DEPARTMENT OF CHEMISTRY,
FEDERAL UNIVERSITY OF
AGRICULTURE, ABEOKUTA.
CHM305: ENVIRONMENTAL
CHEMISTRY (2 UNITS)
• LECTURERS:
• PROF. O. O. ODUKOYA
• DR. (MRS.)T. F. AKINHANMI
COURSE OUTLINE (1)
• Concept of elementary cycles
• Characteristics of the atmosphere
• Sources, types and effects of environmental
pollution
• Water Chemistry
• Composition of domestic wastes
• Water treatment
• Global warming and its effects
• Ozone layer and its functions
• Depletion of ozone layer and its implications
INTRODUCTION
• Environmental Science: study of the earth, air,
water and living environment and the effects
of technology on it.
Comprises the physics, chemistry and biology of
the environment.
Technology and Environmental science
• Technology: Use of automation and machines
Positive and negative effects of technology on the
environment
• Role of environmental science
To minimise damage to environment by allowing
technology to serve environment positively (i.e.
safety of environment for inhabitants)
Environmental Chemistry
• The study of the sources, reactions, transport,
effects and fates of chemical species in water,
soil and air environments and the effect of
technology on them.
The Environment
• Definition: the physical and biological factors
along with their chemical interactions that affect
an organism
• Classification of environment
 Atmosphere
 Hydrosphere
 Geosphere
 Biosphere
Atmosphere
Layer of gases covering the earth surface
Consists of different regions (based on
composition, temp. etc)
Moderates earth’s temperature(absorbs uv
radiation from sun)
Transports energy away from equatorial
regions
Hydrosphere
• Includes earth’s water
Oceans, freshwater (mostly ice form near or at the
poles)
underground water, streams , surface water,
rivers, lakes and ponds
water circulating through environmental
processes and cycles in the atmosphere.
Geosphere
• This is solid earth including soil supporting
plant life.
• Parts of the geosphere:
 Lithosphere - Involved with environmental
processes through contact with other parts of the
environment
 Crust - thin outer skin consisting of lighter silicate
minerals.
Biosphere
• Refers to all living organisms
Living organisms and the portions relating to them
are called BIOTIC
the non living portions are known as ABIOTIC
The section of the environment consisting of
human activities is called ANTHROSPHERE
HUMAN IMPACT AND POLLUTION
Pollution arises from human activities!!!
• POLLUTION: Introduction of waste matter into the
environment by man which causes damage or
deterioration to living systems and for the environment
• POLLUTANT: A substance that is present than its
natural concentration as a result of human activities
and has a detrimental effect on the environment or
hazardous to man (or poses a threat to health and
safety or the quality of life).
HUMAN IMPACT AND POLLUTION…2
• A contaminant is a substance that is present in greater
concentration than its natural concentration as a result of
human activities (causes deviation from normal
composition of an environment)
– it is not a pollutant unless has some detrimental effect
– The toxic or harmful effects from contamination may become
apparent at a later date
– The medium (soil, fish etc) affected by pollutant or contaminant
is called a receptor while the chemical medium or species that
retains or interacts with it is known as sink.
Impact of Technology on the
environment
• Production of pollutants (solids, liquids or gases) can
arise from:
 Industry: Activities involved in the production of large
quantities of industrial products.
 Agriculture: Intensive use of land cultivation, drainage of
wetland, irrigation of arid land, application of fertilizers,
herbicides, pesticides etc
 Oil spillage, Mining
 Extraction and production of mineral and other raw
materials
 Transportation (scarring of road surfaces, emission of air
pollutants
Impact of Technology on the
environment …2
• Intelligent technological applications is a way
to solve environmental problems
Redesign of basic manufacturing processes
(reduces raw material consumption, energy use
and waste production).
Use of computerised control for optimum energy
efficiency, maximum utilization of raw materials
which allows minimum production of pollutants.
TOPIC : ELEMENTARY CYCLES
CARBON CYCLE
NITROGEN CYCLE
OXYGEN CYCLE
PHOSPHOROUS CYCLE
OXYGEN CYCLE
CONCEPTS OF ELEMENTARY CYCLES
Environmental interactions
Every sphere of the environment interact with one
another for survival.
Certain elements are required for the survival of
all living things e.g. C, N, O, P, etc
Each has fixed quantity which are recycled
continuously within and among various
components of the environment
Cycles of matter
• Movement of matter through different
spheres of the environment (Biogeochemical
cycles).
