Artículo en PDF
How to cite
Complete issue
More information about this article
Journal's homepage in redalyc.org
Sistema de Información Científica
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
GEOCHEMICAL DISTRIBUTION AND MOBILITY FACTORS OF Zn AND Cu IN SEDIMENTS
OF THE RECONQUISTA RIVER, ARGENTINA
Alicia RENDINA
1
, Laura de CABO
2
, Silvana ARREGHINI
2
, Martha BARGIELA
1
and Alicia FABRIZIO de IORIO
1
1
Departamento de Recursos Naturales y Ambiente, Facultad de Agronomía, Universidad de Buenos Aires. Av. San
Martín 4453, 1417, Buenos Aires, Argentina
2
Museo de Ciencias Naturales, B. Rivadavia, Av. Ángel Gallardo 470, 1405, Buenos Aires, Argentina
(Recibido mayo 2000, aceptado agosto 2001)
Key words: copper, zinc, sequential fractionation, river-sediment
ABSTRACT
This paper describes the distributions of Cu and Zn among the geochemical phases of the
surface
sediments of the Reconquista River and its main tributary streams (La Choza and
Durazno). The distribution patterns of both metals among the geochemical non-residual phases,
obtained by a sequential extraction procedure did not suffer alteration in any of the geochemi-
cal environments of the seven sampling sites. The main mobile retention phase of Cu was
organic matter-sulfide, whereas for Zn they were the oxides of Fe and Mn. The mobility
factors of Cu and Zn allowed distinguishing areas of high and low anthropogenic impact. The
mobility factor of Zn was close to one in the upper basin, except for La Choza Stream, present-
ing very high values in the main channel of the river. The mobility factor of Cu was high in the
middle and low stretches of the river, while in the upper basin the content of mobile Cu was
low. The decline both in mobility factors and total content of metals in the sediments near the
river mouth evidenced the self-purification power of this watercourse.
Palabras clave: cobre, zinc, fraccionamiento secuencial, sedimentos fluviales
RESUMEN
Este trabajo describe la distribución del Cu y del Zn entre las fases geoquímicas de los
sedimentos superficiales del cauce del Río Reconquista y sus principales arroyos tributarios
(La Choza y Durazno). Los patrones de distribución de ambos metales entre las fases
geoquímicas no residuales, obtenidas con un procedimiento de extracción secuencial, no
sufrieron alteraciones en ninguno de los ambientes geoquímicos de los siete sitios de muestreo.
La principal fase móvil de retención de Cu fue la materia orgánica-sulfuros, mientras que para
el Zn fueron los óxidos de Fe y Mn. Los factores de movilidad del Cu y del Zn permiten
distinguir áreas de alto y bajo impacto antropogénico. El factor de movilidad del Zn fue
cercano a uno en la cuenca alta, a excepción del arroyo La Choza, presentando valores muy
altos en el cauce principal del río. El factor de movilidad del Cu fue alto en las cuencas media
y baja, mientras que la alta presentó contenidos bajos de Cu móvil. La disminución tanto en
los factores de movilidad como en las concentraciones totales de ambos metales en la desem-
bocadura del río, pusieron en evidencia el poder de autodepuración de este curso de agua.
Rev. Int. Contam. Ambient.
17
(4) 187-192, 2001
A. Rendina
et al.
188
INTRODUCTION
Most of the rivers and streams in urban areas of the
Buenos Aires Province contain at present a high load of
urban and industrial wastes (Herkovits
et al
. 1996, Castañé
et al
. 1998). The impact produced by the human activities
on these watercourses results in the alteration of the natu-
ral balance of the systems. In the case of heavy-metal
contamination, various studies have shown the importance
of the geochemical partitioning in the sediments of streams,
rivers and lakes (e.g. Allen 1993, Tack and Verloo 1995),
to interpret the mechanisms that determine its association
with the sediment, mobilization and bioavailability. By means
of techniques of sequential chemical extractions, metals
were partitioned within chemical conceptual phases, al-
lowing the distinction between metals linked to more mo-
bile phases (non-residual), and not very mobile metals re-
lated to the silicated minerals of sediments (residual). Sev-
eral authors (e.g. Calmano
et al.
