EnviSci Midterm Reviewer Flashcards
A mixture of different gases in the atmosphere.
Air
Earth’s air is composed of about how many percent?
78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, and 0.1 percent other gases
The origin of air begins with the Oxygen Catastrophe, also known as the __________, which occurred about 2.7 billion years ago.
Great Oxidation
Microorganisms that perform ___________ lessen the presence of carbon dioxide in the atmosphere.
Oxyphotosynthesis
It is the horizontal motion of air due to the pressure difference between two places.
Wind
It is a suspension of fine solid particles or liquid droplets in air or another gas.
Aerosol
Aerosols such as fog, dust, and mist.
Natural Aerosols
Aerosols such as Particulate air pollutants, Smoke, Sprayed Pesticides
Anthropogenic Aerosols
These tiny microbial organisms found in the air that can travel long distances through the air—via wind, rain, or even a sneeze!
Bioaerosols
During _________, a living thing takes in oxygen from the air and gives out carbon dioxide.
Respiration
Introduction of harmful materials into the environment
Pollution
The contamination of the indoor or outdoor environment by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere.
Air Pollution
Air pollution is the ____ largest threat to human health.
4th
Breathing polluted air can reduce life expectancy by up to how many years?
2 years
Sources of Air Pollution including dust from places without vegetation, animals, vegetation, wildfires, and volcanic activity.
Natural Sources
In large areas of open land that have little to no vegetation and are particularly dry due to a lack of precipitation, wind can naturally create dust storms.
Dust from places without vegetation
Their digestion is another cause of natural air pollution, leading to the release of methane, another greenhouse gas.
Animals (particularly by cattle)
Vegetation – such as black gum, poplar, oak, and willow trees – emits significant amounts _______ of on warmer days.
Volatile organic compounds (VOCs)
These react with primary anthropogenic pollutants – specifically nitrogen oxides, sulfur dioxide and carbon compounds – to produce low-lying seasonal hazes that are rich in ozone.
Volatile organic compounds (VOCs)
This particulate matter, when added to the air, can have a natural warming effect and can also be a health hazard for living creatures.
Dust from places without vegetation
Are a natural occurrence in wooded areas when prolonged dry periods occur, generally as a result of season changes and a lack of precipitation.
Wildfires
The ________ caused by these fires contribute to carbon levels in the atmosphere, which allows for greater warming by causing a Greenhouse Effect.
Smoke and Carbon Monoxide
Are a major source of natural air pollution that produces tremendous amounts of sulfuric, chlorine, and ash products, which are released into the atmosphere and can be picked up by winds to be dispersed over large areas.
Volcanic eruptions
Sources of Air Pollution including environmental tobacco smoke, wood stoves and gas ranges, building materials, asbestos, radon, and biological agents.
Domestic Sources
It is a major air pollutant and one of the most dangerous of all.
It is a leading cause of indoor air pollution.
Environmental tobacco smoke (ETS)
When not properly maintained and vented, they emit noxious substances including Carbon monoxide, Oxides of nitrogen, Particulates, and Hydrocarbons.
Wood stoves
________ may produce nitrogen oxide.
Gas ranges
Potentially important sources of Indoor Air Quality contaminants, which can contain contaminants that are gradually emitted throughout the life of the material.
Building Materials
It is the name given to a group of naturally occurring minerals that are resistant to heat and corrosion.
Asbestos
It is a radioactive gas that has no smell, color or taste.
Radon
The most common source of indoor radon is ________ in the soil or rock on which homes are built.
Uranium
These include bacteria, molds, viruses, animal dander and saliva, dust mites, cockroach parts, and pollens.
These pollutants can travel through the air and are not always easy to see.
Indoor biological pollutants
Sources of air pollution including pesticides and fertilizers, emissions from tractors and farm vehicles, and deforestations.
Agricultural Sources
They emit pollutants such as hazardous air pollutants (HAPs) and Volatile Organic Compounds (VOC). These pollutants can contribute to health problems that may affect residents, the neighborhood, and the community.
Pesticides and Fertilizers
During clearing and working large parts of the land, they emit CO2 from the burning of diesel fuel.
Emission from Tractors and Farm Vehicles.
It refers to the purposeful clearing of forested land.
Deforestation
World water day
March 22
Sources of air pollution including electricity, fragrance, and biomass.
