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Impact of acid mine drainage on the hydrogeochemical characteristics of the Tinto-Odiel Estuary (SW Spain)/ Impacto del drenaje acido de mina en las caracteristicas hidrogeoquimicas del estuario de los rios Tinto y Odiel (SO Espana).

1. Introduction

Typically, the hydrochemical characteristics of estuary systems are defined by the mixing processes between masses of fresh water of fluvial origin and masses of salt water coming from the sea.

The hydrochemical markers of salinity and chlorinity concentrations (dissolved [Cl.sup.-]), more often used to define zones of mixtures in these types of systems, to identify the degree of evolution of the salt-induced process between both masses of water.

The longitudinal variations of these indicators best characterize the intensity of the mixing process, as well as the behaviour of numerous elements such as nutrients, heavy metals, etc. dissolved in the system (Salomon and Fostner, 1984; Seigel, 2002), and changes in environmental conditions.

Inside the mouth of the Odiel and Tinto Rivers describe the typical salt-induced mixture process. Nevertheless, the peculiarity of this system rests in the character of the fluvial contributions received by both rivers from the drainage basins. The rivers are affected by acid mine drainage (AMD) and transmit to the system all the characteristics of these types of processes, e.g., acid waters (pH<3) with high heavy metal concentrations (Nelson and Lamothe, 1993; Sainz et al., 2004; Espana et al., 2005).

The discharge in an estuarine system of a mass of fluvial fresh water with acidic character confers special hydrochemical characteristics to the water produced by the convergence of these two processes. The combined salt-induced mixture and acid neutralization will interfere specially with the behaviour of heavy metals and nutrients that are dissolved in the estuary.

The objective of this work is to determine the hydrochemical characteristics of an estuary affected by AMD by studying the seasonal behaviour and longitudinal distribution of the processes of acid and salt-induced mixing.

1.1. Regional Setting

Ria of Huelva is an estuarine system located in the northwest of the Gulf of Cadiz constituted by the mouths of the Tinto and Odiel rivers. This estuary has a strong tidal influence that controls the salt-induced mixture processes of masses of water. The tidal wave moves along the estuary following a hypersinchronic model with an average tidal range of 2.30 m, ranging between 1.63 m during a mean neap tide and 2.90 m in a mean spring tide (Borrego et al., 1995).

Fluvial discharge in the estuary is markedly seasonal and with a great inter-annual irregularity. Usually, the average flow of both rivers is 49 [hm.sup.3]/month during wet periods (October to March), and less than 5 [hm.sup.3]/month during the driest months (may to September) (Borrego, 1992). Climate at this latitude is characterized as having a short and warm winter, when most annual rains take place, and warm and dry summers (Canovas et al, 2007). During dry years (rainfall < 400 mm x [y.sup.-1]), the average annual discharge of the Tinto river is 5.5 x [10.sup.6] [m.sup.3] x [y.sup.-1] and 79 x [10.sup.6] [m.sup.3] x [y.sup.-1] for the Odiel river, while in wet years (rainfall > 1200 mm x [y.sup.-1]), the average values are 99 x [10.sup.6] [m.sup.3] x [y.sup.-1] for the Tinto river and 1670 x [10.sup.6] [m.sup.3] x [y.sup.-1] for the Odiel river (Sainz et al., 2004; in Lopez-Gonzalez, 2009).

The fluvial basin of these rivers lies, to a great extent, over Paleozoic materials and, more specifically, on formations of the so-called volcano-sedimentary complex, where some of the most important sulfide mineralized masses in Europe can be found. These ore deposits have been mined since at least 4500 B.P. (Leblanc et al., 2000). The natural alteration of these sulfide masses, together with the mining activity, has caused the secular pollution of the Tinto and Odiel Rivers, whose waters have high concentrations of heavy metals and extremely low (less than 3) pH values (Grande et al., 2000).

Furthermore, since 1966, fertilizer factories, copper foundries, paper mills, as well as phosphogypsum deposits and plants for cleaning aggregates have been established along the margins of the Tinto and Odiel estuaries (Fig. 1). This industrial activity produces a large volume of effluents, such as phosphogypsum deposits, which find their way into the waters of the estuary and contribute to the already large quantities of heavy metals and nutrients that make this estuarine system one of the most polluted in Western Europe (Ruiz et al., 1998; Grande et al., 2000; Borrego et al., 2002).


