Analysis of Small Mammal - IAEA

Analysis of Small Mammal Populations inhabiting the Environs of a Low-Level Radioactive Waste Pond*

K. A. Gano

March 1979

Prepared for the U.S. Department of Energy under Contract No. EY-76-C-06-1830

*This research was performed as part of Rockwell Hanford Operations' Site Characterization Activity, Long-Term Management of Low-Level Waste Program, coordinated by Keith Price.

Pacific Northwest Laboratory Richland, Washington 99352

ACKNOWLEDGMENTS

Th is s tudy was supported by t h e Rockwell Hanford Operat ions Long-Term Management o f Low-Level Waste Program under Contracts EY-77-C-06-2130 and EY-76-C-06-1830.

I n developing our concepts, we have drawn ex tens i ve l y on t h e data base, design paradigms and pro fess iona l experience o f s t a f f associated w i t h research programs funded by the O f f i c e o f Hea l th and Environmental Research o f t h e Department o f Energy. Thanks a r e extended t o t h e people who p a r t i c i p a t e d i n and con t r i bu ted t o t h i s study. Rockwell s c i e n t i s t D. Paine and B a t t e l l e s c i e n t i s t s W. H. Rickard, L. E. Rogers, R. G. Schreckhise, G. W. Endres and L. L. Cadwell gave h e l p f u l suggest ions and adv ice on data i n t e r p r e t a t i o n . C. A. Lee, M. A. Rumble and W. D. S te igers ass i s ted i n smal l mammal t r app ing and data c o l l e c t i o n . Dosimeter ana l ys i s was performed by F. N. Eichner.

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T h i s s tudy was designed t o determine t h e k inds o f smal l mammals l i v i n g ad jacen t t o 216-U-10 Pond, t h e r a d i a t i o n exposures these mice rece ived, and t h e l e v e l and type of r a d i o n u c l i d e s a s s i m i l a t e d w h i l e l i v i n g nex t t o t h i s pond and t h e 216-2-19 D i t ch . T h i s i n fo rn i a t i on w i l l u l t i m a t e l y be used t o es t ima te b i o - l o g i c t r a n s p o r t o f r ad ionuc l i des i n t h e pond area.

Four species of mice were t rapped and i nc l uded t h e Great Bas in pocket mouse (~erogmthus parvus ) , deer mouse (~eromjscus maniculatus ) , house mouse us musculus) , and t h e western ha rves t mouse (~eithrodontomys megalotis).

Animals were c o l l e c t e d throughout t h e s tudy and composite t i s s u e samples were analyzed by gamma spect rometry . Also, an a n a l y s i s f o r 2 3 8 P ~ , 2 3 9 , 2 4 0 P ~ and 241Am was performed. The most abundant garrlliia e m i t t e r was 137Cs w i t h t h e h i ghes t l e v e l s o c c u r r i n g a t t h r e e t r a p p i n g l o c a t i o n s : one near t he 216-2-19 D i t c h and two l o c a t i o n s ad jacen t t o t h e pond. House mice captured near t h e 216-2-1 9 D i t c h showed t h e h i ghes t 1 eve ls w i t h one g a s t r o i n t e s t i n a l (GI ) t r a c t sample hav ing 1600 pCi 137Cs/g d r y weight .

Four t i s s u e types f rom r e s i d e n t mice were analyzed f o r Pu and Am concen- t r a t i o n s . The t i s s u e s analyzed were f u r - s k i n , l i v e r , lung, and muscle-bone. The h ighes t concen t ra t i on de tec ted was 2.03 pCi 2 3 9 , 2 4 0 P ~ / g d r y we igh t i n a f u r - s k i n sample from house mice captured on t h e meadow t r a n s e c t near t h e pond.

Resu l ts f rom rad iochemica l analyses o f mouse t i s s u e s showed t h a t pocket mice have t h e lowes t concen t ra t ions of r ad ionuc l i des . They were a l s o l e s s f r e - q u e n t l y t rapped on t h e two r i p a r i a n t r a n s e c t s near t h e pond. Th is may be a t t r i b u t e d t o food and h a b i t a t preference. Pocket m ice g e n e r a l l y p re fe r t h e Artemisia tridentata-Bromus tectorwn vege ta t i on t ype t o r i p a r i an habi t a t s such as t h e pond and d i t ches .

Another p a r t o f t h i s s tudy i nvo l ved dosimeters imp lan ted i n r e s i d e n t mice t o determine gamma exposure. Analyses revea led t h a t mice l i v i n g i n t h e meadow t r a n s e c t ad jacen t t o t h e pond r e c e i v e t h e h i ghes t exposure. Again, house mice had t h e h ighes t , w i t h an average 54.9 R/yr.

Dosimeters were p laced i n t h e s o i 1 a long t h e t r a p p i n g t r a n s e c t s t o measure gamma and thermal neu t ron exposure r a t e s a t each dm o f s o i l t o a depth o f 5 dm. Th is s h ~ w e d t h e s t r a t i f i c a t i o n o f exposure r a t e s i n a 5-dm s o i l p r o f i l e . The t o p decimeter o f s o i l had t h e h i ghes t exposure r a t e w i t h a mean o f 75 R/yr i n t h e meadow. Neutron dose i n t h e s o i l was a l s o h i g h e s t near t h e su r f ace w i t h 37 mrad/yr average i n t h e meadow.

CONTENTS

ACKNOWLEDGMENTS

SUMMARY . L I S T OF FIGURES

L I S T OF TABLES

I IVTRODUCT IOIV . S I T E DESCRIPTION .

METHODS . RESEARCH AND ANALYSIS .

SPECIES COMPOSITION AND RELAT IVE ABUNDANCE . RADIOCHEMICAL ANALYSES .

Gamma-Emi t t i n g N u c l i d e s . P l u t o n i u m A n a l y s i s . F o o d H a b i t s

GAMMA EXPOSURES TO SMALL MAMMALS . EDAPHIC EXPOSURE RATES .

N e u t r o n E x p o s u r e i n t h e S o i l . CONCLUSIONS . LITERATURE C I T E D . APPENDIX A

APPENDIX B

APPENDIX C

APPENDIX D

APPENDIX E

LIST OF FIGURES

Map o f Hanford Area Showing U-Pond . 2

U-Pond Small Mammal Transects 3

Anesthet ized Pocket Mouse Being Imp1 anted w i t h Dosimeter Packet . 6

Dowel Showing Surface Locat ion o f Dosimeters Used t o Measure S o i l Exposure . 8

Concentrat ions o f Plutonium and Americium i n Composite House Mouse Samples . 12

Concentrat ions o f Pl utonium and Amer ic i l~m i n Composite Pocket Mouse Samples . 12

Concentrat ions o f Pl utonium and Americium inCompos i t eDeerMouseSamp les . 13

Concentrat ions o f Pl utonium and Americium i n Composite Harvest Mouse Samples . 13

Gamma Exposure t o Mice L i v i n g Along U-Pond and Contro l Transects . 16

Gamma Exposure t o S o i l Along U-Pond Transects 17

Cross Sec t ion o f Z-19 D i t c h Showing Locat ion o f S o i l Dosimeter Probes . 19

v i i i

LIST OF TABLES

Tota l Number of Animals Captured and Percentage o f Each Species on U-Pond and Contro l Transects . U-Pond Plutonium Ana lys is on Whole Mice

Mean Gamma Exposures t o U-Pond Mice i n R/yr . Mean Gamma Exposure t o S o i l on U-Pond Transects i n R/yr

Mean Neutron Exposure t o S o i l on U-Pond i n mrad/yr

Composite Sample Using L i k e Tissues from Two o r More Animals o f Same Species, pCi 137Cs/g Dry

A . l . l Fur-Skin Samples . A. 1.2 L i v e r Samples

A. 1 .3 Kidney Samples . A.1.4 Lung Samples . A.1.5 G I T rac t Samples . A. 1.6 Muscle-Bone Samples . Composite Samples Other than 1 3 7 ~ s , pCi/g Dry

A.2.1 Sampling Per iod 9 - 1 0 A p r i l '75 . A.2.2 Sampling Per iod 6-7 May '75 . A.2.3 Sampling Per iod 23-24 October '75

U-Pond Samples Col 1 ected Dur ing 1976-77 and Analyzed as I n d i v i d u a l Animals, pCi/g 137Cs/g Dry . U-Pond Samples C o l l ected During 1976-77 and Analyzed as I n d i v i d ~ a l Animals, pCi/g Dry ( Samples Other than 137Cs ) . I s o t o p i c Plutonium and Americium Analys is o f U-Pond Mice Using Composite Samples

B. 1.1 Concentrat ions o f 2 3 8 P ~ / g Dry . B. 1 .2 Concentrat ions o f 2 3 9 p ~ / g Dry . B.1.3 C o n c e n t r a t i o n ~ o f ~ ~ ~ A m / g D r y . Mean Gamma Exposure t o Small Mammals a t U-Pond i n mR/wk

Gamma Exposure t o U-Pond Mammals i n mR/wk . Gamma Exposure i n S o i l Along U-Pond Transects i n Roentgens Per Year .

