Dynamics of Cd, Cu and Pb added to soil through different kinds of sewage sludge

Dynamics of Cd, Cu and Pb added to soil through different kinds
of sewage sludge
S.I. Torri *, R.S. Lavado
Ca´tedra de Fertilidad, Facultad de Agronomıá, UBA, Avda San Martıń 4453, Buenos Aires (C1417 DSE), Argentina
Accepted 12 January 2007
Available online 8 May 2007
Abstract
A greenhouse experiment was set up to study the distribution of Cd, Cu and Pb in three typical soils of the Pampas Region amended
with sewage sludge. A sequential extraction procedure was used to obtain four operationally defined geochemical species: exchangeable,
bound to organic matter, bound to carbonates, and residual. Two kinds of sewage sludge were used: pure sewage sludge and sewage
sludge containing 30% DM of its own incinerated ash, at rates equivalent to a field application of 150 t DM haÀ1
. Pots were maintained
at 80% of field capacity through daily irrigation with distilled water. Soil samples were obtained on days 1, 60, 270 and 360, and then air-
dried and passed through a 2 mm sieve for analysis. Results showed that sludge application increased the less available forms of Cd, Cu
and Pb. The inorganic forms became the most prevalent forms for Cu and Pb, whereas Cd was only found in the residual fraction. The
concentrations of OM-Cu and INOR-Cu in the amended soil samples were closely correlated with soil pH, whereas the chemical behav-
ior of Cd and Pb did not depend on soil physico-chemical characteristics.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
About 1,800,000 metric tons of sewage sludge are pro-
duced annually in the City of Buenos Aires, Argentina.
The accumulation of this biowaste poses a growing envi-
ronmental problem. The disposal of sludge products on
agricultural land or by incineration are feasible options
currently practiced in many parts of the world, but neither
of these strategies are used in Argentina. Sludge products
are aerobically stabilized and presently discarded in land-
farming, and to a minor extent as a soil amendment on
lawns or landfilling.
Agricultural application of sewage sludge (SS) generally
is considered the best option of management because it
offers the possibility of recycling plant nutrients, provides
organic material to the soil, and improves the soil’s aggre-
gate stability, porosity and water infiltration rate (Marinari
et al., 2000; Chambers et al., 2002; Garcıá-Orenes et al.,
2005). One of the main concerns regarding soil application
of SS is the presence of potentially toxic elements (PTE),
which can accumulate in soils when applied repeatedly or
at high rates (Bhogal et al., 2003).
Incineration of sewage sludge usually is considered an
attractive method of energy production and volume reduc-
tion. Incineration eliminates some environmental and
health problems by destroying pathogens and toxic organic
chemicals that may be present in the sludge. Sewage sludge
ash (AS) is primarily an inorganic material, which predom-
inantly contains SiO2, CaO, Al2O3 and Fe2O3 as major
oxide constituents (Pan and Tseng, 2001). Application of
AS to agricultural soils presents an opportunity for the
recovery of nutrients considered essential for plant growth
(Mellbye et al., 1982; Jakobsen and Willett, 1986). The use
of AS in agriculture has been reported; it can be used as a
liming agent on acid soils and may also bring agronomic
benefits, although there are some concerns about its high
PTE contents (Zhang et al., 2002a,b). During incineration,
non-volatile hazardous constituents like Pb, Cd, Zn and Cu
0956-053X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.wasman.2007.01.020
*
Corresponding author. Tel.: +54 01145248228; fax: +54 01145248076.
E-mail address: torri@agro.uba.ar (S.I. Torri).
www.elsevier.com/locate/wasman
Available online at www.sciencedirect.com
Waste Management 28 (2008) 821–832

commonly found in sludge are concentrated in the ash, and
potentially limit the extent of its land application. It was
reported that AS increased the soil solution of Cd, Cu
and Zn (Bierman and Rosen, 1994; Bierman et al., 1995)
or produced the leaching of high amounts of toxic elements
such as As, Cd, Cr, Pb and Se (Saikia et al., 2006). There-
fore, the availability of PTE has become a critical problem
for the disposal and utilization of AS.
Byproducts of coal combustion and residuals from
wastewater treatment sometimes are combined and used
as amendments to agricultural soils. Several studies con-
ducted using mixtures of fly ash and sewage sludge indicate
that these materials could reduce the phytoavailability of
PTE when applied to agricultural land (Sajwan et al.,
2003; Su and Wong, 2004). Although the bulk chemical
composition of the byproducts of combustion residues is
different, the contents of the predominant components usu-
ally differ only in a limited range (Theis and Gardner, 1990).
Thus, combined use of AS and SS for land application could
prove to be a beneficial means of management. Because of
the contrasting chemical properties of AS and SS, land
application of both products as a mixture can improve soil
quality and crop production. As an organic amendment, SS
improves the physical, chemical, and microbiological prop-
erties of soils, whereas its stable organic matrix may act as
an adsorptive medium for the PTE added to soils through
AS (Corey et al., 1987; Torri et al., 2003). Conversely, SS
tends to increase soil acidity as a result of proton release
from organic matter decomposition and mineralization.
The calcium oxide present in AS would increase the pH,
reducing the availability of PTE (Wong, 1995; Jiang et al.,
1999). The addition of silt-size particles present in AS pro-
motes better aeration, percolation and water retention
capacity. AS can also supply essential elements to crops
growing in nutrient-deficient soils, since nutrients present
in organic wastes such as SS must be transformed slowly
from organic to inorganic forms (mineralized), and are
not available to crops during the growing season. Combined
use of AS and SS is not yet used in Argentina, but it is
thought it would fit with the local situation (high-popula-
tion and large cropping area) (Torri, 2001).
Although the evaluation of total PTE concentration
may be useful as a global index of contamination, it pro-
vides little indication of specific bioavailability of PTE or
mobility in sludge amended soils (McBride, 1995). It is
now widely recognized that the toxicity and mobility of
these pollutants strongly depend on their specific chemical
forms and on their binding state (precipitated with primary
or secondary minerals, complexed by organic ligands, and
so on). Soil physical–chemical properties, especially pH,
CEC, organic matter and clay content, also are likely to
assume great importance in determining PTE behavior
(Smith, 1994; Chaudri et al., 2000; McBride et al., 2000).
Sequential extraction is a useful technique for determining
the nature of the association of PTE with soil components.
Such information is potentially valuable for predicting bio-
availability, metal leaching rates and transformations
between physico-chemical forms in agricultural and pol-
luted soils (Miller et al., 1986; Tsadilas et al., 1995). Knowl-
edge of PTE speciation in soil amended with a mixture of
AS and SS is, therefore, essential for the understanding
of the bioavailability and mobility of PTE in soils.
The objective of this research was to determine the
chemical availability of Cd, Cu and Pb in three typical soils
of the Pampas Region amended with sewage sludge or a
mixture of sewage sludge and its own incinerated ash over
a period of 1 yr, and to assess the possible influence of soil
physical–chemical properties on the distribution of Cd, Cu
and Pb among soil fractions.
2. Materials and methods
2.1. Soils – description and characterization
Soil samples of three representative Mollisols (US Soil
Taxonomy, USDA, 1999) of the Pampas Region, Argen-
tina were collected. The soils are classified as Typic Haplu-
doll, Typic Natraquoll and Typic Argiudoll. Sampling sites
were located near C. Casares, Pila and S.A. de Areco
towns. The samples were collected from pristine sites, not
previously fertilized or contaminated. Ten soil samples
(0–15 cm depth) were taken at each site and stored in poly-
ethylene bags. The samples were homogenized, air-dried,
and ground to pass through a 2-mm plastic sieve. The main
physico-chemical characteristics of the soils are presented
in Table 1. Although the soils had different particle size dis-
tributions, the clay-fraction had the same origin and miner-
alogical composition, because they were developed from
deep Aeolian sediments of the Pleistocene (Soriano, 1991).
2.2. Sewage sludge
Sewage sludge from the SW outskirts of the City of Bue-
nos Aires was provided by the local water operator, Aguas
Argentinas S.A. The aerobically stabilized sludge used in
this experiment was previously dried in holding ponds in
the sewage sludge treatment plant. The content of PTE in
the SS was below the maximum permissible concentration
of PTE by Argentinean regulations, whose values are sim-
ilar to US Environmental Protection Agency’s (US EPA)
limits. The sludge (SS) was oven-dried at 60 °C, ground
and sieved (<2 mm) and then split into two portions. One
portion was incinerated at 500 °C, and the ash obtained
(AS) was mixed with a portion of the previously sieved
sewage sludge, resulting in a new mixed waste containing
30% DM as ash (SSA). The moisture content was deter-
mined by drying subsamples at 105 °C to a constant
weight. Analytical data (dry mass basis) for SS and SSA
are presented in Table 2.
2.3. Greenhouse experiment
Both amendments (SS and SSA) were homogeneously
mixed with 100 g of each of the three soils at proportions
822 S.I. Torri, R.S. Lavado / Waste Management 28 (2008) 821–832

