Society for American Archaeology
The Quantitative Analysis of Soil Phosphate
Author(s): William I. Woods
Source: American Antiquity, Vol. 42, No. 2 (Apr., 1977), pp. 248-252
Published by: Society for American Archaeology
Stable URL: http://www.jstor.org/stable/278986 .
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248 AMERICAN ANTIQUITY [Vol. 42, No. 2, 1977]
ments, and rock cairns found at ridge-back
sites; however, flaked stone materialsof other
traditions are also associated in some cases,
making it impossiblenow to demonstratethe
associationof ridge-backsandstone features.
A few ridge-backscould be fortuitous,but
the great quantity and similarityof both large
and smallspecimensat the site locationsstrong-
ly suggeststhat they areman-made.
It is hoped that other investigatorswill
recognizethis lithic traditionelsewhereas more
archaeologistsbecomefamiliarwith the unusual
Acknowledgments. My thanks to George F. Carter
of Texas A & M University for his encouragement and
assistance in preparing this paper. I am also grateful to
Alan Bryan and Frank E. Poirier for critically review-
ing this paper and to Donald Crabtree for his valued
comments and suggestions that inspired this study.
Finally without the assistance and understanding
of my wife, Lucille Childers, none of this work could
have been possible. The photos are by G. J. Bianchi
and the graphics are by Jaime Servin.
Bischoff, James L., and others
1976 Antiquity of man in America indicated by
radiometric dates on the Yuha burial site.
1957 Pleistocene man in San Diego. Johns
Hopkins University Press, Baltimore.
Childers, W. Morlin
1974 Preliminary report on the Yuha burial,
California. Anthropological Journal of Canada
Rogers, Malcolm J.
1929 Early lithic industries of the lower basin of
the Colorado River and adjacent desert areas.
San Diego Museum Papers 3:16-22.
1966 Ancient hunters of the Far West.The Union
Tribune Publishing Company, San Diego.
Weismeyer, Albert L., Jr.
1968 Geology of the northern portions of the
Seventeen Palms and Fonts Point Quadrangles
Imperial and San Diego Counties, California.
Unpublished M.A. thesis, Department of
Geology, University of Southern California.
Woodring, W. P.
1935 Distribution and age of the Tertiary
deposits of the Colorado desert. Carnegie In-
stitution of WashingtonPublication 148:11-25.
Developments in environmental quality testing have revealed the need for a reappraisal of the methods of
phosphate determination employed by archaeologists. The results of such a reappraisal are presented with
recommendations for the implementation of a new technique of quantitative phosphate determination called
sequential fractionation. With this technique three discrete fractions are determined by differential solubility
criteria. These fractions closely approximate in amount the major types of inorganic phosphate known to be
retained by soils. Sample analyses are presented which indicate that the method can be employed to distinguish
between natural and human deposited phosphate and to identify features.
Soil chemicalchangesresultingfrom human
occupation have relatively recently become a
topic of abandoned settlement studies. Soil
chemistryis altereddirectlythroughthe deposi-
tion and decay of organicandinorganicdebris.
