However, Parry and Hern (8) reported negligible iodate at 

IC when they used an open glass tube as a bubbler; this 

seems to indicate that iodate would not be formed at IC 

with an impinger. We feel, nevertheless, that the four data 

points these investigators presented at unspecified values 

of other parameters do not provide sufficient information 

to draw a definite conclusion. 

The acidification procedure, outlined here, provides a 

satisfactory method for the analysis of high ozone concentrations. This is in agreement with Schmitz (15). The procedure would not be suitable for lower levels of ozone (less 

than 50 ppm) because the iodide solution is slowly oxidized 

after acidification and this would lead to a significant error. 

However, this shortcoming might be overcome by using 

buffered acidification to a controlled pH level where the 

rate of iodate decomposition (Equation 3) is rapid, but 

where oxidation remains negligible. This acidification 

might also be performed in stages to minimize the total 

time during which the pH is low. 

Literature Cited 

(1) Federal Register, Vol. 36, No. 84, Part 11, p 8195, April 30, 

1971. 

(2) Byers, D. H., Saltzman, B. E., “Determination of Ozone in Air 

by Neutral and Alkaline Iodide Procedures,” p 93 in “Ozone 

Chemistry and Technology,” Am. Chem. SOC., Adu. Chem. Ser., 

No. 21 (1959). 

(3) Birdsall, C. M., Jenkins, A. C., Spadinger, E., Anal. Chem., 24, 

662 (1952). 

(4) Ingols, R. S., Fetner, R. H., Eberhart, W. H., “Determining 

Ozone in Solution,” p 102 in “Ozone Chemistry and Technology,” Am. Chem. SOC., Adu. Chem. Ser., No. 21 (1955). 

(5) Boyd, N. W., Willis, C., Cyr, R., Anal. Chem., 42,670 (1970). 

(6) Hodgeson, J. A., Baumgardner, R. E., Martin, B. E., Rehne, K. 

(7) Kopczynski, S. L., Bufalini, J. J., ibid., 43, 1126 (1971). 

(8) Parry, E. P., Hern, D. H., Enuiron. Sci. Technol., 7,65 (1973). 

(9) Dietz, R. N., Pruzansky, J., Smith, J. D., Anal. Chem., 45, 402 

(1973). 

(10) Kolthoff, I. M., Belcher, R., “Inorganic Analysis,” Vol. 111, 

“Titrimetric Methods: Oxidation and Reduction Reactions,” p 

281, Interscience, 1957. 

(11) Saltzman, B: E., Gilbert, N., J. Am. Znd. Hyd., 20, (1959). 

(12) Saltzman, B. E., “Selected Methods for the Measurement of 

Air Pollutants,” Public Health Service Publication, No. 999- 

AP-11, p D-1, 1965. 

(13) Jacobs, M. B., “The Chemical Analysis of Air Pollutants,” pp 218-20, Interscience, 1960. 

(14) Hendricks, R. H., Larsen, L. B., J. Am. Znd. Hyg. Assoc., 27, 

80 (1966). 

(15) Schmitz, L. R., Enuiron. Sci. Technol.. 7,647 (1973). 

A., ibid., 43,1123 (1971). 

(16) Vogel, A. I., “A Textbook of Quantitative Inorganic Analy- 

(17) Lanee. N. A.. Ed.. “Handbook of Chemistrv.” D 1124. Handsis,” p 345, Wiley, 1961. 

“, . book PLblishers’, Inc:, 1949. 

Received for review SeDtember 11. 1974. AcceDted Februarv 18. 

1975. Work supported’ by National Science Foundation Grant 

GK-37469. 

