Chemicals In the Environment

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Chemicals In the Environment
All matter in our environment is made of
chemicals. Chemicals are a part of both the
biotic and abiotic parts of any ecosystem.
Limestone (calcium carbonate) shapes the
landscape in many places in North America. Some
forms of limestone becomes marble with unique
qualities that make it great for for making
sculptures.
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Water is our most plentiful compound on earth.
Much of all life are made from water and depend
on water to maintain life. Sea water contain
many other dissolved chemicals that other
organisms depend on getting. Many of these are
what give ocean water its salty taste.
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Living organisms produce chemicals and use their
own chemicals. This mushroom produces a toxin
that destroys your liver. Eating the cap of this
mushroom is fatal.
These newts produce a toxin so deadly that when
predators attack, they roll over and display
their bright stomachs to warn them that if they
are eaten they are deadly. However, there is a
species of snake that produces a chemical to
neutralize the poison.
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Organic chemicals are produced by organisms.
They are usually molecular compounds that contain
carbon. Inorganic compounds are found naturally
on earth and are usually ionic compounds or
elements (with the major exception of
water). Organisms need both organic and inorganic
compounds to survive. The organic compounds we
need are called nutrients. Organisms get their
nutrients by either consuming them from the
environment or by breaking down molecules they
consume to release the needed nutrients. If we
need a lot of a certain nutrient it is called a
macronutrient. If we dont need as much of a
nutrient it is a micronutrient.
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There are 4 main categories of organic nutrients
we needcarbohydrates, proteins, lipids, and
vitamins.
Carbohydrates such as starch from potatoes and
flour made from wheat are energy sources in your
body. We need a certain level of starch to
survive.
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Proteins found in meats, eggs, beans, and legumes
are necessary for their amino acids. Amino acids
are important compounds for making all kinds of
and enzymes and other proteins that the body
needs.
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Lipids from things like oil, milk, cheeses,
butter, nuts and many others, act as long term
storage of energy. We also use lipids in making
cells as well as other useful chemicals.
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Vitamins are found in almost every food source.
They are especially rich in green leafy
vegetables like spinach, broccoli and other mixed
greens.
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Minerals are the inorganic elements and compounds
that we need to consume because we cannot make
them on our own. Minerals are categorized into 2
groups depending on how much we need to consume
in a day. If you need 100mg/day or more then it
is a macromineral. If you need 100mg/day or less
then it is a trace element. Trace elements are
just as important as macrominerals. Just because
you need less doesnt mean you wont die without
it.
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Here are just a few macrominerals and trace
elements we need to consume and their function in
our bodies.
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Humans depend on plants and the minerals they
take up from the soil through their roots. The
following charts shows a few elements and the
approximate (by mass) that the make up in the
earths crust, in plants, and in humans.
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Nitrogen is a very important chemical to living
things. There is a lot of nitrogen in the air.
The problem is that organisms cant use the
nitrogen in the form N2(g). The nitrogen has to
be fixed. Nitrogen fixation means taking
atmospheric nitrogen and putting it into other
molecules that can be used by organisms.
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The nodules (bumps) on this soy bean plant are
the home for a species of bacteria that are
capable of taking nitrogen from the air and
fixing it into organic molecules. All types of
nitrogen fixing bacteria are responsible for the
majority of the fixed nitrogen in the soil. In
this case the bacteria and the soy bean plant
form a relationship of mutualism. The bacteria
get a good stable home and the plant gets organic
nitrogen to help grow.
This is an electron micrograph of a Rhizobium
bacteria. It is one of the species that fixes
nitrogen around the roots of plants.
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Lightning also causes some nitrogen fixation.
Once nitrogen is fixed it is take up by plants or
eaten by animals and returned to the ground in
manure. Some bacteria take fixed nitrogen and
return it back to the atmosphere.
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When our lawns or farm fields dont have the
nitrogen or other minerals needed for healthy
plants we use commercial fertilizers.
A fertilizer will add some of the needed
chemicals for plants to grow. This bag shows us
that there is 29 nitrogen (fixed), 3
phosphorus, and 4 potassium. Nitrogen is needed
to grow green leafy parts of the plant.
Phosphorus is needed to grow roots. Potassium is
needed for the plant to flower.
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Commercially used fertilizers often run off in
rain water to lakes and ponds. The added
nutrients make it very easy for some species of
algae to grow. The massive increase in life in
the lake causes the oxygen levels to go down in
the water making it difficult for species who
depend on oxygen to live. The species of algae
that are resistant to low oxygen thrive and take
over the ecosystem.
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Pesticides are chemicals that are used to control
species that interrupt our activities.
Mosquitoes are an example of a pest that was
controlled by a chemical called DDT.
