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The production of dicalcium phosphate (DCP) uses phosphate rock (PR) as a raw material. Sedimentary phosphate rocks are enriched with relevant concentrations of natural radionuclides from the 238 U decay chain (around 10 3 Bq·kg −1 ), leading to the need of controlling potential exposures to radiation of workers and members of the public in accordance with IAEA safety standards. Indeed, phosphate industries are classified as Naturally Occurring Radioactive Material (NORM) industries. Thus, the aim of this work is to assess the radiological risk of the workers in a DCP production plant located in the Iberian Peninsula (South-West Europe), which digests PR with hydrochloric acid. In the present study 238 U, 230 Th, 222 Rn, 210 Pb and 210 Po concentrations in aerosols (indoor and outdoor areas) are reported. Aerosols showed concentrations between 0.42–92 mBq·m −3 for 238 U, 0.24–33 mBq·m −3 for 230 Th, 0.67–147 mBq·m −3 for 210 Pb and 0.09–34 mBq·m −3 for 210 Po. Long-term exposure (four months) of passive 222 Rn detectors provided concentrations that ranged from detection limit (< DL) to 121 Bq·m -3 in outdoor areas and from < DL to 211 Bq·m −3 in indoor areas, similar to concentrations obtained from short-term measurements with active detectors from < DL to 117 Bq·m −3 in outdoor areas and from < DL to 318 Bq·m −3 in indoor places. 226 Ra accumulation in ebonite and pipe scales were the most important contributions to the ambient dose equivalent H*(10), resulting in 0.07 (background)–27 μSv·h −1 with a median value of 1.1 μSv·h −1 . Average 222 Rn air concentrations were lower than the 300 Bq·m −3 limit and therefore, according to European Directive 2013/59/EURATOM, 222 Rn concentration is excluded from the worker operational annual effective dose. Thus, considering the inhalation of aerosols and the external dose sources, the total effective dose determined for plant operators was 0.37 mSv·y −1 . [ABSTRACT FROM AUTHOR]

This study presents the results of the accumulation of 210 Po and 210 Pb in fish tissues and organs in a brackish-water marshland that is characterized by high concentrations of 222 Rn and 226 Ra supplied by submarine groundwater discharge (SGD). Tissues and organs from Cyprinus carpio , Chelon labrosus and Carassius auratus in the wetland were significantly enriched by both 210 Pb and 210 Po (up to 55 and 66 times, respectively) compared to blanks. The major input route of 210 Pb and 210 Po into the fish body seems to be through ingestion, due to the high levels of 210 Pb and 210 Po found in the gut content as well as in organs involved in digestion and metabolism (i.e. gut, kidney and hepatopancreas). Results showed that 210 Po was more accumulated in all fish tissues and organs except for the spine, which showed a higher affinity for 210 Pb, due to its capacity to replace Ca from apatite in bones. Over all the variables analyzed, fish tissues/organs and, secondarily, fish species were the most important factors explaining the concentration of radionuclides, whereas fish length and the sampling location played a minor role. The relationship of the two radionuclides varied markedly among tissues and their concentration levels were only correlated in gills, gut and, marginally, in spines. In general, the highest values of 210 Pb and 210 Po concentrations in tissues were found on C. labrosus tissues rather C. auratus and C. carpio . This study demonstrates that inputs of natural radionuclides supplied by SGD to coastal semi-enclosed areas (such as marshlands, lagoons or ponds) may significantly increase the contents of 210 Pb and 210 Po in fish tissues/organs. Thus, this study represents one of the first evidences of direct ecological effects derived from SGD. [ABSTRACT FROM AUTHOR]

