Acid Precipitation

Posted by on Jan 14, 2013 in The Biology of Nature | No Comments

Acid precipitation can be rain, sleet, snow, or any other type of precipitation caused by acids of primary sulfur and nitrogen. Any compound–either organic or inorganic–that can liberate hydrogen-ions upon dissociation (where ions are split into smaller particles).

There are thousands of lakes, ponds and high mountain streams in the Adirondacks and Catskill Mountain Ranges in New York State, New England and Canada that are slowly dying due to acid precipitation. The problem is the inability for these habitats to buffer the acidity that is present in acid precipitation. Some of the habitats have a buffer and can deal with the acid but others do not.

The basis of the problem is pH, or degree of acidity. pH, as defined in our study guide, is “the negative logarithm of the hydrogen-ion concentration”. To put it simply, it is the measure of the hydrogen-ion concentration. The hydrogen-ion is the ion responsible for acidity. It is responsible for acidity in the environment and also for stomach acidity. If hydrogen-ion concentrations get high, the pH gets lower. Adversely, the less hydrogen-ion concentration there is, the pH increases.


A neutral pH is 7. Anything below 7 becomes more acid. Any pH above 7 becomes more alkaloid. An acid is a compound that has the capability, upon dissociation, of liberating the hyrodgen-ions. There are two acids associated with natural–and unnatural–associations:


Carbonic Acid (H2CO3). Results in combination of carbon dioxide and water, producing carbonic acid. This acid is commonly found in lakes, stream and ponds. It is also found in the blood and fluids of the human body. Carbonic acid is a weak acid because it remains in its carbonic form. As H2CO3, it ties up the hydrogen-ions.


It only breaks down into hydrogen and carbonate in very small amounts. Since it liberates relatively few hydrogen-ions, it is considered a weak acid. Natural systems have evolved to cope with this weak acid. No buffering is required because not very much hydrogen is liberated. Most mountain streams commonly have pHs between 6 and 7 (slightly acid) because they have carbonic acid in them. Organisms have evolved to exist at those pH levels.


Those acids that associate very strongly in water. Classic examples of strong acids are

Sulferic Acid (H2SO4) and Sulfurous Acid (H2SO3). Only about 30% of acid precipitation are the acids of nitrogen. The rest of them are sulfur acids.



Sulfuric acid is considered a strong acid because in water it dissociates very strongly into its two ionic components: Hydrogen and sulfate ion. Whereas carbonic liberates very few hydrogen-ions—and therefore decreases pH only slightly below neutral—sulfuric dissociates very strongly, releasing a lot of hydrogen-ions that can significantly lower the pH. The point is, that when this acid precipitation–when these large amounts of sulfuric acid—fall on mountain streams, lake and pond areas with very little buffering capacity, they cannot cope with this heavy influx of acidity. PH is dropped drastically and the affects on aquatic organisms is disastrous.

This leads us to a very pivotal question: In terms of buffers, what kind help an environment deal with this acidity? When talking about buffering ions, we are talking about bicarbonate ion (ACO3) and carbonate ion (CO3).


These ions are naturally found in areas where the sub-straight has a high sedimentary rock content, specifically limestone (which is very high in carbonates and bicarbonates). These buffering ions have the ability to take the acid precipitation, remove those reactive hydrogen ions, tie them up and making them non-reactive as carbonic acid and removing them as a source of acidity. Lakes and ponds, for example, that are in limestone areas do not have pH problems.


They are not acid—for example, the Finger Lakes are slightly alkaloid.


Streams, ponds and lakes in non-sedimentary areas (for example, many of the lakes and ponds in the Adirondacks) are not in high-buffer strata. They don’t have the ions—the carbonates and bicarbonates—to buffer these acids. They are the ones that are suffering so much from acid rain.

It is very important because the major component of acid precipitation are these acids of sulfur.

Levels of pH and levels of aluminum that are critical for aquatic organisms:

As far as pH, around 4.4 to 5.2 seem to be critical. pHs around 5 or slightly lower causes a severe amount of damage to the egg stage of trout and also to the young that hatch out called “sack fry”.

As far as aluminum, concentrations of about 0.3mg per liter appear to be very detrimental to fish survival. Any concentration above 0.3mg causes an increased secretion of mucus on the gills’ surfaces. What the fish tissues are trying to do is to protect the gills against these toxic metals that are breaking apart protein compounds within the gills’ structure. This mucus has an effect of causing strangulation: It coats the gills and blocks the transfer of oxygen and carbon dioxide across the gills’ surface and the fish will strangle, or suffocate.


pH’s of about 5.3 and aluminum concentrations of about 0.5 appear critical to invertebrates—at least with may-flies, one of the most dominant forms of invertebrates in trout habitats.


The same thing happens with aluminum concentrations. The gills of the may-flies become clogged with mucus and they will suffocate. This causes detrimental problems with these lakes, because the organisms within the lake die. What results is that invasive species will soon take over that are immune, or tolerant, to the acids—species such as suckers, bullheads and yellow perch.


pHs in the Adirondack lakes were running—at the time of the filming of this lesson—between 4 and 4.5, well below critical levels. There are very acid situations.

