0038-075X/06/17101-29–38
Soil Science
Copyright * 2006 by Lippincott Williams & Wilkins, Inc.

January 2006
Vol. 171, No. 1
Printed in U.S.A.

COPPER MOBILITY IN SOILS AS AFFECTED BY SEWAGE SLUDGE
AND LOW MOLECULAR WEIGHT ORGANIC ACIDS
L. Bahaminyakamwe4, J. Simunek3, J. H. Dane1, J. F. Adams2, and J. W. Odom2
Copper is an essential micronutrient, but at increased concentrations,
it quickly becomes toxic to plants, and remediation is needed. Because
the land disposal of copper containing sewage sludge is increasing eachyear, there is a need to evaluate the mobility of copper in soil as affectedby sewage sludge and low molecular weight organic acids (citric acid andoxalic acid). Copper mobility was studied in a Marvyn soil (fine-loamy,
siliceous, subactive, thermic, Typic Kanhapludult) without or with 1 of 2
sewage sludges from the Birmingham, Alabama area. A total of 5column experiments were performed. The columns were leached withsolutions containing potassium sulfate (10j2 M/L) to maintain properionic strength, in addition to different combinations of copper, oxalic
acid, and citric acid. The Cu2+ concentration in all applied solutions was1000 mg Cu2+ per kg of solution. In the column experiments containing
sewage sludge, the effluent copper concentration did not reach the
influent concentration. In the column experiments without sewage
sludge, the influent copper concentrations were easily reached in theeffluent, independent of the addition of oxalic or citric acid. A batch
equilibrium study showed that both sewage sludges could adsorb morethan 50,000 mg of copper per kilogram of sewage sludge, compared with
1250 mg of copper per kilogram of Marvyn soil. This amount is so highthat sewage sludges could possibly be used for copper detoxification inmine tailings or farm lands where copper pollution is a potential
problem for vegetation. (Soil Science 2006;171:29–38)
Key words: Maximum adsorption, copper, breakthrough curves,
HYDRUS-1D, Langmuir isotherms, sewage sludge, mine tailings.

NLIKE for other heavy metals, minerals
governing Cu2+ solubility in soils are notwell known (Lindsay, 1979). Most of the Cu2+
minerals are more soluble than the soil Cu(copper adsorbed to soil) and will dissolve toform soil Cu (Lindsay, 1979; Alloway, 1995).
Below pH 6.5, the ion Cu2+ will be the domi-

nant copper species in soil solution, whereas
CuOH02 is the major solution species above
pH 7. The hydrolysis species Cu(OH)+ becomessignificant between pH 6.5 and 7. Several Cu2+
complexes, inorganic and organic, also contribute to total copper in soil solution. Sulfate(CuSO04 ) and carbonate (CuCO03 ) complexes
are important inorganic complexes, because, according to Lindsay (1979), at a concentration of2+
and CuSO04
10j2.36 M SO2j
4 , activities of Cu
are equal, and at CO2 pressure of 0.005 MPa, theactivities of CuCO03 and CuðOHÞ02 are equal.
The contributions of the other inorganic complexes are negligible, and total inorganic copperin soil solution can be estimated by the following equation (Lindsay, 1979):

U

1Professor, Agronomy and Soils, 201 Funchess Hall, Auburn, AL 36849-5412.

E-mail: danejac@auburn.edu
2Associate Professors, Agronomy and Soils, 201 Funchess Hall, Auburn, AL

36849-5412.
3Professor, Department of Environmental Sciences, University of California,
Riverside, CA
4Research Associate, Agronomy and Soils, 201 Funchess Hall, Auburn, AL
36849-5412. Tel. (334)844-4100 Fax (334) 844-3945. Dr. L. Bahaminyakamwe
is corresponding author. E-mail: bahamla@auburn.edu½Cu inorg  ¼ ½Cu2þ  þ ½CuOH þ  þ ½CuSOo4 þ ½CuðOHÞo2  þ ½CuCOo3 

Received May 23, 2005; accepted July 19, 2005.
DOI: 10.1097/01.ss.0000187349.31987.ff

ð1Þ

29

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

30

BAHAMINYAKAMWE, ET AL.

