Transcript Atmospheric Pollution

Atmospheric Science and Pollution
ENV 4030 (3 credits)
大气科学与污染
Textbook
Atmospheric Pollution
History, Science, and Regulation
By Mark Z. Jacobson
Cambridge 2002
Preface
Atmospheric pollution = air pollution ???
Air pollution problems on the Earth are as old as the Earth itself
Air is not privately owned; instead, it is common property共同财产
1. Natural air pollution: volcano eruption 火山爆发 ,
fumaroles火山喷气孔, natural fires自然火灾, desert dust
沙尘暴
2. Anthropogenic (manmade 人为) air pollution
Manmade pollution
1. Urban smog 城市烟雾
2. Indoor air pollution (indoor air quality, IAQ)
3. Acid deposition 酸雨
4. Antarctic ozone depletion 南极臭氧层空洞
(global ozone reduction 全球臭氧损耗)
5. Global warming 全球变暖
(green house effect 温室效应)
Chapter 1
Basics and History of Discovery of Atmospheric Chemicals
大气化学物的发现历史
1.6. Summary
In this chapter, atoms, molecules, elements, and compounds
were defined and a history of the discovery of elements and
compounds of atmospheric importance was given. Only a few
elements, including carbon, sulfur, and certain metals, and a
few solid compound, including calcite方解石, halite石盐, and
nitre硝石, were known in ancient times古代. An acceleration
of the discovery of elements and compounds, particularly of
gases, occurred near the end of the eighteenth century 18世
纪末 1790s.
1.6. Summary (continued)
Several types of chemical reactions化学反应 occur in the air,
including photolysis光分解, kinetic动力学, thermal
decomposition热分解, isomerization异构化, and combination
reactions化合反应. The rate of reaction反应速度 depends on
the reactivity活性 and concentration of molecules. The
chemical e-folding lifetime指数递减时间 of a substance is the
time required for its concentration to decrease to 1/e its
original value and gives an indication of the reactivity of the
substance. Molecules with free electrons自由电子are called
free radicals自由基 and are highly reactive 高活性.
e 指数= 2.718281828…… π 圆周率 = 3.14159265…….
1.1 Basic Definitions
Atmosphere 大气 = Air 空气 ????
Air is a mixture of gases and particles, both of which are
made of atoms. In this section, atoms, elements, molecules,
compounds, gases, and particles are defined.
A gas consists of individual atoms or molecules that are
separated, whereas a particle consists of aggregates集合体
of atoms or molecules bonded together. Thus, a particle is
larger than a single gas atom or molecule. Second, whereas
particles contain liquids or solids, gases are in their own
phase state.
1.2 History of Discovery of Elements and Compounds of
Atmospheric Importance
1.3 Chemical Structure and Reactivity 活性
O3
NO2
A single dot indicates that the atom has a free electron. Compounds
with a free electron are called free radicals and are highly reactive.
Some nonfree radicals that have a single bond are also reactive
because single bonds are readily broken. Compounds with double or
triple bonds are not so reactive because they are difficult to break.
Noble elements惰性氣體 has no free electrons and no potential to
form bonds with other elements; thus, they are chemically unreactive
(inert惰性).
1.4. Chemical reactions and photoprocesses光反应
Photolysis reactions are unimolecular单分子
(involving one reactant反应物)
For example
NO2(g) +
hv
→
太阳辐射
nitrogen
solar
dioxide radiation
wavelength 420nm
NO(g)
nitric
oxide
+ O(g)
atomic
oxygen
Chemical kinetic reactions are usually bimolecular双分子
Thermal decomposition reaction 热分解反应
.
N2O5(g) + M → NO2(g) + NO3(g) + M
dinitrogen
pentoxide
nitrogen
dioxide
nitrate
radical
M can be any molecule that provides collisional
energy碰撞能量.
Isomerization reaction 异构化反应
H2-C-O-O*
+
excited激发态
Criegee biradical
M → HO*-CH=O
+
M
excited formic
acid
M can be any molecule that provides collisional energy碰
撞能量.
Isomers 异构体:
chemical compound which has the same number and kind
of atoms as another but differs in structural arrangement原
子排列
Collision reaction 碰撞反应
.
CH4(g)
methane
.
