The development of an airborne remote laser fluorsensor for use in oil pollution detection and hydrologic studies

THE DEVELOPMENT OF AN AIRBORNE REMOTE LASER FLUOROSENSOR

FOR USE IN aIL POLLUTION DETECTION AND HYDROLOGIC STUDIES

TECHNISCHE HOGESCHOOL 8!Lf\

VUEGTUIG&OUW~UHDI

BIBUOTHEEK

Prepared for the

Canada Centre for Remote Sensing

DEPARTMENT OF ENERGY, MINES AND RESOURCES

ti

f

'

,

(

'7

OTTAWA

4, ONTARIO

December, 19710 by Dr. R. M. Measures Principa1 Investigator Associate Professor and Dr. M. Bristow Research Associate

=

Page 16 ~ Table 11

ERRATA SHEET

Report No. 175

by

Dr. R. M. Measures and Dr. M. Bristow

APPROPRIATE FLUORESCENT CONVERSION COEFFICIENTS

Calcium Rhodamine Thick Oil

1ignosulphonate BN Film

Threshold

concentration (2 mgm/litre) (4.5 !lgm/litre)

,

>

10 !lm

Wavelength 4254°A 5676°A 52100A

C~OTAL(À)~[i~OAJ

1.02 x 10-5 3.32 x 10-6 7.50 x 10 -6

C~ATER(À)~[i~~OA

J

2.42 x 10-6 1.18 x 10-6 <2 x 10-6 ~

I

Correction ?

THE DEVELOPMENT OF AN AIRBORNE REMOTE LASER FLUOROSENSOR FOR USE IN OIL PO~LUTION DETECTION AND HYD~OLOGIC STUDIES

December, 1971.

Prepared for the

Canada Centre for Remote Sensing

DEPARTMENT OF ENERGY, MINES AND RESOURCES OTTAWA 4,qNTARIO by Dr. R. M. Measures Principa1 Investigator Associate Professor and Dr. M. Bristow Research Associate

Institute for Aerospace Studies

University of Toronto

SUMMARY

The first phase of a development programme devoted to the exploitation of laser induced fluorescence for environmental sensing has been completed. A

prototype Laser Fluorosensor has been constructed and used to evaluate, in the laboratory, the feasibility of this concept and to explore the potential range

of applications. Special attention has been given to assessing the ability of

a Laser Fluorosensor to map the extent of an oil slick, locate the source of lignin sulphonate pollution and monitor the dispersal of a tracer dye for

hydrologie uses. The preliminary results of our study are very encouraging and leads us to predict th at

a

Laser Fluorosensor could be used for environmental sensing from an aircraft flying at between 1000 and 2000 ft. on a 24-hour basis.

I.

11. 111.

N.

V.

TABLE OF CONTENTS INTRODUCTION

THEORY OF THE LASER F:):.UOROSENSOR

I I . l

11.2 11.3

Fluoreseenee

Radianee Due to Fluoreseenee Signal to Noise Consideration PROTOTYPE LASER FLUOROSENSOR

RESULTS AND CONCLUSIONS IV.l

N.2

N.

3

N.4

N.5

Oil Sliek Mapping

Results of Hydrologie Interest and Water Fluorescence

Water Pollution and Chlorophyll Monitoring Geophysieal Surveying

Signal and Noise Considerations Based on Experi-mental Data

RECOMMENDATIONS FOR PRASE 11 REFERENCES FIGURES

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PAGE 1 1 1 2

5

8

12 12

1

3

1

3

1

4

1

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17

18

. . - - - -- - - -_ ..

-I. INTRODUCTION

The purpose of this programme is the development of a new form of remote airborne environmental sensor termed a Laser Fluorosensor. The opera-tion of this instrument hinges upon the ability of a short wavelength laser to induce fluorescence i~ a wide variety of materials • The laser radiation is absorbed by the irradiated material, raising the molecules concerned to an excited state from which they can decay with emission of long er wavelength radiation which can be detected by a suitable receiver mounted adjacent to the laser. The high intensity and narrow beam of the laser enables both long range monitoring and precise location of the fluorescing source. Furthermore, this type of active remote sensor lends itself rather well to 24-hour sur-veillance and is, consequently, especially well suited to patrolling the Northern regions of Canada.

The proposed laser fluorosensor would essentially comprise a suitable high power pulsed laser to excite the material of interest and a sensitive photodetection system to observe the resulting fluorescence signal. Hemphill, Stoertz and Marklel have discussed the possiblity of using solar induced fluorescence for the purpose of remote sensing of the environment. Their technique relies on solar radiation to both excite the fluorescence and

set the stage for its detection. Their instrument, called a Fraunhofer Line Discriminator, uses the change in depth produced in the Fraunhofer dark lines of the reflected solar spectrum compared to the depth of these lines in the incident solar radiation.

Unfortunately, this technique suffers from three major drawbacks, good sensitivity is achieved only when there is little cloud, the technique cannot be used at night and the main source of background noise is also the exciting source. The Laser Fluorosensor does not suffer from any of these limitations as the exciting source is a beam of laser radiation. The essential components of the proposed Laser Fluorosensor are schematically illustrated in Fig. 1.

The scope of Phase I included the design and construction of a prototype model of the Laser Fluorosensor and the subsequent assessment of the viaoility of the concept. This has been done by setting up a target at a range of 24 feet and irradiating a number of samples with the beam from a Q-switched ruby laser operating at its second harmonic frequency. The f luo-rescence profile resulting from exposure to the laser radiation has been mo ni-tored and t he magnitude of the fluorescent radiance has been estimated. This has been related to the power density of the incident exciting radiation in terms of an effective fluorescence cross section. Determination of this cros s-section enables calculations to be made on the full scale system and thereby predict the potentialof a given application.

II. THEORY OF THE LASER FLUOROSENSOR II.l Fluorescence

When a molecule is exposed to radiation of a suitable frequency there is a certain probability that the molecule will absorb a quantum of ele ctro-magnetic energy and subsequently be elevated to an excited state. The excited molecule may return to the ground state by a number of decay modes, two of which result in the emission of a quantum of electromagnetic energy having a

somewhat lower frequency than the exciting quantum. These processes are

illustrated in Fig. 2.

In the condensed state the excited molecule can relax to the lowest

vibrational state of the excited electrönic state by a rapid non-radiative

process termed, "internal conversion" • Once in this level the molecule may

undergo; either a radiative decay to some vibrational state of the ground electronic state or a non-radiative transition to a long lived state. The former process is called "fluorescence" and in most instances has the higher probabili ty. The latter process is referred to as "intersystem crossing" and

results in the molecule being shunted to an intermediate level from which it

may subsequently decay by the emission of a photon. This process is then

termed phosphorescence. The disparity in the lifetimes of the two forms of

radiative decay is clearly evident in the relative strengths of the two forms

of emission. Consequently, fluorescence having the shorter lifetime has the

greatest probability of occurrence. In fact in almost all instances we shall

be quite justified in neglecting the contribution arising from phosphorescence.