Reactions controlling Cu2+ in soil solution
are similar to those controlling other micronutrients (Tisdale et al., 1993), such as precipitationdissolution, plant absorption-exudation, andimmobilization-mineralization. However,adsorption-desorption reactions are of the greatest interest because they most directly affectthe levels of copper in the soil solution. Most
organic complexes of copper are soluble inwater and may not be subject to adsorptiondesorption reactions. To determine if organiccopper complexes are adsorbed to the soil,
concentrations of Cu2+ in solution are measured
in the presence and the absence of an appropriate organic chelating agent (i.e., oxalic acid,citric acid, and sewage sludge), and the breakthrough curves are compared to establish whichorganic compound is retarding Cu2+ movement
the most. McLaren et al. (1981) found that totalsolution copper concentrations were increased
above equilibrium levels for Cu2+ by the presence of soluble organic complexes. McBrideand Blasiak (1979) found that 99.9 % of totalsoluble Cu2+ was in complexed forms at pH 8.
Hodgson et al. (1966) estimated that 99% of
Cu2+ was organically complexed in calcareous
soils. Stevenson and Fitch (1981) found that theamount of Cu2+ that can be bound to humic
and fulvic acids is equal to the content of acidic
groups. This corresponds to the sorption of from48 to 160 mg of Cu2+ per gram of humic acid
(Kabata-Pendias and Pendias, 1992). High sorption of Cu2+ by peat-muck soil and humic acidhas been reported (McLaren et al., 1981).
Besides humic and fulvic acids, soils containlow molecular weight organic acids such as
aliphatic carboxylic, phenolic, and amino acids(Stevenson and Fitch, 1981). These acids are
considered soluble, and their presence may
maintain Cu2+ in the soil solution. Bloomfield
et al. (1976) suggested that Cu2+ may form
negatively charged organic complexes not retained by clay minerals. McBride (1981) foundthat the effects of organic compounds on Cu2+
depend on the nature of the adsorbing surface aswell as the type of organic compound. For example, fulvic and glutamic acids were found toenhance Cu2+ adsorption at a given pH, whereas citric acid and EDTA prevented adsorption
by maintaining Cu2+ in soil solution (McBride,1981).
Adsorption and desorption of heavy metal
cations are important processes in soils, because
they determine the availability of the cations toplants. They also affect the mobility of cations in

SOIL SCIENCE

the soil profile. Excellent reviews have been
published describing the adsorption-desorption
behavior of heavy metal cations in soils in thepresence of organic chelates (Ponizovsky et al.,
1999; Temminghoff et al., 1999). Specific adsorption of copper in soils has been evaluated(McLaren and Crawford, 1973; Forbes et al.,
1976; McLaren et al., 1981; McBride, 1981).
The copper ion is specifically adsorbed bysilicate clays, organic matter, iron, aluminum,or manganese oxides. Among all the divalentcations, it is the most strongly held by iron andaluminum oxides (Tisdale et al., 1993). The
mechanism of this adsorption is a chemisorption
process involving the formation of Cu-O-Al or
Cu-O-Fe surface bonds, which is controlled by
the quantity of surface OHj groups (KabataPendias and Pendias, 1992; Tisdale et al., 1993).
These OHj groups are pH-dependent, andtherefore, the adsorption of Cu2+ is a functionof pH (Kabata-Pendias and Pendias, 1992).
In most soils at pH 5.5, copper may bepresent as specifically adsorbed ions, which areconsidered to be part of the solid phase. These
ions cannot be removed by cation exchange
processes when large quantities of other cations
are added to the soil (McLaren and Crawford,
1973; Baker and Senft, 1995). The amounts ofcopper ions which can be removed by exchange
reactions will be definitely affected by the pH of
the solution. McLaren et al. (1981) studied theadsorption of copper by individual soil components at equilibrium with copper concentrations
normally found in natural soils and concluded
that copper adsorption isotherms were essentially linear. They also found that oxides andorganic materials adsorbed the greatest amountsof copper. They, however, found little effect on
copper adsorption by changes in pH or background concentrations of cations within theionic strength and pH range found in agricultural soils. On the other hand, Sauvé et al. (2000
and 2003) found that the partitioning coefficients of copper in organic and inorganic soils
were largely predicted by the pH alone. Poloet al. (1999) studied the effects of sewage sludge
on copper adsorption by soils and found that
copper adsorption by soils was decreased. In
other words, copper remaining in soil solutions
was increased in sewage sludge–treated soils
despite the low copper concentration in the
sewage sludge.
The objectives of this study were to determine (1) the adsorption-desorption of copperin the presence of oxalic acid, citric acid, andCopyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

