Toxicity Thresholds of Certain Sodium Sulfonates for Daphnia magna StrausAuthor(s): Louis FreemanSource: Sewage and Industrial Wastes, Vol. 25, No. 11 (Nov., 1953), pp. 1331-1335Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25032335 .

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TOXICITY THRESHOLDS OF CERTAIN SODIUM SULFONATES FOR DAPHNIA MAGNA STRAUS

By Louis Freeman *

Graduate Research Fellow, Industrial Project, Department of Zoology, Physiology and Entomology, Louisiana State University, Baton Rouge, La.

The investigation reported herein was carried out to determine the tox

icity thresholds displayed by Daphnia magna to various sodium sulfonate

compounds and to attempt to relate the obtained values with some mole cular property. Such information should prove valuable for future in

vestigations of these compounds, as some members of this series are thought to be present in effluents of various in dustries and are finding widespread use in the field of synthetic detergents.

Although preliminary work (3) on the toxicity of certain sodium sulfon ates to the bluegill, Lepomis macro

chirus Eaf., indicated that these com

pounds are relatively non-toxic to the test animal employed, even at moder

ately high levels, it was felt that an

evaluation of these compounds by means of the daphnid was advisable, as daphnids and other small crust?cea are an important fish food, and Ander son (2) has shown that Daphnia magna is more sensitive to chemicals than are

fish.

Material and Methods

A survey of the literature concerned with the measurement of toxicity toler ances by means of bio-assay methods

clearly shows a lack of standardization of the methods employed. It is of

prime importance that the results ob tained on pure compounds be readily reproducible by other workers regard less of the location of the laboratory.

* Present address : College of Engineering,

Engineering Experiment Station, Louisiana State University, Baton Rouge, La.

Hence, the author has attempted to

employ such methods as might make it

possible for other workers to duplicate or to evaluate the results obtained in the light of other work.

Chemicals Tested

This investigation is limited to one

series of organic compounds, the so dium sulfonates. Many of the com

pounds tested were selected on the basis of their molecular structure without re

gard to the possibility of their being present in any industrial effluent.

All of the sodium sulfonate com

pounds employed were of the purest grade obtainable (95 per cent or

greater purity).

Culture Method

Culture of the Daphnia magna used in this study was according to the

method of Anderson (2) as modified by Freeman and Fowler (4). Culturing by the indicated method yielded broods, averaging 20 young per brood, every 2% days.

Testing Procedure

The testing procedure employed was that of Anderson (2) as modified by

Freeman and Fowler (4). All tests were conducted for 100 hr.,

11 observations being made during the

period, the observations being made at intervals in geometrical progression in

powers of 1.99. The number of animals alive in each solution was recorded at the time of observation.

After establishment of the limits of

toxicity, three experimental tests were conducted over a narrow range of con

1331

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1332 SEWAGE AND INDUSTRIAL WASTES November, 1953

centrations, the dilution factor for each test being 1.33.

The tests were all conducted at a

temperature of 23? ? Io C.

Calculation of Toxicity Threshold

The toxicity thresholds were calcu lated according to the method of An derson (2). As the experiments were carried out in triplicate, the toxicity threshold was calculated for each test and the average of the three then de termined.

Results

Five experiments were conducted on

each of 10 organic compounds of the sodium sulfonate series. Nine were

aromatic sulfonates and one was an

alkyl sulfonate. Of the 50 experiments, 20 (2 per

compound) were for the purpose of

establishing the toxicity range and 30

(3 per compound) for the establish ment of the toxicity thresholds.

The 100-hr. toxicity threshold of each of the three tests on a given compound

was determined and the three threshold values were averaged. Similarly, the 100-hr. range (0 to 100 per cent mor

tality) for each compound was evalu ated as the average of the three tests.

The pH of the test solutions at the concentration imparting 100 per cent

mortality was also determined. The average 100-hr. toxicity thresh

olds, the 100-hr. toxicity ranges, and the pH values of the 10 compounds investigated are given in Table I.

Discussion

Toxicity Threshold and Molecular Structure

Examination of the average toxicity thresholds in Table I shows several re

lationships between the molecular struc ture and the toxicity displayed by the sodium sulfonates employed in this

study.

Comparison of the toxicity threshold of sodium w-butylsulfonate with those of the other compounds tested indi cates that the alkyl sulfonates are ap parently less toxic than the aromatic sulfonates.

