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International audience; Elemental concentrations of Rare Earth Elements (REE) and isotopic compositions of Neodymium (ε Nd) have been measured in three water column profiles in the North Western Mediterranean Sea. Clear enrichments of REE are observed when comparing to adjacent Atlantic waters suggesting REE inputs along the circulation in this area. For the first time, relative proportions of external sources including submarine groundwater discharges (SGD) have been quantified for the studied area. Atmospheric deposition is estimated to be the most important external source for all the REE with an average contribution of 44%, followed by diffusion from porewaters, which provide a 30%. Dissolved riverine fluxes account for 11%, SGD for 10% and dissolution of remobilized surface sediments the remaining 6%. Mass balances accounting for seawater transport and identified external sources have been delineated for the three main water masses (Modified Atlantic Waters, Levantine Intermediate Waters and Western Mediterranean Deep Waters). They show that the balances of REE in this area are dominated by seawater mass mixing. Superimposed on this hydrography, REE vertical profiles are affected by external sources and biogeochemical cycling. Dissolved REE are correctly balanced in deep waters whereas substantial missing fluxes are identified in the surface and intermediate water masses. Additional net LREE outputs and HREE inputs are required in the surface waters while net output fluxes for all the REE are missing at intermediate waters. The most likely process suggested here is an active reversible scavenging, consistent with a stronger adsorption of LREE compared to HREE. In the particular case of the redox-sensitive cerium, the most plausible mechanism to explain the net output missing fluxes is Ce +3 removal by particle scavenging via oxidation to insoluble Ce +4. Estimated Ce oxidation rates of 0.33% d −1 in surface waters agree well with previously published values. Exchange fluxes derived from the isotopic Nd mass balance indicate higher Nd scavenging in surface compared to intermediate waters.

International audience; Submarine groundwater discharge (SGD) has been identified as an important source of Sr to the ocean and the SGD-driven Sr flux to the global ocean has been recently re-evaluated (Beck et al., 2013). However, the uncertainty of this value is still high because of the uncertainties related to the determination of SGD flow rates and the paucity of (Sr/Sr)-Sr-87-Sr-86 data in SGD end-members. As carbonates have high Sr concentrations and are subjected to intense heightened weathering, they might significantly influence the SGD input of Sr to the ocean. Here we present data on Sr concentrations and Sr-87/Sr-86 ratios in three carbonate dominated sites of the western area of the Mediterranean Sea, a semi-enclosed basin characterized by abundant coastal carbonates. The Sr-87/(86) Sr ratios in groundwater were lower compared to modern seawater (similar to 0.70916), as expected for areas dominated by carbonate lithologies. Concentrations of Sr and Sr-87/Sr-86 ratios in groundwater showed conservative mixing in the studied subterranean estuaries. By using SGD flow rates reported in the literature for the study areas, a flow-weighted fresh SGD end-member characterized by a Sr concentration of 27-30 mu M and a Sr-87/Sr-86 ratio of 0.707834-0.708020 was calculated for the eastern coast of the Iberian Peninsula. Integrating these Sr data with literature data (i.e. values of Sr concentration and Sr-87/Sr-86 ratio from other lithologies as well as SGD flow rates), we also calculated the fresh SGD-driven Sr flux to the entire Mediterranean Sea, obtaining a value of (0.34-0.83) . 10(9) mol y(-1), with a Sr-87/Sr-86 of 0.7081-0.7086. Thus, for the entire Mediterranean basin, SGD is globally a source of Sr less radiogenic compared to seawater. The SGD Sr flux to the Mediterranean Sea represents 5-6% of the SGD Sr flux to the global ocean and the Mediterranean SGD end-member has higher Sr concentration (5-12 mu M) than the global SGD end-member (2.9 mu M). This confirms the significant role of carbonate lithologies on SGD-driven Sr fluxes to seawater. The fresh SGD-driven Sr flux to the Mediterranean Sea is about 20-50% of the riverine Sr input and significantly higher than the input through atmospheric dust deposition. Therefore SGD should be considered as an important continental source of Sr to the basin. (C) 2016 Elsevier Ltd. All rights reserved.