VOL. 171 ~ NO. 1

COPPER MOBILITY IN SOIL AND SEWAGE SLUDGESTABLE 1

Soil physicochemical characterization
AnalysispH
P (double acid)
Ca (double acid)Mg (double acid)
K (double acid)
CEC
Organic matter
Particle size
Sand
Silt
Clay

Unit

Values

mg/kg
mg/kg
mg/kg
mg/kg
mmol (+)/kg
%

6.6
46.0
150.0
11.5
60.5
45
2.6

%
%
%

79
13
8

sewage sludge and (2) the effects of oxalic acid,citric acid, and sewage sludge on the transportparameters of copper using breakthrough curves.
The results will improve our understanding ofcopper retention in biosolid-amended soils andthe observed copper detoxification in minetailings receiving sewage sludge.
MATERIALS AND METHODSA Marvyn loamy sand soil (fine-loamy, siliceous, subactive, thermic, Typic Kanhapludult),
Ap horizon, from the Auburn Cuellars Rotation experiment (plot 1) was used in this study.
The soil pH was measured using a pH meter(Beckman Instrument Inc. Model 71) with a
combination glass electrode. The measurements
were taken 30 min after mixing 20 g of dry soil
and 20 mL of deionized water to make a soil/
solution ratio of 1:1 on a weight basis (McLean,
1982). The pH meter was calibrated with pH
4– and pH 7–certified buffers, and the soil samples and water were remixed immediately before
a reading was obtained. Particle size analyses
were carried out by the Bouyoucos hydrometer
method as described by Gee and Or (2002).
Exchangeable cations and CEC were determined using 1 N NH4OAC at pH 7 as describedby Thomas (1982). The ammonium concentrations (NH4+) were determined using the
microplate method as described by Sims et al.
(1995). The total NH4+ contents were used toestimate the CEC of the soil at pH 7. The soil
chemical characterization is summarized inTable 1. Sewage sludges and soil were analyzed
for total element composition using the method
described by Baker and Amacher (1982). Twograms of soil or sewage sludge was transferred
to a porcelain crucible and heated overnight at
450 -C to destroy organic matter. The ashes

31

were transferred into a 100-mL polypropylene
beaker, and 10 mL of a 30% H2O2 solution wasadded to the beaker and evaporated to dryness at
90 -C. The treatment was repeated until thesample no longer effervesced on addition of
H2O2. Three drops of concentrated H2SO4 and10 mL of a 48% HF solution were added to thebeaker and evaporated to dryness at 125 -C in asand bath. The treatment was repeated twice,then additions of 15 mL of a concentrated
HNO3, 2 mL of concentrated H2SO4, and 5 mLof a 60% HClO4 were made, and the heating
continued until strong fumes of SO3 were
produced. After cooling the polypropylene
beakers, 25 mL of deionized water was added
to complete the extraction of all the elements.
Total concentration of copper and other elements was determined by ICP-OES (inductively
coupled argon plasma-optical emission spectrophotometry). The results are summarized inTable 2.
Column Experiments
Figure 1 represents the setup for the column experiments. The column was a Plexiglas
cylinder, 30 cm long with a diameter of 5 cm.
The column was filled with the Marvyn soil(columns 1, 2, and 3) at a bulk density of 1.5 g I
cmj3. When sewage sludge was used (columns
4 and 5), 200 g of soil was mixed with 20 g ofsewage sludge, making a ratio of 10:1 soil/
sewage sludge, and the mixture was placed in
the bottom quarter of the cylinder (about 7.5 cmof height). The remaining part of the cylinder
was packed with the Marvyn soil. Each column

TABLE 2
Soil and biosolids total elementary analysis
Analysis

Unit

Village
Creek waste
water plant

Trussvillewaste water
plant

Soil

Ash
Total P
Total Ca
Total Mg
Total K
Total Cu
Total Ba
Total Cd
Total Co
Total Cr
Total Na
Total Ni
Total Zn

%
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg
mg/kg

44.0
87434.4
20799.1
4458.62718.6
472.8
75.5
4.0
6.8
58.9
1180.2
26.3
1869.642.769754.9
18758.8
2800.33710.91413.4
24.1
2.9
7.4
34.8
1200.425.6
1146.3

97.4
191.3
1223.7374.1
1631.8
2.4
0.2
0.3
2.5
5.4
83.8
1.9
8.6

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

32

BAHAMINYAKAMWE, ET AL.

