Environmental Science: The Effects of Acid
Rain on the Shells of Birds.
(Process skills used in this experiment were: observation
and prediction.)
August 9th: Today, after brainstorming different environmental concerns of
our planet, our class began an experiment to demonstrate the effects of
acid rain on the eggs of birds. We placed a raw chicken egg in a jar of
vinegar (4% acetic acid). Each student wrote a prediction on what they
thought would happen to the shell of the egg. The first observation that
students made was that the jar was filled with bubbles. These appeared to
be on the egg shell. 24-hours later, we observed the egg again. Many
students who had predicted that they would see pieces of shell floating on
top were surprised when the only thing they saw was a white frothy scum
floating on top of the vinegar. The egg sat in the vinegar over the weekend.
What students observed when they came in on Monday was that the shell
was completely dissolved by the vinegar and that the egg was enlarged.
Reaction:
The acetic acid in the vinegar reacts with the calcium carbonate (CaCO3)
in the egg shell and releases carbon dioxide (CO2) that can be seen as
bubbles on the shell. The egg insides remain intact and are held together
by two fragile membranes just inside the shell.
The egg is bigger than when it was first put into the vinegar because the
vinegar and some of the water has moved through the membranes to the
inside of the egg. These membranes are semi-permeable and allow water
to move through them. This process is called osmosis.
We will follow up this experiment by placing the already enlarged egg into a
jar of plain water. Since the inside of the egg is already around 90% water,
we will demonstrate that, by placing it into a container of 100% water, the
water should start to move through the membrane to equalize the amount
of water both inside and outside the membrane. Students will add food
coloring to help them see this process of osmosis more clearly.
(http://www.imaginationstationtoledo.org/content/2011/04/how-to-make-a-naked-egg/)
Resources:
Sources of Acid Rain

Acid rain has increased since the dawn of the Industrial Revolution.
Humans generally produce acid rain through emissions from factories that
release combinations of sulfur, nitrogen and carbon into the air and mix with
naturally occurring water molecules. Volcanic eruptions also cause acid rain to
form.
Food Chain

Declines in snail populations herald drops in nesting success for
some bird species.
Acid rain depletes calcium in soil. Snails that typically feed on that calcium as
they excrete their shells die off in areas of acidic soils. Birds that rely on the
snails as food can survive by eating other prey, but are unable to produce sturdy
eggs.
Read more: (Acid Rain & Bird Eggs | eHow.com http://www.ehow.com/facts_5898702_acid-rain-birdeggs.html#ixzz23MbNQBTS)
Effects of Acidity on Plants and Animals
As a first example of the effects of acid rain, we can examine a case which is not
obvious - effects on non-aquatic, tree nesting birds. This study was carried out in the
Netherlands. It was observed that the proportion of birds laying defective eggs rose
from roughly 10% in 1983-84 to 40% by 1987-88. The defective eggs had thin and
highly porous egg shells, which resulted in eggs failing to hatch because of shell
breakage and desiccation. As a result, there was also a high proportion of empty nests
and clutch desertion. It was also observed that these effects were limited to areas of
acid rain.
Since the birds did not appear to be directly affected by the acidity, the food chain
was examined (these birds are positioned at the upper part of the local food chain).
The difference between areas of normal soil pH (buffered by high calcium content
due to limestone and marble outcrops and bedrock) and those with acidic soil
appeared to be the presence of snails. The snails depend on the soil as their calcium
source as they secrete their shells. With much of the CaCO3 leached out of the soil by
the acid precipitation, the snails could not survive in the area. The birds did not, at
first, appear to be affected, because they continued to eat spiders and insects which,
while supplying a sufficiently nutritious diet for the birds, where a poor source of
calcium.
To test the hypothesis that the lack of calcium was the cause of the bird's laying
defective eggs, ecologists "salted" the area with chicken egg shell fragments. The
birds began to eat the chicken egg shells, and those that did laid normal eggs.
In this case, acid precipitation had effects that passed on up the food chain.
(http://faculty.plattsburgh.edu/thomas.wolosz/acid_rain.htm)