EPA-660/3-73-024
February 1974
                                  Ecological Research Series
Protocol for Evaluating
the Nitrogen  Status
of  Lake Sediments
                                             ul
                               Office of Research and Development

                               U.S. Environmental Protection Agency
                               Washington, D.C. 20460

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             RESEARCH REPORTING SERIES
Research  reports of the  Office  of   Research  and
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   1.  Environmental Health Effects Research
   2.  Environmental Protection Technology
   3.  Ecological Research
   U.  Environmental Monitoring
   5.  Socioeconomic Environmental Studies

This report has  been assigned  to  the  ECOLOGICAL
RESEARCH  series.   This series describes  research
on the effects of pollution on humans,   plant  and
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assessed   for   their   long-   and     short-term
influences.    Investigations  include  formation,
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provides  the  technical basis for setting standards
to  minimize   undesirable   changes    in    living
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                  EPA REVIEW NOTICE
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                                                    EPA-660/3-73-024
                                                    February 1974
              PROTOCOL FOR EVALUATING  THE NITROGEN

                    STATUS QF LAKE  SEDIMENTS
                               By

                        Dennis R.  Keeney
                     University  of Wisconsin
                       Madison,  Wisconsin
                        Grant No.  801362
                     Program Element  1B1031

                         Project Officer

                    Thomas E. Maloney,  Chief
           Eutrophicat ion and Lake Restoration Branch
      Pacific Northwest Environmental  Research Laboratory
                    Corvallis, Oregon  97330
                          Prepared for

               OFFICE OF RESEARCH  AND DEVELOPMENT
              U.S. ENVIRONMENTAL PROTECTION AGENCY
                     WASHINGTON, D.C.  20460
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Prlco 6J cents

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                                 ABSTRACT
This report outlines the approach, methodology and philosophy needed
to undertake evaluation of the nitrogen status of lake sediments,  with
the ultimate aim of estimating their role as a nitrogen source or  sink
to the overlying waters.  It is gleaned from the knowledge and experi-
ence gained from five years of intensive research effort on the forms,
amounts and transformations of nitrogen in lake sediments.  The sedi-
ment environment and sediment nitrogen transformations are reviewed.
Suggested approaches to evaluation of the nitrogen status of sediments,
along with the required methods,  are presented.

The methods are based on those developed or tested in the author's
laboratory.  The suggested approaches involve monitoring or comparative
characterization, or both, of the forms of nitrogen in lake sediments,
along with laboratory tests to assess the relative rates of various key
nitrogen processes such as nitrification, denitrification, mineraliza-
tion and immobilization.  Suggested additional research needs are
included.

This report was submitted in fulfillment of Project Number 16010 EHR,
Grant Number R-801362,  by the Department of Soil  Science, University of
Wisconsin, under the partial  sponsorship of the Environmental Protection
Agency.  Work was completed as of September 1973*

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                                 CONTENTS


                                                                   Page

Abstract	   ii

Acknowledgments  	   iv

Conclusions  	    I

Recommendations  .	    2

Introduction 	    3

The Sediment Environment 	    4

The Sediment-Water Transfer Mechanisms 	    6

Forms and Availability of Sediment Nitrogen  	    8

Nitrogen Transformation Pathways in Sediment 	   10

Suggested Methods to Evaluate the Nitrogen Status of Lake
  Sediments	.	13

References	2)

Appendix:  List of Project Publications  	   2k

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                              ACKNOWLEDGMENTS
The assistance of the Water Resources Center, The University of Wiscon-
sin, and of Dr. G. A. Rohlich, Dr. J. Villemonte and Dr. G. Chesters,
who served (in that order) as Director of the Center during the period
covered by this grant, is gratefully acknowledged.  Special thanks are
given to Dr. P. D. Uttormark, Project Associate, and to Ms. Mary
Fitzgerald, Administrative Assistant, in the Water Resources Center.

The support and cooperation of the College of Agricultural  and Life
Sciences, The University of Wisconsin, Madison,  is also gratefully
acknowledged.

The personnel who worked under the authors direction, and whose efforts
were in large part responsible for its achievements, were:   Dr. J. G.
Konrad, Dr. D. A. Graetz and Dr.  A. N. Macgregor (Project Associates),
R. L. Chen, and B. H. Byrnes (Research Assistants) and K. L. Chen and
R. T. Checkai (Specialists).
                                   iv

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                                CONCLUSIONS
Lake sediments contain a large reservoir of nitrogen,  most  of  which  is
in refractory forms and thus not immediately available.   The readily
available nitrogen of sediments is the ammonium and organic nitrogen
present in the interstitial  water, and the ammonium nitrogen on  the
exchange complex.  This nitrogen can be released to the  overlying water
by diffusion and by sediment mixing.

Nitrogen reaches lake sediments by sedimentation,  nitrogen  fixation,
and immobilization of nitrate.  The sediment may be regarded as  a nitro-
gen sink because much of this nitrogen is not remineralized to an avail-
able form, and because about 60 to 70% of the nitrate-N  in  sediments  is
reduced to nitrogen gas.  However, sediments also must be regarded as a
nitrogen source because sediments contain as much or more available,  or
potentially available, nitrogen as that added yearly by  external  sources.

The chemical composition of  the Wisconsin lake sediments investigated
affected nitrogen transformations and availability. The influence of
calcium carbonate appeared to be dominant; calcareous  sediments  had
much higher nitrogen transformation rates than noncalcareous sediments,
even though they contained less available nitrogen.

The results of the research  effort of this project suggest  that  it  is
possible to obtain a set of  indices which would indicate the nitrogen
status of a lake's sediment.

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                              RECOMMENDATIONS
The indices suggested in this report must be evaluated in a lake
sediment survey program.  This should be done by agencies with the
capability to monitor a wide range and large number of lakes.   Such a
survey could be coordinated with any existing lake inventory program.
Additional funding would be required.  However,  gaining the capability
to predict more accurately the nitrogen status of a lake system should
be worth the effort.

The approach should be to obtain the indices suggested over time on a
sufficient number of lakes differing in properties and trophic level
that statistically significant trends could be ascertained.  Then
quantitative limits could be placed on the indices which proved to have
predictive capability,  while those of no benefit could be rejected.

