United States Prevention, Pesticides EPA712-C-98-048
Environmental Protection and Toxic Substances January 1998
Agency (7101)
&EPA Fate, Transport and
Transformation Test
Guidelines
OPPTS 835.1220
Sediment and Soil
Adsorption/Desorption
Isotherm
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INTRODUCTION
This guideline is one of a series of test guidelines that have been
developed by the Office of Prevention, Pesticides and Toxic Substances,
United States Environmental Protection Agency for use in the testing of
pesticides and toxic substances, and the development of test data that must
be submitted to the Agency for review under Federal regulations.
The Office of Prevention, Pesticides and Toxic Substances (OPPTS)
has developed this guideline through a process of harmonization that
blended the testing guidance and requirements that existed in the Office
of Pollution Prevention and Toxics (OPPT) and appeared in Title 40,
Chapter I, Subchapter R of the Code of Federal Regulations (CFR), the
Office of Pesticide Programs (OPP) which appeared in publications of the
National Technical Information Service (NTIS) and the guidelines pub-
lished by the Organization for Economic Cooperation and Development
(OECD).
The purpose of harmonizing these guidelines into a single set of
OPPTS guidelines is to minimize variations among the testing procedures
that must be performed to meet the data requirements of the U. S. Environ-
mental Protection Agency under the Toxic Substances Control Act (15
U.S.C. 2601) and the Federal Insecticide, Fungicide and Rodenticide Act
(7U.S.C. I36,etseq.).
Final Guideline Release: This guideline is available from the U.S.
Government Printing Office, Washington, DC 20402 on The Federal Bul-
letin Board. By modem dial 202-512-1387, telnet and ftp:
fedbbs.access.gpo.gov (IP 162.140.64.19), or call 202-512-0132 for disks
or paper copies. This guideline is also available electronically in ASCII
and PDF (portable document format) from EPA's World Wide Web site
(http://www.epa.gov/epahome/research.htm) under the heading "Research-
ers and Scientists/Test Methods and Guidelines/OPPTS Harmonized Test
Guidelines."
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OPPTS 835.1220 Sediment and soil adsorption/desorption iso-
therm.
(a) Scope—(1) Applicability. This guideline is intended to meet test-
ing requirements of both the Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA) (7 U.S.C. 136, et seq.) and the Toxic Substances
Control Act (TSCA) (15 U.S.C. 2601).
(2) Background. The source material used in developing this har-
monized OPPTS test guideline are 40 CFR 796.2750 Sediment and Soil
Adsorption Isotherm and OECD 106 Adsorption/Desorption.
(b) Guidance information—(1) Prerequisites. Water solubility data;
suitable analytical method; boiling point; vapor pressure curve.
(2) Qualifying statements, (i) This method as described is not appli-
cable to substances which are not soluble in water to an extent which
can be measured analytically. It is also not applicable to compounds which
are unstable in the time scale of the test.
(ii) Although the methods can be applied to pure and commercial
grade substances, the possible effects of impurities on the results should
be considered.
(3) Recommendations, (i) It is emphasized that although three soil
types are broadly described under paragraph (c)(4)(i) of this guideline,
there is a wide variation of the soils used in different laboratories through-
out the world and variation in the test results is to be expected. It is not
possible to prescribe exactly the soils to be used, and experience with a
central store of so-called "standard soil" indicates that this approach also
presents problems.
(ii) This test has promised to give preliminary information on the
soil leaching behavior of substances. Therefore, substances of known soil
leaching behavior should be investigated. For reference substances in order
to establish this possibility see paragraph (g)(4) of this guideline.
(4) Standard documents. The following test guideline is based on
the references under paragraph (g) of this guideline. Certain modifications
have been introduced to minimize the disparity in the references with re-
gard to materials used, laboratory methodology, data presentation, and data
interpretation.
(c) Method—(1) Purpose, relevance, application, and limits of test.
(i) Adsorption-desorption data are necessary for the evaluation of the mi-
gratory tendency of chemicals into the air, water, and soil or sediment
compartments of our environment. They are needed to estimate, for exam-
ple, leaching through the soil, volatility from water and soil,
photodegradation in the adsorbed state on aerosol surfaces, and concentra-
tion in water or run-off from land surfaces into natural waters. Adsorption/
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desorption processes (= sorption processes) of chemicals have an effect
on transport processes and on their bioavailability. In the natural environ-
ment adsorption reduces the concentration of a chemical in aqueous solu-
tion.