equivalent to a field application rate of 150 t DM haÀ1
.
Sludge loading rates used in this experiment vastly
exceeded normal application rates. Heavy loadings were
used to study short-term equilibrium in soils with high
sludge adsorption capacity in order to assess the potential
impact of short-term sewage sludge application. A control
with no sludge was also included for each soil. Amended
and control soils were placed in 200-cm3
plastic pots with
no lids. Each pot was 7 cm (top) and 5 cm (bottom) in
diameter and 8 cm in height, with drain holes in the bottom
to ensure aerated conditions. All treatments were replicated
four times. The pots were arranged in completely random-
ized blocks outdoors, at ambient temperature and sheltered
from direct sunlight and rainfall. Mean annual minimum
and maximum temperatures were 10 °C and 25 °C, respec-
tively. The experiment consisted of a factorial design of
3 · 3 with 144 pots (3 soils · 3 treatments · 4 replicates · 4
sampling dates). Soil moisture was maintained at 80% of
water holding capacity (WHC) by adding distilled water
and weighing on a daily basis. Four pots for each treatment
were sampled on days 1, 60, 270 and 360, air-dried and
ground to pass through a 2-mm plastic sieve for analysis.
2.4. Analytical methods
Soil pH was measured with a pH-meter at a 1:2.5 (w/v)
ratio of soil and water on each sampling date. Particle dis-
tribution was analyzed following a micropipette method
(Miller and Miller, 1987). Organic carbon content was ana-
lyzed by the wet oxidation method (Amato, 1983). Total N
was determined by the Kjeldahl method as described by
Bremmer and Mulvaney (1982); total P, Ca, Mg and K
were obtained as described by Blakemore et al. (1987). Cat-
ion exchange capacity (CEC) was determined using a
sodium acetate method (Chapman, 1965). The total Zn,
Cu, Pb content in soils, SS and SSA was determined by
digestion in HNO3, HCl, HF (Shuman, 1985) and the con-
centration of Zn, Cu, Pb in the digested solution was mea-
sured by atomic adsorption spectroscopy (AAS).
The procedure of McGrath and Cegarra (1992) was used
for soil fractionation of PTE into water-soluble and
exchangeable fraction (EXCH); organic matter bound frac-
tion (OM); inorganic precipitate fraction (INOR) and
residual fraction (RES). Briefly, 3 g of each soil sample
were weighed into 50-ml centrifuge tubes, and 30 ml of
each of the following reagents were sequentially added
and shaken for the time specified for each extractant in
the order listed: 0.1 M CaCl2 for 16 h (EXCH); 0.5 M
NaOH for 16 h (OM); 0.05 M Na2 EDTA for 1 h (INOR).
To minimize the risk of contamination and losses through
handling, successive extractions were performed in the
same centrifuge tube. At the end of each extraction period,
the soil suspension was centrifuged at 3600 rpm for 45 min
and filtered through Whatman no. 42 filter paper. The tube
with soil was weighed once after the addition of the extract-
ant and again after the solution was filtered, to estimate the
quantity of entrained solution. The quantity of each subse-
quent extractant was adjusted to account for the entrained
solution from the previous extraction. Because the NaOH
reagent also extracted organic matter, the supernatant
was digested in aqua regia previous to its determination.
PTE were determined in each filtrate by inductively couple
plasma emission spectrometry (ICP). Blanks were used for
background concentrations. All analyses were checked
against standard reference materials from NIST. Standards
for both trace metals were analyzed in the same matrix as
the extractant. PTE concentrations in the whole soil sample
and in the residual fractions were determined by digestion
with HNO3, HCl, HF (Shuman, 1985). The recovery of the
sequential extraction procedure (sum of all fractions/total
EPT · 100%) has been found to be in the range of 95–
105%. Crystalline phases present in SS, AS and in the soils
were identified by X-ray diffraction (XRD) using a Philips
PW 1510 diffractometer with Cu radiation, and by SEM–
EDS.
2.5. Statistical analysis
Data were analyzed using one-way analysis of variance
(ANOVA). In all cases, normality assumption was tested
Table 1
Selected properties of the A horizon (0–15 cm)
Typic
Hapludoll
Typic
Natraquoll
Typic
Argiudoll
Clay (%) 19.2 27.6 32.7
Silt (%) 23.2 43.0 57.5
Sand (%) 57.6 29.4 9.8
pH 5.12 6.21 5.44
Organic carbon (g kgÀ1
) 28.6 35.31 23.9
Electrical conductivity
(dS mÀ1
)
0.61 1.18 0.90
Cation exchange capacity
(cmol(c) kgÀ1
)
22.3 22.3 15.3
Exchangeable cations
Ca2+
(cmol(c) kgÀ1
) 5.2 9.1 11.0
Mg2+
(cmol(c) kgÀ1
) 2.0 5.4 1.8
Na+
(cmol(c) kgÀ1
) 0.3 3.1 0.1
K+
(cmol(c) kgÀ1
) 2.8 1.6 2.2
Table 2
Selected properties of sewage sludge (SS) and 70:30 DMW mixture of
sewage sludge and sewage sludge ash (SSA)
SS SSA
pH 5.82 6.17
Moisture content (%) 5 4.5
Total organic carbon (mg gÀ1
) 251 176
Total N (mg gÀ1
) 19.3 22.5
Total P (mg gÀ1
) 0.052 0.086
Electrical conductivity (dS mÀ1
) 0.90 0.89
Cation exchange capacity (cmol(c) kgÀ1
) 11.95 nd
Ca (mg gÀ1
) 22.5 nd
Mg (mg gÀ1
) 5.6 nd
K (mg gÀ1
) 10.7 nd
Total Cd (mg kgÀ1
) 10.08 13.08
Total Cu (mg kgÀ1
) 750.8 894.7
Total Pb (mg kgÀ1
) 334.2 365.9
nd = not determined.
S.I. Torri, R.S. Lavado / Waste Management 28 (2008) 821–832 823

