Environment & Pollution Dept. Applied Ecology—Lecture No.

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Second Stage Instructor: Safa Yaseen

ENVIRONMENTAL FACTORS

Conditions that are not under the control of human and influence many
human activities. Environmental factors make up the physical, social and
attitudinal environment in which people live and conduct their lives.
Environmental factors are external to the individual and can have a positive
or negative influence on a person's participation as a member of society, on
performance of activities, or on a person's body function or structure. Those
factors include Social, Economic, Cultural, Geographical, Technological,
Political, Legal, and Ecological factors.

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 Environmental factors can be classified as three chief types: Physical,
Chemical, and Biological.

1- Physical Factors: include many elements like temperature, light,

moisture, pressure, rain, wind …etc.
2- Chemical Factors: include hydrogen ion (pH), salinity, nutrients,
oxidation and reduction … etc.
3- Biological Factors: include all living organisms with all their
different relations like predations, parasitism, cooperation, mutual
benefit, coexistence …etc.

Moisture & Humidity

Moisture content is, simply, how much water is in a product. It influences

the physical properties of a substance, including weight, density, viscosity,
conductivity, and others. It is generally determined by weight loss upon
drying.

Humidity is the amount of water vapor in the air. If there is a lot of water
vapor in the air, the humidity will be high. The higher humidity, the wetter it
feels outside. The percentage or amount of humidity in the air varies
depending on the temperature and air pressure . It is directly proportional to
the temperature.

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Humidity is divided into two parts:

Absolute humidity: it is the weight or

amount of water vapor present in a
volume of air at a certain temperature,
and it is measured in units of gm/m3.

Relative humidity: it is the weight of

water vapor in the air divided by the
weight of water vapor in the same
volume of air when it is in a state of
saturation , expressed as a percentage of
the maximum amount of water vapor the
air can hold at the same temperature
(what its units?)

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 Example// Think of the air at a chilly -10 degrees Celsius (14 degrees
Fahrenheit). At that temperature, the air can hold, at most, 2.2 grams of water per
cubic meter. So if there are 2.2 grams of water per cubic meter when its -10 degrees
Celsius outside, we're at an uncomfortable 100 percent relative humidity. If there
was 1.1 grams of water in the air at -10 degrees Celsius, we're at 50 percent relative
humidity.

Humidity is blamed for all kinds of negative things, including mold in your
house (usually the bathroom, where its wet a lot of the time), as well as
malfunctions in regular household electronics. High humidity is also
associated with hurricanes. Air with high moisture content is necessary for a
hurricane to develop.

Air Movement

Air is a fluid, just like water. It will also flow from one area to another.

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What causes air movement and forms the natural ventilation
system for the earth?

In general, air movement results from differences in pressure. Air moves

from high pressure areas to low pressure areas. This difference in pressure is
the result of thermal conditions. We know that hot air rises. Hot air rises
because air expands as it is heated and thus becomes lighter. The air rises and
is replaced by air from a higher pressure area. Thus, convection currents
cause a natural ventilation effect through the resulting winds. The higher the
difference in pressure, the greater quantity of air will flow in a given period
of time.

Day Lighting

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 The primary source of light for day lighting is the sun. Nuclear fusion
reaction at the sun's core converts hydrogen to helium. A nuclear fusion
releases a tremendous amount of thermal energy according to Einstein’s
formula: E=Mc2

The radiation from the inner core is not visible since it is absorbed by a layer
of hydrogen atoms closer to the sun's surface. As sunlight enters the earth‟s
atmosphere, some of it gets absorbed, some is scattered and some passes
through and reaches the earth‟s surface. Different molecules in the
atmosphere absorb significant amounts of sunlight at certain wavelengths.

–Water vapor and carbon dioxide absorb sunlight in the visible and
infrared region
– Ozone absorbs sunlight in the UV region

Irradiance and Irradiation

Irradiance is power density of Irradiation is a measure of energy

sunlight (W/m2). Often referred to as density of sunlight (kWh/m2). It is
intensity of sunlight. the integral of irradiance over a
period of time (usually 1 day).

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Types of Radiation

• Scattered sunlight (what makes the sky blue) is responsible for the light
entering the north facing windows. It is referred to as diffuse radiation.

• Direct or beam radiation is sunlight that reaches the earth‟s surface

without scattering as absorbed radiation.

• Sunlight that is reflected from the ground is called albedo radiation.

• The sum of the all three components above is called global radiation.

The most important benefit of using daylight is that it can illuminate a large
portion of the interior in a uniform way, without any energy consumption.
Sunlight kills many microbes and bacteria, keeping the indoor environment
fresh, healthy and cheerful. Using daylight reduces a lot of cost that is usually
spent on artificial lighting.
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Heat & Sound

Temperature : It has a direct relationship with all other factors. It is

defined as the energy associated with sunlight. The sun is the main source of
heat on the surface of the earth, as well as chemical reactions and heat of the
Earth's interior, volcanoes and others. Temperature is measured in units of
degrees Celsius (Cᵒ), Fahrenheit (ᵒF) and Kelvin (K).

K= ᵒC +273.15
ᵒF= (ᵒC*9/5)+ 32
K=(ᵒF+ 459.67)*5/9

The Body’s Response to Heat and Cold

Your body works best when it has an internal “core” temperature of 37°C.
37°C might seem warm, but this is your internal temperature (not the air
temperature). This temperature is necessary for your vital organs to function
normally.

During a regular day, your body temperature may vary by about 1°C
depending on the time of day, your level of physical activity and how you are
feeling (emotional reactions). The body‟s metabolic processes produce the
right amount of heat you need when you digest your food and when you
perform physical activity.

