1
Before the Illinois Pollution Control Board
In the matter of:
Proposed Amendments to
Dissolved Oxygen Standard
35 Ill. Adm. Code 302.206
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)
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R04-25
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Testimony of Thomas J. Murphy, Ph. D.
I am Thomas J. Murphy, an emeritus professor of chemistry at DePaul University. I founded
and chaired the ESP at DePaul. My research was principally related to the atmospheric transport of
toxic substances, the deposition of particulates containing these substances in wet and dry
deposition, and the exchange of vapors of these substances with bodies of water. I served as editor
of the JGLR for six years. I have been involved with water quality issues in Illinois for more than 35
years. As a board member and technical advisor for the lake Michigan Federation for 20 years or so,
I participated in and commented on many water quality issues related to nutrients, dissolved oxygen
and toxics in the rivers and lakes of Illinois and their sediments. I was the scientific advisor to and
member of a citizen’s task force, Operation Lakewatch, in the early 1980’s. This group uncovered
major illegal discharges to Lake Michigan and spurred the WRDGC to revamp its lake-monitoring
programs. My comments here relate to the physical chemistry of the exchange of gases between
phases, and the driving force for their distribution within phases. Chemists claim that chemistry is
the fundamental science because everything is composed of atoms and molecules, and all of the
transformations that occur in the universe, on the earth, in organisms,
etc
. obey the laws of
chemistry.
The Illinois Association of Wastewater Agencies (IAWA) has proposed amendments to the
Dissolved Oxygen (DO) Water Quality Standards for General Use waters in Illinois to the Illinois
Pollution Control Board (Board), R 04-025. Their request is for a
scientifically defensible
standard to
update the current regulations adopted in 1972. Testimony before this Board in subsequent hearings,
supports the need to update the DO standards as requested by the IAWA.
The background papers (Joel Cross 2006; Roy Smoger 2006) submitted by the Illinois DNR and
the Illinois EPA for these standard settings demonstrate that the agencies put in considerable effort
and did a thorough job in evaluating the available data on Illinois streams and the indigenous aquatic
organisms that inhabit them. These data should form a good basis for a science-based review of the
WQ standards for DO in Illinois.
The recommendation of the IDNR and the IEPA for amendments to the DO standards is
described and supported in the document, “Recommended Revisions to the Illinois General Use
Water-Quality Standards for Dissolved Oxygen”, March 31, 2006 (IEPA 2006). In this document (p.
2) they describe the 1986 Ambient Water Quality Criteria Document of the USEPA (USEPA 1986):
“…a foundation from which to interpret…information applicable to the DO needs of aquatic life in
Illinois.”
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This claim is echoed in other testimony presented to the Board in this standard-setting
procedure. Let us review the usefulness of USEPA (1986) to the IEPA in making their
recommendations:
• Most of the studies discussed in USEPA (1986) relate to
cold water
fishes. IEPA (2006)
states: Because USEPA (1986) “warmwater” criteria are based on information for only a few
tested “warmwater” fish species …”
• Most of the reports discussed in USEPA (1986) are based on laboratory studies. IEPA (2006)
states (p. 22): “
Moreover, particularly for non-toxic substances like dissolved oxygen, sole
reliance in laboratory-based acute thresholds is not recommended
;” and they quote Smale
and Rabeni (1995), “
Considerable difference have been found between laboratory tolerance
values and lethal conditions in natural situations
(Moore 1942; Davis 1975).
• Very few studies of stream macroinvertebrates are discussed in USEPA (1986). IEPA (2006)
states (p. 15): “…USEPA (1986) … relied primarily on only two studies of relatively few
types of insects from streams in …”
• The absence in USEPA (1986) of any information from the last 20 years.
• Most of the reports of DO concentrations in USEPA (1986) do not include the temperature of
the measurement. This precludes the determination of the percent saturation of the oxygen in
the sample.
These
deficiencies demonstrate
that USEPA (1986) is an outdated, limited and inadequate
‘foundation’, and preclude it from contributing meaningful help to a scientifically defensible
standard-setting procedure.
A house built on such a foundation can not be expected to stand. Why
do the IDNR, the IEPA and the MWRDGC claim it as a ‘foundation’? The answer may be in a
consideration of the science of gas partitioning.