(ii) Since soils have varying capacities for ion-exchange as well as
differing surface areas, pH, and redox potential, interaction with chemical
substances in an aqueous system is a complex process and cannot be com-
pletely defined by a simple testing scheme.
(iii) The resulting distribution between the adsorbed and solution
phase depends upon chemical parameters, properties of the adsorbent and
environmental parameters such as temperature, the ratio of soil to water
and ionic strength. The present test method is based upon a simplified
model which can serve as an initial sorption screening test for chemical
substances. When warranted, more extensive testing can be performed to
more accurately define the effect of a specific soil or environmental vari-
able (for instance to obtain isotherm data)—and these possibilities are
pointed out in this guideline.
(iv) The experimental procedure measures the decrease in concentra-
tion when aqueous solutions of a chemical substance are in contact with
three different soil types at room temperature.
(v) A CaCi2 solution (0.01 M) is used as the aqueous solvent phase
to improve centrifugation and minimize cation exchange.
(2) Definitions and abbreviations, (i) The definitions in section 3
of the Toxic Substances Control Act (TSCA) and the definitions in 40
CFR Part 792—Good Laboratory Practice Standards apply to this test
guideline. The following definitions also apply to this test guideline.
Soil is the unconsolidated mixed mineral and organic material of the
earth which consists of the three-phase system: Mineral and/or organic
material/water/air, and which serves as a natural medium for the growth
of plants.
Sediment is the unconsolidated material deposited at the bottom of
natural water and which consists of the phases mineral material/water/
(gas).
Adsorption in the present method does not distinguish between sur-
face adsorption and such processes as surface catalyzed degradation, bulk
adsorption, or chemical reaction.
(ii) The following abbreviations and units used in this guideline:
a is concentration in soil blank, in milligrams per liter (mg/L).
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c is decrease in concentration (Q = Ce) in milligrams per liter
(mg/L).
Ci is initial concentration (= weight of test substance/volume solution)
in milligrams per liter (mg/L).
Ce is final concentration, in milligrams per liter (mg/L).
Co is concentration in no-soil control, in milligrams per liter
(mg/L).
Ce is final concentration after correction, (Ce' = a) in milligrams per
liter (mg/L).
d is volume of solution and of each wash, in liters (L).
/ is concentration in first desorption extraction (wash), in milligrams
per liter (mg/L).
GA is quantity in no-soil control [Cid(l,000)] in micrograms (jig).
GD is total quantity desorbed [(l,000)(j + 1)] in micrograms (jig).
GR is quantity remaining on soil after desorption (x - GD) in
micrograms (jig).
h is quantity in first wash (g x d) in milligrams (mg).
/ is quantity in v, [Ce x v(l/l,000)], in milligrams (mg).
j is quantity desorbed by first wash (h - i) in milligrams (mg).
k is concentration in second wash, in milligrams per liter (mg/L).
/ is quantity in second wash (k x d) in milligrams (mg).
m is quantity of soil (oven-dried equivalent), in grams (g).
m is oven dried weight of soil (q = pq) in grams (g).
p is fraction of moisture in soil.
q is air dried weight of soil used, in grams (g).
S is soil as described under paragraph (c)(4)(i) of this guideline.
t is temperature at which test was run in degrees Celsius (°C).
T is quantity in solution at equilibrium [Ced( 1,000)] in micrograms
(MB)-
x is quantity adsorbed [(c x d)( 1,000)] (or, GA = T) in micrograms
(MB)-
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x/m is concentration adsorbed in micrograms per gram (|ig/g).
V is volume of solution recovered from adsorption test in milliliters
(mL).
v is volume of solution remaining in soil (d - 1,000 - V) in milliliters
(mL).
(3) Reference substances. The following reference compounds need
not be employed in all cases when investigating a new substance. They
are listed so that the method can be calibrated from time to time and to
offer the chance to compare the results when another method is applied.
The values presented in the following Table 1. are not necessarily rep-
resentative of the results which can be obtained with this test guideline,
as they have been derived from an earlier version of it.