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                               INTRODUCTION
Several recent reviews have pointed out the possible importance of  lake
sediments as a source or sink of nitrogen to overlying waters'"".
However field quantitation of the role of sediments  to the nitrogen
balance of lakes is extremely difficult,  if not  impossible,  due to  the
complexity of the required experimental systems  and  edge effects due  to
restricted container size.  The purpose of this  paper is to consider
the sediment and lake properties which influence the role of sediments
as a source or sink of nitrogen to lakes  and outline appropriate
analyses which could be undertaken to evaluate the nitrogen status  of
sediments.

The specific objective of the research project was first to evaluate
the forms and amounts of nitrogen compounds in lake  sediments,  and
their relationship to lake trophic status and second, the transforma-
tions of nitrogen in sediments.  The ultimate objective was to  enable
prediction of the role of sediments as a  nitrogen source or sink to the
overlying waters.

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                         THE SEDIMENT ENVIRONMENT
 The physical properties of  lake sediments vary widely, depending on
 their  composition.  At one  end of the scale are sandy deposits of
 relatively high bulk density  (ca. 1.5 g/cc) which contain low levels
 of total and available nitrogen, to  low bulk density, (ca. 1.0 to 1.1
 g/cc)  dispersed deposits containing  largely silt and clay-size
 particulates.  A given lake may contain significant amounts of both
 extremes, with an  infinite  gradation of sediments with intermediate
 properties.  In many lakes, the finer sized sediments are located in
 the middle, deeper portions of the lake, due to size sorting during
 deposition  .  The composition of the particulate matter of sediments
 is also highly variable, and may consist of sand, silt,  clay (crystal-
 line and amorphous), organic matter and marl (in calcareous sediments)
 in varying proportions.

 The fluidity (i.e., the relative ease of penetration of a sediment by
 a sampling device or sounding weight)''  is a parameter of lake sedi-
 ments  that may well be worth estimating as it affects the degree of
 mixing in sediments.  In some lakes, the sediment-water interface is
 quite  diffuse, extending over a range of one to several  meters, with
 gradually increasing bulk density with depth of the sediment below the
 sediment-water interface.  Other lakes have a sharp sediment-water
 interface, while the majority have a diffuse sediment-water interface
 zone of a few centimeters".  Also,  fluidity of the sediment at the
 sediment-water interface likely will  vary widely within the lake, and
 with time, as sediments are more dispersed under anaerobic than aerobic
 condi tions.

 The water content, and related bulk density, of sediments will  depend
 on its fluidity, and also to some extent on the sampling method.  Normal
 water contents of sediments when taken by the Eckman dredge range from
 50 to 95% on a volume/volume basis.   This water, commonly referred to
 as interstitial water,  contains in general  much higher NH^-N and organic
 N concentrations than the overlying water.   Within the limits of high
 speed centrifuges,  it is all of the same composition, i.e.,  the NH^-N
 content of the water removed by centrifugation at relatively low
 g-forces is the same as that removed at  g-forces to ¥t,000 X g12.

 The pH of sediments j_n situ probably does not vary widely and in
 general is in the slightly acid to neutral  range (pH 6-7.5),  presumably
 due to the dominant influence of various redox systems'*.   The lower
 values are typical  of those obtained with softwater Wisconsin sediments
while the higher values are representative  of hardwater  (calcareous)
 lake sediments.  On drying, pH of unbuffered (noncalcareous)  sediments
 can decrease,  presumably due to the production of h^SOi*  on oxidation
 of sulfides.

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The Eh (redox potentials) values of sediments are typically  0 to
negative.  Graetz et al.'^ obtained data indicating that -250 to -300
mV was the stable Eh value for the sediments they investigated below
the sediment-water interface, while i n s itu values of +100 to -100 mV
at the sediment-water interface have been measured in Lake Wingra,
Wisconsin's.

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                     SEDIMENT-WATER TRANSFER MECHANISMS
Physical, chemical and biological processes are intimately involved in
determining the net uptake or release of nitrogen at the sediment-water
interface.  These factors are often interrelated, and the overall
process of sediment-water interchange is quite complex"'''.   Because of
experimental difficulties, meaningful  quantitative field experimental
data on nitrogen sediment-water transfer rates are difficult to obtain2.
Probably the only valid field approach will be observation of the
effects of markedly reducing outside nitrogen inputs, or other manipu-
lative schemes such as drawdown, on the nitrogen balance in the lake''.
However, use of '5N treated sediment in bottles suspended in sediment
have shown promise'2''5.

A working model for nitrogen uptake or release by sediments must include
the processes that add nitrogen to sediments, control the nitrogen
content of the interstitial  water, and the release of nitrogen from the
interstitial to the overlying waters".   A model  (Fig. 1) which is
currently guiding our thinking involves an active sediment of 5 to 20 cm
thickness overlying a historical sediment.  The active sediment is
being constantly reworked by physical  (currents, wave action, fish) and
biological (gas formation and ebullition, faunal activity) processes.
The historical  sediment, on the other  hand, is not involved in nutrient
exchange with the exception of interaction with  seepage water.  Recent
evidence"*'2 indicates that the 5 to  20 cm depth of mixing in sediments
is reasonable for relatively unconsolidated materials.

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9-
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(O
 o.
 2.
 ~00
                                              benthic organisms)
Active
sediment
            Historic
            sediment
                              5  to
                             20 cm
  Soluble
combined N
  poo!
                       Diffusion
                                                                  Uotakt
                                                        Exchange
                                                               Mineralization, desorption
                                                   Immobilization,  sorption
                                 Seepage water
Exchangeable
ammonium N
                                                Sorbed
                                                organic N

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                 FORMS AND AVAILABILITY OF SEDIMENT NITROGEN
A  survey of  the  forms and amounts of nitrogen  in surficial and profile
samples of sediments from Wisconsin 1akes'°»'7 has shown that while
sediments contain  the same  forms of nitrogen as do soils, there is a
marked difference  in the absolute amounts and  in many cases, the dis-
tribution of nitrogen.  As with soils, the nitrogen in lake sediments
is present largely as organic-N, and the distribution of the various
forms of organic-N determined  (total acid hydrolyzable-N, amino acid-N,
ami no sugar N, hydrolyzable ammonium-N and unidentified-N) was similar
to results obtained for organic soils'^.  This work also showed that
lake sediments contain significant amounts of NH^-N entrapped within
the lattices of  clay minerals, and that sediments from southern Wiscon-
sin lakes contained much greater concentrations of clay-fixed NH^-N
than did northern Wisconsin lake sediments.  This was probably related
to extent of erosion and soil type in the watersheds of the respective
lakes, i.e., the southern Wisconsin lake sediments contain more crys-
talline clay minerals, eroded from the watershed, than do the northern
lake sediments.  Fixed NH^-N is essentially unavailable for microbial
uptake'8.