D.2 Neutron Exposure i n S o i l Along U-Pond Transects i n mrads Per Year . . D-3

D.3 Mean Gamma Exposure t o S o i l on U-Pond Transects i n Roentgens Per Year . . D-4

E. l Tota l Number o f I n d i v i d u a l Animals Captured Each Month . E-1

E.2 Average Number o f Animals Captured on U-Pond Transects Per Trap Session . . E-3

INTRODUCTION

In fo rmat ion concerning species composit ion, concent ra t ion o f rad ionuc l ides taken up by t h e var ious species, and ex te rna l doses o f gamma r a d i a t i o n i s essen- t i a l i n determin ing t h e environmental impact o f waste management areas on small mammal populat ions. Small mammals a re p o t e n t i a l vectors i n t he t r a n s p o r t o f rad ionuc l ides away from waste management areas because they prov ide a food base fo r many l a r g e r , more mobi le secondary consumers such as snakes, rap tors , bad- gers, racoons, skunks, and coyotes. For t h i s reason i t i s important t o de ter - mine the types and t h e q u a n t i t i e s o f nuc l ides being concentrated by mice l i v i n g on waste management areas. Also o f concern i s t he exposure r a t e t o t he b i o t a on these areas (Energy Research and Development Admin is t ra t ion , 1975).

This s tudy was designed t o gather i n fo rma t i on on small mammals l i v i n g adja- cen t t o 216-U-10 Pond. Rad ia t ion exposures t o the mice were i nves t i ga ted a long w i t h t he l e v e l and type o f rad ionuc l ides being ass imi la ted . This i n fo rma t i on w i l l u l t i m a t e l y be used t o est imate b i o l o g i c t r a n s p o r t o f rad ionuc l ides i n t h e pond area.

To accompl i s h t h i s o b j e c t i v e the f o l l o w i n g approach was used:

1. Species composit ion was i n v e s t i g a t e d f o r mice l i v i n g near 216-U-10 (U-Pond), a l i q u i d waste d isposal s i t e .

2. Tissue samples taken from mice l i v i n g i n t he v i c i n i t y o f 216-U-10 were analyzed f o r rad ionuc l i de content t o determine concentrat ions.

3 . Dosimeters were implanted i n mice l i v i n g i n t he v i c i n i t y o f t he t rapp ing t ransec ts on the study areas t o p rov ide a means f o r determin ing ex te rna l gamma exposures.

4. To e s t a b l i s h exposure d i s t r i b u t i o n i n a 5-dm s o i l p r o f i l e , dosimeters were bu r i ed a t 1 dm increments a long the t r a n s e c t l i n e s .

This r e p o r t descr ibes r e s u l t s o f these analyses. Appendix A conta ins r e s u l t s f rom t i s s u e ana l ys i s f o r gamna emi t t e rs , and Appendix B prov ides summaries of t i s s u e ana l ys i s f o r p lu tonium and americium-241. Appendix C inc ludes exposure ra tes of gamma r a d i a t i o n t o mice l i v i n g near the var ious t ransec ts . Appendix D prov ides in fo rmat ion on the s t r a t i f i c a t i o n o f gamma and thermal neutron r a d i a t i o n doses i n a 5-dm s o i l p r o f i l e a long each t ransec t and Appendix E conta ins i n fo rma t i on on t rapp ing r e s u l t s .

SITE DESCRIPTION

The study areas are l oca ted on the Department o f Energy's Hanford S i t e i n Benton County, sou thcent ra l Washington (F igure 1) . These areas c o n s i s t o f t he U-Pond study s i t e , s p e c i f i c a l l y 216-U-10 (F igure 2 ) , l oca ted w i t h i n t he con- f i n e s o f t h e 200 West per imeter fence, a c o n t r o l p l o t near U-Pond, and an addi - t i o n a l c o n t r o l s i t e on the A r i d Lands Ecology (ALE) Reserve a t Ratt lesnake Springs, es tab l ished t o correspond w i t h t he r i p a r i a n vegeta t ion a t U-Pond.

FIGURE 1. Map o f Hanford Area Showing U-Pond

U-Pond was e s t a b l i s h e d i n 1944 i n a sha l low depress ion i n t he 200 West Area o f t he Hanford S i t e . I t s f u n c t i o n was t o r e c e i v e l ow- l eve l r a d i o a c t i v e wastes, p r i m a r i l y c o o l i n g water, and laundry waste water. The pond p r e s e n t l y rece ives water f rom t h r e e major sources: a p lu ton ium process ing p l a n t v i a 216-2-19 D i t ch , a laundry where p r o t e c t i v e c l o t h i n g i s washed ( v i a 216-U-14 D i t ch ) , and an evapora to r c r y s t a l 1 i z e r p l a n t which reduces 1 i q u i d rad-wastes t o s a l t cakes v i a 216-U-14 D i t ch .

U-Pond i s t h e o l d e s t 1 i q u i d waste d isposa l s i t e on t h e Hanford S i t e . Since i t s o r i g i n , a d i ve rse r i p a r i a n vege ta t ion has developed, c r e a t i n g an a t t r a c t i v e h a b i t a t f o r many animals o therw ise n o t common t o t h i s a r i d env i ron- ment ( F i t z n e r and Rickard, 1975).

TRAPS

x SOIL TLD LOCATIONS

U-POFID FOREST TRANSECT

FIGURE 2. ti-Pond Small Mammal Transects

METHODS

Trap l i n e s were e s t a b l i s h e d a t t h e U-Pond s tudy s i t e us ing Sherman l i v e t r aps . Four t r a n s e c t s were s e t up near t h e pond. These t r ansec t s each con- t a i n e d 10 t r aps . There were two d i f f e r e n t h a b i t a t types represented. A t r a p l i n e a long t h e Z-19 D i t c h and one a long t h e U-14 D i t c h represented a d e s e r t h a b i t a t o f sagebrush-cheatgrass w i t h access t o f r e e water. The r i p a r i a n habi - t a t ad jacen t t o t h e pond was represented by two t ransec ts , one i n t h e smal l d e l t a r e g i o n between t h e two d i t c h e s (~eadow t r a n s e c t ) , and one near t h e south end o f t h e pond i n a wooded area, t h e Fo res t t r a n s e c t (F i gu re 2 ) .

Two c o n t r o l t r a n s e c t s were l o c a t e d i n noncontaminated areas away f rom the pond. One c o n t r o l t r a n s e c t was l o c a t e d i n s i d e t h e 200 West per-inieter fence i n a sagebrush-cheatgrass area approx imate ly 114 m i l e f rom U-Pond. It con ta ined two l i n e s o f 10 t r a p s each f o r a t o t a l o f 20 t r aps . The second c o n t r o l t r a n - s e c t on t h e A r i d Lands Ecology Reserve a t Rat t lesnake Spr ings con ta ined 40 t r a p s . S i x teen t r a p p i n g sessions were conducted a t t h e U-Pond s tudy s i t e and c o n t r o l t r ansec t s . Trapping commenced i n A p r i l 1975 and ended i n J u l y 1977.

The f i r s t phase o f t h e s tudy i n v e s t i g a t e d r a d i o n u c l i d e concent ra t ions i n t h e smal l mammals l i v i n g near t h e pond. The t r a p l i n e s were operated d u r i n g A p r i l , May and October 1975, and t h e mice submi t ted f o r rad iochemica l ana l ys i s . A f t e r each t r a p sess ion t h e animals were brought i n t o t h e l a b and separated by species and t r ansec t . They were then d i ssec ted i n t o var ious t i s s u e s w i t h each l i k e sample o f same species and l o c a t i o n combined t o make composite samples. For example, a l l t h e l i v e r s f rom pocket mice captured on t h e Z t r a n s e c t d u r i n g one t r a p sess ion were combined t o make one sample.

Dur ing t h e f i r s t sample sess ion i n A p r i l 1975, t h e composite sarr~ples con- s i s t e d o f muscle-bone, f u r - s k i n , head, f e e t - t a i l , lung, l i v e r , k idney, t es tes , ovary, and g a s t r o i n t e s t i n a l t r a c t . Dur ing t he sample per iods o f May and Octo- b e r 1975, f o u r o f t h e sample types were d iscon t inued . The "head" and t h e " f e e t - t a i l " samples were n o t used because i n bo th cases t he re were inseparab le i n t e r n a l and e x t e r n a l s t r u c t u r e s , e.g., bone, ~ i iusc le and f u r - s k i n on t h e " f e e t - t a i l " sample, making i t imposs ib le t o determine t h e l o c a t i o n o f de tec tab le rad ionuc l i des . The t e s t e s and ova ry samples were a l s o d i scon t i nued due t o i n s u f f i c i e n t t i s s u e mass t o o b t a i n va l i d coun t ing r e s u l t s . Therefore, t he samples used i n t h e f o l l o w i n g two sample sessions were f u r - s k i n , l i v e r , lung, k idney, g a s t r o i n t e s t i n a l t r a c t , and muscle-bone ( t h e remain ing carcass).