Numerous studies have used naturally occurring Ra isotopes (223Ra, 224Ra, 226Ra, and 228Ra, with half-lives of 11.4 d, 3.7 d, 1600 y, and 5.8 y, respectively) to quantify water mass ages, coastal ocean mixing rates, and submarine groundwater discharge (SGD). Using Monte Carlo models, this study investigated how uncertainties in Ra isotope activities and the derived activity ratios (AR) arising from analytical uncertainty and natural variability affect the uncertainty associated with Ra-derived water ages and eddy diffusion coefficients, both of which can be used to calculate SGD. Analytical uncertainties associated with 224Ra, 226Ra, and 228Ra activities were reported in most published studies to be less than 10% of sample activity; those reported for 223Ra ranged from 7% to 40%. Relative uncertainty related to natural variability — estimated from the variability in 223Ra and 224Ra activities of replicate field samples — ranged from 15% to 50% and was similar for 223Ra activity, 224Ra activity, and the 224Ra/223Ra AR. Our analysis revealed that AR-based water ages shorter than 3–5 d often have relative uncertainties greater than 100%, potentially limiting their utility. Uncertainties in eddy diffusion coefficients estimated based on cross-shore gradients in short-lived Ra isotope activity were greater when fewer points were used to determine the linear trend, when the coefficient of determination (R2) was low, and when 224Ra, rather than 223Ra, was used. By exploring the uncertainties associated with Ra-derived water ages and eddy diffusion coefficients, this study will enable researchers to apply these methods more effectively and to reduce uncertainty.

The four naturally-occurring isotopes of radium were coupled with a previously evaluated hydrodynamic model to determine the apparent age of surface waters and to quantify submarine groundwater discharge (SGD) into the Venice Lagoon, Italy. Mean apparent age of water in the Venice Lagoon was calculated using the ratio of 224Ra to 228Ra determined from 30 monitoring stations and a mean pore water end member. Average apparent age was calculated to be 6.0 d using Ra ratios. This calculated age was very similar to average residence time calculated for the same period using a hydrodynamic model (5.8 d). A mass balance of Ra was accomplished by quantifying each of the sources and sinks of Ra in the lagoon, with the unknown variable being attributed to SGD. Total SGD were calculated to be 4.1 +/- 1.5, 3.8 +/- 0.7, 3.0 +/- 1.3, and 3.5 +/- 1.0 x 10(10) L d(-1) for (223,224,226, 228)Ra, respectively, which are an order of magnitude larger than total mean fluvial discharge into the Venice Lagoon (3.1 x 10(9) L d(-1)). The SGD as a source of nutrients in the Venice Lagoon is also discussed and, though significant to the nutrient budget, is likely to be less important as the dominant control on SGD is recirculated seawater rather than freshwater.

11 pages, 8 figures, 3 tables, Submarine groundwater discharge (SGD) was investigated at El Gorguel Bay (Cartagena-La Unión Pb–Zn mining district, Murcia, Spain), a Mediterranean region where mine tailings have been accumulated for decades at the shoreline. At this site, groundwater may become enriched in metals prior to discharge to the coastal sea and may lead to significant releases that can contaminate the coastal environment. The distribution of dissolved metals and Ra isotopes were studied in seawater and groundwater samples collected during the summer season in 2013. Cross-shore gradients of 224Ra in the bay allowed the calculation of a SGD flow of (39 ± 14) 103 m3 day−1. SGD-driven metal fluxes were 47–180 mol day−1 km− 1 for Zn, 0.20–0.60 mol day− 1 km− 1 for Pb, 4–32 mol day− 1 km− 1 for Fe, 0.8–2.3 mol day− 1 km− 1 for Cu and 0.9–2.8 mol day− 1 km− 1 for Ni. Compared to other coastal zones not affected by mining activities, SGD-driven metal fluxes were especially significant for dissolved Zn and Pb. The magnitude of these SGD-driven metal fluxes indicates that SGD is a relevant pathway in delivering metals to the coastal environment at El Gorguel Bay. This fact highlights the importance of investigating the role of SGD as a possible source of contamination to the sea in mining districts located in the proximity of the coast., This project has been partially funded by the European Union Seventh Framework Programme, Marie Curie Actions, through the MetTrans Initial Training Network, which also provide financial support through a PhD fellowship to G.T. (EU FP7-People-2011-ITN-290336). The research has been funded partially also by the Spanish Government project NUREIEV (CTM2013-44598-R). Support from the CSIC, under the program JAE-Doc (Junta para la Ampliación de Estudios) co-funded by the Fondo Social Europeo (FSE) is acknowledged for the post-doctoral fellowship (JAEDOC038) to J.S.-E. V.R. was supported through a Ph.D. fellowship (AP2008-03044) from the Spanish Government. A Beatriu de Pinós Postdoctoral fellowship from the Generalitat de Catalunya (2011BP-B00225) and a post-doctoral grant (FPDI-2013-15660) from the Spanish Government to E.G.-S. are also acknowledged. P.M. was supported in part by a Gledden Visiting Fellowship awarded by the Institute of Advanced Studies at The University of Western Australia. The support of the Generalitat de Catalunya to MERS (2014 SGR — 1356) is also acknowledged.

