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July 3, 2001
Dear Dennis,
Enclosed please find our third six-month project report on the Nichols site.
If you have any questions concerning the data presented please feel free to contact us.
Department of Agronomy
Crop, Soil, and Environmental SciencesAmes, Iowa 50011-1010
515 294-1360
FAX 515 294-3163
Our results continue to support the conclusion that the ammonium present in these soil samples is “fixed” and thus potentially unavailable for nitrification or nitrate production. We are currently running a series of experiments to determine under what conditions, if any, this “fixed” ammonium can nitrify.
Dennis M. Burchett -Vice President Environmental/Regulatory ServicesUnited Agri Products419 18th Street, P.O. Box 1286
Greeley, Colorado
Iowa State UniversityOF SCIENCE AND TECHNOLOGY
JOtl';er
V -
Sincerely,
QBill EvangelouProfessor 1!
rJ i Chois...E;uc;k._o? -̂------------
O37Z
BY
THIS PROGRESS REPORT WAS PREPARED FOR:
This report includes accomplishments in the third 6-month period of the project.
THIRD PROGRESS REPORT ON SOIL AMMONIUM STATUS OF NICHOLS SITE
AGRONOMY DEPARTMENT IOWA SATE UNIVERSITY
AMES, IA 50011-1010 Phone (515) 294-9237
Fax: (515) 294-3163
V.P. EVANGELOU, PRINCIPAL INVESTIGATOR ([email protected]) LETICIA S. SONON, POST-DOCTORAL FELLOW
JUTTA R.V. PILS, Ph.D. STUDENT
Dennis M. Burchett, Vice President Environmental/Regulatory Services United Agri Products
419 18th Street, P.O. Box 1286 Greeley, Colorado 806-1286 USA
Phone (970) 356-4400
CONTRIBUTING/CONSULTING CO-PIsLarry Halverson, Soil Microbiologist
Robert Horton, Soil Physicist Michael Thompson, Soil Mineralogist
TABLE OF CONTENTS
Page No.
PRACTICAL SUMMARY 11.
TECHNICAL SUMMARY 32.
GENERAL OBJECTIVES 63.
4.. 7
STUDIES CONDUCTED 135.
5.113
5.219
5.330
APPENDICES 346.
ii
78
810
4.14.2
MINERALOGICAL AND CHEMICAL CHARACTERIZATION OF SOIL CLAYS COLLECTED FROM NICHOLS SITE ......
EXPERIMENTS ON K+-Ca2+ EXCHANGE ON THE
ENTIRE EXCHANGE PHASE OF CLAY SAMPLES
METHODOLOGY......................RESULTS AND DISCUSSION
3030
1921
1314
EXPERIMENTS ON K+-Ca2+ EXCHANGE WITH VARIOUS
OSMOTICA....................................................................................................
5.2.1 METHODOLOGY......................5.2.2 RESULTS AND DISCUSSION
5.3.1 METHODOLOGY.......................5.3.2 RESULTS AND DISCUSSION
5.1.1 METHODOLOGY......................5.1.2 RESULTS AND DISCUSSION
EXPERIMENTS ON K+-Ca2+ AND NH4+-Ca2+ EXCHANGE
AT LOW FRACTIONAL LOAD LEVELS..................................
4.2.1 X-RAY DIFFRACTION (XRD)4.2.2 INFRARED SPECTRA (FT-IR)
LIST OF FIGURES
Page No.
15
16
22
23
25
28
iii
Figure 2. Relationship between equilibrium NH4 concentration (CRnh4) and
adsorbed NHZ for NH4+-Ca2+ exchange at low fractional load on soil
samples from three areas (S-l, S-2 and S-3) of the Nichols site...........
Figure 5. Influence of K-load on the exchange phase (Ek) on the Vanselow
selectivity coefficient of soil sample S-l...............................................
Figure 6. Relationship between exchangeable and fixed cations (K+ and Ca2+) at
various K-loads on the exchange phase (Er) for K+-Ca2+ exchange
in S-l soil sample. Lines were drawn to establish trends.........................
Figure 4. Relationship between K-equivalent in the solution phase versus
K-load on the exchange phase for K+-Ca2+ exchange in soil sample (S-l).
The nonpreference line (solid line without data) represents a relationship
when Kv=l.............................................................................................................
Figure 1. Relationship between the equilibrium K+ concentration ratio (CRr)
and adsorbed K+ for K+-Ca2+ exchange at low fractional load on soil
samples. The three data sets represent sampling sites (S-l, S-2 and S-3)
in the Nichols site..........................................................................................
Figure 3. Relationship between the equilibrium K+ concentration ratio
(CRK=K+/(Ca2+)1/2)) and exchangeableK+ for K+-Ca2+ exchange on soil
sample (S-l).......................................................................................................
LIST OF TABLES
Page No.
Table 1. Area of the -1630 cm'1 water deformation band for surface and
subsurface samples of the Nichols site, 11
18
Table 3. Equilibria data of K -Ca exchange on soil sample S-l 27
31
iv
Table 4. Equilibria solution chemistry, adsorbed K+ and fixed NH4+ of S-l
surface soil treated with various osmotica..............................................
Table 2. Equations describing the linear portion of the exchange isotherm
plots of adsorbed K vs. CRk and adsorbed NH4 vs. CRnh4 of soil
samples from three Nichols site areas (S-l, S-2, S-3).......................
LIST OF APPENDIX FIGURES
Page No.
39
40
41
44
v
Appendix Figure 6. X-ray diffractogram for samples S-2 (30-60 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).......................................................................
Appendix Figure 10. X-ray diffractogram for samples S-3 (30-60 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).........................................................................
Appendix Figure 7. X-ray diffractogram for samples S-2 (60-90 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).......................................................................
Appendix Figure 5. X-ray diffractogram for samples S-2 (0-30 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K. treated, and e = K + 100° C treated)....................................................................
Appendix Figure 3. X-ray diffractogram for samples S-l (60-90 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).......................................................................... 37
Appendix Figure 4. X-ray diffractogram for samples S-l (90-120 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).......................................................................... 38
Appendix Figure 1. X-ray diffractogram for samples S-l (0-30 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).......................................................................... 35
Appendix Figure 9. X-ray diffractogram for samples S-3 (0-30 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated)........................................................................... 43
Appendix Figure 2. X-ray diffractogram for samples S-l (30-60 cm) under different treatments (a - untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated)........................................................................... 36
Appendix Figure 8. X-ray diffractogram for samples S-2 (90-120 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated)........................................................................... 42
I-
45
46
47
48
49
50
51
52
53
54
55
56
57
58
vi
Appendix Figure 21. IR-spectra of S-3 (0-30 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 22. IR-spectra of S-3 (30-60 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample) ....................
Appendix Figure 24. IR-spectra of S-3 (90-120 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 20. IR-spectra of S-2 (90-120 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 19. IR-spectra of S-2 (60-90 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 16. IR-spectra of S-l (90-120 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 13. IR-spectra of S-l (0-30 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 23. IR-spectra of S-3 (60-90 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 18. IR-spectra of S-2 (30-60 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 15. IR-spectra of S-l (60-90 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
Appendix Figure 14. IR-spectra of S-l (30-60 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample) ...................................
