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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
colloidal-sized 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?

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

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 .

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 SiO₂, Al₂O₃
and Fe₂O_3, 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	Emission (106 tons per year)
Sea-salt aerosol	500-2000
Dust aerosol	7-1800
Biological aerosol	80
Smoke from forest fires	5-150
Volcanic aerosol	4-90
Anthropogenic aerosol	181-396

Modes of urban aerosol	Sources	Characterization
Nuclei Mode	Combustion particles; gas-to-particle conversion	0.001-0.1 ?m; high concentration; rapid coagulation; short lifetime
Accumulation Mode	Combustion particles; smog particles; coagulated nuclei-mode particles	0.1-2.5 ?m; slow coagulation; long lifetime; accounting for most of visibility effects
Coarse Particle Mode	Windblown dusts; salt particles from sea spray; volcanic eruption anthropogenic particles from agriculture and surface mining	2.5-100 ?m; readily settle down on surface; short lifetime

	Urban
	Fine	Coarse
Total Mass	42	27
SO42-	17	1.1
NO3–	0.25	1.8
NH4+	4.3	<0.19
H+	0.067	<0.01
C	7.6	3.3
Al	0.095	1.4
Si	0.2	3.8
S	–	–
Ca	0.15	3.1
Fe	0.17	0.73
Pb	0.48	0.13

3.4.2.
Processing of Soil Sample

3.4.3.
Processing of Plant Sample

b)
 Elemental Carbon (EC)

 

c)
 Organic Carbon (OC)

 

Organic carbon was determined by Sunset OC/EC
analyzer and for the analysis NIOSH protocol was used.

 

f)
Trace
Elements (Pb, Cd, Zn and Cu)

 

b)
Electrical Conductivity (EC)

c)
Organic Carbon (OC)

d)
Extractable Heavy metals (Pb, Cd, Zn and Cu)

3.5.3. Analysis of Plant Sample

 

a)
Heavy Metals (Pb, Cd, Zn and Cu)

 

4. Results and Discussion

4.1.
Analyses Result of Aerosol Sample

4.1.1.
Elemental carbon

4.1.5.
Trace Elements

Parameter	Location
	Curzon Hall	Dhanmondi	Farmgate	Mohakhali	Mirpur	Mohammadpur
	Size- TSP	Size-TSP	Size-TSP	Size-TSP	Size-TSP	Size-TSP
OC	3.32	5.43	3.39	10.36	5.5	3.46
EC	0.35	0.36	0.29	0.78	0.51	0.47
CC	0.02	0.08	0.35	0.07	0.04	0.04
TC	3.69	5.87	4.03	11.21	6.05	3.97
OC (%)	82.73	90.1	88.8	88.23	87.72	81.25
EC (%)	16.48	8.75	9.95	11.12	11.1	11.80
CC (%)	0.79	1.15	1.25	0.65	1.18	0.95
Na+	0.9	0.18	0.14	0.24	0.29	0.11

Parameter	Location
	Curzon Hall	Dhanmondi	Farmgate	Mohakhali	Mirpur	Mohammadpur
	Size-TSP	Size-TSP	Size-TSP	Size-TSP	Size-TSP	Size-TSP
NH4+	0.48	0.32	0.29	0.87	0.91	0.29
K+	0.26	0.29	0.23	0.39	0.58	0.24
Mg2+	0.05	0.07	0.08	0.09	0.12	0.06
Ca2+	2.54	5.00	4.53	4.73	5.44	3.58
Cl–	0.29	0.48	0.46	0.53	1.07	0.31
NO3–	2.08	2.46	2.52	3.12	1.78	1.32
SO42-	1.86	2.42	1.57	3.09	4.02	1.48

Parameter	Location
	Curzon Hall	Dhanmondi	Farmgate	Mohakhali	Mirpur	Mohammadpur
	Size-TSP	Size-TSP	Size-TSP	Size-TSP	Size-TSP	Size-TSP
Pb	201.02	149.23	287.01	282.88	114.73	102.82
Cd	11.35	14.18	7.65	6.42	9.41	4.48
Zn	481.93	553.18	438.16	631.48	364.07	308.30
Cu	371.84	153.79	100.61	397.05	196.71	72.29

Cu	.15	.556	-.416	.665	.607	.238	-.009	-.252	-.026	.528	.345	.425	.155	.666	1.0
Zn	.63	.445	.009	.140	.248	-.039	-.044	.15	-.157	.921	.187	.633	.368	1.0
Cd	.783	-.441	-.14	.389	-.102	.050	-.097	.096	.097	.188	.173	-.135	1.0
Pb	-.06	.233	.615	.064	.073	-.260	-.026	-.02	-.25	.832	-.161	1.0
SO42-	.038	.530	-.368	-.052	.897	.971	.861	.679	.895	.182	1.0
NO3–	.39	.422	.344	-042	.262	-.011	.142	.304	-.044	1.0
Cl–	-.189	.230	-.093	-.213	.719	.943	.952	.758	1.0
Ca2+	.149	.278	.221	-.684	.414	.626	.835	1.0
Mg2+	-.268	.397	.071	-.378	.748	.892	1.0
K+	-.164	.458	-.358	-.052	.884	1.0
NH4+	-.202	.733	-.39	.128	1.0
Na+	.052	-.176	-.389	1.0
CC	-.219	-.364	1.0
EC	-.090	1.0
OC	1.0
	OC	EC	CC	Na+	NH4+	K+	Mg2+	Ca2+	Cl–	NO3–	SO42-	Pb	Cd	Zn	Cu