SOIL SCIENCE

Fig. 1. Schematic representation of the column experiment apparatus.

medium was dry at the start of the experiment.
The initial potassium content of the soil andsoil/sewage sludge mixtures, as determined by
the water extract method, was 29.6 (soil), 54.7
(mixture soil/sewage sludge 1), and 112.6 mg/kg(mixture soil/sewage sludge 2). Potassium content in the soil sample, as determined in the
double-acid method, was 60.5 mg/kg (Table 1).
No copper was detected in the soil sample or
the mixtures by the water extract method or
the double-acid method (Table 1). The column
was leached with a copper solution containing
1000 mg of copper per kilogram of solution(1.5710j2 M/L CuSO4), and the effluent wascollected in sample tubes every 10 min. Oxalic
acid (10j3 M/L) or citric acid (10j3 M/L) was
added to the solution only in case that low
molecular weight organic acid was needed.
Potassium sulfate (10j2 M/L K2SO4) served as
background electrolyte to keep the ionicstrength of the effluent solution constant. Witha flow rate of 1.2 mL/min maintained by aperistaltic pump, 12 mL of effluent was collected
per sample tube and analyzed for pH, copper,
and potassium concentrations. The pH of theeffluent samples was determined immediately
after the collection of the samples. Copper andpotassium were determined using atomic adsorption (AA) and atomic emission using an
atomic absorption spectrophotometer, respectively. A breakthrough curve was established foreach column, and the retardation factor R,
the distribution coefficient Kd, and the longitudinal dispersivity D were calculated using the
HYDRUS-1D software package for simulating
one-dimensional movement of water, heat, andmultiple solutes in variably saturated media(Simunek et al., 1998). In this study, five column experiments (Table 3) were conducted:(1) the column was packed with Marvyn soil,
and the influent solution contained only copper and potassium sulfate; (2) the column was

TABLE 3Chemical composition of the eluent that was introduced into the medium for the five column experiments
Column no.
1
2
3
4
5

CuSO4

K2SO4

Oxalic acid

Citric acid

1.5710j2 M/L
1.5710j2 M/L
1.5710j2 M/L
1.5710j2 M/L
1.5710j2 M/L

10j2 M/L
10j2 M/L
10j2 M/L
10j2 M/L
10j2 M/LNA
10j3 M/L
NA
NA
NA

NA
NA
10j3 M/LNA
NA

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

VOL. 171 ~ NO. 1

COPPER MOBILITY IN SOIL AND SEWAGE SLUDGES

packed with Marvyn soil, and the influent
contained oxalic acid in addition to copper andpotassium sulfate; (3) the column was packed
with Marvyn soil, and the influent contained
citric acid in addition to copper and potassium
sulfate; (4) the bottom quarter of the column
was packed with a mixture of the Marvyn soil
and sewage sludge 1 (Village Creek waste water
plant in Birmingham, AL); and (5) the bottom
quarter of the column was packed with amixture of the Marvyn soil and sewage sludge
2 (Trussville waste water plant in Trussville,
AL). The influent solution in column experiments 4 and 5 contained only copper and potassium sulfate.
Sorption Isotherm
To determine how much copper can beadsorbed by the sewage sludges and by the
Marvyn soil, a series of batch experiments was
conducted. Triplicate 10-g samples were prepared of oven-dried (105 -C) sewage sludge 1,oven-dried sewage sludge 2, and oven-dried
Marvyn soil for each of 9 copper concentrations,
resulting in a total of 81 samples. Each sample wasplaced in a 125-mL Erlenmeyer flask, and copper
was added to each replicate set in the following
amounts: 0, 1, 2, 4, 8, 10, 20, 40, and 80 mg.
Deionized water was then added to bring thetotal volume in each flask to 100 mL. The flasks
were secured on a reciprocal mechanical shaker
and shaken overnight for equilibration purpose.
The contents of the flasks were filtrated throughWhatman no. 42 filter paper, and the copper

