PHILIP L. JOI-INSON*L', S. Cold Regions

Res. & Eng, Lab.Hanover, N. H.

Radioactive

Contamination

to Vegetation

Gamma radiation damageon an experimental forestarea is evaluated using

aerial photographywith four different

film emulsions.

(.1 bs/rl/ct 011 pl/ge 987)

I~TRODlJCTlO:\'

N ATL'RAL and culti\'ated yegetati\'e pat-terns consti tu te one of the se\'eral areasof interest in aerial photography obtained forinterpretation studies. Therelore, it is impor-tan t to understand just where \'egetationand the organisms composing it fit into theanalysis. Each organism is the result of itsgenetic potential ill/eracting with the enyiron-ment in which it lives. The internal processesin e\'ery indi \·id ual in concert wi th those ofthe biological community produce the re-sponse displayed to aerial sensors. Hence,vegetation is the resultant of a specific in-heri tance de\'eloping and in teracting wi th ex-lernal factors snch as climate, soil, topogra-phy, and other organisms.

One en\'ironmental factor, gamma racli-ation, is extremely important for two reasons.First, we need to understand the effects ofhigh energy radiation which man can un-leash but not \'et fulh' control; it becomes amalt~r of self-presen·~tion to understand theconsequences of our technology. Secondly,gamma radiation is one of the fe\\' environ-mental factors \\,hich man can J'egulate andyary in intensity without interaction withother factors of the eJl\'ironmental complex.

* Presented at the Annual Convention of thej\ll1erican Society of I'hotogranlll1etry, \\'ashing-lOll 1>. c., i\larch, 19(',L

Hence \I'e are learning some basic ecologyfrom controlled gamma irradiation experi-ments wit h natural plant populations (\Vood-\I'ell, 1963). In this regard, plants have lethaldosages comparable to humans.

CA~DIA EXPERDIEI'T

I n !II ay, 1963, a preliminary study of aforest exposed to gamma radiation was ini-tiated at Brookhayen :\ational Laboratoryon Long Island. The objecti\'e-can aerialphotography be used to monitor ionizingradiation damage to \'egetation?

The gamma forest experiment is funded bythe Atomic Energy Commission and directedby Dr. George \Voodwell. Ionizing radiationis supplied by 9,500 curies of Cesium 137 in-stalled in a towel' 12 feet above the ground.This Oak-Pine forest has been continuouslyirradiated since No\'ember, 1961; the sourcewas exposed four hours of each day. Cammadosage decreased wi th distance from thesource, consti tu ting a gamma gradien t. I n-asmuch as it is the cell nuclei that recei\'e thedamage from gamma radiation, and as thesensi ti vi ty of a species increases \I·i th the sizeand number of its chromosomes (Sparrowand \\'oodwell, 1961), the lethal dosage foreach species i· predictable.

Our problem \\'as to e\'aluate the \'egeta-tion response to a gamma gradien t by usc ofaerial photography. Accordingly, we de-signed a co-ordinated ground and aerialstudy which \I'ould yield quantitati\'e expres-sion of photographic pattern and \'egetationdifferences.

l\]ETHOD

Photography was obtained at 1,200 feetabove mean terrain from a helicopter with ahand-held Cranex camera having a six-inchfocal length lens. The four emulsions u 'ed\I'ere Kodak Tri-X, Infrared, l~ktachroJlleER, and on some Rights Ektachrome Infra-red Aero ftlm, commonly known as camou-Rage detection film (C-D) (Figure 1.). :\\Vratten 89B filter was used with the infraredfilm to exclude all \I'a\'elengths below 700 mM,and a \\'ratten 12 filter was lIsed with theC-D film to exclude blue wavelengths.

FJG. 1. \'ertical photography at a scale of 1/1,200over the gamma forest. A. Infrared film (700-900mIL) B. Panchromatic film (400-700 IllIL) C.Ektachrome {illll 400-700 IllIL, D. Call1ollAage De-tection film (500-900 mIL).

984

A

J\lO;\'!TORI:\G R_\DI O_\CTl n.; CO;\,T_\~I t:\',\TIO\' TO \'I,GET_\TION 987

In order to c\-aluate thc influence of phc-nology (the rclation hctwcen environmcntand pcriodic biological phcnomcna-in thiscase leaf de\-clopmcnt) during thc growingseason, pcriodic flights \\-en: madc from :\[aythru Dccember, 1963_ Ground photographsalong the gamma gradient were takcn withthe samc emulsions at thc time of each flight_

the forcst floor, and panchl-omatic film hadthc lcast con trast bu t thc greatest apparcn tresolution becausc of its highcr film spced_

