RELEASE OF SEDIMENT P
IN MILL CREEK OF PORTAGE AND WOOD COUNTIES,
WISCONSIN
By
Amy A. Timm
A Thesis
Submitted in partial fulfillment of the requirements of the degree
MASTER OF SCIENCE
IN
NATURAL RESOURCES (WATER)
College of Natural Resources
UNIVERSITY OF WISCONSIN
Stevens Point, WI
January 2012
Approved by the graduate committee of:
_______________________________
Dr. Paul McGinley, Committee Chairman
Professor of Water
_______________________________
Dr. Les Werner
Professor of Forestry
_______________________________
Dr. David Ozsvath
Professor of Geosciences
_______________________________
Dr. Katherine Clancy
Professor of Water
ii
ACKNOWLEDGMENTS
Many people and groups were instrumental in the completion of this project. Whether
the assistance was in funding, sharing of ideas, revisions or support, I am very grateful.
I would like to thank my advisor, Dr. Paul McGinley.
His ideas, enthusiasm and
suggestions made this project a joy to work on. I appreciate all the time spent on
revisions and his knowledge of modeling. I am grateful for the opportunity to have
worked with him on this project - I have learned so much.
Along this process, I have appreciated the support and encouragement of several
professors. Thank you especially to my committee of Dr. Les Werner, Dr. David Ozsvath
and Dr. Katherine Clancy. While the subject of our conversations may not have always
been this project, you have all been great mentors and were available when I needed
your assistance and suggestions.
I appreciated the funding provided through the Wisconsin DNR, University of Wisconsin
- Stevens Point, and the Portage County Land Conservation Department. The University
of Wisconsin Stevens Point Water and Environmental Analysis Lab (WEAL) ran many
analyses and I would like to thank Dick Stevens who oversees the lab along with the
team who works for him. The UWSP American Water Resources Association provided
funding which gave me the opportunity to present my work at several conferences. My
iii
lab assistant, Alicia DeGroot, was great to work with and I am appreciative of her desire
to clean lab glassware.
Lastly, I would like to thank my family and friends. My family has supported me
endlessly through all my ventures. I appreciate their openness to new ideas and the
efforts they have made to reduce the impact of our farm to the environment. The
changes in management they have made encouraged me in the pursuit of this degree.
To my friends who reminded me that there is life outside of a thesis – Thank you!!
iv
TABLE OF CONTENTS
ACKNOWLEDGMENTS................................................................................................ III
TABLE OF CONTENTS .................................................................................................. V
LIST OF FIGURES ....................................................................................................... VII
LIST OF TABLES ........................................................................................................... X
LIST OF EQUATIONS ................................................................................................... XI
ABSTRACT .................................................................................................................. 1
INTRODUCTION .......................................................................................................... 3
Purpose and Problem .................................................................................... 10
Objectives ..................................................................................................... 11
METHODS ................................................................................................................ 12
Study area ..................................................................................................... 12
Sediment collection and field sampling .......................................................... 15
Pore-water and Stream Sampling .................................................................. 17
Sorption Isotherms ........................................................................................ 18
Desorption Extractions .................................................................................. 20
Freundlich Isotherm model ........................................................................... 20
Stream P Model ............................................................................................ 23
Data Analysis ................................................................................................ 25
RESULTS AND DISCUSSION ....................................................................................... 26
Isotherms ...................................................................................................... 26
Pore- Water .................................................................................................. 35
Sediment P release model ............................................................................. 43
SUMMARY ............................................................................................................... 51
v
WORKS CITED ........................................................................................................... 54
APPENDIX A – STREAM AND SEDIMENT CHARACTERIZATION .................................... 58
APPENDIX B – DATA ................................................................................................. 60
Data for sorption isotherms and desorption extractions ................................ 60
PWE – Fe, P, Mn relationship in PWE ............................................................. 80
Pore-water ion concentrations: 3 per location ............................................... 83
Stream Ionic Concentrations ......................................................................... 88
APPENDIX C - ACRONYMS ......................................................................................... 89
APPENDIX D - PICTURES OF LOCATIONS .................................................................... 90
vi
LIST OF FIGURES
Figure 1. In-stream P processes in a flowing water system (adapted from Withers and Jarvie,
2008). .................................................................................................................................. 6
Figure 2. The diffusion of P which is thought to be dependent on the stream P concentration
where CP is the P concentration in the pore-water and CR is the P concentration in the
river. .................................................................................................................................... 7
Figure 3. Land-use and study sites within Mill Creek watershed of Portage and Wood
Counties, WI. ..................................................................................................................... 14
Figure 4. The field set-up for one transect at Stadt Road showing 3 pore-water equilibrators
and Hydrolab to collect pH, temperature and dissolved oxygen. .................................... 16
Figure 5. Pore-water equilibrator used to collect pore-water ion concentrations with depth
based on Hesslein’s (1976) design. ................................................................................... 18
Figure 6.. Data points from sorption isotherms and desorption extractions with a linear
regression of the log of the data; Q represents the change in sorption, C represents
the solution concentration; sample from Stadt Road (Sx2-3). ......................................... 22
Figure 7. Data points from sorption isotherms and desorption extractions with the
Freundlich isotherm model determined from slope and intercept of linear log plot.
The EPC is the solution concentration corresponding to a net zero change in sorption.
In theory, solution concentrations greater than the EPC have sediment sorbing P,
whereas solution concentrations less than EPC have sediment desorbing P; sample
from Stadt Road (Sx2-3). ................................................................................................... 22
Figure 8. Schematic of 2-box (water and sediment) model for Mill Creek with runoff P
entering each segment, an exchange between sediment P and stream P and some P
moving to the next segment of this 10-segment hourly model. In each segment, the P
is completely mixed. ......................................................................................................... 23
Figure 9. Range of RP, average TP and average RP during 2010 based on 24, 2, 4, 24 and 16
data points in Mill Creek for Stadt Road, Hwy K, Swedish Road, Elm Road and Hwy PP,
respectively. ...................................................................................................................... 28
Figure 10. EPC determined with Freundlich isotherm and stream RP with distance from
headwaters for Mill Creek. Stream RP values greater than the sediment EPC should
be sorbing P from the stream. .......................................................................................... 28
vii
Figure 11. Median yearly stream RP (mg P/L) versus EPC (mg P/L), by location, with a linear
trend between the median yearly RP versus the median EPC; EPC was determined
with Freundlich isotherms. ............................................................................................... 29
Figure 12. KEPC versus EPC for 27 sorption isotherms determined with the Freundlich
isotherm model by location and distance downtstream. ................................................ 32
Figure 13a-b. Pore water profiles for Stadt Road and Hwy K; 0 cm is the sediment/water
interface. ........................................................................................................................... 36
Figure 14a-b. Pore water profiles for Swedish Road and Elm Road; 0 cm is the
sediment/water interface. ................................................................................................ 37
Figure 15. 3 PW profiles at Hwy PP; 0 cm is the sediment/water interface................................ 38
Figure 16. Pore-water profile of P, Fe and Mn for an equilibrator at Stadt with
concentrations increasing around 9cm suggesting an oxidized zone 9 cm thick; 0 is
the sediment water interface, whereas negative depths are in the sediment and
positive depths are in the stream water. ......................................................................... 40
Figure 17. Pore-water profile at Elm of P, Fe and Mn with increased concentrations near the
sediment interface suggesting a very thin oxidized zone; 0 is the sediment water
interface, whereas negative depths are in the sediment and positive depths are in the
stream water. .................................................................................................................... 40
Figure 18. DO (mg/L) over 3 day 24-hour periods at all locations during sampling periods in
fall 2010 in Mill Creek taken with a MS-5 sonde. ............................................................. 42
Figure 19. DO (mg/L) measurements determined with a MS-5 sonde during summer 2010;
measurements taken on a biweekly basis at 3 locations along Mill Creek from 6am to
6pm. .................................................................................................................................. 42
Figure 20. Simulated pulse of P in the model evaluated at 35 km downstream and compared
to the simulated output. The difference reflects numerical dispersion. ......................... 45
Figure 21. Evaluation of k values (0,0.01, 0.10 and 1 m/day) at 35 km downstream with
loading reduced to half and a beginning stream P concentration of about 320 mg
P/m3. ................................................................................................................................. 46
Figure 22. Evaluation of K and depth of sediment at 35 km downstream using a lower K (0.04
m3/kg) and higher K (0.50 m3/kg) at depths of 0.03 and 0.10 meters of sediment. ........ 46
viii
Figure 23. Simulated stream P concentrations with distance downstream two months after
external P loading reduced to half of the original. ........................................................... 49
Figure 24. Simulated sediment P release over 2-year period at 70 km downstream; Load was
reduced to half and sediment interaction was considered for sediment depths of 0.03
and 0.10 m. ....................................................................................................................... 49
Figure 25. TP and RP during 2001-2002 based on 22, 4, 4, 28 and 6 data points for Stadt, K,
Swedish, Elm and Hwy PP, respectively; Measurements taken between 6am and 6pm. 58
Figure 26. Stadt Road site ............................................................................................................ 90
Figure 27. Hwy K site .................................................................................................................... 91
Figure 28. Swedish Road site ....................................................................................................... 91
Figure 29. Elm Road site............................................................................................................... 92
Figure 30. Hwy PP site .................................................................................................................. 92
ix
LIST OF TABLES
Table 1. Three day sampling periods for the five locations along Mill Creek during fall
2010. ..................................................................................................................... 17
Table 2. Freundlich isotherm model parameters determined with sorption isotherm
and desorption data. Linear log plot of Freundlich isotherm determined R 2. .... 31
Table 3. Texture and percent sand, silt, clay and organic matter for 6 samples at each
location in Mill Creek. ........................................................................................... 34
Table 4. Correlation between percent sand, silt or organic matter with KEPC or KEPC/2
using Spearman rank order correlation. ............................................................... 35
Table 5. Summary of variables and sources of model inputs for sediment release
model for Mill Creek. ............................................................................................ 43
Table 6. Recorded temperature and pH over 3-daysampling period and during
isotherm experiment. ........................................................................................... 59
x
LIST OF EQUATIONS
(1) Freundlich isotherm determination…………………………………………………….……………. 21
(2) Slope of line tangent to Freundlich equation…………………………………………………….. 21
(3) Model: P mass on sediment………………………………………………………………………………. 24
(4) Model: Pore-water P concentration………………………………………………………………….. 24
(5) Model: Stream water P mass…………………………………………………………………………….. 24
(6) Model: Convert P stream water mass to concentration……………………………………….. 24
xi
ABSTRACT
This research characterized the sorption of P by sediment in Mill Creek, of Portage and
Wood counties, Wisconsin. Mill Creek is an impaired stream where the sediment has
been exposed to high P concentrations for at least 10 years. P sorption is important
because the release of P from stream sediments could prolong efforts to reduce P
concentrations in streams. This research can be used to estimate how long sediment P
release would affect stream P concentrations after a reduction in P inputs.
Laboratory sorption and desorption experiments evaluated the buffering of P with
sediment. Mill Creek was sampled at five locations. Each location had a different
dissolved P concentration.
The results showed a decrease in EPC (equilibrium P
concentration) with a decrease in stream P concentration. The sorption/desorption
measurements were combined and fit to a non-linear Freundlich isotherm model. The
KEPC (change in sorption at EPC) had an inverse relationship with EPC. While there were
differences in the EPC and KEPC values between locations, the results showed that the
sediment along Mill Creek had a relatively similar buffering capacity if exposed to similar
stream P concentrations. The different EPC and KEPC values between locations could be
due to the different ranges of stream P concentrations the sediments have been
exposed to.
1
A simulation model was developed to predict how the sediment P released over time
could influence stream P concentrations. The characteristics of the sediment were
based on a linear fit to the Freundlich curve at the concentration of interest. Freundlich
curves were based on both the P desorption and sorption data. The sediment layer
used in the simulation was representative of the oxic sediment layer as determined with
pore-water equilibrators. The simulation suggests sediments could have an effect on
stream P concentrations after a reduction in external loading but the duration may only
be a few years. That time could be increased with greater stream P reductions, slower
desorption rates or if there are large areas of transient flow.
2
INTRODUCTION
Eutrophication is a widespread problem in aquatic ecosystems around the world (NRC,
1993) and accounts for 60% of impaired river reaches in the United States (USEPA,
2009). A river is considered impaired if it does not meet water quality standards set by
the state. Eutrophication can reduce the use of water for drinking, industry, agriculture
and recreation.
While both nitrogen (N) and phosphorus (P)
are of concern, in
freshwater systems, P is usually the limiting nutrient that leads to eutrophication (Fang
et al., 2005).
Characteristics of eutrophication are excessive biological growth and low dissolved
oxygen (DO) in a stream. P is a naturally occurring element in our environment that is
used by plants for the formation of more plant life (Conley et al., 2009). With an
increase in nutrient loads, biological productivity is increased and more plant life is
created (Kovar and Pierzynski, 2009). An increase in plant life results in higher rates of
respiration, which can lower dissolved oxygen concentrations (Sharpley et al., 2003).
The reduced oxygen provides an undesirable habitat.
Increased P can come from point and non-point sources. A point source is a known
specific source where the P load is measurable, such as a wastewater treatment plant
(WWTP). A non-point source comes from many combined sources and the P load from
each specific area is not measureable, such as runoff during a rain event. Since the
3
Clean Water Act in 1972, there has been substantial progress in reducing point sources
of pollution, such as WWTPs. Because non-point sources of pollution do not have a
specific source, they have been difficult to monitor and regulate.