33

concentration of the filtrates was determined by
AA. Amounts of copper adsorbed on the soil oron the sewage sludge were calculated from thedifference between the initial copper concentrations and the equilibrium aqueous phase concentrations of copper. Because sewage sludges
adsorbed so much copper, 5 additional copper
concentrations were added only to the sewage
sludges, resulting in the following amounts ofcopper being added to triplicate 10-g samples ofoven-dried sewage sludges: 100, 200, 400, 800,
and 1000 mg. The same procedure was used todetermine the amounts of copper adsorbed.
RESULTS AND DISCUSSIONSThe pH values of the samples collectedduring each column experiment were immediately determined and are presented in Fig. 2.
Zero time for all column experiments is definedas the time at which the first drop of the effluent
appeared (1 pore volume of effluent is equivalent to 200 min of leaching). Although initial
pH values for all columns differed somewhat,
they were close to the pH of the Marvyn soil
pH (6.6). First, there was a slight increase in pH,
suggesting that some H+ ions were adsorbedby the column medium, followed by a steadydecrease. This might be the result of the lack ofequilibrium observed at the beginning of manycolumn experiments, particularly when themedium in the column was not saturated by abackground solution. At the end of each column
experiment (10 pore volumes of effluent), thepH values of the collected effluent samples were

Fig. 2. Changes in pH value of the effluent as time (leaching volume) progresses.

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

34

BAHAMINYAKAMWE, ET AL.
TABLE 4

Values of the distribution coefficient (Kd), the retardation
factor (R), the longitudinal dispersivity (D), and theregression coefficient (r2) for copper (Cu) andpotassium (K) as estimated by HYDRUS-1D
Column no.

Kd

R

D (cm)r2Cu
1 (100% Soil)
2 (100% Soil)
3 (100% Soil)
4 (75% Soil)(25% Mixture)5 (75% Soil)(25% Mixture)

1.26
1.26
1.41
1.26.
5.85
1.26.
5.46

5.26
5.24
5.74
5.26.
16.95
5.26.
15.85

3.04
2.81
1.17
3.04.
13.06
3.04.
30.00‘

0.980
0.991
0.990
NA
0.992
NA
0.992

0.13
0.17
0.16
0.13.
0.63
0.13.
0.56

1.42
1.56
1.53
1.42.
2.72
1.42.
2.52

0.83
2.07
1.15
0.83.
30.00‘
0.83.
30.00‘

0.977
0.949
0.974
NA
0.935
NA
0.927

K
1 (100% Soil)
2 (100% Soil)
3 (100% Soil)
4 (75% Soil)(25% Mixture)
5 (7% Soil)(25% Mixture).

These values were not optimized. They were fixed tovalues obtained by the optimization in column 1.
The mixture consisted of sewage sludge and the Mavyn soilin the ratio of 1:10.
‘
These values were constrained to the value of the length ofthe column.

very close to the pH value of the influent
solution (pH 4.7).
Potassium, which was used to maintain aconstant ionic strength, was hardly retarded by
the soil or sewage sludge, and the maximum(influent) potassium concentration was quickly
obtained (Table 4; Fig. 3). This was in part