Examples: carbon, nitrogen, sulphur, phosphorous
cycles etc
Biogeochemical cycles can be endogenic or
exogenic
Endogenic and Exogenic cycles
• Endogenic: These are cycles occurring at
different sub surface rocks below the earth’s
surface (e.g. phosphorous cycle)
• Exogenic: occurs on the surface of the earth
(e.g. C, N, S cycles)
THE CARBON CYCLE
• Carbon cycle shows the circulation of carbon in the environment
 Carbon is present in the atmosphere as gaseous CO2 in the
atmosphere and HCO3- and CO2(aq) in surface and ground water
 Occurs as minerals e.g. CaCO3 and MgCO3
 Fossil fuel (coal and petroleum).
 Photosynthesis (green plants) fix carbon as biological/organic carbon
with the aid of solar energy (carbohydrate – CH2O).
 During respiration, carbohydrate reacts with oxygen to produce CO2
which is returned to the atmosphere and energy is released.
CH2O + O2 (g)
→
CO2(g) + H2O + Energy.
THE CARBON CYCLE…2
 Combustion of wood or fossil fuel releases CO2
into the atmosphere.
2CH4 + 4O2 →
2CO2 + 4H2O
 Rock Formation Processes: C fixed in limestone,
oil shale, dolomite are released into the
atmosphere as CO2 when the minerals are broken
down during weathering
 Micro organisms also play an important role in
C – cycle.
CARBON CYCLE
Nitrogen Cycle
• Nitrogen: Essential component of protein.
The atmosphere contains about 78% nitrogen
 Very stable but not available for use directly by
most organisms in the gaseous state.
Can be converted to usable form through nitrogen
fixation which involves biochemical and
atmospheric processes.
Nitrogen Cycle…2
• Biological fixation: This is made possible by
nitrogen fixing bacteria (Rhizobium) occurring
freely in the soil or root of leguminous plants
These bacteria combine nitrogen gas with hydrogen to
produce ammonia.
N2(g) + 3H2(g) →
2NH3(g)
The ammonia produced is further acted upon by another
specialized set of bacteria and converted to nitrates.
Nitrogen Cycle…3
•
Atmospheric Fixation: The electrical energy produced during lightening which
occurs with thunderstorm causes nitrogen to combine with atmospheric oxygen to
produce nitrogen oxides (NOx : NO, NO2 or N2O)
 When rain falls, No2 is dissolved to give nitric acid.
4NO2 +
2H2O
+ O2
→
4HNO3
 The nitrate obtained from both fixation processes are taken up by plant roots and transformed
into a number of organic compounds e.g. protein.
 The nitrogenous organic compound return to the soil when plants and animals die as NH4+ and
nitrate.
3[CH2O] +
2N2 +
NH3 + 3/2O2
NO2- +
½ O2
3H2O + 4H+
→ 3CO2 + 4NH4+
H + + NO2-
→
→
NO3-
+ H2O
Nitrogen Cycle…4
• DENITRIFICATION: Bacteria e.g. bacillus
metabolise nitrogenous compounds with the
assistance of nitrate reductase enzyme to turn
oxides of nitrogen to nitrogen and water.
occurs in deep sub strata of soil or areas of
stagnant water. This process depletes soil fertility.
2NO3- + 10e- + 12H+
→
N2 + 6H2O
OXYGEN CYCLE
• The atmosphere contains 20.8% oxygen.
Oxygen occurs chemically bound to CO2, H2O and
organic matter.
Becomes chemically bound by different energy
yielding processes like combustion and metabolic
processes in organisms.
O2 is released during photosynthesis.
It readily combines with and oxidizes other species
e.g. C in aerobic respiration or combustion of fossil
fuels.
Ozone, an isotope of oxygen in the atmosphere filters
out damaging UV radiation and protects life on earth.
Phosphorous Cycle
• An endogenous cycle
 Soil is the major contributor of phosphorous.
 Phosphorus is taken off from the soil in form of phosphate
(sparingly soluble mineral e.g. Ca3(PO4)2 ) from the root system of
plants and transported to the growing parts of the plants.
 This is then incorporated into a number of organic compounds e.g.
nucleic acids within the growing plants of the plant or animal.
 Mineralization of the biomass by microbial decay returns
phosphorous to salt solution from where it may precipitate
as mineral matter and taken up by plant roots again.
Phosphorous Cycle…2
• An endogenous cycle (Contd.)
 Large quantities of PO43- are extracted from PO43- minerals and
bones to make fertilizers and food additives.
 Phosphorous is a constituent of toxic compounds e.g. PH3–
military nerve gas (tear gas)
 Weathering of phosphorous containing rocks also release
Phosphorous into the environment.