"Available" N in sediments may be divided into two classes, namely:
(a) the soluble  and exchangeable NH/+-N and soluble organic-N, which is
immediately available for transfer to the overlying water; and, (b)
that nitrogen potentially available through microbial  mineralization
of organic-N.

Recent work'9 has shown that soluble-  and exchangeable-NH^-N are equally
available to nitrifying bacteria,  while Byrnes et al.12 and Isirimah
and Keeney'5 have obtained evidence that sediment NH^-N is transferred
to the overlying water.

An estimate of the potential of sediment organic N to be mineralized
is much more difficult to obtain.   Austin*" incubated sediments in
carboys at wide water:sediment ratios  under aerobic conditions and
obtained considerable release.   This experiment,  however,  was so dif-
ferent from actual  conditions that valid conclusions cannot be obtained
from her work.   A more reliable test is to incubate sediments under a
narrow waterrsediment ratio, anaerobic conditions and  cold temperatures
(10° C or less)  and determine the  increase in NH^-N (soluble and
exchangeable) in the sample.  Using this approach,  Chen et al.'9 found
that,  with a Lake Mendota sediment, practically no increase in NH^-N
occurred in l*t days under quiescent (non-stirred)  conditions but that
about  2.1  mg NH^-N/liter sediment/day  was formed when  the mixture was
stirred.   Similar results were obtained for a noncalcareous Trout Lake
sediment2'.   Further work in our laboratory'^ has  indicated that

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sediment's have a high potential  for producing NH^-N and releasing this
N into the overlying water.  This work involved use of simulated lakes
in plexiglass columns, incubated under quiescent, anaerobic conditions
at room temperature for 48 to 52 days.  During this time period, the
sediments studied released from 0.38 mg NHi^-N/liter sediment/day
(noncalcareous Tomahawk) to 0.65 mg (calcareous Hendota).  More recently
Isirimah and Keeney'5 estimated a mineralization-release rate of *fO (ig
NH^-N/liter sediment/day in Lake Wingra during the summer.  These
values were obtained in bottles suspended in the sediment, and thus are
a conservative estimate.  This was further evaluated by field monitoring
of the NH^-N in Lake Wingra sediments22 where a loss rate of 29 mg
NH/^-N/m2 sediment surface/day was estimated.  The actual release rate
for calcareous eutrophic Wisconsin lakes thus apparently ranges from
about k to 29 mg NH^-N/nr/day.  These estimates show that lake sediments
are a significant source of nitrogen to the overlying water, with from
40 to 290 g/hectare/day being released.

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                NITROGEN  TRANSFORMATION  PATHWAYS  IN SEDIMENTS
 The pathways  involved  in  the  cycling,  gains and  losses of nitrogen in
 sediment-water  systems have been  recently  reviewed?***  (Fig. 2).   In
 summary,  the  nitrogen  cycle  in  sediment-water  systems  is largely micro-
 bial,  and more  complex than  in  most  terrestrial  systems.  Several of
 the pathways  are  dominated by the oxidation-reduction  (redox) status of
 the system, although evidence has been obtained  in our laboratory of
 indirect  effects  due to pH, available  carbonate-carbon and perhaps
 available calcium or phosphorus2'.

 As  stated preciously,  the sediment is  almost always  in a highly reduced
 state.  The only  possible exception  is in  stirred shallow water sedi-
 ments  and at  the  sediment-water interface  in oxygenated waters.  To-date,
 we  have not observed Eh values of >+100 mV in  the sediment-water inter-
 face region,  although  locating  the interface precisely is difficult if
 not impossible  in most  cases.   This  indicates  that anoxic conditions
 prevail in the  consolidated sediment,  and  that.denitrification, N£
 fixation,  and Fe  and Mn reduction would be expected  to occur.  Below the
 interface, the  Eh  is negative, probably in the range of -200 to -300 mV
 for most  sediments.  Thus nitrogen transformations are carried out by
 facultative and obligate anaerobic bacteria.

 Laboratory and  field incubation studies using ammonium-'5N have shown
 that the  ammonium-N in sediments  is continually being assimilated while
 organic-N  is  being ammonified'2»15.  The net effect of the mineraliza-
 tion-immobilization reaction appears to be for ammonificat ion to occur
 during the summer, and  immobilization  in the winter, in apparent
 response  to sediment temperature".

 Most sediments have the capacity  to denitrify considerable nitrite-N
 and nitrate-N2'"2".  This may be  of particular importance for lakes
 receiving nitrate-N in water entering  the lake through the sediments by
 a hydraulically connected aquifer.  Studies on a number of Wisconsin
 lakes  indicate that over 60% of the nitrate-N added to sediments is
 denitrified,   the  remainder being  immobiIized2^»2^»2°.  Further,
 nitrate-N will be formed in oxygenated waters,  and by diffusion or
mixing, be carried into the sediment.  No doubt most of this nitrate-N
also will  be  lost from the system by denitrification.  Some sediments,
when stirred and oxygenated,  are  capable of rapid nitrification.  It
 is plausible  that nitrate-N could be formed in surficial  sediments
during high winds, with denitrification occurring during quiescent
conditions'5,190  This principle also could be used to remove nitrogen
 from lakes, using hypolimnion aeration combined with stratification to
effect a nitrification-denitrification sequence.
                                   10

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(O
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     ATMOSPHERE
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(D
rt

A
                                          ExternaL Sources
    WATER
                N03 ,   NH4- ,   Organic  N
                      Participate organic N


                           (Ammonification)
NH
>NO,
                                                              (Nitrification)
IT


I.  SEDIMENT
NO
                                                                    Exchangeable)
               NO,   in  Groundwater

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Our denitrif ication research also has shown that considerable of the
added nitrate-^N is transformed to ammonium-N and organic-N.  I  had
originally assumed this was entirely due to a mechanism involving
preferential utilization of nitrate-N over ammonium-N by the sediment
microbial population.  However, even more recent work^°»^7 indicates
that Nz fixation by anaerobes may be at least partially responsible for
the internal cycling of nitrogen in sediments.  The overall  reaction
sequence envisaged here is:

                                         overlying water
                                                t
                   NOj-N -» N02-N -> (NO)
                       N02-N -> NhVN^ Organi c-N
The net result of this sequence is that part of the nitrate-N that
reaches sediments will be converted to available or potentially avail-
able nitrogen.