Ambient Air Analysis with Dichotomous Sampler and 

X-ray Fluorescence Spectrometer 

Thomas G. Dzubay’ and Robert K. Stevens 

Chemistry and Physics Laboratory, Environmental Protection Agency, Research Triangle Park, N.C. 277 1 1 

Aerosol samples were collected in St. Louis using a dichotomous sampler operating on the principle of virtual 

impaction and were analyzed for a wide variety of elements 

by X-ray fluorescence. A striking difference was observed 

between the particles collected in the 0-2-gm range and the 

particles collected in the 2-10-pm range. Although nearly 

equal mass was collected in the two size ranges, the deposit 

of small particles was black and the deposit of the coarse 

particles was a light tan. At least 75% of the S, Zn, Br, and 

Pb occurred in particles smaller than 2 pm, and at least 

75% of the Si, Ca, Ti, and Fe occurred in particles larger 

than 2 pm. 

A major task in the field of air pollution monitoring is 

the development of devices for determining the mass and 

composition of airborne particulate matter as a function of 

size and time. This instrumentation is presently needed for 

human studies research in which attempts are being made 

to determine toxic threshold levels for aerosol constituents 

in ambient air. It is also needed for aerosol formation and 

transport studies essential to the development of cost-effective control strategies. 

To perform elemental analysis on an increasing number 

of samples in more than one size range, a rapid analytical 

procedure is required. The use of X-ray fluorescence spectroscopy is well suited to meet this need for elements heavier than A1 in atomic weight (I, 2). A wide variety of elements can be determined in a few minutes without sample 

preparation. The composition of the sample is determined 

by irradiating with a beam of X-rays and observing the 

emission of characteristic K and L X-rays. By use of secondary fluorescers to produce a nearly monochromatic but 

variable energy X-ray source, a wide variety of elements 

throughout the periodic table can be analyzed (3). If particles are collected on the surface of a membrane filter, then 

no sample preparation is required. 

The sample collection device must be designed with consideration given to the nature of the aerosol and to the effects of the aerosol on human health. Recent measurements 

by Whitby et al. (4) show that the volume and hence the 

mass of aerosol in ambient air has a bimodal distribution 

with a relative minimum at particle diameters of about 2 

pm. It has been established that particles smaller than 3.5 

pm in diameter can penetrate deeply into the human respiratory system, and that larger particles are trapped in the 

upper respiratory passages (5). For these reasons, it is desirable to use a dichotomous sampler to collect particles in 

two size ranges rather than to collect total particulates on a 

single filter. Separation at particle diameters of about 2 gm 

would be appropriate for aerosol research; separation at 3.5 

pm is needed for monitoring aerosols to protect human 

health. Ractionation of particles into several additional 

size ranges is desirable only if the increased cost of analyzing more stages and the decreased deposited mass per stage 

can be tolerated. 

For size fractionation, a wide variety of conventional impactor devices is available in which particles are collected 

on a surface placed behind a circular or slit-shaped orifice. 

Volume 9, Number 7, July 1975 663 
Collection in these devices may not be quantitative if particles bounce off the intended collection surfaces. Particle 

bounce errors can be reduced by applying an adhesive coating to the collection surface (6). However, Lundgren has 

demonstrated that the effectiveness of the adhesive coating 

can become nullified when a monolayer of particles has 

been deposited (7). 

The problems inherent in collection by impaction onto 

surfaces can be eliminated by using a virtual impactor in 

which particles are impacted into a slowly pumped void (8, 

9). Figure 1 illustrates a dichotomous sampler (a device 

which collects particles in two size ranges) which operates 

on the principle of virtual impaction. In this device, the air 

being sampled passes through an inlet jet and is deflected 

around a coarse particle receptor. Coarse particles, unable 

to follow the curving air stream, enter the coarse particle 

receptor and are collected on a filter. Fine particles that 

move with the air stream are collected on a second filter. 

The use of filters in a virtual impactor eliminates the particle bounce problem associated with impaction surfaces. 

To minimize wall losses in the virtual impactor, it is necessary to maintain a small flow of air into the coarse particle receptor. In the device illustrated in Figure 1, critical 

flow orifices are used to maintain a 7:l concentration ratio 

between inlet and coarse particle air streams. For this flow 

ratio, 14.3% of the fine particle mass is deposited on the 

coarse particle filter. 