P stored in the sediment may be an important source of P. More studies on sediment P
release have focused on lakes and larger water bodies rather than streams. A study by
Carpenter (2005) found that a Wisconsin lake affected by eutrophication due to
agricultural runoff could potentially take 1,000 years to recover from over-enrichment.
A study by Laukkanen et al. (2009) incorporated sediment P release into a simulation of
the Baltic Sea, which has seen reductions to P inputs, but has not seen a decrease in
eutrophication. A study on river sediment P by McDaniel et al. (2009) found the
sediment may affect stream P concentrations during low discharge but is unlikely to
alter annual P loads, but this assessment did not look at a decrease of P inputs.
Little is known about the impact of sediment P to stream P concentrations after a
reduction in point or non-point sources of P. Assuming sediment P is in equilibrium with
stream P, a reduction in stream P could then lead to a release of P from sediments after
a reduction in external loads. This release of P could then sustain high stream P
concentrations after a reduction in external P loads.
The release of P from sediment is complex. P transfers between the sediment, the porewater around the sediment and the stream water depending on stream conditions. As
4
factors such as oxygen or stream P concentration change, there could be a change in the
relationship between P in the pore-water, P in the stream and P on the sediment. Add
in plants and microbial influences that are continuously using, moving or releasing P,
and the interaction becomes increasingly complex.
P is characterized as dissolved or particulate by passage through a 0.45µm filter (Wetzel
and Likens, 2000). The inorganic forms include H2PO4- and HPO42-, which can be readily
assimilated by bacteria, plants and algae (Correll, 1998). Many dissolved forms of P
react with an ammonium molybdate complex that is the basis for a colorimetric analysis
method (Murphy and Riley, 1962). These reactive forms are often referred to as
dissolved reactive P (RP). Although much of the dissolved P that passes through a
0.45μm filter is reactive, it has been found that some is not reactive (Turner and
Haygarth, 2002). The particulate P includes organic, mineral and sorbed P. It can be
converted to bio-available P (Bridgham et al., 2001). Bio-available PP represents a
variable (10-90% of PP) but long-term source of P for algal uptake (Dorich et al., 1985).
Figure 1 is an overview of the processes controlling stream P concentrations. Both point
and non-point sources deliver P to a stream as dissolved and PP. The dissolved P is
available for biological uptake and reaction with the sediment. The PP can remain
suspended and be carried downstream or settle in the stream. It is thought that the
suspended PP quickly comes into equilibrium with the stream water P (House et al.,
1998; James and Barko, 2004). The sediment that settles to the streambed provides an
5
additional source of P, and interacts with the stream by means of sorption and
desorption of P.
Figure 1. In-stream P processes in a flowing water system (adapted from Withers and Jarvie, 2008).
Sediment pore-water is the link between sediment P and stream water P. When the
stream P is less than the pore-water P, the pore-water P diffuses to the stream. This
allows sediment P to desorb into the pore-water. When stream P concentrations are
6
higher than pore-water P concentrations, the stream P diffuses into the pore-water and
increases the pore-water concentration (Hoffman et al, 2009). The sediment then acts
like a sink for the pore-water P (Figure 2). This reaction of P with sediment has become
known as the phosphate buffer mechanism (Froelich, 1988).
Figure 2. The diffusion of P which is thought to be dependent on the stream P concentration where CP is
the P concentration in the pore-water and CR is the P concentration in the river.
The sorption of P has been described as a two-step process. The process starts with fast
kinetics on the sediment surface followed by slow kinetics to the interior of the particle
(Barrow, 2008). Fast kinetics occur within hours, whereas slow kinetics can take from
weeks to months (Froelich, 1988; Holton et al., 1988). P interactions with the sediment
surface are often referred to as adsorption whereas P interactions with the particle
interior are referred to absorption. In this paper, there is no distinction between
7
adsorption and absorption, instead P attaching to the sediment will be referred to as
sorption.
Other processes can control the exchange of P between stream and pore-water. When
an oxidized sediment surface layer is present, P can be retained in the sediment through
sorption to Fe oxides (Jensen et al., 1995; Krom and Berner, 1980; Sundby et al., 1992).
These oxidized sediments can create a barrier that slows underlying diffusing phosphate
from reaching the overlying water column (Correll, 1998; Correll, 1999).
In the
underlying reduced sediments, ferric (Fe3+) iron becomes ferrous (Fe2+) iron and
phosphate is often released. The result is less P sorbed to the sediments (Krom and
Berner, 1980) and a higher concentration of dissolved P. The high pore-water P can be
prevented from moving into the stream by the oxic sediment layer.
The sediment pore-water P concentration is controlled by the exchange between sorbed
and solution P. Sorption measurements can be used to evaluate this sediment P
buffering. A sorption isotherm compares the solution P concentration to the change in
P sorption. The solution P concentration when there is no net change in sorption is the
equilibrium P concentration (EPC) (Froelich, 1988). The slope of the isotherm, or K,
represents the buffering of P by the sediment. A higher K value represents sediment
that gives off more P with a smaller change in stream P concentration than a lower K.
8
Researchers have used linear and non-linear sorption isotherms to estimate the
buffering of sediment P and the EPC (Froelich, 1988; Barrow, 2008).
A linear
relationship assumes the buffering capacity is similar at all solution P concentrations
while a non-linear relationship indicates a different buffering capacity at different
solution P concentrations. To isolate the desorbing portion of the isotherm, researchers
have used various methods including fitting a linear relationship to the lower solution
concentrations (Haggard et al., 2007) or relating soil composition to the soil’s ability to
desorb P (Edis et al., 2002).
The connection between the stream and sediment can be explored by measuring porewater concentrations. The profile of pore-water P, Fe and Mn concentrations with
depth can be used to estimate the location of an oxygenated boundary. Generally,
increased levels of P, Fe and Mn are present in oxygen-depleted sediment (Slomp et al.,
1998). The sediment becomes anoxic around the depth when there is an increase in the
dissolved P, Fe and Mn concentrations. Anoxic conditions below an oxygenated layer
could lead to increased rates of P release (Schindler, 2005; Fillos and Swanson, 1975). A
profile with a high dissolved P, Fe and Mn concentrations at the surface, has a very thin
or non-existent oxygenated boundary layer (Sundby et al., 1992).
When an oxic
boundary is thin or nonexistent, the flux of P is not limited and P can diffuse to the
stream (Sundby et al.,1992).
9
Purpose and Problem
Stream sediment P has the potential to prolong the presence of high P concentrations in
a stream following decreases in point or non-point sources of P. The US EPA has been
encouraging states to develop nutrient criteria for streams (USEPA, 2011). Wisconsin,
for example, just published P concentration standards for surface waters, including
streams (NR 102, 2010).
The sediment release of P could present an important
impediment to meeting these water quality standards. The purpose of this research is
to investigate stream sediment P and the effect on stream P concentrations.
The focus of this study was Mill Creek in Central Wisconsin. This stream was selected
due to its relatively high P concentrations and likely long sediment exposure to those P
concentrations. Mill Creek is on the EPA’s 303(d) list of impaired streams for high
nutrient concentrations and low dissolved oxygen. The results of this study will be
useful in developing a strategy to reduce the P concentrations in Mill Creek.
10
Objectives
The objectives of this study are to:
 Characterize the extent to which P sorbs/desorbs from stream sediments in Mill
Creek and determine if P sorption relates to stream P concentrations in Mill Creek
 Estimate the size of the oxic P reservoir in the Mill Creek stream sediment
 Determine the extent to which sorbed P could slow the reduction of stream P
concentrations after changes in external loading
11
METHODS
Study area
Mill Creek, shown in Figure 3, is in Portage and Wood Counties of Wisconsin. The
stream discharges to the Wisconsin River. Excessive nutrients in Mill Creek have led to
excessive plant growth. Due to respiration of plants, the stream exhibits large diurnal
variations in oxygen. The nutrient sources in Mill Creek include both wastewater
treatment plants (WWTP) and agricultural runoff.
Five sample sites were used along Mill Creek. These were, from west to east, Stadt
Road, Hwy K, Swedish Road, Elm Road and Hwy PP. Stadt and Elm Roads have historical
data for discharge, total phosphorus (TP) and RP collected by the United States
Geological Survey (USGS) in 2001-2002. A USGS station began operating in June 2010 at
Hwy PP, and is currently collecting daily discharge and biweekly measurements of TP
and RP. The average TP concentrations at Stadt and Elm Roads in 2002 were 0.51 mg/L
and 0.30 mg/L, respectively (Oldenburg, 2005). These concentrations are higher than
the Wisconsin P criteria of 0.075 mg/L for streams (NR 102, 2010).
Five wastewater treatment plants contribute discharge to Mill Creek upstream of Elm
Road. The cities that contribute P to Mill Creek are Marshfield, Hewitt, Junction City,
Milladore, Blenker and Sherry. In 2002, these plants served approximately 20,000
people and the annual TP load to Mill Creek was 3,886 kg/year (Oldenburg, 2005). The
12
WWTPs make up about 39% of the P load at Stadt Road and is diluted by other additions
to about 14% of the P load at Elm Road (Oldenburg, 2005).
Non-point agricultural runoff also contributes to the Mill Creek P load. The 337-km2
watershed is predominately rural and approximately 45% of the land use is agriculture.
Based on the National Agricultural Survey Statistics (NASS) for 2008, the agricultural
land is primarily corn, alfalfa and pasture.
A physical inventory of Mill Creek was compiled in 2005 (GSRCD, 2006). The agricultural
area around Stadt Road has been ditched to drain the cropland into Mill Creek. This
results in runoff quickly entering the stream.
The streambed is characterized by
particles less than 2mm in diameter (sands, silts and clays). There is dense vegetation
(primarily Elodea canadensis and Lemna minor) in the upper reaches of the stream and
very little in the lower reaches. At Hwy K and Swedish Road, the stream begins to
meander. The substrate becomes coarser, with some cobbles or scattered boulders and
about 80% of the streambed is less than 2mm. At Elm Road and Hwy PP, there are large
boulders in the stream and less areas of deposited sediment.
13
Figure 3. Land-use and study sites within Mill Creek watershed of Portage and Wood Counties, WI.
14
Sediment collection and field sampling
Sediment samples were collected along Mill Creek at Stadt Road, Hwy K, Swedish Road,
Elm Road and Hwy PP. The top 3-4 cm of sediment was sampled because previous
research suggested that is the active layer (Reynolds and Davies, 2001). Transects were
perpendicular to stream flow at all locations except Hwy PP where the stream was not
wadeable, so transects were on either side of the stream and parallel to stream flow
within 1 meter of stream edge.
Along each transect, three sediment samples were collected at uniform spacing. Rather
than homogenize the samples within a short stream reach as others have done (Jarvie et
al., 2005; McDaniel et al., 2009), each sample was tested separately to determine the
sorption characteristics. After collection, the samples were wet sieved through a 2mm
sieve and stored at 4
Sediment texture was determined using methods from Gee and
Bauder (1986).
Water samples were collected before and after a three-day monitoring period. These
samples were analyzed for major ions, N and P. TP and RP were analyzed using a flow
injection analyzer (Lachat, Loveland CO). Major ion concentrations were analyzed using
Inductively Coupled Plasma spectrometry (Varian Vista ICP-OES, Santa Clara CA).
Streamflow was measured using a Flowtracker (Sontek, San Diego CA) at the beginning
and end of the sampling period. A Hydrolab MS-5 (Hach Inc., Loveland CO) monitored
15
pH, dissolved oxygen (DO) and temperature and pore-water equilibrators were used to
measure pore-water chemistry.
The pore-water equilibrators were constructed to
mimic the design proposed by Hesslein (1976). The sampling dates for each location are
shown in Table 1. Figure 4 shows a typical field sampling arrangement.
Pore-water Equilibrators
Hydrolab
Figure 4. The field set-up for one transect at Stadt Road showing 3 pore-water equilibrators and Hydrolab
to collect pH, temperature and dissolved oxygen.
16
Table 1. Three day sampling periods for the five locations along Mill Creek during fall 2010.
Location
Stadt
Hwy K
Swedish
Elm
Hwy PP
Distance from
headwaters (km)
4
18
29
47
57
Begin date
9/2/2010
11/1/2010
9/6/2010
9/13/2010
10/4/2010
End date
9/5/2010
11/4/2010
9/9/2010
9/16/2010
10/7/2010
Pore-water and Stream Sampling
Pore-water equilibrators (“peepers”) were used to measure pore-water chemistry with
depth in the sediment (Hesslein, 1976). The peepers were constructed from 2×10×50
cm blocks of acrylic with twelve horizontally milled 8-cm3 cells (Figure 5). The cells were
filled with de-ionized water purged with nitrogen and a 0.2µm filter was used to cover
the cells.
To maintain anoxic conditions during transportation, equilibrators were
placed in a tub of de-ionized water that was purged with nitrogen gas for one hour.
At each location, three equilibrators were spaced across the stream parallel to stream
flow. Equilibrators were placed close to transects where the sediment was deep enough
to get a profile that included at least eight cells. They were left for three days.
According to Webster et al. (1998), three days is sufficient time to achieve 90% of the
equilibrated dissolved ions through molecular diffusion.
After the equilibration period, samples were extracted by pipette. To reduce aerobic
influence on iron, samples were extracted from the cells within 5 minutes and placed in
17
10 ml vials with a drop of nitric acid. The UWSP-Water and Environmental Analysis Lab
(WEAL) analyzed samples on an ICP to determine the primary ions.
Figure 5. Pore-water equilibrator used to collect pore-water ion concentrations with depth based on
Hesslein’s (1976) design.