This is a picture of DDT being sprayed over farm
animals to control mosquitoes. Mosquitoes helped
transmit diseases and were an irritant to
livestock. It is doubtful now that any farmer
would spray their herds like this.
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The more DDT that was sprayed, the more
mosquitoes developed adaptations to resist the
pesticide. Now, many pesticides no longer work
against these pest species.
This adaptation to pesticides is called
resistance. This chart shows how the number of
resistant pest species has dramatically increased
in the past few years.
19
Acids and bases are reactive chemicals dissolved
in water. They are very important chemicals to
us and our environment. The pH scale measures
the acidity or alkalinity of compounds. A ph of
7 is called neutral. Pure water has pH of 7.
Other common compounds are shown here.
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Determining an acid from a base is difficult.
Both are reactive substances. Acids (like lemon
juice) are sour tasting but it is not acceptable
to taste an unknown liquid in a science lab.
Bases (like soap) are slippery, but we shouldnt
touch chemicals with our bare hands in a lab
either. Indicators have been developed so that
we can test whether a substance is acidic or
basic. Litmus paper is a common quick indicator
test.
There are two types of litmus paperred and blue.
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An acid will turn red litmus paper red and blue
litmus paper red.
A base will turn red litmus paper blue and blue
litmus paper blue.
A neutral substance will turn red litmus paper
red and blue litmus paper blue.
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These pH papers will also test for acids and
bases but you will actually get an approximate pH
value. Litmus paper only tells you whether the
substance is acidic, basic, or neutral.
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There are also pH meters that can give you a
quick accurate pH of a solution. These meters
are quite expensive and difficult to maintain.
They can also be more expensive to use over
litmus papers or pH paper.
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One common ecological issue dealing with acids
and bases is acid precipitation. There are 4
main reactions that occur in the atmosphere that
contribute to acid precipitation.
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This map show the areas currently effected by
acid precipitation.
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Neutralization is the process where an acid
reacts with a base. For example, hydrochloric
acid reacts with sodium hydroxide to produce
water and sodium chloride (table salt). HCl(aq)
NaOH(aq)? H2O(l) NaCl(aq) acid
base water ionic
salt All neutralization reactions produce an
ionic salt and water. We use calcium rich
tablets to help neutralize our stomach acid when
there is an excess of acid causing heartburn.
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Chemicals and Organisms
We have already seen that plants and animals need
nutrients and minerals to survive. But how do
they get these substances? How do they also make
sure that they dont escape after they have been
acquired? Plant use their roots and leaves to
absorb their nutrients and minerals.
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The cells are the root hairs use semi-permeable
membranes to let substances in and not let in
others. When a substance moves from an area of
high concentration to an area of low
concentration, the movement is called diffusion.
Diffusion is passive transport of materials
because it requires no work from the cell.
Diffusion naturally happens.
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When water moves across a membrane through
diffusion the process is called osmosis.
Here the blue water molecules are in relatively
low concentration on the left. There is a lower
concentration of water on the right. Through
osmosis, the water moves to the right side of the
membrane. This effect can be dangerous to some
cells. If red blood cells are put in pure water,
the water will rush into the cell through
osmosis. This cause the cell to swell and burst.
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Sometimes, diffusion would work against the root
cells. This would happen if there were a higher
concentration of some compound inside the cell
compared to the outside. Cell membranes then use
special proteins and energy to pump chemicals
in. When the cell uses energy to consume
something it is called active transport.
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Animals like lions need to ingest their food.
After they eat another organism, they break it
down mechanically and chemically. This chemical
break down is called hydrolysis since the food is
broken down with water (and many other
chemicals). When a chemical is broken down
through hydrolysis it is said that the chemical
was hydrolyzed.
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We have seen that fertilizer runoff can effect
the organisms in a lake. So clearly, lakes with
a lot of green algae have water we wouldnt want
to drink.
But water clarity is not the only thing that
determines the water quality. A lake that has
been poisoned may be absolutely clear because it
lacks the ability to support life.
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Biological indicators such as mosquito larva and
other insects, fish, bacterial and algae species
can shed light on the water quality of a lake.
Each species has a specific tolerance to
different levels of water quality. If only very
sensitive species are not found in the lake, then
the water quality may be quite good. If very
resistant species start decreasing in number,
then it might be due to decreasing water quality.

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The chemical imbalance in a lake can be altered
by point sources and non-point sources. A point
source means that the pollutant is coming into
the lake at one location such as a drain pipe. A
non-point source means that a location cannot be
determined as the source of pollution. Runoff is
likely occurring from an agricultural field or
city.