The samples were oven-dr ied a t 50°C f o r 48 h r and then analyzed by gamma spectrometry. Samples f rom each t r a n s e c t w i t h s i g n i f i c a n t 137Cs concent ra t ions above c o n t r o l va lues were se lec ted and analyzed f o r p lu ton ium concent ra t ions . Samples f rom May and October sessions were analyzed f o r s p e c i f i c p lu ton ium and americium, i .e., 2 3 8 P ~ , 2 3 9 - 2 4 0 ~ ~ , and 241Am by LFE Environmental Analy- s i s Labora to r ies , Richmond, C a l i f o r n i a .

T issue samples were taken throughout t h e s tudy p e r i ~ d f o r rad iochemica l a n a l y s i s and i nc l uded whole body samples f o r p lu ton ium ana l ys i s . Two o t h e r

Fol lowing the opera t ion the mice were returned t o t h e i r respect ive po in ts o f capture and released. Approximately 1 month l a t e r the t r a p l i n e s were operated again and the recovered TLDs exchanged. Concurrent ly, newly captured mice were -i rr~pl anted w i t h TLDs.

The TLD 700s used i n t h i s study were c a l i b r a t e d f o r exposure dose i n a i r w i t h a 226Ra source. Therefore, a l l exposure data from TLD 700s are repor ted i n roentgens (R). T o t a l l y accurate measurements o f absorbed doses i n U-Pond mice are extremely d i f f i c u l t t o i n t e r p o l a t e . Ca lcu la t ions necessary t o de te r - mine absorbed dose from known exposed dose employ a conversion f a c t o r which uses the e f f e c t i v e atomic number o f t he i r r a d i a t e d medium along w i t h the ener- g ies o f t h e i o n i z i n g rad ia t i ons . The f o l l o w i n g expression i s used f o r t h i s conversion when the photon energy and mass absorpt ion c o e f f i c i e n t o f the exposed medium a re known (Arena, 1971 ).

'/ Of R (exposed dose) Rads (absorbed dose) = [0.869 EIp of air

where t h e p /p values are the mass absorpt ion c o e f f i c i e n t s f o r t he absorbing ma te r ia l and a i r . The mass absorpt ion c o e f f i c i e n t s are func t ions o f t he energy o f t h e i n c i d e n t photons and the atomic number o f t he absorbing medium.

I f one assumes t h a t t he energies o f t he i n c i d e n t photons a t U-Pond were equal t o 0.1 MeV, and o n l y s o f t t i ssues o f t he mice were considered then the mass absorpt ion c o e f f i c i e n t s are 0.0252 cm2/g f o r t he ma te r ia l and 0.0231 cm2/g f o r a i r (NBS Handbook 85, 1964). The absorbed dose would then be equal t o

0 0252 cm2/ rads = 10.869 -1 R = (0.95) R

Dosimeters were a l so placed i n the s o i l a long t h e t ransec t l i n e s . There were f i v e l o c a t i o n s on each t ransec t . A t each l oca t i on , aluminum tubing, 5.5 dm long by 1.9 cm i n diameter and a w a l l th ickness o f approximately 1 mm, was d r i v e n i n t o t h e s o i l . Dosimeters were attached t o a wooden dowel a t 1-dm i n t e r v a l s and t h e dowel placed i n s i d e the aluminum tub ing (F igure 4). The dosimeter l o c a t i o n s s t a r t e d a t t h e s o i l sur face and went t o a depth o f 5 dm.# Along w i t h TLD 700s, which are p r i m a r i l y f o r de tec t i ng gamma r a d i a t i o n , TLD 600s were a l s o used a t each depth. The TLD 600 i s capable o f de tec t i ng gamma and thermal neutron r a d i a t i o n and was employed t o check f o r neutron r a d i a t i o n i n the s o i l . Detectable neutron r a d i a t i o n would i n d i c a t e the presence o f t rans- u ran i c elements which undergo spontaneous f i s s i o n .

The response of TLD 600s t o thermal neutron exposure i s r e l a t e d through t h e c a l i b r a t i o n t o t h e response o f t i s s u e i f t i s s u e were present. Therefore, a l l thermal neutron exposures a re repor ted i n mrads.

RESEARCH AND ANALYSIS

The t r a p p i n g e f f o r t had f o u r main o b j e c t i v e s . The f i r s t was t o determine species composi t ion o f t h e smal l mammals 1 i v i n g i n t h e v i c i n i t y o f U-Pond and t h e two c o n t r i b u t i n g d i t ches ; t h e second was t o q u a n t i t a t i v e l y measure t h e uptake o f nuc l i des , and t h e t h i r d was t o determine t h e gamma exposure t o smal l mammals i n h a b i t i n g t h e r a d i a t i o n zones ad jacen t t o t h e pond. The f o u r t h p a r t o f t h i s s tudy enabled edaphic exposure r a t e s t o be checked by p l a c i n g dosimeters a t c e r t a i n l e v e l s i n t h e s o i l . The f o l l o w i n g t e x t i n c l udes t h e f i e l d work and corresponding analyses.

SPECIES COMPOSITION AND RELATIVE ABUNDANCE

There were f o u r spec ies o f mice t rapped a t t h e U-Pond s i t e . They i nc l uded t h e Great Basin pocket mouse, Perognuthus parvus, deer mouse, Peromyscus mani- cuZatus , house mouse, Mus muscuZus, and t h e western ha rves t mouse, Rei throdon- tomys megaZotis .

The r e l a t i v e abundance o f each spec ies v a r i e d accord ing t o t h e h a b i t a t o f each t r a n s e c t . The vege ta t i on on t h e U-Pond c o n t r o l t r a n s e c t i s desc r ibed as sagebrush-cheatgrasslsandberg bluegrass t ype (Daubenmire, 1970; C l i ne , e t a l . , 1975). The most f r e q u e n t l y t rapped smal l mammal on t h i s t r a n s e c t was t h e pocket mouse w i t h 43 i n d i v i d u a l animals and second was t h e deer mouse w i t h 28 i n d i v i d u a l s (Table 1 ) . The t r ansec t s a long U- and Z-Ditches appear t o have vege ta t i on s i m i l a r t o t h e c o n t r o l t r a n s e c t w i t h t h e excep t ion o f nearby f r e e water and a ve r y 1- in i i ted and narrow r i p a r i a n zone. The major smal l mammal spec ies t rapped a long these t r a n s e c t s was t h e pocket mouse compr is ing 82% o f t h e i n d i v i d u a l s cap tu red a t U-Di tch and 69% a t Z-Di tch (Appendix E-1). Deer mice comprised t h e m a j o r i t y o f i n d i v i d u a l s captured i n t h e r i p a r i a n vege ta t i on o f t h e Meadow and Fores t t r a n s e c t s w i t h 37% and 46% r e s p e c t i v e l y . Species composi t ion was most d i v e r s e a t these two t r a n s e c t s w i t h a l l f o u r spec ies represented i n bo th (Table 1 ) .

The c o n t r o l t r a n s e c t l o c a t e d a t Ra t t lesnake Spr ings was es tab l i shed t o correspond w i t h t h e r i p a r i a n vege ta t i on t r a n s e c t s a t U-Pond. I t a l s o served as an added c o n t r o l f o r deer mice t o supplement da ta c o l l e c t e d on t h e c o n t r o l t r a n s e c t near U-Pond. The t r a p p i n g e f f o r t a t Ra t t lesnake Spr ings y i e l d e d 36 deer mice, making i t an e f f e c t i v e c o n t r o l f o r t h i s species.

TABLE 1. To ta l Number o f Animals Captured and Percentage o f Each Species on U-Pond and Cont ro l Transects

R.S. U-Pond Control ( a ) Control Z-Di tch Meadow U-Ditch Forest

n % n % n % n % n % n %

Pocket Mouse 43 61 45 69 17 23 51 82 6 10

Deer Mouse 36 97 28 39 19 29 28 37 9 15 27 46

House Mouse 1 3 1 2 26 35 2 3 21 36

Harvest Mouse 4 5 5 8

( a ) Ratt lesnake Springs Control n Number o f ind iv idua ls caught % Percent o f i n d i v i d u a l s caught on each t ransect

RADIOCHEMICAL ANALYSES

Radiochemical ana lyses were conducted f o r bo th gamma-emitting n u c l i d e s and p l u t o n i um.

Gamma-Emittina Nuc l ides

Composite samples r ep resen t i ng s i x t i s s u e types were analyzed f o r gamma- emi t t i n g nuc l i des . The t i s s u e s used were f u r - s k i n , 1 i v e r , k idney, 1 ung, gas t ro - i n t e s t i n a l t r a c t , and muscle-bone. Samples f rom each o f t h e t r a n s e c t s were represented d u r i n g t h e t h r e e sampl ing per iods .

The most abundant gamma e m i t t e r de tec ted f rom t h e U-Pond samples was 137Cs (Appendix A). The gamma scan i n d i c a t e d t h a t t h e n e x t most abundant n u c l i d e i n t h e samples was lo6Ru. However, t h i s n u c l i d e was represen ted i n o n l y one o u t o f t h r e e sampl ing sess ions. The May 1975 sampl ing sess ion showed lo6Ru w i t h an average o f 220 pC i /g d ry .