Appendix Figure 11.treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated)
Appendix Figure 12. X-ray diffractogram for samples S-3 (90-120 cm) under different treatments (a = untreated, b = Mg treated, c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated) ;....
Appendix Figure 17. IR-spectra of S-2 (0-30 cm) under different treatments (a = untreated, b = Ca treated, c = K treated sample)
PRACTICAL SUMMARY1.
The practical significance of the findings described in this report are as follows: First, the
clay minerals contained in the soil of the Nichols site are for the most part smectites. X-
traditional extraction techniques, an index of potential nutrient bioavailability, failed.
This strongly suggested that the soil “fixed” ammonium would not be readily transformed
to nitrate (NO3’) and the soil’s potential to produce NO3 would be most likely negligible.
Additional observations that would be of importance to NO3 production was the amount
elucidated in our follow up experiments.
In order to shed light in some of the above observations, we carried out studies on
available for NO3 production. Furthermore, we found out that there were two soil
1
of water retained by the soil, determined by spectroscopy, when untreated and treated
with potassium or calcium (Ca2+). These data tell us that upon addition of K+ many of
“whole” and “low” fractional isotherms. The purpose of these isotherms was to reveal if
soil “fixed” NH4+ was independent of exchangeable K+ and determine the different soil
the soil samples showed the quantity of water retained by the clay samples increased,
which hints that the clay may release with time some of its “fixed” NH4+. Furthermore,
treatment with Ca2+ showed a large increase in water retention which may also suggest
some potential release of “fixed” NFL/. It appears that there is some conflict between
traditional NFL/ extraction techniques and spectroscopic techniques which would be
sinks of exchangeable monovalent cations that are available on the Nichols site soil
samples. Our “whole” isotherms showed that “fixed” NEL/ was independent of
exchangeable K+. This again suggested that the “fixed” NH/ would not most likely be
ray diffraction evidence suggested that these smectites have the potential to fix
ammonium (NH/) and potassium (K+). Attempts to extract the “fixed” NFL/ and K+ by
to influence the release of fixed ammonium which is subject to nitrification.
soil. We will be using the following approaches:
Control1.
j A |
Sugars with low/high K /Ca ratios2.
• Fresh com vegetation
• Dry com vegetation
• Pure osmoticum
High redox3.
Low redox4.
Lime-induced volatilization5
The purpose of the above treatments is to evaluate potential release of the “fixed” NH4+
on the basis of what we have learned so far. Furthermore, we want to determine how we
can take this released “fixed” NFL|+ and transform it to NH3 gas or nitrogen (N2) gas.
I
2
We are now continuing to elucidate the role of soil redox or Eh on the release of “fixed”
NH4+. Currently we have designed and started to run a number of experiments to reveal
how this above knowledge can be used to remove, if possible, “fixed” NIL|+ from the
weakly. Moreover, the findings revealed that all soil samples tested, using low fractional
isotherm studies, contained negligible quantities of exchangeable NH4+ and most of the
NH4+ present is in the “fixed” or “confined” form. Addition of osmotica (sugars) appears
monovalent Cation sinks. One soil sink held the monovalent cations (K+ or NH«+) very
strongly but not “fixed” and the other soil sink held the monovalent cations (K+ or NH4+)
2. TECHNICAL SUMMARY
accessible sites and non-extractable sites, most likely internal sites. Ammonium ions
occupying clay external or easily accessible clay sites were readily available while those
in the clay internal sites were “confined” and therefore considered unavailable.
Soil samples from the Nichols site as well as normal Iowa agricultural soils appear to
3
unsuccessful. A 3-week nitrification study was performed to determine whether or not
this “fixed” NH4+ fraction could be nitrified (NH4+
exhibit high tendency to fix ammonium (see Project Report No. 2). Attempts to extract
the fixed NH4+ using cation exchange resin and cations, such as K+ and Ca2+, were
The availability of soil “fixed” NH4+ and its possible contribution to groundwater
pollution, in the form of NO3, has been the overall focus of this research project. Earlier
research activities involved chemical and mineralogical characterization of soil samples
collected from the Nichols site. This was followed by a series of experiments that
examined the releasability of “fixed” NH/ under various conditions. Our mineralogical
Distinction in ammonium clay sink was made through chemical means, i.e.,
exchangeable (-available) NH/ fraction was displaceable from clay exchange sites by K
ions (1 M KC1 extraction); “fixed” NH4+ by clay destructive techniques.
analysis showed that the Nichols soil samples (S-l, S-2 and S-3) were highly smectitic in
nature. Owing to the smectite’s expansive properties, NH4 ions were shown to occupy
two distinct clay sites: easily extractable sites, most likely external sites or easily
> NO3-) under a set of optimum
incubation conditions. Our results indicated that soil sample S-l, with the highest “fixed”
NH?, did not produce significant amount of NO3 at any depth compared to soil samples
S-2 and S-3 with lower “fixed” NH/. This implied that “fixed” NH4+ was not
bioavailabie and furthermore "fixed” Nil/ bioavaiiabiiity was independent of soil
sample.
For a holistic understanding of the chemistry of NH4+ in the Nichols site, we needed to
quantity-intensity approach for simulating Nichols site soil conditions. The results of
these experiments would enable us to describe the ability of soil from the Nichols site to
exchangeable with the soil solution. Such observation was in full agreement with our
earlier experimental results which, showed that NH4 ions were tightly fixed by the S-l
clay samples.
A second set of experiments was carried out in order to evaluate the entire exchange
4
maintain a certain cation concentration in solution as influenced by the soil clay surfaces
and the quantity of soil adsorbed NH4+.
phase of the clay samples from the Nichols site. The purpose of this evaluation was to
determine the nature of the clay surface and furthermore evaluate if the quantity of K+ on
The low fractional load isotherm studies suggested that the three Nichols soil samples (S-
1, S-2, and S-3) exhibited comparable ability to adsorb/desorb K+ by the exchanger
phase. However, in the NFLi+-Ca2+ system, the S-l soil sample showed marginal ability
to provide soil solution NH4+ buffering compared to the other two soil samples. It
implied that a large fraction of the adsorbed NH4+ remained “fixed” and, therefore, non
Nichols site. Our experiments describe cation exchange equilibria between soil and soil
solution at relatively low fractional loads of K+ and NH4+ employing a modified
investigate its interaction with other cations, commonly found in all agricultural soils,
e.g., K+ and Ca2+. Our present report (Third Report) provides detailed exchange
reactions of K+ versus Ca2+ and, NFL/ versus Ca2+ in soil samples collected from the
5
the clay controlled the quantity of “fixed” KJ and/or “fixed” NH4+. Throughout the entire
isotherm, K+ ions were preferentially adsorbed over Ca2+ by the exchange sites. The
exchanger demonstrated two classes of sorption sites: high affinity and low affinity sites.