by the Shapiro–Wilks test, and homogeneity of variance
was tested using the Bartlett’s test. We used Logarithmic
transformations (logx) when data did not meet the
assumptions of normality and homoscedasticity. Because
a common transformation scale was applied, the compara-
tive values among treatments were not altered and compar-
isons among them remain valid. We performed multiple
comparisons by Tukey’s honestly significant difference
(HSD) test if differences among means of treatments were
statistically significant. For simplicity of interpretation,
untransformed data is presented in figures and tables, with
the corresponding standard deviation (±S.D.). Statistical
analyses were conducted using Statistix Program version
7.0. Values of p < 0.05 were considered to be significant
in all analyses.
Correlation (Pearson correlation) was explored between
the concentration of PTE in soil fractions and selected vari-
ables: pH, organic matter (OM) and clay content.
3. Results and discussion
3.1. Distribution of Cd, Cu and Pb in pristine soils
The mineralogy of three pristine soils is dominated by
nearly unweathered volcanic material such as plagioclases,
glasses and lithic fragments. Minor components include
quartz and orthoclase, as can be seen in the X-ray analysis
(Fig. 1). In the clay-fraction, the predominant mineral is
illite, some montmorillonite and a lesser proportion of int-
erstratified illite/montmorillonite make up the reminder
(Soriano, 1991).
Total concentrations of Cd, Cu and Pb in the three
pristine soils were according to non-contaminated soils
(Lavado et al., 2004). Total Cd concentration was below
analytical detection limits in the three soils (< 0.1
mg Cd kgÀ1
).
Total endogenous Cu and Pb were two times higher in the
Hapludoll than in the Natraquoll, with intermediate values
in the Argiudoll. The distribution of Cu and Pb among soil
fractions depended on the soil considered (Table 3), and did
not change throughout the study period. In the Hapludoll,
Cu was predominantly present as RES-Cu (70%), with
much less OM-Cu and INOR-Cu (17.49% and 12.39%,
respectively). In the Natraquoll it was uniformly distributed
among OM-Cu, INOR-Cu and RES-Cu (31.5%, 35%, 33%,
respectively), whereas in the Argiudoll, Cu was mainly
found as OM-Cu and INOR-Cu (43.8% and 41%, respec-
tively), with a smaller proportion of RES-Cu (15%).
EXCH-Cu was below the analytical detection limit in the
three pristine soils (< 0.5 mg Cu kgÀ1
). Pb was present as
INOR-Pb and RES-Pb, with EXCH-Pb and OM-Pb below
the analytical detection limit in the three soils (<0.5 mg
Pb kgÀ1
). INOR-Pb represented the largest fraction in the
Natraquoll and Argiudoll (88% and 63%, respectively), in
agreement with the results reported by Walter and Cuevas
(1999). In the Hapludoll, 67% of Pb was associated with
the RES fraction.
3.2. Cd, Cu and Pb in sewage sludge
The main crystalline component of SS was quartz (SiO2,
26.90° 2h), with a trace of plagioclase [(Na,Ca)(Si,Al)4O8]
(Fig. 2a). Incineration of SS had little influence on the over-
all mineralogy of the sludge components. Comparison of
the X-ray diffraction (XRD) patterns showed that the main
effect of incineration was the formation of hematite (a-
Fe2O3) and calcite (ACO3) (Fig. 2b). There also appears
to be a slight increase in the amount of plagioclase relative
to the amount of hematite and quartz.
The contents of Cd, Cu and Pb in SS and SSA did not
exceed ceiling concentrations for land application recom-
mended by Argentine regulation (S.A.D.S., 2001, Res.
97/01) and the USEPA (1993). Cd and Cu concentrations
were within the numerical standards for biosolids not sub-
ject to cumulative pollutant loading rates (CPLRs) permit-
ted by the USEPA regulations (Table 4). Because of high
Pb concentration, this sludge would not be allowed for
use in agriculture without maintaining records of cumula-
tive applications, 300 kg/ha for Pb. Total Pb loading used
in this study for SS and SSA complies with the Argentine
and US regulations on cumulative loadings for soils treated
with sludge.
Sequential chemical fractionation of the elements stud-
ied in the SS and SSA samples is shown in Table 5. Cd
was only recovered from the residual fraction. These results
differ from other reports, where Cd in sludge was princi-
pally distributed in the oxidizable and residual fractions
or between the easily assimilable, exchangeable and reduc-
ible fraction (Fuentes et al., 2004; Wang et al., 2005). Incin-
eration reduced the availability of Cu and Pb, increasing
the percentage of residual fractions, which agrees with
the results found by Obrador et al. (2001). Cu and Pb were
predominantly in the residual fraction of both SS and AS,
which indicates that the elements were probably occluded
in primary minerals. Only 17–20% of Cu was recovered
as OM-Cu, differing from other studies (Zufiaurre et al.,
1998; Scancar et al., 2002; Fuentes et al., 2004). The high
proportion of Pb recovered from the inorganic and residual
fraction should also be mentioned. Different results have
been reported in other studies (Scancar et al., 2002; Wang
et al., 2005), where Pb was distributed between the organic
and the residual fraction. These results show that the mode
by which the sludge is processed may affect individual
metal association with soil components, and lead to consid-
erable variation of availability. The differences among our
results and results from other authors could also be due to
the different origin of metals in the sludge (Smith, 1996).
3.3. Cd, Cu and Pb in sewage amended soils
The application of the SS and SSA amendments to the
three soils caused a significant build up of total Cd, Cu
and Pb at each sampling date. The speciation of Cd, Cu
and Pb at day 1 in the three amended soils was governed
by the initial chemical state in which these elements occur

