Indeks Kualitas Udara Perkotaan

Reaksi-reaksi atmosfer dan
Dampak pencemaran udara
terhadap kesehatan dan
lingkungan
Kuliah Minggu VIII
Laboratorium Pencemaran Udara dan Perubahan Iklim (LPUPI)
Jurusan Teknik Lingkungan FTSP ITS
Komposisi Atmosfer
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The atmosphere consists of the thin layer of
mixed gases covering the earth’s surface.
Exclusive of water, atmospheric air is 78.1% (by
volume) nitrogen, 21.0% oxygen, 0.9% argon, and
0.03% carbon dioxide.
Normally, air contains 1-3% water vapor by
volume; large variety of trace level gases at levels
below 0.002% (neon, helium, methane, krypton,
nitrous oxide, hydrogen, xenon, sulfur dioxide,
ozone, nitrogen dioxide, ammonia, and carbon
monoxide)
Pembagian Atmosfer berdasarkan
temperatur

troposphere extending in altitude from the earth’s surface to approximately 11 -16
kilometers (km), homogeneous composition of major gases (results from constant
mixing by circulating air masses); decreasing temperature with increasing altitude  The
temperature of the troposphere ranges from an average of 15°C at sea level to an average
of -56°C at its upper boundary.
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the water vapor content of the troposphere is extremely variable because of cloud formation,
precipitation, and evaporation of water from terrestrial water bodies.
stratosphere  11 km to approximately 50 km. The average temperature of the
stratosphere increases from -56°C at its boundary with the troposphere to –2°C at its upper
boundary. The reason for this increase is absorption of solar ultraviolet energy by ozone
(O3) in the stratosphere
Mesosphere immediately above the stratosphere results in a further temperature decrease
to about –92°C at an altitude around 85 km.
thermosphere, in which the highly rarified gas reaches temperatures as high as 1200°C
by the absorption of very energetic radiation of wavelengths less than approximately 200
nm by gas species in this region
Stratifikasi
Atmosfer
dan
Spesies
yang
dipengaruhi
fotoreaksi
“Lee Chateleur” Principle
Strata Atmosfer
Sifat Fisik dan Kimia
Troposphere
Makin tinggi  tekanan menurun,
temperatur menurun. Reaksi makin
cepat ke arah exotermis, dan
pemecahan molekul.
Stratosphere
Makin tinggi  tekanan makin turun,
temperatur makin naik. Reaksi kimia
makin cepat ke arah endotermis dan
pemecahan molekul.
Mesosphere
Makin tinggi  tekanan makin rendah
dan suhu makin rendah. Reaksi
molekul menjadi lebih sulit karena
tekanan terlalu rendah, tumbukan
antar molekul makin jarang.
Thermosphere
Makin tinggi  tekanan makin rendah,
suhu extrem makin tinggi, rekasi
makin sulit terjadi.
Beberapa parameter kunci pada
kinetika dan reaksi atmosfer
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Molekul stabil  CO2, N2, O2, dimana O2 merupakan dasar dari
kimia ozon (O3)
Oksida nitrogen  sebagai katalis di troposfer dalam deret reaksi
konversi hidrokarbon menjadi spesies teroksidasi, menghasilkan
ozon dan partikel (penggunaan fossil fuel  menunjukkan kenaikan
konsentrasi zat ini di northen hemisfer dekat permukaan)
Radikal hidroksil  spesies reaktif yang utama di troposfer dan
meremove sebagian besar jenis polutan di udara (terbetuk dari
kombinasi ozon dan uap air, dengan radiasi sinar matahari)
CO reagen penting di atmosfer  diemisikan langsung dari
pembakaran kondisi kurang oksigen atau dihasilkan di atmosfer
melalui oksidasi virtual seluruh hydrokarbon.
Kira-kira ¾ OH atmosfer akan bereaksi dengan CO menghasilkan
1/6 CO2 di atmosfer
ENERGY BALANCE ATMOSFIR
BUMI
Proses
yang
terjadi
pada
spesies
gas di
atmosfer
Major atmospheric Chemical
Process
Gas-gas yang berperan dalam
reaksi atmosfer

