chapter 2; air pollution

CHAPTER 2: Air Pollution

Prepared by: Shaheen SardarBSc textile engineeringMS Textile ManagementFaisalabad, Punjab, PakistanEmail: [email protected]

COURSE TITLE: Environmental issues of textile industry

INTRODUCTION

• Air pollution is the introduction of chemicals, particulate matter or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere.

INTRODUCTION

INTRODUCTION

• Sulfurous smog is caused by combustion of fossil fuels, especially coal, in stationary sources such as plants and smelters.

• CO, oxides of nitrogen, and various VOCs swirl around in atmosphere reacting with each other and with sunlight to form Photochemical smog.

INTRODUCTION

• Much of the work on air pollution in the last few decades has centered on a small set of six substances, called Criteria Pollutants” that have been identified as contributors to both sulfurous and photochemical smog problems. We will focus on these Criteria Pollutants.

INTRODUCTION

• More recently, attention has been shifting towards the characterization and control of a growing list of especially hazardous air pollutants, many of which we are exposed to in our homes and workplaces, where we spend roughly 90% of our time.

• Modest improvements in indoor air quality can improve public health as much as major reductions in the traditional outdoor sources.

OVERVIEW OF EMISSIONS

• There are many sources of the gases and particulate matter that pollute our atmosphere.

• Substances that are emitted directly into the atmosphere are called primary pollutants. Examples are Nitrogen oxides and hydrocarbons emitted when fuels are burned.


• Substances that are created by various physical processes and chemical reactions that take place in the atmosphere are called secondary pollutants. Example is ground level ozone (O3) that is created when those chemicals react with each other in the atmosphere.


• Primary pollutants enter the atmosphere as a result of combustion, evaporation, or grinding and abrasion.

• Volatile substances such as gasoline, paints, and cleaning fluids enter the atmosphere by evaporation.


• Dust kicked up when land is plowed and asbestos fibers that flake off of pipe insulation are examples of grinding and abrasion.

• Automobile exhaust emissions and power plant stack gases are created during combustion.


• Combustion accounts for the majority of emissions.

• Combustion is the gases and particulate matter released when fuels are burned.

• Complete combustion of a pure hydrocarbon fuel such as methane CH4 is given below:

• CH4 + 2O2 → CO2 + 2H2O


• If temperature of combustion is not high enough, or there is not enough oxygen available, or if the fuel is not given enough time to burn completely, then following reaction takes place. Where, (HC) stands for hydrocarbons.

• CH4 + O2 → mostly (CO2 + 2H2O) + traces of [CO +(HC)]


• Air is 78% N2 and 21% O2, when temperature of combustion is very high; some of N2 reacts with O2 in air to form various nitrogen oxides. Following reaction takes place.

• Air (N2 + O2) +Heat → Thermal NOX


• If fuel is not pure, then following reaction takes place.

• Fuel (H, C,S, N, Pb, ash) +air (N2 + O2) → Emissions (CO2, H2O, CO, NOX, SOX, Pb, Particulates) + ash


• Secondary pollutant ground level ozone (O3) is formed as a result of following reaction.

• VOCs + NOX + Sunlight → Photochemical Smog (O3 + etc.)


• There are two categories of sources of air pollution, Mobile Sources and Stationary Sources.

• Mobile Sources: Highway vehicles (automobiles and trucks) and other modes of transportation (railroads, aircraft, farm vehicles and “boats and ships”.


• Stationary Sources: There are following three categories of Stationary sources.

• (i) Stationary fuel combustion: Electric power plants and industrial energy systems.

• (ii) Industrial Processes: Metal processing, petroleum refineries, and other chemical and allied product manufacturing.

• (iii) Miscellaneous sources:

OVERVIEW OF EMISSIONS• Following table and figures show emissions of

six air pollutants with respect to mobile sources and stationary sources.

CO Pb NOX VOCs PM10 SOX

Transport 77% 33% 45% 36% 22% 3%

Fuel combustion 6% 10% 50% 3% 46% 88%

Industrial 7% 57% 4% 57% 32% 9%

Miscellaneous 10% 0% 1% 4% 0% 0%


77%

6%

7%10%

CO Transport

Fuel combustion

Industrial

Miscellaneous


33%

10%

57%

Pb Transport

Fuel combustion

Industrial

Miscellaneous


45%

50%

4% 1%NOX

TransportFuel combustionIndustrialMiscellaneous


36%

3%

57%

4%VOCs Transport

Fuel combustionIndustrialMiscellaneous


22%

46%

32%

PM10 TransportFuel combustionIndustrialMiscellaneous


3%

88%

9%

SOX TransportFuel combustionIndustrialMiscellaneous

CRITERIA POLLUTANTS (SIX MOST IMPORTANT POLLUTANTS):

• (1) Carbon Monoxide (CO): • It is produced when carbonaceous fuels are

burned under less than ideal conditions.• Incomplete combustion(yielding CO instead of

CO2) results when any of the following four variables are not kept sufficiently high:

• (1) Oxygen supply, (2) Combustion temperature, (3) Gas residence time at high temperature, and (4) Combustion Chamber Turbulence.