© 2014 American Chemical Society. Submarine groundwater discharge (SGD) and derived nutrient (NO2 -, NO3 -, NH4 +, PO4 3-, and SiO2) and trace element (Cd, Co, Cu, Fe, Mo, Ni, Pb, V and Zn) loadings to the coastal sea were systematically assessed along the coast of Majorca Island, Spain, in a general survey around the island and in three representative coves during 2010. We estimated that brackish water discharges through the shoreline are important contributors to the DIN, SiO2, Fe, and Zn budgets of the nearshore waters. Furthermore, our results showed that SGD-derived elements are conditioned by the hydrogeological formations of the aquifer and discharge type. Thus, while rapid discharges through karstic conduits are enriched in SiO2 and Zn, the large detrital aquifers of the island typically present enhanced concentrations of Fe. The estimated total annual inputs of chemicals constituents discharged by SGD to the coastal waters were as follows: DIN: 610 × 103 kg yr-1, SiO2: 1400 × 103 kg yr-1, Fe: 3.2 × 103 kg yr-1, and Zn: 2.0 × 103 kg yr-1. Our results provide evidence that SGD is a major contributor to the dissolved pool of inorganic nutrients and trace metals in the nearshore waters of Majorca., This research has been funded by the Spanish Government projects EDASE (ref CGL2008-00047/BTE) and GRADIENTS (CTM2012-39476-C02-01). D.S.-Q. was supported by the JAE-predoc program of the Spanish National Research Council (CSIC). V.R. was supported through a Ph.D. fellowship (AP2008-03044) from MICINN (Spain). P.M. was partially supported by the ICREA Academia prize, funded by the Generalitat de Catalunya. Authors want to thank the support of the Generalitat de Catalunya to MERS (2014 SGR − 1356).

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Moreno, Victoria Garcia-Solsona, Ester Masque, Pere Masque, Pere/B-7379-2008 Masque, Pere/0000-0002-1789-320X Spanish Government project EDASMAR [CGL2006-09274/HID]; Consejo de Seguridad Nuclear project [2686-SRA]; MICINN (Spain) [AP2008-03044]; ICREA Academia; Generalitat de Catalunya The authors would like to thank the assistance in field and laboratory work from our colleagues at the Laboratori de Radioactivitat Ambiental (Universitat de Barcelona). This project has been funded partially by the Spanish Government project EDASMAR (Ref. CGL2006-09274/HID) and the Consejo de Seguridad Nuclear project (Ref. 2686-SRA). V.R. acknowledges financial support through a PhD fellowship (AP2008-03044) from MICINN (Spain). Support for the research of PM was received through the prize ICREA Academia, funded by the Generalitat de Catalunya. We also want to thank the collaboration of Anna Cherta, Maribel Forner (Hotel Marina), Camping Eden, FACSA, School "Jaume Sainz" and the Peniscola Municipality. We want also to thank Gerard Carmona and Lluis Benejam for their support during fish sampling. 1 ELSEVIER SCIENCE BV AMSTERDAM MAR CHEM SI; Submarine groundwater discharge (SGD) has attracted the interest from the scientific community over the past decade for its impact on biogeochemical cycles of coastal ecosystems and/or management of water resources. SGD is associated with a flow of natural radionuclides (Ra isotopes and Rn-222), which are often used as SGD tracers that can significantly increase the natural background radiation. Although in many circumstances the discharge is produced directly to the sea and therefore the increase of natural radioactivity levels can generally be considered negligible due to a dilution processes, the discharge into coastal wetlands (marshes, coastal lagoons or ponds), with somewhat restricted exchange with the open sea, may require a detailed study of the distribution of natural radionuclides and their effects on the coastal ecosystem. The Peniscola marsh is a Mediterranean coastal wetland where such studies may be of special interest because it is fed exclusively by groundwater, mainly discharging from a deep aquifer with high natural radioactivity content. In the Peniscola marsh, brackish groundwater discharging through the wetland sediments is enriched in radionuclides to maximum values of 2.8 and 616 kBq m(-3) of Ra-226 and Rn-222, respectively. These high dissolved concentrations result in high levels of Rn-222 in air (up to 36 Bq m(-3)) and Pb-210 and Po-210 dissolved in water (20 and 5.7 Bq m(-3), respectively). These elevated levels of natural radionuclides in the Peniscola marsh are also responsible of the significant increase in Po-210 and Pb-210 contents in both fish and plants. (C) 2013 Elsevier B.V. All rights reserved.

