Illinois State Water Survey Department of Energy and Natural Resources -- (Reprinted 7-1-87)
Elisabeth Panttaja Siebel is a graduate student in journalism at the U. of Illinois and a part-time Research Assistant at the Water Survey.
Richard G. Semonin is Assistant Chief of the Water Survey and former Head of its Atmospheric Sciences Section. He is also adjunct Professor of Meteorology in the Laboratory for Atmospheric Research at the U. oflllinois and serves on the Executive Committee for the National Atmospheric Deposition Program.
Acid rain is not new. it was first identified in 1872 by an English chemist,
and Swedish meteorologists have been studying it since the 1950s. But
only in the last few years has acid rain become a subject of intensive
research in this country and a source of worldwide concern.
Acid rain is widely believed to have damaging effects on the environment
--- from killing off fish and wildlife, to stunting forest growth and
inhibiting agricultural production, to the erosion of buildings and statues.
There is even some talk about acid rain threatening human health.
In 1980, President Carter's committee on Health and Environmental
Effects of increased Coal Utilization called acid rain one of the major
global environmental problems to face us in this decade, and public and
private sectors have taken the problem to heart:
An automobile company recently issued a pamphlet describing how to
treat paint damage caused by acid rain, and an Illinois farmer discovered
that the warranty on his new roof would not be honored because the
damage, the company said, had been caused by acid rain . . . .
The Illinois State Water Survey is the central data repository and
research ooordinator for Illinois in matters related to water resources
and weather. Its research and service programs encompass assessment
and evaluation of ground, surface, and atmospheric water resources as to
quantity, quality, and use. The Water Survey was founded in 1895 and in
1979 became a division of the lnstitute of Natural Resources (now the
Department of Energy and Natural Resources).
What is Acid Rain?
If you take a glass of distilled water and put it in a room at normal
temperature, the water will react with carbon dioxide molecules in the
air, creating a slightly acid solution. Its pH, formerly 7, is now 5.6.
Many
early discussions 0 acid rain used the 5.6 pH value as the dividing line
between acid and non-acid rain.
This simple definition is no longer accepted and, in fact, no pH value has
been agreed upon for use as the critical dividing line.
What is the pH value of precipitation unaffected by human activities?
Scientists have been trying to answer this question by measuring the pH
values of the "purest" rainfalls they can find, but they have no easy
answers. Some samples from the most remote parts of the world such as
the Indian Ocean and the Amazon jungle have pH values between 4 and 5.31
In a study conducted by the Water Survey near St. Louis, Missouri, rain
receptors were placed every three miles in a 900 square mile area. After
fourteen rainfalls, the measurements taken at each receptor were
averaged, and the resulting values in this one area ranged from 4.3 to 6.8.
These findings suggest that determining what is natural and unnatural
in the chemistry of precipitation is very complex. In addition, the pH
measurement itself can often be a misleading guide to acidity.
A pH value is derived from the relationships between four individual
substances in a solution:
Calcium Sulfuric acid
(There are other chemicals that affect precipitation chemistry, but
these are the major contributors to acid rain.) Calcium and magneslum are
the two alkaline agents, and the degree to which they exist in a solution
directly affects pH levels. Low levels of calcium and magnesium will
result in a low pH reading, just as high concentrations of acid will. Thus,
before an accurate interpretation of a pH reading can be made, the
occurrence of all four substances must be measured and compared.
American Acid Rain Research
Prior to 1972, only two comprehensive rain sampling networks existed
in this country, and those but briefly. The first consisted of 67 ste tions
and operated from July 1955 to July 1956. This survey provided data on a
variety of chemical constituents of rainfall in that year, but it failed to
record pH.
In 1974, two scientists from Cornell University, Cogbill and Likens,
decided to compare pH calculations they made on the chemistry
measurements from the two national networks. They used information
from the 1955-1956 network to calculate the pH values of rainfall for that
year.
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The results showed average values of 4.3-5.0 over most of the
northeast. To the west and south, however, the pH values were higher.
Cog-bill and Likens drew a line ringing that part of the northeast in which
the pH was less than 5.6. They called the pH = 5.6 line the "threshold level"
and used it as a way of identifying the extent of acid rain.
