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THESIS
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EJBRARY
Michigan State
University

 

 

This is to certify that the
thesis entitled
THE TRACE EVIDENCE CONCENTRATOR:
A SYSTEM FOR ISOLATING TRACE EVIDENCE
FROM SOIL SAMPLES

presented by

Jessica G. Johnston

has been accepted towards fulfillment
of the requirements for

M.S. degree in Criminal Justice

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Datew

O-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

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ma W14

THE TRACE EVIDENCE CONCENTRATOR:
A SYSTEM FOR ISOLATING TRACE EVIDENCE FROM SOIL
SAEEHHES

BY

Jessica G. Johnston

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

School of Criminal Justice

1997

JKBSTRAfifl?

THE TRACE EVIDENCE CDNCENTRATOR:
A METHOD FOR ISOLATING TRACE EVIDENCE FROM SOIL
SAflflflflES

BY

Jessica G. Johnston

This research project was conducted in order to
develop and test a rapid, quantitative, and efficient
method of trace evidence isolation from soil samples. The
Trace Evidence Concentrator (TEC) is a hydropneumatic
elutriation system that operates on a differential density
principle in order to perform this separation task. That
is, various low density items of trace evidence may be
successfully separated from mineral soil particles by
subjecting samples to this system. Standard samples of
human hair, carpet fibers, and, automobile paint chips were
combined with various soil standards and processed with the
TEC. Trace evidence recovery ranged from 86% to 100% for
each of the three items and the TEC proved to be 21% more
time efficient than a conventional manual dryesieving

method for processing large volumes of soil.

To my grandmother, Agnes L. Johnston. Thank you, for all
of your love and support.

iii

ACKNOWLEDG-INTS

I have sincerely appreciated the tremendous support
provided by my project supervisors throughout this
endeavor. I was especially fortunate to have had the
opportunity to engage in interdisciplinary research under
two very fine professors, Dr. Jay Siegel and Dr. Alvin
Smucker. I would like to thank Dr. Siegel for sharing his
expertise in trace evidence recovery and analysis, and Dr.
Smucker for broadening my scientific horizon to include the
realms of plant and soil sciences (engineering, plumbing,
and mechanics) .

Also, my special thanks to Dr. Fred Erbicsh and the
Office of Intellectual Property who provided the financial
support for this research.

Finally, thank you to my family and friends who have
tolerated sporadic panic attacks and always provided the

necessary guidance.

iv

TABLE OF CONTENTS

LIST OF TABLES OOOOOOOOOO OOOOOOOOOO OOOOOOOOOOOOOOOOOOOOO COO... ...... Vi
LIST OF FIGURES .............. . ................... .......... Vii

IMRODUCTION 0.... ...... OOOOOO OOOOOOOOOOOOOOO 00.... 0000000000000 0.0... 1
Literature review . ................. "an" ........... .u" 3

MATERIALS AND METHODS .......... ............. . ....... 7
Apparatus OOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOO ..... I... ...... 000.00.00.00 7
Procedures 0... OOOOOOOOO OOOOOOOOOOOOOOOOOOOOOO0.000000000000000000000 10

Trace Evidence from Soil at a Simulated

crime sceneOOOOOOOOOOOOO0......OOOOOOOOOOOOOOOOOO0.00000000000000000.011
RESULTS AND DISCUSSION. . .................... .......... .. 15
SUMMARY AND CONCLUSIONS ................. . ........... 20

APPENDIX ............................................. . ................. 22

BIBLIOGRAPHY ..... . ......... . .................. ......... 24

LIST OF TABLES

Table - 1 Trace evidence recovery from three
soil types by the TEC (12 replications in total) ............ 15

Table - 2 Air-dry weight values of soil samples from
experimental units of simulated crime scene ..................... 16

Table - 3 Trace evidence recovery from
experimental units of the simulated crime scene. ............ 17

vi

LIST OF FIGURES

Figure - 1 A diagrammatic illustration of the Trace
Evidence Concentrator .......................................................... 9

vii

INTRODUCTION

The extraction of trace evidence materials from crime
scene soil samples has remained a somewhat neglected area
of research in forensic science. Trace evidence may be
useful in event reconstruction and the association of
people, places, and things. The most common techniques
implemented for the processing of soil for evidentiary
purposes involve manual dry sieving and/or vacuuming,
accompanied by visual microscopic observation and forceps
removal. Trace evidence of 'various forms (e.ga hairs,
fibers, glass, and paint) may be associated with various
soil materials. This mixture often results from. crimes
committed in various modes and environments. The focus
here is to develop a fast, efficient, and continuous means
by which trace evidence materials may be quantitatively
separated from soils, without altering and/or destroying
the evidence.