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The pH of the water in a lake is another good
indicator of water quality. Acid precipitation
can make a lake more acidic and lower its pH to
levels that are dangerous to organisms. If acid
precipitation builds up during winter, the spring
melt could drastically lower the pH of a lake
quickly. This is called the spring acid
shock. Other chemicals can influence the water
quality. Dissolved oxygen, heavy metals,
nitrogen, phosphorus, pesticides, and ionic salts
are all possible measures of water
quality. However, there is a lot of water in a
lake and all of these chemicals would exist in
very small quantities. To discuss these
chemicals, scientists use the measure parts per
million (ppm).
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How many ppm of salt are in 2 kg of water if you
added 14mg of salt?
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Most organisms need about 5 ppm (5 mg/L) of
dissolved oxygen to survive. The water
temperature, turbulence, and the number and type
of organisms that live in the water all determine
the amount of dissolved oxygen.
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The toxicity is a measure of how dangerous a
substance is to organisms. We measure how toxic
a substance is with an LD50. LD stands for
lethal dose and 50 stands for 50 of an
exposed test group. There also has to be
standard ways to administer the toxin. Some
toxins only need to touch your skin where as
others need to be eaten. The lower the LD50 the
more toxic the substance.
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Heavy metals are also important chemicals. These
include mercury, copper, lead, zinc, cadmium and
nickel. These may not exist in large quantities
in a lake but could turn out to be quite a
problem because it is very difficult to brake
down and excrete these chemicals. Even trace
amounts could be a serious problem to predators
at the top of the food chain due to a process of
bioaccumulation.
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Bioaccumulation begins when small algae consume
one unit of mercury tainted nutrients. One in a
thousand algae carries mercury. One invertebrate
eats thousands of algae getting 4 units of
mercury. Then, small fish eat hundreds of
invertebrates gaining hundreds of units of
mercury. Then a big fish eats several small fish
gaining possibly toxic levels of mercury. As you
go up the food chain the level of mercury in a
single organism is amplified. In some lakes and
streams now, it is recommended that you not eat
the fish in the lake but the water is fine to
drink. The water has a low concentration of Hg
but the fish have a high level of mercury due to
bioaccumulation.
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Ground water can also be polluted. Under ground
water sources, called aquifers, are usually
filled with clean safe water but, dissolved
pollutants can concentrate in them.
The polluted water from the aquifer might them be
used to irrigate a farmers field transferring the
pollutants to the field.
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Chemical Waste Management
The smog seen here on the right is a common sight
around major industrial cities. Smog is air
pollution that is visible and looks like fog.
There are many different chemicals that
contribute to smog and it can make it difficult
to breath, especially on hot humid days.
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Sulfur oxides like sulfur dioxide (SO2(g)) are
mainly a product of burning fossil fuels like
coal, oil, and gas. They can contribute to smog
and to acid rain. This is a coal scrubber. Its
job is to remove as much of the sulfur compounds
from the burning process as possible so that the
sulfur oxides are not put back into the air.
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A coal scrubber works by reacting hot sulfur
dioxide (SO2(g)) with calcium oxide (CaO lime) to
make calcium sulfite (CaSO3(s)). The calcium
sulfite is a solid and make a slurry which can
then be filtered. The CaSO3(s) can be further
reacted to make CaSO42H2O(s) which is gypsum
(used in drywall).
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Nitrogen oxides are also a major component of
smog and acid precipitation. They are mainly
from the burning of gasoline in cars. This
hybrid car has an engine that is part gasoline
powered and part electrically powered. The
attempt is to use less fuel and produce
less air pollution.
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Carbon monoxide is produced when chemicals
containing carbon (like gasoline) are burned.
CO(g) is colorless and odorless but it will kill
you if you inhale enough of it. CO(g) detectors
are common around new homes. In is always
important to NEVER run a vehicle where there is
not sufficient ventilation like inside a closed
garage. CO(g) will make you dizzy, sleepy, or
before you pass out. Catalytic converters turn
CO(g) into the less dangerous CO2(g).
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Ozone (O3(g)) is an interesting chemical. In the
upper atmosphere, it protects us from the suns
UV light. The problem is that O3(g) is difficult
to make chemically speaking. CFCs
(Chlorofluorocarbons Cl3FC(g)) is a stable gas
that was thought to be a perfect propellant in
aerosol sprays. But, in the upper atmosphere,
CFCs react with the sun to break away a reactive
chlorine atom. The chlorine reacts with ozone
and breaks it into oxygen and chlorine monoxide.
An oxygen then comes are breaks the chlorine
monoxide releasing the free chlorine atom and
making O2(g). Hence, more reactive chlorine is
set to fly about breaking up more ozone molecules.
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The extent of the damage to the ozone layer is
quite extensive especially over the south pole.
The amount of ozone in the upper atmosphere is
measured by satellites.