2. Materials and methods

To study this system, ten sampling stations have been distributed among this system: in the main channel, called Padre Santo Channel (C1, C2 and C3 stations), in the Odiel River estuary (O1, O2, O3 and O4 stations), and in the Tinto River estuary (T1, T2 and T3 stations) (Figure 1). Seven bi-monthly cruises were made from the years 2003 to 2004 to collect superficial water samples and to measure in situ the pH and conductivity values in the control stations. Water samples were collected in 1000 ml polypropylene bottles and filtered through Millipore membrane filters (0.45 pm pore size; 47 mm diameter). Thus, suspended matter samples (with size of particles superior to 0.45 pm) and filtered water samples were obtained. The latter were acidified to pH 2 with Merck supra pure HN[O.sub.3] and kept cool until analysis. The suspended matter samples were kept in filters; from each sample, 0.2 g of material was taken and subjected to a triacid attack for total extraction (HF-HCl-HN[O.sub.3]).

Chemical analysis of the suspended matter samples and filtered water samples were made following the established protocol for these types of samples in the laboratories of the R&D Central Services of the University of Huelva. The concentration of cations was measured by optical emission spectroscopy of the plasma source connected by induction (ICP-MS, HP4500). External calibration was made with the multielemental solution SPEX 1, including periodically a control solution of 10 [micro]g x [L.sup.-1] during the analysis. The detection limit was close to 0.01 [micro]g x [L.sup.-1], with a precision greater than 5% RSD for all determinations.

The concentration of anions in the filtered water samples were determined by ion chromatography using a DIONEX DX120 machine fitted with an AS9-HC of 4x250 mm column (IonPac) and an ASRS ULTRAII suppressing membrane of 4 mm.

3. Results

The results obtained of the analyses are shown in the table 1 and are represented in the figures 2 and 3.

During the period of study, the pH values ranged from 2.7 to 8.2, showing high gradients in the mixture zones of both rivers (where pH varied between 3 and 7) (Table 1). On the contrary, the pH values in the Padre Santo Channel showed few variations, oscillating between 6.8 and 8.2 (Table 1).


In the mixing zone of the Tinto and Odiel Rivers, greater gradients in chlorinity were observed during winter, spring and autumn, in which the concentrations of dissolved [Cl.sup.-] oscillate between 0.02 and 16 g x [L.sup.-1]. Nevertheless at ebb tides, chlorinity values were uniform in all sampling stations distributed along the estuary, and these were higher than 12 g x [L.sup.-1] (Table 1). In summer, the temperature easily rises above 39[degrees]C in the upper estuary zone, inducing intense evaporation of water (Borrego et al, 1995). Thus, greater chlorinity values can be observed in this sector than in the marine sector (Padre Santo Channel) where temperatures are smoothed.


4. Discussion

4.1. pH and Chlorinity of the Water

The most outstanding characteristic of the water in Ria of Huelva is the longitudinal variation of the pH values, which can be attributed to the mixing of acid water contributions from the Tinto and Odiel Rivers and the marine water introduced by the tide (Borrego et al., 2004).

The largest longitudinal variations in the pH values were observed during winter, spring and autumn, when the fluvial inputs were greater. Whereas during summer, the pH of the estuary was more uniform, with values higher than 6.5 in most of the stations, except for the O-4 and T-3 stations where the tidal influence was minor and the pH values were lower than 4 (Table 1). In this case, the low volume of fluvial contributions in summer allowed fast neutralizations of the acid water in the upper sector of the mixing zone of both rivers. It is necessary to point out that during periods of strong and abundant rains at the source of the Odiel and Tinto Rivers, the acid water inputs that reached the estuary gave rise to pH values lower than 7 in the Padre Santo Channel, as it happened in the autumn cruise of year 2003.