Table 1.—Reference Substances2
Naphthalene
Soil I
Soil II
Soil III
2.4-Dichlorophenoxy acetic
acid
Soil I
Soil II
Soil III
Soil character
very strongly-strongly acid sandy soil
moderately or slightly acid loamy soil
slightly alkaline loamy soil
very strongly-strongly acid sandy soil
moderately or slightly acid loamy soil
sliahtlv alkaline loamv soil
K00i
4205 (739-7671)
7382 (772-20 088)
17009 (1441-32577)
175.9 (119.0-231.0)
1084 (693-1444)
225.6 (62.1 - 389.0)
1 Total mean and range of mean values (in parentheses) reported by the participants of the OECD/
EEC Laboratory Intercomparison Testing, Part II.
2 p-Chloroaniline is suggested in addition to the above.
(4) Principle of the test method, (i) Three soils which vary signifi-
cantly in cation exchange capacity, clay content, organic matter content,
exchangeable cations, and pH are selected:
(A) Very strongly to strongly acid sandy soil (pH 4.5-5.5, clay con-
tent 5 percent, organic matter content 0.6-3.5 percent (e.g. Spodosol).
(B) Moderately or slightly acid loamy soil, pH 5.6-6.5; clay content
15-25 percent, organic carbon content 0.6-2.3 percent (e.g. Alfisol).
(C) Slightly alkaline loamy soil, pH 7.1-8.0; CaCO3 1-10 percent;
clay content 11-25 percent, organic carbon content 0.6-2.3 percent (e.g.
Entisol).
(D) All soils should be classified in terms of the US comprehensive
soil classification system (on the level of the soil family) and additional
information may be included (e.g. the national soil classification). The
physical and chemical properties of Alfisol are given by:
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Physical and Chemical Properties of Alfisol
Soil order: Alfisol
Soil series: Crider
Location: Gallatin County, Illinois, California
Classification: typic paleudalf, fine-silty, mixed,
mesic
Horizon: A
percent sand: 1.2
percent silt: 86.6
percent clay: 12.2
percent organic carbon 1.0
carbonate as CaCOS -
pH (1:1 H20): 7.2
cation exchange capacity 13.5
(meq/100 g).
extractable cations (meq/100 g).
Ca 8.4
Mg 2.8
Na -
K 0.7
H 1.6
Clay Fraction Mineralogy: >50% Montmorillonite; 5-20%
mica; <5% kaolinite (36-120 cm
depth)
(ii) All three soils are common in temperate zones, but are not rep-
resentative of arid or tropical regions. They may also be used for further
testing designed to study behavior in sedimentary systems.
(iii) The method first establishes that a suitable analytical procedure
exists, then proceeds to answer the question whether the chemical sub-
stance has a tendency to be strongly, weakly or nonadsorbed from a dilute
aqueous solution by any of the three soil types. If little or no adsorption
occurs, no further sorption tests are performed because the chemical will
not be retained in soil media.
(iv) If adsorption is moderate or high (A > 25%), a single desorption
test is performed to establish whether or not this chemical is likely to
be retained in soil media. If it is readily desorbed (D > 75%), no further
sorption tests are required; if only poorly desorbed (D < 75%), the screen-
ing test is considered to be complete and the investigator has the option
of proceeding to the secondary or advanced phase in which an adsorption
isotherm is determined and a mass balance established.
(v) Under the advanced test, the absorption kinetics are determined.
If neither a plateau value nor a mass balance value is obtained, check
for biotic and abiotic degradation. If a plateau value or a mass balance
value is obtained, the absorption isotherms are determined. If the soil envi-
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ronment is not considered a likely as a trap for the substance, no further
tests are needed because the soil media are of minimal importance. The
information should be considered for hazard assessment of the substance.
If the soil environment seems to be a likely trap, consider the fate of the
substance in soil, and consider the information for hazard assessment of
the substance.
(5) Quality criteria—(i) Repeatability. The repeatability of the
measurement is not well known at present, as is indicated with two ref-
erence compounds named under paragraph (c)(3) of this guideline. Stand-
ard deviation of the mean should be determined.
(ii) Sensitivity. The sensitivity of the test method depends on the
water solubility of the test substance.
(iii) Specificity. This method as described is not applicable to water
insoluble gases, hydrolytically unstable compounds, chemicals which may
suffer catalytic decomposition on soil surface, or in cases where analytical
methods are unavailable in the 0.01 mg/L range.