The partitioning of gases between different phases and their movement within phases are well
understood physical phenomena discussed in all physical chemistry and even most intro chemistry
texts. The partitioning and movement is driven by differences in pressure (activity; percent
saturation). The occurrence of differences in pressure, within or between phases drive and control
such processes as the exchange of oxygen, water vapor, carbon dioxide, nitrogen,
etc
. between the
atmosphere, soils, and bodies of water, and the uptake and distribution of gases to and within all
organisms.
A standard reference book on the principles of respiratory physiology by Pierre Dejours, 1981,
Principles of Comparative Respiratory Physiology
, discusses the science of gas exchange in many
organisms, including fishes and other aquatic organisms. In the chapters relevant to aquatic
organisms, I counted 88 equations that related in one way or another to gas exchange or transport in
the functioning of organisms. In
all
of those equations the concentrations of the gas was given in
units of pressure. In this text on the science of gas transport in organisms, I looked and did not find
one reference to a concentration in mg/L as a driving force for molecular movement.
In contrast, IEPA (2006) uses units of mass mg O
2
/L for the concentrations of oxygen in the
proposed amendments and in the discussion supporting the changes. While there is a proportionality
between pressure units and mass units, the proportionality factor differs depending on the
temperature. The factor depends on the maximum solubility of the gas in water at that temperature,
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and oxygen has a higher solubility in cold water than in warm water. For instance, its solubility in
water is 14.6 mg O
2
/L at 0
˚
C, and 7.5 mg O
2
/L at 30
˚
. Thus water with 7.5 mg O
2
/L present at 30
˚
is
100% saturated–the pressure of oxygen in the water is the same as in the atmosphere, while at 0
˚
the
water is only 51% saturated–the oxygen pressure in the water is only half of an atmosphere.
While
the same mass of oxygen is present (7.5 mg O
2
/L ) at both temperatures, its percent saturation–
what
an organism experiences
, is only one-half as much at the lower temperature as it does at the higher
temperature
. It could be mentioned here that water at 20°C in equilibrium with the atmosphere–the
pressure of the oxygen in each phase is 0.21 atm, contains 9.1 mg O
2
/L while the air contains 284
mg O
2
/L.
The significance of this temperature dependency of oxygen solubility with the proposed DO
amendments is that each of the different time periods has months of the year when the water in
Illinois rivers are zero degrees or close to it–March and February, and months of the year when the
water is often above 25°C–July and August. IEPA (2006) gives no explanation or justification why
they require a daily minimum of 53% saturation at 30
˚
C (4 mg/L) but require only 27% saturation at
0
˚
. It could be noted that the oxygen pressure at the summit of Mt. Everest is 33% of the pressure at
sea level.
Inexplicably and unaccountably, the IEPA is proposing DO standards for General Use waters in
Illinois in mass units (mg O
2
/L). Perhaps there are scientific reasons for not basing the proposed
standards on pressure (or not exclusively on pressure), but their
support documents are totally silent
on an explanation, rationalization or scientific justification for this choice, a choice that does
not
follow the established science of gas transport and partitioning, as demonstrated in Dejours (1981)
and Davis (1975).
The only document cited that supports the use of a mass-based DO standard is USEPA (1986).
IEPA (2006) states (p. 5): “Illinois DNR and Illinois EPA primarily base the recommended revisions
to DO standards on information in USEPA (1986), which provides a sound, scientifically based
foundation.” USEPA (1986) states on its page 1: “Expressing the criteria in terms of the actual
amount of dissolved oxygen available to organisms in mg/L is considered more direct and
easier to
administer
compared to expressing the criteria in terms of percent saturation. DO criteria expressed
as percent saturation, such as discussed by Davis (1975 a,b), are
more complex
and could often
result in unnecessarily stringent criteria in the cold months and potentially unprotective criteria
during times of high ambient temperature or at high elevations.” (emphasis added)
Clearly
USEPA (1986) does not
provide a sound, scientifically based foundation for these
proposed DO standards
(see also comments above). Is ‘ease to administer’ the basis on which we
should base water quality standards in Illinois? Do IDNR scientists find it ‘complex’ to convert
mg/L at a particular temperature to percent saturation? Should we have
standards that
are not
based
on the actual availability of oxygen to aquatic organisms?
In a paper referenced several times in the IDNR and IEPA background documents, Davis (1975)
arrives at recommended DO criteria essential for the protection of fish populations and lists them for
six different groups. The results for the group of ‘freshwater mixed fish populations with no
salmonids’ are shown in the abbreviated table 10 below.
The significance of Table 10 is that the
recommended criteria are in units of percent saturation NOT in mg O
2
/L.