4.2. Relationship of pH Values to [Cl.sup.-], [Na.sup.+], [K.sup.+], [Mg.sup.2+], [Ca.sup.2+] and S[O.sub.4.sup.=] concentrations

As for the relationship between pH values and [Cl.sup.-] and [Na.sup.+] concentrations dissolved in water (characteristic marine water elements), it was observed that when pH values were lower than 4.5, the concentrations of [Cl.sup.-] and Na+ did not exceed 4 and 1 mg x [L.sup.-1], respectively. Neither did these elements show a direct relation with pH of water (Figure 2a-b). These behaviours indicate that, during the first stages of neutralization of acid water, pH did not respond to an increase in the volume of seawater in the mixture and therefore was not related with the salt-induced mixture process. Likewise, the concentrations of [Ca.sup.2+], [K.sup.+] and [Mg.sup.2+] dissolved in water did not display any response related to this increase of pH (Figure 2c-d-e), one reason why the neutralization of the fluvial water could not be related to the weathering of carbonates or aluminium silicates phases. Nevertheless, for equal range of acidity in estuarine water, an inverse relation of pH with the dissolved S[O.sub.4.sup.=] concentration was observed (Figure 2f). This progressive loss of dissolved S[O.sub.4.sup.=] took place via the precipitation of sulphated salts in the upper inter-tidal zones of the estuary (Borrego et al., 1995; Carro et al., 2006) (Figure 4).

At an advanced stage in the process of acid water neutralization inside the estuary (sectors with pH values between 4.5 and 6.5), a direct linear relation of pH with concentrations of dissolved [Cl.sup.-], [Na.sup.+], [Mg.sup.2+], [Ca.sup.2+], [K.sup.+] and S[O.sub.4.sup.=] was observed. It is shown that the increase of pH in this sector was directly related to a process of dilution between the acid water coming from fluvial discharge and the marine water introduced by the tide in the system. These neutralization processes took place in the mixture zones of the Odiel and Tinto Rivers, between the sampling stations of O-1 and O-4, and T1 and T-3, respectively (Table 1).

Finally, when pH values in the system reached between 6.5 and 8, [Cl.sup.-] and concentrations of [Na.sup.+] and S[O.sub.4.sup.=] dissolved did not show any relation to pH and maintained relatively constant values in each sampling. Nevertheless, a significant variation in the concentrations of these elements dissolved in water was observed during the seven sampling cruises that were made. This increase of pH where values next to neutrality were reached did not seem to have a direct relation with the increase of the concentrations of dissolved [Cl.sup.-], [Na.sup.+] and S[O.sub.4.sup.=]. This same effect has been observed in previous work (Carro et al., 2006) and has been interpreted as the result of the mixing of estuarine water with water with greater concentrations of dissolved salt (respect to fluvial water) and with pH values near neutrality and slightly basic marine water. This mixing process was limited to the sector of the Padre Santo Channel where these levels of pH were reached.


4.3. Relationship of pH Values to [Cu.sup.2+] and [Zn.sup.2+] in the Water and in Particulate Suspended Matter (SPM)

Concentrations of dissolved [Cu.sup.2+] and [Zn.sup.2+] in the water of this estuary showed a decrease in pH of less than 4.5 (Figure 3a-c) not associated with the transference processes from the dissolved phase to the particulate one (SPM) since the concentrations of both metals in the SPM remained constant at this pH level. As explained previously, this removal of metals cannot be associated with the salt-induced mixture processes because it has a different level of pH values. However, it can be associated with decrease of dissolved S[O.sub.4.sup.=] produced by the precipitation of sulphated salts by intense evaporation in the upper inter-tidal zones, because these salts work like a temporary warehouse of metals and atoms of hydrogen (acidity) (Canovas et al, 2007).

In the acidity interval ranging from 4.5 and 7, concentrations of [Cu.sup.2+] and [Zn.sup.2+] in the dissolved phase also improved by a significant removal, wherein [Cu.sup.2+] concentrations decreased from greater than 2000 [micro]g x [L.sup.-1] to concentrations lower than 550 [micro]g x [L.sup.-1]. Concentrations of [Zn.sup.2+] went from 4000 [micro]g x [L.sup.-1] to 1500 [micro]g x [L.sup.-1]. In these cases, the removal of these metals in the dissolved phase can be explained by the coexistence of two processes. The first is a removal associated with a mixture process brought about by acid water dilution with tidal water (indicated by the reduction of [Na.sup.+] and [Cl.sup.-] and an increase of pH). The second is by transfer of a fraction of [Cu.sup.2+] and [Zn.sup.2+] dissolved in water towards the SPM by sorption or coagulation (Turner and Millward, 2002; Braungardt et al., 2003), since under this pH level, an important increase in the concentration of these metals in this phase was observed (Figure 3b-d).