(iv) Possibility of standardization. The method itself can be stand-
ardized, but the soils probably cannot. There is no possibility of automa-
tion.
(d) Description of the test procedure—(1) Preparations. The ad-
sorption test should be run using sieved soil to be less than or equal to
2 mm (N° 10 mesh) soil which has either been stored damp since collec-
tion or air-dried and reequilibrated with approximately twice its weight
of water before use. (This reequilibration should be carried out for a mini-
mum of 24 h by gently tumbling the soil and water together.) In either
case the dry weight content (100 °C for approximately 12 h) of the soil
should be determined.
(2) Test conditions, (i) The three soil samples selected for this study
should have a pH between 4 and 8, an organic carbon content between
0.6 and 3.5 percent. Suggested soil types are described under paragraph
(c)(4)(i) of this guideline.
(ii) Distilled or deionized water are used to prepare the CaCk solution
(0.01 M) as the solvent.
(iii) Containers should be made of materials that adsorb negligible
amounts of the chemical to be tested. Other details of container design
are not critical, although handling and transfer errors are minimized by
using centrifuge tubes. The test solutions listed under paragraph (d)(3)(ii)
through (iv) of this guideline should be added to their respective test con-
tainers and equilibrated (without soil sample). The containers should be
closed during agitation and centrifugation to avoid volatility losses.
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(iv) The actual determination should be carried out in duplicate using,
e.g. 1:5 w/w soil/solution ratio.
(v) The experiment should be run at room temperature.
(3) Performance of the tests — (i) Preliminary test. (A) To assure
applicability of the method, especially the analytical method, to a given
chemical substance the following test should be performed.
(B) The soil is equilibrated with the aqueous phase (0.01 M
as described under paragraph (d)(3)(ii)(A) of this guideline. The aqueous
phase is separated by centrifugation, and sufficient test chemical is added
to form a solution of approximately one-half saturation and not exceeding
5 mg/L, unless the analytical method cannot be operated at this level. The
solution is then subjected to chemical analysis and, if satisfactory, the
screening test can be performed. A satisfactory, reproducible analytical
method is essential to this method.
(ii) Screening test: Adsorption. (A) The solution of test chemical
is prepared in 0.01 m CaCl2 at a level of one-half saturation but less than
5 mg/L maximum, unless otherwise dictated by the analytical method.
(B) The adsorption step is performed in duplicate upon this single
concentration solution using the three soil types.
(C) Blanks include each of the three soils with only 0.01 M
solution (no test chemical) and a single control of the test chemical solu-
tion with no soil. These blanks permit correction for analytical interference
due to soil extracts as well as correction for interaction between chemical
and container or handling losses.
(D) The soil is added to the test solution and agitation is begun imme-
diately. Agitation must be continuous and sufficient to maintain the ad-
sorbent (soil) in suspension, but should not be so vigorous as to cause
the breakdown of the soil structure.
(E) Agitation is continued for 16 h.
(F) After agitation, this suspension is centrifuged to obtain a clear
solution. The volume of clear aqueous solution is measured and either ana-
lyzed immediately for parent compound concentration or stored under re-
frigeration (5 °C) to minimize biodegradation.
(G) The three blanks and control are subjected to precisely the same
steps as the test systems and appropriate correction is applied as necessary.
(H) The volume of equilibrium test solution retained in the solid
phase following centrifugation and the volume, V, of the supernatant must
be recorded for subsequent correction of the desorption data.
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(iii) Screening test: Desorption. (A) If no significant adsorption (ap-
proximately 25 percent or less) occurs, the desorption part of the test is
not called for.
(B) If medium to high adsorption occurs (A > 25%), desorption test-
ing is carried out.
(7) To each solid phase is added a volume V (see paragraph
(d)(3)(ii)(H) of this guideline) of 0.01 M CaCk solution and this mixture
gently agitated for 16 h. It is then centrifuged and the supernatant retained
for analysis. The whole desorption procedure is then repeated on the solid
phase with a further quantity of fresh 0.01 M CaCk solution.
(2) The solute retained in the entrained equilibrium test solution under
paragraph (d)(3)(ii)(H) is assumed to be completely removed in the two
washings along with the desorbed material and an appropriate correction
applied to decrease the measured concentration by the calculated amount
of retained solute.