Bi-weekly water sampling was performed at Stadt Road, Elm Road and Hwy PP. At Hwy
PP, samples were collected by the Center of Watershed Development at the University
of Wisconsin – Stevens Point (UWSP) in cooperation with the USGS from April 2010 into
2011. Sampling at Stadt and Elm Roads occurred between April and October of 2010.
Water samples were analyzed by the UWSP–WEAL to determine TP, RP and total
suspended solids.
Sorption Isotherms
Methods adapted from Kovar and Pierzynski (2009) were used to develop the sorption
isotherms. Approximately 1.5 g of sediment was mixed with approximately 30 ml
phosphate solution. Initial P concentrations of 0, 0.1, 0.25, 0.5, 0.75 and 1 mg/L (made
18
in solutions of 0.001M CaCl2 & 0.001M NaHCO3) were added to the sediment in a 50 ml
centrifuge tube.
The sediment to solution ratio and solution ion chemistry can affect the results of the
sorption isotherms (Falkiner, 1997; Taylor, 1971; White, 1966).
Preliminary tests
evaluated the effect of solution and sediment to solution ratios and led to the selected
experimental conditions.
The solution of 0.001M CaCl2 and 0.001M NaHCO3 was
designed to mimic stream ion chemistry. Using 1.0-1.5 g sediment with solution created
a sediment to solution ratio of 1:20 and it has been recommended to use a sediment to
solution ratio less than 1:50 (White, 1966). Initial P concentration were between 0 to 1
mg/L because the expected EPC concentrations were between 0 and 1 mg P/L.
Tubes were rotated slowly, end-over-end, for 24 hours and then centrifuged for 15
minutes. Supernatant samples were filtered with a 0.45 µm filter, and after 20 minutes
analyzed with colorimetric methods (Murphy and Riley, 1962) on a Novaspec II
(Pharmacia Biotech) spectrophotometer at 880nm. Quality control consisted of periodic
comparisons to samples analyzed by the UWSP - WEAL.
After the isotherm experiment, the sediment samples were oven dried at 60oC for 24
hours and the weight recorded to determine the dry sediment mass. Samples were
then combusted in a muffle furnace at 550oC for 5 hours and the weight recorded to
determine the percentage of organic matter by loss on ignition.
19
Desorption Extractions
Moist sediment was sequentially extracted (Hooda et al., 2000; Jarvie et al., 2005) eight
times with a 1:20 soil to solution (0.001M CaCl2 & 0.001M NaHCO3) ratio for one hour
and the mass of P extracted was determined. Air was lightly bubbled into the solution
to simulate movement of water. Supernatant samples were filtered through a 0.45 µm
filter and analyzed colorimetrically. Similar to the sorption experiment, after the last
extraction, the sediment samples were oven dried and then combusted in a muffle
furnace.
Freundlich Isotherm model
The results of the sorption and desorption extractions were combined and expressed as
the mass of P sorbed or desorbed at the final solution concentration. The data was nonlinear and the Freundlich isotherm model was utilized. Although most P sorption
studies have used a linear isotherm, a few have used the non-linear Freundlich model
(Jarvie et al., 2005, Torrent and Delgado, 2001).
To estimate the parameters for a Freundlich model, a linear regression was fit to the log
transformed data, as shown in Figure 6. The change in sorption (Q) had negative values
representing P desorbed, so an arbitrary constant of 70 was added to make all values
positive. The slope (n) and intercept (Kf) of the log linear regression provided parameter
estimates in the Freundlich isotherm model:
20
Q = Kf(C)n
(1)
The slope of the P sorbed versus solution concentration is the buffering ability of the
sediment or K (L/kg). The slope of a non-linear isotherm varies with concentration
(Figure 7). The slope was calculated from the derivative of the Freundlich Isotherm
model at a solution concentration (Equation 2) (Zhang and Huang, 2011).
K = nKf(C)n-1
(2)
The slope, K, was evaluated at the EPC (KEPC), half the EPC (KEPC/2), 0.01 mg P/L (K0.01) and
0.6 mg P/L (K0.6). KEPC represents the slope of the isotherm when the sediment is in
equilibrium (no net sorption or desorption), whereas KEPC/2 represents sediment
buffering after a reduction in stream P concentrations. The K evaluated at K0.01 and K0.6,
represent the sediment P buffering at each of those solution concentrations.
21
1.92
Sorption isotherms
Desorption extractions
Log (Q +70)
1.88
log (Q+70) = (0.072*log C) + 1.90
R² = 0.91
1.84
1.8
1.76
-1.8
-1.6
-1.4
-1.2
-1
-0.8
-0.6
Log solution concentration (log C)
-0.4
-0.2
0
Figure 6.. Data points from sorption isotherms and desorption extractions with a linear regression of the
log of the data; Q represents the change in sorption, C represents the solution concentration;
sample from Stadt Road (Sx2-3).
Change in sorption (mg P/kg
sediment); Q
10
5
0
Sorbing
Desorbing
EPC
Sorption Isotherms
Desorption Extractions
Freundlich Isotherm
-5
-10
Q= 78.7C0.072
R2 = 0.91 (log linear regression)
-15
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Solution Concentration (mg P/L)
Figure 7. Data points from sorption isotherms and desorption extractions with the Freundlich isotherm
model determined from slope and intercept of linear log plot. The EPC is the solution
concentration corresponding to a net zero change in sorption. In theory, solution
concentrations greater than the EPC have sediment sorbing P, whereas solution concentrations
less than EPC have sediment desorbing P; sample from Stadt Road (Sx2-3).
22
Stream P Model
To predict P concentrations after a reduction in P inputs, a two-box numerical
simulation model was constructed. One box was the sediment and the other was the
stream water. Each box was assumed to be completely mixed. Ten longitudinal
segments represented the 70 km stream. Lateral inflow was incorporated into each
segment. This was adjustable to allow for reductions in runoff P concentrations. The P
load moves downstream with an exchange between sediment and stream water
occurring in each segment and each hour for 2 years (Figure 8).
Figure 8. Schematic of 2-box (water and sediment) model for Mill Creek with runoff P entering each
segment, an exchange between sediment P and stream P and some P moving to the next
segment of this 10-segment hourly model. In each segment, the P is completely mixed.
23
Four equations create the hourly simulation of sediment P interaction with the stream.
The P mass on sediment (1) uses a concentration difference between the stream and
pore-water P concentration. The pore-water P concentration (2) is a function of the
sediment P mass and its relationship to the pore-water. The mass of stream water P (3)
combines the P mass into the segment with sediment exchangeable P and subtracts the
P mass leaving the segment. The P concentration of the stream (4) converts the stream
P mass to a concentration.
P mass on sediment:
(1)
Pore-water P concentration:
(2)
Stream P mass:
(3)
Stream P concentration:
(4)
Where:
t = time-step (hour)
Ms = Mass of P in sediment (mg)
k = mass transfer coefficient (m/hour)
= Concentration of P in river (mg/m3)
= Concentration of P in pore-water (mg/m3)
Vs = Volume of sediment (m3)
K = Relationship between pore-water P concentration to mass of P on sediment (m3/kg)
Vp = Volume of pore-water (m3)
= bulk density (kg/m3)
24
= Porosity
Mr = Mass of P in river (mg)
Qin = Discharge (m3)
CI = Concentration of P in runoff (mg/m3)
Qout = Discharge moving to next segment (m3)
As = Surface area of sediment (m2)
Vr = Volume of river (m3)
Data Analysis
SigmaStat 11.0 was used to perform regression analyses, rank sum tests, post-hoc tests,
and correlations. A linear regression of the log transformed isotherm data was used to
determine the slope and intercept for the Freundlich isotherm model. The KruskalWallis test was used as a non-parametric ANOVA. Tukey’s and Dunn’s test were posthoc tests which used the difference in rank to determine if pair-wise comparisons were
significantly different. A Wilcoxon signed rank test compared the Freundlich isotherm
to the linear isotherm, which were both developed from the same laboratory results.
Spearman’s rank order was used for correlations.
25
RESULTS AND DISCUSSION
Isotherms
The results of fitting the Freundlich equation to the isotherm measurements are shown
in Table 2, along with the goodness of fit (R2) of the isotherms. The R2 was based on the
linear regression of the log-transformed data. The sorption isotherms and desorption
extractions provided 6 and 8 data points, respectively, to fit the Freundlich equation at
each location. Three isotherm locations with R2 values less than 0.50 were removed
from the analyses. Of the remaining 27 locations, 19 individual data points were
removed using Studentized Residuals before isotherm models were fit. Sorption and
desorption results are listed in Appendix B.
The equilibrium phosphorus concentration (EPC) was compared within and between
sites in Table 2. Within each site, the EPC was sectioned into three groups by location
along transects and the Kruskal-Wallis tests showed there were no statistical differences
(P>0.05) in the EPC within each site. A Kruskal-Wallis test revealed a significant effect
on EPC between the different sites (H(4)=22.76, P=<0.001). A post-hoc Tukey’s test
showed the EPC was statistically higher at Stadt Road than Hwy PP and Swedish Road
(P<0.05). There were no statistical differences between EPC at Hwy K, Swedish Road,
Elm Road or Hwy PP (P>0.05).
26
The EPCs ranged from 0.02 to 0.30 mg P/L.
The EPC represents the stream P
concentration when the stream sediment is neither sorbing nor desorbing P. At Hwy PP,
a stream P concentration less than the EPC of 0.02 mg P/L would result in desorbing P
and more than 0.02 mg P/L would result in sediment sorbing P. Stadt Road, with a
median EPC of 0.30 mg P/L, would have sediment sorbing P at stream P concentrations
greater than 0.30 mg P/L and desorbing sediment P at stream P concentrations less than
0.30 mg P/L.
Within Mill Creek, there is a range in the EPC and RP. In Figure 9, the stream RP
concentrations range from about 0.40 mg P/L at Stadt Road to about 0.16 mg P/L at
Hwy PP. The range of RP and TP concentrations are also shown for each location. In
Figure 10, the average stream RP concentrations over the sampling period were higher
than the median EPC at all sites except Elm Road, where the median EPC and median RP
were about equal. The ranges in EPC and RP at each location suggest there is some
variation in loading.
The median EPC was positively correlated with the median stream RP in Figure 11
(P<0.05; R2=0.75).
Others have found positive correlations between RP and EPC
(Haggard et al., 2007; Jarvie et al., 2005; McDaniel et al., 2009).
This positive
relationship suggests the sediments are close to equilibrium with the stream.
27
0.8
P concentration (mg/L)
Range of RP
Average TP
Average RP
0.6
0.4
0.2
0.0
Stadt
Hwy K
Swedish
Elm
Hwy PP
Figure 9. Range of RP, average TP and average RP during 2010 based on 24, 2, 4, 24 and 16 data points in
Mill Creek for Stadt Road, Hwy K, Swedish Road, Elm Road and Hwy PP, respectively.
Concentration (mg P/L)
0.5
All EPC values
Median EPC
Median RP (2010)
Avg RP (sampling period)
0.4
0.3
0.2
0.1
0.0
0
10
20
30
40
50
60
Distance from headwaters (km)
Figure 10. EPC determined with Freundlich isotherm and stream RP with distance from headwaters for
Mill Creek. Stream RP values greater than the sediment EPC should be sorbing P from the
stream.
28
0.5
Stadt Road (4km)
Hwy K (18 km)
Swedish Road (29 km)
0.4
Elm Road (47 km)
EPC (mg P/L)
Hwy PP (57 km)
Median RP vs median EPC
0.3
median EPC =(0.89*median yearly RP) - 0.08; R² = 0.75
0.2
0.1
0.0
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
RP(mg/L)
Figure 11. Median yearly stream RP (mg P/L) versus EPC (mg P/L), by location, with a linear trend
between the median yearly RP versus the median EPC; EPC was determined with Freundlich
isotherms.
The characteristics of the sorption isotherms were evaluated at the different locations.
The K is the change in sorbed P concentrations with a change in the solution P
concentration. Table 2 shows the KEPC and KEPC/2 were statistically higher at Hwy PP (173
L/kg) compared to Stadt Road (19 L/kg) (P<0.05). There were no other statistically
significant differences between any other sites (P>0.05). The median KEPC values for
Hwy K, Swedish Road and Elm Road were 22, 41 and 55 L/kg, respectively. The KEPC/2
was about double the KEPC for most sediment samples and exhibited the same statistical
relationship as KEPC. These results are consistent with a non-linear sorption isotherm.
29
K was also evaluated at specific concentrations of 0.01 and then at 0.6 mg P/L using the
slope of the Freundlich isotherm. The results in Table 2 show no statistical differences
between the locations at K0.01 (median: 328 L/kg) or K0.06 (median: 7 L/kg) (P>0.05).
With no statistically significant differences between K0.01, the sediments along Mill Creek
would buffer similar amounts of P if subjected to a solution concentration of 0.01 mg
P/L. The same is true if the sediments were exposed to a solution concentration of 0.6
mg P/L.
There was no significant difference between the EPC determined with the Freundlich
isotherm and the EPC determined with linear sorption isotherms (P>0.05), but there was
a significant difference in K (P<0.001). The similar EPC values is expected, as both the
Freundlich and linear models provide a relatively good fit across the concentration
range near the EPC. The KEPC and KEPC/2 of the Freundlich isotherms were significantly
higher than the K of the linear sorption isotherm (KEPC: Z= -3.7, P<0.001; KEPC/2: Z=-4.541,
P<0.001), which points out the importance of using a non-linear sorption relationship.
30
Table 2. Freundlich isotherm model parameters determined with sorption isotherm and desorption data. Linear
2
log plot of Freundlich isotherm determined R .