4.4. Hydrochemical Zonation

Based on the mixture processes that occur in the estuary of Ria of Huelva, we have mapped out a hydrochemical zonation in the system.

Zone 1. In this sector, pH increases from the most typical acid values of acid fluvial water (from 2.4 to 3) to pH values of 4.5. The chlorinity does not rise above 3 g x [L.sup.-1], keeping relatively constant values during each one of the cruises. The same behaviour has been observed in the concentrations of dissolved Na+, which in this zone does not exceed 2 g x [L.sup.-1]. Concentration of dissolved S displays an inverse relation with the values of pH, reaching values lower than 0.2 g x [L.sup.-1] with lower pH values. One of the main characteristics of acid water derived from sulphide oxidation is the greater concentration of dissolved metals and sulphates in its composition. The process of neutralization of this water in the absence of salt-induced mixing gives rise to the precipitation of sulphates and therefore a fast removal of dissolved S[O.sub.4.sup.=] and [Cu.sup.2+]. The precipitated sulphates scavenge an important fraction of the concentration of some heavy metals transported by water in the dissolved phase ([Cu.sup.2+], [Zn.sup.2+], for example), since these sulphated salts are a temporary warehouse of heavy metals and atoms of hydrogen (acidity). Together with this process could be oxidation of [Fe.sup.2+] to [Fe.sup.3+], which generates water and consumes acidity with the following reaction (Younger et al, 2002):

4 [F.sup.2+] + [O.sub.2] + 4[H.sup.+] [right arrow] 4[Fe.sup.3+] + 2 [H.sub.2]O

The [Fe.sup.3+] released could react with any other element and precipitate in the form of colloid, so that no hydrogenions would be released since the following reaction would be interrupted:

4 [Fe.sup.2+] + 8[H.sub.2]O + 4Fe(OH) + 12[H.sup.+]

On the other hand, the existence of an anoxic environment in the river channel could also account for the lack of acidity generation.

Neutralization by mixing of water masses is not related to the weathering of carbonates or aluminium silicates in their mineral phases, as charts indicate the absence of any relation in the concentration of elements such as dissolved [Ca.sup.2+], [Na.sup.+], [Mg.sup.2+] or [K.sup.+] versus pH values. Neither does this process show an effect of the dilution of marine water with pH values greater than 7, since this would typically give rise to an increase in the concentration of dissolved marine elements such as [Cl.sup.-], [Na.sup.+], [Ca.sup.2+] and S[O.sub.4.sup.=].

Zone 2. This zone is limited to pH values ranging between 4.5 and 7.5, and chlorine concentration with values between 3 and 15 g x [L.sup.-1]. Both parameters have a lineal relation suggesting that neutralization in this sector is induced by the direct dilution of acid fluvial water and marine water with pH values greater than 7. The same behaviour that shows pH values and chlorinity also indicates that other dissolved elements that have been described, such as [Na.sup.+], [Ca.sup.2+], [K.sup.+], [Mg.sup.2+] and S[O.sub.4.sup.=], are contributed by dissolved salts in marine water.

During this mixing dilution, a noteworthy decrease in the concentrations of some dissolved heavy metals in fluvial water derived from acid mine drainage has been observed. This was the case of [Cu.sup.2+] and [Zn.sup.2+], which had lower concentrations in the dissolved phase, from 1500 to 600 [micro]g x [L.sup.-1] and, from 4000 to 1000 [micro]g x [L.sup.-1] respectively. Likewise, a part of these dissolved metals is absorbed as solid particles that compose the SPM and cause a progressive increase of the concentration of these metals in this phase. This process has been observed in laboratory of neutralization of waterproof (Achterberg et al., 2003; Espana et al., 2006).

Zone 3. In this zone, pH values range from 7.5 to 8.2, and average increase of the dissolved concentrations of [Cl.sup.-], [Na.sup.+] and S[O.sub.4.sup.=] occurs. In this sector, distribution of the concentration of heavy metals dissolved in water changes depending on chemical element. Whereas some elements such as dissolved Mn or [Zn.sup.2+] experience a strong loss in concentration because of the dilution of estuarine water with water derived from the open sea, other elements such as dissolved [Cu.sup.2+] or U increase in concentration. This event is caused by the remineralisation produced by saline shock, wherein a part of the concentration of the chemical element in its particulate phase is re-dissolved and transferred to the dissolved phase.