To reduce the contamination of fine particles on the 

coarse particle filter, two virtual impactors, which have the 

same fractionation cutpoint diameters, can be operated in 

series. Figure 2 illustrates a practical two-stage device developed by Peterson (10). An internal orifice maintains a 

7:l concentration ratio for each stage, and external orifices 

maintain an overall concentration ratio of 49:l for the inlet 

and coarse particle air streams. For this flow ratio, only 2% 

of the fine particle mass is collected on the coarse particle 

filter. Attempts have been made to develop a single-stage 

virtual impactor with a 49:l concentration ratio, but wall 

losses were much worse than those obtained using a twostage device (10, 11 ). 

In the present work, a prototype dichotomous sampler 

was field tested and evaluated for usefulness as an ambient 

air monitor. Aerosols collected in the dichotomous sampler 

and in a second automatic filter changing device were analyzed for elemental content with an X-ray fluorescence 

spectrometer. 

Experimental 

The dichotomous sampler used in this study is illustrated in Figure 2 and was built by Environmental Research Corp. (St. Paul, Minn.). It was evaluated for wall 

losses and fractionation characteristics by Loo and Jaklevic 

(12) using monodisperse aerosols of dioctylphthalate. It 

was demonstrated that particles smaller than 2.0 pm (50% 

cutpoint diameter) were collected on the fine-particle 

stage, and particles ranging from 2.5-10 pm (50% cutpoint 

diameters) were collected on the coarse particle stage. Wall 

losses were very low for particles smaller than 1 pm and for 

particles between 3.5 and 8 gm. The wall losses were about 

25% in the 2-3-pm range of diameters and were large for 

particles larger than 10 gm (12). 

The dichotomous sampler was operated with the flow 

rate divisions indicated in Figure 2. Flow rates were 

checked at the beginning and end of each measurement 

using a dry test meter. The inlet flow rate was maintained 

at 49 l./min within an accuracy of f3%. A second sampling 

device which automatically changed the filter every 2 hr 

was also used. This device also operated at a flow rate of 49 

7 LMIN 

COARSE 

PARTICLE 

RECEPTOR 

It1 

TO PUMP 

Figure 1. Schematic view of dichotomous sampler that contains a single-stage virtual impactor 

Flow rate at inlet is 7 I./mln, and the concentration ratio for coarse particles 

is 7: 1. Coarse particles are collected on filter C; fine particles are collected 

on filter F 

INLETU LMlN 

FIRSTSTAGE I1 JETS) 

INTERNAL FLOW ORIFICE 

SECONO STAGE I1 JET1 

7 LMlN 

yilN2 -TO - FLOW FINEPARTICLES MONITOR ~ 

IU LMlNl 

INCHES 

COARSE PARTICLES I1 LMlNi 

Figure 2. Drawing of dichotomous sampler with two substages used 

in present work 

Each substage has the same fractionation cutpoint diameter. The internal 

flow orifice and orifices in exit flow lines (not shown) together maintain a 7:l 

concentration ratio for each stage 

l./min, and used a single collection surface without size 

fractionation. 

Measurements of trace element composition were made 

using an energy dispersive X-ray fluorescence spectrometer 

(3) which is illustrated in Figure 3. In this device, an X-ray 

beam from the tungsten anode excites the secondary fluorescer which in turn excites the sample with its nearly 

monochromatic characteristic X-rays (13). The three fluorescers used are Cu, Mo, and Tb, for which the corresponding anode potentials of the X-ray tube are 35, 50, and 70 

kV, respectively. Each sample was analyzed for 5 min with 

each fluorescer with an electron current of 400 pA in the 

X-ray tube. The fluorescent X-ray lines emitted by the 

sample were detected in a lithium-drifted silicon detector 

which used electronic collimation to enhance the signal 

664 Environmental Science & Technology 
I nv 

Figure 3. Schematic view of X-ray fluorescence spectrometer using 

secondary fluorescer and solid state detector 

above background (3). Because of the very compact geometrical arrangement of the components in Figure 3, an adequate count rate was obtained with X-ray power dissipation of less than 30 W. 