1993) have observed
that an increment in the content of heavy metals of
geochemical non-residual fractions was associated to con-
tamination processes, predominantly anthropogenic (Grif-
fin
et al
. 1989). Lesmes (1996), who proposed a ranking
of mobility factors, based on the “total metal/residual metal”
ratio, applied this concept to distinguish between natural
values and those originated in human activities.
The Reconquista River, receives untreated sewage and
toxic effluents from the industrial belt mainly located in its
middle and low basins. The river contributes a third part of
the toxic contamination of De la Plata River, which provides
drinkable water to the urban conglomerate of Buenos Ai-
res City and part of the province of Buenos Aires. Previous
studies have described the physical, chemical and biological
conditions of this watercourse (Herkovits
et al.
1996,
Arreghini
et al
. 1997, Castañé
et al
. 1998); however, the
potential ecological risk of the heavy metals associated to
the river sediments has not been evaluated yet. Loez and
Salibián (1990) and Castañé
et al
. (1998) have established
that the average levels of dissolved heavy metals in this
river surpass the established limits for the protection of the
aquatic life, even in the least contaminated site (Cascallares)
Cu and Zn reached very high levels. These heavy metals
derive from wastes of industries such as galvanoplasty,
electric materials, paints, etc., of which there are plenty in
this region (Pescuma and Guaresti 1992).
The present study investigates the distribution of Cu
and Zn among the geochemical phases of sediments of
Reconquista River and differentiates areas of high and
low potential mobility of these metals.
MATERIALS AND METHODS
Study area
The Reconquista River basin has a surface of 169,000
ha, 72,000 of which are devoted to agriculture and cattle
breeding. The rest of this basin is urbanized (three million
inhabitants) with over 12,000 industries located in the area.
The Reconquista is a lowland river of Buenos Aires Prov-
ince, that starts at the confluence of La Choza and Durazno
streams and drains into the Luján River, which in turn dis-
charges it waters into De la Plata River. This watercourse
is characterized by having a low flow during the summer
(0.6 m
3
s
-1
to 1.0 m
3
s
-1
) which can be further reduced due
to obstructions caused by the accumulation of garbage
under the bridges.
Three sampling sites (
Fig. 1
) were located in the up-
per basin: La Choza Stream (E1), Durazno Stream (E2)
and Cascallares (E3=5 km). The middle basin was repre-
sented by Gorriti (E4=20 km), whereas the sampling sites
of low basin were: San Martin (E5=38 km), Bancalari
(E6=46 km) and Tigre (E7=55 km). The land use in the
upper basin is predominantly rural and agricultural with
some urban settlements in E3, while the middle basin rep-
resents the periphery of a very industrialized (food and
rubber industries) and urbanized area. The low basin starts
downstream of Moron Stream, which receives untreated
sewage from a variety of industries (food, tannery, chem-
istry, and non-ferrous smelting), that confer its waters the
characteristic of a raw sewer
effluent. E5 and E6 also
receive the impact of chemical, food, tannery and non-
ferrous smelting industries, as well as of landfills and wastes
of a densely populated area. E7 is located in a urban sec-
tor with few industries, near the mouth of the Reconquista
River, where it flows into the Luján River, which in turn
drains into the De la Plata River Estuary.
Sampling and chemical analysis
Sediments were collected with a grab-sampler at seven
sampling stations (
Fig. 1
), packed in airtight plastic bags,
R
e
q
u
is
ta
R
iv
e
r
Aires
La Choza
Stream
D
u
raz
n
o
S
tream
Ing.
Roggero
Dam
Morón
Stream
Río de
la Plata
E4
L
uján R
iver
E3
E1
E2
E6
E7
58°30'
58°45'
59°00'
59°15'
34°45'
34°30'
0
10
20 Km
59º15´
59º00´
58º45´
58º30´
34º30´
34º45´
N
E
S
O
E7
E6
Río de
la Plata
Luján River
E4
Morón
Stream
Buenos
Aires
Reconquista
River
E3
E1
E2
Ing.