On the microscale,settlementsoils exhibit pH
anomalies and often, greatly increased con-
centrationsof differentcompoundsof calcium,
metals. Phosphoruscompoundsin the form of
phosphatehave provedto be the most stablein
their chemistry and location in a wide variety
Duringthe past three years,the authorhas
been involved in a project part of whose
purpose has been the development of ap-
propriatefield and laboratorymethods for the
analysis of phosphate in settlement soils
(anthrosols).The study has producedan inex-
pensive,versatilefield method for detection of
phosphate which presently is being widely
employed (Eidt 1973; Woods 1975). In addi-
tion, through modificationsof phosphatefrac-
tionation schemes devised for pedogenic in-
vestigations,a quantitativeprocedurehas been
developed by means of which highly accurate
determinationsof discrete chemical forms of
inorganic phosphate in soils from abandoned
settlements have been achieved for the first
It has become apparent that with certain
exceptions, the field method is extremely
worthwhile in site surveys (for example, see
that the method can be most helpful in
reconstructingregional settlement geographies
and in the location and delimitation of in-
dividualsettlements. It is anticipatedthat at a
largerscale of inquiry,the study of phosphate
distributions will reveal house types, field
forms, and the form and function of areasand
Thoughsitescanbe locatedwith the qualita-
tive field test, quantitativeanalysistechniques
are necessary to ascertain the kinds and
amountsof phosphateinvolved.Oncethe latter
areknown, conclusionsaboutthe intensityand
durationof habitationcan be drawn,accurate
phosphate maps compiled, and comparisons
between intersiteand intrasiteelementswithin
Archaeologists and geographerswho have
become interested in the measurement of
human phosphatedepositionshave either sent
samples outside for analysis or borrowed
analyticaltechniques directly from agronomy,
and, in many cases,haveemployedunmodified
procedureswithout a firmunderstandingof the
principles involved. Numerous laboratory
proceduresfor phosphate determinationhave
been employed by abandonedsettlement in-
vestigators. Various researchers have used
able phosphate concentrations (Arrhenius
1931; Lorch 1940; Lutz 1951; Solecki 1951;
Dietz 1956; Eddy and Dregne 1964; and Abt
1968). Unfortunately, the results of these
methods could be highlymisleadingasavailable
phosphateconstitutes only a smallpartof total
soil inorganic phosphate and can vary signifi-
cantlyin amount from seasonto season.When
soils are sent to outside laboratoriesfor analy-
sis, availablephosphatetests arethe only ones
Procedureswith a strongacid extractionare
more reliable (Buehrer 1950; Lorch 1954;
Cornwall 1958). Though adequate for deter-
mining the amounts of calcium oriented
phosphate, acid extractions do not work well
with the iron oxide occluded phosphatefound
in some acid soils, and only a little better for
determining the nonoccluded phosphate as-
sociated with aluminumand iron compounds.
binedinorganic/organicresult,but still tell little
about the nature of the phosphatebeyond its
absoluteamount. Unlike those who haverelied
on the above singleextractionprocedures,only
Mattinglyand Williams(1962) have examined
more than one type of phosphate.These two
soil scientists were able to test for total,
available,andorganicphosphatein a soil froma
Romansite in England.Of the methodsusedin
the phosphate analysis of anthrosols, it has
become increasingly clear that the recently
developed fractionationprocedureis the most
The techniqueis basedupon the differential
solubility of the major phosphate forms in
1957; Syerset al. 1972). Whenthese solutions
are arranged in appropriate sequence, the
to phosphateform (Fig. 1). Readilycarriedout
by students with even minimalchemicalback-
grounds, the technique could be adequately
performed in many laboratoriesof the type
commonlyfound associatedwith anthropology
and geography departments. Detailed
proceduralinstructions and equipment needs
can be found in a recent publication(Eidt and
To illustratesome of the conclusionswhich
can be drawnfrom fractionationanalysis,six
sample results are presented in Table 1. The
total amountof inorganicphosphateis reported
in parts per million elemental phosphorus
(ppmP). Totals for extractions are shown in
percentage figures. Figures in the NaOH&CB
column closely approximate the amount of
nonoccluded aluminum and iron phosphate
found in each sample.In the samemanner,the
CBD column reflectsthe quantityof occluded
aluminumand ironphosphate,whereasthe HCI
column shows phosphatefound to be in com-
bination with calcium. The samples were
chosen to reflect varying degrees of human
Sample 1 was taken from one of a groupof
burials found under a medievalchurch floor.
Due to the dryness of the soil and to the
permanent floor covering, the body experi-
enced little weathering.As a result,mineraliza-
tion of organic matter and slight bone dis-
integrationwere the only evidenteffects of the
last severalhundredyearssince interment.The
total column shows the extremely high
phosphate concentrationswhich are found in
The moderatelyhigh concentrationandfair-
250 AMERICAN ANTIQUITY [Vol. 42, No. 2, 1977]
40 ml 0 1 N NaOH/1 0 N NaCI
12 hr SHAKING/CENTRIFUGE
1 0 N NaCI WASH TWICE/CENTRIFUGE/DISCARD
50 tmilNa CITRATE/Na BICARBONATE
15 min WATER BATH85? C/CENTRIFUGE
25 ml NaCI WASH/CENTRIFUGE
SOLUTION B SOIL
NaCI WASH TWICE/CENTRIFUGE/DISCARD
| 1 50 ml Na CITRATE/Na BICARBONATE
| I 1Og0 g NaDITHIONITE
I I I
15 min WATER BATH 85? C/CENTRIFUGE
i | _ 25 ml NaCI WASH/CENTRIFUGE
| SOLUTION C SOI
1(CBD) |NaCI WASH/CENTRIFUGE/DISCARD
40 ml 1 0 N HCI
4 hr SHAKING/CENTRIFUGE
SOLUTION D SOIL
| 1 11 | t~~~~~~~~~~~~~HCI)
I I (HCI) ~~~~~~~~~~~~(DISCARD)
NON-OCCLUDED P SORBED FOCCLUDEDAl-&Fe-P ACID EXTRACTABLE
Al -& Fe-P DURING (OCCLUDEDAND
EXTRACTION SOMELATTICE)Ca -P
DETERMINED DETERMINED DETERMINED DETERMINED
BY METHOD1' BY METHOD2- BY METHOD2" BY METHOD1'
'Method 1 is the colorimetric technique of Murphy and Riley, 1962.