The data suggested that the clay internal sites (interlayers) comprise the high affinity
sites, which were more active in sorbing K at the lower end of the CRk values. In other
words, at the lower equilibrium K+ concentration or ratio (CRk < 0.2), K+ ions were
strongly held. The foregoing observation was also supported by the relatively high
selectivity coefficient (Kv > 22) at this point. As the solution was loaded with more K+
(increasing CRk), the exchanger selectivity for K+ ions decreased implying that these ions
could be easily replaced from the exchange phase. Release of “fixed” NH/ throughout
the entire isotherm was not evident at all. “Fixed” NH4+ remained at ~7.5 cmolc kg'1
regardless of K+-load on the exchanger. This implied that application of K+ or increased
levels of K+ would not have any influence on level of “fixed” NH4+.
A follow-up study on K+-Ca2+ and NTL|+-Ca2+ exchange as influenced by glucose was
carried out to further investigate the effect of osmotic pressure, a potential influence
induced by the decomposition of vegetation in late fall. This study was an offshoot of
our previous findings that showed “fixed” ammonium in glucose-treated soil samples
markedly decreased after a 20-day incubation period (see Project Report No. 2).
Mannitol, along with glucose, was added to soils with solutions of various K+/Ca2+ ratios.
Soil samples representing the control (no osmoticum) generally had higher “fixed” NH/
than those that received osmoticum regardless of the equilibrium K+ concentration ratio
(K+/(Ca2+)1/2). In other words, “fixed” NH4+ decreased upon the introduction of an
osmoticum into the system. The data suggested that some “fixed” NH4+ may become
bioavailable due to the production of osmoticum during decomposition of natural
GENERAL OBJECTIVES3.
6
vegetation on the Nichols site. Our goai is to develop procedures by which bioavailable
NH4+ would be transformed to gas products N2 or N2O.
The purpose of this portion of the overall laboratory investigation was to determine and
characterize K+-Ca2+ and NH4+-Ca2+ exchange reactions in soil samples representing the
Nichols site and relate this to the bioavailability of NH4+. Moreover, the role of
osmoticum in the release of “fixed” NH4+ was investigated to evaluate its potential role
in the remediation strategies for the “fixed” NH4+-rich Nichols site.
4.
METHODOLOGY4.1
X-Ray Analysis. Approximately 150 mg of clay, representing the S-l, S-2, and S-3
areas of the Nichols site, and 10 ml of 1 M KCl.were added to 50-ml polyethylene
centrifuge tubes. The mixtures were agitated in a reciprocating shaker for 30 minutes.
third time, clay suspensions were mounted on ceramic tiles for x-ray examination.
Desired clay orientation was achieved by adding clay suspension in small increments
using a Pasteur pipette. The tiles were washed three times with deionized water to
remove excess salt. The same procedure was followed for clay samples treated with 1 M
MgCh and with deionized water. All tiles were stored in a dessicator containing
saturated MgNCh to maintain a relative humidity of approximately 54%. After x-raying
all equilibrated tiles at 54% relative humidity, the K-tiles were heated to 100 °C and the
Mg-tiles were treated with 30% glycerol prior to x-ray diffraction. X-ray diffraction
analysis was carried out using the Siemens D500 Diffraktometer equipped with Siemens
Kristalloflex x-ray generator.
Fourier-Transform Infrared (FT-IR) Analysis: Clay samples representing the S-l, S-
2 and S-3 areas of the Nichols site were saturated with 10 ml of 1 M KC1 in 50-ml
polyethylene centrifuge tubes. The mixtures were agitated in a reciprocating shaker for
30 minutes. After centrifuging at 1500 rpm for 5 minutes and decanting the supernatant,
7
MINERALOGICAL AND CHEMICAL CHARACTERIZATION
OF SOIL CLAYS COLLECTED FROM NICHOLS SITE
After centrifuging at 1500 rpm for 5 minutes, salt wash was repeated two more times to
ensure complete saturation of the exchange sites by K+. After shaking the samples for the
salt wash was repeated two more times to ensure complete saturation of the clay samples
with K+. After washing with deionized water, the clay samples were air dried for FT-IR
analysis. The same procedure was used to saturate the ciay samples with ca2+ using 1 M
CaCh. The clay samples were mixed with KBr on a 1:10 weight ratio recommended for
FT-IR analysis using diffuse reflectance or DRIFT. The clay-KBr mixture was finely
ground using mortar and pestle and approximately 15 mg of the mixture sample was
placed in an FT-IR sample cup holder and analyzed with the Nicolet Magna-IR 560
Spectrometer.
RESULTS AND DISCUSSION4.2
4.2.1 X-Ray Diffraction (XRD)
NH4+. For example, exchangeable K+ or NH4+ is associated with the > 14 A peak
whereas the 10 A peak represents possible “caged” or “fixed” NH4 or K ions within the
collapsed interlayer of 2:1 expandable clay minerals.
General mineralogical characterization can be made for these soils based on x-ray
diffraction peaks. Spectra 'a' in Appendix Figs. 1-12 represent the untreated samples and
are used as reference. In order to differentiate between 2:1 expanding clay minerals and
8
2:1 non-expanding clay minerals, subsamples representing S-l, S-2 and S-3 soil samples
were treated with Mg2+ (b) and Mg2+ + glycerol (c). In general, all clay samples saturated
with Mg2+ showed a 14 A peak. Magnesium-saturated clay samples were treated with
glycerol to differentiate smectite and vermiculite. If smectite dominates the clay fraction,
the near 14 A peak shifts to >18 A, whereas in the case of vermiculite the 14 A peak
The data in Appendix Figs. 1-12 show x-ray of S-l, S-2 and S-3 samples from the
Nichols site. These XRD data are also used to identify “fixed” or exchangeable K+ or
remains the same, lhe 10 A peak can be due to mica or collapsed vermiculite due to
“caged” NH4 ions. Mica is also associated with a sharp high intensity peak, comparable
to the quartz peak, at a d-spacing of 3.3 A.
smectite.
Description of XRD Spectra
smectite was present in the clay sample.
vermiculite as the dominant clay mineral. In order to provide additional support for
9
eliminated the possibility of chlorite being present in the clay sample, whereas the
collapse of the >14 A to 10 A peak after the KC1 plus 100 °C treatment (e) ensured
observed for Mg treated (b) and for Mg + glycerol treated samples (c), which indicated
presence of smectites. The disappearance of the 14 A peak after KC1 treatment (d)
The untreated (a) and magnesium-treated (b) S-2 clay for the 0-30 cm depth revealed d-
spacing of 14 A. Clay samples representing the lower depths showed an increase in d-
spacings after Mg treatment from 14 A to ~16 A. After application of glycerol (c) to the
Mg-treated clay samples, the interlayer spacing increased to 18 A, eliminating
Clay subsamples representing S-l, S-2 and S-3 soil samples were also treated with IN
KC1 (d) to observe possible enhancement/appearance of the 10 A peak, which would
support presence of vermiculite. The KC1 treated clay samples were then heated to 100
°C (e) to verify which of the two 2:1 clay minerals, smectite or vermiculite, was present.