Thc discrimillation of pine frolll oakcrowns \\-a casicst on Ektachrome, possibleon infrarcd \I-hcrc it \I-as darke,- than thedeciduous crowns, and possiblc on panchro-matic film only for those indi\-jdual trccs that

:\USTJ{ACT: Camma railialioll is all 'imporlalll cOllseqllellce of Ollr III1c1earlecll/lology_ .lerial pholography was oblailled of ([II experimelll collillicied 10([ssess plalll respollses 10 !'IIriolis dosages of ga111111a radialioll 011 LOllI'. IslaJ/ll_Pallchromalic, illfrared, color alldfalse color.fil11ls were silidied alld sllbjecled 10microdellsilomelry 10 pr01'ide gila II lila live expressiolls of II,e pllOlograpllic imageas II fllllclion of Ihe gamma grailielll, film Iype, leaf de!'elopmelll, aJ/(1 species_.ler-ill! mOllilorillg of rudiai'iol/. damage 10 vegelalion has Ihe possibilily oj delecl-illg Ihis killd of dislllrbuJ7ce_

\-ECETATION ZO:\ES IN I{ESI'O!':SE TO A CAM~I.\

GRAlJIE"iT (:\FTER \\-OOIJ\\-ELL, 1962)

1 Tree growth was inhibited ill this zone as loll'as 2r/day (about 110 m_).

2 Consists prinlarily of Gaylllssacia and Va cc i-nium species,

were clcarly tallcr than the surrounding forestcanopy_

On 10 Octobcr thc deciduous Icm-cs hadcompletcly changcd color and thc pines were\-ery conspicuou s on color and C- D II 1m_ Inearly Decem bc'- the decid uous 1ea\-cs hadfallen and pine crO\\-ns were very ob\-iousagainst the fallcn litter on the forcst floor.I den Li fication of a gamma d isturba nce onpanchromatic film was only possible becauseof thc lowcr densi ty of standing tree stemsand slightly lightcr tone of thc older Icaf litterncar the source_ This oldcr litter which hasbeen decomposing for a ycar is a strong ab-sorber of near infrared ",a\-elengths and ap-

15

SO48-3232-2222-15

J)isla licefrom

SourceJrelers( 1962)

350

J)ailyExposure

Naler/20-hr

day

13ackgroLl nd l20-6060-150

150-350

l'egelalion Zone

Oak-pine forestOak forestEricaceous heath'Carex zoneZone of dead vascular

plants

:-\ fi\-e-step gray scale and four-step colorpanels were incorporated in both acrial andground photography_

RESULTS Ai\D I)JSCUSSJO:-l

:\11 of the photographv at a scale of 1/2.400clearly shO\\-s a forested area disturbcd froma point source_ Bccause of the flatness of thcterrain, species simplicity, and uniform dis-tribution the concentric yegetation zoncscoincidc ,,-j th species tolcrance to ionizingradiation_ ] t is obvious that Pitch Pine(Pill liS rigida) is the most sensi ti \-c specicsand is killed to the greatest distancc from thesource; sedge (Care.>:: penllsyv([lIiCII) is amongthe most tolerant_ Species tolerance in fi\-edistinct ycgetation zoncs are sho\\-n in Table1.

Thcre \I-as a phenological delay associatcd\\-ith highcr (hut not Icthal) gamma dosagc,and suHicient leaf expansion had occurred by16 :\Iay to clearly distinguish the gamma ex-perimcnt from the surrounding forest_ This\\-as particularly true on color and infraredfilm and only dimly identifiable on panchro-matic lilm_ The steepness of the ycgetationgradicnt incrcascd \I-ith thc developing foli-age to mid-Junc (Figurc 2)_ By late Septem-ber thc fringe of live vcgetation appearedmore diffuse, presumably because a smallnumbcr of leafy shoots dc\-cloped during thesummcr growing season in more shelteredlocations or from morc resistant indi\-iduals_

:\s might be expected, color film prcscntedthe grcatest information for qualitativeinterpretation, infrared film had thc greatestcontrast between live vcgctation and litter on

088 PI IOTOGRAMM ETRIC E:-IG1;-':EE R I;-':G

FIG. 2. Hemispherical ground photographs along a radius at 20 meter intervals from the gamma sourceshowing increasing canopy with decreasing dOSilge on 1-1- June 1963.

F1G. 3. Transmission density of pa nchromatic lindinfraredlilml"ilong the gamma gradient exposed l-'June 1963 uver the gam IIIa forest.