Analysis of the toxicity threshold values for the sodium benzenesulfo nates shows that these compounds are not over one-fourth as toxic, on the

average, as is sodium naphthalene-? sulfonate. Similarly, it is to be noted that sodium anthraquinone-ct-sulfonate is far more toxic to the daphnid than is the sodium naphthalene-/?-sulfonate.

Further examination of the toxicity thresholds of the sodium benzenesulfo nates shows that substitution of various

compounds on the benzene ring in creases the toxicity of the parent com

pound, sodium benzenesulfonate. Com binations of these radicals further in crease the toxicity, as is shown by

TABLE I.?Summary of Results of Toxicity Threshold Determinations for Daphnia magna

Compound Average Toxicity

Threshold (p.p.m.)

Toxicity (p.p.m.)

100% Toxicity

(p.p.m.)

Toxicity Range, 0-100%

Mortality (p.p.m.)

Sodium n-butylsulfonate Sodium benzenesulfonate

Sodium p-chlorobenzenesulfonate Sodium m-nitrobenzenesulfonate Sodium p-phenolsulfonate Sodium 4-nitrochlorobenzene-2-sulfonate Sodium 2,5-dichlorobenzenesulfonate Sodium p-bromobenzenesulfonate Sodium naphthalene-0-sulfonate Sodium anthraquinone-a-sulfonate

3,380 2,840 2,394 2,335 1,876 1,474 1,468

523 135 12

1,637 1,895 1,687 1,000

556 318 389 200

55 10

7,827 8,000 3,007 5,618 5,623 3,187 3,890

843 308

30

6,190 6,105 1,320 4,618 5,067 2,869 3,501

643 253

20

1 The standard reference water employed for dilution medium had an average pH value of 7.34.

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Vol. 25, No. 11 TOXICITY OF SODIUM SULFONATES 1333

TABLE II.?Molecular Weights and Parachors of Ten Sodium Sulfonates

Compound Average Toxicity

Threshold (p.p.m.)

Molecular Weight

Sodium n-butylsulfonate Sodium benzenesulfonate

Sodium p-chlorobenzenesulfonate Sodium m-nitrobenzenesulfonate

Sodium p-phenolsulfonate Sodium 4-nitrochlorobenzene-2-sulfonate

Sodium 2,5-dichlorobenzenesulfonate Sodium p-bromobenzenesulfonate Sodium naphthalene-/3-sulfonate Sodium anthraquinone-a-sulfonate

3,380 2,840 2,394 2,335 1,876 1,474 1,468

523 135

12

160.18

180.16 214.62

225.16

196.16

259.15 249.07

259.08 230.23 310.27

1 Calculated on the basis of free sulfonic ions, employing values of the atomic and struc tural parachors of the molecules.

sodium 4-nitrochlorobenzene-2-sulfon ate and sodium 2,5-dichlorobenzenesul fonate.

Toxicity Threshold and Molecular

Weight

Upon comparing the molecular

weights and the 100-hr. toxicity thresh olds of the sodium sulfonates (Table II) it is noted that an exact relation

ship apparently does not exist. How

ever, upon plotting these two proper ties (Figure 1) it is noted that a trend is present among the sodium benzene sulfonates as a group, the toxicity tend

ing to increase as the molecular weight increases until a certain level is

reached, at which level the relative

change in molecular weight need be rather small in order to produce a

400

300

.c c?

I

o o o

s

200

(00 10 20 40 60 80 100 200 400 600 800 1000 2p00 4,000

Toxicity Threshold (RRM.)

FIGURE 1.-?Molecular weight vs. 100-hr. toxicity threshold (p.p.m.) of ten sodium sulfonates.

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1334 SEWAGE AND INDUSTRIAL WASTES November, 1953

V'

300 I 20 40 60 80 100 200 400 600 800 1,000 2,000 4,000

Toxicity Threshold (P.RM.)

FIGURE 2.?Parachor vs. 100-hr. toxicity threshold (p.p.m.) of ten sodium sulfonates.

marked change in the toxicity thresh old.

Another interesting relation exists between the w-butyl-, the benzene-, the

naphthalene-j?-, and the anthraqui none-a-sulfonates (solid points, Figure 1). It is seen that an almost direct re

lationship exists between the aromatic

sulfonates, with a marked drop for the

alkyl sulfonate's value. Whether this relation is attributable to the increas

ing molecular weight or to the increas

ing volume of the molecule can be de termined from the parachor values of the molecules.