Collapse of the >14 A peak to the 10 A peak upon heating indicated presence of
Based on the above clay mineralogical characterization, x-ray diffractograms of sample
S-l at all four depths show similar trends. Shift from 14 A to >18 A d-spacing was
minerals.
4.2.2 Infrared Spectra (FT-IR)
10
Intensities of the 14 A and 10 A peaks and their significance in regard to NHZ “caging”
or fixation has been described in Project Report No. 2.
The data in Appendix Figs. 13 to 24 show FT-IR spectra for the soil samples S-l, S-2,
and S-3 of the Nichols surface and subsurface soil samples under different treatments,
distinguishing smectite from vermiculite, KC1 treatment was introduced. Vermiculite
was not present in these samples as the 10 A peak did not intensify upon K-saturation
whereas the lack of a 14 A peak eliminates the presence of chlorite. After heating the K
samples to 100 °C the shift from 14 A to 10 A supported the presence of smectite.
where ‘a’ represents untreated or control, ‘b’ represents Ca-saturated, and ‘c’ represents
K-saturated. Table 1 shows the area of the approximately 1630 cm'1 water deformation
band. This band is associated with water molecules mostly within the clay interlayer.
All clay samples showed a significant increase of water molecules in the interlayer after
the soil sample was saturated with 1 M CaCh. This showed possible clay expansion due
to the Ca ion. However, the corresponding increase in the wavenumber of the NFL/
deformation band (-1430 cm'1), did not support release of the NH4 ion as would be
expected. Only sample S-2 (90-120 cm depth ) indicated a decrease in the NFL/
The x-ray diffractograms of clay sample S-3 were nearly identical to clay sample S-2
with the only difference that the Mg treatment showed 14 A peak as the untreated sample
at all four depths. The increase to 18 A peak after glycerol treatment (c) and the collapse
of the 14 A peak to 10 A after heat treatment, suggested the presence of smectite
I
Table 1. Area of the ~1630 cm*1 water deformation band for surface and subsurface samples of the Nichols site.
Treatment Area Sample-ID TreatmentSample-ID Area
S-2 (60-90 cm)S-l (0-30 cm)
S-2 (90-120 cm)S-l (30-60 cm)
S-3 (0-30 cm)S-l (60-90 cm)
S-3 (30-60 cm)S-l (90-120 cm)
S-3 (60-90 cm)S-2 (0-30 cm)
S-3 (90-120 cm)S-2 (30-60 cm)
16.44
22.53
19.76
8.96
35.36
9.10
10.98
26.91
13.1
12.45
19.38
8.63
17.28
32.91
14.81
Untreated
Ca-saturated
K-saturated
12.91
26.57
11.81
10.59
25.71
6.38
17.28
27.71
13.25
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
Untreated
Ca-saturated
K-saturated
8.69
34.63
15.74
Untreated
Ca-saturated
K-saturated
14.92
25.43
20.22
19.21
25.90
20.18
12.97
28.40
15.48
12
Note that x-ray and FT-IR spectroscopic data suggest certain expected behavior with
respect to soil NH4+ release/fixation. Wet chemistry evidence are needed to verify this
suggestion. The following section provides some wet chemistry evidence on NFL/ and
K+ fixation/exchange behavior.
deformation band from 1431 cm'1 for the untreated sample to 1423 cm'1 for the K+
saturated, and to 1407 cm'1 for the Ca2+ saturated sample. This wavenumber decrease
suggested that expansion of the interlayer weakened the NH4+ clay lattice interaction.
However, all other eleven samples showed an increase in wavenumbers of the NH4+-
deformation band suggesting that NH4+ was in a non-exchangeable form despite
interlayer expansion by cation saturation.
STUDIES CONDUCTED5.
5.1
METHODOLOGY5.1.1
Sample Treatment. Surface (0-30 cm) soil samples from 3 sites (S-l, S-2, and S-3)
the end of the equilibration period, pH and electrical conductivity were measured in each
suspension. The mixture was then centrifuged at 8,000 rpm for 5 min. The supernatant
was collected and analyzed for cations using the atomic absorption spectrophotometry
(AAS). All experimental units were carried out in duplicates.
13
EXPERIMENTS ON K+-Ca2+ AND NH/-Ca2+ EXCHANGE AT LOW
FRACTIONAL LOAD LEVELS
were passed through a 2-mm sieve. Twenty-five milliliters of each solution with a
specified K+/Ca2+ ratio were added to 2.5-g soil sample. The mixture was equilibrated on
a reciprocal shaker at a speed of 180 cycles min’1 for 24 h and at room temperature. At
Solution Preparation: Solutions of varying K+/Ca2+ ratios were prepared using KC1 and
CaCh. The initial K concentrations ranged from 2.9 to 13 mmol L’1 while those for Ca2+
ranged from 3.97 to 11.9 mmol L'1. After equilibration, K+ and Ca2+ concentrations
ranged from 0.28 to 11 mmol L'1 and 0.18 to 8 mmol L’1, respectively, resulting in an
array of CRk. values (0.005 to 0.200 (mol L_1)1/2), simulating the Nichols site.
5.1.2 RESULTS AND DISCUSSION
14
The data in Figs. 1 and 2 show examples of the relationship between the equilibrium
concentration ratio (CRk or CRnh4) and adsorbed K+ or NH/ at low fractional loads. In
the K+-Ca2+ exchange (Fig. 1), the adsorbed K increased as the concentration ratio of K+
in solution increased. The curves were generally curvilinear but the curvilinearity was
more expressed in the S-l soil. In particular, S-l soil sample exhibited curved portions at
CRk values <0.05 and >0.15 (L mol'1)172. This foregoing trend could suggest two things:
high K+ affinity sites were adsorbing K+ at lower CRk values but exchange sites became
inaccessible at high CRk values. One plausible explanation for the behavior of S-l soil
sample is the “pinching” effect of the K+ ions. Perhaps, the clay interlayers collapsed
towards the K+ ions as the latter enter the internal surfaces. Under this condition, the
internal surfaces would be excluded from any exchange reaction. The K+-Ca2+ exchange
would now be limited to only certain sites and hence, decreasing the exchangeable K+
concentration at a given CRk level.
