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Distribution of N 2 O has been determined in eight cruises along three transects (Guadalquivir, Sancti Petri and Trafalgar) in the Gulf of Cadiz, during 2014 and 2015. The mean N 2 O value for this area was 10.0 ± 0.9 nM, with large spatial and temporal variations. Stratification in the water column has been observed; the concentration of this gas increases with the depth, because of the presence of the Eastern North Atlantic Central Water (ENACW) and the Mediterranean Outflow Waters (MOW). The N 2 O production measured in this study is mainly due to nitrification. N 2 O yields from nitrification were estimated from the linear correlation of the excess of N 2 O (ΔN 2 O) with Apparent Oxygen Utilization (AOU) and nitrate (NO 3 − ), with values of their slopes ranged between 0.010 and 0.021% and 0.017–0.025% respectively. There is an onshore – offshore gradient of N 2 O; the highest values were found at the shallower stations, indicating coastal input and benthic remineralization. The seawater-air flux of N 2 O is affected by several variables (temperature, AOU and NO 3 − ), and the average flux calculated is 2.7 ± 2.0 μmol m − 2 d − 1 . The fluxes show a decrease with increasing distance from the coast, and with proximity to the Strait of Gibraltar. The study area behaves as a source of N 2 O to the atmosphere, with a global emission of 0.18 Gg year − 1 .

Chinese hamster ovary (CHO) cells are characterized by a low glucose catabolic efficiency, resulting in undesirable lactate production. Here, it is hypothesized that such low efficiency is determined by the transport of pyruvate into the mitochondria. The mitochondrial pyruvate carrier (MPC), responsible for introducing pyruvate into the mitochondria, is formed by two subunits, MPC1 and MPC2. Stable CHO cell lines, overexpressing the genes of both subunits, were constructed to facilitate the entry of pyruvate into the mitochondria and its incorporation into oxidative pathways. Significant overexpression of both genes, compared to the basal level of the control cells, was verified, and subcellular localization of both subunits in the mitochondria was confirmed. Kinetic evaluation of the best MPC overexpressing CHO cells showed a reduction of up to 50% in the overall yield of lactate production with respect to the control. An increase in specific growth rate and maximum viable cell concentration, as well as an increase of up to 40% on the maximum concentration of two recombinant model proteins transiently expressed (alkaline phosphatase or a monoclonal antibody), was also observed. Hybrid cybernetic modeling, that considered 89 reactions, 25 extracellular metabolites, and a network of 62 intracellular metabolites, explained that the best MPC overexpression case resulted in an increased metabolic flux across the mitochondrial membrane, activated a more balanced growth, and reduced the Warburg effect without compromising glucose consumption rate and maximum cell concentration. Overall, this study showed that transport of pyruvate into the mitochondria limits the efficiency of glucose oxidation, which can be overcome by a cell engineering approach.

Metal matrix composite (MMC) materials are increasingly used in industrial sectors such as energy, structural, aerospace, and automotive. This is due to the improvement of properties by the addition of reinforcements. Thus, it is possible to obtain properties of higher strength, better rigidity, controlled thermal expansion, and elevated wear resistance. However, due to the extreme hardness achieved during their manufacture, these composites pose a challenge to the conventional machining industry due to the rapid deterioration experienced by cutting tools. This article therefore proposes the use of an unconventional machining method that is becoming increasingly widely used: abrasive water jet cutting. This process is characterized by high production rates, absence of wear, and environmental friendliness, among other advantages. Experimental tests were carried out in order to analyze results that minimize the formation of defects in the machining of metal matrix composite consisting of aluminium matrix with silicon carbide (Al-SiC MMC). To this end, results were analyzed using Scanning Optical and Electron Microscope (SOM/SEM) techniques, the taper angle was calculated, and areas with different surface quality were detected by measuring the roughness.

The Mar Menor is a hypersaline coastal lagoon with salinity values ranging from 41.9 to 45.5. The system is subjected to a high anthropic pressure that causes an intense eutrophication process, followed by a recovery of the macrophyte meadows. This study focuses on the distribution of the main greenhouse gases (CO2, CH4 and N2O) and was carried out in the extreme seasonal conditions of winter and summer during the year 2018. Sediment-water-atmosphere exchanges and biochemical processes in the water column appeared to be the main factors to explain the variability of these gases. Dissolved Inorganic Carbon (DIC), CH4 and N2O benthic fluxes values obtained in this study, were of 91 ± 29 mmol m-2 d-1, 3.9 ± 1.9 μmol m-2 d-1 and -0.65 μmol m-2 d-1, respectively, along with an important seasonal variation observed, with an increase of DIC and CH4 benthic fluxes during the summer season. Mean values of partial pressure of CO2 (pCO2) in surface water were of 579 μatm in winter and 464 μatm in summer, therefore we can establish that the Mar Menor acts as a source of this gas emitting 3.3 ± 3.0 mmol CO2 m-2 d-1 to the atmosphere. In spite of this, the Mar Menor has a strong autotrophic behaviour partly due to the recovery of the macrophyte meadows, presenting an estimated NEP of 101 mmol m-2 d-1. Regarding to CH4, the mean fluxes to the atmosphere were of 8.0 ± 5.8 μmol m-2 d-1 and there was evidence of CH4 production in the water column that increased in summer. Last of all, in the case of N2O the system acts as a sink with values of -0.65 ± 0.5 μmol m-2 d-1, presenting an intake of N2O that is usually detected in pristine systems.

Tool wear is one of the main parameters employed for evaluating tool life, due to its influence in the loss of quality of the manufactured parts. So, minimising tool wear is possible to maximise tool life and to optimise the manufacturing performance. Different mechanisms can cause the tool wear in a specific machining process. Adhesion wear is one of the tool wear mechanisms that can be present in a wider range of cutting temperatures. This type of tool wear can be produced by two different ways. On the one hand, direct adhesion wear is caused by the incorporation of tool particles to the chips. On the other hand, secondary adhesion wear is caused by the incorporation of fragment of the workpiece material to the tool. This affects to the tool wear in two ways. First, tool geometry changes by the material incorporation. In a second place, when these fragments are removed, they can drag out tool particles causing tool wear. Indirect adhesion can be located in the tool edge, giving rise to the Built-Up Edge (BUE) and/or in the tool rake face giving rise to the Built-Up Layer (BUL). BUL and BUE formation and their evolutions affects to the workpiece quality. In this paper a study of the BUL and BUE formation mechanisms, their evolution and their influence on the dry turned aeronautical workpieces surface quality has been achieved. In particular, this study has been developed using aerospace aluminium alloys such as UNS A92024 (Al–Cu) and UNS A97050 (Al–Zn). Results have shown that BUE is formed by mechanical adhesion mechanism. On the other hand, BUL is initially formed by thermo-mechanical causes. However, a secondary BUL has been detected as a consequence of the extrusion process of the BUE. Changes in BUL and BUE have been related with the changes observed in the roughness profile of the machined pieces and evaluated through the average surface roughness, Ra. So, a first relationship between the adhesion effects and the surface finish of the worked samples has been found. Obtained results have confirmed that BUE changes the tool position angle giving rise to a reduction of Ra.