The potential for the addition of nitrogen to the lake ecosystem
through N  fixation in sediments was also evaluated in our
laboratory "» 7.  The acetylene reduction method has been modified for
sediment studies and applied to sediment samples from several Wisconsin
lakes.  Results obtained indicate that in the eutrophic,  calcareous
sediment lakes of southern Wisconsin, this pathway can add a  significant
amount of nitrogen to the
                                   12

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             SUGGESTED METHODS TO EVALUATE  THE  NITROGEN  STATUS

                             OF LAKE SEDIMENTS
The approach taken to this section is to provide recommendations  for
(a) the minimum of sampling and analysis of sediments  required  to
obtain an estimate of their nitrogen status and (b)  further  process
studies which would provide additional  information,  mainly for  use  in
more detailed investigations.   The methods given are those used cur-
rently in our laboratory.  Many have been used extensively for  research
in soil N transformations, and have been modified as needed  for use on
sediments.  Operating details  of the methodology can be found  in  the
references quoted.

SAMPLING

Obtaining a representative sample of lake sediment from most lakes may
be one of the most critical steps in obtaining an estimate of  sediment
contribution to the nitrogen status of lakes,  and the  problem  obviously
is greater as the area of a lake increases. However,  for survey  pur-
poses, detailed grid sampling  of a lake is one approach. Alternatively,
samples from the deepest portion of the lake as well as from intermed-
iate and shallow water column  depth could be obtained.  Areas  such as
obviously isolated bays should be sampled independently. Profile water
samples also should be taken at the time of sediment sampling.

Numerous sediment samplers are available, any  of which might be prefer-
able depending on sediment consistency and information desired.  For
relatively fluid (unconsolidated) sediments, the Eckman dredge works
satisfactorily for grab samples, and simple, gravity driven  stratifi-
cation samplers (e.g., Soil Test Inc.,  Evanston, Illinois Catalog No.
DR-1006) for cores of 20 to 30 cm depth.  For  consolidated  sediments
(e.g., sandy materials) a Peterson dredge, or  more sophisticated
corers^8»29 are necessary.

Core samples to at least the 20-cm depth are to be preferred even for
routine survey work.  However, dredge samples  will suffice  if  a coring
device and/or the man-power is not available.   For laboratory  work, a
dredge sample usually is necessary due to the  relatively large amount
of sample required.  If a dredge is to be used, the Eckman-type of
dredge is preferred over a Peterson-type as the former obtains a  more
representative sample of the surficial  sediments.  At  the time of
sampling, free water should be decanted from the sediment sample.

The sediment (and water) samples must be handled in such a way as to
minimize changes during transportation and storage.   In particular,  the
sediment samples should be protected from exposure to  the air,  stored
                                   13

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at low temperatures (just above freezing) to minimize microbial  activity
and analyzed as soon as possible.  We have found that plastic bottles
permit diffusion of sufficient air that significant changes can occur,
especially in smaller-sized samples.  Large (10 tc 20 liter) polyethy-
lene containers are satisfactory for bulk samples.  Sample bottles
should be completely filled with sediment so that air is excluded.
Water samples should be treated with phenyl mercuric acetate* and
stored at 5° C.  The sampling frequency is optional.  We have noted
significant periodic fluctuations of NH^-N (soluble and exchangeable)
in Lake Wingra sediments^ with a maximum in the autumn and minimum in
the spring.  Ideally,  sampling should be conducted weekly at overturn
and every other week the rest of the time.  At a minimum, sampling
should be conducted at spring turnover, summer stratification (or about
mid-August if the lake does not stratify), fall turnover, and mid-
winter.  If only one sampling time is possible, a relatively static
period (i.e., mid-summer or mid-winter) would be the most feasible if
only a comparison between lakes is desired.

On-Site Measurements

The following should be measured at the time of sampling:  (a) water
temperature profile (YSI or equivalent probe) to sediment-water inter-
face; (b) dissolved oxygen profile to sediment water interface (YSI
probe); (c) pH profile to sediment-water interface (may be taken later
on water samples collected); (d) (optional) Eh profile to sediment-
water interface (a platinum-black indicator electrode on a long lead,
and calomel reference  electrode dipped into the water surface provides
a suitable electrode pair, (any portable Eh-pH meter with ± 700 mV
range is satisfactory), and, (e) general limnological observations as
desired (e.g., Seechi  disk reading).

PHYSICAL CHARACTERISTICS OF THE SEDIMENT

Before subsampling, the sample should be mixed thoroughly.  Subsampling
can best be conducted  by using a piston type coring device (about 1 cm
diameter) or a hypodermic syringe with an opening enlarged sufficiently
that it does not become clogged.
 Dissolve 0.1  g of phenyl  mercuric acetate in 20 ml  of dioxane.   Dilute
 with water to 100 ml.   Add I  ml  of this solution to each  liter  of
 water sample.

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Sediment Water and Solids

Add a 100 ml sample to a tared 100-ml  graduated beaker.   Determine
weight of wet sediment (WNJ).   Evaporate the sediment to dryness on a
hot plate at 60° C, and bring to constant weight (16-24 hrs)  in an oven
set at 105-110° C.  Determine weight of oven-dry sediment (wds).

     a)  Sediment water content, ml/liter - ^s " wds^  ^l0^  where dw =
         water at temperature of solutions.        dw
     b)  Bulk density (D^) * -^ — in g/cc.

     c)  % Solids - 100 - % H20.

Extraction of Interstitial Water

Place  150 ml of sediment in a 200-ml polypropylene centrifuge bottle,
centrifuge at 16,00 Xg (10,000 rpm for a 30 cm radius fixed head rotor
Sorvall Superspeed RC-2 Automatic Refrigerated Centrifuge.)  Decant the
water and determine the water volume removed.  Weigh the moist residue,
allow the residue to air dry and determine the oven-dry weight of solids
on a subsample.  Calculate the amount of water retained by the sediment.

If the centrifuge used is different from the above, the relative centri-
fugal force can be calculated by:
     g • (1.118x10-5) (RPM)2 (radius of rotation in cm, R)

or:
     RPM «= f    16.000 Xg     "1
           L (1.118x10-5) (R) -I

CHEMICAL CHARACTERIZATION OP SEDIMENTS

Presence of
Treat 10 ml of sediment with 5 ml of 1 ti HC1 and stir gently.  If gas
bubbles observed to evolve, the sediment is calcareous.