Spatial location and extent of these zones within the estuarine system are affected by seasonal variations depending on volume of fluvial discharge (Figure 4). Therefore, in dry season, there is a shift upstream of these areas, reducing considerably the area of Zone 1 and expanding Zone 3 (Figure 4b), while in periods with great fluvial discharge, there is an opposite effect (Figure 4a).

5. Conclusions

The hydrogeochemical characteristics of the water in an estuary where acid fluvial water and marine water are mixed allow us to define the intervention of two geochemical processes: a typical process of salt-induced mixing and a process of neutralization of acid water derived from AMD. The product of the convergence of these mixture processes will not only affect the behaviours of heavy metals and nutrients that form the system. It allows us to make a hydrochemical zonation of the estuary. The definition of these zones depends on the behaviour of pH values and chlorinity concentration of the water, as well as on the heavy metal concentrations in their dissolved and particulate phases.

The three zones are:

Zone 1. Sector with pH values that increase from 2.4 to 4.5, where chlorinity concentration of the water does not rise above 3 g x [L.sup.-1]. In this zone, starting the neutralization process produces the precipitation of particulate sulphates, which scavenge an important fraction of the metal concentration that is transported in a dissolved phase by the acid water.

Zone 2. In this zone, pH and chlorinity have a direct relation (fluctuating from 4.5 to 7.5 and from 3 to 15 g x [L.sup.-1], respectively). This indicates that the neutralization process is induced by the dilution of the water derived from Zone 1 with salt water, which introduces dissolved elements (typically marine) into the mixture.

Zone 3. This zone is characterized by slightly basic pH water, where the salt-induced mixture process typical of estuarine systems takes place and some dissolved elements such as [Cu.sup.2+] or U increase in concentration due to the remineralisation produced by saline shock.

doi: 10.5209/


Financial support for this research provided by DGCI-CYT National Plan, project REN2002-03979 and CTM2006-08298, Andalusian Regional Government (PAI- Group RNM-276), and the MECD of the Spanish Government by a FPU grant.

The Editorial Office of Journal of Iberian Geology aknowledges the reviews by two anonymous referees.


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B. Carro (1), J. Borrego (1), N. Lopez-Gonzalez (1), J.A. Grande (2) *, T. Gomez (2), M.L. de la Torre (2). T. Valente (3)

(1) Departamento de Geologia, Universidad de Huelva, Campus El Carmen, Facultad de Ciencias Experimentales, 21071 Huelva. Spain.

(2) Departamento de Ingenieria Minera, Mecanica y Energetica. Grupo de Geologia Costera y Recursos Hidricos. Escuela Tecnica Superior de Ingenieria. Universidad de Huelva. Ctra. Palos Fra. s/n. 21819. Palos de la Frontera. Huelva. Spain.

(3) Centro de Investigacao Geologica, Ordenamento e Valorizacao, Recursos (CIG-R)--Universidade do Minho, Campus de Gualtar, 4710-057Braga, Portugal

* Corresponding author: Tel.: +34 959217346; Fax: +34 959 217304; E-mail:

Received: 14/08/10 / Accepted: 01/03/11
Table 1.-pH, Cl-(g.[L.sup.-1]), [Cu.sup.2+], [Zn.sup.2+], [Ca.sup.2+],
[K.sup.+], [Mg.sup.2+], [Na.sup.+] and S[O.sub.4.sup.=] (mg.[L.sup.-1])
in water samples of Odiel-Tinto Rivers Estuary.

Tabla 1.-Valores de pH y concentracion de Cl-(g.[L.sup.-1]),
[Cu.sup.2+], [Zn.sup.2+], [Ca.sup.2+], [K.sup.+], [Mg.sup.2+],
[Na.sup.+] and S[O.sub.4.sup.=] (mg.[L.sup.-1]) en las muestras de agua
del estuario de los rios Tinto y Odiel.