Roggero
Dam
La Choza
Stream
Durazno Stream
Fig. 1.
Map of the investigated area and sampling locations
GEOCHEMICAL DISTRIBUTION AND MOBILITY FACTORS OF Zn AND Cu IN SEDIMENTS
189
transported immediately to the laboratory, and frozen until
analysis. Three subsamples, then pool into a composite
sample, were taken in each location. Three one-gram
portions (oven dry wt.) of each sample were submitted
to the sequential extraction procedure of Tessier
et al
.
(1979). The sequence can be summarized as follows:
Fraction 1: exchangeable, 1M MgCl
2
, pH 7, for 1h.
Fraction 2: bound to carbonate, 1M sodium acetate, pH
5, for 5 h.
Fraction 3: bound to amorphous Fe and Mn oxides, 0.04
M hydroxylamine hydrochloric acid in 25 %
(v/v) at 96
°
C, for 6 h.
Fraction 4: bound to organic matter and sulfides, 30 %
H
2
O
2
and 0.02 M nitric acid at 85
°
C, for 5 h.
Fraction 5: residual, concentrated HNO
3,
HClO
4
and
HF.
The effectiveness of the sequential extraction pro-
cesses was assured by comparing the sum of each frac-
tion with the amount of all the metals extracted by HNO
3
-
HClO
4
-HF. The error of the sequential extraction method
is generally around 12 %. Cu and Zn concentrations in
all the extracts were measured by inductive coupling
plasma atomic emission spectrophotometry (ICPAES).
RESULTS AND DISCUSSION
Zinc
The total concentration of Zn ranged between 104
and 1,092 mg kg
-1
in E2 and E6, respectively (
Table I
).
Zn concentrations in each chemical fraction, considered
as percentages of total Zn, are shown in
Figure 2
. E2
and E3 had low percentages of non-residual Zn (21 and
26 %, respectively), indicating a low contribution of this
element by human activities, but the effects of natural
weathering and erosion processes on the drainage of the
upper basin. On the contrary, the other sites had high
levels of non-residual Zn (70-85 %), denoting a great
anthropogenic accumulation of this element.
The Zn distribution among the most mobile fractions
(F1, F2, F3, and F4) in all seven sites showed that the
oxides of Fe and Mn were the most important Zn sinks
(13–67 % of total Zn), followed by organic matter-sul-
fide (3–18 % of total Zn), carbonates (2–7 % of total
Zn), and exchangeable (0.2-1.3 % of total Zn). These
results would indicate that the main mechanism involved
in the retention of the Zn is adsorption or coprecipitation
with Fe and Mn oxides. The association between Zn and
the oxides of Fe and Mn in sediments and soils has been
widely recognized (Kuo
et al
. 1983, Fernandes 1997).
Osaki
et al
. (1990a) studied the differential adsorption of
Zn on fine particles in riverbed sediments, particulates
and kaolin, observing that this metal was mostly adsorbed
on fine sediments. These authors also indicate that this
greater adsorption may obey to the presence of Mn and
Fe oxides and/or of organic matter on these particles.
Taking into account that the fraction of adsorbed metals
increases at higher concentrations of adsorbent solid (Lion
et al
. 1982), a high content of Fe and Mn (2,100
µ
g/g and
350
µ
g/g on average respectively) in the oxide fraction of
the sediments, would facilitate a great accumulation of
Zn. In addition, since Zn is the most abundant metal in
these sediments (Rendina
et al
. 1997), a concentration
effect (order of abundance) may also determine the high
percentage of Zn adsorbed in this fraction, as previously
found by Galvez-Cloutier and Dubé (1998). This does
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
E1
E2
E3
E4
E5
E6
E7
F5
F4
F3
F2
F1
100%
90%
80%
70%
60%
50%
40%
30%
20%
0%
10%
E1
E7
E6
E5
E4
E3
E2
F5
F4
F3
F2
F1
TABLE I.