Site
(Distance
Downstream)
Stadt
2
Road
(4 km)
2
Hwy K
(18 km)
Swedish
2
Road
(29 km)
Elm
2
Road
(47 km)
2
Hwy PP
(57 km)
1
*
n
Sample
SX1-1
SX1-2
SX1-3
SX2-1
SX2-2
SX2-3
median
KX1-1
KX1-2
KX1-3
KX2-1
KX2-2
KX2-3
median
SwX1-1
SwX1-2
SwX1-3
SwX2-1
SwX2-2
SwX2-3
median
1
EX1-1
EX1-2
EX1-3
EX2-1
EX2-2
EX2-3
median
PPX1-1
PPX1-2
PPX1-3
PPX2-1
1
PPX2-2
1
PPX2-3
median
Q = Kf C
Kf
n
73.5 0.068
75.0 0.063
110.2 0.308
73.6 0.041
80.0 0.111
78.7 0.072
75.5
75.7
81.0
75.5
74.4
93.3
0.031
0.043
0.053
0.037
0.031
0.088
77.1
77.5
79.2
78.7
74.0
84.9
0.052
0.044
0.044
0.040
0.018
0.058
102.6
147.3
867.0
76.1
79.0
79.0
0.133
0.286
0.943
0.046
0.062
0.041
77.0
83.4
98.0
107.6
100.5
77.8
0.025
0.047
0.098
0.115
0.103
0.029
Freundlich isotherm
a
b
b
EPC
KEPC
KEPC/2
2
R
mg P/L L/kg
L/kg
0.55
0.48
10
31
0.76
0.34
13
28
0.72
0.23
94
94
0.49
0.30
10
19
0.82
0.30
26
48
0.91
0.20
26
49
0.30
19
40
0.70
0.09
25
53
0.75
0.16
19
37
0.79
0.06
58
118
0.90
0.13
20
39
0.88
0.14
16
32
0.78
0.04
162
291
0.11
22
46
0.73
0.15
24
47
0.91
0.10
31
60
0.90
0.06
52
100
0.83
0.05
53
104
0.71
0.04
28
62
0.84
0.04
114
257
0.06
41
81
0.30
0.06
165
303
0.82
0.07
270
461
0.57
0.07
952
990
0.63
0.16
20
39
0.92
0.14
31
59
0.73
0.05
55
111
0.07
55
111
0.57
0.02
83
163
0.64
0.02
136
265
0.71
0.03
211
426
0.63
0.02
340
627
0.40
0.03
240
449
0.35
0.03
78
152
0.03
173
345
2
c
K0.01
L/kg
365
355
821
251
534
405
385
203
268
335
238
198
548
253
315
279
285
261
122
257
270
739
1129
1063
282
369
267
369
169
316
613
729
646
197
527
c
K0.6
L/kg
8
8
48
5
14
9
9
4
5
7
5
4
13
5
6
6
6
5
2
8
6
21
61
842
6
8
5
8
3
6
15
19
16
4
11
Linear
**
isotherm
d
EPC
mg P/L
0.49
0.41
0.11
0.29
0.33
0.25
0.31
0.11
0.10
0.08
0.20
0.20
0.04
0.11
0.15
0.08
0.05
0.05
0.06
0.06
0.06
0.05
0.06
0.04
0.12
0.11
0.03
0.06
0.04
0.05
0.04
0.05
0.02
0.06
0.05
Samples removed from analysis because R <0.5
Within locations: grouped by location along transect; no statistical difference in EPC or KEPC (Kruskal-Wallis; P>0.05)
a
Stadt Road EPC significantly higher than Hwy PP and Swedish Road (H=22.030(4), P<0.001; Tukey’s test: P<0.05)
b
Hwy PP significantly higher K than Stadt Road (H=10.379(4), P=0.035, Tukey’s test: P<0.05)
c
No significant difference K0.01 or K0.6 between locations (K0.01: H(4)=6.717, P=0.152; K0.6: H(4)=6.022, P=0.198)
d
No significant difference between Freundlich determined EPC and linear isotherm determined EPC (Z= 0.721, P=0.478)
e
KEPC and KEPC/2 were significantly higher than linear isotherm K (KEPC: Z= -3.7, P<0.001; KEPC/2: Z=-4.541, P<0.001 )
*
Sorption and desorption data
**
Only sorption data
2
31
e
K
L/kg
17
14
21
17
30
18
18
20
12
67
13
9
93
17
22
19
24
34
15
67
23
146
220
617
8
15
30
30
13
39
183
335
228
804
111
Jarvie et al. (2005) found relationships between high K and low EPC values using
Freundlich isotherm models. Figure 12 shows the inverse relationship between K and
EPC at the different sites along Mill Creek. The location with a higher stream P
concentration, Stadt Road, had higher EPC and lower K values than Hwy PP, which had a
lower stream P concentration. This implies that sediments exposed to higher stream P
concentrations are less able to buffer P than sediments exposed to lower stream P
concentrations. This is consistent with the non-linear sorption relationship found.
KEPC (mg P/kg sediment)
1000
Stadt Road (4km)
Hwy K (18 km)
Swedish Road (29 km)
Elm Road (47 km)
Hwy PP (57 km)
100
10
1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
EPC (mg/L)
Figure 12. KEPC versus EPC for 27 sorption isotherms determined with the Freundlich isotherm model by
location and distance downtstream.
32
The similarity of K0.01 and the K0.6 at different locations along with the inverse
relationship between K and EPC suggest the stream P could be affecting the sediments
buffering capacity. The Stadt Road location is closest to the MWWTP and the sediment
is continuously exposed to higher concentrations of P. These high concentrations lead
to sediments that have a higher concentration of sorbed P and a lower buffering
capacity. At the Hwy PP location, the range in solution P concentration is generally
lower and the lower sediment P concentrations leads to a higher buffering capacity.
33
The sediment composition is listed in Table 3. The sediment were similar and composed
of about 90% sand, 9% clay and 1% silt. The organic matter content ranged from 0.12%
to 1.97%.
Table 3. Texture and percent sand, silt, clay and organic matter for 6 samples at each location in Mill
Creek.
Stadt (4 km)
K (18 km)
Swedish (29 km)
Elm (47 km)
PP (57 km)
SX1-1
SX1-2
SX1-3
SX2-1
SX2-2
SX2-3
KX1-1
KX1-2
KX1-3
KX2-1
KX2-2
KX2-3
SwX1-1
SwX1-2
SwX1-3
SwX2-1
SwX2-2
SwX2-3
EX1-1
EX1-2
EX1-3
EX2-1
EX2-2
EX2-3
PPX1-1
PPX1-2
PPX1-3
PPX2-1
PPX2-2
PPX2-3
% Sand
90
89
88
88
85
89
91
91
91
92
93
92
87
87
89
88
88
89
89
90
91
89
91
90
85
88
90
90
88
88
% Silt
1
3
1
4
6
3
1
0
1
0
0
0
5
5
0
1
1
0
5
1
0
0
0
0
4
1
0
0
1
1
34
% Clay
9
9
11
9
9
9
7
9
7
8
7
8
8
8
11
11
11
11
6
9
9
11
9
10
11
11
10
10
11
11
Texture
S
S
LS
S
LS
S
S
S
S
S
S
S
LS
LS
LS
LS
LS
LS
S
S
S
LS
S
S
LS
LS
LS
S
LS
LS
% Organic Matter
0.49
0.41
0.12
0.26
0.34
0.23
1.97
0.93
0.54
0.40
1.12
0.63
0.32
0.28
0.19
0.53
0.22
0.36
1.31
1.54
1.27
0.36
0.30
0.33
0.55
0.49
0.55
0.94
0.77
1.17
A Spearman rank order correlation coefficient was computed to assess the relationship
between K and percent sediment composition. In Table 4, there was no correlation
between the percent silt, clay or organic matter with KEPC or KEPC/2 (p>0.05, n=27).
Table 4. Correlation between percent sand, silt or organic matter with K EPC or KEPC/2 using Spearman rank
order correlation.
Correlation
Coefficient (r)
p-value
% Silt
K @ EPC
K @ half
-0.222
-0.222
0.264
0.262
% Clay
K @ EPC
K @ half
0.175
0.193
0.380
0.332
% Organic Matter
K @ EPC
K @ half
0.309
0.310
0.116
0.114
Other research has found higher correlations between the sorption isotherm K and finer
particle sediments (Pant and Reddy, 2001;Pailles and Moody, 1992).
In theory,
sediment with higher amounts of clay or organic material have more sorption sites for P.
With more sorption sites, the buffering capacity of the sediment, K, should increase. In
Mill Creek, the similar sediment composition along the stream likely makes it difficult to
evaluate this effect.
Pore- Water
Figure 13a-b, Figure 14a-b and Figure 15 show three pore-water P profiles at each of the
five locations. A depth of zero is the sediment/water interface. Positive depths are in
the stream water and negative values represent sediment depth. The typical range in P
concentrations was between 0.05 to 5.5 mg P/L.
There are variations in the P
concentrations with depth, which is similar to Lewandowski et al. (2003) who found P
profiles could vary within short distances.
35
10
Stadt Road
5
Depth (cm)
0
-5
-10
-15
-20
-25
0
1
2
3
4
P concentration (mg/L)
5
6
10
Hwy K
5
Depth (cm)
0
-5
-10
-15
-20
-25
0.0
0.5
1.0
1.5
P concentration (mg/L)
Figure 13a-b. Pore water profiles for Stadt Road and Hwy K; 0 cm is the sediment/water interface.
36
2.0
10
Swedish Road
5
Depth (cm)
0
-5
-10
-15
-20
-25
0
1
2
3
4
P concentration (mg/L)
10
Elm Road
5
Depth (cm)
0
-5
-10
-15
-20
-25
0
1
2
3
4
5
P concentration (mg/L)
Figure 14a-b. Pore water profiles for Swedish Road and Elm Road; 0 cm is the sediment/water interface.
37
10
Hwy PP
5
Depth (cm)
0
-5
-10
-15
-20
-25
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
P concentration (mg/L)
Figure 15. 3 PW profiles at Hwy PP; 0 cm is the sediment/water interface.
Stadt, Swedish and Elm Roads had higher pore-water P concentrations in the sediment
than in the stream water, whereas Hwy K and Hwy PP did not. If the pore-water P
concentration is higher than the stream RP concentration, there could be diffusion of P
from the PW to the stream. If the stream RP concentrations are higher than pore-water
P concentrations, the P could diffuse into the pore-water. In some cases, the porewater equilibrators show pore-water P concentrations similar to stream P up to 10-20
cm into the sediment. These areas appear to be in equilibrium with the stream P
consistent with the results of the EPC/stream RP comparisons presented in Figure 11.
38
Equilibrators can be used to estimate the depth of the oxidized zone by examining the
concentrations of P, Mn and Fe. In Figure 16, an equilibrator at Stadt Road had a large
increase in the iron and manganese concentrations at 9 cm, suggesting anoxic
conditions do not occur until a depth of about 9 cm. In Figure 17, Elm Road had an
increase in P, Mn and Fe, close to the sediment surface which suggests low oxygen
concentrations close to the sediment surface. The locations sampled at Elm Road had
significantly thinner oxidized zones (3 cm) compared to Hwy PP (18 cm), whereas the
other locations did not have significant differences in the depths (10 cm) (H(4)=11.219,
P=0.024; Dunn’s: P<0.05). All pore-water profiles are listed in Appendix B.
The thickness of the oxygenated sediment boundary layer can affect the rate of P
diffusion from the anoxic sediment layer to the stream water. With a thin oxygenated
sediment boundary, such as the one found at Elm Road, there is a thin barrier to P
diffusing from anoxic sediment. The locations that have a thicker boundary layer, such
as at Hwy PP, could prevent the higher P concentrations from diffusing from the anoxic
sediment zone to the stream. The thicker boundary layer also suggests a similar
sorption interaction is occurring deeper in the sediments as at the surface
39
10
5
Depth (cm)
0
P
-5
Mn
-10
Fe
-15
-20
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Concentration (mg/L)
Figure 16. Pore-water profile of P, Fe and Mn for an equilibrator at Stadt with concentrations increasing
around 9cm suggesting an oxidized zone 9 cm thick; 0 is the sediment water interface, whereas
negative depths are in the sediment and positive depths are in the stream water.
5
Depth (cm)
0
P
-5
Mn
Fe
-10
-15
0.0
0.1
1.0
Concentration (mg/L)
10.0
100.0
Figure 17. Pore-water profile at Elm of P, Fe and Mn with increased concentrations near the sediment
interface suggesting a very thin oxidized zone; 0 is the sediment water interface, whereas
negative depths are in the sediment and positive depths are in the stream water.
40
More sampling conducted throughout the summer months would aid in an assessment
of the oxygenated sediment layer during lower oxygen periods. At the time of sampling,
the stream oxygen concentrations were relatively high, as shown in Figure 18. All
locations except Stadt Road had oxygen concentrations over 7 mg/L. Stadt Road had a
wide diurnal range in oxygen concentrations. This may be due to the higher quantity of
plant life in the stream compared to the other locations. Even Elm Road, which had a
very thin oxygenated sediment layer, had stream oxygen concentrations greater than 7
mg/L. The low oxygen in the sediment at Elm Road could be due to microbial influence.
While the stream oxygen concentrations were quite high during the sampling period,
Figure 19 shows the stream does experience periods of lower oxygen concentrations.
Pore-water equilibrators have received little attention but may provide a different tool
to determine movement of P. The sorption isotherms indicated phosphorus moving
onto the sediment when comparing the median EPC to the median RP (Figure 10).