The data from 1966 again showed average pH values of between 4.3
and 5.0 for the northeast, but this time the threshold level of 5.6 was
picked up farther south than before, and extended westward beyond the
area of their study, implying that the acid rain problem had spread over
our midwestern states.
In 1976, Cogbill obtained measurements of pH from many sites in the
northeast for 1972-73. In 1972-73. the average pH values of rainfall
stayed about the same, but the threshold level had moved farther south
into Florida and north into Canada, implicating the entire eastern half of
the United States in an acid rain situation.
A
The trend seemed clear: acid rain was gradually spreading cross the
country.
It was an alarming report. Acid rain had been perceived as a serious
problem in Europe for decades. It had been linked to high levels of gaseous
pollutants in the atmosphere, and Scandinavian research had already
suggested its harmful environmental effects. The study by Cogbill and
Likens was the first time that a trend of increasing acidity had been
identified in this country, and it marked the beginning of the American
acid rain problem.
Scientists measure the relative acidity or alkalinity of a substance on a
so-called pH scale. with values ranging from 0 to 14. Very simply, pH is a
symbol representing the concentration of hydrogen ions in a solution.
Seven is the neutral point, at which a substance is neither acid nor
alkaline. Distilled water has a pH of 7. Numbers greater than 7 refer to
alkaline substances; numbers less than 7 to acids. Thus, ammonia has a
pH of 12, while lemon juice has a pH of 2. The pH scale is logarithmic;
meaning that for every whole number increment. there is a tenfold
difference in the concentration of hydrogen ions.
Leyden note:
a "log scale" means that a pH of 3 is 10x more acidic than pH 4 --- and is 100 times that of pH of 5 (10 x 10). The Richter Scale of Earthquake intensity has the same "log" relationship between its numbers. So -- an EQ of 8 is 10x the power of EQ of 7. That's something to get all shook up about.
Leyden note:
elementary schools in illinois -- including Mark Twain in Charleston, participate in an acid rain "watch" -- where they measure the acidity of the rain and via computer, send their data to a National Geographic collection depot in D.C. Elementary teachers had better know what this "stuff" is all about.
Not only do the pH levels of precipitation vary widely over relatively
short time periods (and even within the same storm events), but they have
also been shown to change significantly over relatively short distances.
Magnesium Nitric acid
A second and smaller sampling network provided data, including
pH, for rainfalls from 1965-66.
But the drastic drop in pH from 1954 to 1960 was suspicious. What had happened in those six years to so radically affect the chemistry of precipitation ?
Richard Semonin, Assistant Chief of the Survey, and his colleagues went
back to the data. This time they broke the compositions of the various
rainfalls down into the four basic parts -sulfates, nitrates, calcium, and
magnesium -and compared them. They observed that the amounts of
sulfuric acid in rainwater had not increased over the years, and that while
the amounts of nitric acid had increased, they had not changed
significantly enough to explain the plunge in pH.
What the Survey
scientists did notice was a substantial drop in the amounts of calcium and
magnesium, the two alkaline substances (whose absence can make water
acidic).
---- Ca + Mg --- Sulfate -- Nitrate --- pH
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Semonin delved into other records for 1954 and discovered that it had been a year of severe drought that affected both the northeastern and midwestern states. Dust storms were a common hazard that year, and one record states that at times the blowing dust reduced the visibility to 1/8 of a mile.
Dust is made up of loose topsoil, rich in calcium and magnesium. It falls as solid particles and also mixes with drops of moisture in the atmosphere and falls as rain. When measured on the pH scale, that rain was unusually alkaline, and the corresponding pH value was unusually high. So Semonin recalculated all the original data from the 1955-56 network. Only this time, where the levels of calcium and magnesium had been unusually high, he substituted more typical values. He discovered that, while the pH values of the northeast remained roughly the same, the pH measurements for the south and mid west were much lower, and the 5.6 threshold level that Cogbill and Likens had observed ringing the northeast did not occur. Semonin's new maps showed average pH levels ranging between 4.3 and 5.0 all across the country. In Illinois, the rainfall pH figure has historically been around 4.4, a value consistent with what has been measured in the state this year. (pH levels since 1978 have been 4.3-4.5 all across the state.)