Unlike in S-l soil, the exchangeable K+ concentrations in S-2 and S-3 soil samples
concomitantly increased with CRk. This trend may indicate that the loading of K+ ions in
the solution did not alter the clay exchange sites in adsorbing/desorbing K+ ions. Simply
put, the interlayers could have not participated in the exchange process or K+ did not
induce an interlayer “pinching” effect within the range of CRk this experiment was
carried out. Subsequently, the K+-Ca2+ exchange in S-2 and S-3 soils was exclusive to
readily exchanging surfaces of the clays only. The surfaces may include expanded
interlayers and/or external surfaces only. One additional point that Fig. 1 reveals is that
S-l soil exhibits little exchangeable K+. This is revealed from the fact that its y-intercept
exhibits a relatively small negative value (0.58 cmolc kg'1; Table 2). The negative value
4.00
3.00
2.00 -
1.00
0.00
-4.00
-5.00
0.000 0.1500.050 0.200 0.250
15
♦ S-1
HS-2
AS-3
o>o o
o- eE,
* -1.00 -I o n
8 -2.00 - ■o <
-3.00
CRk (mol L'1)1/2
Figure 1. Relationship between the equilibrium K concentration ratio (CRk) and adsorbed K+ for K+-Ca2+ exchange at low fractional load on soil samples. The three data sets
represent sampling areas (S-1, S-2 and S-3) in the Nichols site.
0.100
7.0
6.0
-1.0
0.04 0.08 0.12 0.16 0.20
16
-2.0 J—
0.00
Figure 2. Relationship between equilibrium NH4 concentration ratio (CRnfm) and adsorbed NH4+ for NH4+-Ca2+ exchange at low fractional load on soil samples from three areas
(S-1, S-2 and S-3) of the Nichols site.
! <S-1 |
bs-2
•g 2.0 .ag 1.0 ■u <
0.0
CF^fmolL-1)1'2
8.0
17
of the y-intercept reveals exchangeable K+ under the experimental conditions
(approximately 10 meq L' Ca“ in solution). However, the same can not be said for soil
samples S-2 and S-3. These two samples contain large amounts of exchangeable K+
under the experimental conditions, which are designed to simulate soil field conditions.
Note that the y-intercept is highly negative for both soil samples (1.91 and 5.87 cmolc
kg'1). These quantities represent large amounts of soil exchangeable K+.
The NH4+-Ca2+ exchange is graphically presented in Fig. 2. Here, the isotherms are
slightly curvilinear for the three soil samples (S-l, S-2 and S-3) studied. But again, the
isotherm line was more curved at CRnh4<0.05 in the S-l soil sample and such
observation was not necessarily evident in the other two soils. However, unlike K -Ca
exchange, NHi+-Ca2+ exchange does not exhibit major negative y-intercept (Table 2). It
signified that the quantity of exchangeable NH/ was negligible. Any residual inorganic
NH4+ present in the soil was “fixed”. The latter quantity was determined by using the
HF-HC1 procedure, which is designed to extract tightly held NH4+.
Figure 2 also suggests that the newly added NH4+ became exchangeable. This is revealed
by the slope of the plots in Fig. 2. These slopes are relatively small (48 to 74) and signify
exchangeable NH4+. Slope greater than 100 would signify tightly held NH4+ and
significantly greater than 100 would suggest “fixed” NH/. These data suggest that the
ability of these soil samples to fix any additional NH4+ is not apparent. However, the
plots do reveal if the "fixed" NHf1- can become exchangeable which may lead to NO3
formation.
V
R2Prediction Equation y-interceptSoil Slope
- - cmolc kg*1 - -
K-Ca
NH4-Ca
00
0.948
0.989
0.994
-0.59
-5.87
-1.91
-0.59
0.19
0.05
y = 41.95x-0.58
y = 41.89x-5.87
y = 31.21x-1.91
S-l
S-2
S-3
S-l
S-2
S-3
Table 2. Equations describing the linear portion of the exchange isotherm plots of adsorbed K vs. CRr and adsorbed NH/ vs.
CRnh4 of soil samples from three Nichols site areas (S-l, S-2 and S-3).
ExchangeSystem
y = 54.29x - 0.59
y = 74.87x + 0.19
y = 48.06x + 0.05
0.954
0.973
0.977
41.95
41.89
30.21
54.29
74.87
48.06
cmolc kg*‘/(mol L*1)172
5.2
5.2.1 METHODOLOGY
our earlier chemical tests. Potassium-saturated soil (KSOii) was prepared by adding 300
exchange sites. After the third saturation cycle, the supernatant was decanted and the
remaining solid materials were washed thoroughly with deionized, distilled water until
approximately -30% and labeled as KSOii. The calcium-saturated soil (CaSOii) was
prepared by using 1 N CaCh solution following the procedure as described above for
Ksoil-
19
mL of 1 N KC1 to a 150 g soil sample. The mixture was shaken on a reciprocal shaker at
a speed of 180 cycles min’1 and allowed to equilibrate for three days. After equilibration,
EXPERIMENTS ON K+-Ca2+ EXCHANGE ON THE ENTIRE
EXCHANGE PHASE OF CLAY SAMPLES
Soil Preparation and Pre-Treatment: Soil samples representing the S-l area of the
Nichols site were pre-saturated with either K. or Ca . The 0-30 cm depth sample was
selected because generally this depth had the highest level of “fixed” NH/ as shown by
the electrical conductivity registered at -1.0 mmhos/cm (equivalent to approximately 10
meq K+ L’1). The solid materials were partially air-dried to a moisture content of
the liquid was decanted and the solid was again washed with 300 mL of 1 N KC1. These
steps were carried out in three cycles to ensure maximum K+ saturation of the soil
The following initial treatment percentages (% K/% Ca) were used in the experiment: Tj-
5% K / 95% Ca; T2- 10% K / 90% Ca; T3- 20% K / 80% Ca; T4- 30% K / 70% Ca; Ts-
40% K / 60% Ca; T6- 50% K / 50% Ca; T7- 60% K / 40% Ca; Tg- 70% K / 30% Ca; T9-
80% K / 20% Ca; Tio-90% K /10% Ca; T,,-95% K / 5% Ca.
equilibration, electrical conductivity and pH of each tube was measured.
spectrophotometry (AAS). Correction was made for the soil-entrapped solution after
20
Preparation of Solution with Various K+/Ca2+ Ratios: Solutions of different K+ to
Ca2+ ratios and an ionic concentration of 10 meq/L were prepared using KC1 and CaCl2.
Exchange Reaction Experiment: The K+-Ca2+ exchange reaction was carried out
employing a batch technique. Triplicate 2.5-g soil samples were placed in pre-weighed
50-mL centrifuge tubes. The weight of KSOii to Ca50n ratio in each centrifuge tube was
matched with the corresponding K+ to Ca2+ concentration ratio of the solution described
previously. Twenty-five mL of the corresponding K to Ca ratio solution was added to
suspensions were then centrifuged at 8,000 rpm for 5 min and the supernatants were
collected in clean container and later analyzed for K+ and Ca2+ using atomic absorption
equilibration. The solid phase was then extracted with 1 M NTUOAc and extracts were
analyzed for exchangeable K+ and Ca2+. Determination of “fixed” K+ and “confined or
fixed” NH4+ were carried out following the HNO3 and HF-HC1 procedures, respectively.
each of the centrifuge tube. The mixture was placed on a reciprocating shaker for 7 days
under room temperature to reach a K+-Ca2+ exchange equilibrium state. After
The
5.2.2 RESULTS AND DISCUSSION
The data in Fig. 3 show the influence of CRk (CRk = K+/(Ca2+)1/2) on exchangeable K ■+
increasing CRk, there was a corresponding increase in ExK. A closer inspection of the
21
(ExK). The overall plot of CRk vs. ExK produced a curvilinear line approaching a y-
maximum of 18 cmolc kg’1, which, theoretically represents the CEC of S-l soil. Upon
S-l soil sample. Throughout the entire isotherm, all equilibrium data points are above the
nonpreference line, suggesting a preferential sorption of K+ over Ca2+ by the clay surface.
