Exam 2 - Environmental Science

atmosphere

the layer of gases that envelop our planet and performs many important functions

Atmospheric composition of gases

nitrogen 78% , oxygen 20% , water vapor 0%-4%

Air pollution

any gas or particulate matter that can affect climate or harm people or other organisms

Anthropogenic

sources of air pollution that derive from human activities or natural processes

Primary pollutants

compounds emitted directly into the air

Secondary pollutants

created in the atmosphere through chemical reactions involving primary pollutants, often triggered by sunlight

point sources

industrial smokestacks and coal-burning power plants (i.e., they are stationary and easily identifiable)

non-point sources

motor vehicles (they are not as easy to identify)

Primary pollutant examples

sulfur dioxide (SO2), nitrogen dioxide (NO2), suspended particulate matter (PM), lead (Pb), and carbon monoxide (CO)

Secondary pollutant example

tropospheric ozone (aka ground-level ozone) is a secondary pollutant formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react with sunlight to form O3

Clean Air Act

Requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to the public’s health and the environment

EPA

Environmental Protection Agency

NAAQS

National Ambient Air Quality Standards

Primary standards

set limits on pollutants to protect public health, especially the health of sensitive populations such as children, the elderly, and those that suffer from asthma

Secondary standards

have limits that protect public welfare, things like protection against decreased visibility and damage to crops and vegetation

principal or criteria pollutants (6 criteria pollutants)

NO2, SO2, Pb, PM, CO, O3

Nitrogen oxides (NOx)

group of gases that contain nitrogen (N) and oxygen (O) in varying amounts

How are nitrogen oxides (NOx) formed?

when fuel is burned at a high temperature

What forms a reddish brown layer over cities?

Nitrogen dioxide

What is one of the main ingredients in forming ozone and acid rain?

Nitrogen dioxide

How is sulphur dioxide (SO2) formed?

formed when fuel containing sulfur is burned (coal and oil)

What dissolves in water to form an acid?

sulphur dioxide

What is the biggest contributor to sulphur dioxide?

power plants

What is the biggest contributor to nitrogen oxides?

vehicles and power plants

Lead (Pb)

major source used to be from vehicles, but metals manufacturing is

now the major source since gasoline is unleaded

Particulate matter (PM)

small particles and liquid droplets

-can be ash, soil, dust

How is carbon monoxide (CO) formed? Where does it come from?

-formed when carbon in fuel is incompletely burned

-mostly from vehicle emissions, but can also come from forest fires and combustion of fuel in homes

Ozone (O3)

-most problematic pollutant for air quality in U.S. (and Texas!) because it regularly exceeds NAAQS limits

-secondary pollutant

Where does the ozone occur?

troposphere and stratosphere

Ozone effect on stratosphere

critical to life on Earth because it screens out harmful ultraviolet radiation from the sun

Ozone effect on troposphere

pollutant with significant consequences for human health

tropospheric ozone formation

NOx and VOCs react in the atmosphere in the presence of sunlight

ozone precursors

Primary pollutants have to be emitted first before tropospheric ozone can form

smog

reddish-brown haze that forms when air quality is particularly poor

formation of ground-level ozone (photochemical smog) - simplified process

1. NOX and/or VOC is broken down by sunlight

2. Atomic O joins with O2

3. Forms O3

• Need hot weather and sunlight = “summertime pollutant”

Scrubbers (in coal-burning power plants)

air pollution control devices that use a chemical reaction to reduce SO2 by up to 90%

Most polluted countries

China and India

Why is the WHO so focused on PM2.5?

It is commonly accepted as the most harmful to human health due to its prevalence in the environment and broad range of health effects

Acid rain

Precipitation with elevated acidity (low pH) formed when sulfur dioxide (SO2) and nitrogen oxides (NOx​) react with water and oxygen in the atmosphere to produce sulfuric and nitric acids.

What does acid rain result mostly from?

the transformation of SO2 and NOx into secondary pollutants such as sulfuric acid (H2SO4) and nitric acid (HNO3)

Wet deposition

occurs when atmospheric gases and particles are removed and brought to the Earth’s surface by precipitation

ex. acid rain, fog, and snow

Dry deposition

SOx and NOx particles are deposited onto surfaces; driven by gravity and wind rather than precipitation

What is wet and dry deposition?

The two primary natural processes that remove gases, aerosols, and particulate matter from the atmosphere and transfer them to the Earth's surface

What is the ozone layer or stratospheric ozone?

contains 90% of all atmospheric ozone, acts as primary radiation shield

Ultraviolet (UV) radiation

destructive to genetic cellular material in all organisms; biologically harmful to plants, animals, and humans

Antarctic ozone hole

thinning in ozone that occurs over Antarctica each spring (Aug, Sep, Oct)

Arctic ozone depletion

weaker than hole (Jan, Feb, March)

What causes antarctic/arctic ozone depletion/hole?

human made chlorofluorocarbons (CFCs)

What happens in the stratosphere of the tropics?