in the sludge (Zufiaurre et al., 1998). Comparing treatments
at day 1, RES-Cd, RES-Cu and RES-Pb were significantly
higher in the SSA treatment than for SS treatment in the
three soils. In contrast to the unamended soils, SS and
SSA amended soils showed significant (p < 0.05) changes
over the incubation period.
3.4. Cadmium
Cd was only extracted in the residual fraction from the SS
or SSA amended soils for all of the samples, which is consid-
ered mainly to be highly crystalline Fe-oxides and silicate
minerals. EXCH-Cd, OM-Cd and INOR-Cd remained
below analytical detection limits in the three amended soils
in all sampling dates. Some authors have mentioned that
exchangeable forms of Cd increased significantly under
sludge application (Berti and Jacobs, 1996; Vaca-Paulıń
et al., 2006). Others have reported that the greater percent-
age of Cd was in the inorganic fraction (Walter and Cuevas,
angle 2θ
Typic Natraquoll
0
1000
2000
3000
4000
Typic Hapludoll
0
1000
2000
3000
4000
Typic Argiudoll
0
1000
2000
3000
4000
0 10 20 30 40 50 60
Q = quartz (SiO2)
P = plagioclase (Na,Ca)(Si,Al)4O8)]
P
Q
Q
Q
Q
Q
Q
Q
PP
P Q Q
Q
Q
QQQ
Q
P
QQ
P P P
QP QQQQ
Q
Q P
PP
P
Fig. 1. X-ray diffraction (XRD) patterns of the pristine soils: Typic Hapludoll, Typic Natraquoll and Typic Argiudoll.
Table 3
Total and soil distribution of endogenous Cu and Pb in the three pristine
soils among water-soluble and exchangeable fraction (EXCH), organic
matter bound fraction (OM), inorganic precipitate fraction (INOR) and
residual fraction (RES)
Typic Hapludoll
(mg kgÀ1
)
Typic
Natraquoll
(mg kgÀ1
)
Typic Argiudoll
(mg kgÀ1
)
EXCH-Cu ND ND ND
OM-Cu 3.85 ± 0.30 b 3.46 ± 0.15 b 7.01 ± 0.03 a
INOR-Cu 2.73 ± 0.10 b 3.86 ± 0.31 b 6.56 ± 0.04 a
RES-Cu 15.35 ± 0.30 a 3.60 ± 0.46 b 2.35 ± 0.07 b
Total Cu 22.00 ± 0.55 a 11.00 ± 0.12 c 16.00 ± 0.21 b
EXCH-Pb ND ND ND
OM-Pb ND ND ND
INOR-Pb 5.83 ± 0.09 b 7.93 ± 0.26 a 8.26 ± 0.04 a
RES-Pb 12.17 ± 0.71 a 1.16 ± 0.24 c 5.99 ± 0.29 b
Total Pb 18.00 ± 0.36 a 9.00 ± 0.23 c 13.00 ± 0.15 b
Different letters in the same row are significantly different at the 0.05
probability level. (mean ± SD, n = 4).
ND = not detectable (below analytical detection limit).

1999). Lena and Gade (1997) concluded that Cd was present
in all soil fractions when total Cd concentration was above
50 mg kgÀ1
. The results observed in this study suggest that
Cd was strongly adsorbed by reactive sorptive solid and
inorganic substrates or was incorporated in neoformed
clay-like minerals, reflecting the low reactivity and availabil-
ity of sludge-born Cd in soils amended with sewage sludge
from Buenos Aires outskirts.
3.5. Copper
On day 1, Cu was mainly extracted as RES-Cu (36.7–
65%) from either SS or SSA amended soils. This indicates
tightly bonded forms – presumably corresponding to Cu
held to minerals lattices. This behavior has also been
reported by others (Miller et al., 1986; Vaca-Paulıń et al.,
2006) who concluded that more than 75% of total Cu
was associated with lattices of primary minerals, Fe–Mn
oxides, and sulphides. A lower percentage of Cu was found
in this study to be associated with the organic (20.7–34.7%)
and inorganic (12.9–27.6%) fractions, whereas EXCH-Cu
was below the analytical detection limit (Fig. 3a), suggest-
ing extremely low initial levels of Cu availability.
With the passage of time, an increase in OM-Cu and
INOR-Cu fractions, along with a decrease in the RES-
a
0
1000
2000
3000
4000
0 10 20 30 40 50 60
counts
b
0
1000
2000
3000
4000
0 10 20 30 40 50 60
angle 2θ
counts
Q QQ
Q
Q
Q
QQQ
Q
Q
H
H
P P
PP
C
Q = quartz (SiO2)
P = plagioclase (Na,Ca)(Si,Al)4O8)]
H = hematite (α-Fe2O3)
C = calcite (ACO3)
Q
Fig. 2. X-ray diffraction (XRD) patterns of (a) sewage sludge (SS) and (b) 70:30 DMW mixture of sewage sludge and sewage sludge ash (AS).
Table 4
Argentine and USEPA acceptable standards of Cd, Cu and Pb in sludge
applied to soils (USEPA, 1993)
Cd Cu Pb
(mg kgÀ1
)
SS 10.08 750.8 334.2
SSA 13.08 894.7 365.9
Argentina 85 4300 840
USEPA – PC Biosolida
39 1500 300
USEPA – MAMCb
85 4300 840
kg haÀ1
CPLRsc
39 1500 300
a
PC = pollutant concentration biosolid.
b
MAMC = maximum allowable metal concentrations.
c
CPLRs = cumulative pollutant loading rates.
Table 5
Distribution of Cd, Cu and Pb in sewage sludge (SS) and sewage sludge
plus 30% DM ash (SSA), among water-soluble and exchangeable fraction
(EXCH), organic matter bound fraction (OM), inorganic precipitate
fraction (INOR) and residual fraction (RES) (mean ± SD, n = 4)
SS (mg kgÀ1
) AS (mg kgÀ1
)
Cd RES-Cd 10.80 ± 1.75 13.08 ± 3.74
Cu EXCH-Cu 8.45 ± 0.49 9.58 ± 1.05
OM-Cu 157.7 ± 9.8 159.10 ±4.7
INOR-Cu 108.9 ± 6.1 94.00± 7.9
RES-Cu 475.8 ± 5.4 632.0 ± 6.6
Pb EXCH-Pb ND ND
OM-Pb 31.2 ± 4.4 14.2 ± 0.4
INOR-Pb 157.9 ± 6.5 127.5 ± 8.9
RES-Pb 145.0 ± 4.5 224.2 ± 8.0
ND = not detectable (below analytical detection limit).