Four surveys (Jun’06 and Nov’06; Feb’07 and May’07) were carried out on the northeastern shelf of the Gulf of Cádiz (southwest Iberian Peninsula) to relate the spatio-temporal distribution of the carbon cycle parameters (dissolved inorganic carbon and dissolved organic carbon) to picophytoplankton biomass and community composition. In addition, the net ecosystem production and the picophytoplankton contribution to the air-sea CO2 exchange process were investigated. The results showed that chlorophyll-a, carbon cycle parameters and picophytoplankton composition showed large seasonality, and the Guadalquivir Estuary plays an important role in the contribution of nutrient and suspended particular material over the year. Regarding picophytoplankton composition, the flow cytometry analysis demonstrated that Prochlorococcus and Synechococcus were the main populations in the studied area and their temporal and spatial distributions were complementary: the Prochlorococcus population showed its maximum concentration in May’07 and Jun’06 and in the surface oceanic water, whereas the Synechococcus population was at its maximum during Feb’07 and Nov’06, and off the Guadalquivir Estuary and Bay of Cádiz. In addition, a relationship between the studied parameters and the fugacity of CO2 was also observed, suggesting that primary production is an important factor in the regulation of this parameter in the studied area. The calculated carbon budget showed that the area acts as a carbon sink on an annual basis. Se llevaron a cabo cuatro campañas oceanográficas (Jun’06 y Nov’06; Feb’07 y May’07) en la plataforma continental noreste del golfo de Cádiz (suroeste de la península Ibérica) para relacionar la distribución espacio-temporal de los parámetros del ciclo del carbono (carbono inorgánico disuelto y carbono orgánico disuelto) con la biomasa picofitoplanctónica y la composición de la comunidad. Además, se investigó la producción neta del ecosistema y la contribución del picofitoplancton al proceso de intercambio atmósfera-agua de CO2. Los resultados mostraron que la clorofila-a, los parámetros del ciclo del carbono y la composición del picofitoplancton presentaron una gran estacionalidad, jugando el estuario del Guadalquivir un papel importante en la contribución de nutrientes y material particulado en suspensión a lo largo del año. Los análisis de citometría demostraron que Prochlorococcus y Synechococcus fueron las principales poblaciones en el área de estudio y que su distribución espacial y temporal fue complementaria: Prochlorococcus presentó la máxima concentración en primavera y verano en aguas superficiales oceánicas, mientras que Synechococcus en invierno y otoño en aguas someras. Además, se observó una relación entre los parámetros estudiados y fugacidad de CO2, lo que sugiere que la producción primaria es un factor importante en la regulación de este parámetro en el área de estudio. El balance de carbono calculado indicó que el área actúa como sumidero de carbono a escala anual.

Four surveys (June and November 2006; February and May 2007) were carried out in the north eastern shelf of the Gulf of Cadiz (southwest Iberian Peninsula) to investigate the dynamics of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in a coastal area affected mainly by river input, but also by primary production/respiration, resuspension from the sediments, and mixing. In the period of the present study, DOC values ranged from 42 to 198 μM, while DON ranged from 0 to 20 μM. The seasonal variations showed high mean surface concentrations of DOC (106.2 ± 25.6 μM-C) and DON (8.6 ± 3.1 μM-N) in May, shifting to low DOC (89.1 ± 26.4 μM-C) and DON (4.2 ± 2.8 μM-N) in February. In spring, DOC and DON released by phytoplankton are likely to be the most significant source of organic matter. Low DOC and DON concentrations during winter are probably due to the uptake of DOC and DON by bacteria and to the strong mixing of the water column. The spatial variations showed the highest mean concentrations of dissolved organic matter (DOM) in the lower part of the Guadalquivir Estuary and the lowest mean concentrations of DOM in the bottom water of the oceanic zone. The very high mean DOC and DON concentrations measured off the Guadalquivir Estuary may be due to river input and/or re-suspension of the organic matter from the bottom sediments. The very low mean DOC and DON concentrations measured in the bottom water of the continental shelf may be due to mineralization and a surplus of more refractory organic carbon.

Sedimentary phosphorus was characterized in sediment cores from 3 coastal ecosystems of the Gulf of Cadiz. High spatial variability was observed in total phosphorus (from 445 to 20291 μg g.sed-1) and in the other phosphorus phases studied. This variability correlates with the proximity of the 10 sampling stations to sources of urban and/or industrial effluent in the zone. The benthic and diffusive fluxes were measured concurrently with sediment collection at these stations. The measured values of benthic fluxes range between –14 and 6 mmol m-2 d-1. Generally, stations that showed increased interstitial phosphate concentrations with increasing depth were characterized by positive values in phosphate benthic fluxes and by high percentages of reactive forms of sedimentary phosphorus. Negative benthic fluxes were associated with stations receiving more anthropogenic matter, which showed progressively decreasing phosphate concentrations in the interstitial water with depth. In these anthropogenic areas, the non-reactive forms of phosphorus (those associated with ferric oxyhydroxide and authigenic carbonate fluorapatite) are abundant, and reach values exceeding 75% of total phosphorus in sediment. Se ha realizado la caracterización del fósforo sedimentario en 3 ecosistemas costeros del Golfo de Cádiz. Se ha encontrado una alta variabilidad espacial (desde 445 hasta 20291 μg g.sed-1) en la cantidad de fósforo total, y en las otras fases de fósforo estudiadas. Esta variabilidad se correlaciona con la proximidad de las 10 estaciones de muestreo a las fuentes de efluentes urbanos e industriales de la zona. Los flujos difusivos y bentónicos fueron también medidos en las mismas estaciones de forma simultánea. Los valores de los flujos bentónicos están comprendidos entre –14 y 6 mmol m-2 d-1. Generalmente, un incremento de la concentración de fosfato en el agua intersticial con la profundidad se notó en aquellas zonas en las que se encontraron valores positivos de los flujos y que presentan altos porcentajes de las formas reactivas de fósforo en el sedimento. Por otra parte, los flujos bentónicos negativos parecen estar asociados a las estaciones que reciben más material de origen antropogénico y están relacionados con la disminución progresiva de las concentraciones de fosfato en el agua intersticial. En esas áreas antropogénicas, las formas no reactivas del fósforo (asociadas a oxihidróxidos de hierro y a carbonato fluorapatito autigénico) son las más abundantes, y llegan a alcanzar valores que superan el 75% del fósforo total del sedimento.