11.2 Radiance Due to Fluorescence

In order to arrive at a parameter that may have general

applica-bility in determining the magnitude of the fluorescence signal that we may

expect from a variety of different mediums we introduce the general model illustrated in Fig.

3.

We assume that a

radia~ive

flux

pt

(watts cm-2) is incident normally o

to the surface of a semi-infinite fluorescent medium and that we may use a

one-dimensional approach. We shall neglect reflection losses suffered by the laser beam at the air-medium interface although we shall take account of this

fact wh en we consider the background noise. If at a depth Z within the medium, the exciting radiative flux, p~(~) is given by

t

~

(z) =

~

e - E z (11.1)

o

where

~

t

is the extinction coefficient of the medium at the laser wavelehgth. Now in general

(11.2)

where

t

E is the extinction coefficient associated with the constituent

0;

of interest and

t

is the extinction coefficient of the background medium

E~

E is the scattering contribution to the extinction coefficient. s

The amount of fluorescence in the wavelength interval (À,6À) that emanates from a unit area of a thin slab of thickness 6s, at a depth zand reaches the air-medium interface is

where

~

F(,)

d

F(,)

va f\ an cr t3 f\ are the effective fluorescence cross-sections per unit

wavelength at À,

are the respective densities of the constit~ent of

interest and the background medium and,

are the respective mean extinction coefficients in the fluorescing wavelength interval (À,6À)

for the constituent of interest and the background medium.

Let us introduce E(À)

=

Ea(À)

+

E

t3(À) as the total extinction coefficient in the

wavelength interval (À,6À) then the total laser-induced radiance emanating from the air-medium interface in the wavelength interval (À,6À) is given by

in which case

(11.5)

of interest is confined to a finite layer of

p! Cl t3 F (À)N t3exp [ - {Et3(À) + Et3$ } d ] 2{Et3 (À) + Et3 $ }

(n.6)

If the fluorescence at two wavelengths Àl and À

2 is considered we may write for

the infinite medium case

{ClaF(Àl)Na + Cl t3 F (Àl )Nt3 }p! 2

1

E

(

À l) ) +

E$}

(11. 7)

and { cS(À2 ) Na + F N } p.e

vr(À

₂)

crl3(~2)

_{13 0}

=

(IL8) 2 {E(À2 )

+

E.e

}

In general it is reasonab le to assume E(À) « E l.n w l.C .e. h· h case [Na

{er~

(:\

)

-

cr~(À2)}

+

NI3{er~(Àl) -cr~(À2)}

] p! vl'(À

l )-vI'(À2)

1

'::::

2E] (IL9)

Moreover, we can express the effective fluorescence cross-section, erF, in terms of an absorption cross se~tion,

erA,

and a quantum yield factor, ~, which can be defined as the number of fluorescent photons emitted into unit solid angle, at wavelength À, for each laser photon absorbed by the relevant medium, viz;

and if further we use this in equation (II.2) then we may write

E S

(IL 10)

(II.ll)

If Àl and À

2 are chosen such that,

~aF(À2)

«

~aF(~),

yet

~I3F(Àl) ~ ~I3F(À2)

then the background fluorescence can effectively be subtracted out to give

(II.12)

There are several possi~le sit11ations that may ~ise in practice. We shall res-trict our attention to three limiting cases th at are likely to be of particular interest.

CASE A

The extinction coefficient is dominated by scattering, but background fluorescence is negligible. Under these circumstances we have two unknowns, Na and E , and only one effective equation

s NerF (À)P.e

rl'(À)

= a a 0 (IL13)

2E s

so that the absolute value of Na cannot be evaluated. However, the relative density profile of the constit~ent of interest can be determined. If the concentration is

sampled at one point then the actual spatial distributioB can be rapidly assessed

using this technique, pr01iding we can assume that E is the same over the region of interest. If E does vary with location, then it~ value may be estimated from

s

CASE B

The quantum yield factor for the background is much smaller than for the constitrent of interest, at the approximate wavelengths, yet its absorption characteristics dominate the extinction coefficient. In this case we are

neg-lecting the scattering contribution to the extinction coefficient. In particular

we assume that

and so we may write equation (11.12)

A

if (

À)

~

1

Na

era 2 A N~er~ in t,he form (II.14) Consequently, if the

centration NajN~ can

t "

Fj

A

ra lO, era er~, and the quantum yield is known then the con

-be determined. CASE C

If both the quantum yield and absorption characteristics of the con

-stitvent of interest dominate the background, then

J'(À) -N er

~it

cp F(À) g~ 0 <a (11.15 ) " it 2Ea or pit (j) F(À)

v1

(À) '::: o a 2

and although the sizeable fluorescence signal may be attained, it contains no

in-formation abqut the concentration of the material of interest. A thick layer of

oil is a good illustration of this case. In this mode of operation only the

spatial extent of the constituent is of concern, EO that it is sufficient if there

is a significant change in the fluorescence signal as the monitoring platform

passes over the boundary of the substance. However, good temporal resoluyioR

will give some indicatio~ of the concentration.

11.3 Signal to Noise Consideration

If the fluorescence emanating fram the air-medium interface is assumed

to be Lambertian, then the total fluorescence flux received by the detector in

the spectral interval, 6À, is given by

( 11.16)

where

n

is the solid angle that the detector subtends at the surface. A is the

area of the &urface viewed and s(À) is the transmittance factor for both the

atmosphere and receiver optics of the system, including the filter defining the

spectral interval 6À. We are assuming that the system has been optimized _I so that

the total output power of the laser is

pt,

then since in general we can write WF(À)

=

cF(À)

pt

o

(II.17)

it follows that we can express equation (II.16) in the form

(II.18)

where CF(À) is the appropriate conversion function and

~T

is the transmittance factor for the laser beam. That is to say we are assuming

Ar!

_o (I1.19)

If the Laser Fluorosensor is operating at an altitude Rand the limiting apertlire , of the system has a radius a, then

(IL20)

If the Laser Fluorosensor is to be operated on a 24-hour basis then invariably its sensitivity will be background limited. Under these conditions the two main sources of noise will be scattered and reflected solar and laser radiation. Temporal and spatial filtering can be used to discriminate against the mean component of the solar radiation and spectral filtering can be used to discriminate against the back-scattered laser radiation.

For a downward looking system at an altitude of some hundreds of meters it is reasonable to say ~hat only surface scattering is significant, and that the contribution to 4he background noise from Rayleigh and aerosol scattering in the atmosphere is negligible. Under these circumstances the background signal will arrive at the photo cathode at the same time as the fluorescent signal so that no form of range gating can be used to reduce the background contribution.

If we assume, for simplicity, that we are not in the first instance interested in spatial resolution within the fluorescent medium and that conse-quently the bandwidth of the detector system is made comparable to the pulse duration of tpe laser, then it follows that the number of photoelectrons created by the fluorescent pulse of radiation

where

N F = TJ(À)

e

TJ(À) is the photocathode quantum efficience at wavelength À

T is the integration period of detector system

hv is the mean energy of the photons in the spectral interval

(À,6À).