Cu, was observed in SS and SSA amended soils (Fig. 3).
These results are similar to findings reported by Berti and
Jacobs (1996). Other research has indicated that most of
the Cu was associated with organic forms (Su and Wong,
2004) or organic and residual forms (Nyamangara, 1998).
No significant differences in OM-Cu between SS and SSA
0%
50%
100%
% EXCH-Cu
% OM-Cu
% INOR-Cu
% RES-Cu
C SS SSA C SS SSA C SS SSA
Typic Hapludoll Typic Natraquoll Typic Argiudoll
0%
50%
100%
% EXCH-Cu
% OM-Cu
% INOR-Cu
% RES-Cu
0%
50%
100%
% EXCH-Cu
% OM-Cu
% INOR-Cu
% RES-Cu
0%
50%
100%
% EXCH-Cu
% OM-Cu
% INOR-Cu
% RES-Cu
day 1
day 360
day 60
day 270
Fig. 3. Distribution of Cu as a percentage of the average total amount in the water-soluble and exchangeable fraction (EXCH); organic matter bound
fraction (OM); inorganic precipitate fraction (INOR) and residual fraction (RES). Soils: Typic Hapludoll, Argiudoll and Natraquoll. C = control,
SS = sewage sludge amended soils, SSA = soils amended with the 70:30 DMW mixture of sewage sludge and sewage sludge ash.

treatments were observed for the Hapludoll and Argiudoll,
indicating that Cu incorporated to soils through sewage
ash did not adsorb onto sludge organic matter. This was
also observed for the Natraquoll, except for day 60, where
the OM-Cu fraction was significantly higher in the SSA
compared to the SS treatment.
On day 360, the magnitude of the increase in the OM-Cu
fraction in the amended soils depended on the soil’s phys-
ico-chemical characteristics, and followed the sequence:
Hapludoll >Argiudoll > Natraquoll, with no significant
differences between SS and SSA treatments. Cu is well
known to be predominantly associated with soil organic
matter (SOM) because of the high stability constants of
its organic complexes (Irving and Williams, 1953). How-
ever, the proportion of OM-Cu did not correlate with the
organic carbon content of the amended soils: SOM was
higher in the Natraquoll (38.46 mg C gÀ1
soil), compared
to the Hapludoll (31.3–33.9 mg C gÀ1
soil) or the Argiudoll
(25.53–28.22 mg C gÀ1
soil) (Torri and Lavado, 2002). In
this study, the soil factor most closely associated with the
distribution of OM-Cu in the three soils was soil pH
(Fig. 4). OM-Cu was higher in the low pH Hapludoll
(23.8–26.4 mg Cu kgÀ1
) compared to the other soils
(21.2–22.9 mg OM-Cu kgÀ1
in the Argiudoll and 16.1–
18.3 mg OM-Cu kgÀ1
in the Natraquoll). There was a neg-
ative correlation (r2
= 0.63) between OM-Cu fraction and
soil pH at the end of the experiment, indicating that OM-
Cu increased as soil pH decreased.
On day 360, the increase in INOR-Cu was significantly
higher in the Natraquoll (14.3–271.2 mg kgÀ1
) compared
to the other soils (1.4–105.5 mg kgÀ1
in the Argiudoll and
32.3–175.9 mg kgÀ1
in the Hapludoll). A positive correla-
tion (r2
= 0.80) was established between INOR-Cu and soil
pH on this date (Fig. 5).
A small percentage of EXCH-Cu was found on day
360 in the amended soils (0.95–2.21%), suggesting extre-
mely low levels of Cu availability. It may be expected that
Cu would show a great increase in the labile fraction over
time due to the appreciable amount of organic carbon
mineralization over the incubation period (Torri et al.,
2003). Several studies on the relationship between PTE
and dissolved organic matter (DOM) show that organic
molecules are, in many instances, responsible for the
availability of PTE in sludge amended soils. Hsu and
Lo (2000) observed an increase in Cu availability with
increasing pH and a concurrent increase in DOM. They
attributed these results to the irreversible dissolution of
organic matter with organically bound Cu at high pH
during natural weathering of the sludge in the soil. How-
ever, in this study EXCH-Cu was below analytical detec-
tion limits in the period of intense mineralization of
sewage sludge organic matter. Martıńez and Motto
(2000) studied the relationship between PTE and pH,
and found an approximate threshold pH value at which
PTE solubility increased in amended soils. This pH value
for Cu was 5.5 in non-calcareous soils, concluding that
lower pH values may enhance Cu biological availability.
In this study, soil pH of SS and SSA amended soils ran-
ged at day 360 from pH = 5.04–6.30. Although the lowest
pH value was below this threshold, EXCH-Cu was below
analytical detection limits.
Our results indicate that Cu previously bound to the
mineralized organic fraction of SS or SSA was able to be
retained by other sludge components instead of being
released to water-soluble or exchangeable fractions. The
kind of retention of Cu depended on soil pH. Cu had a
stronger affiliation with the resistant, non-readily decom-
posable organic materials of SS or SSA at lower pH (Torri
et al., 2003). As Cu desorption reactions have a slow kinet-
ics, there was a low proportion of desorbed Cu originating
in the sludge (Arias et al., 2005). Previous studies have also
shown that when soils were arranged in the order of
increasing soil pH, the proportion of OM-Cu decreased,
while INOR-Cu increased (Zhu and Alva, 1993; Alva
et al., 2000, 2005). The results obtained in this study indi-
cate that the proportion of OM-Cu / INOR-Cu is governed
by soil pH. When soil pH is low, the association of Cu with
the organic fraction predominates. As soil pH increases,
there is a shift of Cu towards inorganic species until a
threshold pH value at which Cu precipitation is the main
reaction.
y = -6.4268x + 57.948
R2
= 0.6294
0
10
20
30
40
4.50 5.00 5.50 6.00 6.50
pH
OM-Cu(mgkg-1
)
Fig. 4. Relation between OM-Cu and soil pH in the amended soils.
y = 4.6654x - 6.6406
R2
= 0.8043
0
5
10
15
20
25
30
4.50 5.00 5.50 6.00 6.50
pH
INOR-Cu(mgkg-1
)
Fig. 5. Relation between INOR-Cu and soil pH in the amended soils.

3.6. Lead
On day 1, total Pb concentration significantly increased
(p < 0.05) from 9–18 mg Pb kgÀ1
in controls to 37.5–
41.5 mg Pb kgÀ1
in SS treated soils and up to 47.8–
56.8 mg kgÀ1
in SSA treated soils. Sequential chemical
fractionation indicated that, on day 1, most of the Pb in
the amended soils was found as RES-Pb (28.4–
39.3 mg Pb kgÀ1
) and INOR-Pb (13.3–17.2 mg Pb kgÀ1
).
Both fractions were significantly higher in SS or SSA
amended soils than in the controls. A minor proportion
of Pb was found as OM-Pb (0.9–1.9 mg Pb kgÀ1
). Concen-
trations of EXCH-Pb remained below the levels of analyt-
ical detection. The nature of Pb association among soil
fractions on day 1 reflects the speciation of Pb in the
amendments.
day 1
0%
50%
100%
% EXCH-Pb
% OM-Pb
% INOR-Pb
% RES-Pb
day 60
0%
50%
100%
% EXCH-Pb
% OM-Pb
% INOR-Pb
% RES-Pb
day 270
0%
50%
100%
% EXCH-Pb
% OM-Pb
% INOR-Pb
% RES-Pb
% RES-Pb
day 360
0%
50%
100%
% EXCH-Pb
% OM-Pb
% INOR-Pb
Fig. 6. Distribution of Pb as a percentage of the average total amount in the water-soluble and exchangeable fraction (EXCH); organic matter bound
fraction (OM); inorganic precipitate fraction (INOR) and residual fraction (RES). Soils: Typic Hapludoll, Argiudoll and Natraquoll. C = control,
SS = sewage sludge amended soils, SSA = soils amended with the 70:30 DMW mixture of sewage sludge and sewage sludge ash.