The h i g h e s t con ten t o f 137Cs was found i n a house mouse G I t r a c t composi te and con ta ined 1600 + 82 pC i /g d ry . Th i s sample came f rom t h e Z-D i tch t r a n s e c t . The rema in ing f i v e t i s s u e types f rom t h i s spec ies on t h i s t r a n s e c t a l s o showed h i g h values, w i t h t h e l owes t be ing 470 pC i /g d ry . Next i n o r d e r f rom t h e h i gh - e s t t o l owes t were t h e western ha rves t mouse, t h e deer mouse, and t h e Great Bas in pocke t mouse. The ha rves t mouse was represen ted i n t h e samples o r l l y tw i ce , once i n t h e Meadow and once i n t h e Fo res t t r a n s e c t . The 137Cs l e v e l s , f o r these samples, however, compared q u i t e c l o s e l y w i t h those o f t h e house mice f rom these t r a n s e c t s and sampl ing sess ions (Appendix A-1 th rough A-6).

The deer mice were t h e most comp le te ly represented spec ies and occur red on a l l t r a n s e c t s . On t h r e e o f t h e t r ansec t s , t h e Z-Ditch, Meadow, and t h e Fores t , deer mice were c o l l e c t e d d u r i n g each o f t h e sampl ing sessions. Upon comparing t h e t h r e e sess ions, r e s u l t s f rom t h e October sess ion i n most cases appears t o have h i g h e r concen t ra t i ons than t h e o t h e r two sess ions f o r t h i s mouse. Th i s suggested t r e n d can e s p e c i a l l y be seen i n t h e muscle-bone sample f o r deer mice. The r e p l i c a t i o n o f t h i s t r e n d i n o t h e r t i s s u e samples o f deer mice co r robo ra tes t h i s suggest ion. A f f i r ~ i i a t i o n o f t h i s t r e n d may prove t o be very - important as an a i d t o m o n i t o r i n g t h e uptake o f r a d i o n u c l i d e s by deer mice; however, a d d i t i o n a l work on t h e seasonal v a r i a t i o n s o f n u c l i d e uptake by deer mice i s needed t o con- f i r m t h i s p o s s i b l e t r e n d .

The pocke t mouse samples, i n c o n t r a s t , show ve ry l i t t l e a c t i v i t y f rom t h e t h r e e t r a n s e c t s t h e y represented i n t h i s sar r~p l ing scheme. These t r a n s e c t s were t h e c o n t r o l , Z -D i tch and U-Ditch, a l l o f which con ta ined s i m i l a r l e v e l s o f r a d i o c e s i urn.

I n a d i f f e r e n t a n a l y s i s , mice were randomly taken th roughou t t h e y e a r and analyzed as i n d i v i d u a l animals. The samples were d i v i d e d i n t o two t i s s u e types : 1 ) h ide, f e e t and t a i l , and 2 ) remain ing carcass. I n t h i s ana l ys i s , l e v e l s o f

1 3 7 ~ s f o r deer mice c l o s e l y resembled t h e f i g u r e s f rom t h e composite samples. The l o c a t i o n s y i e l d i n g deer mouse samples f o r t h i s a n a l y s i s were again t h e Z-Ditch, Meadow, and Fores t t r ansec t s . A l though pocket mice were n o t captured d u r i n g t h e f i r s t t h r e e sampl ing sessions on t h e Meadow and Fores t t r ansec t s , t hey were represented on these t r a n s e c t s i n t h i s sampling scheme. Th is t ime t h e q u a n t i t y of cesium de tec ted i n pocket mice c l o s e l y resembled t h a t o f t h e deer mice from t h e same t r ansec t s . Two pocket mice f rom t h e Meadow had l e v e l s exceeding t h a t o f t h e deer mice rang ing from 138 t o 332 pCi/g d r y as opposed t o 8.5 t o 265 pCi/g d r y (Appendix A-13).

The gamma scan data f rom these two sampling schemes show t h e Fleadow and ' . t h e Fores t t r a n s e c t s as t h e areas w i t h t h e h i ghes t l e v e l s o f rad ioces ium uptake

by t h e smal l mammals sampled. Next a re t h e d i t c h e s which a re represented by deer mice, house mice, and ha rves t mice. A c t i v i t y l e v e l s i n pocket mouse t i s - sues taken from the d i t c h e s a re n o t s i g n i f i c a n t l y d i f f e r e n t f rom those on t h e c o n t r o l t r ansec t . The s i m i l a r i t y o f t h e r e s u l t s f rom i n d i v i d u a l samples and t h e composites i n d i c a t e s t h a t combining o f 1-ike t i s s u e s probably d i d n o t obscure any h i g h values o f i n d i v i d u a l t i s s u e .

P lu ton ium Ana lys is

Four composite sample types were used f o r an i s o t o p i c p lu ton ium a n a l y s i s . They were f u r - s k i n , l i v e r , lung, and muscle-bone. The sample qroups used were se lec ted f rom t h e gamma scan r e s u l t s as t h e ones c o n t a i n i n g l 3 Cs a c t i v i t y . Also, an e f f o r t was made t o represen t a l l t r a n s e c t s a t l e a s t once.

Resul ts f rom t h e analyses i n d i c a t e d t h a t t h e amount o f p lu ton ium be ing taken up by smal l mammals was ve ry low. F igures 5a, 5b, 5c, and 5d show con- c e n t r a t i o n s f o r t h e f o u r species trapped. The h ighes t concen t ra t ions came f rom house mice l i v i n g i n t h e Meadow area and a long t h e Z-19 D i t c h (F igu re 5a). A composite f u r - s k i n sample f rom s i x house mice l i v i n g i n t h e Meadow y i e l d e d t h e h i ghes t va lue w i t h 2.03 pCi 2 3 9 - 2 4 0 P ~ / g d ry . Samples rep resen t i ng t h e o t h e r t h ree species i n t h i s ana l ys i s showed ve ry low values f o r p lu ton ium and amer ic iu~ i i o f < 0.5 pCi /g d ry . I n another a n a l y s i s f o r p lu ton ium, whole mice were analyzed-using deer mice from Z-19 D i t c h and house mice f rom t h e Meadow. I n t h i s a n a l y s i s t h e samples were t e s t e d f o r 2 3 8 P ~ and 2 3 9 + 2 4 0 P ~ . The r e s u l t s f o r 2 3 8 P ~ showed l e v e l s ve ry near background bu t f o r 2 3 9 + 2 4 0 P ~ t he deer mice f rom Z-19 e x h i b i t e d l e v e l s t h a t appeared s l i g h t l y above t he c o n t r o l values which average 0.98 pC i /g d r y (Table 2 ) .

The da ta f rom these analyses i n d i c a t e t h a t o f t h e f o u r species o f mice tes ted , t h e house mouse, t h e deer mouse, and t h e harves t mouse have t h e g rea t - e s t o p p o r t u n i t y f o r uptake o f r ad ionuc l i des a t t h e U-Pond s i t e .

Food Hab i ts

The most probable exp lana t i on f o r t h e h i g h e r concen t ra t ions o f t h e above t h ree species may be r e l a t e d t o t h e i r food h a b i t s and environmental o r h a b i t a t preference. The omnivorous deer mouse i s an o p p o r t u n i s t i c feeder t a k i n g advan- tage o f whatever food i s a v a i l a b l e (W- i l l ianis, 1959; Flake, 1973; Kritzman, 1974;

H O U S E M I

FUR-SKI

k Z M F C ;; Z M F C d' Z M F

0.8 - LUNG

>- o h - 2 - Z - D I T C H

E M -MEADOW r=" 0.4 - F - FOREST u, C - CONTROL

0.2 -

O'O -*

MUSCLE-BONE

FIGURE 5a. Concentrat ions of Plutonium and Americium i n Composite House Mouse Samples

P O C K E T M I C E

0.8 1 FUR-SKIN

> n E P 0.4 .- U - U-DITCH 2 Z - 2-DITCH

0.2 C - CONTROL

0.0 - - - U Z C U Z C u z c

LIVER

0.6

1.0

0.8 1 LUNG i:: 1 MUSCLE-BONE

FIGURE 5b. Concentrat ions o f Plutonium and Americium i n Composite Pocket Mouse Samples

- F U R - S K I N

-

-

-

-- [b,- U F C U F C U F C

D E E R M I C E

L I V E R

0.4

0 2

FIGURE 5c. Concentrat ions o f P l u t o n i um and Americi um i n Composite Deer Mouse Samples

1.0

0.8

0.6 n

& 0.4 \ .- U,

0.2

0.0

1.0

> 1 LUNG 1 1 MUSCLE-BONE

0.6

0.4 U,

0 2

(1_-

O.O F C F C F C 0.0 - - -

F C F C F C Z38pu 23gpu 241Am 238pu 23qPu 241Am

2 3 8 ~ u 2 3 9 ~ u 2 4 1 ~ m 2 3 8 ~ u 2 3 9 ~ u 241~rr

H A R V E S T M I C E

FIGURE 5d. Concentrat ions o f Pl utonium and Americium i n Coniposi t e Harvest Mouse Samples