(IL21)

The corresponding number of photoelectrons that are generated by the solar background incident up on the photocathode during the same time interval is

.

wherè

N s

=

e (II.22)

(I1.23)

,(À) being the albedo of the surface and B(À) the solar flux incident upon th$ earth's surface~ at wavelength À. Now if the divergence of the laser

beam ·iS,18 then, A '::: (R8 )<::7T and so

S~

(I1.24)

If , t'is the albedo of the surface at the laser wavelength, then the number of

photoetectrons created at the photocathode by scattered and reflected laser radiation is

'

.

.

N t

e (I1.25)

where

~tis

the quantum efficiency oftthe photocathode, and hv

t

is the energy of a

phbton at the laser wavelength.

ç(À)

includes the spectral discrimination factor

arising from the use of an appropriate narrow band filter.

The mean component of the solar background signal can be eliminated by temporal filtering. This means that only the fluctuations in the scattered

solar radiation will have to be taken into account. If we assume that the burst

of photoelectrons is described by Poisson statistics, then the root mean square

number of photoelectrons arising from the solar background is just equal t·o the

corresponding square root of the mean number of photoelectrons. Hence the effectixe solar noise number of photoelectrons

or

L:ili s

e (I1.26)

(n

.27)

If the spectral filter is sufficient to eliminate the laser returned signal, then the signal to noise ratio of the Laser Fluorosensor will be given by

SNR(F/S)

NF

e

=

L:ili S

=

e

Conversely, if the laser return dominates the background then

(I1.28 )

and so fQr a given value of SNR(F/~) the required filter rejection ratio

~(À)/~(Àt) can be determined.

Finally, the ratio of the solar to laser background is

(11.30)

From this equation we can ascertain which form of background will dominate under

a given set of conditions.

111. PRararYPE LASER FLUOROSENSOR

A schematic diagram of the experimental system is shown in Fig. 4 and

photographs of the prototype laser fluorosensor and fluorescence sample target

tray are shown in Figs. 5(a) and 5(b) respectively.

The ruby laser system consists of a TRG 104A laser head and integrally

mounted second harmonie generator with the addition of a passive Q-switch and

TIR prism as the rear reflector. Satisfactory Q-switching was achieved using

Eastman Kodak Q-switch solution No. A10220 (7.2 x 10-5 M stabilized solution of

cryptocyanine in acetonitrile) further diluted in acetonitrile to a 2.2 x 10-

6

M

solution in a 1 cm path length spectroscopic sample cello With this system,

fundamental power levels of the order of 5-15 Mw were obtained with pulse widths

(FWHM) of about 15 nsec. The corresponding seco~d harmonic pulses at 34710A for

stimulating fluorescence were of the order of 0;.2 - 0.7 MIl in amplitude and pulse

widths (FWHM) of about 12 nsec. The fundamental laser radiation at 69430A was

eliminated from the output-beam by absorption in an 0.8 cm path length cellof

satura~ed copper sulphate (CUS0

4) solution.

With a view to monitoring the power of the second harmonic, a small

percentage of the beam was sampled using a beam splitter placed at 450 to the

incident beam direction. The splitter plate consisted of an approximately 1 mm

thick piece of Schott UG 11 filter glass which at an angle of incidence of 450

has a transmission of about 75% at 34710A while blocking all visible radiation.

It therefore serves to prevent any laser flash lamp pump radiation from entering

the fluorescence emission detection system. Moni~oring the power of each second

harmonic pulse was found to be necessary as the amplitude exhibited at + 40%

variation from shot to shot. This necessitated the prior calibration of the

monitoring photomultiplier (EMI 978lA) against an energy meter (TRG10l Ballistic

Thermopile) so that knowing the pulse FWHM, the peak amplitude and the pulse

energy, the peak pulse power is known. A narrow band interference filter centered

at 34710A was used to prevent any flash lamp or residual fundamental radiation

reaching the monitoring photomultiplier. The ground glass diffuser shown in

Fig. 4 served to ensure an even distribution of the U.V. radiation over the

photocathode in order to accommodate for shot to shot variations in the spatial

distribution of the laser beam. It should be noted that the magnitude of these

inhomogenei ties becornes somewha t enhanced by the square law dependence of the

second harmonic radiation on the frequency doubling process.

The second harmonie beam of approximately 1 cm diameter is then passed

through a diverger lens such that it strikes an approximately 12 in x 8 in.

19-in. diameter front surface mirror (overcoated with magnesium fluoride to prevent

oxidation). The location and positioning of the 12 in. x 8 in. exposed area was

facilitated using Kodak Linagraph Direct Print Paper Type 1895. This U.V. sensi-tive recorder paper gave an excellent indication of beam position and size when

developed by exposure to direct room lighting.

The stainless steel fluorescence sample target tray (see Figs. 4 and 5(b)) was chosen both because of its resistance to corrosion and because of its

low background fluorescence signal level af ter pickling in nitric acid solution. In addition, domestic aluminum cooking foil was fo~d to provide a good low

fluorescence level background material. However, without special cleaning

preparations both materials gave background fluorescènce signals which were typically less than 1% of that from a 5 cm deep tap water sample. All non-metallic and particularly organic materials, e.g. wood, paper, paints, white

enamel, etc., were found to give relatively large fluorescent signals and were

therefore avoided.

It should be noted that both aluminum foil and stainless steel sheet

are relatively good reflectors of both the ultra-violet excitation radiation

(~ 50%) and visible fluorescence radiation

(z

70%). Consequently when dealing

with either oil films on water or with dilute water solutions in depths of the

order of 5 cm where the internal transmission is almost 100%, a considerable percentage of both the excitation and emission radiation will be reflected back up through the oil film or solution as the case may beo This situation is

therefore not typical of that existing in the field where the depth of the

river, lake or ocean will be considerably greater than the equivalent absorption depth for radiation in this region of the spectrum. Because of this there is some uncertainty as to the relative percentages of back reflected fluorescence

emission and U.V. excitation radiation which stimulates further emission on

re-flection and consequently it is desirable to 'dump' all radiation striking the

background supporting system. Attempts to find a suitable radiation sink for use as a background have so far not been successful so that all the present

experiments were performed using either an aluminum or stainless steel background.

\ A sheet of abraded black butyl rubber was found to generate a fluorescence slgnal

which was less than 10% of that for a 5 cm deep tap water sample at 52100A.

Other materials are c~rently being investigated using either optical absorption or geometrical optics arrangements.

The fluorescence detection system is mounted adjacent to the laser system (see Figs. 4 and 5(a)) but during an experiment is carefully screened

to prevent direct exposure to either flash lamp pump or U.V. radiation. The single component optical-glass detector lens (4-in. diameter aperture x l3-in.

focal length) and the photomultiplier (EMI 978lA) are carefully aligned so that

approximately 90% of the fluorescence emission image of the sample formed by the lens, covers the photocathode. In order that an absolute value of the

fluorescence emission can be obtained, i.e., in ~W/sq. cm. of sample/500A band-width, it is necessary to know the overall photemultiplier sensitivity as a

function of wavelength in mA/watt. In this instanee this informat~on was supplied

by the manufacturer although in future it is planned to calibrate the system in order to eliminate errors due to possible deterioration in the tube per-formance with use.