+ OH(g) → CH3(g) + H2O(g)
hydroxyl
radical
methyl
radical
water
vapor
Termolecular三分子 collision reactions are rare稀有 because
the probability概率 that three gases collide simultaneously同时
发生 and change form is not large
.
NO2(g) + NO3(g) + M
nitrogen
dioxide
nitrate
radical
 N2O5(g) + M
dinitrogen
pentoxide
M is any molecule whose purpose目的 is to carry away
energy released 释放 during the reaction.
Chapter 2
The Sun, the Earth, and the evolution进化 of the
Earth’s atmosphere 太阳、地球 和大气的进化
2.4. Summary
The sun formed from the condensation of the solar nebula太阳
星云 about 4.6 billion years ago (b.y.a) 46亿年前. Solar
radiation 太阳辐射 incident on the Earth originates from the
sun’s photosphere光球. The photosphere emits radiation with
an effective temperature near 6,000 K (5,727 ℃). The solar
spectrum consists of UV紫外线, visible可见光谱, and near–IR
近红外线 wavelength regimes. The Earth formed from the
same nebula as the sun. Most of the Earth’s growth was due to
asteroid 小行星 and meteorite 陨石 bombardment 碰撞.
1 billion = 10 亿 = 1,000,000,000 = one thousand million
2.4. Summary (continued)
The composition of the Earth, percentage-wise, is similar to
that of stony meteorites. Dense compounds高密度 and
compounds with high melting points 高熔点settled to the
center of the Earth. Light compounds and those with low
melting points became concentrated in the crust地壳. The
first atmosphere of the Earth, which consisted of hydrogen氢
and helium氦, may have been swept away吹掉 by an
enhanced solar wind太阳风 during early nuclear explosions
核爆炸 in the sun. The second atmosphere, which resulted
from outgassing气体释出, initially consisted of carbon
dioxide, water vapor, and assorted gases混合气体.
2.4. Summary (continued)
When microbes微生物 first evolved进化, they converted
carbon dioxide, ammonia氨, hydrogen sulfide硫化氢 , and
organic material有机物 to methane甲烷, molecular nitrogen
氮, sulfur dioxide二氧化硫 , and carbon dioxide, respectively.
Oxygen-producing photosynthesis 光合作用 led to the
production of oxygen氧 and ozone臭氧. The presence of
oxygen resulted in the evolution of aerobic respiration需氧呼
吸, which led to a more efficient means of producing
molecular nitrogen, the major constitutent要素 in today’s
atmosphere (80% by volume).
2.1. The Sun and its Origin 太阳的诞生
About 15 b.y.a.(150 亿年前), all mass in the known universe
宇宙 may have been compressed 压缩 into a single point,
estimated to have a density 密度 of 109 kg m-3 and a
temperature of 1012 K. With the ‘Big Bang 大爆炸’, this point
of mass exploded, ejecting 弹射出 material to all directions.
Aggregates 聚集物 of ejected material collapsed 压缩
gravitationally引力 to form the earliest最早期 stars 恒星;.
When temperatures in the cores中心 of early stars reached
10 million K, nuclear fusion 核聚变 of hydrogen into helium
and higher elements began, releasing释放 energy that
powered the stars. As early stars aged, they ultimately
exploded, ejecting stellar 星形的 material into space.
About 4.6 b.y.a., some interstellar material aggregated to
form a cloudy mass, the solar nebula太阳星云. The
composition of the solar nebula was the same as that of 95
percent of the other stars in the universe. Gravitational
collapse of the solar nebula resulted in the formation 形成 of
sun
2.2. Spectra光谱 of the radiation辐射of the Sun and the
Earth
Life on Earth 地球上的生命would not have evolved进化to
its present state without heating (energy) by solar radiation.
Radiation辐射is the emission发射or propagation传播 of energy
in the form of a photon光子 or electromagnetic wave电磁波 .
A photon is a particle or quantum of energy量子能量 that has no
mass没有质量, no electric charge没有电荷, and an indefinite
lifetime无尽生命.
An electromagnetic wave is a disturbance扰乱 traveling through
a medium媒体, such as air or space宇宙空间(vacuum真空), that
transfer energy from one object to another without permanently
永久性 displacing取代 the medium itself.
A blackbody黑体 is a body that absorbs吸收 all radiation
incident on it but it also emit发射radiation with 100% efficiency.