-

- MUSCLE-BONE

-

- U - U - D I T C H F - FOREST

- C - CONTROL

- - - - U F C U F C LI F C

-

- LUNG

-

-

-

- - - U F C U F C U F C

1 .o

0.8

0.6 D

E P 0.4 .- U,

0.2

0.0

1.0

0.8

0.6

0.4

0.2

0.0

23gPu 239pu 241A, 23gPu 239pu 241A,

-

- L l VER

-

-

- F - - F C F C

F - FOREST - C - CONTROL

- F U R - S K I N

-

-

- - - F C F C F C

1.0

0.3

0.6

0.4

0.2

0.0

TABLE 2. U-Pond Pluton ium Ana l ys i s on Whole Mice

2 3 8 ~ u 239+24OPu - - - Species x Dry W t g x pCi /g d r y x pCi/g d r y

Deer Mouse Z-Di t c h 4.5 0.10 (0.005) 0.98 (0 .05)

n=3 Cont ro l 5.0 0.13 (0.006) 0.12 (0.006)

n=l

House Mouse Meadow 4.8 0.03 (0.002) 0.07 (0.003)

n=2 Cont ro l 3.8 0.03 (0.002) 0.06 (0.003)

n= l

( ) = Count ing e r r o r .

Johnson, 1975). The presence o f f r e e wate r and an abundance o f r i p a r i a n vegeta- t i o n enhances t h e a v a i l a b i l i t y o f food f o r t h i s mouse. MacMil len (1964) showed t h a t deer mice, when f e d a d i e t o f o n l y d r y seeds, had a mean t ime t i l l death o f about 20 days. Th is suppor ts t h e t heo ry t h a t they must s a t i s f y t h e i r wa te r requirements by e a t i n g green vege ta t ion , ar thropods, o r by d r i n k i n g f r e e water. The deer mice l i v i n g a t U-Pond most l i k e l y do a l l th ree .

The house mouse i s l i k e w i s e an omnivorous feeder, e a t i n g seeds, f r u i t s , vegetables, meat and ar thropods ( I ng les , 1965; Brooks, 1973). Th is mouse a l s o seeks t he l u s h vege ta t i on and f r e e wate r o f t h e d i t c h e s and pond t o s a t i s f y i t s wa te r requi rements. The western harves t mouse a l s o s e l e c t s a h a b i t a t w i t h dense vege ta t ion , e s p e c i a l l y grasses near water . The major food i tems a re seeds, succu len t stems, f r u i t s , and i n s e c t s ( H a l l and Kelson, 1959; I ng les , 1965; B u r t and Grossenheider, 1976). I n an a r i d environment, U-Pond p rov ides an i d e a l h a b i t a t f o r t h i s mouse.

The pocket mouse, on t h e o t h e r hand i s p r i m a r i l y a g r a n i v o r e and can sub- s i s t s o l e l y on a d i e t o f d r y seeds (Schmidt-Nielson e t a l . , 1948; Kr i tzman, 1974). Th i s spec ies does n o t need f r e e wate r b u t o c c a s i o n a l l y ea t s green vege ta t i on dur - i n g t h e s p r i n g months when a v a i l a b l e . Pocket mice a l s o p r e f e r t h e d r y sandy s o i l o t t n e surrounding noncontaminated dese r t f o r c o n s t r u c t i n g t h e i r deep and e labo- r a t e burrow systems (Sche f fe r , 1938; H a l l , 1946). Th is p robab ly exp la i ns t h e low a c t i v i t y l e v e l s observed i n pocket mice a t t h e U-Pond s i t e .

GAMMA EXPOSURES TO SMALL MAMMALS

Small mammals assoc ia ted w i t h t h e U-Pond s tudy s i t e were a l s o i n v e s t i g a t e d f o r e x t e r n a l garrnla exposure. The procedure i n v o l v e d s u r g i c a l l y i m p l a n t i n g t h e r - moluminescent dosimeters (TLDs) subcutaneously and r e l e a s i n g t h e animal t o be caught a t a l a t e r date. The technique proved very successfu l ; o v e r a l l , 49% o f t h e TLDs implanted were recovered.

Dosimeters recovered f rom animals 1 i v i n g i n t h e Meadow area e x h i b i t e d t h e h i ghes t exposures (F igu re 6 ) . The t h r e e species represented t h e r e were, from h ighes t dose t o lowes t , t h e house mouse, pocket mouse, and deer mouse w i t h mean doses o f 55 R/yr, 43 R/yr, and 21 R/yr, r e s p e c t i v e l y (Table 3) . The Fo res t t r a n - sec t was a l s o represented by a l l t h r e e species and l i k e w i s e showed s i g n i f i c a n t exposures above background. The Z-D i tch was t h e o n l y o t h e r t r a n s e c t t o show animals r e c e i v i n g s i g n i f i c a n t exposures. The animals be ing exposed on t h i s t r a n s e c t were deer mice. Pocket mice were a l s o represented on Z Transect c l a im- i n g Illore recap tu res than any o t h e r species o r 1 oca t ion . Th i r t y - two dosimeters were recovered g i v i n g a mean dose o f 0.14 R/yr. Th i s f i g u r e agrees w i t h t h e pocket mouse exposures on t h e c o n t r o l t r a n s e c t o f 0.09 R/yr. The exposure da ta from U-Di tch were represented by o n l y one species, t h e pocket mouse, whose doses were s l i g h t l y h i ghe r than t h e c o n t r o l w i t h 0.35 R/yr. Deer mice f rom bo th con- t r o l t r ansec t s had i d e n t i c a l exposures o f 0.07 Rlyr.

Dosimeters were n o t recovered f rom house mice on Z Transect, U Transect, o r t h e c o n t r o l t r a n s e c t s and deer mice on U Transect . Capture f requenc ies f o r house mice a r e ve ry low even i n an area o f h i ghe r dens i t y . Th is i s a t t r i b u t e d t o t h e seeming s i x t h sense o f house mice f o r shy ing away f rom t r a p s (Brooks, 1973) a long w i t h a probable low dens i t y . Personal exper ience has shown t h a t har- v e s t mice a r e very d i f f i c u l t t o t r a p and even more d i f f i c u l t t o r e t r a p . A1 though s i x animals were s u c c e s s f u l l y implanted w i t h TLD packets, t h e r e were no recap- t u r e s and, consequent ly, no exposure r a t e data were obta ined. The number o f deer mice captured a long U Trench was a l s o ve ry l ow throughout t h e s tudy per iod .

From t h e dos imeter data gathered i n t h i s study, i t becomes apparent t h a t mice l i v i n g i n t h e Meadow and Fo res t t r ansec t s r ece i ved t h e most s i g n i f i c a n t gamma exposure. T h i s can be a t t r i b u t e d t o t h e f a c t t h a t a t one t ime t h e pond was much l a r g e r , encompassing these areas. When t h e pond receded i t l e f t sed i - ments c o n t a i n i n g rad ionuc l i des exposed and r e a d i l y a v a i l a b l e t o t e r r e s t r i a l p l a n t s and animals.

The e f f e c t f rom t h e h i ghes t exposure r a t e recorded a t U-Pond (1.47 R/wk t o a pocket mnuse; see Appendix C-5) would p robab ly be ve ry s l i g h t o r even immeasurable. A decrease i n t h e number o f c i r c u l a t i n g lymphocytes i n t h e b lood i s a ve ry s e n s i t i v e measure of r a d i a t i o n exposure. Acute doses of 5-25 rads can cause a drop i n t h e number of these c e l l s i n r a t s (Casare t t , 1968). However, w i t h a maximum ch ron i c dose o f approx imate ly 1 .4 r a d per week, a decrease i n lymphocytes may n o t be de tec tab le . No obvious abno rma l i t i es were n o t i c e d i n mice du r i ng t h i s s tudy. F u r t h e r i n v e s t i g a t i o n o f h i s t o p a t h o l o g i c a l changes i s needed t o determine t h e e f fec ts of ve ry low ch ron i c exposures t o U-Pond mice.

EDAPHIC EXPOSURE RATES

Dosimeters p laced i n t h e s o i l a long t h e t r a p p i n g t r ansec t s revea led t h a t t h e l o c a t i o n o f t h e s t r onges t gamma exposures i s t h e t o p dec imeter o f s o i l (F i gu re 7 ) . The h i g h e s t exposures came from t h e Meadow t r a n s e c t w i t h a mean o f 75 R l y r i n t h e f i r s t decimeter. The l e v e l s o f exposure d im in ished r a p i d l y w i t h depth, go ing down t o 1.5 R/yr a t 5 dm (Table 4 ) . Th i s t r e n d i s c o n s i s t e n t

FIGURE 6. Gamma Exposure t o Mice L i v i n g Along U-Pond and Cont ro l Transects

TABLE 3. Mean Gamma Exposures t o U-Pond Mice i n R/yr

Pocket Mouse Deer Mouse House Mouse Rlyr + S.E. Rlyr + S.E. Rlyr + S.E.