Interplaced between the detection lens and photomultiplier are three

filters of accurately known transmission characteristics. The ultra-violet

transmits greater than 84% at all visible wavelengths greater than 42000A. At

34710A, this filter has a transmission of

<

10-5 • Each narrow band interference

filter used to select a particular region of fluorescence emission for ex~na­

tion, was carefully calibra~ed to obtaiq the bandwidth (FWHM) and peak transmission

characteristics which in

ge~eral

had

valu~s

of the order of 600A and 70%

respec-tively. The function of the narrow band filter was originally performed by a

grating Monochrometer (Heath Series 700 Scanning Monochrometer) but this was

found to be unsuitable because of the shot to shot variations in the spatial

intensity distribution of the approximately 1/2-in. wide x 3/B-in. high

fluo-rescence image. This was caused by spatial variations in the laser second

harmonie beam (as previously mentioned) and resulted in inconsistencies in the

experimental data that could not be easily eliminated. This problem will not~

however, occur in future as all spectral fluorescence investigations in the

lab-oratory are to be performed using either a spectrofluorometer or our prototype

Laser Fluorosensor with a series of narrow band filters to simulate events

occur-ring in the field. The attenuator which takes the form of a spectral~y

cali-brated (near) neutral density absorption filter is necessary tp ensure that the

fluorescence emission signal (a) is of a similar magnitude to that of the

moni-tored U.V. laser excitation pulse so that direct compariso~ is possible using a

differenti~l rertical oscilloscope amplifier, (b) is not so large as to be in the region of photomultiplier non-linearity.

Typical U.V. laser excitation and visible fluorescence emission pulses

are shown in A-B mode on the oscillogram in Fig. 6, as obtained using a Tektronix

556 oscilloscope and a type lA5 High Gain Differential Amplifier plug-in which

have a combined system risetime of less than 7 nsec. to a step input signal. The

first aqd lower pulse (A1 is that for the U.V. excitation which provides a value

for the peak pulse power obtained via the known calibration factor. The second

and upper pulse (-B) is that for the fluorescence emission where the time lag

between pulses corresponds to the difference in time of arrival of the two pulses

at their respective photomultipliers. For any given experiment corresponding

to a sample of known concentration and to the observed fluorescence emission

wavelength À , the quantities obtained from the oscillogram were V

L the peak

voltage corresponding to the U.V. excitation pulse, V

F the peak voltage

corres-ponding to the fluorescence emission pulse~

TL

the excitation pUlse FWHM and

T

F the fluorescence emission pulse FWHM. The quantity which is of prime interest

is (VF/V

L) which was found to be independent of VL' i.e.~ no power saturation

effects were observed for the samples examined up to peak excitation power

densities of 1120 watts cm- 2 • Consequently, it was possible to present all

the values of (VF/V

L) for a value of VL corresponding to the typical peak power

level of 0.5 MW or Beo w/cm2 of fluorescence sample from which the absolute

fluorescence emission in ~W/cm2/50oA was calcvlated.

It is now pertinent to discuss a number of points regarding the

pre-paration of the various fluorescence samples. It was immediately noticed that

tap (drinking) water gave a relatiyely strong fluorescence signal throughout

the blue-green spectrum. The intensity of this fluorescence was found to

increase linearly with depth up to at least 14 cm and also to vary from day to

day (+ 25%) presumable due to variations in the concentrations of the impurities

responsible for this fluorescence. In general all water and water solutions

were maintained at a constant depth of 5 cm.