A multiproxy approach of complementary techniques is applied to localise and quantify submarine groundwater discharge (SGD) from El Maestrazgo Jurassic aquifer, an example of widespread carbonate coastal aquifer of the Western Mediterranean Sea (Castellón, Spain). Unconventional water resources are critical in this area where highly populated resorts have been developed. The aquifer has two main features of particular interest: a karstic system with a deep saturated zone reaching 450 m and with no significant surface discharge occurring within the continental area. On the other hand, SGD can alter the condition of coastal marine environments, reducing salinities and providing nutrients that can cause eutrophication and algal blooms. The applied combined techniques make it possible to detect groundwater outflows using airborne thermal infrared (TIR) images to monitor physico-chemical anomalies in the sea and to quantify the submarine groundwater discharges by means of direct measurements and radium isotopic analyses. Three main coastal areas affected by SGD and a submarine spring located at 3 km from the coast, which seems to be associated with tectonic discontinuities, were localised. The calculated fresh SGD from Ra isotopes, 375 Mm3 y−1, is in agreement with the mean aquifer recharge obtained by hydrogeological methods, 394 Mm3 y−1., Instituto Geológico y Minero de España, España, Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, España, Departament de Física, Universitat Autònoma de Barcelona, España, Laboratoire d’Etudes en Géophysique et Océanographie Spatiales, Francia

Groundwater discharge constitutes the main water inflow of many coastal wetlands. Despite the potential of Ra isotopes and 222Rn as tracers of groundwater discharge, the use of these radionuclides to quantify the groundwater inflow in coastal wetlands has been only scarcely addressed in the literature. The main goal of this study is to evaluate the use of 222Rn and Ra isotopes to estimate the contribution of distinct groundwater sources into a Mediterranean coastal wetland (the Peníscola marsh, Castelló, Spain). The Peníscola marsh is a small shallow wetland nourished by groundwater coming from four different flowpaths: (i) a deep flow from the regional carbonate aquifer of El Maestrat, (ii) a shallow flow and (iii) an intermediate flow, both from the Irta Range and the detritic Vinaròs-Peníscola aquifer, and (iv) seawater intrusion. Data on 226Ra, 222Rn and salinity obtained in summer 2007 revealed that the deep groundwater contribution was 15% of the total water inflow, whereas the shallow and intermediate flow paths represented 32% and 48%, respectively. Seawater accounted only for the remaining 5% inputs to the wetland. Ra isotopes also allowed estimating the marsh water age in 1.2 days. Both the groundwater contributions derived from 222Rn measurements and the Ra-derived marsh water age agreed well with the direct measurements obtained using propeller flow meters, evidencing the effectiveness of the used methods. An interannual comparison between the estimated groundwater inflow and the precipitation revealed that shallow groundwater flows respond to local precipitation, whereas the deep groundwater flow from the carbonate aquifer is dominated by a constant baseflow, Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, España, Departament de Física, Universitat Autònoma de Barcelona, España, Laboratoire d’Etudes en Géophysique et Océanographie Spatiales, Francia, Instituto Geológico y Minero de España, España, Departament de Geologia, Universitat Autònoma de Barcelona, España

19 pages, 6 figures, 3 tables, Short and long-lived radium isotopes (223Ra, 224Ra, 226Ra, 228Ra) were used to quantify submarine groundwater discharge (SGD) and its associated input of inorganic nitrogen (NO3 −), phosphorus (PO4 3−) and silica (SiO4 4−) into the karstic Alcalfar Cove, a coastal region of Minorca Island (Western Mediterranean Sea). Cove water, seawater and groundwater (wells and karstic springs) samples were collected in May 2005 and February 2006 for radium isotopes and in November 2007 for dissolved inorganic nutrients. Salinity profiles in cove waters suggested that SGD is derived from shallow brackish springs that formed a buoyant surface fresh layer of only 0.3 m depth. A binary mixing model that considers the distribution of radium activities was used to determine the cove water composition. Results showed that cove waters contained 20% brackish groundwater; of which 6% was recirculated seawater and 14% corresponded to freshwater discharge. Using a radium-derived residence time of 2.4 days, a total SGD flux of 150,000 m3 year−1 was calculated, consisting of 45,000 m3 year−1 recirculated seawater and 105,000 m3 year−1 fresh groundwater. Fresh SGD fluxes of NO3 −, SiO4 4− and PO4 3− were estimated to be on the order of 18,000, 1,140 and 4 μmol m−2 day−1, respectively, and presumably sustain the high phytoplankton biomass observed in the cove during summer. The total amount of NO3 − and SiO4 4− supplied by SGD was higher than the measured inventories in the cove, while the reverse was true for PO4 3−. These discrepancies are likely due to non-conservative biogeochemical processes that occur within the subterranean estuary and Alcalfar Cove waters, This project has been partially supported by the Institut Menorquí d’Estudis (IME) and the Departament d’Universitats, Recerca i Societat de la Informació of the Generalitat de Catalunya (PICS program no. 2434). Support from the Spanish Government and the Fulbright Commission for a post-doctoral fellowship to J.G.-O. (ref 2007-0516) is gratefully acknowledged. Support for the research of PM was received through the prize “ICREA Academia”, funded by the Generalitat de Catalunya