R. S . C ~ n t r o l ( a ) 0.07 2 0.003 U. P. Con t ro l 0.09 + 0.005 0.07 + 0.003 Z-Di t c h 0.14 + 0.01 5.74 + 4.83 U-Di t c h 0.35 + 0.11 Fo res t 4.02 + 2.5 2.92 + 0.41 13.5 + 8.8 Meadow 42.6 + 7.32 21.1 + 1.9 54.9 + 1.7

( a ) Ra t t lesnake Spr ings Con t ro l .

LN EXPOSURE RATES (R/yr)

X I

+ 7 0

cn-i . n, mcn - rl-

-

0 0 0 0 0 0 . ~ . . . 0 0 0 0 0 0 - J O O O O O W V 4 W P L n r n - - 1:;

on a l l t h e t ransec ts a t U-Pond. The c o n t r o l t r ansec t shows t h e exposure r a t e t o be cons i s ten t f rom t h e sur face t o 5 dm. The h igher exposure r a t e s t o t h e s o i l i n t h e Meadow and Forest areas concur w i t h the h igher exposure l e v e l s o f t h e animals l i v i n g on these areas.

Neutron Exposure i n t h e S o i l

U-Pond h i s t o r i c a l l y has received 1 ow-1 eve1 re1 eases o f p l u t o n i um process- i n g wastes a1 ong w i t h many o t h e r t ransuran ics a t marg ina l l y de tec tab le l e v e l s (Emery and Gar1 and, 1974). 'The pond receives p l utonium processing e f f l u e n t s from t h e 234-5 p l a n t v i a t h e Z-19 D i tch . Al though processing wastes cont inu- ous l y f l o w i n t o t h e d i t c h , re leases o f p lu tonium are u s u a l l y low l e v e l and on an i n t e r m i t t e n t bas is . For t h i s reason, dosinieters capable o f d e t e c t i n g t h e r - mal neutron r a d i a t i o n were incorpora ted i n t he s o i l dosimeter probes a long the t ransec ts .

The Meadow area showed the h ighes t neutron exposure again i n t he f i r s t decimeter of s o i l w i t h an average o f 37 mrad ly r (Table 5 ) . The f o r e s t t r a n - sec t showed q u i t e a reduced dose from the Meadow w i t h 4.8 mrad/yr a t 1 dm and again t a p e r i n g down w i t h depth. The Z-19 D i t c h was the o n l y o t h e r l o c a t i o n sampled t h a t showed a neutron exposure. I n t h i s case, however, t h e t rend o f h ighes t t o lowest f rom t h e sur face down was somewhat reversed. The h ighes t average l e v e l detected here was 7.8 mrad/yr and was a t 4 dm. The lowest was 1.9 mrad/yr a t 1 dm and the sur face. Th is reverse t rend i s probably a func- t i o n o f t he dosimeter l o c a t i o n near the d i t c h . On t h i s t ransec t , t h e aluminum tub ing con ta in ing t h e dosimeter was placed halfway down the s lope of t he d i t c h . Th is made t h e bottom l o c a t i o n s on the dowel c l o s e r t o t h e l e v e l o f water i n t h e d i t c h (F igure 8 ) . The doses a long U-14 D i t c h and the c o n t r o l t r a n s e c t were s i m i l a r a t a l l depths, i n d i c a t i n g background exposures.

TABLE 5. Mean Neutron Exposure t o S o i l on U-Pond i n mrad/yr

Soi l Depth - Meadow Forest Z - Transect U Transect - Control i n Decimeters x + S.E. i -+ S.E. x ? S.E. i + S.E. x + S.E.

0 37.1 + 16.2 4.1 + 1.58 1.87 + 1.25 0.48 + 0.02 0.26 + 0.0

FIGURE 8. Cross Sect ion o f Z-19 D i t c h Showing Locat ion o f S o i l Dosimeter Probes

CONCLUSIONS

Trapping resul ts along with the radiochemical analyses indicate that the areas of most concern a t U-Pond were the Z-19 Ditch and the riparian zone associated with the ,pond. A1 1 species of mice captured in these areas (except pocket mice along Z-Ditch) accumulated concentrations of radiocesium significantly above background.

The number of individuals representing each species on a transect appeared t o vary according to habitat preference. Pocket mice preferred the noncontaminated sagebrush-cheatgrass habitat adjacent to the ditches over the riparian . I habitat surrounding the pond, as indicated by trapping resul ts . Thus, the fewer numbers of th i s species l iving near the pond reduced the transfer potential for pocket mice. House mice and deer mice preferred the denser vegetation around the pond and thus pose a greater threat for biological transfer due to the i r food habits and greater numbers in th i s area. The potential for biological transfer of radionuclides to a small mammal species and u p through the food chain i s proportional t o the number of individuals of that species present and the avai labi l i ty of radionuclides in an area. Further information should be gathered to determine the origin of the radionuclide concentrations in these animals. The biological transfer pathway of radionuclides to mice could be further examined by diet analysis. A follow-up on the results could include a radiochemical analysis of the food items detected. The emphasis of waste management a t this s i t e could then be directed toward the primary biological transfer organisms.

The radiation exposure data from thermoluminescent dosimeter (TLD) implants showed the highest exposures t o animals l iving along the transects near the pond. The three species for which data were obtained (house mice, deer mice and pocket mice) each had exposures above background. This trend agrees with the radiochemical analysis data from these areas. Animals living along the Meadow and Forest transects appear to be accumulating above background concentrations of radionuclides and external radiation exposures. This also appears to be true for mice living along the two ditches, b u t to a lesser degree. In most instances the values from the ditches appear only s l ight ly above background.

Results from dosimeters placed in the soil along the trapping transects showed the greatest exposure in the surface decimeter of so i l . The transects with the highest exposure were those closest to the pond. This means that the surface decimeter of soil near the pond probably has the highest concentrations of radionuclides. This low level contamination could be readily available to vegetation which provides a food base for the inhabiting mice. I t could also account for the higher exposure rates to mice living near the pond.

Deer mice captured along Z-19 Ditch received higher exposure rates than corresponding soi l dosimeters. This i s due to the location of the soil dosimeters along one bank of the ditch. These higher exposure rates indicate that the deer mice preferred the dense vegetation near the bottom of the ditch where higher exposure rates exis t . The water and lush emergent vegetation covering the ditch provided a good habitat for deer mice.

LITERATURE CITED

Arena, V . 1971. I o n i z i n g Rad ia t i on and L i f e . C. V . Mosby, S t . Lou is , MO.

Brooks, J . E. 1973. A Review of Commensal Rodents and T h e i r Con t ro l . IVew York S ta te Department o f Heal t h y Bureau o f Rodent Contro l , A1 bany, NY, pp. 405-453.

Bur t , W. H., and R. P. Grossenheider. 1976. A F i e l d Guide t o t h e Mammals. Houghton-Miff1 i n Company, Boston, MA.

Casaret t , A. P. 1968. Rad ia t i on B io logy . P ren t i ce -Ha l l , Inc . Englewood C l i f f s , NJ.

C l ine , J. F., D. W. Uresk, and W. H. Rickard. 1975. Cha rac te r i za t i on of P l a n t Communities Adjacent t o t h e B-C Cr i bs C o n t r o l l e d Area and REDOX Pond Areas on t h e 200 Area Plateau. BNWL-1916. B a t t e l l e , P a c i f i c Northwest Labora to r ies , Richland, WA.

Daubenmire, 1970. Steppe vege ta t i on o f Washington. Wash. Ag r i c . Exp. Tech. 62, 131 pp.

Emery, R. M., and T. R. Garland. 1974. The Eco log ica l Behavior o f P lu ton ium and Americium i n a Freshwater Ecosvstem: Phase 11. BNWL-1879. B a t t e l l e , "

P a c i f i c Northwest Labora to r ies , Rich1 and, WA.

Energy Research and Development Adm in i s t r a t i on . 1975. F i n a l Environmental Statement. 2 Vol s. ERDA-1538, Waste Management Operat ions, Hanford Reserva- t i o n , Richland, WA.

F i t zne r , R. E. , and W. H. Rickard. 1975. Av i fauna o f Waste Ponds, ERDA Hanford Reservat ion, Benton County, Washington. BNWL-1885. B a t t e l l e y P a c i f i c Northwest Labora to r ies , Richland, WA.

Flake, L. D. 1973. Food h a b i t s o f four species o f rodents on a shor t -g rass p r a i r i e i n Colorado. J . Mammal. 54:636-47.

H a l l , E. R. 1946. Mammals o f Nevada. Univ . C a l i f . Press, Berke ley and Los Angeles.

H a l l , E. R., and K. R. Kelson. 1959. The Mammals o f Nor th America. Ronald Press Co. , New York.

I ng les G. L. 1965. Mammals o f t h e P a c i f i c States. S tan fo rd Univ. Press, Stanford, CA.