The presence and longitudinal and temporal distributions of the two main anionic surfactants, linear alkylbenzene sulfonates (LAS) and alkyl ethoxysulfates (AES), were monitored in surface sediments from the Guadalete estuary, located in the north of the Bay of Cadiz (SW of Spain). Seasonal samplings were performed for two years at three different stations; one of them located up-stream near the discharge outlet of a wastewater treatment plant (WWTP). A control station was also sampled in a tidal channel within the boundaries of a natural park adjacent to the estuary. LAS and AES concentration values ranged from 196 to 2864 ng g-1 and from 147 to 557 ng g-1, respectively, the lowest values corresponding to the control station and the highest ones found near the WWTP outlet. A general decrease in the concentrations of both surfactants was found in summer, when degradation processes are faster, whereas the highest concentrations were detected during the wet months, when temperature decreases and rainwater exceeds the WWTP capacity, so untreated wastewater is discharged directly into the river. Due to differential sorption and degradation processes, the relative distribution of LAS homologues in sediments showed higher percentages for those having longer alkyl chains, whereas AES homologues with an even carbon unit number in the alkyl chain and AES ethoxymers with fewer ethylene groups were predominant. No hazard for aquatic organisms was foreseen at the concentrations found for both surfactants along the estuary. Se ha realizado un seguimiento de la presencia y las distribuciones temporal y longitudinal de los dos tensioactivos aniónicos más usados -sulfonato de alquilbenceno lineal (LAS) y alquil etoxisulfatos (AES)- en sedimentos superficiales del estuario del río Guadalete, localizado al norte de la Bahía de Cádiz (SO de España). Para ello se llevaron a cabo muestreos estacionales durante dos años en tres estaciones diferentes, una de ellas localizada río arriba y en las inmediaciones de la zona de descarga de una estación depuradora de aguas residuales (EDAR). También se muestreó una estación control en un caño mareal situado dentro de los límites de un parque natural cercano al estuario. El rango de concentraciones de LAS y AES encontrado estuvo comprendido entre 196 y 2864 ng g-1 y entre 147 y 557 ng g-1 respectivamente, correspondiendo los valores más bajos a la estación control y los más altos a aquella situada cerca de la descarga de la EDAR. En términos generales, se detectó un descenso en las concentraciones de ambos tensioactivos durante el verano, cuando los procesos degradativos alcanzan mayor velocidad, mientras que las concentraciones más altas correspondieron a los meses con mayores precipitaciones, cuando se registra un descenso en la temperatura y tienen lugar descargas de agua residual sin tratar a causa de la saturación de la EDAR. Debido a procesos de adsorción y degradación diferencial, la distribución relativa de homólogos de LAS en el sedimento mostró un porcentaje mayor para aquellos con mayor longitud de cadena alquílica, mientras que los homólogos de AES con número par de carbonos en dicha cadena y los etoxímeros con menor número de grupo etoxilados fueron predominantes. No se detectó ningún riesgo para los organismos acuáticos teniendo en cuenta las concentraciones encontradas en el estuario para ambos tensioactivos.

Linear alkylbenzene sulfonates (LAS) are among the principal synthetic surfactants used worldwide. Their presence in the environment has been reported in a significant number of studies, and it has been generally assumed that LAS are not biotransformed in the absence of oxygen. However, laboratory experiments performed by our group using anoxic marine sediments have reported LAS degradation percentages that can reach up to 79% in 165 days. Here, we show for the first time the initial reaction metabolites (generated via fumarate addition to the LAS molecules), their biotransformation into sulfophenyl carboxylic acids (SPC), and the progressive degradation of these by successive beta-oxidation reactions. Advanced mass spectrometry has been used to carry out the identification of these compounds. This is the first time that an anaerobic degradation pathway for LAS is described, and these results represent a significant advance in understanding the final fate of these and other similar compounds in anoxic environments.

Most studies of oxygen solubility values for high salinity conditions have used synthetic solutions. The object of this study is therefore to propose an equation, valid for high salinity conditions, based on the analysis of oxygen saturation in evaporated seawater. In this study, the solubility of oxygen in evaporated seawater has been determined over a temperature range of 8–35°C and with salinity values of up to 133‰. Based on experimental data, an equation is proposed that introduces a S 2 (salinity) term, at 1 atm pressure, giving increased importance to salinity. The equation provides a valid means of predicting the amount of dissolved oxygen in this range of temperatures and salinities. In addition, for high salinity conditions, with this equation there is no need to extrapolate other established equations, which are less accurate at salinities higher than 40‰. The use of the proposed equation offers a more precise way of calculating oxygen solubility in seawater at high salinity values (up to 133‰), and small deviations from experimental values, of the order of 2 μmol kg−1, are obtained.

Dynamic laboratory simulation of processes affecting chemical species in their transit through estuaries is a very useful tool to characterize these littoral systems. To date, laboratory studies concerning biodegradation and sorption (onto suspended particulate matter) of LAS in an estuary are scarce. For this reason, a dynamic automated estuarine simulator has been employed to carry out different experiments in order to assess the biodegradability of linear alkyl benzene sulfonates (LAS) and their biodegradation intermediates (sulfophenylcarboxylic acids, SPCs) using environmentally representative LAS concentrations in estuaries by a continuous injection of LAS into the system. During the experiments, a great affinity of LAS for the solid phase has been found, as well as an increased adsorption in line with increased chain length. On the other hand, the presence of SPCs with chain length between 6 and 13 carbon atoms was detected. Accumulation and persistence of medium chain length SPCs (C 6 –C 8 ) along the experiments show that their degradation constitutes the limiting step for the process of LAS mineralization. In the final zone of the simulated estuarine system, the levels of SPCs were below the limits of detection. Thus, the disappearance of SPCs indicated that LAS biodegradation had been completed along the estuary. Similar results have been described for different Iberian littoral ecosystems. Therefore, the simulator employed in this research appears to be a useful tool to anticipate the behaviour of a xenobiotic chemical in its transit through littoral systems with different salinity gradients.

Synthetic surfactants are among the chemicals that are produced and consumed in the largest volumes in the world, due to the variety of their applications, mainly as key ingredients in detergents and cleaners. Particular attention has been given to anionic and non-ionic surfactants, which account for up to 90% of overall production of these chemicals, so understanding their distribution, behavior and final fate once they reach aquatic environments is very important. It is first necessary to develop reliable analytical methodologies for field sampling and laboratory assays, but also to identify the presence and the distribution of possible degradation intermediates. We provide an overview of techniques and protocols currently used – from extraction and purification techniques (e.g., pressurized fluid extraction or solid-phase extraction) – to separation and determination via gas or liquid chromatography coupled to mass spectrometry. Laboratory tests carried out under controlled environmental conditions are also required for complete characterization of the reactivity of these compounds in both water and sediment columns, mainly by monitoring the influence of the processes of sorption and degradation. We also discuss this topic, taking into account the results from previous laboratory experiments.

This study presents the distribution of dissolved inorganic carbon (DIC) along the Strait of Gibraltar, its tidal-induced variability, as well as the inorganic carbon exchange between the Atlantic Ocean and Mediterranean Sea. During November 2003, water column samples were collected at nine stations to measure total alkalinity (TA), pH, and dissolved oxygen (DO) for the spatial characterization of the carbonate system. At the same time, anchored samplings were carried out, above the Camarinal Sill and in the Eastern Section of the Strait, in order to assess the tidal mixing effects for oxygen and DIC distribution on the water column. Three distinct water masses can be discerned in this area: the Surface Atlantic Water (SAW), the Mediterranean Water (MW), and the less abundant North Atlantic Central Water (NACW). The observations show an increase in the DIC and a decrease in oxygen concentration with depth, related to the different physico-chemical features of each water mass. The results show the high time-dependence of the vertical distribution of DIC with the interface oscillation, affected by the intense mixing processes taking place in the Strait. Intense mixing episodes over the Camarinal Sill are responsible for an increase in the DIC concentrations in the upper layer of the Eastern Section of the Strait. Higher DIC concentrations in the Mediterranean than in the Atlantic waters are responsible for a net DIC transport of 1.47×10 12 mol C yr −1 to the Atlantic Ocean. Nevertheless, the net exchange is highly sensitive to the interface definition, as well as to the estimate of water volume transport used.