When the top 3 cm of sediment pore-water P concentrations in the equilibrators are
compared to the stream P concentration, two equilibrators at Stadt Road, two
equilibrators at Swedish Road and all the equilibrators at Elm Road could have porewater P diffusing to the stream. These differences suggest the isotherms and porewater equilibrators are not measuring the same aspect of P diffusion.
41
14
Stadt (4 km)
DO Concentration (mg/L)
12
10
K (18 km)
8
Swedish (29
km)
6
Elm( 47 km)
4
PP (57 km)
2
0
12:00
0:00
12:00
0:00
12:00
0:00
12:00
Figure 18. DO (mg/L) over 3 day 24-hour periods at all locations during sampling periods in fall 2010 in
Mill Creek taken with a MS-5 sonde.
20
mg/L DO
18
16
Stadt
14
Elm
12
Hwy PP
10
8
6
4
2
0
Apr-10
May-10
Jun-10
Jul-10
Aug-10
Sep-10
Oct-10
Figure 19. DO (mg/L) measurements determined with a MS-5 sonde during summer 2010; measurements
taken on a biweekly basis at 3 locations along Mill Creek from 6am to 6pm.
42
Sediment P release model
The sediment P release model constructed for Mill Creek used both measured values
and estimated values for inputs. Table 5 shows the source of inputs for the model. The
laboratory sorption experiments and non-linear isotherms were used to estimate K. The
median KEPC/2, the desorbing portion of the isotherm, was used for K and varied with
distance downstream.
The oxic zone depth was estimated with pore-water
equilibrators, and the dimensions of the stream were determined during discharge
measurements.
Table 5. Summary of variables and sources of model inputs for sediment release model for Mill Creek.
Variable
Discharge, Width, Depth
Beginning river P concentrations
Concentration of runoff
3
(0.28 mg P/m )
k: Mass transfer coefficient
(0.016 m/day)
K: Relationship between solution
concentration and amount of P
3
desorbed (m /kg)
Bulk density and porosity
3
(1.5 kg/m , 0.43 respectively)
Sediment Depth (m)
Source
Field measurements
Estimate based on Oldenburg, 2005
Estimate based on Reddy et al. (1999)
Table 2 Median value per location using KEPC/2 to
represent desorbing sediment
Estimate
Active layer of 3 cm and oxygenated sediment
layer of 10 cm determined from PWE
The ability of the model to simulate mass traveling downstream is shown in Figure 20.
The model does exhibit some numerical dispersion. That is expected based on the large
spatial step size. With too few segments or too large of time-steps, a model can have
43
numerical dispersion. Some numerical dispersion creates a more realistic simulation
because there is physical dispersion in the natural world (Chapra, 1997). In this model,
there is about a 20-day lag time from the pulse input to the simulated pulse (Figure 20).
Added segments would reduce the simulated lag, but the dispersion is within reason to
represent this natural system.
The sensitivity to the mass transfer coefficient for this model is shown in Figure 21. This
comparison reduced inputs of P to half and had a beginning stream P concentration of
0.32 mg P/L (320 mg/m3) at 35 km downstream. Four values from 0 to 1 m/day were
examined.
A k value of zero does not include the sediment release, so the P
concentration quickly decreases and reaches the stream P concentration of 0.16 mg P/L
(160 mg/m3) . Higher values initially have a large P release and continue to release P for
about 225 days. A lower value of 0.01 m/day does not give as much P off initially and
takes closer to 400 days to reach equilibrium. Reddy et al. (1999) estimates the mass
transfer to be between 0.01 and 0.1 m/day. An intermediate response was randomly
chosen for this model and a value of 0.016 was used.
The sensitivity to K and depth is shown in Figure 22. Two K values (0.04 and 0.50 m3/kg)
at 2 depths (0.03 and 0.1 m) were simulated to compare the concentration at 35 km
downstream. The median K values determined with the isotherms ranged from 0.040 to
0.345 m3/kg (Table 2).
44
Three cm of sediment represents the active layer, whereas ten cm of sediment is the
typical oxidized sediment layer in Mill Creek. With a K of 0.04 m3/kg and depth of 0.03
m of sediment, there is little affect on the stream P concentration. By increasing the K
to 0.50 m3/kg, the sediment affects the stream P concentrations for about 300 days. By
including more sediment, 0.10 m, there is a longer time-period that the stream is
affected by the sediment. With a higher K of 0.50 m3/kg and a depth of 0.10 m of
sediment, the stream P is affected for more than 2 years.
Stream P Concentration (mg/m3)
1600
Concentrated pulse
1400
Simulated pulse
1200
1000
800
600
400
20
30
Days
40
50
60
Figure 20. Simulated pulse of P in the model evaluated at 35 km downstream and compared to the
simulated output. The difference reflects numerical dispersion.
45
350
Stream P concentration (mg/m3)
Evaluated at 35 km downstream
300
k=0
k = 0.1
k=1
k=0.01
250
200
150
0
50
100
150
200
250
300
350
400
Days
Figure 21. Evaluation of k values (0,0.01, 0.10 and 1 m/day) at 35 km downstream with loading reduced
3
to half and a beginning stream P concentration of about 320 mg P/m .
Stream P (mg/m3)
300
Evaluated at 35 km downstream
K=0.04 m3/kg; D=0.03m
K=0.04 m3/kg; D=0.10m
K=0.50 m3/kg; D=0.03m
K=0.50 m3/kg; D=0.10m
250
200
150
0
100
200
300
400
500
600
700
Days
3
Figure 22. Evaluation of K and depth of sediment at 35 km downstream using a lower K (0.04 m /kg) and
3
higher K (0.50 m /kg) at depths of 0.03 and 0.10 meters of sediment.
46
Three scenarios were examined with the simulation model. The first assumed no
change to historical point and non-point loading. The second reduced the loading to
half and examined how the sediment could influence stream P. The third reduced the
loading to half and did not include the sediment P.
These three scenarios used
sediment depths of 0.03 and 0.10 m. At the start of the simulation, pore-water and
stream water P concentrations were assumed to be in equilibrium.
The simulation results in Figure 23 show how the stream P would respond two months
after P inputs were decreased to half along the 70 km stream. Using historic loading the
stream P concentration is about 0.6 mg P/L (600 mg P/m3) at the start and decreases to
a stream P concentration of about 0.29 mg P/L (290 mg P/m3) at the mouth of the river.
After reducing the P inputs to half, without including the sediment P release, the stream
P concentration is 0.3 mg P/L (300 mg P/m3) at the headwaters and 0.15 mg P/L (150 mg
P/m3) at the mouth. The sediment release of P from 0.03 m of sediment, after a
reduction of P inputs, did not affect the stream P concentration for about 40 km. After
40 km, the stream P increased about 0.05 mg P/L (50 mg P/m3) due to the sediment
release of P. Incorporating 0.10 m of sediment increased stream P concentrations for
the entire stream, with the largest increase of about 0.08 mg P/L (80 mg P/m3) in the
last few segments, where the K was larger.
The simulation results in Figure 24 show the length of time the sediment affects the
stream P concentration at the mouth of the river. At 70 km downstream, if 0.03 m of
47
sediment are simulated, the sediment affects the stream P concentration for about a
year. When 0.10 m of sediment are incorporated, the sediment release of P affects the
stream for a little over 2 years.
The model results show a lag of several years may result if external loading is reduced
by half. With an increase in sediment depth or K there would be a longer recovery time
of the stream. Areas off the main channel flow may also affect the recovery time of the
stream. There might be higher amounts of P available to desorb from the sediment and
the release could be slower thereby slowing the recovery time of the stream.
While the simulation for this study did not include variables such as seasonality or
oxygen levels, it is known that oxygen levels can affect sediment P release. In the Mill
Creek watershed, the temperatures vary throughout the year, causing oxygen levels to
change due to plant growth. This simulation represented oxygenated sediment at
depths up to 0.10 m that are in equilibrium with the stream. Data was collected during
the fall of the year when oxygen levels were relatively high. While it was not simulated,
the stream does experience times of less oxygen where there might be an additional
release of P from anoxic portions of the sediment. Anoxic conditions also have the
potential to increase the P reservoir because there would be a thinner oxygenated
boundary and P from deeper sediments could diffuse to the stream.
48
600
Initial conditions
Reduced load and 0.10 m sediment
Reduced load and 0.03 m sediment
No sediment
Stream P (mg P/m3)
500
400
300
200
100
0
10
20
30
40
50
60
70
Distance Downstream (km)
Figure 23. Simulated stream P concentrations with distance downstream two months after external P
loading reduced to half of the original.
Concentration in Stream (mg P/m3)
450
Evaluated at 70 km downstream
Initial conditions
Reduced load and 0.03 m sediment
Reduced load and 0.10 m sediment
Reduced load and no sediment interaction
400
350
300
250
200
150
100
0
100
200
300
Days
400
500
600
Figure 24. Simulated sediment P release over 2-year period at 70 km downstream; Load was reduced to
half and sediment interaction was considered for sediment depths of 0.03 and 0.10 m.
49
This model could provide a more detailed representation of the stream P concentration
and sediment P release when combined with a watershed model. For example, SWAT
(Soil and Water Assessment Tool) is a watershed wide model that charts the movement
of water, sediment and P from the land to the stream. A SWAT model built for the Mill
Creek watershed attempts to match measured stream concentrations to simulated
results (Timm and McGinley, 2010).
By including a sediment sorption/desorption
aspect, based on the research in this thesis, simulated periods which do not match
measured data may be more accurately simulated.
50
SUMMARY
Sorption isotherms and desorption extractions of P in Mill Creek sediments were used to
determine the sediment buffering of P. A non-linear isotherm was created that was a
reasonable fit with the Freundlich isotherm model.
The isotherm was used to
determine the EPC and separate K values at specific stream P concentrations of interest.
There was a positive correlation between EPC and stream P concentrations. The ability
of the sediment to buffer P was significantly higher at KEPC/2 using the Freundlich
isotherm model compared to the linear isotherm. These results demonstrate the
importance of using a non-linear sorption isotherm compared to a linear sorption
isotherm.
Sediment P release can vary within short distances in Mill Creek and with stream RP
concentrations. Stream sections that have similar stream P concentrations can have
sediment sorbing and desorbing P. Within these short sections of stream, there may be
different settling patterns, plant activity, organic matter content or sediment properties
that affect the sorption and desorption of sediment P.
Although the EPC varies along the stream, the sediment composition and buffering
capacity at a specific concentration is similar. This implies that sediment exposed to the
same P concentrations will have similar changes in sorption or desorption. Because the
stream sediment composition and P buffering are similar, a possible explanation for the
51
different EPC and KEPC is the stream P concentration. Along Mill Creek, the stream P
concentration decreased with distance downstream. The sediment exposed to higher P
concentrations had lower KEPC and higher EPC values, whereas sediments exposed to
lower stream P concentrations had lower EPC values and higher KEPC values.
While the
sorption characteristics appear to differ along the stream, when they are viewed as part
of a non-linear, concentration-dependent relationship, they are similar along the stream
Pore-water equilibrators were used to determine the depth of oxic sediment and the
size of the P reservoir. The depth of the oxic sediment was typically 10 cm. Beneath the
oxygenated sediment layer, the anoxic sediment typically had higher P concentrations
than in the oxic sediment. The increasing P concentrations suggest a potentially large
reservoir of P available to release to the stream. While the oxic sediment layer may
provide a barrier to P in the anoxic sediment layer, if the oxic sediment layer becomes
reduced, the reservoir of sediment P available to diffuse to the stream could increase.
A two-box numerical model was developed to relate sediment P with the stream P
concentration. Many measured inputs were utilized, but the model also required
assumptions about the rate of exchange that could not be validated. The primary focus
of the model was to determine how long sediment release of P would affect stream P
concentrations if P inputs were reduced. The simulations show the sediment would
affect stream P concentrations after a reduction in P inputs for less than one year if 3 cm
of sediment were considered. If 10 cm of sediment are considered, the sediment
52
affected the stream P concentration for several years. The model assumed main
channel flow. If there was more transient flow, the recovery could take longer.
This relatively simple model can be combined with a watershed wide model in order to
create a more complex simulation tool that represents runoff events and sediment
release. This would allow for variable P inputs, based on precipitation events, to affect
the stream P concentration, which would affect the sediment release of P.
53
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57
APPENDIX A – STREAM AND SEDIMENT CHARACTERIZATION
The stream P concentration in 2010 are similar to the stream P concentrations in 2002
(Figure 25). This suggest that the sediment have been exposed to these typicalstream P
concentrations for more than 10 years. In 2002, the average TP at Stadt Road was 0.57
mg/L and the concentration decrease to an average of 0.14 mg P/L at Hwy PP.
1.0
TP Range
Average RP
Average TP
Concentration (mg/L)
0.8
0.6
0.4
0.2
0.0
Stadt
K
Swedish
Elm
Hwy PP
Figure 25. TP and RP during 2001-2002 based on 22, 4, 4, 28 and 6 data points for Stadt, K, Swedish, Elm
and Hwy PP, respectively; Measurements taken between 6am and 6pm.
In Table 6, the ranges of pH and temperature from the sonde in the river over the 3-day
period are listed along with pH and temperatures recorded in the lab. The pH and
temperature in the lab were taken at the beginning and end of the sorption isotherm
58
experiment (24-hour period) and averaged over 36 samples. All lab pH and temperature
values were within an acceptable range of the stream monitoring values.
Table 6. Recorded temperature and pH over 3-daysampling period and during isotherm experiment.