'-Method 2 is a modification of the isobutyl alcohol procedure of Berenblum and Chain, 1938.
Fig. 1. Flow sheet for soil inorganic phosphate fractionation system (Eidt and Woods 1974:75).
ly even relativedistributionamongthe discrete
fractions of sample 2 are representativeof
phosphatefrom residentialareas.In contrastis
sample 3, also from within the settlementarea
and collected only 75 metersaway.However,it
is from a ceremonial,ratherthan a residential
zone. This conclusionis supportedby both the
ference,the resultsaremuchcloserto whatone
might expect from the moderatelyweathered,
slightlyacidsoilsfoundnaturallyin the area.
The phosphate distribution and concentra-
tion shown with sample 4 reveal that even
modern agriculturalfertilizationactivities pre-
sent few problemsof interpretation.In addition
to being trappedwithin the plow zone, applied
Table 1. Inorganic Phosphate Fractionation Results
CB CBD HC1 Total
1. Medievalburial 40% 22% 38% 2984ppm P
2. Aboriginal residential 37% 30% 33% 833
3. Aboriginal ceremonial 48% 42% 10% 165
4. Modern fertilized field 25% 22% 53% 195
5. Diatomaceous clay 4% 3% 93% 378
6. Marldeposit 3% 4% 93% 302
those found to be associatedwith habitation
It is to be emphasizedthat the last two
samples reveal relatively high phosphate con-
centrationswhich could, if one wereusingonly
a field test or single fraction procedure,be
mistaken as those of an anthrosol. Only the
fractionationsystem shows the distributionof
the majorityof the phosphateis found in only
one fraction, it revealsa lack of humaninflu-
ence on the distribution.By contrast,numerous
tests on soils fromtropicalto borealconditions
have shown that the phosphateassociatedwith
human settlements is found distributed in
varyingdegreesthroughoutall three fractions.
In summary,of the types of evidenceavail-
able for study at abandoned settlements,
physical and chemicalsoil changesinducedby
human occupation are amongthe most lasting
and potentially valuable.Especiallyimportant
to settlementsoil studiesarethose tests which
revealphosphatedepositions of humanorigin.
Recently, field and laboratorytechniqueshave
been developed specifically for the analysisof
phosphatein anthrosols.Througha quantitative
laboratorymethod called sequentialfractiona-
tion, human phosphate depositions can be
distinguishedfrom natural ones and types of
features and land use can be identified. It is
hoped that through the testing of selected
samplesfrom a varietyof culturalandtemporal
contexts, the mechanismsaffecting phosphate
accumulationsin soils at settlements can be
clarified and that the field and laboratory
applications of the new techniques will he
Acknowledgments. The direction and help of
Robert C. Eidt through all phases of the project are
gratefully acknowledged. In addition, I wish to thank
Clinton R. Edwards and Melvin L. Fowler for their
advice and encouragement, and the University of
Wisconsin-MilwaukeeGraduate School and the Depart-
ment of Geography for providing support.
1968 Phosphatuntersuchungen zur topo-
graphischen Lokalisation von Ortswustungen.
1931 Die Bodenanalyse im Dienst der
Archaologie. Zeitschrift fur Pflanzenerndhrung,
Diingung, und Bodenkunde 10:427-39.
Berenblum, O., and E. Chain
1938 An improved method for the colorimetric
determination of phosphate. Biochemical
Buehrer, T. F.