4.2.
General Characteristics of Soil

4.2.1.
Textural class

4.2.2.
Electrical Conductivity (EC)

4.2.3.
pH

Location	Parameter
	EC (?S)	Moisture Content (%)	Particle Size Analysis			Textural Class
			Sand (%)	Silt (%)	Clay (%)
Curzon Hall	106.6	21.20	8.18	54.55	37.27	Silty Clay loam
Dhanmondi	82.50	20.27	46.01	20.02	33.97	Silty Clay loam
Farmgate	78.3	16.86	2.72	46.74	50.54	Silty Clay
Mohakhali	221.0	12.82	17.35	47.96	34.69	Silty Clay loam
Mirpur	120.3	18.32	10.57	52.50	36.93	Silty Clay loam
Mohammadpur	108.0	25.6	10.05	52.42	37.53	Silty Clay loam

Location	Parameter
	pH	OC (%)	OM (%)
Curzon Hall	6.37	1.11	1.92
Dhanmondi	7.51	0.39	0.67
Farmgate	6.52	1.08	1.86
Mohakhali	8.17	1.02	1.76
Mirpur	6.45	0.63	1.09
Mohammadpur	6.67	0.39	0.67

b)
Cadmium

c)
Zinc

Location	Parameter
	Pb	Cd	Zn	Cu
Curzon Hall	23.6	0.1	38.69	23.83
Dhanmondi	9.75	0.25	56.02	15.40
Farmgate	15.83	0.23	27.25	13.83
Mohakhali	5.79	0.41	42.4	4.37
Mirpur	11.68	0.27	31.47	12.32
Mohammadpur	13.69	0.21	48.02	18.67

b)
Cadmium

c)
Zinc

Location	Parameter
	Pb	Cd	Zn	Cu
Curzon Hall	0.010	1.01	47.85	9.60
Dhanmondi	0.102	1.20	48.83	3.12
Farmgate	0.158	1.25	78.92	13.25
Mohakhali	0.063	1.76	35.09	3.56
Mirpur	0.16	1.29	39.35	9.50
Mohammadpur	0.13	1.17	41.09	7.43

4.4.
Trace Element Contents of Human Blood Sample

b)
Cadmium

c)
Zinc

Location	Parameter
	Pb	Cd	Zn	Cu
Curzon Hall	0.00	40.00	4.399	490
Dhanmondi	0.00	40.02	4.563	570
Farmgate	0.00	41.00	4.691	620
Mohakhali	0.00	40.01	5.293	650
Mirpur	0.00	40.00	5.032	540
Mohammadpur	0.00	39.89	4.721	470

4.5.
Discussions

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

a)
Lead
(Pb)

b)
Cadmium
(Cd)

c)
Zinc
(Zn)

d)
Cupper
(Cu)

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 ?g/m³ 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 N-heterocyclic 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

• SO₄^2-: 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 (BéruBé 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 ?g/m3 to 1 mg/m³
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 ?m, usually found near highways and other sources of combustion), accumulation
mode (0.1 ?m< particle size < 2.5 ?m, 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

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/m³ at an
urban site.

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 ?500 and PAR corrected for the
solar zenith angle (? = 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 ?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.

 

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
23º43’33.62” N longitude and 90º24’16.43” 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 twenty-four hours.

 

 

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 polyethylene-buckets, 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 air-sampling 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.

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.

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 1-100?g 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.

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).

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.

The whole PTFE
membrane filters were extracted with 5 ml of 10% HNO₃ (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).

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).

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

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).

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).

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.

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 ?g/m³
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 ?g/m³.

There are no
international air quality standards for elemental carbon. But there is
alternative guideline value of 8 ?g/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 ?g/m³, whereas at large cities in the Indian sub-continent EC
levels were above 10 ?g/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 ?g/m³
(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 ?g/m³.
A value of around 6 ?g/m³ 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 ?g/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 ?g/m³ 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
?g/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

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/m³. Zinc was
correlated with Pb, Cu and NO₃^–.

The copper levels at the urban
areas of Dhaka varied from 72.29-397.05 ?g/m³ 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/m³.

Table 4.1.2. Soluble
ions in the air sample of Dhaka city. All units are in µg/m³.

Table 4.1.3. Trace elements in
the air sample of Dhaka city. All units are in ng/m^3.

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.

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).

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 ?S. The highest value was observed at Mohakhali (221 ?S) and the
lowest at Farmgate (78.3 ?S). These values indicate that the soils are non
–saline in character.

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.

Table 4.2.2. Some
Physico-chemical properties of the soil

4.2.6.
Trace Element Content of the Soil

a)Lead

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.

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.

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

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.

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.

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

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.

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.

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

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 – 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 – 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 – 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 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 – 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.

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

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

 

 

 

 

The concentrations of Cd in soils
collected from the six sites of Dhaka varied from 0.1 to 0.41 27 mg/kg (Table
4.2.3 and Fig. 4.4), whereas the average concentration of Cd in soil is 14
mg/kg (Sauerbeck, 1985). In six sites of Dhaka city, all the soils from every
site has Cd content within the 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 – 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.

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.

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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