SOIL SCIENCE

attributed to the potassium already present insoil and in part to the lower valence of K+
compared with Cu2+. This may have beendifferent if a Ca2+ or Al3+ solution had beenused to maintain a constant ionic strength.
According to Cavallaro and McBride (1978),Ca2+ greatly reduces the efficiency of heavy
metal adsorption, suggesting a stronger Ca2+
than K+ affinity for adsorption sites.
When the influent contained only copperand potassium sulfate (column 1), the breakthrough curve (Fig. 4) showed that copper
detection in the effluent occurred 400 min after
the start of the experiment (about 2 porevolumes of effluent). Maximum copper concentration was obtained 1600 min after the start ofthe experiment (about 8 pore volumes). Whenthe eluent contained oxalic acid (column 2) inaddition to copper and potassium sulfate, thebreakthrough curve (Fig. 4) resembled the one
obtained when copper and potassium sulfate
alone were present in the eluent solution.
Apparently, oxalic acid did not affect copper
movement in the soil. When the eluent contained citric acid (column 3) in addition tocopper and potassium sulfate, the breakthroughcurve (Fig. 4) showed that copper detection in
the effluent happened 600 min after the start ofthe experiment (about 3 pore volumes). Citricacid affected copper movement by increasing
the retardation factor (Table 4). However, themaximum copper concentration was obtained
1600 min after the start of the column experiment (about 8 pore volumes), which was thesame time observed for the maximum copper
concentration when copper was alone or mixed

Fig. 3. Breakthrough curves for K+ in columns 1 to 5.

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

VOL. 171 ~ NO. 1

COPPER MOBILITY IN SOIL AND SEWAGE SLUDGES

35

Fig. 4. Breakthrough curves for Cu2+ in columns 1 to 5.

with oxalic acid in the eluent solution. Bineyev
et al. (1982) found that copper adsorption bysoil or sewage sludge was 64% higher whencopper was used alone in solution than whencopper was added in a mixture of amino acids.
This was the case when copper was used in a
mixture with oxalic acid, but when copper waspresent in a mixture with citric acid, it was
shown that citric acid formed stronger complexes
with copper than oxalic acid or amino acids, andthe retardation factor was higher than the ones
obtained in the first two column experiments.
The use of sewage sludge 1 (column 4) showeda threefold increase in R over the previous

Fig. 5. Langmuir adsorption isotherm when Cu2+ is being adsorbed by the Marvyn soil.

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

36

BAHAMINYAKAMWE, ET AL.

3 column experiments (Table 4). Copper was
first detected in the effluent 500 min (about 2.5
pore volumes) after the start of the experiment,
the same time as when no sewage sludge wasused, but the maximum copper concentration
was not yet obtained 2000 min (about 10 porevolumes) after the start of the experiment (Fig. 4).
In case of sewage sludge 2 (column 5), detectionof copper in the effluent first happened 300 min
after the start of the experiment (Fig. 4), whichis 200 min earlier than with sewage sludge 1(column 4). However, the retardation factor R(Table 4) was almost the same as for sewage
sludge 1 (16.95 for sewage sludge 1 and 15.85
for sewage sludge 2). Like in case of sewage
sludge 1, the maximum copper concentration
was not obtained 2000 min after the start of theexperiment (about 10 pore volumes).
Not reaching the maximum copper concentration for both sewage sludges is an indication that sewage sludges adsorb a large quantityof copper and potentially other heavy metals.
Bergkvist and Jarvis (2004) found that soils
amended with sewage sludge have a very highadsorption capacity with regard to cadmium.
Liu and Wang (2004) studied in situ speciationof copper-humic substances in a contaminatedsoil during electrokinetic remediation and foundthat copper-humic substances were associatedwith 50% of the total copper contained in thesoil. To check how much copper could be
adsorbed by the sewage sludge, a Langmuir

SOIL SCIENCE

adsorption isotherm was determined for the soil
(Fig. 5) and the sewage sludges (Fig. 6). The
maximum adsorption of copper for the soil was
1250 mg/kg. In case of the sewage sludges, themaximum copper adsorption was 50,000 mg/kg,
which is 40 times higher than the soil maximum
adsorption of copper. Both sewage sludges
adsorbed the same amount of copper. This is
an indication that these sewage sludges have thesame amount of copper adsorption sites andcould be used to detoxify copper from minetailings because they adsorb so much copper.
Over time, however, the decomposition of sewage sludge may be followed by copper desorption. Keeping the pH of the soil around pH 6.5
by liming would lower copper availability toplants and minimize the risk of leaching. Addition of organic matter would maintain copper inan organic form that would be less available toplants or leaching.
CONCLUSION
In general, copper adsorption by soils isaffected by soil organic matter content. The
presence of low molecular weight organic acids
and sewage sludge in soils might prevent copper
adsorption by forming soluble copper complexes.
In this study, oxalic acid–copper complexes did
not affect the mobility of copper in a Marvyn
loamy sand. Citric acid–copper complexes, however, retarded the mobility of copper in the same

Fig. 6. Langmuir adsorption isotherm when Cu2+ is being adsorbed by the sewage sludges 1 and 2.