                                         Cl-           [Cu.sup.2+]
Cruise              Station   pH    (g.[L.sup.-1])   (mg.[L.sup.-1])

Winter 2003           C1      7.9        14.5              0.5
Winter 2003           C2      7.7        11.6              0.5
Winter 2003           C3      7.2        12.8              0.6
Winter 2003           O1      7.3        9.4               0.6
Winter 2003           O2      5.7        5.7               0.8
Winter 2003           O3      4.7        2.5               2.1
Winter 2003           O4      4.2        1.3               3.2
Winter 2003           T1      6.4         12               1.2
Winter 2003           T2      6.2        10.4              1.3
Winter 2003           T3      3.0        1.4               9.8
Spring 2003           C1      8.1        13.6              1.1
Spring 2003           C2       8         12.8              1.3
Spring 2003           C3      7.9        9.4               0.8
Spring 2003           O1      8.1        12.4              0.8
Spring 2003           O2      7.2        10.1              0.7
Spring 2003           O3      4.5        0.2               1.9
Spring 2003           O4       4         0.03              2.4
Spring 2003           T1      7.4        8.6               0.8
Spring 2003           T2      6.8        9.2               0.8
Spring 2003           T3      3.0        0.1              12.6
early summer 2003     C1       8         16.4              0.7
early summer 2003     C2       8          16               0.7
early summer 2003     C3      7.9        12.1              0.9
early summer 2003     O1      7.8        15.2              1.4
early summer 2003     O2      7.8        15.3              1.1
early summer 2003     O3      7.7        12.9              1.7
early summer 2003     O4      3.4        0.05              2.8
early summer 2003     T1      7.9        15.2              1.8
early summer 2003     T2      7.9        14.8               2
early summer 2003     T3      2.7        0.9               7.3
later summer 2003     C1      8.3        14.9              2.2
later summer 2003     C2      8.2        20.5              2.2
later summer 2003     C3       8         16.8              2.5
later summer 2003     O1      8.1         19               1.8
later summer 2003     O2      7.9        20.3              1.8
later summer 2003     O3      7.6        20.6              1.9
later summer 2003     O4      3.5        1.1               12
later summer 2003     T1      7.9        17.1              1.6
later summer 2003     T2      7.7        15.4              1.7
later summer 2003     T3      4.3        1.1               11
Fall 2003             C1      7.4        15.3              1.5
Fall 2003             C2      6.9        13.7              1.3
Fall 2003             C3      6.8        14.2              1.4
Fall 2003             O1       6         8.6               0.9
Fall 2003             O2      5.7        6.9               1.1
Fall 2003             O3      4.2        0.2               11
Fall 2003             O4      3.6        0.05              20
Fall 2003             T1      6.3        13.1              0.9
Fall 2003             T2      6.5         13               1.1
Fall 2003             T3      2.7        0.1              26.6
Winter 2004           C1      8.2        19.8              1.1
Winter 2004           C2      8.1        15.8              0.9
Winter 2004           C3      8.1         16               0.8
Winter 2004           O1       8         18.9              0.8
Winter 2004           O2      5.3        7.8               1.2
Winter 2004           O3      4.8        0.1               5.5
Winter 2004           O4      3.7        0.1              13.5
Winter 2004           T1      7.6        14.1              0.9
Winter 2004           T2      nd          nd               nd
Winter 2004           T3      3.3                         43.3
Spring 2004           C1      7.7        19.7              17
Spring 2004           C2      7.9        14.5              1.3
Spring 2004           C3      7.7        15.1              10
Spring 2004           O1       8         12.7              0.9
Spring 2004           O2      5.9        12.6               1
Spring 2004           O3      3.7        2.8                8
Spring 2004           O4      2.9        1.4               16
Spring 2004           T1      7.8        13.8               1
Spring 2004           T2      7.3        10.3              0.7
Spring 2004           T3      3.1        1.4               37

                                [Zn.sup.2+]       [Ca.sup.2+]
Cruise              Station   (mg.[L.sup.-1])   (mg.[L.sup.-1])