The ability of the system to detect a wide variety of elements in the atmosphere is illustrated in Figure 4, which is 

a plot of the ranges and typical values of the concentrations 

of various elements in urban air (15). The detection limits 

(3a peak area above background) for X-ray fluorescence 

are superimposed on the plot. These detection limits are 

expressed in ng/cm2 for each element assuming that it is 

deposited on a cellulose membrane filter which has a mass 

per unit area of 5 mg/cm2. The discontinuities in the detection limit curve using the molybdenum fluorescer are due 

to iron and copper impurities in the X-ray collimator above 

the detector. The detection limits can be converted to units 

of mass per unit volume by dividing the values on Figure 4 

by the air volume sampled per unit area of filter. For a flow 

rate of 49 l./min through an 8-cm2 area of filter, the conversion factors are 0.74 m3/cm2 for a 2-hr sampling interval 

and 8.8 m3/cm2 for a 24-hr sampling interval. 

For X-ray analysis it is necessary that particles be collected on a filter having very low levels of impurities. Figure 5 shows a spectrum of a Teflon membrane filter with a 

105 

104 

k 103 

d 

n 

E 

0 5 102 

E 

y 101 

2 100 

5 

z 

c 

0 

u 

-l 

2 

w 

10-1 

10-2 

I 0-3 

r: 

8 

CIIMIIEL 

Figure 5. X-ray spectra of clean polyethylene-backed Teflon filter 

and clean glass fiber filter using molybdenum secondary fluorescer 

for excitation 

In Teflon filter spectrum, peaks in channels 188 and 238 are due to iron and 

copper impurities in collimators of X-ray spectrometer 

polyethylene backing which is excellent in this regard. Figure 5 also shows a spectrum of clean glass fiber filter which 

contains large amounts of impurities and is unacceptable 

for X-ray fluorescence analysis. Membrane filters, made of 

mixed esters of cellulose and having 0.8-fim pore size, make 

a good choice and were used in this work. Their elemental 

purity is similar to that of the Teflon shown in Figure 5 except for impurities of Ca and C1. High-porosity Teflon with 

superior gravimetric characteristics became available after 

the experimental phase of this work was completed. 

The elemental concentrations were determined by a 

minicomputer interfaced to the X-ray spectrometer. For 

the analysis, it was assumed that an observed X-ray spectrum was a superposition of characteristic X-rays of each 

individual element in the sample. Individual spectra of 40 

pure element standards were accumulated and stored in 

the computer memory. These individual spectra as well as 

104 

103 N 

E 

t 

I 

. 

102 : 

A 

101 

E 

100 t; Y 

0 

10-1 

10.2 

I 0-3 

Figure 4. Detection limit curves using Cu, Mo, and Tb fluorescers expressed in ng/cm* 

Conditions of analysis and substrate are specified in the text. Also shown are ranges and typical values of urban trace element 

concentrations compiled by Cooper ( 74) 

Volume 9, Number 7, July 1975 665 
a stored clean filter background spectrum were compared 

with the unknown aerosol spectrum using a stripping procedure to determine the concentration of each element (3). 

By making a judicious choice of the order in which the elements were stripped, the prohlem of interfering K, and Kg 

X-ray lines was largely eliminated. 

The analyzer was calibrated using thin single-element 

concentration standards according to a procedure developed by Giauque et al. (I ). These standards consisted of 

vacuum evaporated foils obtained from Micromatter Co. 

(Seattle, Wash.) and dried solution deposits on memhrane 

filters obtained from Columbia Scientific Industries (Austin, Tex.). The elemental deposits were uniform across the 

37-mm diameter of each standard and ranged in mass per 

unit area from 10-150 eg/cm2. They were known to an accuracy of f10% or better. 