RESIDUAL AND TOTAL CONTENT OF Cu AND Zn, AND THEIR MOBILITY FAC-
TORS (
f
)
Sites
Residual Zn
Total Zn
Residual Cu
Total Cu
f
Zn
f
Cu
E1
86.1
459.4
26.1
37.7
5.3
1.4
E2
82.4
103.8
30.2
44.8
1.2
1.5
E3
89.2
119.8
44.4
64.5
1.3
1.4
E4
117.9
468.4
76.6
161.9
4.0
2.1
E5
158.0
994
85.3
239.6
6.3
2.8
E6
159.0
1092
99.7
255.6
6.9
2.6
E7
106.5
361
78.6
120.3
3.4
1.5
Fig. 2.
Partitioning of Zn within different fractions in sediments
A. Rendina
et al.
190
not occur in the oxidizable fraction, since Zn is unable to
compete for the formation of highly stable complexes
between organic matter and Cu, as observed by Nriagu
and Coker (1980) in sediments of Ontario Lake.
Some authors have observed different affinities of Zn
for the distinct geochemical phases of the sediments in
different environments (El Ghobary and La Touche 1982,
Griffin
et al
. 1989, Tingzong Guo
et al
. 1997), while oth-
ers (e.g. Fernandes 1997) do not observe changes in the
distribution pattern of Zn among the non-residual phases.
Nevertheless, a discussion of these results is not only
difficult due to the various methodologies applied to es-
tablish the relative importance of each geochemical phase
in the retention of heavy metals, but also owing to the
different physical and chemical conditions (e.g. Eh, pH,
ionic strength) of the analyzed sediments.
The predominantly lithogenous origin of Zn, can be
inferred by the high percentages of this element in the
residual phase (81 % of total Zn in E2 and 76 % of total
Zn in E3), in coincidence with the lower Zn content in the
sediments at the upper basin, where the land use is mainly
cattle raising on natural pastures. The large fraction of
total Zn associated with the residual phase is unlikely to
be removed due to changes in the physicochemical con-
ditions (Griffin
et al
. 1989). The low percentages of re-
sidual Zn (18 % of total Zn) and the high concentrations
of total Zn found in E1, contrasted with E2 and E3 (82
and 89 % respectively). This may be due to the effect of
effluents from food industries (Pescuma and Guaresti
1992) inflowing through La Choza Stream.
The Zn mobility factors in the seven sampling stations
are shown in
Table I
. The mobility factors of Zn in E2
and E3 were close to one, indicating low contamination
by this element. The other sites (E1 and the whole middle
and low courses) presented very high mobility factors,
denoting an important level of Zn contamination. The re-
ducible phase (F3) of the sediments is the main contrib-
uting factor to Zn mobility. In F3 the mobilization of Zn
may be coupled to the redox cycling of Mn (Osaki
et al
.
1990b), since under reducing conditions, Mn(IV) can be
reduced to Mn(II) more easily than Fe (owing to differ-
ences between their redox potentials), thus inducing Zn
solubilization. The decline in the Zn mobility factor and
the total concentration of the metal in the sediments of
E7 may obey to the dilution effect produced by the De la
Plata Estuary and also to a lesser anthropic impact. The
total content of Zn recorded in this site is in good agree-
ment with the values reported by Villar
et al.
(1998) for
this estuary.
Copper
The total content of Cu ranged between 37.7 and 256
mg kg
-1
in E1 and E6, respectively (
Table I
). The
geochemical partition of Cu among sampling stations is
shown in
Figure 3
. In all seven sites, the main retention
phase of Cu in the sediments was F4. This result is in
agreement with published data (Griffin
et al
. 1989,
Fernandes
et al
. 1997, Larocque and Rasmussen 1998).In
its oxidizable phase, Cu can either be coupled to active
sites of organic molecules (OH of carboxylic and phe-
nolic groups of organic substances) or precipitate as sul-
fide. An investigation on the bed sediments of this river
(Iorio
et al
. 1997) revealed that the humic compounds
predominantly form complexes with Fe and Cu, having
the latter one a stronger affinity for humic acids. Huang
and Yang Y.L. (1995) also found a more pronounced af-
finity of Cu for humic acids with respect to fulvic acids,
in synthetic humus-kaolin complexes. Studies on prefer-
ential absorption (Rashid 1985) indicate that among the
transition metals assayed, Cu competed more strongly
for the bonding sites of the humic material.