The necessity for a continuous separation technique
arises from the inherent limitations encountered with the
utilization of currently accepted methods. These methods
are generally subjective, time consuming, and relatively

inefficient. Furthermore, if trace evidence materials are

l

2
obscured due to the adherence of soil particles they may be

overlooked . A continuous trace evidence separation
technique would allow analysts to process numerous soil
samples from a scene and quantitatively recover
uncontaminated trace evidence from large sample volumes
more effectively. Such a technique could be successfully
implemented and tremendously useful at crime scenes and in
situations involving victim burial, explosions, cremations,
and mass disasters in which trace evidence items are often
combined with surface and/or deeper soil material.

The primary objective of this study was to develop and
test a hydropneumatic evidence elutriation system for
separating trace evidence from mineral soil materials.
This method combines the elutriative separation of
evidence, contained in soil samples, with a sieving process
which accumulates trace evidence. Combinations of a high
energy water vortex, air dispersion, water elutriation, and
low energy separation and concentration by sieving separate
lighter evidentiary materials from heavier mineral soil
fractions. The system is based on the principle that
materials having densities less than that of the
surrounding soil particles will be successfully separated
and elutriated to a submerged sieve. Soil samples may be

continuously fed through an inlet until accumulated soil

3
sediments interfere with maximum trace evidence separation.

Another objective of the proposed research was to determine
how efficiently various trace evidence materials may be
separated from soil samples utilizing the hydropneumatic
elutriation system. Recovery efficiencies by the TEC were
compared to those of conventional manual dry sieving and
visual examination methods. System efficiencies were based
upon the quantities of trace evidence recoveries and sample

processing times .

W

A similar hydropneumatic elutriation system has been
utilized to extract root materials and other organic soil
material from soil samples (Smucker, 1993; Srivastava,
Smucker, McBurney, 1982). This system also separates
materials based on differential density elutriation and has
proven to be an efficient quantitative method of root
system isolation. Used in conjunction with computer
imaging,' Ihydropnuematic elutriation allows precise
quantitation of root system components (Smucker, 1993).
A device consisting of a battery of eight elutriation
columns is commercially available for separating root

materials from mineral soils. It was, therefore,

4
recognized that a comparable method may be utilized for the

separation of trace evidence materials from soil samples.
Conventional methods for the isolation of trace
evidence from various substrates do exist; however, these
techniques are generally limited to the processing of low
volume dust samples (garments, and the like), and thus are
not implemented specifically for high volume soil samples.
Several authors suggest that “hand" picking, which involves
the observation and subsequent removal of trace evidence
material from various substrates (garments, carpet, dust
samples) with forceps, needles or magnets, is the best
method of evidence collection (Gaudette, 1988; Murray and
Tedrow, 1992; Palenik, 1988; Saferstein, 1995; Suzuki,
1993); Swanson, Chamelin, and Territo, 1996). Murray and
Tedrow (l 9 9 2) sugges t that fol lowing this ini tial
examination the material should then be observed under a
stereo-binocular microscope, followed by forceps removal of
evidentiary items. These methods, however, are extremely
tedious, time consuming, and subject to human error,
especially in instances of mass disaster and cremation for
which trace evidence may be combined with large volumes of
soil. Others suggest that trace evidence materials be
collected via vacuuming , tape - li f ting , shaking , or

scraping , fol lowed by microscopic examination and

5
separation of evidence with forceps removal (Bisbing, 1982;

Osterberg' and.‘Ward, 1992; Palenik, 1998; Suzuki, 1993).
However, these methods do not apply generally and are not
commonly’ used for evidence extraction from. soil samples
alone. Thus, the necessity for the development of a more

quantitative and efficient technique is evident.