Furthermore, these data point out an abrupt change in the slope of experimental plot as
The data in Fig. 4 demonstrate the relationship between the equivalent fraction of K+ in
the solution phase versus the equivalent fraction of K+ in the exchange phase, otherwise
known as fractional isotherm. The experimental curve illustrates the monovalent cation
preference by the exchanger in a heterovalent exchange reaction (K+-Ca2+ exchange) on
and this fraction may not be exchanging with the solution phase. As the CRk was
increased and the relationship became linear, K+ may have been adsorbed by exchange
sites in the planar or basal surfaces. This fraction of K+ was exchangeable with the
solution. The practical significance of this observation is that the K+ associated with the
less than 20% of the observed CEC of the S-l sample was not readily desorbed or
released to the soil solution, hence not readily available for plant uptake. This is
consistent with expected behavior supported by the FT-IR and x-ray data.
curve, however, revealed a biphasic relationship rather than the expected curvilinear
relationship asymptotically approaching the cation exchange capacity (CEC) of the soil
sample. The plot (Fig. 3) appears curvilinear at lower CRk values and becomes linear at
sthe higher CRk values. This two-part curve suggested' the presence of different sorption
sites on the clay surface. At CRk < 0.20, specific interlayer sites may have adsorbed KT"
18
16
14
12 -
10 -
8 -
6
4 ■
2
0.20 0.40 0.60 1.00 1.20 1.40
22
o 4—
o.oo
Figure 3. Relationship between the equilibrium PC concentration ratio (CRic=K+/(Ca2+)1/2) and exchangeable K+ for K+-Ca2+ exchange on soil sample S-l.
aw
i
u
JU s
4) ©£
AQ
w
I
I
0.80
CRk (mole L'1)’72
x" x'
/
*
*
4
I
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
nonpreference line
0.20- I0.10
Ek (solution phase)
23
0.00
0.00
Figure 4. Relationship between K-equivalent in the solution phase versus K-load on the exchange phase for K+-Ca2+ exchange in soil sample S-l. The nonpreference
line (solid line without data) represents the relationship when Kv=l.
C/5
XS ex
OJD fl a x
Q XO
*
x1
z" t
I t
I
I
I
I
II
I I
/
/
✓ II
f I
0.10 020 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Er approaches zero, which signifies high affinity sites for the monovaient cation by the
clay surface.
24
The data in Fig. 5 show change in cation affinity as a function of cation load on the
exchange phase (Ek). These data revealed that there are at least two classes of exchange
sites with respect to K -Ca exchange in the Nichols S-l soil sample. At low equivalent
K+-load, the soil exhibited high affinity for K+. Furthermore, a strong preference for K+
over Ca2+ is shown up to Ek=0.2, but an abrupt decline in Kv occurred beyond this point.
At higher K+-loads (Ek>0.40), the magnitude of Kv approached 3 indicating a
diminishing preference for K+ by the exchanger phase. The entire isotherm, however, did
not show any reversal of preference, i.e., Ca2+ over K+, but strongly suggested a different
solid and solution phase environment at both ends of the curve. The system behaved as
an ideal solid-solution at higher CRk environments and that the surface was complexing
with the cations uniformly at Ek values >0.40. The significance of these data is that a
fraction of the K+ load was strongly held by the soil. Indirectly, this may also suggest
that any NH4+ associated with these exchange sites would also be strongly held and thus,
relatively unavailable to organisms for producing NO3.
The affinity of an ion by the exchange phase of a soil can be determined by using the
Vanselow selectivity coefficient, Kv. In K+-Ca2+ exchange, the magnitude of Kv usually
represents the relative affinity of K with respect to Ca" by the clay surface. When Kv=l
at a given level of exchangeable K, the exchanger at that level of K+ load shows no
preference for either K+ or Ca2+. On the otherhand, a KV>1 at any given level of
exchangeable K+ signifies exchange preference for K+. Conversely, Kv values less than 1
indicate preference of Ca2+ over K+ by the exchange phase.
50.00
45.00
40.00 -
35.00 -
20.00 -
15.00
10.00
5.00
0.80 1.000.20 0.40 0.60
Ek (exchange phase)
25
0.00 J—
0.00
4
Figure 5. Influence of K-load on the exchange phase (Ek) on the Vanselow selectivity coefficient of soil sample S-l.
;♦ II I I I I II I I II
I t I
I
\
\
\
30.00 -
E 25.00 - e
£
26
perhaps due to protonation of functional groups at the clay edges and planar surfaces. At
low pH, protonation of some functional groups could lend to the reduction in electrical
Another observation in this experiment was that the calculated CEC (sum of ExK and
ExCa) increased towards the direction of the K+-rich end of the isotherm; On the other
surface potential, a condition that would the favor sorption of monovalent ion over that of
divalent ion. As the pH increased, deprotonation of these functional groups would result
in greater surface electrical potential, a condition favorable for Ca2+ sorption resulting in
lower Kv values. Deprotonation, however small, at higher pH may explain the increase in
CEC at the K-rich end of the isotherm.
A graphical presentation of the relationship between exchangeable and fixed cations at
various K-loads on the exchange phase is given in Fig. 6. It (Fig. 6) illustrates the inverse
trends of exchangeable K+ and Ca2+ along the K-load exchange phase axis. At high K+-
load, exchangeable Ca was low and vice versa. Concentration of “fixed” K slightly
increased towards the K-rich end of the isotherm. “Fixed” NH4+, however, remained at
approximately 7.5 cmolc kg'1 all throughout the isotherm, which implied that additional
fixation or desorption was negligible. This observation appeared to be consistent with our
hand, Kv appeared to be influenced by pH; as pH decreased, Kv increased and vice versa.
This pH decrease signifies an increased affinity for the K+ ions by the clay surface
The data in Table 3 show cation exchangeability on S-l soil sample. The data show a pH
gradient on the isotherm. For example, the pH of the K+-rich isotherm was higher
(pH=4.72) than that of the Ca-rich isotherm (pH=4.28). Apparently, Ca was exchanging
with aluminum more efficiently than K+. In fact, the concentration of exchangeable Al3+
at the end of the equilibration period was slightly lower in the Ca2+-rich end of the
isotherm, implying Al3+ release into the soil solution and hence, lower pH.
Table 3. Equilibria data of K+-Ca2+ exchange on soil sample S-l.
