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What is environmental chemistry?

"What is environmental chemistry? This question is a littledifficult to answer because environmental Chemistryencompasses many different topics. It may involve a study

of Freon reactions in the stratosphere or an analysis oftoxic deposits in ocean sediments. It also covers thechemistry and biochemistry of volatile and solubleorganometallic compounds biosynthesized by anaerobic

bacteria. Environmental chemistry is the study of

the sources, reactions, transport, effects, andfates of chemical species in water, soil, and airenvironments."

- Stanley E. Manahan. 1991. Environmental Chemistry,Fifth edition.

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In the end we will conserve only what we love;

We will love only what we understand;

and we will understand only what we are taught.

Baba Dioum(Senegalese ecologist)

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What does an environmental chemist do?

Environmental

Chemist

Prevent

Environmental

deterioration

Environmental

Clean-up

Environmental

Research Environmental

Regulation

Environmental

Measurement

& Monitoring

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The Environmental Industry in the U.S. in 1995

Sector Amount PercentEngineering & Consulting $12.5 billion 10.2%

Environmental Chem. Labs $1.5 billion 1.2%

Remediation $11 billion 8.9%

Solid waste landfills & transport $33 billion 26.8%

Incineration (waste to energy) $2 billion 1.6%

Recycling $11 billion 8.9%

Water supply & treatment $30 billion 24.4%

Air quality $6 billion 4.9%

Equipment/New technology $11 billion 8.9%

Asbestos removal $2 billion 1.6%

Medical wastes $1 billion 0.8%

Underground storage $2 billion 1.6%

Total for environmental Industry $123 billion 100%

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The Nobel Prize in Chemistry 1995

for their work in atmospheric chemistry,particularly concerning the formation anddecomposition of ozone

Paul JCruzen

Mario JMolina

F. SherwoodRowland

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Press Release: The 1995 Nobel Prize in Chemistry

KUNGL. VETENSKAPSAKADEMIEN

THE ROYAL SWEDISH ACADEMY OF SCIENCES

11 October 1995

Paul Crutzen, Mario Molina and Sherwood Rowlandhave all made pioneering contributions to explaininghow ozone is formed and decomposes through chemicalprocesses in the atmosphere. Most importantly, theyhave in this way showed how sensitive the ozone layer isto the influence of anthropogenic emissions of certaincompounds. The thin ozone layer has proved to be an

Achilles heel that may be seriously injured by apparentlymoderate changes in the composition of the atmosphere.

NOTE: Achilles heel: A seemingly small but mortal weakness. [From Achilles

being vulnerable only in the heel.]

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By explaining the chemical mechanisms

that affect the thickness of the ozonelayer, the three researchers havecontributed to our salvation from aglobal environmental problem thatcould have catastrophic consequences.

Press Release: The 1995 Nobel Prize in ChemistryKUNGL. VETENSKAPSAKADEMIENTHE ROYAL SWEDISH ACADEMY OF SCIENCES11 October 1995

(Continued)

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How this knowledge evolves?

Ozone formation: Chapman Theory

O2+ uv-light -> 2O

O+O2+M -> O3+M

Where M is a random air molecule (O2 or N2)

Chapman theory describes how sunlight converts the various forms of

oxygen from one to another, explains why the highest content of ozoneoccur in the layer between 15 and 50 km, termed the ozone layer

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The Chapman theory, however, overestimates the ozonecontents. Thus, there must be other chemical reactions

contributing to the reduction of the ozone content.

In 1970, Paul Crutzen showed that the nitrogen oxidesNO and NO2 react catalytically (without themselves

being consumed) with ozone, thus accelerating the rateof reduction of the ozone content.

NO+O3 -> NO2 +O2

NO2+O -> NO+O2

O3+uv-light -> O2+O

______________________

Net result: 2O3 -> 3O2

NO

N2O

Microorganism

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Discovery of the ozone hole

The Englishman JosephFarman and his colleaguesnoted a drastic depletion ofthe ozone layer (mean

monthly value in October),over Halley Bay theAntarctic, the "ozone hole.

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Environmental Chemistry

Energy: Introduction

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The question of energy use underliesvirtually all environmental issues

Energy

use

Economic

development

Better

life

Energy

exploration

Pollution

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Energyand

well-being

Energy use per capita versus gross national product per capita

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Energy use trends in the past one century

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What is energy?

Energy is usually defined as the ability todo work or bring about changes.

Energy can take many forms.

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Forms of energy

Heat and work (mechanical energy) areinterconvertible forms of energy.

Kinetic energy is the work that a body can do byvirtue of its motion. (a moving car, wind, flowing

water, a falling rocks, etc). Potential energy is the work that a system ofbodies is capable of doing by virtue of the relativeposition of its parts. Water held behind a dam,

a rock at the edge of a cliff,

chemicals reacting in a battery, etc.

Radiant energy is energy carried by light waves.