Commercial Sources
Most mechanisms for generating ________ release carbon dioxide and other greenhouse gases.
electricity
Gases that absorb and emit radiation into Earth’s atmosphere.
Greenhouse Gases
Primary source of indoor air pollutants which is a formulation of dozens of chemicals, such as volatile organic compounds (VOCs).
Fragrance Products
Examples are ethanol, alpha pinene, acetone, limonene, beta pinene and acetaldehyde which are considered indoor air pollutants.
Volatile organic compounds (VOCs)
Smoke from __________ combustion produces a large number of health-damaging air pollutants including respirable particulate matter, carbon monoxide (CO), nitrogen oxides, formaldehyde, benzene, 1,3 butadiene, polycyclic aromatic hydrocarbons (such as benzo[a]pyrene), and many other toxic organic compounds.
Biomass
Sources of air pollution including oil and gas, petrochemical plants, steelmaking, and hazardous wastes.
Industrial Sources
Every stage of ________ operations, from production and extraction to processing and distribution, releases air pollution that negatively affects public health and exacerbates the climate crisis.
Oil and gas
They are major source of hazardous and toxic air pollutants such as BTEX compounds (benzene, toluene, ethylbenzene, and xylene).
They are also a major source of criteria air pollutants: particulate matter (PM), nitrogen oxides (NOx), carbon monoxide (CO), hydrogen sulfide (H2S), and sulfur dioxide (SO2).
They release less toxic hydrocarbons such as natural gas (methane) and other light volatile fuels and oils.
Petroleum refineries
Steel particularly requires coal for energy, so a lot of emission is caused by ________ .
coal combustion
________ emit air pollutants such as particulate matter (PM2. 5 and PM10), carbon dioxide, Sulphur oxides, nitrogen oxides, carbon monoxide, etc.
Steel plants
These are released from activities such as: burning waste (including plastics, medical and hazardous waste) smoking, and using solvent base paints.
Hazardous air pollutants
Generates the largest share of greenhouse gas emissions.
Transportation sector
The most common include lead (Pb), carbon monoxide (CO), nitrogen oxides (NOx), silicon tetrafluoride (SF6), benzene and volatile components (BTX), heavy metals (zinc, chrome, copper, and cadmium), and particulate matters (ash, dust).
Transportation-related sources
A mixture of solid particles and liquid droplets found in the air.
Particulate Pollutants
Are particulate matter smaller than 10 micrometers in diameter.
PM10
Are particulate matter smaller than 2.5 micrometers in diameter.
PM2.5 (or fine particles)
True or False. PM does not include gas pollutants like ozone and NO2.
True
Emissions from combustion of gasoline, oil, diesel fuel or wood produce much of the ______ pollution found in outdoor air.
PM2.5
also includes dust from construction sites, landfills and agriculture, wildfires and brush/waste burning, industrial sources, wind-blown dust from open lands, pollen, and fragments of bacteria.
PM10
For materials that are hazardous when deposited anywhere in the respiratory tract.
Inhalable Particulate Mass-TLVs
Assigned to materials that are hazardous when deposited anywhere within the lung airways and the gas-exchange region (the lower airways passages).
Thoracic Particulate Mass-TLVs
For particulates that are small enough to reach the gas exchange region and are hazardous only if they are deposited in that region.
Respirable Particulate Mass-TLVs
Colorless, odorless, tasteless gas. Also known as the “silent killer “
Effects on human health include Cardiovascular and Neurological Effects, Headaches, Nausea, Fatigue, Death.
Carbon Monoxide CO
A mixture of gases that are composed of nitrogen and oxygen. Produces smog (Ozone) when reacting with Volatile Organic Compound (VOCS)
Effects on human health include Pulmonary Fibrosis, Emphysema, Lower respiratory trach illness, inflammation and irritation of breathing passages.
Nitrogen Oxides
Ozone is a gas composed of three atoms of oxygen. Occurs both in the earth’s upper atmosphere and at ground level.
O3
Is a colorless gas with a pungent odor. Is a liquid when under pressure, and it dissolves in water very easily.
Effects on human health include Bronchoconstriction and Burning of the nose and throat.
Sulfur Dioxide SO2
Is a naturally occurring bluish-gray metal found in small amounts in the earth’s crust.