---~--~~~~~~~~~~~~~~~~~~~~~~~

~~~~-~~-~----rhodamine BN dye (Canadian Industries Ltd) solutions were made up directly in tap water. However, 'with the chlorophyll extract (Matheson, Coleman and Bell) which is composed of chlorophyll types a and b in the ratio 2.5:1 in a 4% by weight diethyl ether solution, it was first necessary to dilute the extract in

acetone prior to gross dilution in water to the desired concentration. It

should be noted that the chlorophyll fluorescence experiment was performed using a long wave pass filter rather than a narrow band interference filter. Con-sequently the observed backgropnd water fluorescence signal for this experiment

is the total integrated background fluorescence for all wavelengths greater than the filter cut-off value out to the long wave transmission limit of this filter at 2.75~. The long wave pass filter used was a Corning type CS 2-58 which has a relatively steep cut-off with a 50% transmission point at about

6500oA. The filter therefore transmits about 85% of the 2000A wide chlorophyll fluorescence emission band centered at about 6700oA. However, it should be

mentioned that the background fluorescence for water at wavelengths greater than 67000A will generate .only a small signal in the photomultiplier d~e to the rapid fall-off in the spectral sensitivity of the modified S-5 photocathode

response for the EMI 978lA photomultiplier for increasing wavelengths in the

red region.

MATERlAL OBSERVED FLUORESCENT PULSE

F==========================*======HALF====W=ID=T=H~L,==TF~a==(n=s=e=c==)======~~

Film of Light Crude Oil on Water

(Rainbow, Alberta)

Water

Rhodamine BN in Water

Chlorophyll Extract in Water

Calcium Lignosulphonate in Water Scapolite (Kilmar, Quebec) 17 16 < 15 < 71

a

=

Combined Laser and Fluorescence Pulse Width (FWHM)

b

=

Laser Pulse Width (FWHM) ~ 12 nsec.

TABLE I: FLUORESCENCE PULSE HALF WIDTHS FOR SEVERAL MATERIALS IN RELATION TO THAT FOR THE

LASER EXCITATION PULSE

The scapolite rock sample (L. I. Cowan Minerals Ltd., Barrie, Ontario)

originates from Kilmar, Quebec and exhibits bright yellow fluorescence wh en ex-posed to long wave U.V. radiation from a 'black light' type fluorescent tube.

The scapolite itself was supported in a matrix of non-fluorescent rock of unknown

~omposition and was estimated to constitute about 40% of the total rock sample.

small pieces and evenly distributed over a piece of aluminum foil so as to over~

lap the 12~in. x 8-in. target area.

The oil-on-water films were prepared by dropping a known volume of

oil (light crude fromRainbow, N. Alberta) onto the surface of a

5

cm. dep~h

of tap water in the 21-in. x 17-in. stainless steel target tray. Within 1 to

2 seconds, the oil was observed to spread out to form a uniform film of known dimensions. The film uniformity and dimensions were gauged by observing the spreading process under long wave U.V. illumination which makes the oil film highly visible by virtue of its strong characteristic'yellow-green fluorescence.

Hence, knowing the initial volume of the oil and the area of extent of the oil

film, it was possible to obtai~ an approximate value for the film thickness. Dl. RESULTS AND CONCLUSIONS

The prototype Laser Fluorosensor described in Section 111 has been used to make an exploratory investigation of the fluorescence properties of

a number of materials of interest. Oil films on water have been studied and

the results obtained certainly indicate a rich area of work to be further

studied. ~etection threshold concentrations for a variety of substances found or used

in loc al sources of water have been evaluated; these include calcium

ligno-sulphonate, rhodamine BN and chlorophyll. Although the results attained to

date have been preliminary in nature, they are nevertheless encouraging.

Dl.l Oil Slick Mapping

The fluorescent properties of crude oil are well known2 although very little detailed information is to be found in the open literature. We

have examined several samples of crude oil th at have originated from a number

of sources, and found them all to fluoresce. A typical light crude oil

(Rainbow,_ Alberta) was chosen for detailed study. The fluorescent signal produced by oil films (on tap water) of different thickness was measured and

the results shown in Fig. 7. It is clear from these observations that over

the thickness range 0.3 to 5 ~m the fluorescent signal appears to increase

linearly with oil thickness. It is also evident from this figure that the fluorescence signal saturates for film thickness in excess of about 10 ~m.

The primary cause of this saturation is believed to be strong absorption of the exciting laser radiation within the oil film. This is borne out by the

absorption cross section determined for this type of oil in a separate

absorp-tion experiment.

o

Unfortunately, excitation at 3471 A tends to excite fluorescence

in the water. This laser induced fluorescence of water appears to be the

dominant source of background in the present experiments and is likely to

limit the sensi tivity of the system to be below what one might calculate on

the basis of solar back§round. It is well known that radiation of wavelength

greater than about 4200 A generates almost no fluorescence from water, yet

is still effective with oil. Consequently if we were to adapt our Laser

Fluorosensor to operate with a dye laser providing peak power at about 4300oA,

this limitation could be greatly improved.

The fluorescence variation with wavelength for the oil sample

appears to be fairly flat for the thick oil film as seen in Fig. 8. However,

this apparent featureless spectral profile could be a result of the poor

even with our limited system it is clear that the spectral profile for a thin (4.4 ~m) film changes with time (see Fig.

9).

If this spectral change with t,ime* is well defined for a given species of crude oil, then more re-search might lead to a method of determining the time of an oil spill. It is also possible that better spectral resolution will enable identification of the source of an oil spill. See the recent work of Fantasia et a13 •

The spectral difference between the thick and thin oil films seen in Fig.

8

is probably a result of the temporal shift discussed above, since it might be assumed that a 13000A film will lose the appropriate component fairly readily. Indeed, a very definite physical change is noticed for these very thin oil films af ter just a few moments. The film appears

tp

gel and crack when disturbed.

IV~2 Results of Hydrologie Interest and Water Fluorescence

One important fact that has emerged from our experiments to date is that both tap and lake water give an appreciable fluorescence return when irradiated at 34710_{A; the radiance of the blue end of the spectrum being} nearly five times that observed at the red end. The source of this

fluo-rescence is not well known, although the recent work of Christman andGhasseni4 indicates an organic origine Moreover, it is clear from Fig.

8

that a res-idual fluorescence can be induced even in distilled water. The factor of two between tap and lake water could be a significant indicator of the purity of water and further work along this line is being pursued. There have also been suggestions that part of this natural fluorescence is due to the mineral content of the water. If this is found to be the case, then operation at different excitation, as well as fluorescence, wavelengths may enable remote analysis of lake composition.

rluorescent dyes are of ten used to measure the flow patterns in harbours, lakes and riverso In the past this has required constant sampling of the water by a fluorometer on board a boat. This technique is slowand spread over time so that its precision is questionable. The proposed, remote operated, Laser Fluorosensor could be used for this type of research with im-proved convenience. To this end we have attempted to determine the detection threshold concentration of Rhodamine BN. Figure 10 indicates the fluorescent radiance as a function of concentration for a weak dye solution. It is clear from these results that concentrations of Rhodamine BN in excess of 1.3 ~gm/

litre of tap water sho ld be det,ectable by this system at 5676°A. Reference to Fig.

8

allows us to extrapolate to lake conditions where the threshold concentration may be closer to 4.5 ~gm(litre in harbour water. Field trials will be required to determine these values in a real situation due to the

variation in the background fluorescence. Figure 11 shows that the fluorescence return is a linear function of concentration up to values of at least 10 ~gm/ litre. This data, albeit preliminary in nature, indicates that the sensitivity and speed of monitoring of the Laser Fluorosensor could make it very

competi-tive with conventional techniques of evaluating flow patterns and dispersal rates'of na~ural bodies of water.

IV.3 Water Pollution and Chlorophyll Monitoring

Lignin Sulphonates are phenolic-type sub stances that form part of

*

This change is presumably due to decay or loss of some fraction of the oil.

the spent sulphite liquor waste from the pulp and paper industry. We have been able to demonstra~e that the fluorescence return from a solution of

Calcium Lignosulphonate (CaL-S) is approximately linear up to about 12 mgm/

litre, whilst the threshold for its detection appears to ~e about 0.5 mgm/ litre. These results can be seen from Fig. 12. Thurston in his recent work has shown that the background fluorescence of streams can be equivalent to a concentration of CaL-S of about 1 to 2 mgm/litre. Consequen~ly, it would appear that the potential range of operation of the Laser Fluorosensor would permit remote monitoring of CaL-S pollution sources.

Detergents using fluorescent brighteners for enhancing laundered fabrics form one component of the pollution that is affecting our lakes and

rivers. We have made some preliminary observations of the minimum concen-tration that could be detected using laser induced fluorescence. Measurements were made on only one brand of commercial detergent (Sunlight) and it was found that the threshold concentration was about 400 ~gm/litre at 4658°A.

The chlorophyll content of a na~ural body of water can serve as an important indicator of its marine life. Monitoring of the algae blooms of

a lake can be related to the pollution level of that lake, whilst evaluation

of the concentration of phytoplankton in the sea might indicate potentially good fishing areas. We have made some initial measurements on a solution of chlorophyll a and b. The results are shown in Fig. 13. The fluorescence was monitored using a long wave pass filter (Corning) with a sharp cutoff at 65000A. It is evident from Fig. 13 that the sensitivity is likely to be rather low, and the linear range of operation is rather restricted when the excitation wavelength is chosen to be

3471

0

A. The saturation in the fluo-rescence signal observed at about 450 ~gm/litre arises from self absorption of the red emission. A considerable improvement in the sensitivity shóuld be possible if the excitation wavelength is chosen to be closer to the peak of the absorption profile for chlorophyll. This gai~ in sensitivity arises, in part due to the increased absorption cross-section of the chlorophyll but even more important is the substantial decrease in watör fluorescence created by laser radiation of wavelength in excess of 4200 A.

IV.4

Geophysical Surveying

Several rock samples were found to fluoresce, but definitive

measurements were restricted to "Scapolite" as representative of a rock with a high quantum yield when excited at

3471

0_{A. The spectral radiance of}

Scapolite as a f~ction of wavelength is shown in Fig.

8.

It is evident that its fluorescence peaks towards the yellow-red part of the spectrum and the

magnit~de of the signal is seen to be very large.

IV.5 Signal and Noise Considerations Based on Experimental Data

We can use the data discussed in the previous sections to ascertain approximately the results that are likely to be achieved in field trials. The work to date has been conducted in a tray of

5

cm depth, so we must first determine the relevant coefficients which are required in the full scale extrapolation.

In the laboratory experiments the fluid depth is finite and so we must use a modified form of equation (11.6). For a fluid of depth d, and assuming

50%

reflection from the bottom of the stainless steel tray,

(IV .2)

For the CaL-S and Rhodamine BN cases the extinction coefficients corres-ponding to the threshold detection concentrations were found to be sufficiently

small that in ~he laboratory test, where a

5

cm depth was used, equation (IV.2)

was adequate. Under these circumstances, ~aF(À)Na for each of the constituents

can be evaluated directly from Figs. 11 and 12, viz,

(IV.3)

where W~(À,d)6À is the laser induced fluorescence background irradiance from

the water at the appropriate wavelength.

In the real situa~ion the depth is likely to be appreciable and so the

infinite depth limit will, in most instances, be appropriate, i.e., p

t

~

[~F(À)N

+

~~F(À)N~

] 6À

2EX,

a

a

I-' I-'

(Iv.4)

Because of the small extinction coefficients that correspond t~ the threshold

concentrations in the two cases cited above we have used for E the value found

for coastal waters. The value of ~~F(À)N~ is computed using equation (IV.2),

with Na

=

0, and the value for

W~F(À,d)

that we measured for harbour water, see

Fig.

8.

In gener al we can write CF(À)6À

=

~(À)6À/pt

and so we can estimate

o

the appropriate values for this conversion coefficient for the two cases, with and without constituent in harbour water. The values corresponding to the de-tection threshold concentrations CaL-S and Rhodamine BN are shown in Table 11.

Also included in this table are the values for a thick oil film (thickness greater

TABLE 11

APPROPRIATE FLUORESCENT CONVERSION COEFFICIENTS

Calcium Rhodamine Thick Oil

Lignosulphonate BN Film

Threshold (2 mgm/litre) (4.5 I-lgm/litre)

>

10 !-Lm

concentration

Wavelength 4254°A 5676°A 52100A

C~arAL (À)~/{ ~~~oA

] 1.02' x 10- 5 3.32 x ₁₀ -6 7.50 x 10 -6

C~OTAL(À)~À[~~~OAJ

2.42 x 10-6 1.18 x 10 -6 2 x 10-6

We have used this data in an attempt to predict the number of photo-electrons that would be created in the photodetector of the Laser Fluorosensor by the return of the laser induced fluorescence pulse, for the threshold con-centrations of the three media of interest. Figure 14 illustrates the expected variation of this signal with altitude and compares the magnitude of this signal

to that arising from the solar root mean square background. The operational characteristics assumed for the Laser Fluorosensor are presented in Tables 111

and IV. It should be restated that the threshold concentrations are determined by the intrinsic fluorescent nature of the water~nd in these calculations we have used the values that we have found for harbour water. It should also be mentioned that Fig. 14 presents the results for single pulse operation. If a 100 pps laser is used in conjunction with a signal averager then the solar back-ground problem will be considerably diminished.

TABLE 111

LASER TRANSMITTER CHARACTERISTICS

Peak power per pulse p

t

_{6 x 105 watts}

Transmittance factor ~T 0.8

for laser beam

Beam divergence 8 3 x 10-3 rad.

TABLE IV

DETECTOR CHARACTERISTICS

Quantum efficiency 1'] 0,1

Integration time T 15 x 10-

9

sec.

Aperture radius a 12,5 cm

Optical efficiency

(including filter trans- ~(À) 0.1

mittance)

Based upon the results presented in Fig. 14, we feel that the Laser Fluorosensor may be able to remotely map oil slicks and determine regions of

high eoneentration of pollution, sueh as Calcium Lignosulphonate, fram an air-eraft flying at an altitude of between 1000 and 2000 ft. with a ground resolution of about lQ ft. The instrument eould also be used in hydrologie studies for

it eould deteet the dispersal of dyes, sueh as Rhodamine BN, down to about

4.5

~gm/litre with a ground resolution of about 20 ft.

v.

REX::OMMENDATIONS FOR FRASE 11

It is elear from the preliminary results obtained to date that laser indueed fluoreseenee has eonsiderable potential as an environmental probe. We

reeommend that the laboratory work be eontinued but that the programme be ex

-tended to eneompass extensive field trials. We suggest that a rugged Laser Fluorosensor be eonstrueted and used in stationary field trials from a mobile

laboratory. Considerable savings would be aehieved by performing the field

trials in this way, as opposed to flight trials, and yet the information gathered

would be suffieiently realistic for the various user groups to be able to appre

1. Hemphil1, W. R. Stoertz, G. E. Mark1e, D. A. 2. Riecker, R. E. 3. Fantasia, J. F. Hard, T. M. Ingrad, H. C. 4. Christman, R. F. Ghasseni" M. 5. Thruston, A. D. REFERENCES

Proc. of 6th International Symposium on Remote Sensing of Environment. October, 1969, pp.565-585, Ann Arbor, Michigan.

Amer. Assoc. Petrol. Geol. Bull. 46, pp.60-75 (1962).

u.

S. Coast Guard Report No. DOT-TSC-USCG-71-7,

June,

1971.

Jour.

AWWA,

pp. 723-741, June (1966).

REFLECTOR ---MIRROR AIR PHOTOOETECTOR SYSTEM ELECTRONIC PROCESSOR AND DISPLAY 1+----UNIT PHOTOOETECTOR SYSTEM

_____

~~Äi~E~S~LECTRONIC

INTERSVSTEM CROSSING

EXCITATION

PHOSPHORESCENCE

EXCITED ELECTRONIC

STATE

CT)

__________ -