The approach to quantify submarine groundwater discharge using Ra isotopes generally involves developing a Ra mass balance in an estuary, bay or lagoon. In this work we present a 224 Ra mass balance used to evaluate the importance of the submarine groundwater discharge (SGD) in Long Island Sound (NY, US), the third most important estuary in US, located between Long Island and Connecticut that is usually affected by summertime hypoxia in the western basin. Three surveys were conducted between April 2009 and August 2010 where 25 water stations were sampled for Ra isotopes, oxygen and Mn. Stations were oriented along 4 transects: one axial extending from the western to the eastern Sound and three longitudinal transects in the western, central and eastern Sound. The inventory of 224 Ra in the water column in summer was circa 2 times greater than in winter, suggesting an increased 224 Ra flux to the Sound in summer. A mass balance for 224 Ra was constructed considering tidal exchange, inputs from rivers, desorption from resuspended particles, diffusive fluxes (including bioirrigation) from bottom sediments and radioactive decay in the water column. Fluxes of 224 Ra from bottom sediments were measured by incubating cores under oxic conditions in a continuous flow mode such that the overlying water was circulated through a Mn-oxide fiber to maintain a constant activity of 224 Ra. Fluxes from muddy sediments (comprising ∼67% of the Sound bottom) ranged from 127 to 312 dpm m −2 d −1 and were ∼60 dpm m −2 d −1 in sandy sediments (33% of the Sound). Incubations under hypoxic conditions showed variable fluxes depending on reduction and mobilization of Mn. The 224 Ra mass balance shows a net input of Ra to the Sound of 106 ± 50 × 10 12 dpm y −1 in spring and 244 ± 112 × 10 12 dpm y −1 in the summer that is attributed to SGD. Elevated 224 Ra values were observed near shore and in the pore fluids of the coarse beach sands along the Long Island and Connecticut coasts, suggesting that SGD driven by tidal recirculation through the beach face is a major source of 224 Ra to the Sound. Seasonal variation in this source seems unlikely, and the calculated 224 Ra SGD fluxes for spring and summer overlap within the uncertainties. Nevertheless we conclude that variations in the 224 Ra water column inventories could be produced by seasonal changes in bioirrigation and/or redox cycling of Mn as well as sediment resuspension and desorption of 224 Ra from resuspended particles, and that our mass balance underestimates these terms, particularly in the summer. 224 Ra fluxes from sediments in estuaries, especially those with significant areas of muddy sediments and seasonal hypoxia, are important and should be well constrained in future uses of this isotope as a tracer for SGD. [ABSTRACT FROM AUTHOR]

Abstract: Ra isotopes are a powerful tool for quantifying the flux of submarine groundwater discharge (SGD) into the sea. Previous studies of 223Ra and 224Ra mass balances in coastal embayments have shown that the Ra balance is dominated by supply via SGD, exchange with the open ocean and radioactive decay. The current study shows that a single time series over a tidal cycle at the principal inlet to Great South Bay (NY, US) is sufficient to determine the net flux of Ra across the inlet, and also can be used to estimate the decay of short-lived Ra in the bay. Estimates of the net Ra flux obtained from a single tidal time-series by using three different approaches agree with those determined from a more time-consuming survey of Ra within the bay, and may represent a first step of estimating SGD in bays and coastal lagoons. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Artificial radionuclides enter the Mediterranean Sea mainly through atmospheric deposition following nuclear weapons tests and the Chernobyl accident, but also through the river discharge of nuclear facility effluents. Previous studies of artificial radionuclides impact of the Mediterranean Sea have focussed on shallow, coastal sediments. However, deep sea sediments have the potential to store and accumulate pollutants, including artificial radionuclides. Deep sea marine sediment cores were collected from Mediterranean Sea abyssal plains (depth >2000 m) and analysed for 239,240Pu and 137Cs to elucidate the concentrations, inventories and sources of these radionuclides in the deepest areas of the Mediterranean. The activity — depth profiles of 210Pb, together with 14C dating, indicate that sediment mixing redistributes the artificial radionuclides within the first 2.5 cm of the sedimentary column. The excess 210Pb inventory was used to normalize 239,240Pu and 137Cs inventories for variable sediment fluxes. The 239,240Pu/210Pb xs ratio was uniform across the entire sea, with a mean value of 1.24×10−3, indicating homogeneous fallout of 239,240Pu. The 137Cs/210Pb xs ratio showed differences between the eastern (0.049) and western basins (0.030), clearly significant impact of deep sea sediments from the Chernobyl accident. The inventory ratios of 239,240Pu/137Cs were 0.041 and 0.025 in the western and eastern basins respectively, greater than the fallout ratio, 0.021, showing more efficient scavenging of 239,240Pu in the water column and major sedimentation of 137Cs in the eastern basin. Although areas with water depths of >2000 m constitute around 40% of the entire Mediterranean basin, the sediments in these regions only contained 2.7% of the 239,240Pu and 0.95% of the 137Cs deposited across the Sea in 2000. These data show that the accumulation of artificial radionuclides in deep Mediterranean environments is much lower than predicted by other studies from the analysis of continental shelf sediments. [Copyright &y& Elsevier]