MATERIALS AND IITHODS

We

Materials of construction for the Trace Evidence
Concentrator (TEC) were similar to the hydropneumatic
elutriation system for separating roots with several
significant modifications (Smucker, et a1., 1982). The TEC
system includes various engineered components of polyvinyl
chloride, brass clamps, and tygon or rubber tubing. These
components were sealed together using PVC glue or silicone
sealant. The base of the TEC elutriation chamber was
constructed by sealing a 16.9 (i.d.) x 8.5 cm cap (Figure
13) to the 15.3 (i.d.) x 45.7 cm elutriator tube (Figure
1C), with a wall thickness of 0.8 cm. To create a high-
kinetic energy washing environment, four sprayer nozzles
(type, T-jet 8003) (Figure 13) were installed around the
circumference and through the cap/chamber walls at an
approximate acute angle of 84 degrees. In order to lift
the cleaned particles of trace evidence to the surface of
the elutriator tube five air-jet (Figure 11) nozzles were
installed through the base of the cap, with four equally
spaced around its perimeter and one in the center. The

elutriator tube cover (Figure 1D) is a PVC reducer with

'7
an inside diameter of 16.9 to 4.7 cm, combined with a

reducing collar with an inside diameter of 6.1 to 4.7 cm.
The tube cover is equipped with four clamps to eliminate
leakage and also includes the transfer tube (Figure 13) and
low-kinetic energy sieve assembly (Figure 1F and G). The
transfer tube and low-kinetic energy sieving assembly
consists of two 4.6 cm couplers, an 3.8 x 18.0 cm PVC tube
(Figure 13), and a submerged primary sieve (Figure 1F),
with a small air-escape hole drilled at the top of the
transfer tube. The submerged primary sieve, containing a
screen with an aperture of 0.34 m, is submerged in water
bath (Figure 16) to a depth of 1 cm above the screen. To
accommodate large soil samples and facilitate multiple
introductions of samples into the TEC system, a continuous
feed column (Figure 1A) was installed through the wall of
the elutriator tube consisting of a 3.8 cm (i.d.) street-e1
3.8 (i.d.) x 62.8 cm PVC pipe. A small hole (Figure lJ)
was drilled in the side wall of the feed column and
plugged with a rubber stopper, to initiate drainage of the
elutriation chamber before removing the top cap (Figure 1D)
between samles. A second source of air was also added to
flush any remaining evidentiary particles from the base of

the continuous feed column, by removing the access funnel

8
and applying air pressure to the top of the continuous feed

column (Figure 1A), during the elutriation process.

 

 

 

 

 

 

 

 

 

 

 

Figure 1. A diagrammatic illustration of the Trace Evidence

Concentrator

10
Procedure

In order to test and evaluate trace evidence recovery
by the TEC system it was necessary to determine maximum and
minimum air and water pressures required to elutriate trace
evidence materials without eluting coarse sand and silt
particles onto the primary sieve. Soil samples without
trace evidence were elutriated to determine the maximum
pressures. Trace evidence materials, including human
hairs, automobile paint chips, and carpet fibers, were then
run through the TEC without soil materials, to determine
the minimum pressures necessary to elutriate evidentiary
items alone. Preliminary testing revealed that optimum air
and water pressures were measured at 10 and 40 psi,
respectively, for the most effective separation and
deposition of trace evidence on the primary sieve (See
Appendix A for detailed TEC protocol).

Preliminary experimentation was also performed to
determine the basic effectiveness, known as percent
recovery, for composite soil samples and standards of trace
evidence from different soil types. Composite samples
consisted of 150g of soil combined with 10 items each of
human hair, automobile paint chips, and carpet fibers.
Four 150g soil subsamples were obtained from three

different soil types including Tappan clay loam, Kalamazoo

11
loam, and Parkhill loam. Four replications of mixed

samples were performed for each soil type, for a total of
twelve replications. Initially, each 1509 sample was
exposed to the elutriation system for 15 minutes; however,
during the course of sample processing it was discovered
that elutriation time could be decreased to 10 minutes with
the addition of a second air source employed to flush out

the continuous feed column.

W

The protocol for determining the efficiency of
quantitative separation of trace evidence from soil by the
TEC compared to that of a conventional manual dry sieving
and visual examination method required a completely
randomized block experimental design, with three double-
blind treatments having four replications. A simulated
crime scene was established first by filling twelve 38.1 x
50.8 x 12.7 cm plastic containers, referred to as
experimental units, with approximately 6.5 cm soil. The
coarse textured soil, contained some aggregated clay and a
considerable amount of plant residue. Variable numbers of
trace evidence, including human hairs, automobile paint
chips, and carpet fibers were uniformly distributed within

eight of the experimental units, by an individual who was

12
not the TEC operator. Controls, or soils without trace

evidence were randomly selected from four of the twelve
experimental units. Soils from eight experimental units
(four with trace evidence and four without) were subjected
to the TEC system. Four experimental units (containing
trace evidence) were processed by the conventional manual
dry sieving and visual examination method.