The present study describes the temporal variability of the water f CO 2 as well as the different driving forces controlling this variability, on time scales from daily to seasonal, in the Rio San Pedro, a tidal creek located in a salt marsh area in the Bay of Cadiz (SW Iberian Peninsula). This shallow tidal creek system is affected by effluents of organic matter and nutrients from the surrounding marine fish farms. Continuous p CO 2 , salinity and temperature were recorded for four periods of approximately one month, between February and September in 2004. Major processes controlling the CO 2 variability are related to three different time scales. Daily variations in f CO 2 are controlled by tidal advection and mixing of the water from within the creek and the seawater that enters from the Bay of Cadiz. Significant cyclical variations of the f CO 2 have been observed with the maximum values occurring at low tide. On a fortnightly time scale, the amplitude of the daily variability of f CO 2 is modulated by the variations in the residence time of the water within the creek, which are related to the spring–neap tide sequence. On a third time scale, high seasonal variability is observed for the temperature, salinity and f CO 2 . Maximum and minimum values for f CO 2 were 380 µatm and 3760 µatm for February and July respectively. Data suggest that seasonal variability is related to the seasonal variability in discharges from the fish farm and to the increase with temperature of organic matter respiratory processes in the tidal creek. The f CO 2 values observed are in the same range as several highly polluted European estuaries or waters surrounding mangrove forests. From the air–water CO 2 flux computed, it can be concluded that the Rio San Pedro acts as a source of CO 2 to the atmosphere throughout the year, with the summer accounting for the higher average monthly flux.

The main objective of the present study is to assess the temporal variability of the carbonate system, and the mechanisms driving that variability, in the Rio San Pedro, a tidal creek located in the Bay of Cadiz (SW Iberian Peninsula). This shallow tidal creek is affected by effluents of organic matter and nutrients from surrounding marine fish farms. In 2004, 11 tidal samplings, seasonally distributed, were carried out for the measurement of total alkalinity (TA), pH, dissolved oxygen and Chlorophyll- a (Chl- a ) using a fixed station. In addition, several longitudinal samplings were carried out both in the tidal creek and in the adjacent waters of the Bay of Cadiz, in order to obtain a spatial distribution of the carbonate parameters. Tidal mixing is the main factor controlling the dissolved inorganic carbon (DIC) variability, showing almost conservative behaviour on a tidal time scale. The amplitude of the daily oscillations of DIC, pH and chlorophyll show a high dependence on the spring–neap tide sequence, with the maximum amplitude associated with spring tides. Additionally, a marked seasonality has been found in the DIC, pH and oxygen concentrations. This seasonality seems to be related to the increase in metabolic rates with the temperature, the alternation of storm events and high evaporation rates, together with intense seasonal variability in the discharges from fish farms. In addition, the export of DIC from the Rio San Pedro to the adjacent coastal area has been evaluated using the tidal prism model, obtaining a net export of 1.05×10 10 g C yr −1 .

The distribution of inorganic carbon and the CO 2 exchange between atmosphere and water along the Guadalquivir Estuary (SW Iberian Peninsula) have been evaluated, on the basis of field observation performed from 2000 to 2003. The study consisted of the measurement of Total Alkalinity (TAlk), pH, continuous underway CO 2 partial pressure ( p CO 2 ), dissolved oxygen and chlorophyll. The Guadalquivir river water is rich in TAlk and DIC and its behaviour is mainly conservative along the salinity gradient. Estuarine waters were CO 2 oversaturated in all the samplings in space and time. It has been suggested some biogeochemical processes affecting the water p CO 2 such as the CO 2 flux to the atmosphere, aerobic respiration of organic matter, and carbonate dissolution. The average CO 2 flux to the atmosphere is 85.2 mmol m − 2 d − 1 and the total CO 2 emission to the atmosphere is 3.2 mol C 10 6 d − 1 . Ventilation of riverine CO 2 can contribute to the emission of CO 2 from inner estuaries although this factor seems highly variable among European estuaries. It has been estimated that, in the Guadalquivir Estuary, 34% of the total inorganic carbon exported is emitted to the atmosphere.

During 2004, 10 samplings were performed in order to measure dissolved methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) in the surface waters of Rio San Pedro, a tidal creek in the salt marsh area of the Bay of Cadiz (SW Spain). The inner partvs of the creek is affected by the inputs coming from an intensive fish farm and the drainage of an extensive salt marsh area. Dissolved CH4, CO2 and N2O concentrations ranged from 11 to 88 nM, 36 to 108 μM and 14 to 50 nM, respectively. Surface waters were in all cases oversaturated with respect to the atmosphere, reaching values of up to 5000% for CH4, 1240% for CO2 and 840% for N2O. Dissolved CH4, CO2 and N2O showed a significant tidal and seasonal variability. Over a tidal cycle, concentrations were always highest during low tide, which points to the influence of the inputs from the fish farm effluent and the drainage of the adjacent salt marsh area, as well as in situ production within the system. Dissolved CH4, CO2 and N2O seasonal patterns were similar and showed maximum concentrations in summer conditions. Using four different parameterizations to calculate the gas transfer coefficients [Liss, P.S. and Merlivat, L., 1986. Air-sea exchange rates: introduction and synthesis. In P. Buat-Menard (Ed.), The Role of Air-Sea Exchanges in Geochemical Cycling. Reidel, Dordrecht, The Netherlands, p. 113–127.; Clark, J.F., Schlosser, P., Simpson, H.J., Stute, M., Wanninkhof, R., and Ho, D.T., 1995. Relationship between gas transfer velocities and wind speeds in the tidal Hudson River determined by the dual tracer technique. In: B. Jahne and E. Monahan (Eds.), Air-Water Gas Transfer: AEON Verlag and Studio, Hanau, Germany, pp. 785–800.; Carini, S., Weston, N., Hopkinson, G., Tucker, J., Giblin, A. and Vallino, J., 1996. Gas exchanges rates in the Parker River estuary, Massachusetts. Biol. Bull., 191: 333–334.; Kremer, J.N., Reischauer, A. and D'Avanzo, C., 2003. Estuary-specific variation in the air-water gas exchange coefficient for oxygen. Estuaries, 26: 829–836.], the averaged air–water fluxes of CH4, CO2 and N2O from the creek to the atmosphere ranged between 34 and 150 μmol CH4 m− 2 day− 1, 73 and 177 mmol CO2 m− 2 day− 1 and 24 and 62 μmol N2O m−2 day−1, respectively.

This research shows for the first time the degradation of linear alkylbenzene sulfonates (LAS) under anaerobic conditions, together with the presence of metabolites and the identification of microorganisms involved in this process. This compound is the most widely used surfactant and its main environmental concern is related to its persistence in the absence of oxygen as LAS accumulates in anaerobic sediments and sewage sludges. Laboratory experiments performed with anoxic marine sediments spiked with 10-50 ppm of LAS demonstrated, however, that its degradation reached 79% in 165 days via the generation of sulfophenyl carboxylic acids (SPCs). Almost all of the added LAS (>99%) was found to be attached to the sediment while the less hydrophobic SPCs were predominant in solution, as their concentration increased progressively up to 3 ppm during the full course of the experiment. Average half-life for LAS has been estimated to be 90 days, although higher values should be expected when the LAS concentration exceeds 20 ppm, due to inhibition of the microbial community. Sulfate-reducing and methanogenic activities proved to be intense during the experiment. Several sulfate-reducing bacteria and firmicutes/clostridia have been identified as possible candidates for effecting this degradation. Our results imply that the persistence of LAS in anoxic compartments, such as marine sediments, should be reconsidered when evaluating its environmental risk.