 Dissolved P may sink and be deposited as sediment at the
bottom of ocean and transformed through geological processes
to phosphate rocks.
SULPHUR CYCLE
• Involves several gaseous species, sparingly soluble
minerals and several species in solution (e.g. SO2, H2S)
 Others include SO42-, PbS, H2SO4 (acid rain) and
biologically bound sulphur in proteins.
Cysteine
HSCH2 – CH(NH2) – CO2H
Cystine
CH2S – S – CH2 CH(NH2)CO2H
Methionine
H2SCH2CH2 – CH(NH2) – CO2H
TOPIC:
CHARACTERISTICS OF
THE ATMOSPHERE
OBJECTIVES
• Importance of the Atmosphere
• Physical Characteristics of the Atmosphere
• Stratification of the Atmosphere
• Atmospheric Chemical Processes
BASIC DEFINITION
• The atmosphere of Earth is a layer of gases
surrounding the planet Earth that is retained
by Earth's gravity.
• Atmospheric science deals with:
The movement of air masses in the
atmosphere,
Atmospheric heat balance,
Atmospheric chemical composition and
reactions
Physical Characteristics of the
Atmosphere
Atmospheric Composition
Dry air within several kilometers of ground level consists
 Two major components
• Nitrogen,
78.08 % (by volume)
• Oxygen,
20.95 %
 Two minor components
• Argon,
0.934 %
• Carbon dioxide,
0.036 %
• In addition to argon, four more noble gases,
• Neon,
1.818 x 10-3 %
• Helium,
5.24 x 10-4 %
• Krypton,
1.14 x 10-4 %
• Xenon,
8.7 x 10-6 %
 Trace gases (see table below)
• Atmospheric air may contain 0.1–5 % water by volume,
with a normal range of 1–3 %.
Atmospheric Trace Gases in Dry Air near Ground Level
Stratification of the Atmosphere
• The atmosphere is graded on the basis of:
 The temperature/density relationships
Resulting from
 Interactions between physical and
photochemical
(light-induced
chemical
phenomena) processes in air.
Major regions of the atmosphere
Extends to the far outer
reaches of the atmosphere
Layer above stratosphere,
high levels of radiationabsorbing species are absent
in the mesosphere causing
further temperature decrease
to about -92°C
This is the atmospheric layer
directly
above
the
troposphere in which the
temperature rises to a
maximum of about -2 °C with
increasing altitude.
This is lowest layer of the
atmosphere extending from
sea level to an altitude of 10–
16 km.
Importance of the Atmosphere
• The atmosphere is a protective blanket that
nurtures life on the Earth and protects it from
the hostile environment of outer space.
• The atmosphere is the source of carbon
dioxide for plant photosynthesis and of oxygen
for respiration.
• It provides the nitrogen that nitrogen-fixing
bacteria and ammonia-manufacturing plants
use to produce chemically bound nitrogen, an
essential component of life molecules.
Importance of the Atmosphere
• As a basic part of the hydrologic cycle, the
atmosphere transports water from the oceans
to land, thus acting as the condenser in a vast
solar-powered still.
• The atmosphere serves as a dumping ground
for many pollutant materials—ranging from
sulfur dioxide to refrigerant Freon—a practice
that causes damage to vegetation and
materials, shortens human life, and alters the
characteristics of the atmosphere itself.
Limb view, of the Earth's atmosphere. Colours roughly
denote the layers of the atmosphere.
Atmospheric Chemical Processes
• Atmospheric chemistry involves:
 The unpolluted atmosphere,
 Highly polluted atmospheres,
 and a wide range of gradations in between.
• Two constituents of utmost importance in
atmospheric chemistry are:
 Radiant energy from the sun,
The hydroxyl radical, HO• and NO3 • radicals
Atmospheric cycle
Gaseous atmospheric chemical species
Chemical species fall into the following arbitrary
and overlapping classifications:
1. Inorganic oxides (CO, CO2, NO2, SO2),
2. Oxidants (O3, H2O2, HO. radical, HO2. radical,
ROO. radicals, NO3),
3. Reductants (CO, SO2, H2S),
4. Organics (also reductants; in the unpolluted
atmosphere, CH4 is the predominant organic
species, whereas alkanes, alkenes, and aryl
compounds are common around sources of
organic pollution),
Gaseous atmospheric chemical species
5.Oxidized organic species (carbonyls, organic
nitrates),
6.Photochemically
active
species
(NO2,
formaldehyde),
7. Acids (H2SO4),
8. Bases (NH3),
9. Salts (NH4HSO4,),
10. Unstable reactive species (electronically excited
NO2, HO• radical).