An increase in INOR-Pb along with a decrease in RES-
Pb was observed in the three SS and SSA amended soil
samples in the subsequent sampling dates (Fig. 6). On
day 360, most of the Pb was found as INOR-Pb, possibly
precipitated as mineral phases, specifically associated with
Mn-oxides or in a mixture of Fe-oxide and finely divided
plumbogummite crystals (Morin et al., 2001). Calcite may
also act as a strong absorbent for Pb, and could complex
as double salts such as CaCO3 Æ PbCO3. Phosphate miner-
als were shown to bind Pb tightly in several studies on sta-
bilization of Pb in soil (Chen et al., 1997; Jensen et al.,
2006). No significant differences in INOR-Pb were
observed between SS or SSA treatments for the same soil
or among amended soils, indicating that differences in soil
texture or soil pH did not appear to influence Pb redistribu-
tion to this fraction.
OM-Pb was below analytical detection limits in all
sampling dates. These results differ from other authors,
who found a high proportion of organic Pb in sludge
amended soils (Planquart et al., 1999). Pb is reported to
form very stable complexes with humic substances, reduc-
ing Pb availability. Studies of lead uptake in complex soils
conclude that lead uptake capacity is best correlated with
soil pH and organic matter (Arnfalk et al., 1996; Gao
et al., 1997; Hooda and Alloway, 1998); and in a study
on the kinetics of Pb sorption and desorption, it was
shown that soil organic matter increased the adsorption
and impeded the desorption of Pb from soil (Strawn
and Sparks, 2000). However, this study shows that the
stable organic matter present in the SS or SSA amended
soils had a weak tendency to form stable organic com-
plexes with Pb. A possible reason for this is that the inor-
ganic matrix of both SS and SSA amendments enhanced
the formation of inorganic Pb compounds, regardless of
soil pH. This mineral neoformation may have led to the
development of reactive sorptive solid substrates which
can bind Pb. The formation of thermodynamically stable
minerals minimizes Pb bioavailability. The fact that
EXCH-Pb was below the analytical detection limits in
all sampling dates, suggests that solubilization reactions
are negligible.
The chemical partitioning of Pb into unreactive forms in
the sludge amended soils indicate that Pb bioavailability is
not of major concern for these soils The results obtained in
this study for Pb indicate that the chemical behavior of Pb
in different sludge amended soils may be similar, regardless
soil characteristics.
4. General discussion and conclusions
The largest proportion of Cd, Cu and Pb were initially
found in the residual fraction in the three amended soil
samples. PTE associated with the residual fraction are
usually considered as if they could not be released
(Legret, 1993). However, we observed a constant decrease
in the residual fraction of Cu and Pb in both SS and SSA
amended soils during the studied period, possibly due to
SS or SSA weathering. Cd, Cu and Pb would be expected
to be desorbed back and become available with time in
samples of soil amended with sludge. Conversely, environ-
mentally significant changes in labile Cd, Cu or Pb were
not observed in this study. On the contrary, there was a
shift of Cu and Pb from the residual to other stable frac-
tions considered unavailable for plant uptake. These
results were observed for the three soils and for both
amendments.
The chemical behavior of Cd and Pb originating from
the sludge in soils amended with sludge did not depend
on soil physico-chemical characteristics. However, a high
pH dependence of OM-Cu and INOR-Cu in soils amended
with sludge was observed.
Overall, the studies performed over three soil samples of
representative soils of the Pampas Region, Argentina,
showed that the use of a mixture of sewage sludge contain-
ing 30% DM of its own incinerated ash as a soil amend-
ment did not pose a significant risk of contaminating soil,
water or plants. Moreover, for the same fraction, there
were no significant differences between the concentration
of PTE for sewage sludge or for the mixture of sewage
sludge and ash amended soils, in spite of the high rates
applied. However, reactions in the environment are rarely
at equilibrium, but are instead in a state of continuous
change because of the dynamic processes occurring. The
results obtained in this study provide supporting evidence
for the protection theory, which hypothesizes that mineral
components may compensate for any loss of metal reten-
tion capacity caused by mineralization of organic compo-
nents (Chaney and Ryan, 1993).
From an agricultural point of view, the results obtained
in this study cannot be extrapolated directly for making
predictions about in situ Cd, Cu or Pb behavior in soils
amended with sludge. Land-applied sludge is subject to a
variety of factors that affect the availability of PTE. There-
fore, field experiments of fractionation and plant availabil-
ity of Cd, Cu and Pb following the application of these
amendments should be performed.
References
Alva, A.K., Huang, B., Paramasivam, S., 2000. Soil pH affects copper
fractionation and phytotoxicity. Soil Science Society of American
Journal 64, 955–962.
Alva, A.K., Baugh, T.J., Paramasivam, S., Sajwan, K.S., 2005. Adsorp-
tion/desorption of copper by a sandy soil amended with various rates
of manure, sewage sludge, and incinerated sewage sludge. Journal of
Environmental Science and Health – Part B Pesticides, Food
Contaminants, and Agricultural Wastes 40, 687–696.
Amato, M., 1983. Determination of 12
C and 14
C in plant and soil. Soil
Biology and Biochemistry 15, 611–612.
Arias, M., Pe´rez-Novo, C., Osorio, F., Lo´pez, E., Soto, B., 2005.
Adsorption and desorption of copper and zinc in the surface
layer of acid soils. Journal of Colloid and Interface Science 288,
21–29.
Arnfalk, P., Wasay, S.A., Tokunaga, S., 1996. A comparative study of Cd,
Cr(III), Cr(VI), Hg, and Pb uptake by minerals and soil materials.
Water Air and Soil Pollution 87, 131–148.