Gaseous atmospheric chemical species fall into the following
somewhat arbitrary and overlapping classifications:
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
Inorganic oxides (CO, CO2, NO2, SO2),
oxidants (O3, H2O2, HO. radical, HO2. radical, ROO. radicals, NO3),
reductants (CO, SO2, H2S),
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),
oxidized organic species (carbonyls, organic nitrates),
photochemically active species (NO2, formaldehyde),
acids (H2SO4, HNO3, etc),
bases (NH3),
salts (NH4HSO4,), and
unstable reactive species (electronically excited NO2, HO• radical)

solid and liquid particles in atmospheric

aerosols and clouds play a strong role in
atmospheric chemistry as sources and sinks
for gas-phase species, as sites for surface
reactions (solid particles), and as bodies for
aqueous-phase reactions (liquid droplets).
Atmospheric
Chemistry starts with sunlight
O3
v = c/
O +O2
• Breaking chemical bonds
requires energy
• Sunlight has energy
• If sufficient energy is deposited
in the bond, then it will break
• O3 has a bond energy of ~105
kJ mol-1
visible
E = hv
Red
Orange
Yellow
Green
Blue
Violet
Near UV
Far UV
700
620
580
530
470
420
400-200
200-50
Energy/kJ mol-1
170
190
210
230
250
280
300-600
600-2400
The Troposphere
Stratosphere, upper atmosphere
10-16 k m, -56ūC
Troposphere
O2, N2, Ar, CO2, trace gas es
Vapor
NO 2 + h
NO + O
Photoche mical reactions
H2O
Droplets
Air pollutan ts
Particle s
Temperature
invers ion
We athe r
The Stratosphere (Cont.)
High-ene rgy ultraviolet, wavelength less than 100 nanometers,
pen etrating to arou nd 200 k m
altitude
Ultraviolet above 330 nanometers, visible light, infrared,
pen etrating through the stratos phere and to Earth Õs su rface
Ultraviolet be tween 200-330
nanometers pe netrating to
around 50 k m altitude
~ 50 k m, -2ūC
O2 + h
O + O
Stratosphe re
O2 + O
O3
O3 + h
O2 + O
(filtration of ultraviolet radiation )
10-16 k m, -56ūC
Reaksi fotokimia
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Penyerapan energi cahaya (spektrum) oleh
spesies kimia, khususnya radiasi ultraviolet, dari
matahari, dapat menyebabkan reaksi kimia
Adanya katalis, akan menyebabkan reaksi
fotokimia dapat terjadi pada suhu/energi lebih
rendah
Reaksi ini dapat digunakan untuk prediksi
keberadaan dan nasib (fate) spesies kimia di
atmosfer

Nitrogen dioxide, NO2, is one of the most
photochemically active species found in a
polluted atmosphere and is an essential
participant in the smog-formation process.
A species such as NO2 may absorb light of
energy hv, producing an electronically
excited molecule.
Proses reaksi fotokimia

Loss of energy to another molecule or atom (M) by
physical quenching, followed by dissipation of the
energy as heat
Ion dan Radikal di Atmosfer
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Salah satu karakteristik atmosfer bagian atas adalah adanya ion-ion
positif maupun negatif yang stabil (ionosphere  > 50 km)
Producer ion-ion yang utama adalah reaksi yang diakibatkan oleh
cahaya ultraviolet intensitas tinggi
Di troposphere juga terbentuk ion-ion, pada fenomena titik-titik air
yang mengalami gesekan, kompresi selama presipitasi akibat
fenomena turunnya massa udara dingin atau karena angin panas
yang kuat. (Fenomena Foehn/Sharav/Santa Ana)

energetic electromagnetic radiation in the
atmosphere may produce atoms or groups
of atoms with unpaired elect rons called
free radicals
 Proses
Pembentukan Radikal (inisiasi)
 Proses
Reaksi dengan senyawaan netral
(propagasi)
 Proses
reaksi radikal dengan radikal
(terminasi)
Radikal Hodroksil dan
Hidroperoksil di Atmosfer
Removing OH radikal dari Atmosfer
Reaksi Kimia dan Biokimia
Atmosfer
NOx sinks & transport
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NOx lifetime ~1 day
NOx sinks – primarily
HNO3
HNO3 is water soluble