Effects on human health include adverse effects on nervous, kidney, immune, reproductive, and cardiovascular systems and can stall mental development in children.
Lead Pb
A naturally-occurring chemical element found in rock in the earth’s crust, including in deposits of coal.
Three types found in the environment are elemental (metallic), methylmercury, other organic compounds, and inorganic.
Effects on human health include Loss of peripheral vision; “Pins and needles” feelings, usually in the hands, feet, and around the mouth; Lack of coordination of movements; Impairment of speech, hearing, and walking; Muscle weakness.
Mercury Hg
Colorless, odorless gas that occurs abundantly in nature and as a product of certain human activities.
Is among the most potent of the greenhouse gases.
Also contributes to the formation of smog.
Methane CO4
Includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic.
Acid rains
A wear mechanism that is caused by the inclusion of hard particles between two sliding or rolling surfaces.
Abrasion
Laying down of sediment or particulate matter on the surfaces of materials.
Deposition and Removal
Is the process of substances reacting directly with another material that results in chemical degradation or change.
Direct Chemical Attack
Is the process of substances reacting indirectly with another substance, which in turn, results in a new substance that could then directly damage said materials.
Indirect Chemical Attack
A chemical or electrochemical reaction which results in the degradation of materials that is almost unique to metals.
Corrosion
The techniques employed to reduce or eliminate the emission into theatmosphereof substances that can harm theenvironmentor human health.
Air pollution control
Mainly aimed at correction right at the source so there will be lesser amount of pollutant emitted.
Examples such as:
- Using natural gas in place of coal for power generation
- Using LPG/CNG instead of diesel or petrol in automobiles
Preventive Measures
The most common method of eliminating/reducing pollutants to an acceptable level which includes:
- Collecting the pollutants by using equipment
- Destroying the pollutants by thermal or catalytic combustion
- Changing the pollutant to less toxic form
Control Measures
___________ of pollutants by wind reduces the concentration of air pollutants at one place although it does not remove them from the environment as a whole.
Dispersion
The most important natural mechanism, under which large heavy particles from ambient air settles down on buildings, trees, and other objects. This generally happens for the particles which are 50 µm in size.
Gravitational Settling
This process also helps in removing flocculated particles formed by uniting of smaller particles over larger particles, till a floc particle, large and heavy enough to settle out under gravity is formed.
Gravitational Settling
The gaseous as well as particulate pollutants from the air get collected in the rain or mist and may settle out with that moisture. This phenomenon takes place below the cloud level, when falling raindrops absorb pollutants, and is also known as washouts or scavenging. However, it does not help in removing particles smaller than 1µm in size.
Absorption
The gaseous pollutants are removed in a dissolved state with moisture, either with or without chemical changes.
Absorption
The process involving precipitation above the cloud level where submicron particles present in the atmosphere in the cloud serve as condensation nuclei around which drops of water may form and fall out as raindrop.
Rainout
This phenomenon helps in increased rainfall and fog formation in urban areas, containing huge quantity of such particles, raising high above the cloud level.
Rainout
The phenomenon in which the gaseous, liquid, or solid pollutants present in the ambient air are kept attached, generally electrostatically by a surface where they are concentrated and retained.
Adsorption
A measure of how clean or polluted the air is. It is measured with the air quality index, or AQI.
Air quality
This works sort of like a thermometer that runs from 0 to 500 degrees. However, instead of showing changes in the temperature, it shows changes in the amount of pollution in the air.
AQI
It can track five major pollutants including Ground-level ozone, Carbon monoxide, Sulfur dioxide, Nitrogen dioxide, Airborne particles, or aerosols
AQI
It is the control of the level of pollutants prescribed by regulations that is a set of specific techniques and measures identified and implemented to achieve reductions in air pollution to attain an air quality standard or goal.
Air Quality Control
Refers to all the activities a regulatory authority undertakes to help protect human health and the environment from the harmful effects of air pollution.
Air quality management
Are tiny particles and droplets in the air that are made up of hundreds of different chemicals.
Particulate emissions
What does EPA stand for?
Environmental Protection Agency
Used to remove particles with size greater than 50 µm.