Berti, W.R., Jacobs, L.W., 1996. Chemistry and phytotoxicity of soil trace
elements from repeated sewage sludge applications. Journal of
Environmental Quality 25, 1025–1032.
Bhogal, A., Nicholson, F., Chambers, B., Shepherd, M., 2003. Effects of
past sewage sludge additions on heavy metal availability in light
textured soils: implications for crop yields and metal uptakes.
Environmental Pollution 121, 413–423.
Bierman, P.M., Rosen, C.J., 1994. Phosphate and trace metal availability
from sewage-sludge incinerator ash. Journal of Environmental Quality
23, 822–830.
Bierman, P.M., Rosen, C.J., Bloom, P.R., Nater, E.A., 1995. Soil solution
chemistry of sewage-sludge incinerator ash and phosphate fertilizer
amended soil. Journal of Environmental Quality 24, 279–285.
Blakemore, L.C., Searle, P.L., Daly, B.K. 1987. Methods for chemical
analysis of soils, NZ Soil Bureau Scientific Report 80, New Zealand
Soil Bureau, DSIR, Lower Hutt, New Zealand.
Bremmer, J.M., Mulvaney, C.S., 1982. Nitrogen-total. In: Page, A.L.,
Miller, R.H., Keeney, D.R. (Eds.), Methods of soil analysis: part 2, .
In: Agronomy, vol. 9. American Society of Agronomy, Madison, WI,
pp. 595–624.
Chambers, B., Royle, S., Hadden, S., Maslen, S., 2002. The use of
biosolids and other organic substances in the creation of soil-forming
materials. Journal of the Chartered Institution of Water and Envi-
ronmental Management 16, 34–39.
Chapman, H.D., 1965. Diagnostic criteria for plants and soils. In: Black,
C.A. (Ed.), Diagnostic Criteria for Plants and Soils. American Society
of Agronomy, No. 9, Riverside, California, pp. 902–904.
Chaudri, A.M., Allain, C.M., Barbosa-Jefferson, V.L., Nicholson, F.A.,
Chambers, B.J., McGrath, S.P., 2000. A study of the impacts of Zn
and Cu on two rhizobial species in soils of a long-term field
experiment. Plant Soil 221, 167–179.
Chen, X.B., Wright, J.V., Conca, J.L., Peurrung, L.M., 1997. Evaluation
of heavy metal remediation using mineral apatite. Water Air and Soil
Pollution 98, 57–78.
Corey, R.B., King, L.B., Lue-Hing, C., Fanning, D.S., Street, J.J., Walfer,
J.M., 1987. Effects of sludge properties on accumulation of trace
elements by crops. In: Page, A.L., Logan, T.J., Ryan, J.A. (Eds.), Land
Application of Sludge-food chain Implications. Lewis Publishers, Inc.,
Chelsea, MI, pp. 25–51.
Fuentes, A., Lloreńs, M., Saéz, J., Aguilar, M.I., Ortunõ, J., Meseguer, V.,
2004. Phytotoxicity and heavy metals speciation of stabilised sewage
sludges. Journal of Hazardous Materials 108, 161–169.
Gao, S.A., Walker, W.J., Dahlgren, R.A., Bold, J., 1997. Simultaneous
sorption of Cd, Cu, Ni, Zn, Pb, and Cr on soils treated with sewage
sludge supernatant. Water Air and Soil Pollution 93, 331–345.
Garcıá-Orenes, F., Guerrero, C., Mataix-Solera, J., Navarro-Pedrenõ, J.,
Go´mez, I., Mataix-Beneyto, J., 2005. Factors controlling the aggregate
stability and bulk density in two different degraded soils amended with
biosolids. Soil and Tillage Research 82, 65–76.
Hooda, P.S., Alloway, B.J., 1998. Cadmium and lead sorption behaviour
of selected english and Indian soils. Geoderma 84, 121–134.
Hsu, J.-H., Lo, S.L., 2000. Characterization and extractability of copper,
manganese, and zinc in swine manure composts. Journal of Environ-
mental Quality 29, 447–453.
Irving, H., Williams, R.J., 1953. Stability of transition metal complexes.
Journal of Chemical Society, 3182–3210.
Jakobsen, P., Willett, I.R., 1986. Comparisons of the fertilizing and liming
properties of lime-treated sewage sludge with its incinerated ash.
Fertilizer Research 9, 187–197.
Jensen, P.E., Ottosen, L.M., Pedersen, A.J., 2006. Speciation of Pb in
industrially polluted soils. Water, Air, and Soil Pollution 170 (1–4),
359–382.
Jiang, R.F., Yang, C.G., Su, D.C., Wong, J.W.C., 1999. Coal fly ash and
lime stabilized biosolids as an ameliorant for boron deficient acidic
soils. Environmental Technology 20, 645–649.
Lavado, R., Zubillaga, M.S., Alvarez, R., Taboada, M., 2004. Baseline
levels of potentially toxic elements in Pampas soils. Soil and Sediment
Contamination 13, 427–437.
Legret, M., 1993. Speciation of heavy metals in sewage sludge and sludge-
amended soil. International Journal of Environmental and Analytical
Chemistry 51, 161–165.
Lena, Q., Gade, N., 1997. Chemical fractionation of cadmium, copper,
nickel, and zinc in contaminated soils. Journal of Environmental
Quality 26, 259–264.
Marinari, S., Masciandaro, G., Ceccanti, B., Grego, S., 2000. Influence of
organic and mineral fertilisers on soil biological and physical proper-
ties. Bioresource Technology 72, 9–17.
Martıńez, C.E., Motto, H.L., 2000. Solubility of lead, zinc and copper
added to mineral soils. Environmental Pollution 107, 153–158.
McBride, M.B., Martinez, C.E., Topp, E., Evans, L., 2000. Trace metal
solubility and speciation in a calcareous soil 18 years after no-till
sludge application. Soil Science 165, 646–656.
McBride, M.B., 1995. Toxic metal accumulation from agricultural use of
sludge: are USEPA Regulations protective? Journal of Environmental
Quality 24, 5–18.
McGrath, S.P., Cegarra, J., 1992. Chemical extractability of heavy metals
during and after long-term applications of sewage sludge to soil.
Journal of Soil Science 43, 313–321.
Mellbye, M.E., Hemphill, D.D., Volk, V.V., 1982. Sweet corn growth on
incinerated sewage sludge-amended soil. Journal of Environmental
Quality 11, 160–163.
Miller, W.P., Miller, D.M., 1987. A micropipette method for soil
mechanical analysis. Communications in Soil Science and Plant
Analysis 18, 1–15.
Miller, W.P., Martens, D.C., Zelazny, L.W., 1986. Effect of sequence in
extraction of trace metals from soils. Soil Science Society of America
Journal 50, 598–601.
Morin, G., Juillot, F., Ildefonse, P., Calas, G., Samama, J.C., Chevallier,
P., Brown, G.E., 2001. Mineralogy of lead in a soil developed on a Pb-
mineralized sandstone (Largentiere, France). American Mineralogist
86, 92–104.
Nyamangara, J., 1998. Use of sequential extraction to evaluate zinc and
copper in a soil amended with sewage sludge and inorganic metal salts.
Agriculture, Ecosystems and Environment 69, 135–141.
Obrador, A., Rico, M.I., Alvarez, J.M., Novillo, J., 2001. Influence of
thermal treatment on sequential extraction and leaching behaviour of
trace metals in a contaminated sewage sludge. Bioresource Technology
76, 259–264.
Pan, S.C., Tseng, D.H., 2001. Sewage sludge ash characteristics and its
potential applications. Water Science Technology 44, 261–267.
Planquart, P., Bonin, G., Prone, A., Massiani, C., 1999. Distribution,
movement and plant availability of trace metals in soils amended with
sewage sludge composts: application to low metal loadings. Science of
the Total Environment 241, 161–179.
S.A.D.S. 2001. Secretarıá de Ambiente y Desarollo Sustentable, Ministe-
rio de Salud y Ambiente. Resolucioń 97/01, Anexo 1, p. 62.
Saikia, N., Kato, S., Kojima, T., 2006. Compositions and leaching
behaviours of combustion residues. Fuel 85, 264–271.
Sajwan, K.S., Paramasivam, S., Alva, A.K., Adriano, D.C., Hooda, P.S.,
2003. Assessing the feasibility of land application of fly ash, sewage
sludge and their mixtures. Advances in Environmental Research 8, 77–
79.
Scancar, J.R., Milacic, M., Strazar, M., Burica, O., 2002. Total metal
concentrations and partitioning of Cd, Cr, Cu, Fe, Ni and Zn in
sewage sludge. Science of the Total Environment 250, 9–19.
Shuman, L.M., 1985. Fractionation method for soil microelements. Soil
Science 140, 11–22.
Smith, S.R., 1994. Effect of soil pH on availability to crops of metals in
sewage sludge-treated soils. I. Nickel, copper and zinc uptake and
toxicity to ryegrass. Environmental Pollution 85, 321–327.
Smith, S.R., 1996. Agricultural Recycling of Sewage Sludge and the
Environment. CAB International, Wallingford, UK.
Soriano, A., 1991. Temperate subhumid grasslands of South America. In:
Coupland, R.T. (Ed.), Temperate subhumid grasslands. Ecosystems of
the World, vol. 8A, Natural Grasslands. With sections by R.J.C. Leoń
(Geographic Limits, Geomorphology and Geology, Regional Subdi-