(1) Carbon Monoxide (CO)

• 77% of total CO emissions are from transportation sector.

• All CO in urban areas comes from motor vehicles.

• CO interferes with the blood’s ability to carry oxygen from the lungs to the body’s organs and tissues.

• When inhaled, it readily binds to hemoglobin in the blood stream to form (COHb) carboxyhemoglobin.


• Hemoglobin has greater affinity for CO than O2.

• With less oxygen brain function is effected, Heart rate increases, Physiological effects can be noted, affects brain ability to perceive and react, dizziness, headache, fatigue, and impaired judgment, loss of consciousness and death.


• Tobacco smoke also raises CO levels.• COHb is removed from the bloodstream when

clear air is breathed.


• (2) Oxides of Nitrogen: • 7 oxides of Nitrogen are known, NO, NO2, NO3,

N2O, N2O3, N2O4, and N2O5.

• Only two are important air pollutants, Nitric Oxide (NO) and Nitrogen dioxide (NO2).

• There are following two sources of NOX, when fossils fuels are burned.

• Thermal NOX and Fuel NOX.

(2) Oxides of Nitrogen

• 7 oxides of Nitrogen are known, NO, NO2, NO3, N2O, N2O3, N2O4, and N2O5.

• Only two are important air pollutants, Nitric Oxide (NO) and Nitrogen dioxide (NO2).

• There are following two sources of NOX, when fossils fuels are burned.

• Thermal NOX and Fuel NOX.


• Thermal NOX is created is created when nitrogen and oxygen in the combustion air are heated to a high enough temperature (about 1000K) to oxidize the nitrogen.

• Thermal NOX, results from the oxidation of nitrogen compounds that are chemically bound in the fuel molecules themselves.

• Almost all NOX emissions are in the form of NO, which is a colorless gas and has less effect on health.


• NO can oxidize to NO2, which can irritate the lungs, cause bronchitis and pneumonia, lower resistance to respiratory infections.

• NOX can react with volatile organic compounds (VOCs) in the presence of sunlight to form photochemical oxidants that have adverse health effects.


• NO2 reacts with hydroxyl radical (OH) in atmosphere to form nitric acid (HNO3), which corrodes metal surfaces and contributes to the acid rain problem.

• Modifications to the combustion process that can reduce emissions of CO tend to make the NOX problem worse, and vice versa.

• A reduction in NOX emissions is harder than reductions in other criteria pollutants.


• (3) Photochemical Smog and ground level Ozone:

• Volatile organic compounds (VOCs) include unburnt hydrocarbons that are emitted from tailpipes and smoke attacks when fossil fuels are not completely combusted along with gaseous hydrocarbons that enter the atmosphere when solvents, fuels and other organics evaporate.

(3) Photochemical Smog and ground level Ozone:

• Volatile organic compounds (VOCs) include unburnt hydrocarbons that are emitted from tailpipes and smoke attacks when fossil fuels are not completely combusted along with gaseous hydrocarbons that enter the atmosphere when solvents, fuels and other organics evaporate.


• 1/3 of VOCs emissions result from transport sources.

• 2/3 of VOCs emissions result from industrial sources.

• Less than 2% of VOCs result from fossil fuel combustion in power plants and industrial boilers.


• When oxides of nitrogen, VOCs, and sunlight come together, they can initiate a complex set of reactions that produce a number of secondary pollutants known as photochemical oxidants. Ground level Ozone (O3) is the most abundant of the photochemical oxidants.

• VOCs + NOX + Sunlight → Photochemical Smog (O3 + etc.)


• Ground level Ozone (O3) is harmful to our health. But stratospheric Ozone protects our health by shielding us from ultraviolet radiation from the sun.

• It causes materials and vegetables damage.• It causes respiratory effects such as coughing,

shortness of breath, headache, chest tightness and eye, nose, and throat irritation.


• (4) Particulate matter:• Atmospheric particulate matter consists of any

dispersed matter, solid, or liquid.• Size range from 0.005μm diameter to 100μm

(roughly the size of a human hair).• Term “aerosol” is used for any tiny particulate,

liquid, or solid, dispersed in the atmosphere.

(4) Particulate matter

• Solid particles are called “dust” if they are caused by grinding or crushing operations.