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

VOL. 171 ~ NO. 1

COPPER MOBILITY IN SOIL AND SEWAGE SLUDGES

soil. Adding sewage sludge to the soil greatly
slowed the mobility of copper in the column
medium. The maximum (influent) copper concentration was not yet obtained 2000 min (about
10 pore volumes of the influent) after the start ofthe experiment. The maximum copper adsorption was determined to be 1250 mg/kg and
50,000 mg/kg for the soil and sewage sludges,
respectively. With this amount being adsorbed,
sewage sludges could be used to detoxify copperin soils and mine tailings.
Heavy metals such as Cu2+ are known to beadsorbed by soil organic matter in large amounts(Lehmann and Harter, 1984). Sewage sludge
provides abundant organic matter, and its utilization as land applied amendment is limited
mostly by the heavy metals content (Polo et al.,1999). The fact that sewage sludge adsorbs large
amounts of heavy metals, as demonstrated bythis study, should be one of the factors in favorof more use of sewage sludge as a heavy metal
detoxifier. Unfortunately, because of the heavy
metal load already present, the adsorption ofheavy metals could be rendered ineffective by
the release with time of excess heavy metals.
The fear of sewage sludge releasing heavy metals
considered toxic to the environment has caused
the EPA to establish regulations for sewage
sludge use in the environment.

REFERENCES
Alloway, B. J. 1995. Soil processes and the behaviorof metals. In: Heavy Metals in Soils. 2nd ed. B. J.
Alloway (ed.). Blackie Academic and Professional,
London, U.K., pp. 11–37.
Baker, D. E., and J. P. Senft. 1995. Copper. In:
Heavy Metals in Soils. 2nd ed. B. J. Alloway (ed.).
Blackie Academic and Professional. London,
U.K., pp. 179–205.
Baker, D. E., and M. C. Amacher. 1982. Nickel,
copper, zinc and cadmium. In: Methods of Soil
Analysis. Part 2. 2nd ed. A. L. Page (ed.). Soil Sci.
Soc. Amer. Madison, WI, pp. 323–336.
Bergkvist, P., and N. Jarvis. 2004. Modeling organiccarbon dynamics and cadmium fate in long-term
sludge-amended soil. J. Environ. Qual. 33:181–191.
Bineyev, R. G., F. K. Khabibullin, A. I. Sharyapova,
and B. R. Grigoryan. 1982. Effect of chelating
agents on the absorption of copper by plants.
Translated from: Pochvovedeniye. 11:34–37.
Bloomfield, C., W. I. Kelso, and G. Pruden. 1976.
Reactions between heavy metals and humidified
organic matter. J. Soil Sci. 27:16–31.
Cavallaro, N., and M. B. McBride. 1978. Copperand cadmium adsorption characteristics of selected