visions and Vegetation), O.E. Sala (Structure and Function), R.S.
Lavado (Soils), J.H. Lemcoff (Climate), A. Soriano, V.A. Deregibus
and R.S. Lavado (Land use), M.A. Cahuepe´, C.A. Velazquez and O.A.
Scaglia (Fauna). Elsevier Scientific Publishing Company, Amsterdam,
pp. 367–407.
Strawn, D.G., Sparks, D.L., 2000. Effects of soil organic matter on the
kinetics and mechanisms of Pb(II) sorption and desorption in soil. Soil
Science Society of America Journal 64, 144–156.
Su, D.C., Wong, J.W.C., 2004. Chemical speciation and phytoavailability
of Zn, Cu, Ni and Cd in soil amended with fly ash-stabilized sewage
sludge. Environment International 29, 895–900.
Theis, T.L., Gardner, K.H., 1990. Environmental assessment of ash
disposal. Critical Reviews in Environmental Control 20, 21–42.
Torri, S., Lavado, R., 2002. Distribucioń y disponibilidad de elementos
potencialmente to´xicos en suelos representativos de la provincia de
Buenos Aires enmendados con bioso´lidos. (Distribution and availabil-
ity of potentially toxic elements in representative soils of Buenos Aires
Province as a result of biosolid application). Ciencia del Suelo 20, 98–
109.
Torri, S. 2001. Distribucioń y biodisponibilidad de Cd, Cu, Pb y Zn en
suelos fertilizados con bioso´lidos. (Distribution and availability of Cd,
Cu, Pb y Zn in sewage sludge amended soils). M Sci. Dissertation.
University of Buenos Aires, Faculty of Agronomy, Argentina.
Torri, S., Alvarez, R., Lavado, R., 2003. Mineralization of Carbon from
Sewage sludge in three soils of the Argentine pampas. Communica-
tions in Soil Science and Plant Analysis 34, 2035–2043.
Tsadilas, C.D., Matsi, T., Barbayiannis, N., Dimoyiannis, D., 1995.
Influence of sewage sludge application on soil properties and on the
distribution and availability of heavy metal fractions. Communications
in Soil Science and Plant Analysis 26, 2603–2619.
USDA, 1999. Soil taxonomy – a basic system of soil classification for
making and interpreting soil surveys, second ed. Soil survey staff,
United States Department of Agriculture, Natural Resources Conser-
vation Service. Agriculture Handbook Number 436.
USEPA, 1993. Land application of sewage sludge: a guide for land-
appliers on the requirements of the federal standards for the use
or disposal of sewage sludge, 40 CFR Part 503. EPA-831-B-93-
002b.
Vaca-Paulıń, R., Esteller-Alberich, M., Lugo-de la Fuente, J., Zavaleta-
Mancera, H.A., 2006. Effect of sewage sludge or compost on the
sorption and distribution of copper and cadmium in soil. Waste
Management 26, 71–81.
Walter, I., Cuevas, G., 1999. Chemical fractionation of heavy metals in a
soil amended with repeated sewage sludge application. Science of the
Total Environment 226, 113–119.
Wang, C., Hu, X., Chen, M.L., Wu, Y.H., 2005. Total concentrations and
fractions of Cd, Cr, Pb, Cu, Ni and Zn in sewage sludge from
municipal and industrial wastewater treatment plants. Journal of
Hazardous Materials 119, 245–249.
Wong, J.W.C., 1995. The production of artificial soil mix from coal fly ash
and sewage sludge. Environmental Technology 16, 741–751.
Zhang, F., Yamasaki, S., Nanzyo, M., 2002a. Waste ashes for use in
agricultural production: I. Liming effect, contents of plant nutrients
and chemical characteristics of some metals. Science of the Total
Environment 284, 215–225.
Zhang, F., Yamasaki, S., Kimura, K., 2002b. Waste ashes for use in
agricultural production: II. Contents of minor and trace metals.
Science of the Total Environment 286, 111–118.
Zhu, B., Alva, A.K., 1993. Distribution of trace metals in some sandy soils
under citrus production. Soil Science Society of America Journal 57,
350–355.
Zufiaurre, R., Olivar, A., Chamorro, P., Nerıń, C., Callizo, A., 1998.
Speciation of metals in sewage sludge for agricultural uses. Analyst
123, 255–259.

Dynamics of Cd, Cu and Pb added to soil through different kinds of sewage sludge

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Dynamics of Cd, Cu and Pb added to soil through different kinds of sewage sludge

Semelhante a Dynamics of Cd, Cu and Pb added to soil through different kinds of sewage sludge (20)

Mais de Silvana Torri

Mais de Silvana Torri (20)

Último

Último (20)

Dynamics of Cd, Cu and Pb added to soil through different kinds of sewage sludge