Solution Exchangeable Total* Kv“Fixed KpH
Ca KK Ca
mM-
4.28±0.01f 5.18± 0.05 2.94±0.170.80±0.12 9.91±0.39 25.6712.82±0.88 0.86 42.87
nd:4.95± 0.02 3.43±0.071.43 ±0.034.30 ±0.02 12.05±0.43 11.23±0.24 26.71 22.36
4.19± 0.10 4.58±0.153.22 ±0.12 10.96±0.544.30 ±0.01 11.70±0.33 27.23 0.98 12.42
4.63± 0.15 3.48± 0.07 5.21±0.354.29 ± 0.02 8.58±0.81 13.40±0.57 27.19 nd 10.42
6.20±0.275.91 ±0.12 2.71 ±0.08 8.27±0.594.33 ±0.02 13.26±0.55 27.73 nd 8.35
2.02±0.13 7.44±0.19 8.09±0.636.66 ±0.144.41. ±0.06 13.04±0.06 28.57 0.97 7.36
1.50 ±0.17 8.67±0.887.99 ±0.45 7.65±0.644.44 ± 0.03 12.50±0.14 28.82 nd 6.10
10.70±1.070.83 ±0.19 6.15±0.279.68 ±1.55 30.12 nd4.48 ± 0.03 13.26±0.27 4.85
12.48±0.370.41±0.06 4.26±0.4010.68± 0.14 13.78±0.41 30.534.56 ±0.01 1.04 4.21
0.09 ±0.01 16.11±0.11 2.32±0.4511.26± 0.124.66 ± 0.03 14.53±0.86 32.95 nd 3.11
16.31 ±0.2311.49±0.02 0.08± 0.00 1.50±0.26 14.91±0.37 32.724.72 ± 0.02 1.16 3.56
* Total = Exchangeable (K+Ca) + Fixed K♦ ♦ , i - rr- •
Exch.Al
Vanselow selectivity coefficient f Standard deviation
not determined
(L mol4)172cmolc kg'1
« ExK □ ExCa X Fixed NH4
18
16
14
... A...-...12
10
8•X-X- -x- XX6
4
2
0.30.2 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Ek (exchange phase)
28
Figure 6. Relationship between exchangeable and fixed cations (K+ and Ca2+) at various K-loads on the exchange phase (EK) for K+-Ca2+ exchange in S-l soil sample. Lines
were drawn to establish trends.
o0.1
44u
o E u a .2
u aO) u fl o
A ..
□
.J-”
A Fixed K
29
The above overall data strongly suggested that “fixed” K+ and NHZ are constant and
independent of K+ load. We strongly feel that this is a critical information for this
particular project.
earlier findings showing that “fixed” NH/ in S-l soil was energetically strong and
relatively irreversible.
EXPERIMENTS ON K-CA EXCHANGE WITH VARIOUS OSMOTICA5.3
5.3.1 METHODOLOGY
Osmoticum sources and soil treatment: Potassium-calcium exchange reactions under
various osmotica was studied using the batch technique. The osmotica were glucose
(C6H12O6) and mannitol (CgHuOe) both at 4% on weight to volume basis (w/v). Five
grams of S-l soil sample were weighed into 150-mL Erlenmeyer flasks. To one group of
flasks, 2.0 g of glucose was added, another group 2.0 g mannitol was added, and a third
(EC), redox potential and osmotic pressure were measured at the end of the equilibration
period. The osmotic pressure was indirectly obtained by measuring the osmolality of the
absorption spectrophotometry (AAS). The solid materials in the flasks were analyzed for
fixed ammonium following the HF-HC1 procedures.
5.3.2 RESULTS AND DISCUSSION
Data on equilibria solution chemistry at various osmotica are shown in Table 4.
Introduction of osmotica to the solution invariably results in an increase in osmotic
pressure. Osmotic pressure varied from 1.31 to 1.44 MPa in the presence of 4% glucose
or mannitol as compared to 0.19 - 0.22 MPa for the soil solution alone. Solution pH
values were comparable between osmotica and control treatments. The only difference
30
group served as the control (untreated). To each of the sample in the test tubes, 25 mL
of solution composed of various ratios of K+/Ca2+ was added. The mixture was shaken on
a mechanical shaker at 180 cycles min'1 for 24 h. Solution pH, electrical conductivity
solution by a vapor pressure osmometer. The mixture was then centrifuged at 8,000 rpm
for 5 min and the supernatants were analyzed for cations (K+ and Ca2+) using atomic
Table 4. Equilibria solution chemistry, adsorbed K and fixed NH4 of S-l surface soil treated with various osmotica.
Solution phase Solid phase
Osmoticum CRkFixed NH4PH(K+/(Ca2+)1/2)
(mS cm'1)-lxl/2 (MPa)(mol L ) (mV)
H2O (control) 8.93
Glucose (4%) 6.56
Mannitol (4%) 7.07
0.190.210.210.22
1.311.381.401.39
-0.432.732.811.45
3.853.333.243.31
613622622615
7.459.958.849.49
7.615.547.537.59
0.151.721.962.01
3.863.293.263.30
0.142.282.522.61
621623629616
0.15
1.822.002.06
3.86
3.213.213.29
623
619625615
5.25
7.715.657.62
0.023
0.0960.1710.213
1.35
1.441.421.44
-0.43
1.532.551.22
Electricalconductivity
Redox potential
Osmotic
pressure
-0.49*
2.271.770.73
0.0240.0920.1640.214
AdsorbedK
cmolc kg'1
Mean FixedNH/‘
0.0240.0890.148
__________________0.206 _______________________________* Negative value indicates K desorption from the exchange phase. ** Mean fixed NH4 within an osmoticum treatment.
noted was a higher soil pH in the lowest CRk system, a trend consistent in all three
Electrical conductivity (EC) decreased in the presence of osmoticum osmotica.
d-spacing.
bioavailable. These results reveal that sugars released from vegetation in the fall may
32
compared to those without osmoticum as expected. Redox potentials (613 to 629 mV)
were approximately similar in all treatment systems.
which received osmoticum regardless of the equilibrium CRk values. In other words,
“fixed” NH4+ decreased upon the introduction of an osmoticum into the system.
Magnitude of K+ adsorption differed between CRrS within each osmoticum (Table 4). In
the H2O treatment, adsorbed K+ decreased as CRk increased. It was evident from the
above observations that selectivity for K+ was highest at low solution K+ concentration
ratio (K+/(Ca2+)I/2) or CRk- This trend was attributed to soil-site heterogeneity where
highly selective sites for K+ fill up first. Potassium, being a weakly hydrated cation, may
have collapsed the interlayers, leading to NH4+ fixation as well.
The presence of osmotica in the solution phase modified the relationship between CRk-
and adsorbed K+ relationship. In the presence of glucose or mannitol, K+ adsorption
peaked in the mid-CRK range. An apparent trend was noted in the “fixed” NH4+ data.
Soil samples representing the control generally had higher “fixed” NH4+ than those,
The above results were consistent with our earlier findings with respect to glucose (see
Project Report No. 2). In that study, “fixed” NH4+ decreased after a 19-d incubation
period but a large reduction in “fixed” NH4+ was noted in glucose-treated samples. The
x-ray data of the latter soils indicated that the glucose-treated samples displayed a greater
In other words, some “fixed” NH4+ became exchangeable and thus,
33
contribute to the release of “fixed” NH/. We feel that this is important information
which we will use to test if decaying vegetation would release “fixed” NH/.