37

acid and calcareous soils. Soil Sci. Soc. Am. J. 42:
550–556.
Forbes, E. A., A. M. Posner, and J. P. Quirk. 1976.
The specific adsorption of divalent Cd, Co, Cu,
Pb, and Zn on goethite. J. Soil Sci. 27:154–166.
Gee, G. W., and D. Or. 2002. Particle size analysis. In:
Methods of Soil Analysis: Physical Methods. Part
4. J. H. Dane and G. C. Topp (co-eds.). No. 5.
Soil Sci. Soc. Amer. Madison, WI, pp. 255–293.
Hodgson, J. F., W. L. Lindsay, and J. F. Trierweiler.
1966. Micronutrient cation complexes in soil
solution: II. Complexing of zinc and copper indisplaced solution from calcareous soils. Soil Sci.
Soc. Am. Proc. 30:723–726.
Kabata-Pendias, A., and H. Pendias. 1992. Trace Elements in Soils and Plants. 2nd ed. CRC Press,
Boca Raton, FL.
Lehmann, R. G., and R. Harter. 1984. Assessment ofcopper-soil bond strength by desorption kinetics.
Soil Sci. Soc. Am. J. 48:769–772.
Lindsay, W. L. (ed.). 1979. Chemical Aquilibria inSoils. Wiley-Interscience, New York.
Liu, S. H., and H. P. Wang. 2004. In situ speciation
studies of copper-humic substances in a contaminated soil during electrokinetic remediation.
J. Environ. Qual. 33:1280–1287.
McBride, M. B. 1981. Forms and distribution ofcopper in solid and solution phases of soil. In:
Copper in Soils and Plants. J. F. Loneragan, A. D.
Robson, and R. D. Graham (eds.). Academic
Press, New York, pp. 25–45.
McBride, M. B., and J. J. Blasiak. 1979. Zinc andcopper solubility as a function of pH in an acidsoil. Soil Sci. Soc. Am. J. 43:866–870.
McLaren R. G., and D. V. Crawford. 1973. Studies
on soil copper. II. The specific adsorption ofcopper by soils. J. Soil Sci. 24:443–452.
McLaren, R. G., R. S. Swift, and J. G. Williams.
1981. The adsorption of copper by soil materials at
low equilibrium solution concentrations. J. Soil
Sci. 32:247–256.
McLean, E. O. 1982. Soil pH and lime requirement.
In: Methods of Soil Analysis. Part 2. 2nd ed. A. L.
Page (ed.). Soil Sci. Soc. Amer. Madison, WI, pp.
199–224.
Polo, M. J., R. Ordonez, and J. V. Giraldez. 1999.
Copper and zinc adsorption by sewage sludgetreated soil in Southern Spain. Commun. Soil Sci.
Plant Anal. 30:1063–1079.
Ponizovsky, A. A., T. A. Studenikina, and E. V.
Mironenko. 1999. Copper retention as affected bycomplex formation with tartaric and fulvic acids. In:
Fate and Transport of Heavy Metals in the Vadose
Zone. H. M. Selim and I. K. Iskandar (eds.).
Lewis Publishers, Boca Raton, FL, pp. 107–125.
Sauvé, S., W. Hendershot, and H. E. Allen. 2000.
Solid-solution partitioning of metals in contaminated soils: dependence on pH, total metal burden,
and organic matter. Environ. Sci. Technol. 34:
1125–1131.

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

38

BAHAMINYAKAMWE, ET AL.

Sauvé, S., S. Manna, M. C. Turmel, A. G. Roy, and
F. Courchesne. 2003. Solid-solution partitioning of Cd, Cu, Ni, Pb, and Zn in the organic
horizons of a forest soil. Environ. Sci. Technol.
37:5191–5196.
Sims, G. K., T. R. Ellsworth, and R. L. Mulvaney.
1995. Microscale determination of inorganic
nitrogen in water and soil extracts. Comm. Soil
Sci. Plant Anal. 26:303–316.
Simunek, J., M. Sejna, and M. Th. Van Genuchten.
1998. The HYDRUS-1D software package forsimulating the one-dimension movement of water,
heat, and multiple solutes in variably-saturated
media. Version 2.0, IGWMC-TPS-70. International Ground Water Modeling Center, Colorado
School of Mines, Golden, CO.
Stevenson, F. J., and A. Fitch. 1981. Reactions with

SOIL SCIENCE

organic matter. In: Copper in Soils and Plants. J. F.
Loneragan, A. D. Robson, and R. D. Graham(eds.). Academic Press, New York, pp. 69–65.
Temminghoff, E. J. M., M. P. J. C. Marinussen, andS. E. A. T. M. Van Der Zee. 1999. Copper
mobility and bioavailability in relation withchemical speciation in sandy soil. In: Fate andTransport of Heavy Metals in the Vadose Zone.
H. M. Selim and I. K. Iskandar (eds.). Lewis
Publishers, Boca Raton, FL, pp. 127–146.
Tisdale, S. L., W. L. Nelson, J. D. Beaton, and J. L.
Havlin. 1993. Soil Fertility and Fertilizers. 5th ed.
McMillan Publishing Co, New York.
Thomas, G. W. 1982. Exchangeable cations. p. 159–
165. In: Methods of Soil Analysis. Part 2. 2nd ed.
A. L. Page (ed.). Soil Sci. Soc. Amer. Madison,
WI.

Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.