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Davis (1975) recommends a constant PO
2
until 25
˚
, when he recommends a modest increase.
The basis for these recommendations is (p. 2324): “
It must be emphasized that … fish require both
the correct oxygen tension (pressure) gradient to move O
2
into the blood and sufficient oxygen (per
unit volume of water breathed) to fulfill the requirements of metabolism.
”
– – – – – – – – – –
Table 10. Oxygen criteria based on percentage saturation values derived with three levels of
protection in the text. PO
2
’s and values of mg O
2
/L were extracted from Table 9 and rounded off for
use here. The values shown for mg O
2
/L were calculated from the values of mg O
2
/L in this table.
The criteria essential for protection of aquatic fish populations are expressed as percentage
saturation values at various temperatures. They were derived from both PO
2
and mg O
2
/L values, as
both oxygen tension and oxygen content are critical factors. At the lower temperatures, the
percentage saturation value was determined using the PO
2
values essential for maintaining the
necessary oxygen tension gradient between water and blood for proper gas exchange. Higher
percentage saturation values are necessary at the higher temperatures to provide sufficient oxygen
content to meet the requirement of respiration as defined by the
mg O
2
/L values.
Percentage saturation values are defined as “oxygen minima” at each level of protection.
Graphical presentation of the results is found in Fig. 19. The temperatures corresponding to the
percent saturation criteria are defined as “seasonal temperature maxima.”
Freshwater Mixed Fish Populations with no Salmonids
Protection
% Saturation for Criteria
Level
PO
2
mg O
2
/L
0°
5°
10°
15°
20°
25°
A
95
5.5
60
60
60
60
60
66
B
75
4.0
47
47
47
47
47
48
C
55
2.5
35
35
35
35
35
36
– – – – – – – – – –
Based on the petition from the IAWA and the stated objectives of the IDNR and the IEPA that
the new standards be based on science, the proposed amendments to the DO standards now before
the Board are fatally deficient and should not be approved by the Board. They are not based on the
science of gas partitioning and they put organisms with high oxygen requirements at risk in cold
waters.
The IAWA has invested considerable resources in consultants, legal expertise, and staff time to
have the DO standards for the General Use waters in the state amended based on
defensible science
.
Major time and resources have been expended by state agencies to evaluate the considerable amount
of information on the physical and chemical characteristics of the general use water bodies in the
state and their indigenous aquatic organisms. Perhaps the best remedy at this point is to reëvaluate
the DO data now in hand in terms of percent saturation and revise the proposed amendments
accordingly in order to protect the most sensitive types and life stages of aquatic life that require
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relatively higher dissolved oxygen concentrations. These revisions could look like the example
above from Davis (1975) and would keep the current two-tiered set of standards intact.
A more complex and less satisfactory way to base the standards on good science, while keeping
the obtuse method of setting standards based on mass (mg/L), could be to divide each of the tiers
into three or more sections–each covering a limited temperature range, and set separate DO
standards for each temperature range. For example, have ranges of 0-10
˚
, 10-20
˚
and 20-30
˚
. Then
using the percent saturation required for each range, determine the mass of oxygen present at the
midpoint of each (5
˚
, 15
˚
and 25
˚
in this case), and use that as a proxy for a pressure-based standard.
The current water quality standards for DO have been in place in Illinois for 34 years.
Amending them is clearly an involved and complex process. The Board should not allow this one-in-
34-year opportunity to be only ‘tweaking the numbers’. While the scientific base of the proposed
amendments is appreciably better than that of the current standards, the changes are only
evolutionary. The IAWA petition has presented the Board the opportunity to ‘get it right’. Dennis
Streicher, the president of the IAWA has testified in these hearings, “… good science should not be
negotiated.” If the proposed amendments are adopted, they will be obsolete before they go into
effect, being bases on 1972 science. But they may well remain in effect for many years. Thus,
it is
important to get them right
. Neither the current standards nor the proposed amendments are based
on the science of gas partitioning. Therefore there needs to be revolutionary changes in the proposed
amendments if they are to be based on current science.
I urge the Board to delay approving amendments to the DO Water Quality Standards for
General Use waters in Illinois until the amendments are based on current science
. I urge the Board to
require the Agencies to develop amended standards based on the percent saturation of oxygen
, and
on the stream and biology data they have already developed. Such amended standards would satisfy
the request for science-based standards from the IAWA, and should serve to protect the indigenous
aquatic organisms in Illinois waters until climate change necessitates their revision, hopefully well
into the future.
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