1950 Chemical study of the material from several
horizons of the Ventana Cave profile. In The
stratigraphy and archaeology of Ventana Cave,
Arizona, by Emil W. Haury and others, pp.
549-63. The University of Arizona Press,
Chang, S. C., and M. L. Jackson
1957 Fractionation of soil phosphorus. Soil
Comwall, I. W.
1958 Soils for the archaeologist. Phoenix House,
Cruxent, J. M.
1962 Phosphorus content of the Texas street
"hearths." American Antiquity 28:90-91.
Davidson, D. A.
1973 Particle size and phosphate analysis: evi-
dence for the evolution of a tell. Archaeometry
Dietz, Eugene F.
1957 Phosphorus accumulation in soil of an
Indian habitation site. American Antiquity 22:
252 AMERICAN ANTIQUITY [Vol. 42, No. 2, 1977]
Eddy, F. W., and H. E. Dregne
1964 Soil tests on alluvial and archaeological
deposits, Navajo Reservoir district. El Palacio
Eidt, R. C.
1973 A rapid chemical field test for archaeologi-
cal site surveying. American Antiquity 38:
Eidt, Robert C., and WilliamI. Woods
1974 Abandoned settlement analysis: theory and
practice. Field Test Associates, Milwaukee.
Gregg, Michael L.
1975 Test excavation at two sites in northwestern
Illinois. The Wisconsin Archeologist 56:
1940 Die siedlungsgeographische Phosphat-
methode. Die Naturwissenschaften 28:633-40.
1954 Die anthropogenen Bodenphosphate des
Hohenstaufen-Gipfels. Jahrbucher fur Statistik
und Landeskunde von Baden-Wiirttemberg 1:
Lutz, H. J.
1951 The concentration of certain chemical ele-
ments in the soils of Alaskan archaeological
sites. A merican Journal of Science 249:925-28.
Mattingly, S. E. G., and R. J. B. Williams
1962 A note on the chemical analysis of a soil
buried since Roman times. Journal of Soil
Murphy, J., and J. P. Riley
1962 A modified single solution method for the
determination of phosphate in natural waters.
Analytica ChimicaActa 27:31-36.
Solecki, Ralph S.
1951 Notes on soil analysis and archaeology.
American Antiquity 16:254-56.
Syers, J. K., G. W. Smillie, and J. D. H. Williams
1972 Calcium fluoride formation during extrac-
tion of calcareous soils with fluoride: I. implica-
tions to inorganic P fractionation schemes. Soil
Science Society of America Proceedings 36:
Woods, William I.
1975 The analysis of abandoned settlements by a
new phosphate field test method. The
ULTRASONIC DISAGGREGATION OF POTSHERDS
FOR MINERAL SEPARATION AND ANALYSIS
ALAN M. GAINES
JULIA L. HANDY
Weaklybound composite materialssuch as low-firedpottery, bricks,mortar,and induratedsoils can be
disaggregatedby ultrasoundwithno significantchemicalor physicalalterationof individualcomponentgrains.
The components may then be separatedby size, shape, density, magneticproperties, etc. This allows
mineralogical,bulk chemical,trace-element,thermoluminescence,or other analysesof individualseparatesas
wellasdeterminationof theirrelativeproportionsin thecomposite.
The pastfew decadeshaveseenanincreasing
application of sophisticatedtechniquesin the
analysis of archaeologicalmaterials.Complex
chemical and physical analyseshave provided
useful informationconcerningthe ages of arti-
facts and the sourcesof rawmaterialsand the
technologies involved in their manufacture.
However, valid interpretation of the data
produced by analyses of composite materials
(most pottery, brick,mortar,and stone imple-
ments) must involve knowledgeof the relative
contributions of the individual components.
Forexample,the trace-element"signature"of a
sherdof sand-temperedpotterywill dependnot
only uponthe clay(s)in the pastebut alsoupon
the diversemineralsin the temperingmaterial.
It is conceivablethat the trace-elementcontent
of a sherd may be largely determinedby the
chancepresence(or absence)of a singlegrainof
some minor component (such as zircon,
monazite, or sphene) in the sand, resultingin
the same pot. Therefore detailed studies of
analysesof each of the variouscomponentsas
well as a determinationof theirrelativepropor-
tions andtheirdistributionin the sample.
We report here a method for disaggregating
relativelyweakly bound composites (low-fired
pottery, bricks, mortar, indurated soils, etc.)