~~~~~D

ELECTRONIC

f'IG. 2.

SCHEMATIC OF Low LVING STRUCTURE OF

MOLECULE AND BASIC KADIATIVE

Laser

Air

FIG. 3 SCHEMATIC ILLUSTRATION OF MODEL

Detector System

RUBY LASER TEKTRONX \ 556

OSCILLOSCOPE

~

POWER MONITOR PHOTOMULTIPLIER tEMI 9781 AI DIFFUSER

~

ATTENUATOR SCHOTT UGli FUNDAMENTAL BLOC~NG

----FLTER t CuS04 I _~

-~

---FLUORESCENCE SAMPLE _ DETECTOR LENS 41N - DIA. 13 IN - F. LENGTH '-UV BARRIER FILTER

FLUORESCENCE EMISSION LlNE FILTER FLUORESCENCE '" DETECTOR ATTENUATOR PHOTOMULTIPLIER tEMI 9781 AI

'""

1

'

----

-

APPROX 24 FEET

SCHEMATIC DIAGRAl'v' OF PROTOTYPE LASER FLUOROSENSOR USED INTHE LABORATORY

li'IG ...

STAINLESS STEEL TRAY 21INxl71Nx31N

FIG. 5(a)

(b)

PROTOTYPE LASER FLUOROSENSOR

FLUORESCENCE SAMPLE TARGET TRAY AND BEAM FOLDING MIRROR

FIG. 6. TYPICAL OSCILLOGRAM SHOWING 3471°A EXCITATION

(LOWER) LASER PULSE AND 4658°A EMISSION (UPPER)

PULSE FROM

4.4.