Carbon  (optional)

Estimate organic C by determining the CO* evolved on combustion of the
sediment sample at 650° C, and total C (if CaCO^ is present) by CO 2
evolved on combustion at 900° C.  Inorganic C = total C -organic
C30.

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Report results to 3 significant figures as % of oven-dry sediment.
Alternatively, inorganic C can be reported as CaCO?:

     % CaC03 « (8.3) (% inorganic C)

Organic Matter Content

Estimate as the weight loss on ignition at 550° C for two hours of  a
one g sample of air-dry sediment.  Correct results for water content of
the air-dry sample, and report as % of oven-dry sediment.

Sulfur (optional)

Estimate total S by using the digestion methods for soil as described
by Bardsley and Lancaster^'.  Estimate sulfide-S by distillation with
external heat under N£^'  of a sample treated with HC1, and inorganic
forms of S (except sulfate) by distillation as above with the exception
that mossy Zn is also added32.  |n the inorganic S procedures, sulfide
is estimated as molybdenum blue.

Nitrogen Forms

Total Sediment Organic Ni'trogen-

Either the semimicro or macro Kjeldahl procedure is satisfactory33,3**.
Total nitrogen can be determined  on moist sediment or on the air-dry
solids material.  The values obtained should be corrected for inorganic
forms present.  Results can be expressed on the mg N per liter or % of
oven-dry weight of solids basis.

Inorganic N-

Separate the interstitial water as described previously.  Determine
interstitial ammonium-N by steam distillation of a 10- to 50-ml aliquot
of the water sample with  0.2 g of ignited Mg035.  Subsequently, deter-
mine (nitrite plus nitrate)-N by  steam distillation of the same aliquot
with 0.2 g of finely divided Oevarda Alloy35.  Determine nitrite-N  by
the Gries-l llosvay method^.  Extract the ammomum-N remaining on the
sediment exchange sites (exchangeable ammonium-N) bv treatment of the
residue after centrifugal ion with 100 ml of 2 £ KC1'°.  Determine
ammonium-N in the extract by steam distillation with MgO.  Express  the
results as mg of each form of nitrogen per liter of sediment.  The
exchangeable ammonium-N value must be corrected for the amount of
interstitial ammonium-N remaining in the residue after centrifugal ion
and for the increased volume due  to water in this residue.
                                   16

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Soluble and Participate Interstitial  Water  Nitrogen  (optional)—

Determine total  nitrogen (except  nitrite-N  and  nitrate-N)  on  a 10-  to
50-ml aliquot of interstitial  Mater  by  the  Kjeldahl  procedure.   Filter
another aliquot  through a 0.^5 u  Millipore  membrane  filter, and  deter-
mine organic N as above.  Soluble organic-N = total-N  of  filtered
sample minus interstitial water ammonium-N. Particulate-N equals  total
N of unfiltered sample minus soluble organic-N.

Forms of nitrogen in Lake Water-

Oetermine ammonium-N, nitrite-N and  soluble organic  N  as  described
above.  Nitrate-N is often below  the detection  limits  of  the  distilla-
tion method and a more sensitive  colorimetric method such as  the one
described by EPA31* should be used.

PROCESS STUDIES

A few simple process studies are  listed which,  when  performed as part
of a lake survey, will give a relative indication of the  biological
activity and N release characteristics of the  sediment-water  system.
For more detailed investigations, the reader should  consult  the  papers
listed or the author for recommendations.

Ae rob i c N i t r i fIca 11 on

This test, while far from representative of in situ  conditions,  is sug-
gested because it does seem to give a very simple index of potential
biological activity  in sediments'?.   Add 500 ml of sediment  and  500 ml
of water to a 2-liter widemonth jar.  Add  10 g of reagent grade  pow-
dered CaCO^ and a 1  ml suspension of a soil or sediment sample shown
previously to be capable of nitrifying ammonium.  Cover the  bottle with
a loosely-fitting cap of aluminum foil, and place in a dark,  constant
temperature cabinet at 10° C.  Stir continuously using a magnetic
stirrer and Teflon coated stirring bar.  Remove 100-ml samples at  1, 3,
5, 7, \k and 21-day  intervals.  Determine  exchangeable and interstitial
water ammonium-N and  interstitial water nitrite-N and nitrate-N

The  nitrate accumulation curve will  have a delay phase of one to five
days, and one or more linear phases.  The  first phase will correspond
to the time when ammonium-N (exchangeable and  soluble) is still  present
in the medium.  During this time, ammonium-N is not  limiting nitrifi-
nitrification.  A second phase will  occur when the reaction:   organic N
-» ammonium-N  is rate-1imi ting.  This rate will  give an indication  of
the  availability of  sediment organic N.

Data should  be presented as:   (a) the delay phase (hours):   (b)  nitrifi-
cation rate  in the first linear phase  (ug  nitrogen/liter/hour).
                                    17

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Ammoniurn-N Formation Rate

Ammonium-N formation (net mineralization) under anaerobic conditions
may prove to be a valuable index of nitrogen availability.  This is
more representative of |n situ conditions than the aerobic nitrification
test described previously, but is somewhat more difficult to perform
because anaerobic conditions must be maintained.  However, this can be
done by sweeping the sample with helium before closing the flask,  and
using a tightly sealed system.

Place 100 ml of sediment in a 250-ml Erlenmeyer flask, fitted with a
ground glass stopper that can be attached to the body of the flask by
springs.  Purge the atmosphere above the flask with helium,  and stopper
tightly.  Set up sufficient samples so that duplicates can be analyzed
at 0, 3, 7, 14, 28, 56 and 112 days.  Incubate in the dark in a constant
temperature cabinet at 10° C.

Express results as p,g NH^-N formed/liter sediment/day for each of  the
incubation periods (ug NH^-N formed = incubated sediment value minus
initial sediment value).

Nitrate Disappearance Rate
           O 1
Chen et al.   noted significant differences in the rate of nitrate
disappearance when nitrate was added to southern Wisconsin calcareous
and northern Wisconsin noncalcareous sediments.  Because nitrate-N can
be lost from anaerobic systems via two pathways, namely denitrification
nitrate-N - nitrogen gas and assimilatory nitrate reduction nitrate-N -
ammonium-N and organic N), tracer studies with nitrogen-15 are needed
to distinguish the relative rates of these pathways.  However, the rate
of nitrate disappearance should be an indication of the intensity  and
capacity of the redox buffering of the sediment, and will also inte-
grate the rate of biological  activity and organic matter availability.