Winter 2003           C1            0.2               405
Winter 2003           C2            0.3               313
Winter 2003           C3            0.5               364
Winter 2003           O1            0.3               246
Winter 2003           O2            0.9               158
Winter 2003           O3            3.2              85.4
Winter 2003           O4            6.5              31.6
Winter 2003           T1             1                354
Winter 2003           T2            1.2               310
Winter 2003           T3            23               66.6
Spring 2003           C1            0.1               329
Spring 2003           C2            0.2               398
Spring 2003           C3            0.2               254
Spring 2003           O1            0.1               294
Spring 2003           O2            0.5               238
Spring 2003           O3            3.9              33.5
Spring 2003           O4            5.3              26.3
Spring 2003           T1            0.3               317
Spring 2003           T2            0.5               265
Spring 2003           T3           10.7              39.7
early summer 2003     C1           0.05               413
early summer 2003     C2            0.1               400
early summer 2003     C3            0.1               416
early summer 2003     O1            0.4               414
early summer 2003     O2            0.3               318
early summer 2003     O3            1.4               381
early summer 2003     O4            5.9              49.6
early summer 2003     T1            0.4               422
early summer 2003     T2            0.2               411
early summer 2003     T3             9                149
later summer 2003     C1            0.1               458
later summer 2003     C2            0.1               454
later summer 2003     C3            0.1               439
later summer 2003     O1            0.1               459
later summer 2003     O2            0.2               448
later summer 2003     O3            0.5               543
later summer 2003     O4           35.5              50.2
later summer 2003     T1            0.1               450
later summer 2003     T2            0.2               513
later summer 2003     T3            4.7               252
Fall 2003             C1             1                374
Fall 2003             C2             1                359
Fall 2003             C3            1.5               352
Fall 2003             O1            2.6               251
Fall 2003             O2            3.6               203
Fall 2003             O3            27               34.1
Fall 2003             O4            49               24.9
Fall 2003             T1            1.8               295
Fall 2003             T2            2.3               381
Fall 2003             T3           65.6               300
Winter 2004           C1            0.1               339
Winter 2004           C2            0.2               290
Winter 2004           C3            0.2               313
Winter 2004           O1            0.2               325
Winter 2004           O2             3                206
Winter 2004           O3            4.2              43.2
Winter 2004           O4           35.1              38.7
Winter 2004           T1            0.4               366
Winter 2004           T2            nd                nd
Winter 2004           T3           53.9              88.6
Spring 2004           C1            0.2               435
Spring 2004           C2            0.3               331
Spring 2004           C3            0.4               347
Spring 2004           O1            0.3               294
Spring 2004           O2            0.5               298
Spring 2004           O3           17.1              58.4
Spring 2004           O4           36.9              39.7
Spring 2004           T1            0.5               320
Spring 2004           T2            0.9               247
Spring 2004           T3           41.4              90.4

                                 [K.sup.+]        [Mg.sup.2+]
Cruise              Station   (mg.[L.sup.-1])   (mg.[L.sup.-1])

Winter 2003           C1            951              1139
Winter 2003           C2            792               863
Winter 2003           C3            838              1014
Winter 2003           O1            658               710
Winter 2003           O2            427               429
Winter 2003           O3            152               196
Winter 2003           O4            2.3              36.2
Winter 2003           T1            803               992
Winter 2003           T2            738               852
Winter 2003           T3           10.1              66.6
Spring 2003           C1            547               954
Spring 2003           C2            656              1145
Spring 2003           C3            402               724
Spring 2003           O1            469               850
Spring 2003           O2            360               686
Spring 2003           O3           94.2              37.5
Spring 2003           O4            0.9              29.8
Spring 2003           T1            457               842
Spring 2003           T2            379               680
Spring 2003           T3            0.9              44.5
early summer 2003     C1            692              1209
early summer 2003     C2            660              1158
early summer 2003     C3            682              1220
early summer 2003     O1            677              1196
early summer 2003     O2            506               930
early summer 2003     O3            595              1094
early summer 2003     O4            0.9              69.5
early summer 2003     T1            709              1251
early summer 2003     T2            681              1226
early summer 2003     T3            108               149
later summer 2003     C1           1725              1241
later summer 2003     C2           1717              1239
later summer 2003     C3           1645              1216
later summer 2003     O1           1492               632
later summer 2003     O2           1469               618
later summer 2003     O3           1576               649
later summer 2003     O4            7.2              53.2
later summer 2003     T1           1452               629
later summer 2003     T2           1569               649
later summer 2003     T3           95.5               102
Fall 2003             C1           1399              1080
Fall 2003             C2           1296              1022
Fall 2003             C3           1223               977
Fall 2003             O1            751               489
Fall 2003             O2            609               416
Fall 2003             O3           12.2              45.8
Fall 2003             O4            5.2              39.5
Fall 2003             T1            909               535
Fall 2003             T2           1003               581
Fall 2003             T3           44.8               149
Winter 2004           C1            619              1084
Winter 2004           C2            569               924
Winter 2004           C3            561               997
Winter 2004           O1            583              1050
Winter 2004           O2            316               570
Winter 2004           O3            6.7              57.6
Winter 2004           O4            3.7              48.4
Winter 2004           T1            668              1189
Winter 2004           T2            nd                nd
Winter 2004           T3           11.6              68.8
Spring 2004           C1           2136              1264
Spring 2004           C2           1372               945
Spring 2004           C3           1503               995
Spring 2004           O1           1122               826
Spring 2004           O2           1184               849
Spring 2004           O3           64.2               133
Spring 2004           O4            4.6              62.3
Spring 2004           T1           1220               901
Spring 2004           T2            799               680
Spring 2004           T3            7.5              62.5