Both the Sun and Earth are very close接近 to blackbodies
as no bodies are true blackbodies.
伽马射线
波长
可见光
红外线
微波
无线电波
2.3. Primordial Evolution 原始进化of the Earth and
its Atmosphere
球核心的内层
2900-6371 km
iron 铁
地幔
50 – 2900 km
magnesium镁
地壳
0 – 50 km
silicate 硅酸盐
billion
years
ago
Fig. 2.8. Timeline of evolution on the Earth地球进化年历表
To date
迄今
2.3.2. Prebiotic atmosphere 有生命前的大气
The temperature on Earth was still very high, the atmosphere
contained mainly molecular hydrogen, methane, ammonia,
molecular nitrogen and hydrogen sulfide.
2.3.3. Biotic atmosphere before oxygen 无氧前的有生命大气
Abiotic synthesis非生物合成 is the process by which life is created
from chemical reactions and electric discharges.
Phototrophs光合菌 are organisms that obtain their energy from
sunlight, such as some sulfur bacteria硫磺菌.
CO2(g) + 2H2S +
hydrogen
sulfide
hv → CH2O(aq) + H2O(aq) + 2S(g)
sunlight
carbohydrate
碳水化合物
sulfur
Lithotrophs无机氧化生物 are organisms that obtain their energy
from oxidation of inorganic compounds such as carbon dioxide,
hydrogen, hydrogen sulphide, such as some methanogenic bacteria.
Methane甲烷
4H2(g) + CO2(g) → CH4(g) + 2H2O(g)
(anaerobic repiration无氧呼吸)
Conventional heterotrophs异养生物 are organisms that obtain their
energy from oxidation of organic compounds, such as humans.
fermentation发酵
C6H12O6(aq) →
2C2H5OH(aq)
glucose
ethanol乙醇
+ CO2(g)
Carbon sources碳源 for organisms
Autotrophs自养生物 are organisms that obtain their carbon from
carbon dioxide.
Photoautotrophs 光合自營性菌 derive their energy from sunlight
and carbon from carbon dioxide, such as all green plants.
photosynthesis光合作用
6CO2(g) + 6H2O(aq) + hv
→
C6H12O6(g)
+ 6O2(g)
Lithotrophic autotrophs derive their energy and carbon from
inorganic material.
Lithotrophic heterotrophs derive their energy from inorganic
material but their carbon source from organic material.
2.3.5. Aerobic respiration 需氧呼吸
C6H12O6(g)
+ 6O2(g)
→
6CO2(g) + 6H2O(aq)
Oxygen cycle 氧循环
The Oxygen cycle is the biogeochemical cycle that describes the
movement of oxygen within and between its three main reservoirs:
the atmosphere (air), the total content of biological matter within the
biosphere (the global sum of all ecosystems), and the lithosphere
(Earth's crust). Failures in the oxygen cycle within the hydrosphere
(the combined mass of water found on, under, and over the surface
of a planet) can result in the development of hypoxic zones. The
main driving factor of the oxygen cycle is photosynthesis, which is
responsible for the modern Earth's atmosphere and life.
2.3.6. Nitrogen cycle 氮循环
nitrogen fixation固氮作用
ammonification氨化作用
nitrification 硝化作用
denitrification反硝化作用
Most nitrogen is found in the atmosphere. The nitrogen cycle is the
process by which atmospheric nitrogen is converted to ammonia or
nitrates.
Nitrogen is essential to all living systems. To become a part of an
organism, nitrogen must first be fixed or combined with oxygen or
hydrogen. Nitrogen is removed from the atmosphere by lightening and
nitrogen fixing bacteria. During electrical storms, large amounts of
nitrogen are oxidized and united with water to produce an acid which is
carried to the earth in rain producing nitrates. Nitrates are taken up by
plants and are converted to proteins.
Then the nitrogen passes through the food chain from plants to
herbivores to carnivores. When plants and animals eventually die, the
nitrogen compounds are broken down giving ammonia
(ammonification). Some of the ammonia is taken up by the plants;
some is dissolved in water or held in the soil where bacteria convert it
to nitrates (nitrification). Nitrates may be stored in humus or leached
from the soil and carried to lakes and streams. It may also be converted
to free nitrogen (denitrification) and returned to the atmosphere