To a 100 ml polyethylene centrifuge tube, add 50 ml of sediment and
5 ml of a 100 ug/ml nitrate-N (as KNO^) solution.  Purge the atmosphere
with helium, stopper tightly, mix thoroughly, and place in a dark
constant-temperature cabinet set at 10° C.  Remove samples at approxi-
mately 30 minutes, 2 hours, 4 hours, 8 hours, 2k hours and 48 hours
after incubation.  (Shorter or longer incubation times may prove more
feasible with particular samples.)  Determine ammonium-N, nitrite-N and
nitrate-N.

Express results as y,g nitrate-N lost per liter of sediment per hour, and
ug nitrite-N formed per liter of sediment per hour.  (A plot of the
results may prove helpful  in interpretation.)
                                   18

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NH^-N Exchange

This test will provide an indication of the amount  of  ammonium-N  in
solution and on the sediment exchange sites at  varying levels of  NH^-N.
Sediments that do not sorb as much ammonium-N on  the exchange sites have
the potential for releasing more ammonium-N to  the  overlying waters.

To a series of 25 ml samples of sediment in a  100 ml centrifuge tubes,
add 25 ml of a solution containing 0, 10,  100,  or 500  ug of ammonium-N
per ml (as NH^Cl).  Purge the atmosphere with helium,  stopper tightly
and shake gently for four hr.  Determine exchangeable  and  interstitial
water ammonium-N.

Express results as % of added NH^-N on the exchange sites  and  in  the
interstitial water, using zero ammonium-N  addition  as  the  control.

Effect of Sediment;Water Ratio on Ammonium-N Release

Dilution of sediments in the water, as might occur  when a  shallow sedi-
ment is stirred by wave action, currents,  or mechanical action  from
fish, boats, gas bubbling, tends to favor  release of ammonium  from the
exchange sites.  This is because the equilibrium of the reaction:

     X-NH^ + i Ca++ si X-i Ca + NH^+; X - exchange material

proceeds to the right as the concentration of cations  in solution is
decreased, which  is the process which occurs on dilution.   Comparison
of the magnitude of the dilution effect between different  sediments
should indicate which sediments have the potential  for contributing  the
most ammonium-N when disturbed.

To 20 ml of sediment in a 250 ml centrifuge tube, add  10,  20,  50, 100
or 200 ml water  (preferably water from the lake sampled or alternatively,
an artificial solution containing the salt concentration and hardness
typical of the lakes being studied).  Shake for four hours,  and deter-
mine the ammonium  in the interstitial and exchangeable fractions.

Express results as  ug of ammonium-N per liter of sediment  in each
fraction with each  treatment.

EVALUATION OF DATA  OBTAINED
For the most part, the information and suggested parameters have been
based on our experience.  The methods are those we would utilize • r~
given the charge of evaluating the nitrogen status of lakes on a
modest budget.  However, to date, insufficient observations on these
parameters are available to adequately evaluate their usefulness or
                                    19

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establish numerical values to classify lakes with regard to the poten-
tial N contribution from sediments.  The first task should be to corre-
late the suggested parameters with other information available, partic-
ularly trophic status of the lake using a large number of lakes of
diverse types.  From these data, one could then omit tests which did not
give meaningful results.

The next phase would be to apply the tests which show promise over two-
to three-years' duration on selected lakes.  From these data, one should
be able to devise a range of values for each test which would define
closely the nitrogen status of the sediment.
                                   20

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                               REFERENCES

 1.   Vollenweider, R. A.  Scientific Fundamentals of the Eutrophication
     of  Lakes and Flowing Waters with Particular Reference to Nitrogen
     and Phosphorus as Factors  in Eutrophication.  Organization Econ-
     omic Cooperation and Development, Paris.  DAS/CS1768.27, 1968.

 2.   Gahler, A. R.  Sediment-Water Nutrient  Interchange.  J_n Proc.
     Eutrophication-Biostimulation Workshop, Berkeley, Calif, pp. 2^3-
     257,  1969.

 3.   Lee,  G. F.  Eutrophication.  Eutrophication Information Program,
     Univ. Wisconsin, Madison.  Occasional Paper No. 2. 39 p> 1970.

 k.   McKee,  G. D., L. P. Parrish, C. R. Hirth, K. H. Mackenthum and
     L.  E. Keup.  Sediment-Water Nutrient Relationships.  Part 1.  Water
     Sewage  Works, June, 1970.

 5.   McKee,  G. D., L. P. Parrish, C. R. Hirth, K. M. Mackenthum,  and
     L.  E. Keup.  1970.  Sediment-Water Nutrient Relationships.   Part
     2.   Water Sewage Works,  July,  1970.

 6.   Brezonik, P. L.  Nitrogen:Sources and Transformations  in Natural
     Waters,  jjn Nutrients  in Natural Waters.  Allen, H. E.  and J. R.
     Kramer  (ed.).  New  York, Wiley, 1972.   p.  1-50.

 7.   Keeney, 0. R., J. G. Konrad, and G.  Chesters.  Nitrogen Distribu-
     tion in Some Wisconsin Lake Sediments.  J. Water  Poll.  Contr.  Fed.
     **2:411-417,  1970.

 8.   Keeney, D. R.  The  Fate of Nitrogen  in  Aquatic Ecosystems.   Eutro-
     phication  Information  Program,  Univ. Wisconsin, Madison.   Litera-
     ture Review  No.  3,  1972 59 p.

 9.   Macgregor, A. N. and D.  R. Keeney.   Nutrient  Reactions.  In;  Man
     Made Lakes and Human Health.   Stanley,  N.  F.  and  M.  P.  Alpers  (ed).
     London, Academic Press,  197**  (in press).

10.   Frink,  C.  R.   Chemical and Mineralogical  Characterization  of
     Eutrophic  Lake  Sediments.  Soil Sci. Soc.  Amer. Proc.  33:369-372,
     1969.

11.   Lee, G. F.   Factors Affecting  the  Transfer of Material  Between
     Water and  Sediments.   Eutrophication Information  Program,  Univ.
     Wisconsin, Madison. Occasional  Paper  1.   50  p.,  1970.
                                   21

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 12.  Byrnes, B. H., D. R. Keeney, and D. A. Graetz.  Release of
     Ammoniurn-N from Sediments to Waters.  Proc. 15th Conf. Great Lakes
     Res., Internet. Assn. Great Lakes Res., p. 2*6-259., 1972.