(3) The determination of the amount and the characterization of the
chemical remaining in the aqueous solution phase should be accomplished
by appropriate analytical methods.
(iv) Advanced test: Adsorption. (A) If the screening test dem-
onstrates a significant degree of chemical adsorptivity, adsorption
isotherms may be helpful in predicting mobility in soil/water systems.
(B) To ascertain that equilibrium conditions will be met in the ad-
vanced test, a series of samples of each soil is prepared using one conven-
ient concentration of test chemical. These samples are analyzed after ap-
propriate time intervals. If no decomposition of the test chemical occurs,
its concentration in the aqueous phase will eventually reach a plateau
value. The time required to reach this plateau value is the minimum agita-
tion time. If no plateau value can be reached abiotic or biotic degradation
must be considered.
(C) For the adsorption isotherm determination, four initial concentra-
tions, Ci, of approximately 0.04, 0.20, 1.00, and 5.00 mg/L are prepared
and the adsorption test performed on each as described under paragraph
(d)(3)(ii) of this guideline. In some cases the low solubility of the test
chemical will prohibit the use of some of the above concentrations. In
these cases the adsorption isotherm is measured using high and low (other
than 0.00) equilibrium solution concentrations of the chemical that are at
least 1 order of magnitude apart.
(D) Blanks are identical with those described under paragraph
(d)(3)(ii)(C) of this guideline.
(E) An analytical control sample (no soil) should also be run at a
convenient test concentration, not to exceed approximately 1 mg/L.
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(F) Analysis and correction are as before.
(v) Mass balance. (A) A mass balance should be performed by deter-
mining, in addition to the concentrations in the solutions, the concentration
of the substance in the soil. This additional measurement needs only be
performed after reaching the equilibrium plateau and only for one con-
centration with each soil.
(B) The adsorbed chemical substances remaining on the soil particles
are removed so that a mass balance can be attempted. The extraction me-
dium should be a suitable solvent in which the chemical of interest is
very soluble (minimum 1 mg/L). A volume of suitable solvent equal to
the volume of aqueous solution originally used to attain equilibrium is
added to the adsorbent and shaken vigorously for 10 min.
(C) The mixture is centrifuged to obtain a clear solution.
(D) The extraction procedure is performed 3 times with equal vol-
umes of fresh solvent which are then analyzed.
(E) The aqueous solution phase is analyzed for the parent chemical
under test.
(e) Data and reporting—(1) Treatment of results—(i) Soil charac-
terization. Report data on soil using the format provided under paragraph
(f) of this guideline, DATA SHEET FOR SEDIMENT AND SOIL AD-
SORPTION/DESORPTION ISOTHERM, part A. Soils used as adsorbents.
(ii) Screening test. (A) The data required are:
(7) m = dry weight of soil employed (g)
(2) Ce = concentration of substance remaining in solution (V) in the
adsorption step (g/L)
(3) Ci = concentration of substance in solution in the first wash (g/
L)
(4) C2 = concentration of substance in solution in the second wash
(g/L)
(5) Vo = original volume of solution employed (mL)
(6) V = volume of solution obtained after the adsorption step (mL)
(7) G = quantity of material recovered from the soilless control (g)
(B) The calculations to be carried out are as follows:
(7) The percent of the chemical adsorbed is calculated as:
A = (G - Ce xV0)/G x 100 = x/G x 100
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(2) The percent of the adsorbed material which is desorbed is cal-
culated as
D = [(Ci + C2)V - (V0 - V)Ce]/x x 100
(3) The percent of the adsorbed material which is not desorbed is
calculated as:
R = [G - (Ce + Ci + C2)V]/x x 100
(4) The adsorption coefficient for the determination is calculated as:
K' = (x/m)/Ce
(5) The adsorption coefficient should also be calculated as a function
of the organic carbon content of the soil:
K'oc = K'(100/percent organic carbon)
(iii) Advanced test. (A) The time required to reach the equilibrium
concentration, Ce, should be determined.