MICRON OIL FILM. SENSITIVITY

0.1

v/cm,

TIME BASE 20

nsec/crn,

TIME INCREASING TO RIGHT.

1000r---~

'-•

~ 10 o a..

•

U C ~

'"

f o :3 IL 0.1 Emission at 52101 Excitation at 3471

Ä

(800 W lcm! ,)

Lioht Crude Oil Sample trom Rainbow, Alto. Depth of Supportino Tapwater , 5cm

10

~-Signal trom Thick Opaque Layer of Oil

OU Film Thicknesl ( Microns)

FIG. 7. VARIATION OF FLUORESCENCE EMISSION FOR OIL ON WATER AS A FUNCTION OF OIL THICKNESS

o<{ 0 10 ... N E u ... ;t ::t... a:: lIJ ~ a.. lIJ U Z lIJ U (J) lIJ a:: 0 ::;) -I "-104~ __________ ~ ____________ ~ ____________________ - , 103 102 10 IÖ' 4000 EXCITATION AT 3471

A

1890 wcni2 ,

~ TORONTO HARBOUR WATER • TAP (ORINKING l WATER V OISTlLLE;O WATER

) 5 om

~mp.

' .. lh

o SCAPOLITE ( KILMAR • QUEBEC l

• THICK LAYER OF LIGHT CRUOE OIL (RAINBOW. ALBERTAl

o

o 1322 A FILM OF LIGHT CRUOE OIL ON WATER ( RAINBOW • ALTA.l

4400 4800 5200 5600 6000

WAV~LENGTH ~IÄ,

SPECTRAL FLUORESCENCE PROFILES FOR WATER, OIL AND ROCK SAMPLES

FIG. 8

140~---~

Initial Oil Film Thickness Approx. 4.4

fL ,

Excitation at 3471

Ä (

800 W cm 2 )

130 Lioht Crude Oil Sample From Rainbow. Alberta

120 100 90 80 70 60 50

I

I

I

I

I

I

I

I

I

I

t

Oepth of SlJpportino Tapwater 5 cm

0 -

17 Hours

IJ -

44 Hours

40~----~----~~----~----~---~----~---~----~

3600 4000 4400 4800 5200 5600 6000 6400 Wavelenoth À (Ä)

FIG. 9. VARIATION OF FLUORESCENCE EMISSION FOR UNDISTURBED

OIL FILM ON WATER WITH TIME AS FUNCTION OF

WAVE-LENGTH. VALUES GlVEN AS A PERCENTAGE OF VALUE AT

TIME ZERO

240~1---~

20 Oe:(

o

10 "'-ei 160

5

"'-:.

::t..

-120 ~

•

_~ Q..

I

_f

o :::J ii: 10 Excitation at 3471

Ä (

800 W / cm I ) Emission at !5676

Ä

Oepth of Sample !5 cm 102 103 Conc~mtration of Rhodamine Background of 104 BN (n gm/litre HeO)

FIG. 10. FLUOEESCENCE EMISSION FOR RHODAMINE BN DYE AT

5676X AS FUNCTION OF CONCENTRATION

..

240

I

Excitation at 3471Ä (eoow/cm2 ) Emisslon at 5676Ä 200

1

Depth of Sample 5cm

-o<x 0 10 . ' 160

§

... -~

:t..

'-•

~ 0 Q.

•

u c:

•

u

..

•

~ 0 :::J iL 12 80 40

- - - Fluorescence Background of Tapwater

I I I I I I I I I

o

2 4 6 8 10 12 14 16

Concentration of Rhodamine B N f-L gms/litre H₂0)

FIG. 11. FLUO~SCENCE EMISSION FOR RHODAMINE BY DYE AT 5676Ä AS FUNCTION OF CONCENTRATION (LINEAR PLOT)

40or---~ 1200 1000 oc::r

f6

"

800 til E u

"

31

::t.

Excitation at 3471! (800 W / cm2 ) "-CD ~ 0 Cl. CD U C 600 o Emission at 4254 A Depth of Sample 5 cm ~ 400 co 1!! o :J

u:

200

11'-'--- - - -Fluorescence Background of Tapwater

0-r---~2~----~4~---~6~---~8---~10~---1~2~----~14

o

Concentration of Ca L-S (m gm/litre H₂0)

FIG. 12. FLUORESCENCE EMI~SION OF CALCIUM LIGNOSULPHONATE

•

ocr

S

"-..

_E 0 "-~

:t

'-0) ~ 0 0-0) 0 c 0) 0 en 0). '-0 :l G: 4~---,

2

o Excitation at 3471 A· (800 W / cm2 ₎ Emission at . 6710

Ä

Depth of Sample 5 cm

- - - Fluorescence Background of Tapwater

Ratio of Chlorophyll lal to I bi in Extract is 2.5 to I

0~---~IO~O~--~2~0~O----~30~O~--~4~OO~----~~~----~6~0~0~--~7~00

O

.

Concentration of Chtorophyll Extract

(p.

gms /Iitre HeO )

FIG. 13. FLUORESCENCE ~MISSION FOR CHLOROPHYLL EXTRACT IN WATER AT 6710Ä AS A FUNCTION OF CONCENTRATION

104--r---~---~

....

_Z

:

:; Cl.

•

0::: o

ii

•

..

o ö '&.

-

o ....

•

.D E ::J Z ~ _ _ _ NF JThICk 011 Film\. 9'\.0' 5210 X f N F {CalCium Irl,nolulphonate } 9

a'

4254 X (2mgm 11' .. -', NF{R_miM BN (4.5/.Lgm/lI,rO-"} 9

a'

5676 X NF

{wo,or a' }

9 4254 X NF{WO'W a' } 9 5210 X NF

{wo,or ot}

9 5676 X llN~ RMS SOLAR SKY

----~~--~~---~

10~~----~~--~~~--~~----~~----~~--~~---~ _{500 600.} Altitudl in Mlterl

VARIATION OF FLUORESCENCE SIGNAL FOR A THICK OIL FILM, WATER BACKGROUND AND THRESHOLD CONCENTRATIONS

OF CALCIUl~ LIGNOSULPHONATE AND RHODAMINE BN AS A

FUNCTION OF ALTITUDE

FIG. 14

•

U'rIAII lIIPOIt't NO. 1.15

Institute·far Aerospace Studies, University of Toronto

THE PEVELOPKENr 01 All AIRBORNl!: IlEImE WEIl rLUOROSENBOR roR tBE 111 on. POLLU'rION DETICTION ANI) I!YllI\OLOGIC STUDIES

Meaaun., R. M., IUld Br1.tOll, M. l8 paa •• l4 ~\Ire.