Stratospheric ozone is formed naturally

What is involved in the process of ozone generation?

splitting and combination

STEP 1 of ozone generation

O2 is split into 2 O molecules by incoming UV radiation

STEP 2 of ozone generation

Single O combines with O2 to form O3

What are ozone levels measured in?

Dobson Units (DU)

______ total ozone means _______ UV light penetration

less; more

selective gas

absorbs and emits radiation only at specific wavelengths (CO2)

UV-C

most hazardous; ozone absorbs most of it

UV-B

raises risk of skin cancer, weakened immune system and can harm plants, aquatic ecosystems; ozone absorbs most of it

UV-A

radiation can lead to premature skin aging

broad spectrum protection

shields against both UV-A (wrinkles) and UV-B (sunburn, skin cancer)

What UV rays does the ozone absorb?

UV-C and some UV-B

Ozone Depleting Substances (ODS)

initial step in ozone depletion is the release of these gases; contain chlorine and bromine

chlorofluorocarbons (CFCs, freons)

nontoxic alternative to dangerous substances for use in spray cans and refrigeration

What starts the ozone destruction cycle?

UV radiation can break apart the original CFC molecules once in the stratosphere

Reservoir gases (start ozone destruction cycle)

do not react directly with ozone but provide a chlorine reservoir for later ozone destruction

How are reservoir gases transported? Where?

wind currents; poles

When does Antarctica experience an onset of winter?

mid-March

vortex

a spinning mass of fluid, air, or water that rotates rapidly around a central axis

polar vortex

Throughout the winter polar night, sunlight doesn't reach the South Pole; temperatures plummet to extremely low levels

Polar Stratospheric Clouds (PSCs)

when temperatures during the cold polar vortex reach a certain point

molecular chlorine (Cl2)

builds up in stratosphere from reservoir gases during polar winter when PSCs form

free chlorine (Cl)

necessary to destroy ozone; only available when sunlight is present to break down the molecular chlorine (Cl2)

What happens when sunlight returns to the polar region with the onset of the southern hemisphere spring (August)?

Cl2 is rapidly split by the sunlight into free chlorine atoms that quickly attack and destroy ozone molecule

ozone minimum

ozone at its thinnest

When does ozone minimum occur?

end of September/early October; when the sun is fully above the horizon, even at the South Pole

Arctic vs. Antarctica temperatures

Lowest temperatures found in the Arctic are much higher than in Antarctica

catalyst for ozone destruction

chlorine

catalyst

speeds up chemical reactions without getting broken down in the process

Antarctic ozone hole stops expanding

until temperatures rise and the polar vortex weakens

Montreal Protocol

restricts CFC production

global warming

The increase in Earth's average surface temperature, largely caused by human emissions of greenhouse gases.

climate change

Long-term changes in Earth's climate, including temperature, precipitation, and sea levels.

GHGs (greenhouse gases)

Gases in the atmosphere that absorb and re-emit heat, helping regulate Earth's temperature.

tropical regions

Areas near the equator that receive relatively large amounts of solar energy.

polar regions

Areas near the North and South Poles that receive relatively little solar energy.

albedo

The amount of incoming solar radiation reflected by a surface.

reflectivity

A surface's ability to reflect incoming radiation rather than absorb it.

convection currents

The movement of warm air or fluid upward and cooler air or fluid downward, transferring heat.

water vapor

Water in its gaseous state in the atmosphere; it is also a greenhouse gas.

longwave radiation

Heat energy emitted by Earth's surface, primarily in the form of infrared radiation.

greenhouse effect

The process in which greenhouse gases absorb and re-emit heat, keeping Earth warmer than it would otherwise be.

selective gases

Gases that absorb only certain wavelengths of radiation.

sources

Places or processes that release carbon into the atmosphere. Examples include burning fossil fuels and respiration.

sinks

Places or processes that absorb and store more carbon than they release. Examples can include forests and oceans

Mauna Loa Observatory

A research observatory in Hawaii where scientists have measured atmospheric carbon dioxide since the 1950s.

keeling curve

The long-term record showing the rise in atmospheric carbon dioxide concentrations, based on measurements begun by Charles David Keeling in 1958.

Parts per million (ppm)

A unit used to measure the concentration of a substance. For example, 426 ppm means 426 parts of CO₂ per million parts of air.

ice cores

Cylinders of ice containing trapped air bubbles that scientists analyze to learn about past atmospheric conditions.

Antarctica

The continent surrounding the South Pole, where ice cores provide evidence about past climates, contains most of Earth’s freshwater ice

industrial revolution

The period when industrialization and fossil fuel use expanded significantly, increasing human emissions of carbon dioxide.

fossil fuels

Coal, oil, and natural gas formed from ancient organic material; burning them releases carbon dioxide.