For airborne particulates uniformly deposited onto a 

37-mm diameter filter, the concentration (in eg/cm2) of a 

specific element on the filter was determined by comparison of the observed count rate with that of the known foil 

of the same element. A smooth curve was fitted to the calibration points and used to determine elements for which 

foils were not available or not accurately known. By use of 

the smooth calibration curve, the root mean square deviation of the X-ray analysis of each calibration foil from the 

gravimetric value was 5% for the elements with atomic 

numbers between 19 and 38. 

From these considerations it is estimated that for elements well above the detection limit, the 1-0 accuracy for 

X-ray analysis of elements with atomic numbers above 20 

(Ti and heavier) is +lo%. This is compatible with the results from a recent study by Hammerle et al. (15) in which 

X-ray fluorescence and neutron activation analyses were 

applied to aerosol samples, and 20% agreement was obtained. For the lighter elements the energies of the characteristic X-rays are sufficiently low that significant self-ahsorption can take place within the larger collected particles 

and within the filter media for fine particles that penetrate 

into the filter, Self-absorptibn corrections were made, using 

a procedure developed by Dzuhay and Nelson (16). 

For the two size ranges of the dichotomous sampler, the 

total aerosol mass was determined by gravimetrically comparing the weights of each filter before and after sampling. 

A 210Po radioactive source was placed inside the microbalance chamber near the weighing pan to eliminate electrostatic effects. Gravimetric accuracy was f50 Fg for the filters, which had typical deposit masses of about 1-2 mg. 

Results and Discussion 

Samples were collected over the period between August 

26 and August 31, 1973, in St. Louis at a site on the Washington University campus. Figure 6 shows a photograph of 

two filters used in the dichotomous sampler for the 23-hr 

period beginning at 0915 hr on August 30. X-ray spectra for 

these filters are shown in Figure 7, and the elemental and 

gravimetric analyses are shown in Table I. The results for 

five days of continuous measurements using 2-hr sampling 

periods with unfractionated aerosol are shown in Figures 8 

and 9. 

The filters shown in Figure 6 indicate the striking difference between small and large particles. The large particles 

produce a light tan deposit, and yet they have almost as 

much total mass as the small ones, which make a black deposit. This is consistent with the notion that the large particles contain large amounts of earthen crustal materials, 

whereas the small particles consist of combustion and secondary aerosols. From the analysis of the two filters in 

Table I, it appears that the large particles contain at least 

666 Environmental Science & Technology 

2;hr period beg;& at 1015 hr, August 30, 1973, in a St. Louis 

residential neighborhood 

Volume Sampled is 68 m3. Filters are mounted in 5.1 X 5.1-cm frames used 

for automatic manipulation within X-ray analyzer. Elemental analysis for 

these samples is given in Table i 

Figure 7. X-ray fluorescence spectrum with copper secondary fluorescer excitation for particles collected in two size ranges on filters 

shown in Figure 6 

Elemental analysis is given in Table I. Peaks labeled CI are partly due to slgnificant but variable amounts of chlorine in the filter blanks 

Table 1. Analysis o f St. Louis Aerosol on Filters 

Shown in Figure 6 

Samples collected for a 23-hr 

August30. 1973 

Ele- Fine+ Coarse,= 

ment ng/mB ng/mr Element 

Si _. mn+ ifin mn+ inn 7" 

S 

K 

Ca 

Ti 

V 

Cr 

Mn 

Fe 

co 

___ .I" 

3700f 600 6001 200 As 

160Zt60 240+80 Se 

llOf 40 1700+300 Br 

64& 7 210f 30 Rb 

4+2 <3 Sr 

<3 <3 Cd 

5+2 6Zt2 Sn 

130+ 14 400+40 Ba 

<2 <2 Pb 

.. .. . 