Location
Stadt
K
Swedish
Elm
PP
pH range
Low
7.15
7.4
7.39
7.11
6.83
pH in lab
High
7.8
7.73
7.76
7.45
6.91
7.50
7.58
7.64
7.29
7.13
59
Temp low
Low
19.24
3.91
13.20
13.79
8.59
Temp in lab
High
22.86
8.14
17.93
17.27
11.99
20
20
20
20
20
APPENDIX B – DATA
Data for sorption isotherms and desorption extractions
Sorption Isotherms
Desorption Extractions
Sample
location
Solution conc
(mg/L)
Change in P (mg
P/kg sediment)
Solution conc
(mg P/L)
Cumulative P removed
(mg P/kg sediment)
SX1-1
0.190
0.344
0.326
0.461
0.622
0.798
-4.37
-6.05
-1.87
0.81
3.20
4.53
0.059
0.036
0.040
0.036
0.036
0.083
0.053
0.026
-2.91
-4.70
-6.70
-8.49
-10.27
-14.41
-17.03
-18.30
SX1-2
0.165
-4.13
0.070
-2.41
0.183
0.318
0.461
0.615
0.776
-2.23
-1.50
0.76
2.84
4.80
0.036
0.071
0.056
0.031
0.043
0.039
0.039
-3.62
-6.00
-7.97
-9.00
-10.48
-11.79
-13.10
0.080
0.124
0.139
0.307
0.417
0.585
-1.87
-0.94
2.19
4.75
7.37
8.56
0.083
0.073
0.039
0.040
0.036
0.083
0.046
0.026
-12.92
-23.56
-29.40
-34.88
-40.11
-52.22
-59.06
-62.72
SX1-3
Highlighted data points were removed from analysis
60
Change in P (mg P/kg sediment)
10
Sx1-1
5
0
-5
-10
-15
-20
-25
-30
Change in P (mg P/kg sediment)
10
Sx1-2
5
0
-5
-10
-15
-20
Change in P (mg P/kg sediment)
-25
40
Sx1-3
20
0
-20
-40
-60
-80
0.0
0.2
0.4
0.6
Solution Concentration (mg P/L)
Sorption Isotherms
Freundlich Isotherm
Linear (Sorption Isotherms)
0.8
Desorption Extractions
Removed Points
61
1.0
Sorption Isotherms
Desorption Extractions
Sample
location
Solution conc
(mg/L)
Change in P (mg
P/kg sediment)
Solution conc
(mg P/L)
Cumulative P removed
(mg P/kg sediment)
SX2-1
0.168
0.146
0.271
0.333
0.556
0.721
-4.01
-2.20
-0.64
3.71
4.50
6.50
0.044
0.030
0.047
0.034
0.040
0.003
0.070
0.049
-1.75
-2.91
-4.81
-6.21
-7.84
-7.92
-10.77
-12.83
SX2-2
0.183
0.220
0.285
0.413
0.534
0.633
-4.76
-3.38
-0.87
2.06
5.52
9.19
0.121
0.061
0.143
0.044
0.064
0.037
0.033
0.070
-3.58
-5.38
-9.60
-10.93
-12.85
-14.00
-14.98
-17.10
SX2-3
0.128
0.154
0.234
0.373
0.542
0.666
-2.92
-1.69
0.25
2.98
5.15
6.90
0.067
0.044
0.059
0.039
0.036
0.024
0.026
0.037
-2.30
-3.78
-5.81
-7.23
-8.52
-9.36
-10.24
-11.54
62
10
Sx2-1
Change in P (mg P/kg
sediment)
5
0
-5
-10
-15
-20
Change in P (mg P/kg sediment)
20
Sx2-2
10
0
-10
-20
-30
-40
Change in P (mg P/kg sediment)
10
Sx2-3
5
0
-5
-10
-15
-20
-25
0.0
0.2
0.4
0.6
Solution Concentration (mg P/L)
0.8
Sorption Isotherms
Desorption Extractions
Freundlich Isotherm
Linear (Sorption Isotherms)
63
1.0
Sorption Isotherms
Desorption Extractions
Sample
location
Solution
conc (mg/L)
Change in P (mg
P/kg sediment)
Solution
conc (mg/L)
Cumulative P removed
(mg P/kg sediment)
KX1-1
0.089
0.115
0.160
0.297
0.449
0.553
-2.09
0.31
2.20
4.48
6.38
8.56
0.078
0.022
0.011
0.041
0.067
0.019
0.004
0.000
-1.58
-2.04
-2.27
-3.14
-4.52
-4.90
-4.98
-4.98
KX1-2
0.078
0.122
0.182
0.312
0.549
0.683
-1.41
0.11
1.34
4.16
4.33
6.62
0.097
0.059
0.045
0.059
0.003
0.030
0.030
0.033
-2.16
-3.47
-4.45
-5.76
-5.83
-6.48
-7.17
-7.89
KX1-3
0.074
0.089
0.111
0.186
0.312
0.449
-1.40
0.85
3.03
6.57
8.40
9.99
0.063
0.037
0.019
0.056
0.037
0.030
0.022
0.004
-1.35
-2.14
-2.51
-3.66
-4.43
-5.04
-5.51
-5.59
Highlighted data points were removed from analysis
64
Change in P (mg P/kg sediment)
10
Kx1-1
5
0
-5
-10
10
Change in P (mg P/kg
sediment)
Kx1-2
5
0
-5
-10
Change in P (mg P/kg sediment)
-15
15
Kx1-3
10
5
0
-5
-10
-15
-20
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Solution Concentration (mg P/L)
Sorption Isotherms
Freundlich Isotherm
Linear (Sorption Isotherms)
65
0.7
Desorption Extractions
Removed points
0.8
0.9
Sorption Isotherms
Desorption Extractions
Sample
location
Solution
conc (mg/L)
Change in P (mg
P/kg sediment)
Solution
conc (mg/L)
Cumulative P removed
(mg P/kg sediment)
KX2-1
0.111
0.148
0.215
0.371
0.516
0.705
-2.03
-0.43
0.67
2.56
4.47
6.32
0.067
0.037
0.026
0.045
0.022
0.033
0.022
0.007
-1.48
-2.28
-2.86
-3.82
-4.31
-5.02
-5.49
-5.66
KX2-2
0.082
0.189
0.208
0.393
0.531
0.772
-1.50
-1.26
0.81
2.44
4.24
4.42
0.056
0.030
0.026
0.033
0.022
0.033
0.030
0.007
-1.23
-1.85
-2.42
-3.13
-3.61
-4.34
-4.98
-5.14
KX2-3
0.060
0.045
0.085
0.111
0.167
0.226
-1.07
1.86
3.54
9.31
12.38
16.54
0.033
0.033
0.026
0.022
0.052
0.033
0.022
0.007
-0.65
-1.35
-1.87
-2.32
-3.38
-4.06
-4.50
-4.65
66
Change in P (mg P/kg
sediment)
10
Kx2-1
5
0
-5
-10
-15
Change in P (mg P/kg sediment)
10
Kx2-2
5
0
-5
-10
-15
Change in P (mg P/kg sediment)
25
Kx2-3
20
15
10
5
0
-5
-10
0.0
0.2
0.4
0.6
Solution Concentration (mg P/L)
Sorption Isotherms
Desorption Extractions
Freundlich Isotherm
Linear (Sorption Isotherms)
67
0.8
Sorption Isotherms
Desorption Extractions
Sample
location
Solution conc
(mg/L)
Change in P (mg
P/kg sediment)
Solution conc
(mg/L)
Cumulative P removed
(mg P /kg sediment)
SwX1-1
0.077
0.121
0.263
0.242
0.419
0.872
-1.75
-0.84
-0.41
5.53
7.32
2.72
0.053
0.056
0.040
0.028
0.045
0.034
0.039
-1.43
-2.89
-3.97
-4.74
-5.95
-6.88
-7.94
SwX1-2
0.046
0.082
0.160
0.292
0.471
0.754
-0.83
0.03
1.96
3.95
5.81
5.50
0.064
0.033
0.025
0.011
0.030
0.025
0.019
-2.08
-3.10
-3.83
-4.17
-5.08
-5.85
-6.43
SwX1-3
0.041
0.072
0.111
0.257
0.483
0.655
-0.93
0.25
2.90
4.60
5.65
9.15
0.035
0.023
0.019
0.012
0.033
0.028
0.012
-1.13
-1.86
-2.48
-2.86
-3.97
-4.87
-5.27
68
Change in P (mg P/kg sediment)
10
SWx1-1
5
0
-5
-10
-15
-20
10
Change in P (mg P/kg
sediment)
SWx1-2
5
0
-5
-10
Change in P (mg P/kg sediment)
-15
15
SWx1-3
10
5
0
-5
-10
-15
0.0
0.2
0.4
0.6
Solution Concentration (mg P/L)
Sorption Isotherms
Freundlich Isotherm
0.8
Desorption Extractions
Linear (Sorption Isotherms)
69
1.0
Sorption Isotherms
Desorption Extractions
Sample
location
Solution conc
(mg/L)
Change in P (mg
P/kg sediment)
Solution conc
(mg/L)
Cumulative P removed
(mg P /kg sediment)
SwX2-1
0.039
0.069
0.113
0.220
0.363
0.621
-0.65
0.32
2.47
5.48
8.36
8.26
0.059
0.026
0.017
0.003
0.019
0.019
0.003
-2.36
-3.32
-3.97
-4.09
-4.79
-5.55
-5.67
SwX2-2
0.039
0.082
0.143
0.305
0.527
0.739
-0.78
0.02
2.39
3.32
4.76
4.98
0.046
0.017
0.002
0.002
0.028
0.012
0.012
-1.32
-1.80
-1.85
-1.89
-2.70
-3.07
-3.42
SwX2-3
0.105
0.049
0.069
0.143
0.315
0.479
-2.22
0.73
3.96
8.88
10.42
12.23
0.067
0.017
0.011
0.009
0.025
0.008
0.019
-2.12
-2.65
-3.00
-3.29
-4.08
-4.33
-4.94
Highlighted data points were removed from analysis
70
Change in P (mg P/kg
sediment)
15
SWx2-1
10
5
0
-5
-10
-15
Change in P (mg P/kg
sediment)
8
SWx2-2
6
4
2
0
-2
-4
-6
Change in P (mg P/kg sediment)
20
SWx2-3
15
10
5
0
-5
-10
-15
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Solution Concentration (mg P/L)
Sorption Isotherms
Desorption Extractions
Freundlich Isotherm
Removed points
Linear (Sorption Isotherms)
71
0.8
Sorption Isotherms
Desorption Extractions
Sample
location
Solution
conc (mg/L)
Change in P (mg
P/kg sediment)
Solution conc
(mg P/L)
Cumulative P removed (mg
P/kg sediment)
EX1-1
0.082
0.111
0.089
0.078
0.089
0.147
-1.84
-0.65
4.35
11.83
14.12
19.03
0.015
0.028
0.046
0.023
0.917
0.148
0.045
0.029
-0.77
-2.13
-4.48
-5.61
-51.28
-58.67
-60.97
-62.45
EX1-2
0.056
0.053
0.089
0.089
0.111
0.144
-1.28
0.79
3.12
9.98
13.54
18.82
0.084
0.332
0.075
0.021
0.154
0.023
0.017
0.017
-2.87
-13.96
-16.60
-17.35
-22.59
-23.39
-23.95
-24.51
EX1-3
0.046
0.053
0.049
0.060
0.078
0.067
-1.11
0.68
4.69
11.00
14.59
23.39
0.052
0.062
0.131
0.060
0.074
0.011
0.038
0.011
-7.08
-15.30
-32.72
-41.15
-51.26
-52.85
-57.97
-59.43
Highlighted data points were removed from analysis
72
Change in P (mg P/kg sediment)
40
Ex1-1
20
0
-20
-40
-60
Change in P (mg P/kg sediment)
-80
80
Ex1-2
60
40
20
0
-20
-40
-60
Change in P (mg P/kg sediment)
0.0
0.2
0.4
0.6
Solution Concentration (mg P/L)
0.8
1.0
200
Ex1-3
150
100
50
0
-50
-100
0.0
0.1
0.2
Solution Concentration (mg P/L)
Sorption Isotherms
Freundlich Isotherm
Linear (Sorption Isotherms)
73
0.3
Desorption Extractions
Removed points
0.4
Sorption Isotherms
Desorption Extractions
Sample
location
Solution
conc (mg/L)
Change in P (mg
P/kg sediment)
Solution conc
(mg P/L)
Cumulative P removed (mg
P/kg sediment)
EX2-1
0.071
0.111
0.158
0.599
0.476
0.664
-1.60
-0.54
1.61
-1.93
6.64
7.26
0.031
0.031
0.018
0.031
0.066
0.023
0.018
0.017
-1.23
-2.56
-3.34
-4.70
-7.38
-8.29
-9.00
-9.67
EX2-2
0.074
0.111
0.166
0.308
0.468
0.659
-1.75
-0.50
1.80
4.23
5.86
7.58
0.104
0.057
0.047
0.018
0.018
0.016
0.038
0.011
-3.25
-4.98
-6.40
-6.97
-7.51
-7.97
-9.13
-9.46
EX2-3
0.032
0.060
0.096
0.223
0.384
0.631
-0.69
0.49