These findings cast serious doubt on the alleged trend in acidity from 1955-1972. In addition, many scientists argue that data used for acid rain trend analysis should come from the same sites and same type of receptors, and be derived using the same analytical techniques. In the Cogbill and Likens study, both the receptors and the chemistry used to measure the rain were variable. In addition, only ten stations are common to both 1956 and 1966 (for those ten common sites, the acidity increased at four, decreased at two, and remained unchanged at four) and only three stations are common to all three networks.
The media have been instrumental in publicizing the environmental
effects of acid rain. Filmstrips show how acid rain damages crops,
magazine articles talk about the corrosion of buildings, arid newspaper
stories point to "dead" lakes, victims of acid rain. Yet anyone wishing to
dig beneath the surface of these reports will find that the scientific
facts, when they are known, are neither so simple nor so clear.
The two most important potential hazards of acid rain are damage to
aquatic ecosystems and decreases in agricultural production. The
suggested effects of acid rain on lakes and fish are quite alarming and
have received the most attention.
The average pH of a freshwater lake is usually quite high - between 8
and 9.
Lakes in the Adirondack region of New York and in various parts of
southern Ontario and Ouebec, with their unusually low pH readings, have
typically been singled out as examples of the harmful effects of acid rain.
These lakes are virtually carved out of granite and do not have the benefit
of large amounts of soil in their relatively small watersheds to act as
buffering agents.
Do the geological characteristics of the Adirondack and Canadian lakes
make them more vulnerable to outside acidification, or are these factors
in themselves the cause of the low pH readings? The answer to this
question is crucial to the study of acid rain's effects on acuatic
ecosystems. Until we know the chemical history of these lakes, it is
almost impossible to judge whether a low pH reading is natural or man-
made.
At this moment, scientists are conducting chemical studies of the
layers of sediment buried beneath the Adirondack lakes. They hope to
uncover the historical data so necessary to determining whether or not
the lakes have undergone chemical changes and what role, if any, acid rain
has played in the process.
In Illinois, rivers and streams have been chemically tested for a period
of years. Scientists have measured no trend of increased acidity, and no
harmful environmental changes have been noticed. Illinois watersheds are
large and well-buffered, and it is unlikely that high acid levels will ever
pose a serious threat to our aquatic ecosystems.
Illinois watersheds are large and well-buffered, and it is unlikely that
high acid levels will ever pose a serious threat to our aquatic ecosystems.
Scientists usually consider the first danger signal of acidification to be
a decrease in fish populations, and many people have suggested that acid
rain is responsible for the complete disappearance of thousands of fish
from our lakes, especially game fish such as trout which have been shown
to be highly 'acid sensitive.'
Although very few studies have been carried out in natural settings,
laboratory experiments have proven that large quantities of sulfuric acid
released into fish tanks can affect the reproductive organs of fish, and in
higher quantities, the acid can be lethal. Research has also shown that
acid water is especially damaging to fish eggs and hatchlings and that
acid in lakes and streams reacts chemically with surrounding rocks, releasing aluminum and mercury ions that can be harmful - and even deadly - to fish.
After this point, however, scientific consensus breaks down. Many
scientists feel that the laboratory experiments are sufficient to establish
the link between acid rain and decreased fish populations; other experts
think that documented field studies are necessary to support these claims.
The most radical changes in acidity usually occur during winter thaws
or spring, when acids and other substances contained in snow are released
rapidly into streams and lakes as melt-water. In Norway, there is at least
one documented instance of a massive fish kill resulting from a radical
drop in pH in a stream. Even in these dramatic instances, the connection
between increased acidity and decreased fish populations is unclear.
In this country, there have been no reports of fish kills resulting from
drops in pH. There have been reports of decreases in fish populations, but
the cause is a matter of conjecture. The past twenty years has seen such
varied atmospheric and climatological changes, and fish populations can
be influenced by so many factors, that many scientists feel that a direct
cause effect relationship . . . .
Until many more questions can be answered, it will remain difficult, if
not impossible, to either prove or disprove the link between acid rain and
changes in fish populations and aquatic ecosystems.