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Maintaining Balance

When you work in extreme temperatures, your body has to adapt. To

maintain a constant inner body temperature, the body must continually keep
or gain heat in cold environments and lose heat in hot environments.

To stay warm in cold environments, the body:

• Shivers – moving muscles help increase heat production, and

• Reduces blood flow to the skin and extremities (hands and feet) to reduce
heat loss from the surface.

To stay cool in hot environments, the body:

• Sweats – evaporating sweat cools the body, and

• Increases blood flow to the skin – to speed up the loss of heat from the
skin (radiate away the excess heat) if the outside air is cooler.

By sweating, shivering, and changing the rate of blood flow, the body can
adapt to a fairly wide range of temperatures. However, there are limits to
what the body can adapt to and its ability to maintain its core temperature can
fail.

The Wet‐Bulb Globe Temperature (WBGT)

Is a type of apparent temperature used to estimate the effect of temperature,

humidity, wind speed (wind chill), and visible and infrared radiation (usually
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sunlight) on humans. It is used by industrial hygienists, athletes, and the
military to determine appropriate exposure levels to high temperatures. It is
derived from the following formula:

For outdoors with a solar load, WBGT is calculated as:

WBGTout = 0.7 Tnwb + 0.2 Tg + 0.1 Tdb

where:
WBGT = Wet Bulb Globe Temperature Index
Tnwb = Natural Wet‐Bulb Temperature
Tdb = Dry‐Bulb Temperature
Tg= Globe Temperature

Example:
Suppose it‟s a bright sunny day and a crew of roofers is working 20 feet
above ground. Our assessment yields the following readings:
Wet bulb temperature(cooling effects of evaporation) = 20°C
Black bulb globe temperature (radiant heat) = 36°C
Dry bulb temperature (air temperature) = 33°C
Using the formula for work in direct sunlight, we calculate as follows:

WBGT = 0.7 Tnwb + 0.2 Tg + 0.1 Tdb

= (0.7 x 20) + (0.2 x 36) + (0.1 x 33)
= 14 + 7.2 + 3.3
WBGT (outdoors) = 24.5 °C
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Indoors, or when solar radiation is negligible, the following formula is often
used:
Using the formula for work indoors, we calculate as follows:

WBGTin= 0.7 Tnwb + 0.3 Tg

WBGT = 0.7 Tnwb + 0.3 Tg

= (0.7 x 23) + (0.3 x 37) = 27.2°C
WBGT (indoors) = 27.2°

Example:
An athlete is sitting unclothed in a locker room whose dark walls are at a
temperature of 15°C. Estimate his rate of heat loss by radiation, assuming a
skin temperature of 34°C and ε= 0.70.Take the surface area of the body not in
contact with the chair to be 1.5 m2.

Solution:
Let T1 = 34ᵒC= 307K, T2 = 15ᵒC= 288K , ϭ=5.67*10-8 W/m2.K4
∆Ǫ
= 𝝐 б 𝑨 (T14- T24)
∆𝒕
= (0.70) (5.67x10-8 W/m2 .K4) (1.5m2) (344- 154) = 120 W

This is greater than the ~100W that a resting person generates, so athlete
loses heat quickly

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 Sound

Everyday we hear sounds from various sources like humans, birds,

bells, machines, vehicles, televisions, radios etc. Sound is a form of energy
which produces a sensation of hearing in our ears. There are also other forms
of energy like mechanical energy, heat energy, light energy etc. Sound is
produced by vibrating objects. The matter or substance through which sound
is transmitted is called a medium. It can be solid, liquid or gas. The speed of
sound depends primarily on the nature and the temperature of the
transmitting medium.

We can describe a sound wave by its frequency, amplitude and

speed.
The speed of sound is defined as the distance which a point on a wave, such
as a compression or a rarefaction, travels per unit time. For hearing a distinct
sound, the time interval between the original sound and the reflected one
must be at least 0.1 s.

We know, speed, ʋ = distance (d) / time (t)

Here λ is the wavelength of the sound wave. It is the distance travelled by the
sound wave in one time period (T) of the wave. Thus, ʋ = λ ν

Since frequency=1\t »»» ʋ = λ ν

Example: A sound wave has a frequency of 2 kHz and wave length 35 cm.
How long will it take to travel 1.5 km?
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Solution: Given, Frequency, ν = 2 kHz = 2000 Hz , Wavelength, λ = 35 cm =
0.35 m

ʋ of the wave = λ ν
= 0.35 m × 2000 Hz = 700 m/s

• The persistence of sound in an auditorium is the result of repeated

reflections of sound and is called reverberation.
• Loudness is a physiological response of the ear to the intensity of sound.
• The amount of sound energy passing each second through unit area is called
the intensity of sound.
The audible range of sound for human beings extends from about 20 Hz to
20000 Hz. Children under the age of five and some animals, such as dogs can
hear up to 25 kHz (1 kHz = 1000 Hz). As people grow older their ears
become less sensitive to higher frequencies. Sounds of frequencies below 20
Hz are called infrasonic sound or infrasound.

Frequencies higher than 20 kHz are called ultrasonic sound or ultrasound.

Ultrasound is produced by dolphins, bats and porpoises. Moths of certain
families have very sensitive hearing equipment. These moths can hear the
high frequency squeaks of the bat and know when a bat is flying nearby, and
are able to escape capture. Rats also play games by producing ultrasound

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Ultrasound has many medical and industrial applications:
 generally used to clean parts located in hard-to-reach places, for
example, spiral tube, odd shaped parts, electronic components, etc.
 can be used to detect cracks and flaws in metal blocks.
 may be employed to break small „stones‟ formed in the kidneys into
fine grains.
 The SONAR technique is used to determine the depth of the sea and to
locate under water hills, valleys, submarines, icebergs, sunken ships,
etc.

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