Gravitational Settling Chamber
- Low initial cost
- Simple to design
- Low pressure drop
- Low maintenance cost
- Dry and continuous disposal of solid particulates
Advantages of Gravitational settling chamber
- Collection of efficiency can be increased by providing the baffles and horizontal tray in the chamber to reduce the settling path
- Usually used for removal of large solid particulates
Disadvantages of Gravitational Settling Chamber
CF is utilized to separate the particulate matter from the gas. As CF is much greater than gravitational force, smaller particles can be removed (10 – 50 µm).
Centrifugal Collectors
A is a specially designed closed chamber, in which the velocity of the inlet gas is transformed into spinning vortex and the particles from the gas are thrown out under the centrifugal force.
Cyclone separator
- Low initial cost
- Requires less floor area
- Low to moderate pressure loss (2.5–20 cm)
- Simple construction and maintenance
- Dry continuous disposal of collected dust
- Handles large volume of gas at high temperature
Advantages of Centrifugal Collectors
- Requires large head room
- Less efficiency for smaller particles
- Severe abrasive deterioration
- Sensitive to variable dust load and flow rates
- Usually used in industries producing larger quantities of gas containing larger sized particles
Disadvantages of centrifugal Collectors
It works on the principle of electrical charging of the particulate matter and collecting it on a differently charged collecting surface. It has a very high efficiency of about 99% and can remove particles in the size of 0.1 µm to 1 µm efficiently.
Electrostatic Precipitators
- High collection efficiency
- Particles may be collected dry or wet
- Can be operated at high temperature
- Maintenance is nominal
- Few moving parts
- Treatment time is negligible
Advantages of Electrostatic Precipitators
- High initial cost
- Uses high voltage
- Possible explosion hazards
- Collection efficiency reduces with time
- More space requirement
- Widely used in thermal power plants, cement factories, iron and steel industries, mining, etc.
Disadvantages of Electrostatic Precipitators
It outs the particulate matter from the gas stream and allow clear gas to flow. In such a system, the flue gas is allowed to pass through a woven or felted fabric which filters out the particulate matter and allows the gas to pass. It can remove particles up to 1 µm.
Fabric filters
- High collection efficiency for all particle sizes
- Performance decrease becomes visible
- Nominal power consumption
- Dry disposal of collected particles
Advantages of Fabric Filters
- High temperature gases need to be cooled to the range within which filter are stable
- High maintenance and fabric replacement cost
- Large size equipment
- Fabric is liable to chemical attack
Disadvantages of Fabric Filters
Particulate matter are incorporated into liquid droplets and thus are removed from the gas stream. Flue gas is made to push up against a down falling water current. The particulate matter mixes up with water droplets and thus, falls down and get removed.
Scrubbers
Three types of scrubbers
- Spray towers
- Venturi scrubbers
- cyclone scrubbers
- Simultaneously removes particulate and gaseous pollutants
- Cools hot gases
- No particles re-entrainment
- Recovers and neutralizes corrosive gases
Advantages of Scrubbers
- Produces a lot of wastewater
- Wet outlet gases cannot rise from the stack
- Poses freezing problems in cold countries
- Maintenance cost is high
Disadvantages of Scrubbers
It includes the following:
- Limiting emissions from stationary sources
- Choice of fuel
- Combustion control
- Process modifications
- Modifications in operating conditions
Nitrogen Oxide Emission Control
Means avoiding the stoichiometric ratio (the exact ratio of chemicals that enter into reaction)
NOEC Method 1: Reducing Temperature
At high combustion temperatures can be done by ignition or injection timing with internal combustion engines.
NOEC Method 2: Reducing Residence Time
This technique provides a chemically reducing (i.e., reversal of oxidation) substance to remove oxygen from nitrogen oxides.
NOEC Method 3: Chemical Reduction of NOx
This technique intentionally raises the valence of the nitrogen ion to allow water to absorb it.
NOEC Method 4: Oxidation of NOx
This is accomplished by removing of nitrogen as a reactant either by: (1) using oxygen instead of air in the combustion process; or (2) using ultra-low nitrogen content fuel to form less fuel NOx.
NOEC method 5: Removal of Nitrogen From Combustion
Treatment of flue gas by injection of sorbents (such as ammonia, powdered limestone, aluminum oxide, or carbon) can remove NOx and other pollutants (principally sulfur).
NOEC Method 6: Sorption, both adsorption and absorption.
Many of these methods can be combined to achieve a lower NOx concentration than can be achieved alone by any one method.
NOEC Method 7: Combinations of NOEC methods