(B) In addition to using the data to perform the calculations in the
screening test under paragraph (e)(l)(ii) of this guideline, the data should
be plotted according to the Freundlich equation. While the equation is em-
pirical it is widely used and has been found to describe adequately the
adsorption process in dilute solution. The equation has the form:
(x/m) = (K) + (Ce^)
K and 1/n are empirical constants characteristics of the test compound and
the sorbent used in the test. Graphically, K is the x/m intercept of the
isotherm plot at Ce = 1 and 1/n is the slope of the line when log x/m
is plotted on the ordinate (vertical axis) and log Ce is plotted on the ab-
scissa (horizontal axis). The intercept is an indicator of sorption capacity
and the slope of sorption intensity.
(iv) Mass balance. A mass balance should be performed for the par-
ent compound. The combined concentrations of the parent chemical in the
aqueous phase and the organic solvent extracts are subtracted from the
initial concentrations of parent compound and reported. A reasonable hy-
pothesis should be submitted to account for any discrepancy significantly
greater than the experimental error.
(v) Adsorption isotherm and mass balance data format. (A) The
following format is used for presenting adsorption isotherm data:
Adsorption Isotherm Data
x/m
Ce
log (x/m)
log Ce
10
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Adsorption Isotherm Data—Continued
x/m
Ce
log (x/m)
log Ce
(B) Format for graphing adsorption isotherm data for sediment or soil
samples:
(7) Graph 1.—Abscissa is Ce (jig in solution); ordinate is x/m (jig
adsorbed per gram of soil).
(2) Graph 2.—Abscissa is log Ce; ordinate is log (x/m).
(Log (x/m) = log K + 1/n log Ce; intercept = log K; slope = 1/n; R2 =
coefficient of determination for the regression analysis.
(C) The following format should be used for presentation of mass
balance data.
Mass Balance Data
Data
Original amount (u,g)
Amount absorbed at plateau (u,g)
Amount in equilibrium solution (u,g)
Unaccounted material [u,g/(a — (b — c))]
Percentaae of unaccounted material [(b + cVa x 100 = %1
Soil I
Soil II
Soil III
(2) Test report. Information should be submitted for the soils se-
lected using the data sheet provided under paragraph (f) of this guideline.
(i) Screening test. Report the percent of chemical adsorbed, A, and
if necessary, the percent of adsorbed material which is desorbed, D, and
the percent of the adsorbed material which is not desorbed, R, for each
soil. Also report K' and K'oc and the concentration Ce used in the calcula-
tion (refer to paragraph (e)(l)(ii)(B) of this guideline).
(ii) Adsorption/desorption test report The following Tables 2. and
3. list the data required.
Table 2.—Adsorption Test
Data
Soil I
Soil
Soil III
concentration of test substance (mg/L)
after contact of... hours with soil
correction for blank with soil
correction for blank without soil
final corrected concentration (mg/L)
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Table 2.—Adsorption Test—Continued
Data
initial concentration of test solution (mg/L)
decrease in concentration (mg/L)
quantity adsorbed (u,g)
quantity of soil (g of oven-dried equivalent)
quantity adsorbed (u,g) per gram of soil
temperature of test (°C)
volume of solution recovered after centrifugation (ml)
volume of solution not recovered (ml)
corresoondina auantitv of test substance (ma)
Soil 1
Soil II
Soil III
Table 3.—Desorption Test
Data
concentration in combined washings (mg/L)
corresponding quantity of test substance (mg)
auantitv desorbed (ma)
Soil 1
Soil II
Soil III
(iii) Advanced test. (A) The time for reaching the plateau value
should be recorded together with the raw data.
(B) The amount of adsorbed chemical (x) per unit amount of adsorb-
ent (m) (usually expressed as micrograms per gram (|ig/g) soil) is defined
as x/m. This value is calculated from the difference between the initial
concentration of the chemical in the solution and the equilibrium solution
concentration of the chemical (Ce), the volume of the solution and the
weight of the soil (see paragraph (e)(2)(ii) of this guideline.
(C) Average values of the adsorbed chemical, x/m, are plotted graphi-
cally as a function of equilibrium concentration, Ce, for each soil.
(D) The results can also be evaluated by plotting log (x/m) versus
log Ce. If the relationship is linear then the Freundlich isotherm
x/m = K x Ce 1/n
may be applied in its logarithmic form
log x/m = log K + 1/n log Ce
and the linear regression calculated. If the regression is significant (for
N = 5, P = 5%, R2 > 0.77), the adsorption constant K and the constant
1/n should be reported along with all raw data (see Mass Balance under
paragraph (e)(l)(iv) of this guideline).