Operation of the TEC system involves, securing the air
and water tubes to the appropriate fixtures. Air flow is
initiated and adjusted to approximately 10 psi before the
water is turned on. The cover, transfer tube, and sieve
assembly are then secured and the water set to 40-45 psi.
The elutriation chamber is filled and the primary sieve
submerged in at least 1 cm of water. A sample of
approximately 4509 of soil is pored into the continuous
feed port through a funnel attached to the continuous feed
column, in three subsanmles of 1509 at 30 second intervals.
The continuous feed column is flushed with water for 10
seconds and the TEC is run for 10 minutes. Following the
10 minute elutriation period, the TEC is flushed, drained,
disassembled, and emptied. This process involves removing
the primary sieve and flushing the continuous feed column
twice with air, forcing excess water into a container below

the transfer pipe. The extruded water is subsequently

13
emptied into the submerged primary sieve. The water flow

must then be reduced to 10 psi and the stopper removed from
the lower end of the continuous feed column for drainage.
Following drainage, the cap at the top of the elutriation
chamber is removed and the sediment emptied into a large
metal sieve. The contents of the primary sieve must then
be washed into a white tray and floated in water for visual
examination. Repeat these procedures for the remainder of
the soil samples, and ensure adequate rinsing of all TEC
components between sample containers to collect any trapped
trace evidence. Total time for sample processing and total
trace evidence recovery was recorded.

Visual examination of the sieve contents involves the
use of a high-powered illuminated magnifier. Visual
examination occurred during the ten minute elutriation
period. The white tray was placed under the magnifier and
scanned for trace evidence. The organic sediment should be
dispersed, floated, and permitted to settle at least five
times in order to facilitate the observance of trace
evidence. Any trace evidence observed was subsequently
removed with forceps and stored.

Four experimental units were processed using a
combination of manual dry sieving, utilizing a nest of wire

sieves and visual examination, with the assistance of an

14
illuminated magnifier and binocular microscope. This

method involves first arranging a column of sieves with
apertures measuring from top to bottom 6.30 mm, 4.76 mm,
2.00 mm, 1.00 mm, and 0.42 mm. Then approximately 6509 of
soil sample is measured and added to the top of the sieve
column. The top sieve is covered and the column manually
sieved for 30 seconds to facilitate the separation of trace
evidence from soils. The cover is removed and the top
sieve emptied onto a white sheet of paper. The paper and
sample are then placed under the magnifier and scanned for
trace evidence. Examination under a binocular microscope
at 50x may be necessary for further trace evidence
separation. Any trace evidence observed is removed with
forceps and stored. It may be necessary to further agitate
the column of sieves between sieve-content examination to
ensure maximal separation of soil and trace evidence
through the sieve series. Repeat these procedures with the
remaining soils from the experimental unit. Total time for
sample processing and total trace evidence recovery was

recorded.

15
RESULTS AND DISCUSSION

Preliminary experimentation revealed that the TEC was
highly effective in elutriating trace evidence particles
from soil three different soil types. The total evidence
recovery values from Tappan Clay Loam, Kalamazoo Loam, and
Parkhill Loam for human hair, automobile paint chips, and
carpet fibers ranged from 93-10096. Individual means and
standard deviations are presented in Table 1.

Table 1. Trace evidence recovery from three soil types by
the TEC (12 replications in total).

 

 

 

 

 

Soil Type Human Hair Paint Chips Carpet Fibers
% % %

Tappan Clay Loam 98(18)* 100(10) 93(115)
(n=4)

Kalamazoo Loam 100(10) 95(110) 100 (:0)
(n=4)

Parkhill Loam 100(10) 100110) lOWiO)
(n=4)

 

 

 

 

*Values in () are standard deviations of the percent

It must be noted, however, that on occasion paint
chips were retrieved from the bottom of the elutriation
chamber. That is, because some paint chips were comprised
of several layers, increasing their density, they tended to
remain with the coarse mineral fraction. However, these
items were thoroughly cleaned and easily separated from

this fraction following the elutriation period. Similarly,

 

16
other higher density trace evidence items such as glass

fragments and rubber pieces could be recovered from the
coarse mineral fraction, but none of these items ‘were
generally deposited on the primary sieve.