The lowest pH ever recorded in rainfall was in Wheeling, WV, with a pH of 1.8.

Brandy Brook, the site of this video, is so-called because of its brandy-colored waters. It represents streams that are often seen in higher elevation areas. They are common in parts of the Catskills and the Adirondacks.

BRANDY BROOK:,-75.661554&spn=0.016005,0.027595&oe=utf-8&client=firefox-a&hq=brandy+brook&t=m&z=15

Professor W. and his limnology students did invertebrates studies on the stream to get an idea of the stream’s pollution status. The three main organisms in these mountain streams are may-flies, catus-flies and stone-flies. In their studies, they found that there were no may-flies in the brook. This was their first indication to them that something was wrong with Brandy Brook. The next step was to look at the fisheries. There were no fish in the stream, although it flows year-round. Water samples were taken and sent to Cornell University for testing of pH, toxic metals and alkalinity.


Alkalinity is a measure of a solution to find out if it has the ability to neutralize acids with buffering ions. The test results showed that the pH level was at about 5 and the aluminum concentrations (inorganic aluminum) were about 0.5. The pH was very low and the aluminum was high.

The next thing to determine was whether the may-flies were driven out by competition or because of the pH/aluminum factor. In order to determine this, you must run in situ bioassay,or on-sight tool for measurement.

They took may-flies from downstream, stuck them into cases, and then put them in small cases, then placed them into Brandy Brook. At the same time, they had their controls—that is, may-flies in cages in the creek. If caging was a cause of death, they would know from these controls. In 48 hours, when they checked the cages, all of the controls in the round-out (which has a pH of about 7), all of the controls were alive.

When they checked the may-flies in Brandy Brook cages, all of the may-flies were dead.

Their gills were clogged with mucus and had suffocated from congestion.

With another group of independence studies a year ago, Professor W. and his team of students came back to Brandy Brook to check out the stone-flies.


They found that there were three dominant species of stone-flies in the round-out downstream. But, only two of those three were present in Brandy Brook. The one absent was the most dominant stone-fly in the round-out. They used the same type of in situ assay. This time it took 96 hours, but in that amount of time the same situation happened to the stone-flies as what happened with the may-flies from the previous bioassay: They suffered from suffocation by mucus build-up. Not only was an entire group of invertebrates were missing form Brandy Brook but also a species of stone-flies that would normally be present were missing.

Brandy Brook has heavy acidity associated with organic decomposition. It serves as a perfect microcosm to study toxic metal poisoning and acidity without relying on acid precipitation lakes as a source with which to work. Tannic acids and humic acids contribute to its acidity; Brandy Brook starts in a large cedar bog upstream, ffrom where all the acidity comes.

On terrestrial systems, acid precipitation can cause major devastation. For example, the maple industry in New England is in serious trouble because acid precipitation is affecting maple trees—there is a marked decline in sugar maples.

MAPLE SYRUP,1208484300,1/stock-photo–collecting-sap-to-make-maple-syrup-in-the-springtime-11644057.jpg

As far as wildlife, one of the leading theories on the decline of the black duck is that the food supply that they feed on is being affected by acid precipitation: The vegetation in the invertebrates that form the bulk of their food supply are declining, causing the black duck population to shrink as well.


Can we stop acid rain, or the devastating affects of acid rain? There are answers, but they are expensive. And the problem is that governments and industries do not want to pay for the methods to clean up the environment from the devastation.

One of the solutions can be to install stack precipitations on smock stacks, which would entrap and reduce the amount of sulfur dioxide–which escapes into the atmosphere to combine with rain and form sulfuric acids—and therefore reduce sulfur emissions.


There are also ionic exchange resins, where as the sulfur dioxide is leaving the stacks it can combine with calcium to form calcium sulphate and water, forming a substance called gypsum which is valuable in sheet rock. The sulfur dioxide would not be released into the air.

One of the most promising approaches would be to introduce species that are resistant to acid precipitation. Cornell researches got the idea from studies of yellow perch in Big Moose Lake.


They found that the yellow perch built up a resistance to the acidity. That is, the perch transferred from more neutral lakes into Big Moose couldn’t survive the acidity or the toxic metal concentrations. But, those perch that have been present in the lake for a number of years have adapted genetically to those low acidities. The researches are attempting to breed acid-resistant brook trout.

Ultimately what will solve the problem is major funding to stop the emissions. But this invokes the question:

How can you put a price tag on life?

—————————————-DISCUSSION QUESTION—————————————————————–

A) I am not far from Central Park, and in the park is the famous Lake. The Central Park Lake is a 18-acre water body that contain very diverse organisms. Largemouth bass, black crappie, yellow perch, bluegull and carp are just some of the fish found in the Lake.


It is a typical lentic body of water. There is fall and spring overturn. Winter causes stratisfication. During the summer, we will see increase of zooplankton. Photosynthesis is high during the summer.



B) Factors affecting stream life:

1. Natural Flows (Water Flows)

2. Light

3. Temperature

4. Pollution



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