E1, E2 and E3 presented the lowest proportions of
Cu in this fraction (22, 17 and 18 % of total Cu, respec-
tively), whereas the highest percentages of this metal
were found in E5 and E6 (58 and 57 %, respectively), in
coincidence with the greatest contributions of organic
waste of industrial origin. The significant increment of
Cu in F4, starting from E4, can be related to diagenetic
processes associated with a marked decline in dissolved
oxygen in water column (Arreghini
et al
. 1997), and to
an increase in the organic matter content of the sediment
(4.8, 1.8, 2.8, 8.2, 12, 13, and 5.8 % in E1, E2, E3, E4, E5,
E6, and E7, respectively), for which the sulfide content
of that fraction would also increase markedly.
This deterioration on the water quality of the
Reconquista River was attributed to the anthropogenic
impact produced by the inflowing waters of Morón
Stream (de Cabo
et al
. 2000). These authors also re-
ported high conductivities in E5, located 1 km downstream
from Morón Stream. The presence of elevated amounts
of dissolved salts would transform the hydrophilic organo-
metallic complexes into hydrophobic forms that would
finally precipitate, thus incorporating quelated metals into
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
E1
E2
E3
E4
E5
E6
E7
F5
F4
F3
F2
F1
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
E1
E2
E3
E4
E5
E6
E7
F5
F4
F3
F2
F1
Fig. 3.
Partitioning of Cu within different fractions in sediments
GEOCHEMICAL DISTRIBUTION AND MOBILITY FACTORS OF Zn AND Cu IN SEDIMENTS
191
the riverbed sediments. The Cu bound to the other mo-
bile fractions was very low, being 0.2–1.7 % in F1, 0.5–
5.1 % in F2 and 2.8–11 % in F3.
Cu in the residual fraction represented 70, 68 and 70 %
of total Cu in E1, E2 and E3, respectively, hereas in E4,
E5 and E6 it only reached 48, 35 and 39 %, respectively.
The percentage of residual Cu in E7 as similar to that of
sites undergoing lesser impact (E1, E2 and E3).
The mobility factor of Cu (
Table I
) exhibited low
values (close to one) in E1, E2 and E3, in coincidence
with the lower content of total Cu found. Mobility factors
were high (over 2) in E4, E5 and E6, but diminished in
E7, probably owing to the dilution of the fluvial sediments
with less polluted sediments from the estuary, and to a
greater distance from the contamination sources. In all
sites, the high percentages of Cu in the oxidizable phase
of the sediments (F4) were responsible for the values of
Cu mobility factor. In this reducing environment, the
complexed metal-organic matter systems are difficult to
oxidize. Bacteria cannot easily attack this humic acid
fraction in anaerobic sediments; therefore, the complexes
formed there are much more stable than in oxidized
environments (Patrick and Pardue 1992). On the other
hand, part of the Cu in F4, can precipitate as cupric sulfide
under reducing conditions. In spite of being hardly solu-
ble and also stable under reducing conditions, these
compounds can be oxidized by sulfide-oxidizing bacteria
to form sulfate under oxidizing conditions, thus releasing
the metallic ion back into solution.
In agreement with the sequence established by Irving
and Williams (1953) for the stability of complexes
(Mn<Fe=Ni<Zn<Pb<Cd<Cu), and also with the stability
of metallic sulfides, in all of the study sites the percentage
of Cu in the oxidizable fraction was higher than Zn.
According to these authors, the selectivity order for the
amorphous oxides of Fe and Mn also denotes a higher
affinity for Cu than Zn. However, in the present study,
the accumulation order found in the reducible phase was
the opposite one (Zn>Cu). This result may be attributed
to a concentration effect, since the Zn content of the
sediments in all seven sites was much higher than Cu.
The influence of the different concentrations of heavy
metals on the fraction of an adsorbed metal in multivariate
systems has also been postulated by other authors for
natural sediments (e.g. Galvez-Cloutier and Dubé 1998).