PAN allows locally produced NOx to be
transported on global scales
Kelas utama bahan pencemar di udara
Kelas
Contoh
Carbon oxides
Carbon monoxide (CO), Cabon dioxide (CO2)
Sulfur oxides
Sulfur dioxide (SO2), Sulfur trioxide (SO3)
Nitrogen oxides
Nitric oxide (NO), nitrogen dioksida (NO2), nitrous oxide (N2O) (NO
dan NO2 sering tergabung bersama dan diberi label NOx
Volatile Organic Compound (VOCs)
Methane (CH4), propane (C3H8), chlorofluorocarbons (CFCs)
Suspended particulate matter (SPM)
Partikel padat (debu, jelaga, asbestos, timbal, nitrat dan garam
sulfat), butiran air (asam sulfat, PCBs, dioxines dan pestisida)
Photochemical oxidants
Ozon (O3), peroxyacyl nitrates (PANs), hydrogen peroxide (H2O2)
Radioactive substances
Radon-222, iodine-131, strontium-90, plutonium-239
Hazardous air pollutants (HAPs), yang
dapat menyebabkan gangguan
kesehatan
seperti
kanker,
gangguan sistem saraf dan cacat
kelahiran
Carbon tetrachloride (CCl4), methyl chloride (CH3Cl), chloroform
(CHCl3), benzene (C6H6), etylene dibromide (C2H2Br2),
formaldehyde (CH2O2).
General description of a chemical mechanism
Oxygen exchange among the atmosphere,
geosphere, hydrosphere, and biosphere
FENOMENA OKSIGEN DAN NITROGEN
N2 and O2 are by far the most abundant gases in the atmosphere.
Crucial importance of the stratospheric layer of ozone, O3
Oxygen reacts with atmospheric chemical species.
• Through action of intermediate species, particularly hydroxyl radical, HO
• SO2 is converted to H2SO4
• CO is converted to CO2
Atmospheric oxygen comes from photosynthesis
CO2 + H2O + h
{CH2O} + O2 (8.4.2)
where {CH2O} is a generic formula representing biomass
Nitrogen in the atmosphere
Atmospheric N2 is very unreactive
Most important reaction of N-containing species in the atmosphere
NO2 + h
NO + O (8.4.3)
Reactive O atom initiates many tropospheric photochemical reactions
Chemical Processes on and in Atmospheric Particles
POLLUTANT GASEOUS OXIDES
Carbon Monoxide
Toxic to humans by binding to blood hemoglobin and
preventing the hemoglobin from transporting oxygen from the
lungs to other tissues.
Catalytic destruction in auto exhausts:
2CO + O2
2CO2
(8.6.1)
Modern automobile engines use computerized control of
engine operating parameters along with exhaust catalysts to
control carbon monoxide emissions.
Pollutant Gaseous Oxides (Cont.)
Sulfur Dioxide
From several natural and pollutant sources
Direct effects
• On people with respiratory problems
• On plants
Most important indirect effect is atmospheric sulfuric acid
formation
2SO2 + O2 + 2H2O
2H2SO4
(8.6.2)
Avoiding sulfur dioxide pollution by not using sulfur-containing
fuels (coal)
Fluidized bed combustion in a granular medium of CaO that
absorbs SO2
CaO + SO2
CaSO3 (8.6.3)
Scrubbing with substances that absorb sulfur dioxide from
stack gas
Ca(OH)2 + SO2
CaSO3 + H2O (8.6.4)
Green Chemistry and Sulfur Dioxide
Sulfur is a valuable raw material required in the
manufacture of sulfuric acid, one of the largest
volume chemicals made.
Hydrogen sulfide, H2S, can be used to make sulfur
dioxide.
In the Kalundborg, Denmark, industrial ecosystem,
sulfur dioxide scrubbed from stack gas is oxidized
CaSO3 + 1/2O2 + 2H2O
CaSO4.2H2O
(8.6.5)
and used to make gypsum for wallboard.
Nitrogen Oxides in the Atmosphere
Nitrous oxide (N2O), colorless, odorless, nitric oxide (NO), and
pungent-smelling, red-brown nitrogen dioxide (NO2) occur in
the atmosphere.
Nitrous oxide generated by bacteria
In the stratosphere: N2O + h
N2 + O
(8.6.6)
Both NO and NO2, collectively designated as NOx, are
produced from natural sources, such as lightning and
biological processes, and from pollutant sources.
Pollutant concentrations can become too high locally and
regionally.
In the internal combustion engine,
N2 + O2
2NO (8.6.7)
Combustion of fuels that contain organically bound nitrogen
also produces NO.
Atmospheric chemical reactions convert some of the NO
emitted to NO2.
NO2 in the Atmosphere
Electromagnetic radiation below 398 nm causes
NO2 + h
NO + O (8.6.8)
• Produces highly reactive O atoms