Johnson, M. K. 1975. I n t e r s p e c i fi c Assoc ia t i on of Peromyscus manicuZatus , Pero.qnathus parvus, and SpermophiZus tmnsendi on t h e A r i d Lands Ecology Reserve Examined by D i e t Over lap and Related Data. BNWL-1929. B a t t e l l e , P a c i f i c Northwest Labora to r ies , Richland, WA, 50 pp.

Kritzman, E. G. 1974. Eco log ica l r e l a t i o n s h i p s of Peromyscus manicuZatus and Perognuthus parvus i n eas te rn Washington. J. Mammal. 55:172-88.

MacMil len, R. E. 1964. Popu la t ion ecology, wa te r r e l a t i o n s , and s o c i a l beha- v i o r of a southern C a l i f o r n i a semi-desert r oden t fauna, Univ. Cal i f o r n i a Pub1 . ZOO^. 71: l -66.

Na t iona l Bureau o f Standards. 1964. Phys ica l Aspects o f I r r a d i a t i o n . NBS Handbook No. 85. U.S. Government P r i n t i n g O f f i c e , Washington, DC, p. 3.

Sche f fe r , T. H. 1938. Pocket mice o f Washington and Oregon. U.S.D.A. Tech. B u l l e t i n 608.

Schmidt-Nielsen, B., D. Schmidt-Nielsen, A. Brokaw, and H. Schneiderman. 1948. Water conserva t ion i n dese r t rodents . J. C o l l . Comp. Phys io l . 32: 331 -360.

Wi l l i ams, 0. 1959. Food h a b i t s o f t h e deer mouse. J. Mammal. 40:415-19.

APPENDIX A

DETECTABLE GAMMA-EMITTING NUCLIDES

TABLE A.1. Composite Sample Using L i k e Tissues f rom Two o r More Animals o f Same Species, pCi 137Cs/g Dry

A. 1 .1 Fur-Skin Samples

TRANSECT

Sample Sessions Pocket Mouse Deer Mouse Harvest Mouse House Mouse

CONTROL Apr-i 1 0.44 (0.44) - - May - - - - October - - 10.0 (3.6) R.S. October 1.3 (1 .2)

Z-DITCH A p r i 1 1.7 (1 .1) - - May 0.99 (0.66) 8.7 ( 1 .O) October - - 12.0 (4.9)

MEADOW A p r i 1 May October

U-D ITCH A p r i 1 2.5 (2.5) May 2.5 (0.78) 33.0 (1.7) October 3.1 (1 .6)

FOREST A p r i 1 May October

R.S. - Rat t lesnake Spr ings Con t ro l ( ) - Count ing e r r o r - - - Values l e s s than d e t e c t i o n l i m i t s

TABLE A. 1 . (Cont inued)

A.1.2 L i v e r Samples

TRANSECT


CONTROL A p r i 1 - - - - May - - - - October 3.3 (2.2) - - R.S. October

Z-DITCH A p r i 1 - - 2.8 (2 .6) May - - 9.8 (2.8) October 5.8 (3.2) 11 .O (9 .7 )


U-DITCH A p r i 1 - - Yay 62.0 (5.1) October 1 x 0 (4.9)


R.S. - Rat t lesnake Spr ings Cont ro l ( ) - Count ing e r r o r -- - Values l e s s than d e t e c t i o n l i m i t s

TABLE A.1. (Continued)

A.1.3 Kidney Samples

TRANSECT

1975


CONTROL Apr i 1 9.5 (5.5) - - May - - - - October - - - - R.S. October - -

Z-DITCH Apr i 1 27.0 (26.0) - - May - - 18.0 (8.8) October 18.0 (13.0) - -

MEADOW Apr i 1 May October

U-DITCH A p r i l 54.0 (45.0) May - - 50.0 (12.0) October - -

FOREST Apr i 1 May October

R. S. - Ratt lesnake Springs Contro l ( ) - Counting e r r o r - - - Values l e s s than de tec t i on l i m i t s


A. 1.4 Lung Samples

TRAN SECT

1975


CONTROL Apr i 1 - - 124.0 (80.0) May - - - - October 15.0 (9.1) 45.0 (24.0) R.S. October - -

Z-DITCH Apr i 1 May October


U-DITCH Apr i 1 May October

FOREST Apr i 1 May October

R. S. - Ratt lesnake Springs Contro l ( ) - Counting e r r o r - - - Values l e s s than de tec t i on l i m i t s


A.1.5 G I T rac t Samples

TRANSECT

Saniple Sessions Pocket Mouse Deer Mouse Harvest Mouse House Mouse

CONTROL A p r i 1 1.3 (0 .9) - - May - - - - October 1.8 ( 1 .o) - - R.S. October 0.72 (0.71)

Z-DITCH A p r i 1 - - - - May - - 13.0 (3.7) October 2.6 (1.3) 9.7 (6.8)


U-DITCH A p r i l 14.0 (4.7) May 7.1 (1.6) 122.0 (3.2) October 8.4 (2.8)


R.S. - Rat t lesnake Spr ings Cont ro l ( ) - Count ing e r r o r - - - Values l e s s than d e t e c t i o n l i m i t s

TABLE A. 1. (Continued)

A. 1 .6 Muscle-Bone Samples

TRANSECT


CONTROL Apr i 1 0.53 (0.25) - - May - - 0.54 (0.40) October 0.67 (0.52) - - R.S. October - -

Z-DITCH Apr i 1 May October


U-DITCH Apr i 1 - - May 5.2 (0.5) 68.0 (2.2) October 8.2 (1 -0 )


R.S. - Ratt lesnake Springs Contro l ( ) - Counting e r r o r - - - Values l e s s than de tec t i on l i m i t s

A.2. Composite Samples Other Than 137Cs, p C i / g Dry

A.2.1 Sampl i n g P e r i o d 9-10 A p r i l ' 7 5

Species & Sampl e 40K 54Mn 6oCo 6 5Zn 9521" l o6Ru 144Ce

U-POND CONTROL TRANSECT

Deer Mouse Muscl e-Bone Fur -Sk in Head

Pocket Mouse Lung Muscl e-Bone 13 (3.6)

Deer Mouse Fur -Sk i n G I T r a c t Head

Pocket Mouse Muscl e-Bone Head

Deer Mouse L i v e r

Deer Mouse K i dney Muscl e-Bone

House Mouse Feet -Ta i 1 Head

Z-DITCH TRANSECT

FOREST TRANSECT

MEADOW TRANSECT

Harves t Mouse Head

Species & Sampl e

Deer Mouse L i v e r K idney Lung GI T r a c t

Pocket Mouse L i v e r Kidney GI T r a c t

Deer Mouse L i v e r GI T r a c t

Pocket Mouse Lung G I T r a c t

Deer I4ouse Kidney

! J r : ~ , -e t :;:.,use Lung G I T r a c t r luscle-Bone

Deer Mouse L i v e r Lung Muscle-Bone

House Mouse L i v e r Kidney Lung G I T r a c t bluscle-Bone

Deer Mouse L i v e r Muscle-Bone

House Mouse L i v e r Kidney Lung

TABLE A . 2. (Continued)

A . 2 . 2 Sampling Period 6-7 May '75

40K 54Mn 60Co 65Zn 9 5 Z r l o6Ru 1 4 V e

11-POND CONTROL TRANSECT

2-DITCH TRANSECT

19 (5 .1)

U-DITCH TRANSECT

FOREST TRANSECT

MEADOW TRANSECT


A.2.3 Sampling Period 23-24 October ' 7 5

Spec ies & Sample - '+OK S4Mn 60Co 65Zn 9 5 Z r l06Ru l 4 ? e


Deer Mouse Muscle-Bone 45 (22 )

Pocket Mouse Fu r -Sk in 28 (11) L i v e r 67 ( 3 1 ) Lung Muscle-Bone 20 (6 .9 )

Deer Mouse Muscle-Bone

House Mouse Fu r -Sk in L i v e r

Z-DITCH TRANSECT

9.1 ( 3 . 5 )

Pocket Mouse Fu r -Sk in 2.3 (0 .9) 3 .7 (1 .4 ) I.luscle-Bone 18 (6 .4)

U-DITCH TRANSECT

Pocket Mouse Fu r -Sk in 51 ( 2 2 ) 8 .2 (2 .9 ) Lung 182 ( 6 7 ) Ptuscle-Bone 29 (13 ) 2.6 (1 .1 ) 4.0 (1 .7 )

Deer Mouse Fu r -Sk in Kidney

House House Fu r -Sk in

Ha rves t IAouse Muscle-Bone

Deer Mouse Kidney Lung

MEADOW TRANSECT

RATTLESNAKE SPRINGS CONTROL

Deer Mouse L i v e r 5 .7 (2 .8 ) Muscle-Bone 22 (6 .4 )

TABLE A.3. U-Pond Samples Co l lec ted During 1976-77 and Analyzed as I n d i v i d u a l Animals, pCi 1 3 7 ~ s / g Dry

TLD Sampl e Pres . Number Pocket Mouse Deer Mouse House Mouse


U-DITCH TRANSECT

Z-DITCH TRANSECT

76UM05-a 05- b

76UM08-a 08- b

76UM10-a 10-b

Yes 77UM01 -a 01 -b

Yes 77UM02-a 02-b

Yes 77UM03-a 03- b

Yes 77UM04-a 04- b

Yes 77UM17-a 17-b

Yes 77UM18-a 18-b

TABLE A. 3. (Cont inued)