Toxicity Threshold and Parachor

Examination of the values for the

parachors of the sodium sulfonates, Table II, and the plotting of the para chor and the 100-hr. toxicity threshold

(Figure 2) shows a peaked curve for the benzenesulfonates and a straight line for sodium benzenesulfonate, so dium naphthalene-?-sulfonate and so dium anthraquinone-a-sulfonate, with a marked drop for the alkyl sulfonate,

sodium w-butylsulfonate (solid points, Figure 2).

Since almost the same type of curve is displayed for the three different

kinds of aromatic sulfonates as was

displayed when the molecular weight was employed (Figure 1), it may be assumed that the volume of the mole

cule, rather than the molecular weight, was the determining factor in the toxi

city displayed by these three types of

compounds.

The benzenesulfonates display a defi nite trend towards increasing toxicity with increasing values for the para chor. An exception is sodium p-bromo benzenesulfonate, as this compound shows a definite increase in toxicity even though it has a lower parachor value than several of the other sodium benzenesulfonates. This deviation, to

gether with the slight variation in tox

icity with increasing parachor values

displayed by the other benzenesulfo

nates, may be indicative of the impor tance of the substituted group, and this factor may outweigh any effect

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Vol. 25, No. 11 TOXICITY OF SODIUM SULFONATES 1335

imparted by increasing the molecular

size or the molecular weight.

Toxicity Threshold and pH

The sodium sulfonates apparently do not belong to those compounds that exert their effect through a change in

the pH, for the pH values (Table I) were within the limits of tolerance of

Daphnia magna, these limits being about 6.0 to 8.7 with an optimum at

about 7.4 (1). The compounds, then,

probably belong to the truly toxic

group or the osmotically modifying group, but no information was gathered in this study on the osmotic pressure displayed by the concentrations of so

dium sulfonates employed.

Conclusions

1. Ten sodium sulfonates were bio

assayed with Daphnia magna and their 100-hr. toxicity threshold, 100-hr. tox

icity range, molecular weight, molec ular parachor, and pH at the 100 per cent toxicity level are reported.

2. The more complex the ring struc ture of the aromatic compounds, the

more toxic are the compounds ; thus, in order of increasing toxicity: benzene, naphthalene, anthraquinone.

3. Substitution of various groups on the benzene ring increases the toxicity, p-bromine imparting the greatest tox

icity, followed by 2,5-dichloro, 4-nitro

chloro-2-, p-hydroxyl, m-nitro and p

chlorine substitution. 4. Analysis of the data on the basis

of molecular weights yields two con clusions: the toxicity of the sodium benzenesulfonates tends to increase as the molecular weight increases until a level is reached, at which point the tox

icity increases more rapidly than does the molecular weight ; a direct relation exists between an increasing number of

rings, with a corresponding increase in molecular weight, and the toxicity.

5. The parachor data indicate : the sodium benzenesulfonates display a trend towards increasing toxicity with

increasing values of the parachor; a

direct relation exists between an in

creasing number of rings and the para

chor; the increase in toxicity with in

creasing number of rings is attribut able to the volume of the molecule rather than the molecular weight ; and the nature of a group substituted on the benzene ring may be of more im

portance than the size of the molecule or its weight.

6. The toxicity of the sodium sulfo nates to Daphnia magna is not attri butable to any effect the compounds

may have on the acidity or alkalinity of the test solutions.

Acknowledgments

The work reported in this paper was conducted on a project sponsored by the Louisiana Petroleum Kefiners'

Waste Control Council and adminis tered by the Department of Zoology,

Physiology, and Entomology, Louisiana State University. The author wishes also to acknowledge the aid of the Di vision of Besearch and Statistics of the State of Louisiana Department of Wild Life and Fisheries in the provision of

laboratory facilities.

References

1. Anderson, B. G., "The Toxicity Thresh olds of Various Sodium Salts Deter

mined by the Use of Daphnia magna. ' '

Sewage Works Jour., 18, 1, 82 (Jan., 1946).

2. Anderson, B. G., et al., "The Evaluation of

Aquatic Invertebrates as Assay Or

ganisms for the Determination of the

Toxicity of Industrial Wastes." Re

port by Ohio State Univ. Research Found, to American Petroleum Inst., New York, N. Y. (1948).

3. Freeman, L., "An Investigation into the

Toxicity of Certain Sodium Sulfonates on the Fresh-Water Fish, Lepomis

macrochirus." Progress Report to the Louisiana Petroleum Refiners' Waste Control Council. Baton Rouge, La.

(1950). 4. Freeman, L., and Fowler, I., "Toxicity of

Combinations of Certain Inorganic Compounds to Daphnia magna Straus.

' '

This Journal, 25, 10, 1191 (Oct., 1953).

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