CONCLUSIONS
In the areas where the land use is mainly agriculture
and cattle raising, the concentrations of total metals in
riverbed sediments and their mobilities were low. On the
contrary, in those zones were the land use is either indus-
trial or urban, the concentrations of total metals in sedi-
ments and their mobilities increased, thus becoming ar-
eas of high risk for the aquatic life.
The lower concentrations of total metals in the sedi-
ments and the lower mobility factors found in the site
closer to the river mouth are good indicators of the self-
purification sites capability of the riverbed. The results of
sediment fractionating indicate that in all of the study sites,
the main mobile phase of Zn were the oxides of Fe and
Mn. On the other hand, Cu was mainly bound to mobile
phase organic matter-sulfide. The differences in the
geochemical environment from the headwaters to the mouth
of the Reconquista River, do not alter the distribution pat-
tern of heavy metals among the non-residual fractions of
the sediments. The values of the Zn mobility factor in middle
and low stretches of the Reconquista River basin were
much higher than those of Cu. This result indicates a greater
contribution of anthropogenic Zn due to the influences of
the large population end industrialization of this region.
ACKNOWLEDGMENT
We thank the Prefectura Naval Argentina for their
continuing support in the collection of samples.
REFERENCES
Allen H. (1993). The significance of trace metal speciation for
water, sediment and soil quality criteria and standards. Sci.
Total Environ. Suppl. 1993, 23-45.
Arreghini S., de Cabo L., Iorio A. F. de, Rendina A., Bargiela
M., Godoy di Pace G., Corujeira A., Vella R. and Bonetto C.
(1997). Evaluación de la calidad de aguas del Río
Reconquista a través de índices. Mem. Congr. Int. sobre
Aguas, Buenos Aires, III 24.
Calmano W., Hong J. and Förstner U. (1993). Binding and
mobilization of heavy metals in contaminated sediments
affected by pH and redox potential. Wat. Sci. Tech.
28
, 223-
235.
Castañé P., Loez C., Olguín H., Puig A., Rovedatti M., Topalián
M. and Salibian A. (1998). Caracterización y variación es-
pacial de parámetros fisicoquímicos y del plancton en un
río urbano contaminado (Río Reconquista, Argentina). Rev.
Int. Contam. Amb.
14
, 69-77.
de Cabo L., Arreghini S., Iorio A. F. de, Rendina A., Vella R. and
Bonetto C. (2000). Impact of the Morón stream on water
quality of the Reconquista River (Buenos Aires, Argentina).
Rev. Mus. Argentino Cienc. Nat.
2
, 123-130.
El Ghobary H. and La Touche C. (1982). Metal early diagenesis
and pollution in the tidal flats of the Marennes Oleron Bay:
Application of metal sequential extraction. Oceanologica
Acta, No SP, 119-128.
Fernandes H. M. (1997). Heavy metal distribution in sediments
and ecological risk assessment: the role of diagenetic pro-
cesses in reducing metal toxicity in bottom sediments.
A. Rendina
et al.
192
Environ. Pollut.
97
, 317-325.
Griffin T. M., Rabenhorst M. C. and Fanning D. S. (1989). Iron
and trace metals in some tidal marsh soils of the Chespeake
Bay. Soil Sci. Society of America J.
53
, 1010-1019.
Galvez-Cloutier R. and Dubé J. S. (1998). An evaluation of fresh
water sediments contamination: the Lachine canal sediments
case, Montreal, Canadá. Part II: Heavy metal particulate
speciation study. Water, Air, Soil Pollut.
102
, 281-302.
Herkovits J., Pérez-Coll C. S. and Herkovits F. D. (1996).
Ecotoxicity in the Reconquista River, Province of Buenos
Aires, Argentina: a preliminary study. Environ. Health
Perspect.
104
, 186-189.
Huang C. and Yang Y.L. (1995). Adsorption characteristics of
Cu(II) on humus-kaolin complexes. Wat. Res.
29
, 2461-
2466.
Iorio A. F. de, Barros M. J., Rendina A., di Risio C., García A.,
Bargiela M., de Cabo L., Arreghini S., de Siervi M. and Vella
R. (1997). Distribución de metales pesados en ácidos
húmicos y fúlvicos de sedimentos del Río Reconquista
(Buenos Aires, República Argentina). Mem. Congr. Int.
sobre Aguas, Buenos Aires, Argentina. III. 38.