• O atoms can participate in a series of chain reactions through which NO is
converted back to NO2, which can undergo photodissociation again to start the
whole cycle over.
NO2 more toxic than NO
• Exposure to 100-500 ppm of NO2 causes a lung condition called bronchiolitis
fibrosa obliterans
• Exposed plants may suffer decreased photosynthesis, leaf spotting, and
breakdown of plant tissue.
Reducing release of NO from combustion sources
• Limiting excess air so that there is not enough excess oxygen to produce NO
• Exhaust catalytic converters reduce NOx emissions from automobile exhausts.
Halogen Gases in the Atmosphere
Gaseous chlorine, fluorine, and volatile fluorides are uncommon air
pollutants, but very serious where they occur.
Elemental chlorine, Cl2, is widely produced and distributed as a water
disinfectant, bleach, and industrial chemical.
Accidental releases of Cl2 have killed people
Hydrogen chloride, HCl, from accidental releases and by reaction of
reactive chlorine-containing chemicals, such as SiCl4,
SiCl4 + 2H2O
SiO2 + 4HCl (8.8.3)
HCl gas from combustion of polyvinylchloride (PVC) plastic
Exists as droplets of hydrochloric acid
Elemental fluorine (F2) and hydrogen fluoride, both highly toxic, are rarely
released to the atmosphere.
Gaseous silicon tetrafluoride, SiF4, can be released when fluorspar (CaF2)
reacts with sand (SiO2):
2CaF2 + 3SiO2
2CaSiO3 + SiF4 (8.8.4)
Sulfur hexafluoride, SF6, is astoundingly unreactive and a powerful
greenhouse warming gas
Hydrogen Sulfide, H2S
Hydrogen sulfide, H2S is as toxic as hydrogen cyanide.
From geothermal sources, the microbial decay of organic
sulfur compounds, and the microbial conversion of sulfate,
SO42-, to H2S when sulfate acts as an oxidizing agent in the
absence of O2
Wood pulping processes can release hydrogen sulfide.
H2S is a common contaminant of petroleum and natural gas.
Poza Rica, Mexico, incident in 1950 killed 22 people
H2S is phytotoxic (harms or kills plants)
H2S forms a black coating of copper sulfide, CuS, on copper
roofing which weathers to CuSO4 3Cu(OH)2.
H2S oxidizes to SO2.
COS and CS2, occur in the atmosphere
CO2: THE ULTIMATE AIR POLLUTANT?
Carbon dioxide, CO2, is a normal essential
constituent of the atmosphere.
Levels now about 380 parts per million by volume and
increasing by at least 1 ppm/year
Potential greenhouse effect
Evidence of warming during 1980s, 1990s, early
2000s
Other gases such as N2O and CH4 can cause
greenhouse warming
CHEMICAL MECHANISMS
solar radiation, O2
NO2
O3
NO
HNO3
CO2
wet dep
O3
OH
O2
HO2
CO
solar rad.
H2O2
• Analzye mechanism using principles of chemical kinetics
wet dep
CHEMICAL KINETICS
• Chemical kinetics
A study of the rate at which chemical reactions take place and the detailed
chemical mechanism by which they occur
• Rules
Mass balance  integrity of atoms is preserved in a chemical reactions 
number of atoms of each each element on each side of the reaction must
balance
CO + 2O2  CO2 + O3
Charge conservation  electrons are conserved in chemical reactions  net
charge of reactants are equal to net charge of products
HCO3-  CO32- + H+
CH4 Oxidation Scheme
CH4 + OH
CH3O2 +
CH3O +
HO2 +
(+O2)
CH3O2 + H2O
NO
CH3O + NO2
O2
HO2 + HCHO
NO
OH + NO2
HCHO + OH (+O2)
HO2 + CO + H2O
HCHO + h
H2 + CO
HCHO + h (+2O2)
2HO2 + CO
Note:
2 × (NO
NO2) conversions
HCHO formation provides a route to HO2 radical formation.
Chemistry of ozone formation
sunlight
O3
O2
sunlight
NO2
NO
OH
HO2
RO2
RO
oxidation
product
VOC
O2
NO
NO2
O2
O3
sunlight
O2
General VOC oxidation scheme
O3 + h
O1D + O 2
O 1 D + H2 O
2OH
OH + RH (+O2)
RO2 + H2O
RO2 + NO
NO2 + RO
RO + O2
HO2 +R’CHO
HO2 + NO
OH + NO2
NO2 + h
NO + O; O + O2
O3
OVERALL
NOx + VOC + sunlight  ozone
The same reactions can also lead to formation of secondary organic aerosol
(SOA)
SIKLUS KARBON
44
Tugas
Reaksi Asam Basa Atmosfer
 Reaksi Oksigen di Atmosfer
 Reaksi Nitrogen di Atmosfer
 Karbon dioksida di Atmosfer
 Water (air) di Atmosfer
 Reaksi Fotokimia di Atmosfer
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