2070

83030015810084

18

,-'

/' ,PAICNN'ATIC/ '- IIFIlAIlED:',

/ I ,__ / '-- \...... ",', ,-\ ', ', ,

""•

TWO FILMS -14 JUNE

j~.50L.---=------::':--:7-----=-L.----,-'--::-L-"""'-:-.=.J loG

20 40 60 80 100 120 140 160IJISTAler FlO' SOUICE /I .fTf6S

1.10~

~ .90i::~ .70

Color re\"crsal Ii 1m is a posi ti \"e transparency,thereforc, thc density \'alues correspondingto the three cmulsion laycrs are plotted on anordinate of decreasing density \"alues for COIll-parison (Figure 5). These yalues ha\'e beencorrectcd for filter density. The gamma dos-age \'aries with the square of the distance andit is, therefore, ploLLed with a IOi',aril/mlicordinate.

Figure 3 illustrates the direct logarithmicrelationship of panchromatic film (Tri-X)dcnsity exposcd on 14 Junc to the gammagradient. Density of infrared film on this

DDISITO~IETRY

To quantitize furthcr the relationship hc-twccn the gamma gradicnt and the photo-graphic imagc. the processed rilm was scanned\\ith an f\'\SCO Model 4 Microdensitometcr.i\ Iicroscopic optical transmission densi ty wasrecorded by this instrument.."\n effectivecircular aperture of 40 micron diameter \\'asfou nd most satisfactory for portraying in-formation content \\"ith minimum noise due togranularity. This apcrture sizc rcsults in ancffecti\'e ground resolution about the arca ofan average oak leaf. Thc scan rate was suchthat this diameter was equi\'alcnt to approxi-mately 1 mm. on thc strip chart. NaITO\\'band-pass fil tel's (8 millimicrons) at the pcaksensitivity of the thrce color film layers (435,545, 645 1llJ-L) \\'ere uscd to measurc color den-sity of the bluc, grecn and red emulsionlaycrs.

The effcct of gamllla radiation on thisecosystem can be derivcd frolll aerial photosby graphing density \"alues yersus distancefrom the source. Threc ordinates are used inFigures 3 through 6 for comparison purposes.:-\s the panchromatic and infrared films arenegati\'e materials, their ordinate is scaledwith increasing density values. These valueshave been corrected for base level density.

pcars as a dark arca surrounding thc sourcc inall in frarcd cxposu res.

1I10:\lTORI:\G H"\DIO"\CTI\'I': CO'\T.\\1I N"\TlO:\ TO \TG""J'.\TION 989

t;AMIIIA SIIADIEMT, r/tI.,

'.-

24 May

...

Panchromatic FilmThre. Oat••

- ........'-\

'"~ 25Sopl~

'-----"""\14 June'\....

"--•50 '---~-_:_':___=_L-_::":____:::-:--:-:=--:-:-:-___:_:20 40 60 80 100 120 140 160

III.tTA,er 16011 SOU6C£" MITF6S

~ 1.90~

~ 1.70

~ 1.50

~ 1.30~ 1.10....

~ .90i::~ .70

Panchroma/ic

Tri-X & I R vs Gamma Doseage21.90~~ 1.10

~ 1.50 "

~ 1.30~ 1.10

I,\ ,

.... \,~ .90 \ Ii:: \1

~ •70t..·/,.50 ---::1.'::-'0---::Z:":.8~5;-:.2:---;1:=-8 --;;84;-'.-;:1Sa=-·8.:.3o..----·2~0·70

FH;. 4. Transnlission density of infrared ;lnd pan-chromatic Ijlm in relation to g'lnlnl'l dosage.

FIG. 6. Transmissioll dellsity of panchromaticnegatives exposed on three dates over the gammafnresl.

FI(;" 5" Tran'mission den,il'" of three ('olors inI-:ktarhrolne lilm "long the g:lmll1a gradient ex-po'ed 25 1\1"y 1963 over the gamma forest.

same date illustrates an in'"erse relationshipLO radiation intensity" The pronounced de-parture of the density trace at 130 metersidentifies the location of a fire lane in ,,"hichyoun~ pine predominate" The relationship ofradiation intensity to density of this negati'"eis sho""n in figure 4" Color densities for thesame nate are represented in Figure 5.

In three emulsions eXfJosed on the samedate, a high positi'"e correlation of '"eg-etationresponse wi th fJanchromat ic and color filmdensi ty and a high negati ,"e correia tion ,,"i thinfrared film density is apparent from 30mcters to 80 meters" This corresponds togamma dosage rates of 601' (roentgen) to5"21' per 20 hI' day..-\bo'"e this Ic'"el radiation,,"as sufhcicntly intense to kill all ,"ascularplants" Bela,," a dosage of 5"2r/day opticaldensity decreased to a le,"cl corresponding- to

\)

~"" 1.00C>.. 1.20......~ 1.40illQ 1.80....'(IJ 1.80i::~2.00

()

Ektachrome - 3 Filters25 May

.,rlled

20 40 60 80 100 120 140 160II/STAler 160M $OV6C£" MITF6S

a dosage of 2r/day, beyond which little corre-lation was apparen t and no damage to ,"ege-tation lI"as dctected on the ground" Thefluctuating dcnsities (Figure 5) bet""een 60and 90 meters rcprescnt the opcn "fringeforest" in which the densitometer ,"ie""salternating tree crOIl"ns and inten"eningshado,,"s. 1n the undisturbed forest thisshadow effect is less ob,"ious because of theclosed canopy.

