and Fe were found in the plants exposed to vehicle pollution than in control nursery plants. They also mentioned that leaves accumulated more of these heavy metals than other plant parts.

d) Cupper (Cu) Soil samples collected from the different spots at urban and rural areas Dhaka division and Bhola (Island), which analyzed for Fe and its concentration in soil varied from 202250 to 35000 mg/kg

(Table 4.3.3 and Fig. 4.3 – 4.45) whereas the normal concentration of Fe in soil is 7000 – 55000 mg/kg (Bowen, 1966). It was found that the collected soils contained Fe within normal range.

In urban areas of Dhaka, Farmgate showed the highest level of Fe followed by Science laboratory crossing. Considering Fe accumulation in soils, the following sequence of Fe pollution was observed.

Farmgate > Science laboratory crossing > Shahbagh crossing > Nilkhet > Mohammadpur.

Rural areas Dhaka division showed that the concentrations of Fe varied from 28375 to 34375 mg/kg soil and the highest value was observed at Bhola (35000 mg/kg soil, Table 4.3.3 and Fig. 4.3 – 4.45).

The Fe content was higher in agricultural soils. The highest value was observed in agricultural soils of Bhola, which indicated that fertilizers, pesticides and organic manure, etc. contribute a high content of Fe to the soil. On the other hand, rural areas of Dhaka division also showed higher Fe concentration than the normal roadside of urban areas of Dhaka that might be due to the addition of sewage sludge, garbage, etc. containing high amounts of Fe. The following sequence of Fe contamination in soil was observed: Bhola > Manikgonj > Munshigonj > Zinzera > Sonargoan.

Plant samples were investigated for heavy metals. It was found that Fe content in plant did not follow any definite pattern. It varied form 75 – 1085 mg/kg (Tables 4.4.2 – 4.11.2 and Fig. 4.3 – 4.45) plant, whereas the average concentration of Fe in plant is 140 mg/kg (Allaway, 1970). As Fe chelates with organic matter, becomes available to plant. Plants growing on high Fe and organic matter containing soils take up higher amounts of Fe into plants might have often – interfere with plant biochemistry.

Moreover, consumption of plants with such high Fe might have adverse effect on animal and human begins. It was observed that almost all the concentrations were above the normal range of plant. The accumulation of this heavy metal in plant is regulated by plant is regulated by plant through some mechanisms, which were dependent on the plant species or variety. The difference in accumulation of Fe by the same species form one spot to another could be related variations in soil conditions, plant growth stages and plant parts. Das et al., (1989) showed that, significantly higher content of Pb, Zn and Fe were found in the plants exposed to vehicle pollution than in control nursery plants. They also mentioned that leaves accumulated more of these heavy metals than other plant parts.

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