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).
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).
[FIGURE 1 OMITTED]
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.
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).
[FIGURE 2 OMITTED]
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.
[FIGURE 3 OMITTED]
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.
[FIGURE 4 OMITTED]
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).
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.
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.
Achterberg, E.P., Herzl, VM.C., Braungardt, C.B., Millward, G.E. (2003): Metal behaviour in an estuary polluted by acid mine drainage: the role of particulate matter. Environmental Pollution, 121: 283-292. doi: 10.1016/S02697491(02)00216-6.
Borrego, J. (1992): Sedimentologia del estuario del rio Odiel (Huelva, S.O. Espana). Ph.D. Thesis, University of Sevilla, 296 pBorrego, J., Morales, J.A., Pendon, J.G. (1995): Holocene estuarine facies along the mesotidal coast of Huelva, southwestern Spain. In: Flemming, B.W., Bartholoma, A. (Eds.). Tidal Signatures in Modern and Ancient Sediments. International Association of Sedimentologists, Special Publication 24: 151-170.
Borrego, J., Morales, J.A., de la Torre, M.L., Grande, J.A. (2002): Geochemical characteristics of heavy metal pollution in surface sediments of the Tinto and Odiel river estuary (southwestern Spain). Environmental Geology, 41: 785-96. doi: 10.1007/s00254-001-0445-3.
Borrego, J., Lopez-Gonzalez, N., Carro, B., Lozano-Soria, O. (2004): Origin of the anomalies in Light and middle REE in sediments of an estuary affected by phosphogypsum wastes (southwestern Spain). Marine Pollution Bulletin, 49: 1045-1053. doi: 10.1016/j.marpolbul.2004.07.009.
Braungardt, C.B., Achterberg, E.P., Elbaz-Poulichet, F., Morley, N.H. (2003): Metal geochemistry in a mine-polluted estuarine system in Spain. Applied Geochemistry, 18: 1757-1771. doi: 10.1016/S0883-2927(03)00079-9.
Canovas, C.R., Olias, M., Nieto, J.M., Sarmiento, A.M., Ceron, J.C. (2007): Hydrogeochemical characteristics of the Tinto and Odiel rivers (SW Spain). Factors controlling metal contents. Science of the Total Environment, 373: 363-382. doi: 10.1016/j.scitotenv.2006.11.022.
Carro, B., Borrego, J., Lopez-Gonzalez, N., Lozano-Soria, O. (2006): Transferencia de Tierras Raras entre la fase disuelta y la particulada en el agua de un estuario afectado por drenaje acido (SO de Espana). Geogaceta, 39: 111-114.
Elbaz-Poulichet, F., Morley, N.H., Cruzado, A., Velasquez, Z., Achterberg, E.P., Braungardt, C.B. (1999): Trace metal and nutrient distribution in an extremely low pH (2.5) river-estuarine system the Ria de Huelva (southwest Spain). Science of the Total Environment, 227: 73-83. doi: 10.1016/S0048-9697(99)00006-6.
Espana, J.S., Pamo, E.L., Santofimia, E., Aduvire, O., Reyes, J., Barettino, D. (2005): Acid mine drainage in the Iberian Pyrite Belt (Odiel river watershed Huelva SW Spain): Geochemistry mineralogy and environmental implications. Applied Geochemistry, 20: 1320-1356. doi: 10.1016/j.apgeochem.2005.01.011.
Espana, J.S., Pamo Lopez, E., Santofimia, E., Reyes, J., Matin, J.A. (2006): The removal of dissolved metals by hydroxysulphate precipitates during oxidation and neutralizations of acid mine waters Iberian Pyrite Belt. Aquatic Geochemistry, 12: 269-298. doi: 10.1007/s10498-005-6246-7.
Grande, J.A., Borrego, J., Morales J.A. (2000): A study of heavy metal pollution in the Tinto-Odiel estuary in southwestern Spain using factor analysis. Environmental Geology, 39: 1095-1101. doi: 10.1007/s002549900080.
Leblanc, M., Morales, J.A., Borrego, J., Elbaz-Poulichet, E. (2000): 4500-Year-Old mining pollution in southwestern Spain: long-term implications for modern mining pollution. Economic Geology, 95: 655-662.
Lopez-Gonzalez, N. (2009): Estudios de marcadores ambientales sedimentarios y geoquimicos en los sedimentos del estuario de los rios Tinto y Odiel. Ph.D. Thesis, University of Huelva, 153 p.
Nelson, C.H., Lamothe, P.J. (1993): Heavy metal anomalies in the Tinto and Odiel river and estuary system Spain. Estuaries, 16: 496-511. doi: 10.1007/BF02718297.
Ruiz, F., Gonzalez-Regalado, M.L., Borrego, J., Morales, J.A., Pendon, J.G., Munoz, J.M. (1998): Stratigraphic sequence elemental concentrations and heavy metal pollution in Holocene sediments from the Tinto-Odiel estuary southwestern Spain. Environmental Geology, 34: 270-278. doi: 10.1007/s002540050278.
Sainz, A., Grande, J.A., de la Torre, M.L. (2004): Characterisation of heavy metal discharge into the Ria of Huelva. Environment International, 30: 557-566. doi: 10.1016/j.en vint.2003.10.013.
Salomons, W., Forstner, U. (1984): Metals in the Hydrocycle. New York. Springer-Verlag.
Siegel, F.R. (2002): Environmental Geochemistry of Potentially Toxic Metals. Berling. Springer-Verlag 218 p.
Turner, A., Millward, G.E. (2002): Suspended Particles: Their role in Estuarine biogeochemical cycles. Estuarine Coastal and Shelf Science, 55: 857-883. doi: 10.1006/ ecss.2002.1033.
Younger, P., Banwart, S.A., Hedin, R.S. (2002): Mine Water. Hydrology pollution remediation. Kluwer Academic Publishers 442 p.
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: email@example.com
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