How docs phenolo~y influence these rela-tionships) .-\s ,,"as obsen"ed in qualitati'"einterpretation of the phoLOgraphs the bestcontrast het""cen irradiated and normallorest occurred during the height of leaf ex-pansion in mid-June. Earlier phenologicalstages had less pronounced density gradientsand late summer conditions ,,"ere e,"en lesscontrasty" These relationships are repre-sented in Figure 6, for panchromatic nega-ti,"cs on 24 J\lay, 14 June, and 25 September.The uniformity of the density change withdistance from the source is a function of (1)the original yegetation homogeneity and (2)equal densitometry along all radii" :\ssuming,the original '"egetation was homogeneous,density traces of opposite radii from the samenegati,"e arc plotted in Figurc 7 to comparetreatment response in different radii" Radius5 is the path scanned for all pre,"jous illustra-tions; on this scan a light-colored trail at 90meters and a dark shad 011' at 100 meters ac-count for the sharp fluctuations"

Sl'~D1ARY

Utilizing qualitati,"e and quantitatiye in-formation deri'"ed from aerial photographs, aunique ecological problem has been e\"aluated"[s it possible to detect gamma radiation from

990 PHOTOGRAMMET1UC ENGINEE1Ul\'G

FIG. 7. Relationship of transmission density alongt,,"O radii of the same negative.

.10 ~-'---:c':---:'::-::':-~~:7:-~-=-0-:"'.16020 40 10 80 100 120 14

lIlTlItE "tI. ItlVleI /I .HEII

the aerial photographs alone? Given a homo-geneous Yegetation background on le\"el ter-rain, a competent photo interpreter couldanalyze a point disturbance exhibiting ap-paren t decreasing response wi th distancefrom that point. Shielding effects from treetrunks or terrain \I"ould confirm this distur-bance as ionizing radiation. Terrain shieldingis emphasized on C-D film. Assuming thatsome information on the plant speciesaffected could be discerned from the pho-tography, further confirmation and an esti-mate of the size of the source could be in-fen"ed by com paring chromosome nu m berand size with their apparent lethal distance.

Each of the four emulsions has contributedslightly different information. For qualitati\"e

interpretation, color film is preferred; C-Dfilm emphasizes the response of the sedge andshrub zones to shielding or radiation shado\\"s"There is SCHne suggestion that oak canopies inthe "fringe" area are dying, hut this is notclearly unique to C-D exposures" Infraredfilm, filtered to exclude \"isual \\"a\"elengths,was \"ery contrasty Ilecause of the strong ab-sorption of in frarer! wayelengths by the deadand decaying Yegetation and the equallystrong reAection by li\"e tree crowns. Pan-chromatic film \\"as the fastest emulsion usedand was exposed \\i th the slOllest apparen tmotion and therefore appeared to ha\"e thegreatest resolu tion.

E\"aluation of these emulsions for opticaltransmission densitometry is the most en-couraging technique for expression of quanti-tati\'e \'alues, particu]arly of color imagery. Itis possih]e to express the data so obtainedeither as arbitrary three-filter integral den-sities, or to transform these expressions intothe C.LE. tristilllulus coordinate (S\\"eet,1952) system of color space notation.

REFEREl\CES

Hardy, Arthur C. 1936" "Handbook of co]orimc-try." 1\1.1.'1'. Press, Cllnbridge, 87 pp.

Sweet, 1\lonroe H. 1952. "Color Ijlm an,lIysis fromintcgral dcnsity data." J. Optical Soc. _111Ier.'+2: 232-237.

SpaITO\\", A. J-l. and G. 1\r. \\'oodll"ell 1962. "Pre-diction o[ thc scnsitivity o[ plaids to chnlllicgamma radiation." Radiation Bo/any 2: 9-26.

\\"oodll"ell, Ceorge 1\1. 1962. "Effects of ionizingrad ia tion on terre:;trial ecosystems." Science138: 577.

Woodwell, Georgc 1\1. 1963. "The ccological effectsof radiation." Sci. Amer. 208: 40-49.

,,,

Panchromatic Film - Two Radii24 M~y

/-~~~~~~?\

"

21.10~

~ 1.70

~ 1.10..~ 1.301MQ 1.10...~ .90i:~ .70