An accompanying article has demonstrated the anaerobic degradation of the surfactant linear alkylbenzene sulfonate (LAS) in microcosms filled with marine sediments through the generation of sulfophenylcarboxylic acids (SPCs). A detailed study shows that this process was uniform in the blanks (non-spiked natural sediments) for every LAS homologue during the complete course of the experiment. However, when sediments were spiked with commercial LAS and, therefore, enriched with short-chain homologues, degradation was enhanced for these homologues until their percentages were close to those for non-spiked sediments. The reason is that short-chain homologues are more bioavailable due to their higher solubility and lower sorption capacity. Thus, sorption on sediments was found to be increased with the length of the alkyl chain for LAS homologues, following a linear Freundlich isotherm, whereas the metabolites generated were predominant in solution due to their much higher polarity. Intermediate-chain SPC homologues (C7-C9 SPCs) were the most abundant during the experiment, but a significant increase in the concentration of shorter-chain SPC homologues (C4-C6 SPCs) was detected toward the end. In the case of isomers, the steric effect of the aromatic group implies that LAS primary degradation took place preferentially over external isomers. Therefore, the generation of external isomers of SPCs was predominant during the complete experiment although internal isomers of SPCs became more evident when the degradation process had advanced and external isomers of LAS became scarce. The identity of both types of SPC isomer was confirmed by tandem mass spectrometry. With respect to LAS coproducts, the relative percentage of iso-LAS increased during the complete experiment and removal percentages for dialkyl tetralinsulfonates (30%) were typically lower that those for LAS (66-79%), although a similar behavior was observed for their homologues in both cases.

Phosphate behaviour in natural estuarine systems can be studied by performing field measurements and by undertaking laboratory simulation experiments. Thus, in this paper we describe the use of a dynamic automated estuarine simulator to characterize the geochemical reactivity of phosphate in varying salinity gradients in order to study possible mechanisms of phosphate removal from the dissolved phase (e.g. formation of some kind of apatite) and how changes in pH and salinity values influence this removal. Six laboratory assays, representing various salinity and pH gradients (average pH values between 7 and 8), were carried out. The geochemical equilibrium model MINTEQA2 was employed to characterize removal of phosphate. Among the minerals from which dissolved phosphate can originate, it seems that hydroxyapatite is by far the mineral that shows the greatest saturation indexes in the experiments. Thus, there is evidence that a type of calcium phosphate (hydroxyapatite) is involved in phosphate removal in the assays. Phosphate removal by Ca2+ occurs sharply at salinity values of 1–2, whereas by Fe3+ it is relatively gradual, at least until a salinity value of 7. Copyright © 2006 John Wiley & Sons, Ltd.

A simple and fast method is described for the determination in marine sediments of the anionic and non-ionic surfactants most commonly used worldwide. This group of compounds includes linear alkylb...

Molar absorptivities of thymol blue have been determined in synthetic solutions of ionic strength ranging from 0.1 to 0.7 Mw. The solutions were buffered to pH 11.5 in order to characterize the absorption spectrum of the basic form of the indicator and to pH 5.0 to characterize the HI– form. The extinction coefficients corresponding to the maximums of absorption of these forms of the indicator, as well as the molar absorptivities that describe the residual absorbances at the same wavelengths, were determined through linear regression between the indicator concentration in these samples and the absorbances of the maximums after successive additions of 2 mM thymol blue. A linear dependence of the molar absorptivities was found with temperature between 5ºC and 30ºC, and with salinity only for 596ε (I2–). The application of the expressions of the molar absorptivities for the calculation of the spectrophotometric pH provided results in accordance with the potentiometric pH measurements in the total hydrogen ion concentration scale

The diffusive and in situ fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA) have been measured and an estimation has been made of the water–atmosphere fluxes of CO2 in three estuarine systems of the Cantabrian Sea during the spring of 1998. Each of these systems undergoes a different anthropogenic influence. The diffusive fluxes of dissolved inorganic carbon and total alkalinity obtained present values ranging between 0.54–2.65 and 0.0–2.4 mmol m−2 day−1, respectively. These ranges are in agreement with those of other coastal systems. The in situ fluxes are high and extremely variable (35–284 mmol TA m−2 day−1, 43–554 mmol DIC m−2 day−1 and 22–261 mmol dissolved oxygen (DO) m−2 day−1), because the systems studied are very heterogeneous. The values of the ratio of the in situ fluxes of TA and DIC show on average that the rate of dissolution of CaCO3 is 0.37 times that of organic carbon oxidation. Equally, the interval of variation of the relationship between the benthic fluxes of inorganic carbon and oxygen (FDIC/FDO) is very wide (0.3–13.9), which demonstrates the different contributions made by the processes of aerobic and anaerobic degradation of the organic matter, as well as by the dissolution–precipitation of CaCO3. The water–atmosphere fluxes of CO2 present a clear dependence on the salinity. The brackish water of these systems (salinity 30) act as a sink of CO2, with fluxes between −5 and −10 mmol m−2 day−1.

A new method has been developed for the determination of linear alkylbenzene sulfonates (LAS) from various marine organisms, and compared with Soxhlet extraction. The technique applied includes the use of pressurized liquid extraction (PLE) for the extraction stage, preconcentration of the samples, purification by solid-phase extraction (SPE) and analysis by liquid chromatography with fluorescence detection. The spiked concentrations were added to the samples (wet mass of the organisms: Solea senegalensis and Ruditapes semidecussatus ), which were homogenized and agitated continuously for 25 h. The samples were extracted by pressurized hot solvent extraction using two different extraction temperatures (100 and 150 °C) and by traditional Soxhlet extraction. The best recoveries were obtained employing pressurized hot solvent extraction at 100 °C and varied in the range from 66.1 to 101.3% with a standard deviation of between 2 and 13. Detection limit was between 5 and 15 μg kg −1 wet mass using HPLC–fluorescence detection. The analytical method developed in this paper has been applied for LAS determination in samples from a Flow-through exposure system with the objective of measuring the bioconcentration of this surfactant.

A study has been made of the aerobic biodegradation of linear alkylbenzene sulfonates (C12 and C11 homologues) and sulfophenylcarboxylic acids (C5 and C11 homologues) in seawater at concentrations of the same order as those detected ones in coastal waters influenced by wastewater effluents, at different temperatures, and both with and without the addition of an inoculum adapted to the presence of linear alkylbenzene sulfonate (LAS). The biodegradation of C12LAS, C11LAS, C5SPC, and C11SPC exceeds 99% in all tests performed and can be satisfactorily fitted to a second-degree polynomial without an independent term. The kinetic of degradation of LAS presents a clear seasonal component, since the process is considerably inhibited at lower temperatures; it is also kinetically enhanced by the presence of the inoculum. The intermediates detected for all the cases are sulfophenylcarboxylic acids (SPCs), the most abundant being those intermediates produced by the omega- and beta-oxidations of the parent compound, although intermediates produced by the alpha-oxidation have also been detected. The kinetic of the SPCs generated can be described using a model composed of two terms that represent the formation and the degradation of these intermediates. The total disappearance of the SPCs in all cases indicates that the degradation of LAS in seawater at the tested concentrations in aerobic conditions is complete.