Abstract: The short-lived radium isotopes, 223Ra (T 1/2 =11.4 days) and 224Ra (T 1/2 =3.66 days), have been successfully used as tracers of several environmental processes, e.g., submarine groundwater discharge, coastal mixing processes, and water residence times. In this paper, the uncertainties associated with 223Ra and 224Ra measurements using a Radium Delayed Coincidence Counter are determined on a detailed error propagation basis with a confidence interval of 1σ. From the data analyses of several groups of coastal water samples, the calculated relative uncertainties averaged 12% for the 223Ra and 7% for the 224Ra. These uncertainties can decrease for radium-enriched groundwater samples although asymptotic limits have been found at 7% relative uncertainty for 223Ra and 4% for 224Ra. In this paper, the influence of sampling and measurement parameters on the final radium uncertainties is evaluated in order to provide guidance to optimize these factors and obtain more reliable results. [Copyright &y& Elsevier]

Submarine groundwater discharge (SGD) is now recognized as an important process of the hydrological cycle worldwide and plays a major role as a conveyor of dissolved compounds to the ocean. Naturally occurring radium isotopes (223Ra, 224Ra, 226Ra and 228Ra) are widely employed geochemical tracers in marine environments. Whilst Ra isotopes were initially predominantly applied to study open ocean processes and fluxes across the continental margins, their most common application in the marine environment has undoubtedly become the identification and quantification of SGD. This review focuses on the application of Ra isotopes as tracers of SGD and associated inputs of water and solutes to the coastal ocean. In addition, we review i) the processes controlling Ra enrichment and depletion in coastal groundwater and seawater; ii) the systematics applied to estimate SGD using Ra isotopes and iii) we summarize additional applications of Ra isotopes in groundwater and marine studies. We also provide some considerations that will help refine SGD estimates and identify the critical knowledge gaps and research needs related to the current use of Ra isotopes as SGD tracers. [ABSTRACT FROM AUTHOR]

Abstract: The production of dicalcium phosphate (DCP) is part of the phosphate industry, which has been recently included in the positive list of the NORM industries defined in the revised version of the EU-BSS (Euratom 29/96). The objective of the present work is to study specific concentrations and fluxes of 238,234U, 230Th, 226Ra, 210Pb and 210Po at the different stages of the DCP production. Results showed highest activities of 238U and 210Pb were found in DCP (1500–2000Bqkg−1); 230Th and 210Po were released together with the sludges (1600–2000Bqkg−1) and 226Ra presented particularly high activities in water (48×103 Bqm−3) and in the reactor scales (115×103 Bqkg−1). Fluxes of radionuclides showed that 238U outflows were equally distributed between sludges (16×103 kBqh−1) and dicalcium phosphate (20×103 kBqh−1); 230Th and 210Po were almost entirely released in the sludges (30×103 kBqh−1) and the greatest 210Pb outflow was the DCP current (25×103 kBqh−1). 226Ra was mainly discharged through the water effluent (12×103 kBqh−1). This work highlights the importance of studying the industrial processes involving NORM, as minor changes in the production steps lead to different radionuclide distribution in the process. [Copyright &y& Elsevier]

Abstract: Since the 1950s, nuclear weapon testing and releases from the nuclear industry have introduced anthropogenic radionuclides into the sea, and in many instances their ultimate fate are the bottom sediments. The Arctic Ocean is one of the most polluted in this respect, because, in addition to global fallout, it is impacted by regional fallout from nuclear weapon testing, and indirectly by releases from nuclear reprocessing facilities and nuclear accidents. Sea-ice formed in the shallow continental shelves incorporate sediments with variable concentrations of anthropogenic radionuclides that are transported through the Arctic Ocean and are finally released in the melting areas. In this work, we present the results of anthropogenic radionuclide analyses of sea-ice sediments (SIS) collected on five cruises from different Arctic regions and combine them with a database including prior measurements of these radionuclides in SIS. The distribution of 137Cs and 239,240Pu activities and the 240Pu/239Pu atom ratio in SIS showed geographical differences, in agreement with the two main sea ice drift patterns derived from the mean field of sea-ice motion, the Transpolar Drift and Beaufort Gyre, with the Fram Strait as the main ablation area. A direct comparison of data measured in SIS samples against those reported for the potential source regions permits identification of the regions from which sea ice incorporates sediments. The 240Pu/239Pu atom ratio in SIS may be used to discern the origin of sea ice from the Kara–Laptev Sea and the Alaskan shelf. However, if the 240Pu/239Pu atom ratio is similar to global fallout, it does not provide a unique diagnostic indicator of the source area, and in such cases, the source of SIS can be constrained with a combination of the 137Cs and 239,240Pu activities. Therefore, these anthropogenic radionuclides can be used in many instances to determine the geographical source area of sea-ice. [Copyright &y& Elsevier]