In Illinois, the most critical aspect of the acid rain issue is its alleged
harmful effects on soil and agricultural production. Here the scientific
evidence comes almost exclusively from laboratory tests. Simulated acid
rain has been shown to cause an impressive array of biological and
chemical changes in plants and soils. Sometimes these changes are
harmful, sometimes beneficial. Some results are even contradictory:
Soybeans treated with acid water, for example, exhibited both decreases
and increases in size and rate of growth.
Among other things, simulated acid rain causes lesions on foliage and
slows the rate of many important microbiological processes in soil. It is
also a good fertilizer and adds significant quantities of nutrients to both
plants and soils.
In nature, actual economic damage to crops or soils due to polluted
precipitation has been reported only rarely, and in most cases the evidence has not been considered scientifically reliable. Most scientists agree that examples of soil deterioration or crop
damage caused by acid rain have not been found. Even if evidence of crop or
soil damage did exist, it is unlikely that Illinois agricultural production
would be affected. The Illinois soil is alkaline and wellbuffered, meaning
that it has plenty of natural chemicals to offset high acidity levels should
they occur.
Whether or not the net effect of acid precipitation will be harmful or
beneficial in any geographic area seems to depend on a variety of interrelated factors, among them the chemical composition of the rainfall,
its duration and intensity, and the general condition of the lakes and soils
on which it falls.
Research suggests that acid rain is most likely to wreak ecological
damage in areas with poorly buffered soils or lakes that are subjected to
long and frequent rainfalls. Other areas are not likely to be affected by
acid precipitation, and some regions may even enjoy ecological advantages
caused by acid rain.
Unlike standard climatic variable which are continuously and exhaustively studied, information about acid rain is scare and incomplete. The lack of data precludes a firm conclusion, but the little that we do know indicates that changes in the acidity of rainfall may be much more subtle than initially conceived.
so far, evidence coming out of Illinois has questioned the alleged trend of increasing acidity and has suggest that at least some instances of radical rain chemistry change may have natural, not man - made, causes.
over the next few years as research findings from groups such as the National Atmospheric Deposition Program and the National Acid Precipitation Assessment Program become available, many of the unresolve issues will probably be decided. At this time, however, the questions are far more numerous than the answers, and as acid rain remains in the public spotlight, it is increasingly important to separate scienctific facts from speculations.
Effects on Lakes
When even "pure" precipitation has a pH of 5.6, one wonders how the
lakes can maintain their low levels of acidity. There are two main
reasons, and both have to do with soil: A lake's "watershed" is the
geographical region surrounding the lake, and any precipitaton that falls in
the watershed area ultimately drains into the lake. When the watershed is
large, the rain travels a long distance before it reaches the lake, and the
soil it passes over and through, usually rich in calcium and magnesium,
acts as a buffering agent to neutralie the rain's acidity. The soil and rocks
that make up the bottom and sides of the lake have the same buffering
effect and help to maintain the lake's low level of acidity.
Leyden note:
Note that term, buffered ? How about "bufferin" - - the OTC drug for headaches; etc. Do you suppose there is a connection ? A buffered solution is one that essentially can maintain a constant pH ( unless severely chemically upset ).
Effects on Fish
Until many more questions can be answered, it wlll remain difficult
to efther prove or disprove the llnk between acid rain and changes in
fish populations and aquatic ecosystems.
These latter scientists point to the fact that the pH levels of lakes vary
naturally, and many species of fish that have lived in lakes for generations have experienced numerous changes in pH without being noticeably
adversely affected. In addition, acid precipitation is not the only cause of
a drop in pH, and not all drops in pH are harmful to fish.
Leyden note:
Remember the 'what is science' discussion about -- cause - correlation and coincidence ? Hmmm - which is at work here ?
. . . . between acid rain and decreased fish populations
is unrealistic. A lack of historical data compounds the problem, making it
difficult to tell the exact extent to which game fish populations have
decreased over time, and what other species, if any, have been affected.
Effects on Soil and Agriculture
Is acid rain a problem or not ?
NOTE:
this report is dates may 1981; revised dec 1984; reprinted july 1987. That was almost a decade ago. You'll need more modern references to supplement this report. Pages 7-8 omitted: topic: The NADP - national atmospheric deposition program / NTN - national trends network