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col.lectedand sacrificed about tva yeers after the 3&lAal Mout. these aaimd~. The analyees ham not beencompl&$dbutTable Tvo
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G&ma Dose Rhes on The Gamma Dose Rates Three Feet Above Ground on Island of Rongelap Estimated From Relative Theoretical Ganmm Dose Rates, Decay Rates of ~SSiOn Products,_Jnergy of the Gamas, ind the Number of Gmmna Photons Per Msintegra-
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Applied Fisheries Laboratory uni: Isity of Washington Comments on SrgO in Land Crabs re.: Dr. Seymour's letter of The SrgO levels in land crabs can be expected to remain constant (excepting physical decay) over a period of years. This statement is based on the data resulting from repeated collections at Belle Island, Eniwetok, during a period of two years following Nectar test. The radioactivity in the carapace (exoskeleton) due to long lived isotopes remained approximately constant at a level of approximately 10,000 d/m/g wet throughout a period of 23 months during which collections were made. Radiochemical analysis of 15 samples taken at various times during the collecting period, and three samples taken 35 days before Nectar test demonstrated that virtually 100% of the long lived isotopes was Sr90 and its Ygo daughter. The land crabs being omnivorous can probably be considered an index of biologically available strontium. However, the ratio of the strontium to that in food items is not known. Judging from the meager data presently available the radiostrontium content of the crab skeleton is more than ten times that in land plants on a--wetweight basis and is more than three times that in soil on a dry weight basis. The data from the Belle Island collections indicates that turnover of strontium in the land crab skeleton is rapid. The
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comparatively high levels of SrgO in the carapace probably represent a condition of equilibrium with the available strontium rather than an accumulation over a long period of time. In muscle of land crabs collected at Belle Island in and November 1955, and analyzed in January and March l$,respectively, of the total activity. In contrast to the exoskeleton, muscle had a variable, though generally decreasing level of long lived isotopes throughout the post Nectar collecting period at Belle Island. Whether or not SrgO levels in the muscle were decreasing during this period is not known. Although there was a decrease from 90 d/m/g wet in a single specimen collected in February 1955 to 60 d/m/g wet in a specimen collected in November 1955, experience has shown that individual variation may account for such differences. Values of determinations of SrgO in muscle of land crabs from Kabelle Island, Rongelap Atoll, indicate that the Sr90 level is remaining constant. But here again individual variation is great; the value for duplicate determinations of muscle from a single coconut crab collected in January 1955 was 59fl.5 d/m/g wet and the average of three samples of hermit crab muscle taken in , It should be clearly understood that applies only to the land crabs and not to crabs have lower levels of total activity and contain little, if any, Sr90 (see for the above discussion marine crabs. Marine than do the land crabs
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RESULTSOF ANALYSES PERFCRMEDAT HASL life, laud plants,water and soil, and lagoonand oceanwater on or near selectedislandsin the.Marshallgroup. Some of the collectedsampleswere sent to HASL for fissionproduct analysis. In some casesportionsof specimenswere retainedat NRDL for interreceivedincludingthose selectedfor analysisis given in Table 1. The marine,water, and urine sampleswere receivedin good conditionbut many of the vegetationspecimenswere in a severestate of decay upm arrivalat HASL. Furthermore,some sampleswere receivedunsealedso that the contentshad leakedout and were on the outsideof their own and other containers. It was felt that this could be a sourceof cross contaminationin additionto the loss of the leakingsamples.(1) For this reason and becauseof limitedtime and manpower,only selectedsamples were subjectedto analysis. However,all of the marine and vegewet-ashedusing nitric acid, dilutedto known volumes,and stored
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in polyethylenecontainers.Concentrationsare based on the weight of the materialat the time it was receivedat HASL. Consequently,all radiochemicaland analyticalresultsare reported here in terms of d/m or grams,per gram of materialas received at HASL. Dr. H. Weiss has statedvia letter(*)that the wet weightsof the plant spectins were not recordedat the time of collection. He has proposedthat the resultsbe expressedin terms of d/m/kg of materialas receivedat NRDL. For determinationof totalbeta activity the solutionof wet-ashedmatertalwas transferred chet, evaporatedand dried under an infra-redlamp. Countswere convertedto disintegrat%onsby applyinga geometryfactorbased on & ' as a standard. used at HASL possible Under the wet ashingand platingconditions loss of volatilefissionproductssuch as outer and inner shellswere dry ashed at 506OC prior to dissoluvalues of activityvs. dry weight of the plated aliquotwere plottedand a smoothcurvefittedfor the points. Another curve (basedon extrapolationto zero mass) of activityratio (A/Ao)was drawn and used for determiningthe self-absorption
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The procedureoutlinedin NY&4617 was followedfor the by S. Tarrasusing a methodwhich to date has not been documented. It involvesthe coprecipitationof cesiumwith ammoniumalum to eliminatemixed fissionproductsas well as potassium,then a final ric yields of 95% are attainable. The sampleswere analyzedfor As a check on radiochemical purity,beta absorptionanalyses were carriedout by N. Hallden(9 on the Csl37 fractionsof two pooled urine samples(specimenscollectedat Utirik and Likiep), one water sample (HASL#3&7), and one soil (HASL#3462). In each case Csl37was positivelyidentifiedand therewas no evidenceof other interferingisotopes. The radioactivedecay of the $O.fractions of the urine samples hours. Within statistical was followedover a period of one hundred limitsconcurrencewith the theoretical error term accompanyingeach dard deviationdue to the error in counting. The only available interlaboratorycross-checkdata are given in Table 7. These
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resultswere obtainedfrom Dr. &. Cohn by phone on April 24, 1956. discrepancyin the beta count probablylies in the for purposesof comparison,the HASL allowsthe best approximationof the ducts among the availablelong-lived this case and resultswere also standardieed As an aid in evaluatingthese data, Figure 1 and Table
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Letter of May 9, 19% from Dr. H. Weiss to EdwardRardy. the Wet Ashing TechniqueUsed at HASL on RutheniumVolatiliza-
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bat and Milk Meat and Milk 3447 558 Rongelap Arrowroot Entire 4-a-56 lost 3456 856 Oegen Arrowroot Entire 4-a-56 30024.1 3492 726 Eniwetak Arrowroot Entire 4-U-56 6722.1 3505 674 Sifo Arrowroot Entire h-14-56 5922.2 3519 756 Utirik Arrowroot Entire 4-&56 26tl.h 3541 807 Likiep Arrowroot Entire 4-14-56 7.31.1 Results of Analyses Performedat HASL + Weight as receivedat HASL
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ERDLB Sapling Location D,pth Total Activity d/s/pan* Results of Analyses?erforznedat HASL + Fleightas received at AASL.
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Well or Cistern Results of Analyses Performedat RASL Total Activity Total Activity
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(Snail Solutions Prepared at HRDL from Specimens Collected on Gejen Island) NOTE : Vet weights furnished by XRDL from S. Cohn on April 24, 1956.
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Rongelap Eniaetok Kabelle oejen Eniwetak sir0 Utirik Lildep + Weight of material as receivedat BASL
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