3.49
5.22
7.19
8.13
0.035
0.015
0.014
0.008
0.011
0.054
0.013
0.029
-1.25
-1.78
-2.29
-2.60
-2.99
-4.89
-5.34
-6.33
74
Change in P (mg P/kg
sediment)
10
Ex2-1
5
0
-5
-10
-15
-20
Change in P (mg P/kg
sediment)
10
Ex2-2
5
0
-5
-10
-15
Change in P (mg P/kg sediment)
-20
15
Ex2-3
10
5
0
-5
-10
-15
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Solution Concentration (mg P/L)
Sorption Isotherms
Freundlich Isotherm
0.7
Desorption Extractions
Linear (Sorption Isotherms)
75
0.8
Sorption Isotherms
Sample
location
Desorption Extractions
Solution conc
(mg/L)
Change in P (mg P/kg
sediment)
Solution conc
(mg P/L)
Cumulative P removed
(mg P/kg sediment)
PPX1-1
0.271
0.067
0.056
0.393
0.471
0.412
-6.00
0.36
4.02
2.30
5.87
12.16
0.040
0.001
0.006
0.000
0.011
0.036
0.007
0.007
-1.07
-1.11
-1.26
-1.26
-1.56
-2.54
-2.72
-2.92
PPX1-2
0.119
0.056
0.182
0.141
0.178
0.415
-3.05
0.61
1.48
8.48
10.31
13.86
0.018
0.001
0.003
0.000
0.019
0.065
0.029
0.018
-0.34
-0.37
-0.43
-0.43
-0.78
-2.03
-2.62
-2.99
PPX1-3
0.052
0.048
0.056
0.089
0.115
0.145
-1.35
0.78
4.91
8.35
13.63
17.91
0.087
0.021
0.015
0.022
0.019
0.025
0.014
0.018
-1.69
-2.09
-2.38
-2.82
-3.19
-3.71
-3.99
-4.37
Highlighted data points were removed from analysis
76
Change in P (mg P/kg sediment)
15
PPx1-1
10
5
0
-5
-10
Change in P (mg P/kg sediment)
20
PPx1-2
15
10
5
0
-5
-10
Change in P (mg P/kg sediment)
-15
30
PPx1-3
20
10
0
-10
-20
-30
0.0
0.1
0.2
0.3
0.4
Solution Concentration (mg P/L)
Sorption Isotherms
Desorption Extractions
Freundlich Isotherm
Removed points
Linear (Sorption Isotherms)
77
0.5
Sorption Isotherms
Sample
location
Desorption Extractions
Solution conc
(mg/L)
Change in P (mg P/kg
sediment)
Solution conc
(mg P/L)
Cumulative P removed
(mg P/kg sediment)
PPX2-1
0.037
0.074
0.059
0.085
0.074
0.093
-0.82
0.20
4.19
9.31
15.36
21.93
0.028
0.004
0.010
0.011
0.067
0.025
0.025
0.022
-0.55
-0.65
-0.85
-1.07
-2.43
-2.99
-3.51
-3.97
PPX2-2
0.052
0.033
0.026
0.067
0.059
0.115
-1.06
1.15
4.19
9.05
14.21
21.64
0.064
0.030
0.000
0.011
0.037
0.062
0.018
0.018
-1.38
-1.99
-1.99
-2.22
-3.01
-4.29
-4.66
-5.03
PPX2-3
0.059
0.067
0.119
0.067
0.052
0.048
-1.29
0.34
3.08
9.02
15.64
19.99
0.009
0.003
0.010
0.026
0.030
0.040
0.014
0.007
-0.18
-0.24
-0.45
-1.00
-1.62
-2.51
-2.81
-2.97
Highlighted data points were removed from analysis
78
Change in P (mg P/kg
sediment)
40
PPx2-1
30
20
10
0
-10
-20
-30
Change in P (mg P/kg
sediment)
40
PPx2-2
30
20
10
0
-10
-20
Change in P (mg P/kg sediment)
-30
25
PPx2-3
20
15
10
5
0
-5
-10
0.0
0.1
Solution Concentration (mg P/L)
Sorption Isotherms
Freundlich Isotherm
Linear (Sorption Isotherms)
79
Desorption Extractions
Removed points
0.2
PWE – Fe, P, Mn relationship in PWE
Depth
11.2
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
Depth
11.2
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
P
0.68
0.64
0.62
0.66
0.51
0.41
0.41
0.79
2.11
1.95
P
0.27
0.20
0.23
0.21
0.12
0.11
0.12
0.09
0.09
0.06
0.06
0.10
A (Sx1-1)
Fe
0.27
0.27
0.19
0.17
0.11
0.10
0.10
0.32
2.69
1.85
Mn
0.02
0.03
0.03
0.04
0.11
0.41
0.31
0.62
1.26
1.15
R (Kx1-2)
Fe
Mn
0.30
0.07
0.19
0.10
0.02
0.02
0.02
0.01
0.02
0.01
0.07
0.42
0.07
0.04
0.05
0.05
0.01
0.02
0.02
0.03
0.18
0.38
1.09
1.52
Stadt Road
B (Sx1-2)
P
Fe
Mn
0.36
0.36
0.37
0.39
1.54
2.40
2.58
2.52
3.48
0.12
0.11
0.12
0.07
0.41
1.36
2.00
2.73
4.46
0.05
0.04
0.04
0.06
0.63
1.05
1.14
0.73
0.89
Hwy K
S (Kx1-3)
Fe
Mn
P
0.28
0.27
0.25
0.22
0.13
0.13
0.20
1.20
1.58
1.31
1.23
1.23
80
0.46
0.32
0.29
0.16
0.03
0.02
0.04
2.89
5.68
2.98
2.87
4.44
0.09
0.05
0.05
0.04
0.04
1.21
2.11
3.72
3.95
4.98
4.66
3.70
P
0.35
0.35
0.35
0.36
2.63
3.33
2.93
2.13
4.68
3.51
3.26
5.39
P
0.28
0.27
0.27
0.25
0.22
0.21
0.14
0.13
0.14
0.12
0.10
0.08
C (Sx1-3)
Fe
Mn
0.06
0.08
0.07
0.08
3.54
4.77
6.82
7.07
16.69
13.75
16.91
25.91
0.03
0.03
0.12
1.12
2.55
2.24
2.87
3.99
4.43
4.27
4.28
5.86
T (Kx2-2)
Fe
Mn
0.37
0.32
0.26
0.27
0.11
0.06
0.01
0.02
0.02
0.01
0.03
0.01
0.07
0.05
0.05
0.05
0.04
0.03
0.02
0.03
0.03
0.06
0.14
0.27
Depth
11.2
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
Depth
11.2
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
D (SWx2-1)
P
Fe
0.2203 0.214
0.22
0.12
0.22
0.10
0.20
0.11
0.19
0.04
0.17
0.06
0.31
0.46
0.52
1.14
0.99
5.59
2.39
17.37
2.40
17.35
2.36
16.95
P
0.12
0.13
0.62
1.89
2.20
3.37
2.91
3.05
2.63
3.43
H (Ex1-3)
Fe
Mn
0.26
0.32
13.51
6.53
21.30
23.86
33.07
33.98
37.05
35.73
36.58
26.39
0.13
0.26
4.26
4.54
6.02
7.56
6.18
5.31
6.04
5.92
6.07
5.83
Mn
0.147
0.09
0.09
0.09
0.09
0.82
1.49
1.70
2.15
1.05
1.06
1.04
Swedish Road
E (SWx2-2)
P
Fe
Mn
0.21
0.20
0.20
0.19
0.19
0.18
0.19
0.17
0.18
0.51
2.77
3.85
0.13
0.15
0.04
0.03
0.03
0.02
0.02
0.05
0.13
1.42
13.30
23.58
Elm Road
I (Ex2-3)
P
Fe
0.0909
0.1546
0.09
0.13
0.10
0.13
0.10
0.16
0.09
0.17
0.47
3.95
0.84
8.42
1.68
17.47
2.57
22.06
4.37
31.49
2.70
26.17
81
0.09
0.08
0.09
0.09
0.02
0.10
0.11
0.66
1.18
2.80
3.33
3.11
Mn
0.1216
0.12
0.12
0.12
0.17
1.91
1.83
1.96
1.86
2.35
2.39
G (SWx2-3)
P
Fe
Mn
0.20
0.20
0.22
2.14
2.86
2.59
2.93
2.84
2.46
2.89
2.79
2.86
P
0.11
0.43
3.86
4.08
3.81
3.48
3.71
3.40
2.69
4.00
0.08
0.06
0.13
4.84
5.85
5.32
6.24
6.60
6.44
9.11
9.66
9.84
0.09
0.06
0.16
3.34
2.75
2.66
2.78
2.92
3.13
3.32
3.26
3.50
J (Ex1-2)
Fe
Mn
0.15
3.18
20.71
25.19
29.92
31.27
33.97
33.35
30.80
37.81
0.13
2.91
3.82
3.16
3.95
4.47
4.41
3.99
3.94
3.63
Depth
11.2
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
P
0.10
0.06
0.06
0.06
0.06
0.08
0.06
0.04
0.06
0.07
0.39
0.20
K (PPx1-2)
Fe
Mn
0.99
0.55
0.51
0.50
0.35
0.30
0.16
0.10
0.23
1.69
14.75
0.00
0.12
0.04
0.04
0.05
0.11
1.50
2.08
2.45
4.16
5.81
9.24
12.11
Hwy PP
L (PPx1-3)
P
Fe
Mn
0.07
0.05
0.05
0.05
0.05
0.05
0.06
0.05
0.06
0.05
0.08
0.08
0.69
0.46
0.47
0.18
0.04
0.04
0.05
0.04
0.03
0.05
1.67
2.45
82
0.08
0.05
0.04
0.02
0.35
0.38
0.49
0.40
0.87
2.50
6.64
6.08
M (PPx1-1)
P
Fe
Mn
0.1537
1.9378
0.1543
0.07
0.83
0.05
0.07
0.69
0.05
0.07
0.59
0.05
0.07
0.50
0.05
0.08
0.29
0.01
0.09
0.14
0.02
0.07
0.08
0.04
0.08
0.07
0.03
0.08
0.05
0.28
0.10
0.05
0.56
0.22
0.06
2.15
Pore-water ion concentrations: 3 per location
Depth
Stadt Road
Cu
K
Mg
As
Ca
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
58.5
56.6
55.7
58.4
56.0
53.9
43.5
45.1
45.4
35.6
0.008
0.009
0.009
0.010
0.012
0.010
0.016
0.017
0.028
0.023
10.3
10.0
9.8
10.4
9.7
9.5
8.9
9.2
9.0
8.5
B1
B2
B3
8.7
6.2
3.7
<0.005
<0.005
<0.005
64.6
65.8
65.5
0.008
0.008
0.008
B4
1.2
<0.005
65.6
B5
B6
B7
B11
B12
-1
-3.5
-6.2
-8.7
-11.3
<0.005
<0.005
0.005
<0.005
<0.005
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
0.005
0.008
0.008
<0.005
<0.005
<0.005
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
Na
Pb
S
Zn
16.9
16.8
16.5
17.0
16.8
16.5
14.1
14.6
15.0
17.0
102.6
100.2
97.3
102.4
102.1
99.8
85.8
88.8
77.8
58.9
<0.002
<0.002
<0.002
0.002
0.002
0.003
0.003
0.002
<0.002
0.003
30.33
29.23
29.90
31.09
31.91
31.73
31.67
32.40
23.71
10.06
0.085
0.070
0.194
0.150
0.318
0.241
0.226
0.331
0.732
0.068
8.6
8.7
8.8
19.0
19.4
19.4
101.8
104.0
104.4
0.002
0.002
0.003
27.03
27.51
27.36
0.043
0.024
0.024
0.008
8.8
19.3
104.5
<0.002
27.11
0.024
57.9
51.8
52.5
32.3
37.1
0.007
0.008
0.009
0.008
0.015
9.4
9.6
9.6
7.1
7.8
16.8
15.0
15.2
8.6
9.9
84.3
59.8
56.6
37.9
41.5
0.002
0.002
0.003
0.004
0.015
17.58
5.48
3.18
4.38
13.04
0.021
0.025
0.024
0.016
0.064
67.2
66.4
65.1
62.0
38.7
36.1
49.5
64.3
67.6
65.0
73.7
72.5
0.008
0.011
0.012
0.012
0.020
0.022
0.012
0.016
0.014
0.011
0.011
0.013
9.0
8.9
8.9
9.2
7.2
7.5
9.3
12.5
11.9
11.9
13.7
12.8
19.9
19.6
19.2
17.9
10.5
9.8
12.6
16.1
16.1
15.1
16.6
15.4
107.8
106.3
105.6
102.9
52.0
35.6
36.9
41.0
36.7
34.5
37.2
35.4
<0.002
<0.002
0.003
0.002
0.002
<0.002
<0.002
0.003
0.004
0.005
0.004
0.006
28.13
27.75
27.35
26.36
11.51
3.68
2.25
2.02
1.72
1.81
1.61
1.52
0.019
0.021
0.022
0.022
0.008
0.011
0.012
0.024
0.009
0.015
0.014
0.015
83
Hwy K
K
Mg
Depth
As
Ca
Cu
Na
Pb
S
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
49.8
50.1
44.6
49.9
43.6
35.1
34.4
29.6
35.5
38.2
47.1
49.7
0.006
0.005
0.011
0.007
0.010
0.011
0.011
0.013
0.016
0.018
0.016
0.018
6.9
6.9
6.3
6.9
7.1
7.1
7.1
6.5
7.0
7.0
7.5
7.2
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
0.007
<0.005
<0.005
49.9
50.5
50.4
47.4
48.8
39.6
35.9
40.5
41.3
40.5
39.9
40.6
0.006
0.005
0.006
0.005
0.006
0.007
0.008
0.009
0.011
0.018
0.019
0.021
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
50.0
50.4
49.6
50.5
50.6
50.0
47.1
45.9
41.5
36.5
33.4
30.1
0.006
0.010
0.011
0.015