1. Laser ,1nduced tluor •• oenee 2. 11uoreaeellcl 3. Cillorophyll 4. L1111111 Suli'lIonatl 5. PollutlO11 6. Laaer acatt.r1lli 7. ll1IIaral tluor •• cellC" 8. R.mot. •• III1na

9. Oil i'OllutiOll

I. ",,"ure., R.M., an4 Brilt"", M. II. lIrIAS Rei'ort No. l75

The f1r.t pllt.se ot a develOi'l'8l1t Fogram... devote'" to tb • • xploU .. t1011 ot l .... r

1II"'uced nuore.cellce tor environmental .ell.lllg lias beell completed. A Fotot.". Laser rluoro.ellaor lias been COII.tructed &lid uae'" to .valuat., 111 tb. laboratorf;

tIIe f .... lbill,tf ot thia COllC.pt an4 to tIXl>lor. th. i'ot.lltlal rang. ot awUcat10111.

Specl .. l'attentlO11 lias be'lI 8lven to ... iIlg the ablUtf ot a Laa.r rluoro.ell.or '

to _p the extlllt ot lUl oil .Uck, locat. th • • oure. ot U811111 aul1>honate pollu..

tlol1 lU1d IIIOIÛtor the di'i'ersal ot a ,trac.r 411 tor lIfdrologlc ua ••• Th. Ff!1III1IIaz'f

re.utts ot our atudf AH verf IIICOuragillg &lid leads ua to i'r • .uct tllat a Laser lluorosenaor eoul'" 'oe 1IIed tor envirOlllllelltal IIlIIiIlg 'trom lUl Urcraft tlJ1ll& at .

betveen'l.OOO &lid 2000 ft. 011 a 24-hour b ... ia. ' .

~

WW RZPOR'r \10. 1"

Inl,titute far Aerosp.c. Stud! .. , Univerlity of T orontc TIIII: 1)EV!LOM1fr r:JI All AI1IlKlUII REIOrE WEIl rL\1aIaI!IIIOR rOR tB! 111

OIL POLLWION I)Z'l'IlC'rI<lII ANI) HYDROLOGIC STUDIES

Me •• ure., R. M., &lid Bri.t"", M. 18 :PAIe. l.4 figure.

l. La.n lndllOed fluore.cellce 2. Fluore.cenee 3'. ChlorOilbfll 4. L1gn1n Suli'lIonate 5. PollutiOll 6. Laaer .cattering 7. Mineral fluore.cenee 8. Remote .e1l811lg

9. 011 i'olwtloo

I. )lea.ure., R.M., &lid Bri.tow, M. II. lIrIAS lIel>ort 110. 175

Th. fir.t i'1Ia •• ot a c1evelOilllOllt i'rogr ... "'evot.d to tb. elqlloltatioll ot la.er

induce'" fluor •• c.nce for ellvirODlllelltal aenl1llg bal been completed. A i'rotot.".

La.er rluoro.ell.or ba. been con.tructed and uaed to evaluate, 111 tbe laboratQrf,

tbe tealibil1tf of tb1. CCIICept and to tIXl>lore the i'Otelltial range ot awUcatlona. Special 'attentlol1 ba. belll givell to ... iIlg the abil1tf ot a Laser Fluoro.ell8or

to mail the .xtellt of lUl oil .Uel<, locate tb • • aurce ot l1gn1n auli>bOnate i'Ollu-tioll &lid lIIOOitor tbe di.i'er,al ot a tracer 41e tor bfdrologlc ua ••• The Felilll1.Jl,arf

.e.ult. of our .tudf are verf ellcouragillg and lead. ua to prediet tb&t a Laser

rluoro~en.or could 'oe uaed tor environmelltal •• lI8i1lg trom an aircraft ~ at

betveen l.OOO &lid 2000 ft. 011 a 24-hour baah.

~

Available copies of t:his report are limited. Return this card to ÜTIAS, if you require a copy. Available co pies of this report are limited. Return this CIIrd to UTIAS, if you require a copy. _. ,

lIrIAS lIEPOR'r NO. l75

Institute far Aerospace Studies,. Vniversity of T oronto TIm DEVELOPMEII'r ar All AIRllCIUIE REIClTE LASER FLUOROSENBOR roR WE IN OIL POLLI1UON DETECTIOII AND HYDROLOOIC STUDIm

Me ... urea, R. M., IUld Brist"", M. 18 pages 14 flgure.

1. Laser iDduced fluor.scence 2. Fluorescence 3. Cbloropbfll 4. L1gn1n Sulpbooate

5. Pollutioll 6. Laser .catterillg 7. Mineral fluorescellC. 8. Remot. sell8i1lg

9. Oil pollutioll

I. Meaaures, R.M., and Brl.tow, M. II. lIrIAS Report No. 17';

The fint pbs..le ot a develOi'l'8nt Fogr&mme devoted to tbe expl01tatlon ot .l .... er induced. fiuorescence for environmental senslng has been completed. A prototype

Laser JPluorosensor has been censtructed and used to evaluate, in the laboratory, tIIe feaalbll1ty ot tb1s concept and to explore tbe potel'tlal range ot appl1catlona. Speclal 'attentlo11 bas been given to aasessing the abil1ty o€ a Laser Fluoro~ensor

tQ map tba extent of an 011 slick, locate the source ot lignlll sulpbOllate poUu. tion and monitor tbe dispersalot a tracer dfe tor bfdrologic usos. The FelilldJlarf

resutts ot our studf are verf encouraging and lead. ua to pred1ct tbat a Laser

~luaroelllsor eould be used tor environmental . sensillg trom an aircraft nf1ng at

betveen 1000 and 2000 ft. on a 24-bour basls.

~

Availa,ble cQpies of this report are limited. Return this card'tc UTIA$, if you require a copy.

lIrIAS REPORT NO. 175

Institute for Aerospace Studies, University of T oronto

'rI\E D~PME!fr or Alf A.IRBaRm: REMOTE LASER FLUOROSElflOR FOR WE IN OIL POLLl1rIOIl DETECTION AND .. HYDROLOGIe STUDIES

Measures, R. M., and Br1stow, M. 18 pages 14 figures

1. Laser induced fluorescence 2. Fluorescence 3. Cbloropbfll 4. L1gn1n Sulpbonate 5. l'ollution 6. Laser scatterlllg 7. Mineral fluorescence 8. Remote sell8111i 9. 911 poUutlon

I. Measures, R.M., and Bristow, M. Il. lJrIAS Report Ilo. 175

Tbe fust phase ot a development progreJrme devoted te the explo1tat10n oL laser

induced tluarescence tor environmental sens1ng bas been campleted.. A prototype

Laser l"luQX'osensor bas been conatructed and used to evalUàte, in the laboratary,

the feas1bll1tf of tb1s concept and to explore the potentlal range of appUcationa. 8peclal'attelltioll lias been .. iven to assess1llg tbe ab11itf of a Laser Fluorosensor

to map tbe extent of an 011 sUck, locate tbe souree ot l1gn1ll sulpbonate

poUu-tl,on and IIXlnitor tbe d1spersal of a tracer dfe for lIfdrologlc uso8. The Felilll1.Jl,arf

re_ult. of our study are very encouragillg and leads us to predict tbat a Laser Fluorosenspr could be used tor environment al aellBing frOlll an aircratt fl}l1ng at

bet"eoll 1000 and 2000 tt. on a 24-bour baals.

~