Electrical energy

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Units of energy

Energyform

Correspondingenergy unit

Definition

heat Calorie, kcal

btu

One calorie is the heat needed to raise thetemperature of 1 g of water by 1oC.

one BTU is the heat needed to raise the

temperature of 1 lb of water by 1 oF.

work Joule, kJ

erg

One joule is the work done by a force thataccelerates a 1-kg mass at 1.0 m/s2 for adistance of 1m.

One erg is the work done by a force that

accelerates a 1-g mass at 1 cm/s2 for adistance of 1 cm

electricenergy

kwh One kWh is the energy consumed or producedin one hour by a 1 kW power.

To be continued

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Units of energy (Continued)

Energy form Correspondingenergy unit

definition

Chemical

energy

kJ/mol One kJ/mol is the energy associatedwith 1 mol of chemical molecules

Radiantenergy

cm-1 Wavenumber (cm-1) is the inverse ofwavelength for a electromagneticwave.

Radiation orenergypossesses byelementaryparticles

eV, MeV One electron volts (ev) is the amountof energy acquired by any chargedparticle that carries unit electric chargewhen it falls through a potentialdifference of 1 volt.

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Power

Power is a measure of the rate at which energyis used.

Power is expressed in terms of units of energy

used per unit of time.

t

W

P (!

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Power (Continued)

Example units:

One watt (W)= one J/s,

the amount of power available from an electricitycurrent of 1 ampere at the potential difference ofone volt

One kilowatt (kW) = 1000 W

One Megawatt (MW) = 1 million watts

One horsepower= 33,000 ft lb of work/min

(Established in the late 18th century, based onresults obtained with strong dray horses).

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Where do we extract our energy?

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Where does the energy come from?

Solar source Direct

Solar energy (Earth intercepts 500 parts per trillion of theenergy emitted by the Sun)

Indirect Food

Wind

hydropower

Fossil fuel

Nonsolar sources Tidal energy

Geothermal heat

Nuclear energy

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How much solar energy does the earthintercept from the Sun?

The sun radiates at 1.17x1031 kJ/yr.

The earth is 1.5x108 km from the sun.

The earth has a radius of 6.4x103 km.Sun

Earth

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What happens to the solar energy intercepted bythe earth?

30% of this energy is reflected back to the space, andthe rest is absorbed by the earth.

Energy reflected by the atmosphere and clouds: 14.1 x1020 kJ/yr

Energy reflected by the earth surface: 2.2 x1020 kJ/yr.

Total: 16.3 x 1020 kJ/yr

Absorbed solar energy is converted to heat and thisheat flow drives Earth's weather system.

Half of the absorbed energy flows through thehydrological cycle (warming of water bodies,evaporation and precipitation)

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Global energy transport

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Energy in rainfall

HK has an area of 1068 km2. In 2000, the totalrainfall is 275cm. How much energy is releasedin last years rainfall in HK? (Given that

evaporation of 1ml of water requires 2.46 kJ ofenergy at ambient temperature.)

How does the value above compare with the total solar

energy received in HK? (The mean daily solar radiationmeasured on ground was 14.46 MJ/m2 in 2000.)

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Energy in rainfall (Continued)

Energy released = Energy used for evaporation

Energy released = (2.46kJ/ml) x (ml of water)

Ml of rainwater = (area) x (depth of rainfall)

Area = 1068 km2 =1068 x (1000x100)2 cm2= 1.068 x 1013 cm2

Volume of water = 1.068 x 1013 cm2 x 275 cm

=2.94 x 10

15

ml Energy = (2.46 kJ/ml) x (2.94 x 1015 ml)

= 7.23 x 1015 kJ

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Energy in rainfall (Continued)

Solar energy received

= (surface Area) x (solar irradiation perunit area per year)

= 1068x106 m2 x (14.5x103kJ/m2/day x 365

d/yr)=5.65 x 1015 kJ/yr

7.23 x 1015

kJ/yr(Equivalent to energy released by 1.7 x 109 tons TNT)

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What happens to the solar energy intercepted

by the earth? (Continued)

A fraction of this energy is used by green plantsand algae in photosynthesis to provide food for

the planet. We derive our energy by burning wood and other

biomass, and by mining the store ofphotosynthetic products buried in ages past, in

the form of fossil fuels.

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Global Energy Fluxes

Sources Rates(1020 kJ/yr)

Solar energy incident on Earth 54.4

Solar energy affecting Earths climate and biosphere 38.1

Energy used to evaporate water 12.5Energy in wind 0.11

Solar energy used in photosynthesis 0.08

Energy used in net primary productivity 0.0372

E

nergy conducted fromE

arths interior to surface 0.0100Energy in tides and waves 0.0013

Total primary energy consumed by humans, 1990 0.0037

Fossil fuel energy consumed by humans, 1990 0.0030

Energy content of food consumed by humans, 1990 0.000188

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Human Energy Use vs. Natural Energy Flows

Annual energy fluxes on Earth in 1020 kilojoules