(neutral
to slightly all‘
rated into hydrogen and hydroxyl ions.
Natural waters are buered—that is, there is a natural mechanism which
regulates the pH so that it usually varies Within the narrow range between 7
:
and 9. The concept of buers also applies to the regulation of pH in the internal environment of living things. The pH of human blood, for example, is
maintained at 7.4:
The carbon dioxide and the bicarbonate
ions dissolved in water are mainly
:
responsible for the regulation of pH in lakesand streams. If a strong acid is ‘
added to disülled‘ water, which is without these dissolved compounds and is
hot buered; its pH will change drætically; if the same amount of acid is
î
to naturally buered lake water, however, the change in pH will be
relatively small.
'
Rain picks up carbon dioxide in the atmosphere. The water and the car—
bon dioxide react to form carbonic acid, and carbonic acid becomes dis—
sociated into hydrogen— and bicarbonate ions. This increase in hydrogen ion
î
concentration gives—rain a pHî of 5.7
normal conditions. If that were the
;
end of the matter, we would expect lake and stream water to be similarly
slightly acidic. But after water reaches the ground…it percolates through the
_ !
soil, acquiring more carbon dioxidèwhich has been produced by the respira—
toryacti‘vity ofîplantroots and microorganisms. When water containing car—
, ?
bon dioxide (and carboniè acid'by the association} comes into contact with
rocks such as tnestone, calcium bicarbonate is leached out and set free in the
water. -
'
As mentioned previously, the bicarbonate ion is the most abundant ion
,
fOUnd‘in natural£fresh Wate‘rs. These-bicarbonate ions react with the hydrogen.
i0ns- to form carbonic acid (the reverse of the reaction in which carbonic acid
is dissociated into hydrogen ions and‘bicarbonate ions). Thus, the conversion.
]ÏQ‘fQf‘
of
to
acid (a relatiVely weak acid) uses up the ex—
‘ —
thereby bueng the effect of the latter on the
pH. A strong acid will add— many hydrogen ions to the water, and how much
;
acid can be added to any— stream or other body of water before the pH is
.
‘changed.therefgœ appreciably depends on the amount of bicarbonate ions
available in the water to take up the added hydrogen ions.
have recently been recorded in the acidity of rain demon—
“
Stateleth hoW ‘ChŒges'm'PH fcan occur and how industrial pollutants can
on aglobahscale. In a numberof places in or near highly
“
thepH of rainwaterhas droppedÿ Measurements taken in New
_
England (Hubbard Brook Experimental Forest) and New York (Finger Lakes »
'
‘
in theScandinavian countries, sh0w pH values as low as
3'0‘ Thls
is —dùe presumably to :srfuric.and nitric acids in
‘
and the s0urce of these acids is ae-sulf-ur and nitrogen oxides
fess'fuel‘sl —In Sweden, changes
:
the
t'o acid rain. One.pos—
isan increase in the amount
Of"
54
An Uncommon Friendw
to slightly all‘
rated into hydrogen and hydroxyl ions.
Natural waters are buered—that is, there is a natural mechanism which
regulates the pH so that it usually varies Within the narrow range between 7
:
and 9. The concept of buers also applies to the regulation of pH in the internal environment of living things. The pH of human blood, for example, is
maintained at 7.4:
The carbon dioxide and the bicarbonate
ions dissolved in water are mainly
:
responsible for the regulation of pH in lakesand streams. If a strong acid is ‘
added to disülled‘ water, which is without these dissolved compounds and is
hot buered; its pH will change drætically; if the same amount of acid is
î
to naturally buered lake water, however, the change in pH will be
relatively small.
'
Rain picks up carbon dioxide in the atmosphere. The water and the car—
bon dioxide react to form carbonic acid, and carbonic acid becomes dis—
sociated into hydrogen— and bicarbonate ions. This increase in hydrogen ion
î
concentration gives—rain a pHî of 5.7
normal conditions. If that were the
;
end of the matter, we would expect lake and stream water to be similarly
slightly acidic. But after water reaches the ground…it percolates through the
_ !
soil, acquiring more carbon dioxidèwhich has been produced by the respira—
toryacti‘vity ofîplantroots and microorganisms. When water containing car—
, ?
bon dioxide (and carboniè acid'by the association} comes into contact with
rocks such as tnestone, calcium bicarbonate is leached out and set free in the
water. -
'
As mentioned previously, the bicarbonate ion is the most abundant ion
,
fOUnd‘in natural£fresh Wate‘rs. These-bicarbonate ions react with the hydrogen.
i0ns- to form carbonic acid (the reverse of the reaction in which carbonic acid
is dissociated into hydrogen ions and‘bicarbonate ions). Thus, the conversion.
]ÏQ‘fQf‘
of
to
acid (a relatiVely weak acid) uses up the ex—
‘ —
thereby bueng the effect of the latter on the
pH. A strong acid will add— many hydrogen ions to the water, and how much
;
acid can be added to any— stream or other body of water before the pH is
.
‘changed.therefgœ appreciably depends on the amount of bicarbonate ions
available in the water to take up the added hydrogen ions.
have recently been recorded in the acidity of rain demon—
“
Stateleth hoW ‘ChŒges'm'PH fcan occur and how industrial pollutants can
on aglobahscale. In a numberof places in or near highly
“
thepH of rainwaterhas droppedÿ Measurements taken in New
_
England (Hubbard Brook Experimental Forest) and New York (Finger Lakes »
'
‘
in theScandinavian countries, sh0w pH values as low as
3'0‘ Thls
is —dùe presumably to :srfuric.and nitric acids in
‘
and the s0urce of these acids is ae-sulf-ur and nitrogen oxides
fess'fuel‘sl —In Sweden, changes
:
the
t'o acid rain. One.pos—
isan increase in the amount
Of"
54
An Uncommon Friendw