                                [Na.sup.+]       S[O.sub.4.sub.=]
Cruise              Station   (mg.[L.sup.-1])   (mg.[L.sup.-1])

Winter 2003           C1           9284               867
Winter 2003           C2           7273               758
Winter 2003           C3           8133               768
Winter 2003           O1           5748               640
Winter 2003           O2           3104               416
Winter 2003           O3            850               249
Winter 2003           O4            13                128
Winter 2003           T1           7526               753
Winter 2003           T2           6412               669
Winter 2003           T3            83                320
Spring 2003           C1           7772               741
Spring 2003           C2           8766               805
Spring 2003           C3           5905               643
Spring 2003           O1           6459               647
Spring 2003           O2           4724               509
Spring 2003           O3           67.2               105
Spring 2003           O4           35.2               108
Spring 2003           T1           6553               620
Spring 2003           T2           5018               525
Spring 2003           T3           43.8               204
early summer 2003     C1           9429               848
early summer 2003     C2           9001               805
early summer 2003     C3           9399               849
early summer 2003     O1           9166               812
early summer 2003     O2           7006               829
early summer 2003     O3           8185               804
early summer 2003     O4             3                221
early summer 2003     T1           9626               888
early summer 2003     T2           9059               869
early summer 2003     T3            336               444
later summer 2003     C1           13065             1053
later summer 2003     C2           12525             1069
later summer 2003     C3           12437             1045
later summer 2003     O1           10866              946
later summer 2003     O2           11225              983
later summer 2003     O3           12757             1059
later summer 2003     O4           122.3              197
later summer 2003     T1           11167              908
later summer 2003     T2           11753             1013
later summer 2003     T3            453               178
Fall 2003             C1           10699              980
Fall 2003             C2           9914               913
Fall 2003             C3           10017              890
Fall 2003             O1           5790               666
Fall 2003             O2           4546               595
Fall 2003             O3            164               153
Fall 2003             O4            117               163
Fall 2003             T1           7299               746
Fall 2003             T2           9835               921
Fall 2003             T3            325               663
Winter 2004           C1           11001              923
Winter 2004           C2           10619              962
Winter 2004           C3           9820               920
Winter 2004           O1           9989               841
Winter 2004           O2           5058               555
Winter 2004           O3            60                155
Winter 2004           O4           20.1               134
Winter 2004           T1           11252              943
Winter 2004           T2            nd                nd
Winter 2004           T3            123               271
Spring 2004           C1           12953             1072
Spring 2004           C2           9287               810
Spring 2004           C3           9745               830
Spring 2004           O1           8024               733
Spring 2004           O2           7979               685
Spring 2004           O3           1095               274
Spring 2004           O4           84.6               190
Spring 2004           T1           8820               793
Spring 2004           T2           6350               654
Spring 2004           T3            90                273
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Article Details
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Author:Carro, B.; Borrego, J.; Lopez-Gonzalez, N.; Grande, J.A.; Gomez, T.; de la Torre, M.L.; Valente, T.
Publication:Journal of Iberian Geology
Article Type:Report
Date:Jan 1, 2011
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