FiW,G 

ns/mz 

45dz 6 

20f 10 

7f 2 

114& 12 

<1 

<2 

<13 

<14 

<30 

460 f 50 

CO.W*W 

ns/mr 

15+ 2 

<4 

<2 

30* 4 

<1 

4+ 2 

<13 

<14 

<30 

llOf 12 

19,200f 

nnn 

Ni <2 <2 Gravi- 26.600+ 

cu <3 <3 metric 800 ... 

aThe collected size ranges are 0-2 pm for fine particles and 2.5-10 

for coarse particles. 
Table II. Maximum Amount of Various Sulfate 

Compounds Deduced from Observed 

Elemental Sulfur and Metal Concentrations 

Listed in Table I for Particles Smaller 

Than 2 Mm 

It is assumed that all of the sulfur is in the form of 

sulfate 

Compound Sulfate, %a Compound Sulfate, %a 

K2S04 <2% Fe~(S04)~ < 3% 

CaS04 <3% ZnS04 <1% 

TiZ(SO& <2% PbS04 < 2% a If only fraction F of the elemental sylfur were in the form of sulfate, then these percentages are to be multiplied by 1/F. 

75% of the Si, Ca, Ti, and Fe at the sampling site. At least 

75% of the S, Zn, Br, and Pb is contained in the small particles. These same features were observed in all the data 

from the dichotomous sampler over the August 26-31 sampling period. Similar results have been reported by Lee et 

al. (17) for a variety of elements. The concentrations listed 

in Table I for V, Cr, Mn, Ni, Cu, Zn, Rb, and Sr are significantly lower than the typical urban values shown in Figure 

4. This may be due to the residential nature of the sampling site and to the relatively clean air conditions at the 

time of measurement. Variable amounts of chlorine in the 

filter blanks prevented analysis for that element. 

In these data the most abundant observed element is sulfur. Certain sulfate compounds such as zinc ammonium 

sulfate, sulfuric acid, and ammonium sulfate have been 

shown by Amdur (18) to be pulmonary irritants. If one 

makes the assumption that all sulfur is in the form of sulfate, then one can deduce the maximum possible fraction of 

the sulfate that is associated with the various observed cations as shown in Table 11. One notes that the biologically 

active zinc sulfate compounds can only be minor components. Table I1 suggests that significant amounts of sulfate 

may be bound to light element cations such as H+ or 

(NHJ+. Additional work needs to be done to demonstrate 

the accuracy of the X-ray analysis for sulfur, to determine 

the percentage of sulfur in the form of sulfate and to verify 

that the observed sulfur is not the result of SO2 being converted to sulfate on the filter. 

The diurnal patterns of the elements plotted in Figures 8 

and 9 give valuable clues about the source of these pollutants. For example, the enormous fluctuation in the titanium concentration is indicative of a local discrete source. 

The lack of major fluctuations in the sulfur concentration 

indicates a lack of a single local or discrete source. The Br 

to Pb ratio and the lead concentration seem to be influenced by rush hour traffic patterns. 

These results illustrate the utility of using the combination of dichotomous sampler, X-ray fluorescence analyzer 

and gravimetric analysis for particulate monitoring. For 

future studies of this type, a newly developed dichotomous 

sampler will be available. Through careful design by Loo 

(II), the wall losses in the 0-15-wm range of diameters are 

reduced to a very low level. Ten dichotomous samplers with 

automatic sample changers are presently being installed in 

a network for use in the Regional Air Pollution Study in St. 

Louis. A second low loss dichotomous sampler has been developed for routine field use (19). 

Acknowledgments 

The authors are grateful to F. S. Goulding, J. M. Jaklevic, B. V. Jarrett, J. Meng, and H. A. Rook for valuable advice and discussions, to J. A. Cooper for providing the plot 