Simulated crime scene results indicate that both the
TEC and manual dry sieving are effective quantitative
isolation techniques for trace evidence combined with large
quantities of soil. To aid in the efficiency comparison
between these two separation systems it was necessary to
determine means and standard deviations for air-dry weight

values of simulated crime scene soil experimental units

(Table 2).

Table 2. Air-dry weights of soil samples from experimental
units of the simulated crime scene.

 

 

 

 

 

Soil Condition TEC Elutriated Samples sieved Samples
(9) (9)
Blank Control 5173.1(1315.31)
N/A
(ns4)
Trace Evidence 5177.9(1283.25) 4986.5(i374.77)
(n=3) (n=4)
' l 4. 2 .
Combined 5 7 8;:768 38) N/A

 

 

 

The TEC method of evidence concentration proved to be
an effective, efficient, and quantitative technique for
trace evidence separation. Total recovery results for

human hairs, automobile paint chips, and carpet fibers were

 

17
86%, 87%, and 100%, respectively; Means and standard

deviations are presented in Table 3.

Table 3 also depicts the total trace evidence
recovery results for the manual dry sieving method.
Similarly, this technique proved to be very effective.
Total recovery results for human hairs, paint chips, and
carpet fibers were 92%, 100%, and 100%, respectively.

Table 3. Trace evidence recovery from experimental units
of the simulated crime scene.

 

 

 

 

 

5°11 TEC Elutriation Manual Sieving
Condition X/Y* % X/Y* %
Blank
Control 0(10) 0(10) N/A N/A
(n-4)
Trace
Evidence
Human 86(13) 19/20,9/10, 92(13)
Hairs 7/7'4/7'1/1 (na3) 11/12 (n-3)

 

Paint l7/22,10/1O 87(115) 11/11,0/0, 100(10)

 

Chips 9/13,5/5 (n-4) 7/7,2/2 (na4)
Carpet 9/9,11/11, 100(10) 13/13,3/3, 100(10)
Fibers 14/14 (n=3) 26/26,3/3 (n=4)

 

 

 

 

 

 

 

*X Number of items recovered
*Y’ Number of items in sample acquired from. experiment
director, following separation work.

Trace evidence recovered by both the TEC and manual

sieving methods were not significantly different, Table 3.

However, the time required to process each kilogram.of soil

18
with the TEC was 34.1(11.0) minutes and with the manual

sieving method was 41.1(11.3) minutes. Thus, the TEC was
an average of 21% faster than the manual sieving method for
processing experimental units.

Because the TEC had not been exposed to the magnitude
of soil sample encountered in this portion *of the
experiment some trouble-shooting was necessary during
sample processing. That is, an optimum amount of soil
sample had to be determined in order to prevent system
back-up, which did indeed occur during the processing of
the first sample. This back-up could thus explain the
diminished evidence recovery, for paint chips in particular
compared to that of preliminary experimentation. TEC paint
chip recovery was also slightly low for the fourth sample.
The explanation here involves the nature of the soil. The
high organic content of soil employed as the substrate may
have impaired recovery. That is, following sample
elutriation it was necessary to examine the primary sieve
contents and remove the trace evidence particles from the
organic material. This process was somewhat hindered by
the high organic content and, thus could explain the lower
paint chip recovery. These results do not, however,
compromise the value of utilizing the TEC for trace

evidence recovery. Instead they provide further insight

19
for determining the samples for which it may be optimally

enmloyed. That is, implementation of the single TEC unit,
may be most effective for samples consisting of either.
small volumes of high organic content soils, or large
volumes of low organic content soils. However, the TEC is
designed for the potential of operating collectively with
several other units. In order to most effectively process
large volumes of high organic content soil an arrangement
of THC units with a mechanized device for routinely
emptying the primary sieve could be employed. Such a
combination of several TEC systems would effectively
prevent organic content from accumulating on the primary
sieve and obscuring trace evidence. Thus, facilitating

trace evidence removal from primary sieve contents.