14 páginas, 9 figuras, 2 tablas., [EN] Acid and alkaline phosphatase activities (E.C.3.1.3.2 and E.C.3.1.3.1, respectively) were measured in seawater and sediments from different sites of a salt-pond of the Bay of Cádiz. The profiles of enzymatic activity relative to depth were also analysed. Initially, the optimum conditions (pH, temperature, substrate concentration and amount of sample) for determining enzymatic activities were studied. The apparent activation energies for alkaline phosphatase activity in seawater and sediments were 53.8 and 48.6 kJ mol–1, respectively. The Km and Vmax were 10.6 mM and 89 μg of 4-nitrophenol g–1 h–1 and 8.42 mM and 145 μg of 4-nitrophenol L–1 h–1 for sediments and seawater, respectively. Both types of enzymatic activity reached high values in seawater and sediments; in the confined areas of the salt-pond the values were around 100 μg of 4-nitrophenol L–1 h–1 for seawater and higher for sediments. In general, clear seasonal evolutions for both types of enzymatic activity were found in the seawater, with maxima at the end of summer and minima in winter. No seasonal pattern was evident in the sediment. Stratification of phosphorus regeneration was observed in the sediment column but there was no stratification at depths greater than 15 cm., [ES] Se midieron las actividades fosfatásicas ácida y alcalina ((E.C.3.1.3.2 y E.C.3.1.3.1, respectivamente) en muestras de agua y sedimento en diferentes estaciones de salinas de la Bahía de Cádiz. También se analizaron los perfiles de actividad fosfatásica con relación a la profundidad. Se estudiaron las condiciones óptimas (pH, temperatura, concentración de sustrato y cantidad de muestra) para la determinación de las actividades enzimáticas. La energía de activación aparente para la actividad fosfatásica alcalina en agua y sedimento fueron 53.8 y 48.6 kJ mol–1, respectivamente. Los valores de Km y Vmax fueron 10.6 mM y 89 μg de 4-nitrofenol g–1 h–1 y 8.42 mM y 145 μg de 4-nitrofenol L–1 h–1, para sedimentos y agua, respectivamente. Ambos tipos de actividades enzimáticas presentan elevados valores en agua y sedimentos; en las áreas más confinadas de las salinas, los valores alcanzados llegan a ser del orden de 100 μg de 4-nitrofenol L–1 h–1 en las muestras de agua de mar, y superiores en los sedimentos. En general, se apreciaron evoluciones estacionales para ambos tipos de actividades fosfatásicas en las muestras de agua, con máximos a finales del verano y mínimos en invierno. En los sedimentos no se observó esta estacionalidad. La estratificación en la regeneración del fósforo es apreciable en la columna del sedimento, si bien ésta no se observa a profundidades mayores de 15 cm.

The benthic fluxes of inorganic carbon, total alkalinity and oxygen were measured in five shallow coastal ecosystems located along the coast of the Iberian Peninsula (Southern Europe). The measured values ranged between 135 and 447 mmol m−2 day−1 for inorganic carbon, between 22 and 206 mmol m−2 day−1 for total alkalinity, and between 98 and 199 mmol m−2 day−1 for oxygen. These are higher than most fluxes reported previously in other coastal systems. They presented a linear correlation with the organic carbon content of surface sediments found in the systems studied. For the two sampling stations situated in the Bay of Cadiz, a significant dependence of the benthic fluxes on the temperature has been observed, with an activation energy value ranged between 45 and 53 kJ mol−1 based on inorganic carbon flux data, and ranged between 34 and 44 kJ mol−1 based on oxygen flux data. The relationship between the fluxes of inorganic carbon and oxygen increases with the concentration of organic carbon in the surface sediments, from values close to 1 up to values in excess of 3, and is found to be affected by variations in temperature. From the vertical profiles in the interstitial water, sulfate-reduction appears to be one of the principal routes of anaerobic oxidation of the organic matter in these systems, and is to a large extent responsible for the variations in pH found and the variation of the ratio of DIC/DO fluxes.

The spill at 'Los Frailes' caused a large input of metals into the riverine, estuarine and coastal ecosystems. Metal behaviour in natural waters can be studied both by performing field measurements, and by undertaking laboratory simulation experiments. Here is described the behaviour of the heavy metals Zn, Cd, Pb and Cu in the Guadalquivir estuary using incubation experiments and the results compared to those obtained during field assessments. If the toxic waste water had been discharged untreated into the environment, it could have raised the heavy metal concentrations in the estuary water to high values, such as 20.65 microM for Zn and 40 x 10(-3) microM for Cd. These values are several times higher than those obtained in samples collected in the area during the monitoring of the early impact. The metals present a non-conservative behaviour, with a high loss to waters of low salinity values.

The distribution of linear alkylbenzene sulfonates (LAS) and sulfophenylcarboxylic acids (SPC) has been characterized in water and sediment of five Iberian estuaries and a saltmarsh channel. The highest concentrations of LAS and SPC were detected in shallow zones close to discharge points of untreated urban effluent, and decreased sharply with increasing distance from these. SPC homologues of between 3 and 12 carbon atoms were detected, although their concentrations were several orders of magnitude lower than the corresponding LAS. The highest SPC concentrations found were of medium carboxylic chain lengths (C6-C8) in water, and of longer chain lengths (C9-C11) in particulate material. LAS homologues were associated preferentially with the particulate material. The vertical distribution of LAS in the water column was not homogeneous, in contrast to that presented by the SPC homologues. In the case of the Sancti Petri Channel, there was a net flow of LAS exportation into the Bay of Cádiz, of -38.6 kg day(-1), and a net flow for SPC of -6.0 kg day(-1). The daily mass input of LAS and their biodegradation intermediates from the Sancti Petri Channel to Cadiz Bay was 44.6 kg.

Sorption experiments using different homologues of linear alkylbenzene sulfonate (LAS) and sulfophenylcarboxylic acid (SPC) on several marine microalgae have been carried out. The steady state seems to be reached in the first 4 hours. Longer exposure times lead to biodegradation of the compound and, therefore, to an overestimation of the bioconcentration factor. Sorption coefficients are higher for Nannochloropsis gaditana, for example, 1,293 Lkg(-1) for C11-LAS and 525 Lkg(-1) for C11-SPC versus 727 Lkg(-1) for C11-LAS and 28 Lkg(-1) for C11-SPC for Dunaliella salina. For both algae an increase in the sorption coefficient is observed when the polarity of the compound decreases (C5-SPCC11-SPCC11-LAS approximately/= C12-LAS). The sorption of C11-LAS on D. salina is fitted to a linear Freundlich isotherm (K=176+/-0.02, n=0.964+/-0.02).

The synthesis and preliminary assays as hypocholesterolemic agents of five N-diphenylmethylpiperazines are described. The evaluations were carried out in hypercholesterolemic mice and two of these compounds were more effective than bezafibrate in the test employed. The di-p-chlorosubstituted compounds showed higher activity than their corresponding dechlorinated analogs. Synthese und hypocholesterolemische Aktivitat von einigen N-Diphenyl-methylpiperazin-Derivaten Funf N-Diphenylmethylpiperazine wurden synthetisiert und ihre hypocholesterolemische Aktivitat an hypercholesterolaemischen Mausen untersucht. Zwei Substanzen zeigten eine hohere Aktivitat als Bezafibrat. Die di-p-chlo-rosubstituierten Verbindungen waren aktiver als die dechlorierten Analoga.