TLD Sampl e Pres. Number Pocket Mouse Deer h u s e House Mouse

FOREST TRANSECT

FEADOW TRANSECT

( ) - Count ing e r r o r - - - Below d e t e c t i o n l i m i t s

a - Sample c o n s i s t s o f sk in , f u r , f e e t , t a i l b - Sample cons i s t s o f remain i ng carcass

TABLE A.4. U-Pond Samples Co l l ec ted Dur ing 1976-77 and Analyzed as I n d i v i d u a l Animals, PcI /g Dry

Samples Other Than 137Cs

Species & Samp 1 e 40K 54Mn 6oCo G5Zn q5Zr l06Ru 144Ce


Pocket Mouse

77UM10-a 10-b

77UMll-a 11-b

77UM12-a 12-b

77UM13-a 13-b

U-DITCH TRANSECT

Pocket Ibouse

77UM05-a 05-b

77UM21-a 21-b 33 ( 1 4 )

77UM22-a 22-b 56 (15)

House House

77UM14-a 14-b

Z-DITCH TRANSECT

Deer Mouse

Pocke t [ louse

76UM10-a 10-b

77UM01 -a 01-b


Species & Sample 40K 54Mn 6oCo 6 5Zn 9 5 Z r 106Ru ' 44Ce

FOREST TRANSECT

Pocket Mouse

Deer llouse

76UMll -a 11-b

77UM07-a 07- b

77UM08- a 08- b

77UM09-a 09-b

77UM16-a 16-b

MEADOW TRANSECT

Deer Mouse

Pocket Mouse

( ) - Counting e r r o r a - Sample cons is ts o f sk in , f u r , f e e t , t a i l b - Sample c o n s i s t s o f remaining carcass

A-15

TABLE C.2. (Cont inued)

F o r e s t Transec t Cont. U-Di tch Transect

House Mouse Pocket Mouse Pocket Mouse

Sex Dose Sex Dose Sex Dose Sex Dose

a" 426.4 a* 33.8 a* 7.8 a" 3.0

a* 88.5 f 221.2 9 4.2 9 2.1

9 19.7 9 4.3 a" 2.4

9 32.3 oT 3.0 a* 11.6

a" 3.9 9 4.4

a" 4.0 a* 4.8

a" 10.9 a" 5.2

a" 1.9 a" 46.8

a" 2.3 a" 5.7

a* 2.1 9 3.0 - - - - - - - - - - - - - _ _ _ _ - - - - - - - - - -

n = 2 4 20

2 + S.E. = 258 + 170 76.8 + 48.3 6.7 + 2.2

Range = 426 t o 89 19.7 t o 221 1.9 t o 46.8

APPENDIX D

GAMMA AND NEUTRON EXPOSURES TO S O I L ALONG U-POND TRANSECTS

TABLE D.1. Gamma Exposure i n S o i l Along U-Pond Transects i n Roentgens Per Year

CONTROL TRANSECT

S o i l Depth #1 #2

0 dm .084 .073

1 dm .084 .084

2 dm . l o4 . l o4

3 dm .073 . lo4

4 dm -104 . l o4

5 dm . I15 .094

Z 'TRANSECT

So i l Depth

U TRANSECT

S o i l Depth

Dosimeter Locations -

#3 # 4 # 5 X

.073 .073 .084 .077

.084 .084 .084 .084

.094 .094 .084 .096

.094 . l o4 .084 .092

.094 . l o 4 .084 .098

.094 . l o4 . I15 . l o4

S.E.

.002

0.0

.003

.006

.004

.005

T A B L E D . 1. (Continued)

FOREST TRANSECT

S o i l Depth # 1

0 dm 14.2

1 dm 23.2

2 dm 6.23

3 dm 1.90

4 dm .699

5 dm .354

Dosimeter Loca t ions -

#2 #3 # 4 # 5 x S. E.

4.50 11.9 .542 2.69 6.78 2.67

3.19 8.88 .230 2.71 7.64 4.14

.824 3.41 . I 2 5 .814 2.28 1.14

.334 1.70 . I 1 5 .407 .892 .376

.354 4.59 . I15 .292 1.21 .850

.208 ,303 . I35 .365 .273 .044

MEADOW TRANSECT

S o i l Depth

TABLE D.2. Neutron Exposure i n S o i l Along U-Pond Transects i n mrads Per Year

CONTROL TRANSECT

S o i l Depth # 1

Z TRANSECT

S o i l Depth

U TRANSECT

S o i l Depth

Dosimeter Loca t ions

$2 # 3 $4 # 5

0.26 0.26 0.26 0.26

0.31 0.31 0.31 0.26

0.26 0.37 0.31 0.37

0.37 0.26 0.37 0.31

0.31 0.26 0.37 0.31

0.31 0.31 0.31 0.37

TABLE 0.2. (Continued)

FOREST TRANSECT

S o i l Depth #1

Dosimeter Locat ions

#4 # 5 x S.E.

0.68 1.62 4.1 1.58

0.37 1.41 4.8 2.69

0.31 0.63 1 .52 0.63

0.31 0.47 0.63 0.15

0.26 0.37 0.34 0.02

0.37 0.42 0.36 0.03

MEADOW 'TRANSECT

S o i l Depth

TABLE D. 3. Mean Gamma Exposure t o Soi 1 on U-Pond Transects i n Roentgens Per Year

S o i l Depth *adow Fores t Z-Transect U-Transect Con t ro l i n Decimeters i + S.E. i + S.E. x + S.E. x + S.E. i + S.E. --

APPENDIX E

SUMMARIES OF TRAPPING DATA

TABLE E.1. T o t a l Number o f I n d i v i d u a l Animals Captured Each Month

Apr 1975* May 1975* Oc t 1975* C Z M U F C Z M U F C I M U F - - - - - - - - - A - -

Pocket Mouse 9 3 1 5 6 5 6 6 3

Deer Mouse 2 4 2 2 6 5 1 4 6 2 1 2 2

House Mouse 2 6 4 1 4

Harvest Mouse 1 1

Mar 1976* May 1976 Jun 1976 J u l 1976 R.S. M U F M U F C Z M U F - - - - -

Pocket Mouse 4 1 3 9 1 8 5 3 9 2

Deer Mouse 5 5 1 3 4 1 7 9 4 2 2

House Mouse 1 1 4 5 6 2

Harvest Mouse 3 1

Aug 1976 Sep 1976 Nov 1976 Z M U F C R.S. C Z M U F

Pocket Mouse 7 3 8 2 11 8 5 7

Deer Mouse 2 2 1 2 5 5 3 2 6 2

House Mouse 1 3 1

Harvest Mouse 1

*Animals captured d u r i n g months were s a c r i f i c e d f o r rad iochemica l a n a l y s i s

R.S. = Rat t lesnake Spr ings Cont ro l C = U-Pond Cont ro l Z = Z Trench M = Meadow U = U Trench F = Fo res t

TABLE E. 1. (Continued)

Dec 1976 Feb 1977 Mar 1977 Z M U F - - - - R.S. - - - - - - C Z M U F

Pocket Mouse 4 1 6 9 3 4

Deer Mouse 3 4 1 3 12 4 2 3 1 4

House Mouse 3 2 1

Harvest Mouse

Apr 1977 May 1977 J u l 1977* . . R.S. C Z M U F - - R.S. Z !!A - F /Mt4F -

Pocket Mouse 3 1 4 4 6 2 1 3 6 1 1 2 6 3 3 1

Deer Mouse 18 3 1 7 1 7 5 1 3

House Mouse 1

Harvest Mouse 1 1

* Animals captured du r i ng months were s a c r i f i c e d f o r radiochemical ana lys is .

TABLE E.2. Average Number of Animals Captured on U-Pond Transects Per Trap Session*

R a t t l esnake U-Pond Spr ings Con t ro l Z-Trench Meadow U-Trench Fores t

- - - - - n x S.D. n x S.D. n x S.D. n X S.D. n x S.D. n x S.D. - - - - - - - - - - - -

Pocket Mouse 8 7 2.5 11 7.1 3.5 13 1.9 2.2 13 5.5 3.2 13 0.9 0.9

Deer Mouse 4 10.5 5.8 8 4.3 2.4 11 2.2 1.7 13 3.3 2.1 13 0.8 1.1 13 2.9 1.8

House Mouse 11 0.1 0.3 13 1.9 2.2 13 0.2 0.4 13 1.5 1.9

Ha rves t Mouse 13 0.3 0.9 13 0.4 0.5

*Data from Apr, May, Oct 1975, Mar 1976, and J u l 1977 were o m i t t e d due t o s e l e c t i v e t r a p p i n g f o r r a d i o - chemical a n a l y s i s .

m n = Number o f t r a p p i n g sessions 9 W

S.D. = Standard Dev ia t i on

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Documents

Analysis of Small Mammal - IAEA