TIME OF DAY 

Figure 8. Plot of 2-hr average concentrations of S, Fe, and Ti for the 

five-day period between August 26 and August 31, 1973, in St. Louis 

Size fractionation was not used 

0 0 0 0 0 0 

~SUN4~ON~TUf~WEO~T~U~FFRI

TlUE OF DAY 

Figure 9. Plot of 2-hr average concentrations of Zn, Pb, and the 

Br-Pb ratio for period between August 26 and August 31, 1973, in 

St. Louis 

Smooth curve is a repetitive 24-hr pattern and guide to the eye. Size fractionation was not used 

of elemental abundances used in Figure 4, to W. E. Wilson 

for providing space in his mobile laboratory in St. Louis to 

operate the sampling equipment, and to W. C. Peters and 

C. R. Sawicki and L. E. Hines for valuable assistance. 

Literature Cited 

(1) Giauque, R. D., Goulding, F. S., Jaklevic, J. M., Pehl, R. H., 

Anal. Chem., 45,671 (1973). 

(2) Rhodes, J. R., Pradzynski, A. H., Hunter, C. B., Payne, J. S. 

Lindgren, J. L., Enuiron, Sci. Technol., 6,922 (1972). 

(3) Goulding, F. S., Jaklevic, J. M., "X-Ray Fluorescence Spectrometer for Airborne Particulate Monitoring," EPA Rep. No. 

EPA-R243-182. Auril 1973. 

(4) Whitby, K. T., Hisar, R. B., Liu, B. Y. H., J. Colloid Interface 

(5) Liuumann. M.. Harris. W. B.. Health Phvs.. 8.155 119621. 

Sci., 39, 177 (1972). 

(6) Mi;, K. R.', J. Sei. Instrum., 22,187 (19&).' 

(7) Lundgren, D. A,, J. AirPollut. Contr. Assoc., 17,225 (1967). 

(8) Hounam, R. F., Sherwood, R. J., Am. Ind. Hyg. Assoc. J., 26, 

(9) Conner, W. D., J. Air Pollut. Contr. Assoc., 16,35 (1966). 

' 

122 (1965). 

Volume 9, Number 7, July 1975 667 
(10) Peterson, C., Environmental Research Corporation, private (16) Dzubav. T. G., Nelson, R. O., in “Advances in X-Rav Analvcommunication. 1973. 

(11) Loo, B. W., to be published. 

(12) Loo, B. W., Jaklevic, J. M., “An Evaluation of the ERC Virtual ImDactor.” Lawrence Berkelev Laboratorv Publication LBL2468,-Berkeley Calif., 1974. 

(13) Jaklevic, J. M., Giauoue. R. D.. Malone. D. F.. Searles. W. L. 

in “Advances in X-Ray Analysis,’’ Heinrich et al:, Eds., Vol. 15, 

p 266,1972. 

(14) CooDer. J. A.. Battelle Pacific Northwest Laboratorv ReDort “. 

~ BNWL‘-SA-4690, June 1,1973. 

(15) Hammerle, R. H., Marsh, R. H., Rengan, K., Giauque, R. D., 

Jaklevic, J. M., Anal. Chem., 45, 1939 (1973). 

ses,” Vol-18, p 619, W. L. Pickels, C. S. Barrett, J. B. Newkirk, 

C. 0. Ruud, Eds., 1974. 

(17) Lee. R. E.. Goranson. S. S.. Enrione. R. E.. Morean. G. B.. .. I. 

Enuirok. Sci. ’Technol., 6,1025 (1972). ’ 

(18) Amdur, M. O., Proc. Am. Phil. Soc., 14,3 (1970). 

(19) Peterson, C., EPA Report, “Development and Testing of Dichotomous Sampler,” to be published, 1975. 

Received for review July 11, 1974. Accepted April 10, 1975. Mention of commercial products is for identification only and does 

not constitute endorsement by the Enuironmental Protection 

Agency of the U.S. Gouernment. 

Distribution of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) 

in Aquatic Model Ecosystem 

Allan R. Isensee* and Gerald E. Jones 

Agricultural Environmental Quality Institute, Agricultural Research Center, ARS, 

United States Department of Agriculture, Beltsville, Md. 20705 

Several organisms in a model ecosystem were exposed to 

14C-labeled TCDD for up to 31 days to determine the distribution and bioaccumulation potential in the aquatic environment. TCDD accumulation by all organisms was directly related to water concentration (0.05-1330 ppt) and 

averaged 2.0-2.6 X lo4 (snail, Gambusia, and daphnid) and 

4-9 X lo3 (duckweed, algae, and catfish) times the water 

concentration. No metabolites of TCDD were found in submerged soil, water, snails, Gambusia, or catfish. 