• Solid particles are called “fumes” if they are formed when vapors dense.

• Liquid particles may be called “mist” or “fog”.• Carbon particles that result from incomplete

combustion are called smoke and soot.


• Particles have very irregular shapes.• Large particles that enter the respiratory system

can be trapped by the hairs and lining of the nose. (Driven out by cough or sneeze).

• Smaller particles can be captured by hair like cilia in the respiratory system. (Removed by swallowing or spitting).


• Sources are fuel combustion, industrial processing and transportation.

• Transportation sources are emissions from buses and trucks.

• 95% of particulate emissions are from wild fires, wind-driven soil erosion, dust from croplands, construction, mining activities, and the constant abrasion of paved and unpaved roadways.


• The bulk smoke from diesel engines and smoke stacks consists solid particles made up of “carbon atoms fused in benzene rings” can irritate lungs.

• Of greater concern is a class “Poly nuclear aromatic hydrocarbons consist of fused benzene rings”. Its sources are tobacco smoke, motor vehicle exhaust, the char on charcoal, broiled food, and smoke from wood and coal combustion.


• Most dangerous is a substance called benzo[a]pyrene (Bap), consists of five fused rings. It is a category-A human carcinogen known to cause lung and kidneys cancer.

• Aerosols consisting (SO4) contribute to respiratory distress, degradation of materials, and major cause of reduced visibility.


• Particulates aggravate existing respiratory and cardiovascular disease and damage lung tissue, and some are carcinogenic.

• Tens of thousands of premature deaths are caused each year in US due to inhaled particles.


• (5) Oxides of Sulfur:• Sulfur dioxide is highly water soluble than any other

criteria pollutant. When it is inhaled it is absorbed in moist passages of the upper respiratory tract, the nose and upper airways, where it does less long term damage.

• When Sulfur oxides reach far deeper into the lungs, the combination of particulate matter and sulfur oxides can act synergistically to cause excess mortality. (50,000 premature deaths, 2% of total deaths per year in the US and Canada).

(5) Oxides of Sulfur• Sulfur oxides can damage trees.• Sulfurous pollutants can discolor paint, corrode

metals, and cause organic fibers to weaken.• Airborne Sulfates reduce visibility and discolor

the atmosphere.• Prolong exposure to Sulfates cause serious

damage to building marble, limestone and mortar, as the carbonates (e.g. limestone, CaCO3) in these materials are replaced by sulfates.

• CaCO3 +H2SO4 → CaSO4 + CO2 + H2O.

(5) Oxides of Sulfur• The calcium Sulfate (Gypsum, CaSO4) produced by

this reaction is water soluble and easily washed away leaving a pitted, eroded surface.

• In US, 90% of 22 million tons/ year of sulfurous emissions are the result of fossil fuel combustion in stationary sources. 85% of that is emitted from electric utility power plants (16 million tons/ year).

• 3% sulfurous emissions come from highway vehicles.• Non combustion sulfurous emissions are from

petroleum refining, copper smelting, and cement manufacture.


(6) Lead:• Most lead emissions from motor vehicles

burning gasoline containing the antiknock additive tetraethyl lead Pb (C2H5) 4.

• Ambient (outdoor) lead levels tend to be high in the vicinity (nearness) of industrial facilities such as metal smelters and plants that manufacture lead acid batteries.

• Lead is emitted into the atmosphere in the form of inorganic particulates.

(6) Lead

• Air borne lead may affect human populations by direct inhalation. People living near highways or metal processing plants are at greatest risk.

• In door source of lead is chipped and flaking particles of lead-based paints.

• Most human exposure to lead is from inhalation.• Lead can also be ingested after airborne lead is deposited

onto soil, water, and food crops such as leafy vegetables and fruits.

• Lead poisoning can cause aggressive, hostile, and destructive behavioral changes as well as learning disabilities, seizures, severe and permanent brain damage, and even death.

TOXIC AIR POLLUTANTS

• These are carcinogenic, teratogenic, neurotoxic, which cause reproductive dysfunction, or which are acutely are chronically toxic.

• There are hundreds of such chemicals.• Examples are asbestos, benzene, beryllium,

coke-oven emissions, inorganic arsenic, mercury, radionuclides, and vinyl chloride.

AIR POLLUTION IN BIG CITIES

• Principal source is motor vehicles.• Leaded fuels are burned.• High %age of the vehicles is diesel-powered

trucks and buses with no emission controls.• Many streets are unpaved.• Traffic congestion, which intensifies emissions,

is overwhelming.

AIR POLLUTION IN BIG CITIES

• The resulting concentrations of Pb, CO, NOX, O3 and suspended particulate matter (SPM) are higher.