Irving H. and Williams R. J. G. (1953) Stability of transition
metals complexes. J. Chem. Soc. 3182-3210.
Kuo S., Hellman P. E. and Baker A. S. (1983). Distribution and
forms of copper, zinc, cadmium, iron, and manganese in
soils near a copper smelter. Soil Sci.
135
, 101-109.
Larocque A. C. L. and Rasmussen P. E. (1998). An overview of
trace metals in the environment, from mobilization to
remediation. Environ. Geol.
33
, 85-91.
Lesmes L. E. (1996). Estudio de un factor de movilidad en
geoquímica ambiental. Environ. Geochem. in Tropical Coun-
tries. 2nd. International Symposium. Cartagena, Colombia.
Lion L. W., Altmann R. S. and Leckie J. O. (1982). Trace-metal
adsorption characteristics of estuarine particulate matter:
evaluation of contributions of Fe/Mn oxide and organic
surface coatings. Environ. Sci. Technol.
16
, 660-676.
Loez C. and Salibian A. (1990). Premiéres donées sur le phy-
toplankton et les caractéristiques phisico–chemiques du
Río Reconquista (Buenos Aires, Argentina). Une riviére
urbaine polluée. Rev. Hydrobiol. Trop.
23
, 283-296.
Nriagu J. and Coker R.
(1980). Trace metals in humic and fulvic
acids from lake Ontario sediments. Environ. Sci. Technol.
2, 443-446.
Osaki S., Miyoshi T., Sugihara S. and Takashima Y. (1990a).
Adsorption of Fe(III), Co(II) and Zn(II) onto particulates
in fresh waters on the basis of the surface complexation
model. I. Stabilities of metal species adsorbed on particu-
lates. Sci. Total Environ.
99
, 105-114.
Osaki S., Miyoshi T., Sugihara S. and Takashima Y. (1990b).
Adsorption of Fe(III), Co(II) and Zn(II) onto particulates
in fresh waters on the basis of the surface complexation
model. II. Stabilities of metal species dissolved in fresh
waters. Sci. Total Environ.
99
, 115-123.
Patrick W.H. Jr and Pardue J. (1992). Redox and pH condi-
tions affecting solubility and mobility of copper in wet-
lands. Proc. Bioavail. Toxic. of Copper. Workshop
Goinesville, Florida, 49-71.
Pescuma A. and Guaresmi M. E. (1992). Proyecto de sanea-
miento ambiental y control de inundaciones de la cuenca
del Río Reconquista. Informe final. Buenos Aires, 180 p.
Rashid M. A. (1985).
Geochemistry of marine humic com-
pounds
. Springer Verlag, New York, 300 p.
Rendina A., Iorio A. F. de, Bargiela M., García A., Barros M. J.,
de Cabo L. and Arreghini S. (1997). Distribution of heavy
metals in water and sediment of a polluted river of Argen-
tina. XIII International Symposium on Environmental Bio-
geochemistry. Vol.
1
, p. 182.
Tack F. M. G. and Verloo M. G. (1995). Chemical speciation and
fractionation in soil and sediment heavy metal analysis: a
review. Environ. Anal. Chem.
59
, 225-238.
Tessier A., Campbell P. G. C. and Bisson M. (1979). Sequential
extraction of particulate trace metals. Anal. Chem.
51
, 844-
850.
Tingzong Guo R. D., DeLaune R. D. and Patrick Jr. W. H. (1997).
The influence of sediment redox chemistry on chemically
active forms of arsenic, cadmium, chromium, and zinc in es-
tuarine sediment. Environ. Int.
23
, 305-316.
Villar C., Tudino M., Bonetto C., de Cabo L., Stripeikis J.,
d’Huicque L. and Troccoli O. (1998). Heavy metal concen-
trations in the lower Paraná river and right margin of the
Río de la Plata estuary. Verh. Int. Verein. Limnol.
26
, 963-
966.
logo_pie_uaemex.mx