Level of my participation!!!
• What are the Importance of the Atmosphere?
• What are the Major and Minor components of
the Atmosphere?
• The Atmosphere can be stratified according to…
and into how many?
• The Atmospheric Chemical species are…
COURSE: ENVIRONMENTAL
CHEMISTRY (CHM 305)
TOPIC:
SOURCES, TYPES AND
EFFECTS OF
ENVIRONMENTAL
POLLUTION
OBJECTIVES
What are Pollutants?
Main types of environmental pollution
Sources
Effects
POLLUTANTS
• A substance becomes a pollutant when it is present
in a concentration that is high enough for it to have a
harmful effect on the natural environment.
• Substances that are normally considered harmless
may become pollutants if present in:
high enough concentrations and
the wrong place at the wrong time.
Quantitative Test
The maximum safe limit of nitrate in drinking water is a
concentration of 45 ppm (mgdm-3). A sample of water
(volume 250 cm3) was analysed and found to contain 0.012 g
of NO3(i)
What is the concentration of NO3- in the sample in moldm-3?
(ii) Would the water be considered safe to drink?
(iii) Ammonium nitrate (NH4NO3) is a common, solid fertilizer. It
supplies nitrogen to the soil which is an essential plant
nutrient. What percentage of nitrogen by mass does it
contain?
An environmental pollution model
By Water
Air
Dumped on land
Three main types of environmental
pollution
1.
Air pollution
2.
Water
pollution
3.
land
pollution
AIR POLLUTION
• The main sources of air pollution can be generally
classified as:
Inorganic and Organic pollutants.
• Gaseous inorganic pollutants enter the atmosphere
as a result of human activities
• Those added in the greatest quantities are:
CO, SO2, NO, and NO2.
• Other inorganic pollutant gases include:
NH3, N2O, N2O5, H2S, Cl2, HCl, and HF.
• Natural sources are the most important contributors
of organics in the atmosphere
Some of the effects of air pollution
Ozone layer depletion
Global warming and
the greenhouse effect
Acid deposition
Acid deposition
• This is a term used to describe all precipitation
(rain, snow or fog) which is made acidic by
acids stronger than aqueous CO2.
• The gases SO2 and NO2, mainly emitted from
fossil fuel combustion, are major contributors
towards acid rain since these gases are
oxidized to acids by the oxygen in the
atmosphere:
WATER POLLUTION
• The quality of drinking water is very important
to human welfare. However, pollution of
water results from various sources with
serious health effects.
• Some water pollution sources are:
1. Heavy metals
2. Detergents and fertilizers
3. Acid-polluted water (pH<3)
4. PCBs (polychlorinated biphenyls)
5. Raw sewage
Some of the effects of water pollution
1. Heavy metals: Metals such as Cd, Pb and Hg
 These metals can prove poisonous to humans
– Cadmium and mercury can cause kidney
damage,
– lead poisoning can cause damage to the
kidneys, liver, brain and central nervous
system.
All of these metals are cumulative poisons
Some of the effects of water pollution
2. Detergents and fertilizers: These may contain
phosphates as additives
 Eutrophication and threatens the development of
higher life forms, such as fish.
(Reduction of the dissolved oxygen concentration of
the water).
3. Acid-polluted water (pH<3): Acid mine water
principally contains sulfuric acid produced by the
oxidation of iron pyrites (FeS2)
Some of the effects of water pollution
4. PCBs (polychlorinated biphenyls): The organic
compound are used as fluids in transformers
and capacitors. Although their manufacture
has been stopped.
PCBs are resistant to oxidation when released
into the environment and so persist for a long
time
– can cause skin disorders in humans.
– They may be carcinogenic to humans.
Some of the effects of water pollution
5. Raw sewage:
When a source for drinking water becomes
contaminated with untreated sewage it is
possible to spread diseases through the water
like:
– Giardiasis, a diarrheal disease caused by a
parasitic protazoa, Giardia lamblia.
– These types of diseases can also be caused by
bacteria, viruses, and other microorganisms.
LAND POLLUTION
Land pollution involves disposal of hazardous
waste on, or within a hole in, the ground.
Some of the effects of land pollution
Problems associated with pollution include:
 Volatile waste may lead to unpleasant odours
The decomposition of garbage may release
methane and other gases for many years.
Also, rain may dissolve (leach) buried toxic
material – the resulting solution can contaminate
drinking water supplies via underground water
courses.
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