Discovery in 1970 of the highly toxic contaminant 

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the herbicide (2,4,5-trichlorophenoxy) acetic acid (2,4,5-T) spawned 

a great deak of concern about the potential hazard to man 

and the environment. This concern subsequently stimulated numerous studies to assess the behavior of TCDD in the 

environment [as summarized by Helling et al. (I)]. These 

studies revealed that TCDD is immobile in soils, is not 

translocated in plants, has a half-life in soil of about 1 year, 

and is slowly photodecomposed in water but not on soil. 

The results of these studies, combined with the knowledge 

that presently produced 2,4,5-T contains <0.1 ppm TCDD, 

indicate that TCDD is not entering or being distributed in 

the environment in large quantities. However, concern still 

lingers over the TCDD hazard to man for several reasons: 

(1) it has an extremely high mammalian toxicity [LD50 of 

10 pg/kg for rabbits (2)]; 0.6 wg/kg for guinea pigs (3); (2) it 

is a teratogen (4,5); and (3) concentrations of TCDD ranging from about 20-1000 parts per trillion (ppt) have been 

found in fish and crustaceans from South Vietnamese waters (6). Since this concern exists and the total environmental impact is still in question, we felt that further information on the probable environmental distribution would 

be useful. This study was therefore initiated to determine 

the availability, distribution, and bioaccumulation potential of TCDD in a model ecosystem. 

This model ecosystem was designed to simulate the usual 

mode of entry of pesticides into water and the simultaneous exposure of several organisms representing parts of 

natural food chains. The bulk of pesticides (or their contaminants) that enter yater unintentionally do so via erosion of pesticide contaminated soil or plant remains from 

agricultural land. The amount of pesticide that enters 

water from the submerged soil will depend on its solubility 

and desorption from soil. Simultaneous exposure of several 

organisms should ensure that accumulation by all processes-i.e., absorption, adsorption, and consumption of 

lower by higher food chain organisms, would be represented. As designed, this model ecosystem exposes both a test 

chemical and organisms to some of the major conditions 

that might realistically be expected to occur in the environment. The system is not designed to determine the effects 

of a chemical on the organisms (though some primary effects can be assessed) but rather, how does the chemical behave when subjected to likely environmental conditions. 

Experimental 

One single concentration and two multiple concentration 

experiments were performed. In each, 14C-TCDD was adsorbed to soil, and placed in the bottom of glass aquaria 

(25.4 X 5.2 X 17.8 cm). Table I summarizes the treatment, 

rate, and replication details of the three experiments. In 

Table I. Soil TCDD Application Rates and Replications 

Total TCDD Type and amount, Final soil 

added per grams, of soil com- TCDD No. of 

tank. !.w bined with TCDDa concn., ppmb replicates 

149 

0 

63 

63 

63 

63 

0 

10 

1 

0.1 

0.01 

0 

Experiment I 

L-2 0 

L-20 

L-20 

L-20 + M-100 

L-20 + M-200 

L-20 + M-400 

L-20 

M-100 

M-100 

M-100 

M-100 

M-100 

Experiment II 

Experiment Ill 

7.45 

0 

3.17 

0.53 

0.29 

0.15 

0 

0.1 

0.01 

0.001 

0.0001 

0 

3 

1 

2 

2 

2 

2 

2 

2 

2 

2 

2 

2 

a L = Lakeland sandy loam, M = M,atapeake silt loam. In II, L was grst treated with TCDD, then dry mixed with M in, treatment tanks. 

Soil concentrations based on total quantity of soil in tank. 

668 Environmental Science & Technology