(E) KOC should be determined from K and recorded.
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(f) Data report forms. Sample data sheets for reporting test results
are attached, and may be duplicated.
DATA SHEET FOR SEDIMENT AND SOIL ADSORPTION/
DESORPTION ISOTHERM
Laboratory:
Date:
Test Substance:.
Formula:
Name (IUPAC):.
A. Soils used as adsorbents
Soil order
Soil series
Classification
Location
Horizon
percent sand
percent silt
percent clay
percent organic matter
percent organic carbon
carbonate as CaCOS
percent insoluble carbonates
pH (1:1 Ho)
Cation exchange cap (MEQ/100 g)
Extractable cations (MEQ/100 g)
Ca
Mq
Na
K
H
I
II
III
Special Chemical/Mineralogical Features:
Clay Fraction Mineralogy:
13
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B. Results of preliminary test
Test substance:
Sample purity:
Saturation concentrations:
Concentration of the test solution (show calculation):
Description of a suitable analytical method:
14
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C. Results of screening test
1. Adsorption
temperature,
°C
C control
C,
Ce
x
m
x/m
G
V
So
il 1
So
1 II
Soil
III
2. Desorption
temperature,
°C
Ci
D
R
So
il 1
So
1 II
Soil
III
3. Final data
temperature t °C
initial concentration, Ci
percent of chemical adsorbed on adsorbent, A
percent desorbed D
percent of the original quantity found in the control sample
remaining on adsorbent after desorption, R
adsorption coefficient K'
adsorption coefficient based on organic carbon content K'00
final concentration after correction. C,,
1
II
III
15
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D. Results of advanced test
1. Adsorption kinetics
Soil Type I:
Temperature:
Time for reaching Ce
time
C,
Ce
Soil Type II:
Temperature:.
Time for reaching Ce
time
C,
Ce
Soil Type III:
Temperature:_
Time for reaching Ce
time
c,
Ce
16
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2. Adsorption Isotherms for each concentration (Ci)
c,
Ce
X
m
x/m
c,
Ce
x
m
x/m
C,
Ce
x
m
x/m
1
Soil
II
III
1
Soil
II
III
17
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(g) References. The following references should be consulted for ad-
ditional background material on this test guideline.
(1) Aharonson, N. and U. Kafkafi. Adsorption, mobility and persist-
ence of thiabendazole and methyl 2-benzimidazole carbamate in soils.
Journal of Agrcultural and Food Chemistry 23:720-724 (1975).
(2) Environmental Protection Agency, Office of Pesticide Programs.
Guidelines for registering pesticides in the United States. FEDERAL REG-
ISTER 40, No. 123, 26881 (1975).
(3) FEDERAL REGISTER 44 FR 16257-16264 (1979).
(4) Hamaker, J.W. The interpretation of soil leaching experiments,
in Environmental Dynamics of Pesticides (ed. R. Hague and V.H. Freed),
pp 115-134, Plenum, N.Y. (1975).
(5) Harvey, R.G. Soil adsorption and volatility of dinitroaniline herbi-
cides. Weed Science 22:120-124 (1974).
(6) Laskowski & McCall, Communication to W.M.J. Strachan, July
1978.
(7) Murray, D.S., P.W. Santlemann, and J.M. Davidson. Comparative
adsorption, desorption, and mobility of disporpetryn and prometryn in soil.
Journal of Agricultural and Food Chemistry 23:578-582 (1975).
(8) Saltzman, S. et al. Adsorption-desorption of parathion as affected
by soil organic matter. Journal of Agricultural and Food Chemistry 20:
1224-1226 (1972).
(9) Unweltbundesamt (Draft: Test protocol for the determination of
adsorbability. Sept. 1979. with comments from Prof. Brummer, Kiel, and
Prof Lagally, Kiel).
(10) Weber, J.B. Model soil system, herbicide leaching, and sorption.
P. 145-60. In R.E. Wilkinson, ed., Research methods in weed science.
Southern Weed Science Society (1971).
(11) Wu. C.H. et al. Napropamide adsorption, desorption, and move-
ment in soils. Weed Science 23: 454-457 (1975).
18
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