0.024
0.028
0.021
0.021
0.018
0.016
0.014
0.017
16.0
16.1
14.4
16.1
13.9
11.0
10.8
9.2
11.0
11.7
14.3
15.0
54
54
48
55
49
34
32
25
27
26
28
24
<0.002
<0.002
0.003
0.002
0.003
<0.002
<0.002
0.003
<0.002
0.002
0.003
0.002
21.3
21.2
19.2
21.1
18.4
15.5
14.0
9.9
10.3
12.7
17.4
15.1
0.006
0.003
0.024
0.006
0.004
<0.002
<0.002
<0.002
0.003
0.004
0.003
0.003
7.0
7.0
6.9
6.6
6.9
6.5
5.7
4.2
3.6
4.2
4.3
3.4
16.1
16.4
16.2
15.4
15.8
12.3
10.9
11.5
11.4
11.5
11.6
12.2
55
56
56
53
55
44
35
31
28
27
27
29
0.003
<0.002
0.003
<0.002
<0.002
0.003
<0.002
<0.002
0.003
<0.002
<0.002
0.002
21.7
21.8
21.8
20.5
20.7
13.8
9.6
6.8
4.4
2.9
3.4
6.6
0.006
0.002
0.003
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.003
<0.002
<0.002
7.0
7.4
6.9
7.1
7.0
7.8
8.3
9.3
8.7
8.0
7.7
6.7
16.4
16.4
16.2
16.5
16.6
16.2
15.3
14.8
13.2
11.5
10.5
9.4
56
57
56
57
57
56
53
46
38
32
27
21
<0.002
<0.002
<0.002
0.003
0.002
0.003
<0.002
<0.002
<0.002
0.002
0.002
<0.002
21.8
21.8
21.6
22.0
22.2
22.0
21.5
22.2
21.4
18.2
15.5
10.1
0.003
0.015
0.004
<0.002
0.002
0.018
0.002
0.003
<0.002
<0.002
<0.002
<0.002
84
Zn
Swedish Road
Cu
K
Mg
Depth
As
Ca
Na
Pb
S
Zn
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
11.2
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
46.2
45.8
45.9
44.4
45.2
39.3
38.0
30.2
29.0
26.5
26.8
26.8
0.006
0.009
0.007
0.007
0.005
0.010
0.009
0.009
0.009
0.008
0.006
0.006
7.3
7.4
7.4
7.2
7.3
7.8
8.3
6.6
5.4
5.3
5.5
5.5
14.7
14.5
14.6
14.1
14.3
12.2
11.7
9.1
9.5
9.8
9.9
9.7
53.1
52.3
53.2
51.5
52.0
24.4
14.9
13.3
14.9
15.6
15.7
15.4
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
17.76
18.11
17.96
17.44
17.39
5.52
2.30
1.59
1.27
1.56
1.87
1.44
0.011
0.017
0.011
0.012
0.006
0.010
0.008
0.009
0.015
0.007
0.005
0.005
E1
E2
E3
E4
E5
E6
E7
E8
E9
E10
E11
E12
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
<0.005
<0.005
<0.005
<0.005
<0.005
0.006
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
46.1
37.0
46.1
45.4
46.1
35.7
29.0
22.8
25.0
34.7
46.5
51.5
0.004
0.007
0.008
0.005
0.008
0.013
0.013
0.014
0.013
0.011
0.007
0.005
7.4
6.2
7.6
7.3
7.7
7.5
7.1
6.7
6.8
6.9
6.9
6.6
14.6
11.7
14.7
14.5
14.7
10.9
8.7
6.8
7.5
9.3
9.3
9.0
52.8
42.4
53.7
53.1
56.9
45.7
31.1
20.5
19.0
16.8
20.1
21.6
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
17.60
14.39
17.64
17.57
18.03
13.40
10.71
7.80
6.88
2.11
1.07
1.06
0.008
0.009
0.010
0.008
0.006
0.007
0.005
0.005
0.007
0.012
0.018
0.012
G1
G2
G3
G4
G5
G6
G7
G8
G9
G10
G11
G12
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
<0.005
<0.005
<0.005
0.005
0.007
<0.005
<0.005
<0.005
<0.005
0.005
<0.005
0.007
46.8
45.8
46.2
40.1
33.3
33.2
31.9
27.3
26.3
25.6
24.6
25.6
0.006
0.008
0.009
0.013
0.007
0.007
0.008
0.011
0.007
0.010
0.008
0.008
7.5
7.4
7.7
7.8
7.1
7.0
6.6
4.9
4.3
3.8
3.3
3.3
14.9
14.6
14.8
12.2
9.9
9.8
9.2
7.7
7.2
7.0
6.7
6.8
54.6
53.7
55.9
38.2
31.2
29.5
25.4
19.3
15.4
15.8
16.0
14.5
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.002
<0.002
<0.002
<0.002
<0.002
18.18
17.72
18.82
11.20
7.60
5.93
4.07
3.16
2.81
2.48
2.01
2.27
0.005
0.005
0.006
0.004
0.004
0.005
0.004
0.007
0.009
0.015
0.016
0.015
85
Depth
As
Ca
Elm Road
Cu
K
Mg
Na
Pb
S
Zn
H1
H2
H3
H4
H5
H6
H7
H8
H9
H10
H11
H12
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
<0.005
<0.005
<0.005
<0.005
<0.005
0.006
0.009
<0.005
<0.005
0.007
<0.005
0.009
30.8
31.9
36.3
38.8
48.5
56.3
63.6
66.4
74.0
71.8
69.0
74.0
0.007
0.007
0.018
0.016
0.012
0.013
0.022
0.016
0.020
0.011
0.008
0.003
8.8
8.3
7.8
8.0
9.0
10.2
11.3
11.8
12.4
12.1
11.9
12.1
10.7
11.0
11.3
11.3
12.3
14.4
15.7
16.2
17.6
17.0
16.4
17.2
34
36
36
32
28
30
36
40
44
43
42
45
<0.002
<0.002
<0.002
<0.002
0.003
0.003
0.006
0.007
0.008
0.006
0.007
0.004
13.8
13.7
7.2
7.0
2.8
2.2
2.1
2.1
2.0
1.8
1.6
1.4
0.006
0.003
0.007
0.006
0.007
0.006
0.008
0.005
0.006
0.004
0.004
0.003
I2
I3
I4
I5
I6
I7
I8
I9
I10
I11
I12
11.2
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
<0.005
<0.005
<0.005
<0.005
0.002
<0.005
0.009
<0.005
<0.005
<0.005
0.007
30.9
30.0
30.1
30.8
33.6
34.1
36.3
47.4
49.2
60.3
58.1
0.011
0.012
0.018
0.012
0.018
0.013
0.016
0.025
0.017
0.019
0.032
8.5
8.3
8.4
8.6
8.0
8.3
8.7
9.9
11.0
11.5
10.7
10.8
10.5
10.5
10.8
11.5
10.4
10.3
12.8
13.1
16.5
15.2
35
34
34
35
39
29
28
34
35
39
40
<0.002
<0.002
<0.002
<0.002
0.001
<0.002
<0.002
0.002
0.003
0.005
0.003
13.8
13.4
13.4
13.6
13.9
6.4
3.6
2.2
3.7
4.5
1.4
0.004
0.003
0.004
0.005
0.004
0.007
0.009
0.006
0.003
0.003
0.006
J1
J2
J3
J4
J5
J6
J7
J8
J9
J10
J11
J12
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
-24
-26.5
<0.005
<0.005
<0.005
<0.005
<0.005
0.006
<0.005
<0.005
0.005
0.009
<0.005
0.007
30.2
33.8
42.6
42.6
51.8
54.9
57.7
57.2
58.9
60.7
62.5
66.7
0.006
0.017
0.024
0.026
0.022
0.019
0.021
0.019
0.023
0.024
0.028
0.018
8.8
7.5
8.6
8.8
9.6
9.9
10.0
9.9
10.2
10.1
9.8
10.1
10.6
11.1
12.4
11.1
13.1
13.4
13.7
13.4
13.9
13.9
14.1
15.4
34
42
34
25
28
29
31
33
35
34
33
33
<0.002
<0.002
0.003
0.004
0.004
0.005
0.005
0.004
0.003
0.005
0.007
0.006
13.8
13.8
3.2
1.8
2.3
2.1
2.1
1.9
2.1
1.6
1.6
1.6
0.005
0.007
0.006
0.006
0.006
0.006
0.006
0.005
0.008
0.004
0.004
0.006
86
Hwy PP
Depth
As
Ca
Cu
K
Mg
Na
Pb
S
Zn
K1
K2
K3
K4
K5
K6
K7
K8
K9
K10
K11
K12
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
0.008
0.005
20.2
19.7
19.7
19.8
19.5
16.7
21.2
22.8
31.4
35.2
49.7
66.4
0.011
0.007
0.007
0.005
0.009
0.016
0.013
0.016
0.018
0.020
0.017
0.033
4.9
4.8
4.8
4.8
5.0
5.2
5.8
6.2
7.6
7.3
7.5
7.6
7.1
7.1
7.0
7.1
7.0
5.6
7.0
7.5
9.8
10.4
12.6
16.2
14
14
14
14
13
6
6
6
7
7
9
10
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
9.0
8.8
8.8
9.0
8.6
5.0
4.0
2.0
1.5
1.4
1.1
1.8
0.008
0.004
0.005
0.003
0.004
0.006
0.007
0.007
0.011
0.009
0.011
0.019
L1
L2
L3
L4
L5
L6
L7
L8
L9
L10
L11
L12
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
-19
-21.5
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
19.7
19.6
19.3
17.6
16.7
15.5
16.1
16.3
19.2
24.7
29.2
25.5
0.012
0.013
0.015
0.024
0.026
0.028
0.030
0.031
0.033
0.039
0.032
0.020
4.9
4.8
4.8
5.0
5.0
4.9
5.3
5.5
6.0
6.1
5.8
5.4
7.0
7.1
7.0
6.4
5.9
5.4
5.6
5.6
6.5
7.7
8.1
7.3
14
14
14
11
6
5
4
4
4
5
5
5
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
8.9
8.9
8.8
6.9
4.3
4.3
4.5
3.4
2.3
1.5
1.0
0.9
0.006
0.007
0.005
0.010
0.007
0.007
0.007
0.007
0.008
0.010
0.014
0.013
M1
M2
M3
M4
M5
M6
M7
M8
M9
M10
M11
M12
11.2
8.7
6.2
3.7
1.2
-1
-3.5
-6.2
-8.7
-11.3
-13.8
-16.5
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
20.0
19.9
19.6
19.3
19.2
16.0
14.9
14.6
13.7
13.8
14.9
15.2
0.003
0.004
0.006
0.007
0.007
0.010
0.013
0.012
0.011
0.013
0.012
0.016
4.8
4.8
4.7
4.7
4.7
4.3
4.3
4.1
3.9
3.7
3.5
3.3
7.1
7.2
7.1
7.0
7.0
5.9
5.4
5.2
4.9
4.8
5.0
4.8
14
14
14
14
13
5
5
4
4
4
4
4
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
9.0
9.1
8.9
8.9
9.3
13.2
12.7
12.9
12.3
12.4
13.2
13.8
0.008
0.005
0.005
0.004
0.003
0.004
0.005
0.003
0.004
0.004
0.004
0.006
87
Stream Ionic Concentrations
Ion
As
Ca
Cu
Fe
K
Mg
Mn
Na
P
Pb
SO4
Zn
NO3
Cl
HCO3
Stadt
0.00
204.35
0.02
0.05
14.96
106.97
0.05
350.16
0.88
0.00
39.69
0.05
14.44
424.51
137.12
Hwy K
0.02
128.76
0.02
0.10
9.52
68.94
0.09
126.47
0.33
0.00
24.80
0.35
6.21
167.83
104.08
mg/L CaCO3
Swedish
0.00
87.84
0.02
0.92
10.03
45.98
0.20
80.75
0.45
0.00
15.23
0.01
2.90
139.48
88.44
Elm
Hwy PP
0.00
0.01
90.60
43.22
0.02
0.03
0.69
0.89
8.96
9.19
48.88
23.11
0.20
0.12
86.15
24.50
0.18
0.33
0.00
0.00
16.96
9.79
0.06
0.23
2.18
1.37
116.21
38.50
86.55
43.31
88
APPENDIX C - ACRONYMS
DO – Dissolved Oxygen
EPA – Environmental Protection Agency
EPC – Equilibrium P Concentration
MWWTP – Marshfield Waste Water Treatment Plant
N – Nitrogen
P – Phosphorus
PLCD – Portage Land Conservation Department
PP – Particulate P
PW – Pore-water
PWE – Pore-water equilibrators
RP – Reactive P
TP – Total P
USGS – United States Geological Survey
UWSP – University of Wisconsin Stevens Point
WEAL – Water and Environmental Analysis Lab
WWTP – Waste Water Treatment Plant
89
APPENDIX D - PICTURES OF LOCATIONS
The following pictures were taken at time of sampling.
Transect 1/Transect 2
PWE
Sonde, Transducer
Flow
Figure 26. Stadt Road site
90
PWE
Transect 1/Transect 2
Sonde, Transducer
Flow
Figure 27. Hwy K site
PWE
Transect 2/Transect 1
Sonde, Transducer
Flow
Figure 28. Swedish Road site
91
Transect 2/Transect 1
Sonde, Transducer
PWE
Flow
Figure 29. Elm Road site
Transect 1/Transect 2
Along edges
Sonde, Transducer
PWE
Flow
Figure 30. Hwy PP site
92