The Guadalquivir estuary was impacted by the accidental release of 5 million cubic meters of acid waste from the processing of pyrite ore (25 April 1998). The waste entered ecologically sensitive and protected areas such as the National Park of Donana. Here are presented the results obtained from a time sequence of different sampling sites in the estuary and in the surrounding areas from May to September 1998. Water, suspended solids and sediments were analysed for six different metals (Fe, Mn, Zn, Cd, Pb, Cu). Also, the concentration of the metals in the different geochemical sediment fractions was determined as a means of assessing bioavailability. The results obtained during the first weeks after the incident show high concentrations of Zn. At the end of June a 10 000 m 3 temporary water-treatment plant was constructed on site for depuration of the toxic waters. The results obtained in August and September show a decrease in the metal concentrations measured in the estuary. Only concentrations of Zn were higher than sediment quality values proposed by various authors.

Concentrations of the heavy metals Cr, Cu, Fe and Mn were measured in sediments and porewater samples collected in three coastal ecosystems southwest of the Iberian Peninsula: the Odiel and Barbate River Salt Marshes and the Bay of Cadiz. Both the sediment and the porewater metal concentrations in the Odiel River Salt Marshes are higher than the values found in the Bay of Cadiz and Barbate River Salt Marsh, particularly for copper, a metal associated with mining activity. In porewater, the profiles were not the same as those in the solid phase and reflect the different behaviours of the elements in relation to the redox conditions. The heavy metals Cr and Cu show a typical enrichment in the porewater of the oxic zone. The heavy metals Mn and Fe show an increase in the porewater at the depths where the maximum nitrate and phosphate concentrations occur, respectively. Significant differences between background levels for each heavy metal in the various studied zones exist. Iron and Cu showed larger background levels in the Odiel River Salt Marshes than those in the Cadiz Bay and the Barbate River Salt Marshes. In the Bay of Cadiz the background levels are also high, particularly for Cr. At the Odiel River Salt Marshes the diffusive flux of Cu is high (1.3-230.1 microg cm(-2) year(-1)), which suggests that the Odiel River Salt Marshes are subject to strong contamination by Cu, which is presumably introduced to the sediment in particulate form. In the Bay of Cadiz, Cr is the only metal with positive diffusive flux (2.15 microg cm(-2) year(-1)). It is higher than those obtained in other coastal ecosystems including the Odiel River Salt Marshes. The positive diffusive flux of Cr has been associated with the input of this metal by the naval industry and the manufacturing of car and aircraft components.

A number of natural and man-made chemicals possess estrogenic activity, i.e. they induce a variety of estrogen dependent responses in vertebrates. These xenobiotics include a variety of surfactants such as alkylphenolpolyethoxylates (APnEO) and their biodegradation products. Another group of synthetic surfactants are the linear alkylbenzene sulfonates (LAS). Recently high concentrations of LAS and intermediate products of LAS biodegradation, sulphophenyl carboxylates (SPC), have been found in the Bay of Cadiz, Spain. Due to their similar chemical properties with the estrogenic APnEO it has been speculated that LAS and their metabolites have estrogenic effects. The present work addresses the question upon the possible estrogenicity of LAS and LAS metabolites by two in vitro assays: the vitellogenin assay with unaltered trout hepatocytes and the yeast estrogen receptor assay. No estrogenic effects were observed for any of the compounds tested.

Long-chain sulfophenyl carboxylate compounds (SPC) with more than five carbon atoms, which are degradation products of linear alkylbenzenesulfonates (LAS), have been isolated by solid-phase extraction (SPE) followed by identification with liquid chromatography/ ionspray—mass spectrometry (LC/ISP-MS). The isolation procedure involved extraction in a C18 minicolumn and subsequently in a strong anionic exchange (SAX) column, the final determination was accomplished by Negative Ion LC/ISP/MS using a two step approach. First, a chromatographic run at a cone voltage of 80 V was performed. At this voltage the major fragment ion corresponded either to m/z 183 (C11 SPC and LAS) or to m/z 170 (C6SPC to C10SPC), and permitted the confirmation of LAS and SPC. The second step involved an extraction cone voltage of 20 V. In this case [M-H]− ion was the base peak for all the studied compounds (LAS and SPC) and was used as a quantitative ion. The linear range of the proposed method varied from 0.4 to 10 ppb with a limit of detection ranging from 2–20 ppt when 250 mL of coastal water were preconcentrated. The present method represents an important advancement for the unequivocal trace determination of the polar degradation products of LAS, SPC, since current established protocols involve either the use of derivatization/gas chromatography-mass spectrometry and/or liquid chromatography with UV detection. By using the protocol described the direct confirmation and quantitative trace determination of both LAS and their polar metabolites SPC is feasible.

A factor analysis was carried out to interpret the variability observed in the data obtained for a salt-marsh area to the south of the Bay of Cadiz in the southwest of Spain. A case involving the quantitation of 15 variables in 273 water samples of the Sancti Petri Channel has been selected for examination. An overall synthesis of all the information obtained from the factor analysis establishes five processes that determine the hydrochemistry of the zone: mineralisation, influence of urban effluents, seasonality, degree of agitation and action of the tides. Of all the processes, the mineralisation of the organic matter stands out as the main process determining the hydrochemistry of the zone.

The distribution of linear alkylbenzene sulfonates (LAS) and their biodegradation intermediates (SPC) has been studied at a salt marsh of the Bay of Cadiz. The identification and quantification of LAS and SPC was carried out after solid-phase extraction of 250 mL of water samples followed by liquid chromatography with fluorescence, diode array, and ionspray mass spectrometry. The latter procedure permitted the unequivocal confirmation of long-chain SPC, of up to 11 carbon atoms in seawater, and of up to 13 carbon atoms in interstitial water. Some of these compounds have not been described until now in environmental samples. The relative abundance of the SPC found at some of the sampling stations agrees with what would be expected after the occurrence of the first and second β-oxidations of the alkyl chain of the various homologues of commercial LAS. Furthermore, the existence of SPC-C13 in interstitial water proves unequivocally that ω-oxidation occurs in the environment. In general terms, the persistence...

The determination of synthetic anionic surfactants and their degradation products in environmental samples is a complex problem. This complexity is even greater in seawater, especially from littoral zones, owing to the presence of numerous organic substances that may potentially interfere with the analysis of the samples; more common among these are naturally-occurring surfactant compounds. Various stages are involved in the determination of linear alkylbenzene sulfonates (LAS), which are the surfactants most used commercially, and their degradation products (sulfophenylcarboxylic acids or SPC); successful completion of these analytical stages should result in the concentration of these compounds, their isolation, their quantification and, in cases where no reference standards are available, their structural identification. At the present time, some of these stages are still under development.

Spatial and seasonal variation in benthic fluxes of nutrients, oxygen and alkalinity were measured in the Bay of Cadiz, a temperate semi-confined shallow water ecosystem. Oxygen, alkalinity, ammonia, phosphate and silicate fluxes averaged (mean ± SD) 137·5 ± 48·1, 376·3 ± 177·3, 17·7 ± 7·5, 4·4 ± 2·5 and 14·8 ± 8·8 mmol m -2 day -1 , respectively. These values are high in comparison to those previously reported for other coastal locations in similar latitudes. Benthic fluxes clearly changed seasonally and an exponential relationship with temperature was found. Apparent flux activation energies ranged between 10.7 kcal mol -1 for phosphate and 18·1 kcal mol -1 for silicate. Seasonal variation in the stoichiometry of nutrient, oxygen and alkalinity fluxes revealed an intensification in the anaerobic decomposition pathways of organic matter during the summer. Spatial variation, oxygen and alkalinity fluxes were found to be linearly correlated with the organic matter content of the sediment (measured as organic carbon). Also, ammonia and phosphate fluxes increased as the C/N ratio of the incorporated organic matter in the sediment decreased.