• Coal-fired power plants and other industrial facilities within city limits and levels of SOX, NOX and particulate matter are high.

• Combustion of coal and biomass fuels for cooking and heating leads to extremely high pollutant concentrations indoors, where many people spend most of their time.

INDOOR AIR QUALITY

• Combustion that takes place inside of homes and other buildings to cook, heat water, and provide space heating and cooling can produce elevated levels of CO, Nitrogen oxides, hydrocarbons, and respirable particulates.

• Cigarette smoke emits CO, benzene, acrobin, and other aldehydes, and particulates, as well as about 4000 other chemicals.

INDOOR AIR QUALITY• Some photocopying machines emit ozone.• Building materials such as particle board,

plywood, urea-formaldehyde foam insulation, and various adhesives emit formaldehyde.

• Chipped and peeling paint containing lead becomes air borne toxic dust.

• A long list of VOCs is emitted from house hold cleaning products, paints, carpeting, and a variety of other chemicals we use in our homes.

INDOOR AIR QUALITY

• Some pollutants are unique to the indoor environment such as following;

• Asbestos: Used for fireproofing and insulation.• Radon gas: Seeps out of the houses and

collects in houses.• Biological Pollutants: Such as house dust

mites, fungi, and other microorganisms.

INDOOR AIR QUALITY

ENVIRONMENTAL TOBACCO SMOKE:• Tobacco Smoke contains over 4000 chemicals,

including more than 40 that cause cancer in humans or animals. Many chemicals are strong respiratory irritants.

• Smokers inhale “mainstream smoke”.

INDOOR AIR QUALITY

ENVIRONMENTAL TOBACCO SMOKE:• Sidestream smoke, emitted from smoldering

cigarettes, mixed with smoke exhaled by smoker is known as “Environmental tobacco smoke (ETS) or secondhand smoke”.

• Breathing air with ETS is called “involuntary or passive smoking”.

• ETS causes lung cancer and other disorders.

INDOOR AIR QUALITYASBESTOS:• Asbestos is a common name for a group of

naturally occurring fibrous silicate minerals that are made up of thin but strong durable fibers. Because of its tensile strength and heat resistant properties, asbestos has been used extensively in building materials such as ceilings, insulation and tiles, automobile clutch and transmission parts and heat resistant fabrics.

INDOOR AIR QUALITYASBESTOS:• Asbestos is a mineral and is relatively stable in

the environment unless they are disturbed. Natural weathering or upon damage or disturbance of asbestos-containing products, the microscopic fibers become airborne and can be inhaled into the lungs or ingested with contaminated food where they can cause significant health problems.

Asbestos

INDOOR AIR QUALITYAsbestos:• It is Hazardous air pollutants. Asbestos is

dangerous when it is crushed, crumbled or disturbed because fibers can be released into the air.

• It is used to be a common building material found in structural fireproofing, heating-system insulation, floor and ceiling tiles, roofing felts and shingles.

INDOOR AIR QUALITYAsbestos:• Used in consumer products such as fireplace

gloves, and certain hair dryers.• If these materials damage, microscopic fibers

may be dispersed into the indoor air environment.

• Inhalation of these fibers can lead to diseases including asbestosis, lung cancer and mesothelioma.

INDOOR AIR QUALITYASBESTOS:• Asbestos exposure along with tobacco smoke

elevates the lung cancer risk by approximately fivefold.

INDOOR AIR QUALITYRADON: It is second leading cause of lung

cancer after smoking.• Sources are diffusion from soil, ground water

and building materials such as brick, concrete, and tiles.

• Radon itself is inert but its short-lived decay products-Polonium, lead, and bismuth-are chemically active and easily become attached to inhaled particles that can lodge in the lung.

INDOOR AIR QUALITYRADON:• Indoor air can be exchanged with outdoor air by

any combination of following three mechanisms.• Radon is a naturally-occurring, invisible and

odorless radioactive gas. One in 15 American homes contains high levels of radon. Millions of Americans are unknowingly exposed to this dangerous gas. Radon gas causes more deaths every year than fires and carbon monoxide combined.

INDOOR AIR QUALITY• (1) Infiltration: Natural air exchange, when doors

and windows are closed. Air exchange happens by leakage through various cracks and holes in building.

• (2) Natural Ventilation: Air exchange, when windows or doors are purposely opened to increase air circulation.

• (3) Forced Ventilation: Air exchange using fans or blowers by mechanical handling systems.

chapter 2; air pollution

Education

overview of emissions

overview of emissions

overview of emissionsnox

air pollutants

stationary fuel combustion

miscellaneous sources

air n2

introduction air pollution