20
SUMMARY AND CONCLUSIONS

With regard to overall time efficiency the TEC is
definitely superior. The manual dry sieving and visual
examination required an average of 21% longer per kilogram
of soil processed than did the TEC. This difference may
not appear significant here, however, incidents such as
explosions, arsons, and the like do occur in which hundreds
of kilograms of soil may require processing in order to
locate important trace items. Although the TEC is not
designed to recover insoluble or soluble chemicals that are
not present in an aggregated form, it may be implemented
after chemical analyses in order to recover solid
incendiaries associated with such incidents.

In summary, the TEC system would appear to be the
obvious candidate for crime scene investigators faced with
the challenge of isolating trace evidence from both small
and large soil sample volumes. The effectiveness of the
TEC system has been clearly demonstrated by the research
conducted. The results reveal that the TEC method provides
a quantitative, user-friendly approach to trace evidence
isolation from soil samples. Furthermore, it is important
to recognize that the TEC system technology is not limited
to the present application, but is designed to accommodate

any further modifications, additions, and/or adaptations

21
that may be required for the separation of any other

desired materials of interest. That is, the TEC system, is
not limited to utilization for trace evidence recovery, but
may be adapted and implemented to isolate materials
associated 'with other disciplines such as anthropology,

archeology, and the like.

APPENDIX

.APPEEHIEK.A

A DETAILED TEC PROTOCOL

I TEC assembly and sample addition

a)
b)
c)
d)
e)

f)

9)

h)
i)
j)
k)

1)

m)

Secure water tube with metal connector

Secure air tube with plastic connector

Turn on and adjust air to approximately 10 psi

Place stopper in continuous feed column

Place transfer tube into tube cover/reducer

Place cover' onto elutriation. tube and. align.*with
clamps.

Place primary sieve into submersion pan

Turn water on and adjust water to 40 psi

Allow TEC to operate to equilibrium

Measure 4509 of soil sample

Add three 1509 portions at 30 second intervals

Rinse continuous feed column ‘with water for 10
seconds

Allow to elutriate for 10 minutes following last

1509 portion

22

 

23

II TEC disassembly

a)

b)

e)

d)

e)
f)

9)

h)

J)

Following 10 minute elutriation period remove
primary sieve

Flush continuous feed column for 5-10 seconds with
air, catch water in a beaker, and repeat

Adjust water to 10 psi and remove stopper from
continuous feed column

Pour beaker contents into submerged primary sieve
and rinse beaker thoroughly

Rinse primary sieve into white tray

Remove feed column and allow to drain

Remove TEC top cover

Adjust water to 40 psi and pouring elutriation

chamber sediment into metal screen

Return to I d) above and continue with next sample

BIBLIOGRAPHY

BIBLIOGRAPHY

Bisbing, R.E. (1982). The forensic identification and
association of human hair. In R. Saferstein (Ed.),

WW9 184-221).
Englewood Cliffs, NJ: Prentice Hall.

Gaudette, Barry D. (1988). The forensic aspects of
textile fiber examination. In R. Saferstein (Ed.),

MW (1313- 209-272).
Englewood Cliffs, NJ: Prentice Hall.

Murray, R. & Tedrow, J.C.F. (1992). Egrensig_§eglggy.
Englewood Cliffs, NJ: Prentice Hall.

Osterberg, J.W; a ward, R.H. (1992). Criminal_

(5th ed.). Cincinnati, Ohio: Anderson Publishing Co.

Palenik, Skip. (1988). Microscopy and microchemistry of
physical evidence. In R. Saferstein (Ed.), Egren§19_

W4 (pp. 161-202). Englewood
Cliffs, NJ: Prentice Hall

Saferstein, R. (1995). -

Forensig_figienge_(5th ed.). Englewood Cliffs,
NJ:Prentice Hall.

Smucker, A.J.M., McBurney, S.L., a Srivastava, A.K.
(1982). Quantitative separation of roots from
compacted soil profiles by the hydropneumatic

elutriation system” Agronomy_flgurnalL_14, 500-503.

Smucker, A.J.M. (1993). Soil environmental modifications

of root dynamics and measurement. _Annual_ngyigu;gfi_
Eh¥£293£h919921_11. 191-216-

Suzuki, Edward A. (1993). Forensic Applications of
Infrared Spectroscopy. In R. Saferstein, Forensic

W4 (pp. 24-70). Englewood
Cliffs, NJ: Prentice Hall.

Swanson, C.R., Chamelin, N.C., & Territo, L. (1996).
CriminaLImsrigation (5th ed.). McGraw-Hill.

24

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