Vertical profiles of total alkalinity, pH, and salinity, as well as ammonia, silicate, sulphate, sulphur and borate concentration in the interstitial water of sediments from the Bay of Cadiz were measured. The results established which of those chemical species included in Dickson's (1981) definition have an influence on total alkalinity above the limits of accuracy of the analytical method. This enables an operative definition of alkalinity in interstitial waters to be proposed: A T =[ HCO 3 − ]+2[ CO 3 2− ]+[ B ( OH ) 4 − ]+[ OH − ]+[ HPO 4 2− ]+2[ PO 4 3− ]+[ SiO ( OH ) 3 − ]+[ HS − ]+[ NH 3 ] The main advantage is that with only a moderate amount of analytical work, the speciation of inorganic C in the interstitial water can be accurately determined. At the same time, the analytical method proposed by Van den Berg and Rogers (1987) for estuarine waters has been revised and adapted for the measurement of alkalinity in interstitial waters.

In vivo experiments with fish (sole) were performed for pure homologs of linear alkylbenzene sulfonates (LAS) and alcohol ethoxylates (AEO), the most widely used anionic and nonionic surfactants. The surfactant concentration measured in the organism was higher than in the experimental water, and increased with the exposure concentration for both compounds. At the exposure levels tested the bioconcentration factors (BCF) for AEO were one order of magnitude higher than for LAS. Two linear relationships for hydrophobicity were established, one with BCF and the other with uptake rate. The influence of the exposure concentration on the uptake (k(1)) and elimination (k(2)) velocities was researched. The value obtained for k(1) for AEO was higher than for LAS, while k(2) was very similar for both compounds, indicating differences in the incorporation and but not in the depuration rate. For the first time, internal degradation products of LAS were identified and quantified in fish and water and the glucuronic conjugate of AEO was detected in an organism. The predominant biotransformation process for these compounds may be different: the results suggest a phase I biotransformation for LAS and phase II for AEO, due to their different molecular structures.

For development of new cardiotonic agents a series of 5-aryl-3,4-dihydropyridin-2(1H)-ones, related to amrinone have been prepared from methylquinolines, 2-arylacetic acid or 3-arylethanones by direct aminomethylenation and subsequent condensation-cyclization with malonamide and cyanacetamide in classic basic media or phase-transfer catalysis, in good to excellent yields. Preliminary pharmacological assays have shown that these compounds, especially 5h and 5i, have a remarkable cardiotonic effect and present a selective inhibition of PDE-III/PDE-I isolated from cat heart.

Primary degradation of a linear‐chain sodium dodecyl benzene sulphonate was studied in the laboratory by using water and sediments taken from various points in the Bay of Cadiz and the surrounding tidal lands and marshes. The degradation, carried out in a testing system quite similar to the “river‐die‐away”;, was shown to depend on the granulometric characteristics of the sediment and on the initial surfactant concentration. In most test runs, the biodegradation kinetic equations derived from the process showed good agreement with the non‐structured model of bacterial growth proposed by Velhurst and Pearld & Read1, and subsequently modified by Volterra1.

For development of new cardiotonic agents a series of 5-aryl-3,4-dihydropyridin-2(1H)-ones, related to amrinone have been prepared from methylquinolines, 2-arylacetic acid or 3-arylethanones by direct aminomethylenation and subsequent condensation-cyclization with malonamide and cyanacetamide in classic basic media or phase-transfer catalysis, in good to excellent yields. Preliminary pharmacological assays have shown that these compounds, especially 5h and 5i, have a remarkable cardiotonic effect and present a selective inhibition of PDE-III/PDE-I isolated from cat heart.

10 páginas, 6 figuras.-- The final publication is available at www.springerlink.com, From September 2005 to May 2006 four cruises were performed in the Strait of Gibraltar to study the seasonal variability of carbon dioxide surface waters and assess the air-sea CO2 fluxes. Continuous water measurement of fugacity ofCO2 (fCO2), temperature and salinity was performed along the longitudinal and latitudinal axes of the Strait. Additionally, discrete surface water samples were taken to measure dissolved inorganic carbon (DIC) and oxygen. The spatial distribution of surface fCO2 showed low variability compared to the seasonal scale, with fCO2 values ranging from 329 matm in March to 387 matm in September. Seasonal variability of fCO2 was assessed and discussed in terms of temperature and biology, and the temperature was the main controlling factor. The Strait of Gibraltar is CO2 undersaturated most of the year, except in September, when the annual average CO2 uptake equals 0.28 mol C m 2 yr 1, if behaves as a discreet sink of CO2 on an annual scale, This work has been supported by the Spanish CICYT under the contract CTM2005-01364/MAR and by the European CARBOOCEAN IP (511176 GOCE)

Presence, distribution and transport mechanisms of the four major synthetic surfactants--linear alkylbenzene sulfonates (LAS), alkyl ethoxysulfates (AES), nonylphenol ethoxylates (NPEOs) and alcohol ethoxylates (AEOs)--have been simultaneously studied in different aquatic ecosystems. Urban wastewater discharges and industrial activities were identified as the main sources for these compounds and their metabolites. LAS, AES and carboxylic metabolites remained in the dissolved form (87-99%). However, NPEOs and AEOs were mostly associated with particulate matter (65-86%), so their degradation in the water column was limited due to their lower bioavailability. It was also observed that sorption to the particulate phase was more intense for longer homologs/ethoxymers for all surfactants. With respect to surface sediments, AES levels were considerably below (

A method for the simultaneous determination of semi-volatile organic contaminants (polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine and organophosphorus pesticides) in marine samples has been developed, for the first time, using the stir bar sorptive extraction technique (SBSE) and thermal desorption coupled to capillary gas chromatography-mass spectrometry (SBSE-TD-GC-MS). Polydimethyl siloxane (PDMS) was used for the extraction of the selected analytes and two procedures have been optimised and validated, one for seawater samples (100 mL) and another for interstitial water samples (10 mL), using PDMS stir bars of 20 mm and 10 mm size, respectively. The extraction and analytical conditions, such as extraction time, matrix effects, sample volume and desorption time, were optimised. The proposed methods are sensitive, simple and show good linearity and detection limits lower than 1 ng L(-1) with seawater and lower than 10 ng L(-1) with interstitial marine water for the majority of compounds tested. Repeatability and reproducibility, expressed as relative standard deviation, have values lower than 20% for the majority of analytes considered. The recoveries for both sample volume procedures are higher than 60 and 70% for 10 and 100 mL, respectively, except for the more apolar (some PAHs and PCBs) and the more polar (some triazines) analytes which present lower values. The present SBSE/GC/MS method was applied for the analysis of trace organic contaminants in seawater and interstitial water samples from Cadiz Bay (SW of Spain). Terbutylazine, DDX and some PAHs were found at several seawater sampling points at ng L(-1) levels, and some PAHs in interstitial water too.