The quantitative analysis of soil phosphate
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  • 1. 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 . Accessed: 29/06/2011 14:06 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at . http://www.jstor.org/action/showPublisher?publisherCode=sam. . Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Society for American Archaeology is collaborating with JSTOR to digitize, preserve and extend access to American Antiquity. http://www.jstor.org
  • 2. 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 formandthe knappingtechniquesinvolved. 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. Nature 261:28-29. Carter,George F. 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 12(1):2-9. 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. THEQUANTITATIVEANALYSISOFSOILPHOSPHATE WILLIAMI. WOODS 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, nitrogen,carbon,phosphorus,andcertaintrace metals. Phosphoruscompoundsin the form of phosphatehave provedto be the most stablein their chemistry and location in a wide variety of soils. 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 time. It has become apparent that with certain exceptions, the field method is extremely worthwhile in site surveys (for example, see Gregg1975:184-87). Presentevidenceindicates
  • 3. REPORTS 249 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 structureswithinsettlements. 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 regionalcontextsmade. 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 agronomictechniquesdesignedfor testingavail- 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 routinelycarriedout. 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. Totalphosphatedeterminationsproducea com- 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 revealing. The techniqueis basedupon the differential solubility of the major phosphate forms in variousextractingsolutions(ChangandJackson 1957; Syerset al. 1972). Whenthese solutions are arranged in appropriate sequence, the procedurecanyield resultswhicharespecificas 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 Woods1974:79-103, 146-55). 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 influence. 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 conjunctionwith burials. The moderatelyhigh concentrationandfair-
  • 4. 250 AMERICAN ANTIQUITY [Vol. 42, No. 2, 1977] 1.0gAIRDRIEDSOILSAMPLE 40 ml 0 1 N NaOH/1 0 N NaCI 12 hr SHAKING/CENTRIFUGE SOLUTION A NaOH 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 PREVIOUS 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 phosphatedistributionandconcentrationin the fractions.Thoughexhibitingsomehumaninter- 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 phosphateconcentrationsrarelyeven approach
  • 5. REPORTS 251 Table 1. Inorganic Phosphate Fractionation Results NaOH & 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 activities. 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 phosphateformswithinsoilsof thiskind.When 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 expanded. 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. Apt, Peter 1968 Phosphatuntersuchungen zur topo- graphischen Lokalisation von Ortswustungen. GeographicaHelvetica 6:185-90. Arrhenius, 0. 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 Journal 32:295-98. 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, Tucson. Chang, S. C., and M. L. Jackson 1957 Fractionation of soil phosphorus. Soil Science 84:133-44. Comwall, I. W. 1958 Soils for the archaeologist. Phoenix House, London. 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 15:143-52. Dietz, Eugene F. 1957 Phosphorus accumulation in soil of an Indian habitation site. American Antiquity 22: 405-09.
  • 6. 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 71:5-21. Eidt, R. C. 1973 A rapid chemical field test for archaeologi- cal site surveying. American Antiquity 38: 206-10. 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: 174-200. Lorch, Walter 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: 367-75. 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 Science 13:254:58. 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: 20-25. Woods, William I. 1975 The analysis of abandoned settlements by a new phosphate field test method. The Chesopiean 13:1-45. 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 different"signatures"for adjacentsherdsfrom the same pot. Therefore detailed studies of heterogeneoussubstancesmay requireseparate 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.)