 13>  Ponnamperuma, F. N., E. Martinez, and T. Loy.  Influence of Redox
     Potential and Partial Pressure of Carbon Dioxide on pH Values and
     the Suspension Effect of Flooded Soils.  Soil Sci. 101:421-431,
     1966.

 14.  Graetz, 0. A., D. R. Keeney, and R. Aspiras.  Eh Status of Lake
     Sediment-Water Systems in Relation to Nitrogen Transformations.
     Limnol. Oceanogr. (in press), 1973*

 15.  Isirimah, N. 0. and 0. R. Keeney.  Nitrogen Cycling in Lake Wingra.
     I. Process.  Limnol. Oceanogr. (in press), 1974.

 16.  Kemp, A. L., and A.  Mudrochova.   Distribution and Forms of Nitrogen
     in a Lake Ontario Sediment Core.  Limnol.  Oceanogr. 17:855-867,
     1972.

 17-  Konrad, J. G., D. R. Keeney, G.  Chesters,  and K. L. Chen.  Nitrogen
     and Carbon Distribution in Sediment Cores  of Selected Wisconsin
     Lakes.  J. Water Poll. Contr. Fed. 42:2094-2101, 1970.

 18.  Bremner, J. M. and D. R.  Keeney.  Determination and Isotope-Ratio
     Analysis of Different Forms of Nitrogen in Soils.  3- Exchangeable
     Ammonium, Nitrate and Nitrite by Extraction-Distillation Methods.
     Soil Sci. Soc. Amer. Proc. 30:577-582, 1966.

 19.  Chen, R. L., D. R. Keeney, and J. G. Konrad.  Nitrification in
     Lake Sediments.  J.  Environ. Qua I. 1:151-154, 1972.

20.  Austin, E. R.  Release of Nitrogenous Compounds from Lake Sedi-
     ments.  M.S. Thesis, Univ. Wisconsin Library, Madison, 1970.

21.  Chen, R. L., D. R. Keeney, D. A. Graetz, and A. J. Holding.
     Denitrification and Nitrate Reduction in Lake Sediments.  J.
     Environ. Qual. 2:15-29, 1972.

22.  Isirimah, N. 0., D.  R. Keeney, and E. H. Dettman.  Nitrogen
     Cycling in Lake Wingra.  II. Field Results.  Limnol. Oceanogr.
     (in press), 1974.

23*  Chen, R. L. and D. R. Keeney.  Nitrogen Transformations in Sedi-
     ments as Affected by Chemical Amendments.   Water Resources
     Bulletin (in press), 1973*
                                   22

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2k.  Keeney, 0. R.,  R.  L.  Chen,  and 0.  A.  Graetz.   Importance of
     Denitrification and Nitrate Reduction in Sediments  to  the  Nitrogen
     Budget of Lakes.  Nature 233:66-6?,  1971.

25.  Chen, R. L., D. R. Keeney,  J.  G.  Konrad, A.  J.  Holding, and  D. A.
     Graetz.  Gas Production in Sediments  of Lake Mendota,  Wisconsin.
     J. Environ. Qual.  1:155-158, 1972.

26.  Macgregor, A. N. and 0. R.  Keeney.  Denitrification in Lake
     Sediments.  Environ.  Letters 5:175-181, 1973-

27.  Macgregor, A. N.,  0.  R. Keeney, and K.  L.  Chen.  Nitrogen  Fixation:
     Sediment Contribution to Nitrogen Budgets of Lake Mendota  and Lake
     Wingra.  Environ.  Lett. 4:21-26,  1973«

28.  Wentz, D. A. and G. F. Lee.  Sedimentary Phosphorus in Lake  Cores--
     Observations on Depositional Patterns in Lake Mendota.  Environ.
     Sci. Technol. 3:75^-759, 1969.

29*  Daniel, T. C. and G. Chesters.  Design and Construction of a
     Shallow Water Sediment Core Sampler.  Environ. Lett. 1:225-228,
     1971.

30.  Konrad, J. G., G.  Chesters, and D. R. Keeney.  Determination of
     Organic- and Carbonate-Carbon  in Fresh Water Lake Sediments by a
     Microcombustion Procedure.  J. Thermal  Anal. 2:199-208, 1970.

31.  Bardsley, C. E. and J. D. Lancaster.  Sulfur.  In;   Methods of
     Soil Analysis, Black, C. A. (ed).  Madison, Wis., American Society
     of Agronomy, 1965, p.  1102-1116.

32.  Aspiras, R.  B., D. R. Keeney, and G. Chesters.  Determination of
     Reduced Sulfur Forms as Sulfide by Zinc-Hydrochloride Acid Distil-
     lation.  Anal. Lett. 5:425-^32, 1972.

33.  Bremner, J.  M.  Total Nitrogen.   In;  Methods of Soil Analysis,
     Black, C. A. (ed).  Madison, Wis., American  Society of Agronomy,
     1965,  p.  11^9-1178.

34.  Environmental  Protection Agency.  Methods for  Chemical Analysis
     of Water and Wastes.   Cincinnati, Ohio, Environmental Protection
     Agency,  1971.

35.  Bremner, J.  M. and D.  R. Keeney.  Steam Distillation Methods for
     Determination  of Ammonium,  Nitrate and  Nitrite.  Anal. Chim. Acta.
     32:485-^95,  1962.
                                   23

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                 APPENDIX:  LIST OF PROJECT PUBLICATIONS
 1.  Keeney, D. R., J. G. Konrad, and G. Chesters.  Nitrogen Distri-
     bution in Some Wisconsin Lake Sediments.  J. Water Poll.  Contr.
     Fed. 42:411-417, 1970.

 2.  Keeney, D. R., B. H. Byrnes, and J. J. Genson.   Determination of
     Nitrate in Waters with the Nitrate Selective Electrode.  Analyst
     95:383-386, 1970.

 3.  Konrad, J. G., G. Chesters, and D. R.  Keeney.  Determination of
     Organic- and Carbonate- Carbon in Freshwater Lake Sediments  by a
     Microcombustion Procedure.  J.  Thermal Anal. 2:199-208, 1970.