This is a picture of the ozone layer from 1995
where the hole is clearly visible. We didnt
even notice there was a hole for years because
software sending messages back to earth were
designed to ignore readings that were thought to
be impossible. When we looked at all the data
this is what we saw.
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Since 1997, 81 countries have signed an agreement
to ban the use of CFCs. This has helped and the
ozone layer is slowly improving. Although
atmospheric ozone is a beneficial compound to us,
ground level ozone is a dangerous pollutant.
Ozone is toxic and is produce when oxygen,
nitrogen oxides, and volatile organic compounds
(VOCs, made from combustion of flues mostly)
react with heat and light. Ozone can be
hazardous to people with respiratory illnesses
and can also damage crops in a field. Some cities
now ozonate (treat with ozone) their water to
kill deadly bacterial spores.
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Carbon dioxide (CO2(g)) is found in the
atmosphere naturally. Our activities, such as
burning fossil fuels, have increased the amount
of atmospheric CO2(g). CO2(g) is a greenhouse
gas. This means that it helps to trap heat that
comes to the earth and regulate our temperature.
Water vapor, methane and nitrogen oxides are also
greenhouse gases. The increase in atmospheric
CO2(g) has caused an enhanced greenhouse effect.
More heat is trapped than what normally happens.
This is results in global warming.
Global warming can alter habitats however, the
effects are still not known exactly.
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Pollutant chemicals can be dissolved in water,
scattered as solid pieces on the ground, or
simply float off in the air. Dispersion of an air
pollutant can be difficult to track since the
scatter in all direction. Dilution is the process
where chemicals are dissolved in such a big
amount of water (or air) that you couldnt notice
it. Chemicals that dissolve in water can travel
through the tiny spaces between pieces of soil
called pores. The groundwater carries the
chemicals and they concentrate in aquifers. A
very permeable soil will allow water and
pollutants to travel easily through its large
spaces.
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Surface waters, such as a river can carry
pollutants long distances to other water bodies
or in the case of floods, to large areas of land.
Soils can also absorb and hold chemicals. Packed
clay will hold a chemical immobile for the most
part but soft sandier soils will allow more
movement through ground water. There are also
many other chemicals in soil that may react with
deposited pollutants.
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The acronym NIMBY stands for Not In My Back Yard
and is a slogan for most people when talking
about where to put wastes.
Landfill sites have become a popular solution.
Garbage is collected and compacted in a specific
site where it is broken down mechanically and
chemically by bacteria, worms, and insects in a
process called biodegradation.
Leachate, is the liquid from biodegradation.
Leachate is collected and treated in a water
treatment center.
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This table shows how long it takes for some
common materials to biodegrade.
Decomposers are mainly microbes (bacteria).
There are two general types of microbesaerobic
and anaerobic. Aerobic need oxygen anaerobic
thrive without oxygen.
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A secure landfill uses packed clay and a clay cap
to safely store potentially hazardous materials.
Wells and pipes are put in to make sure that
leachate doesnt pollute the groundwater.
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Phytoremediation is the process where plants are
used to break down wastes. Plants slow the flow
of groundwater by taking up the water in their
roots. They also provide a good living condition
for microbes.
The microbes are especially good at breaking down
hydrocarbons (carbon and hydrogen based molecules
that are usually from oil). Phytoremediation can
also help with metals, pesticides, solvents
(dissolving substances), and radioactive
materials.
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Photolysis is the breakdown of materials by
light. Plastic is a chemical that will decompose
with light. After some time in light, plastic
breaks into tiny small particles that are more
easily broken down by bacteria. However, most
plastics are buried in a landfill where light
cannot reach. NO2(g) will also go through the
process of photolysis to eventually make
ozone. NO2(g) light ? NO(g) O(g) O(g) O2(g) ?
O3(g)
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We can all help our environment by remembering
the 4 Rs of waste managementreduce, reuse,
recycle, recover. Reduce means to use fewer
materials so we produce less waste. Reuse means
to use our materials for as long as we can so we
dont need as many new things. Recycle means to
use old things in new ways either through
breaking them down and making things out of
recycled materials or by using pieces in new
ways. Recover means to get back some of the
wasted and thrown away materials we have already
polluted our environment with.
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We will still have some wastes and some of those
wastes will be hazardous. Here are some dos and
donts for handling hazardous waste.
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An oil spill is a good thing to look at when
talking about handling our wastes.
Large sponges called skimmers are set out to
contain the oil. Chemicals are added that break
the oil up into tiny droplets. Bacteria are used
that consume the oil. All of this is an effort
to keep the oil off the shore. Once the oil
reaches shore, wildlife like birds, sea mammals
and fish are polluted and killed.