6. APPENDIX
34
3.3 A
5.0 A-10.0 A 7.2 A 4.2 A3.2 A
' e
0MMTd
Mi
c*•■ •
i b
a Wk
Two-Theta
r
2“T-
23
w cn
"T
6
I
10
I
14I
18
I
28
Appendix Figure 1. X-ray diffractogram for sample S-l (0-30 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
3318
J -18.0 A
C 4. . a > *
-1..OA-14OA
5.0 A 4.2 A7.2 A
?_
e
•• I
c
<2
b
-
■)T Tr
18141062
Two-Theta
I
18
>» ■+j « c a> +■> c
w o>
Appendix Figure 2. X-ray diffractogram for sample S-l (30-60 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
3323 28
3.3 A3.2 A
i
' iiI
----- XJr-.
r jJ. j*
r
-10.0 A
-14.0 A -18.0 A
. - J JU *»
-18.0 A-10.0 A
7.1 A 5.0 A-14.0 A
e
4
c
a
Two-Theta
I
18
I
18
r
2
—r
6
I
23
I
28
Appendix Figure 3. X-ray diffractogram for sample S-l (60-90 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
I
10
I
14 33
> b
5.0 A7.2 A
Sftasi 1 e1 .•
1
c... •_»:-'
b....—r'"M‘
Two-Theta
—I
18—)
33
[
10
—r
6
>» .-W (Jj c a> +■> c
co00
Appendix Figure 4. X-ray diffractogram for sample S-l (90-120 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
V--r^4
1428
I
232
18
ft'’
—"<• -'<*''** 11
- .-7h
1 '■».
, “L ■
J
-14.0 A ~1°.o A 7.9 A
18.0 A
-10.0 A22.1 A
-14.0 A 7.1 A 5.0 A
‘ e
d
b
a
Two-Theta
I
18
I
10
I
33r
2
I
14
I
23T
6
Appendix Figure 5. X-ray diffractogram for sample S-2 (0-30 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
28
c
I
18
CD
3.2 A-14.0 A 7.9 A
3.3 A7.0 A 5.0 A 4.2 A 3.6 A-18.0 A
3.1 A
d
1 f
■Ata c
bb-;
--v""1
a
Two-Theta
c Q>
i
33
i
23r-
2
I
14
k
Appendix Figure 6. X-ray difiractogram for sample S-2 (30-60 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
T*1.
I.J
1810 286
F
llfo-
-10.0 A
12.7 A
I
18
if
? "i!
/ \
i.
>» -M
-14.0 A
-10.0 A
d
c
Two-Theta
e
~l
3318
I
18
r
2
"T“
6
I
28
Appendix Figure 7. X-ray diffractogram for sample S-2 (60-90 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e — K + 100° C treated).
10 14
| 16.5 A ' I ' • -
b
I
23
-18.0 A
18.0 A
-14.0 A
-10.0 A 7.1 A 5.0 A
I
V efi
k/ d!
c,z
b
aTrr T
18 2314 182 6
Two-Theta
I
28
I
10
I
33
Appendix Figure 8. X-ray diffractogram for sample S-2 (90-120 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
-
>» IS c
c
15.8 AI I
J
■ ,3^ ,
I
;V B, IK
'A
V b
P1
I
iI ;.f
1 |
/I ft
KJ
-10.0 A 3.6 A
3.2 A
3.1 A
■ AfcJt fori % iijj.
18
Two-Theta
I
10
I
28
I
23
I
6
-14.0 A
-18.0 A
Appendix Figure 9. X-ray diffractogram for sample S-3 (0-30 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
33142
4.2 A
I
18
-14.0 A-10.0 A
c
b
a
62 10 18
Two-Theta
e
d
I
28
I
14
Appendix Figure 10. X-ray diffractogram for sample S-3 (30-60 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
23 33
18.0 A
I
18
-14.0 A
18.0 A
-10.0 A7.1 A 14.2 A5.0 A
Le
b
a
18
Two-Theta
)
18
I
14
I
23
I
33I
10
r
2
cn
>»
w c 0) +-> c
~F
6
Appendix Figure 11. X-ray diffractogram for sample S-3 (60-90 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
28
id
3.1 A
-14.0 A
3.2 A
-18.0 A-10.0 A 7.1 A 5.0 A 4.2 A
3.1A
efi -i
d
‘ c J,-. ■■• -J /!■
b
a
Two-Theta
I
18
—I
33
]
10
I
23
~r
6
]
14
I
28
I
18
-Ucn
Appendix Figure 12. X-ray diffractogram for sample S-3 (90-120 cm) under different treatments (a = untreated, b = Mg treated,
c = Mg + Glycerol treated, d = K treated, and e = K + 100° C treated).
2
L
>»
W c M. 0>£
<*.•_ r
fT
Ak r ?
I h • •'
3.6 A 3.3 A
36973285
16323619
1871
C
b
a
30003500 2000 1500
-J
Appendix Figure 13. IR-spectra of S-l (0-30 cm) under different treatments (a = untreated, b - Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
,1405
3277
16283694
1875
b
c
3616
a
T
2000 150030003500
-p. oo
Appendix Figure 14. IR-spectra of S-l (30-60 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
1403
3616
20003500 3000 1500
'-O
Appendix Figure 15. IR-spectra of S-l (60-90 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
3693
3500 2000 1500
Appendix Figure 16. IR-spectra of S-l (90-120 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
3000
36921626
3000 20003500 1500
Appendix Figure 17. IR-spectra of S-2 (0-30 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
3325
162831441420
1385
a
20003500 15003000
tn
2500Wavenumbers (cm-1)
Appendix Figure 18. IR-spectra of S-2 (30-60 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2000 15003000
Appendix Figure 19. IR-spectra of S-2 (60-90 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
3500
1624
1866
T
3000 20003500 1500
Ul4^
Appendix Figure 20. IR-spectra of S-2 (90-120 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
334536921628
3616
1424b
1873
C
a
T
3500 20003000 1500
Ch th
Appendix Figure 21. IR-spectra of S-3 (0-30 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
33691629
b
C
I a
20003500 3000 1500
Ui o
Appendix Figure 22. IR-spectra of S-3 (30-60 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
2500Wavenumbers (cm-1)
1868
36221626 1431
3366
b
1863
a
cLA
3692
3000T
3500 2000 1500
Appendix Figure 23. JR-spectra of S-3 (60-90 cm) under different treatments (a = untreated, b = Ca treated,
and c = K treated sample).
2500Wavenumbers (cm-1)
3394 16263621
b1431
1872
a c
T T
30003500 2000 1500
00
Appendix Figure 24. IR-spectra of S-3 (90-120 cm) under different treatments (a = untreated, b = Ca treated,and c = K treated sample).
!
2500Wavenumbers (cm-1)