 4.  Konrad, J. G., D. R. Keeney, G. Chesters,  and K. L.  Chen.  Nitro-
     gen and Carbon Distribution in  Sediment Cores of Selected Wiscon-
     sin Lakes.  J. Water Poll. Contr. Fed. 42:2094-2101,  1970.

 5.  Keeney, D. R., R. L. Chen, and  D. A.  Graetz.  Importance  of
     Denitrif ication and Nitrate Reduction in Sediments to the Nitrogen
     Budget of Lakes.  Nature 233:66-67, 1971.

 6.  Keeney, D. R., R. A. Herbert, and A.  J. Holding.  Microbiological
     Aspects of the Pollution of Freshwater with Inorganic Nutrients.
     jjn The Society for Applied Bacteriology, Symposium Series,  Sykes,
     G. and F.  A. Skinner, (eds). No. 1.  London Academic  Press, 197',
     p. 181-200.

 7.  Chen,  R.  L., D. R. Keeney, and  J. G.  Konrad. Nitrification in
     Lake Sediments.  J. Environ. Qua!. 1:151-154, 1972.

 8.  Chen,  R.  L., D. R. Keeney, J. G. Konrad, A. J.  Holding, and D. A.
     Graetz.  Gas Production in Sediments  of Lake Mendota, Wisconsin.
     J. Environ. Qual. 1:155-158, 1972.

 9.  Chen,  R.  L., D. R. Keeney, D. A. Graetz and A.  J.  Holding.
     Denitrif ication and Nitrate Reduction in Lake Sediments.  J.
     Environ.  Qual. 1:158-162,  1972.

10.  Keeney, D. R.   The Fate of Nitrogen in Aquatic  Ecosystems.   Eutro-
     ph ication  Information Program,  Water  Resources  Center,  University
     of Wisconsin.   Literature Review No.  3, 1972, 59 P*

11.  Aspiras,  R. B., D. R. Keeney and G. Chesters.  Determination of
     Reduced Inorganic Sulfur Forms  as Sulfide by Zinc-Hydrochloric
     Acid Distillation.  Anal.  Lett. 5:425-432, 1972.
                                    24

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12.   Byrnes,  B.  H.,  D.  R.  Keeney and  0.  A.  Graetz.   Release  of
     Ammonium-N  from Sediments  to Waters.   Proc.  15th  Conf.  Great  Lakes
     Res.,  Internat. Assn. Great Lakes  Res.,  p.  249-259,  1972.

13.   Keeney,  D.R.   The Nitrogen Cycle in Sediment-Water  Systems.   J.
     Environ. O.ual.  2:15-29,  1973.

14.   Macgregor,  A.  N.,  D.  R.  Keeney and K.  L.  Chen.   Nitrogen Fixation:
     Sediment Contribution to Nitrogen  Budgets of Lake Mendota  and Lake
     Wingra.   Environ.  Lett.  4:21-26, 1973.

15*   Macgregor,  A.  N. and  0.  R. Keeney.   Oenitrification in  Lake Sedi-
     ments.   Environ. Letters 5:175-181, 1973.

16.   Macgregor,  A.  N. and  0.  R. Keeney.   Methane Formation by Lake
     Sediments During In Vitro Incubation.   Water Resources  Bulletin
     (in press), 1973.

17.   Macgregor,  A.  N. and  0.  R. Keeney.   Nitrogen Fixation by Sediments
     of Selected Wisconsin Lakes.  J. Environ. Q,ual • 2 (in press), 1973<

18.   Chen,  R. L. and D. R. Keeney.  Nitrogen Transformations in Sedi-
     ments  as Affected by  Chemical Amendments.  Water Resources
     Bulletin (in press),  1973.

19.   Graetz,  D.  A.,  D.  R.  Keeney and  R. Aspiras.  Eh Status  of
     Lake Sediment-Water Systems in Relation to Nitrogen Transforma-
     tions.   Limnol. Oceanogr.  (in press),  1973.

20.   Macgregor,  A.  N. and  0.  R. Keeney.  Nutrient Reactions.  _l_n Man
     Made Lakes  and Human  Health.  Stanley, N. F. and M. P.  Alpers,
     (eds).   London Academic Press, 1974 (in press).
                                   25

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 SELECTED WATER
 RESOURCES ABSTRACTS

 INPUT TRANSACTION FORM
                                                1. Report No.
                                                                     3. Accession No.
                                                w
 4. Title

    PROTOCOL FOR  EVALUATING THE NITROGEN  STATUS OF LAKE
    SEDIMENTS
                                                 S. Report toe

                                                 6.

                                                 8.
 7.  Author(s)
           Keeney,  Dennis R.
    Department of  Soil  Science
    University of  Wisconsin, Madison
                                                                     10. Project No.
                                                                        16010 EHR
Environmental  Protection Agency
 12. s,v •.••!•£ Organization

 IS. Supplementary Notes
          Environmental Protection Agency report number,
                         11. Contract/Grant No.
                            R-801362
                               . v' Report <";.
                         Final;
          EBA-660/3-73-024, February 1974.
 16. Abstract
      The approach  and methodology  to evaluate the nitrogen status of lake  sediments,
 with the ultimate  aim of estimating  their role as a nitrogen source or sink  to the
 overlying waters,  is outlined.  The  information is derived from five years of
 research effort  by the author and  associates on the forms,  amounts and transformations
 of nitrogen  In  lake sediments.  The  suggested approach  involves monitoring or  compar-
 ative characterization, or both, of  the forms of nitrogen in lake sediments, along
 with laboratory  tests to assess the  relative rates of various key nitrogen processes
 such as nitrification, denltrifIcatlon, mineralization  and immobilization.
 17a.  Descriptors
      *Lakes, *lake sediments, *water chemistry, *sediment  chemistry, *eutrophlcation,
 *nitrogen, nitrogen balance, nitrogen sources, nitrogen sinks, nitrification,
 denltriflcation,  mineralization,  immobilization, nitrogen  fixation.,


 17b.  Identifiers
 Lake rehabilitation, lake survey, Wisconsin.
 17c. COWRR Field &. Group
 18. Availability
      19.  Security Class.
         (Report)

      'iO.  Security Cici .1.
21. No. of
   Pages

22. Price
Send To:

WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OP THE INTERIOR
WASHINGTON. D.C. 10340
 Abstiactoi
                                        Institution
                                                University of Wisconsin
WHSIC 1O2  (R6V. JUNE 1971)
                                                                                    G P O 488-j

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