Abstract: Potentially harmful phosphate-based products derived from the wet acid digestion of phosphate rock represent one of the most serious problems facing the phosphate industry. This is particularly true for dicalcium phosphate (DCP), a food additive produced from either sulphuric acid or hydrochloric acid digestion of raw rock material. This study determined the natural occurring radionuclide concentrations of 12 DCP samples and 4 tricalcium phosphate (TCP) samples used for animal and human consumption, respectively. Metal concentrations (Al, Fe, Zn, Cd, Cr, As, Hg, Pb and Mg) were also determined. Samples were grouped into three different clusters (A, B, C) based on their radionuclide content. Whereas group A is characterized by high activities of 238U, 234U (∼103 Bqkg−1), 210Pb (2×103 Bqkg−1) and 210Po (∼800Bqkg−1); group B presents high activities of 238U, 234U and 230Th (∼103 Bqkg−1). Group C was characterized by very low activities of all radionuclides (<50Bqkg−1). Differences between the two groups of DCP samples for animal consumption (groups A and B) were related to the wet acid digestion method used, with group A samples produced from hydrochloric acid digestion, and group B samples produced using sulphuric acid. Group C includes more purified samples required for human consumption. High radionuclide concentrations in some DCP samples (reaching 2×103 and 103 Bqkg−1 of 210Pb and 210Po, respectively) may be of concern due to direct or indirect radiological exposure via ingestion. Our experimental results based on 210Pb and 210Po within poultry consumed by humans, suggest that the maximum radiological doses are 11±2μSvy−1. While these results suggest that human health risks are small, additional testing should be conducted. [Copyright &y& Elsevier]

Abstract: The four naturally-occurring radium isotopes (223Ra, 224Ra, 226Ra and 228Ra) were used to estimate the submarine groundwater discharge (SGD) in the Isola La Cura marsh area in the northern Venice Lagoon (Italy). By determining the radium contributors to the study area (river, coastal ocean and sediments) the radium excess in the lagoon water was quantified through a mass balance model. This radium excess is attributed to a submarine groundwater discharge source and represents the most important input of radium. Possible endmembers were considered from analysis of groundwater samples (subtidal and marsh piezometers, marsh wells and seepage meters) that were enriched in Ra by one to two orders of magnitude relative to surface waters. In particular, a permeable layer at 80 cm depth in the surrounding marsh is considered to be representative of the most likely SGD source, although similar radium activities were measured in other subtidal porewater samples collected in the Isola La Cura area. The estimated SGD flux to the study area ranged from 1·109 to 6·109 L·d−1, the same order of magnitude as the overall riverine input to the lagoon (3·109 L·d−1). A major fraction of this SGD flux is likely recirculated seawater, as evidenced by the endmember salinity. The water residence time of 2 days was estimated by both using the shortest-lived radium isotope and estimating the volume of water exchanged between the lagoon and the open sea during a tidal cycle (tidal prism approach). This SGD flux could be used to estimate the input of other chemical species (metals, nutrients, etc.) via SGD which might affect the Venice Lagoon ecosystem. [Copyright &y& Elsevier]

The first basin-wide distribution of 236 U/ 238 U atom ratios and 129 I concentrations is presented for the Mediterranean Sea. During the GEOTRACES GA04S-MedSeA expedition in 2013 seawater was collected from 10 vertical profiles covering the principal sub–basins of the Mediterranean Sea. The main objective was to understand the distributions of 236 U and 129 I in relation to the water masses, and to constrain their sources in this region. The 236 U/ 238 U atom ratios and the 129 I concentrations ranged from (710 ± 40) × 10 − 12 to (2220 ± 60) × 10 − 12 and from (4.0 ± 0.1) × 10 7 to (13.8 ± 0.3) × 10 7 at·kg − 1 , respectively. The results show that radionuclide–poor Atlantic Water is entering at the surface through the Strait of Gibraltar whereas comparably radionuclide-enriched Levantine Intermediate Water is sinking in the Eastern Basin and flowing westward at intermediate depths. Low radionuclide levels were found in the oldest water masses at about 1000–2000 m depth in the Eastern Basin. At greater depths, waters were relatively enriched in 236 U and 129 I due to dense water formation occurring in both, the Eastern and Western Basins. The inventories of 236 U and 129 I cannot be explained only by global fallout from atmospheric nuclear bomb testings carried out in the 1950s and 1960s. We estimate that the liquid input of 236 U from the nuclear reprocessing facility of Marcoule (France), via the Rhône river, was of the same order of magnitude than the contribution from global fallout, whereas liquid and gaseous releases of 129 I from Marcoule were up to two orders of magnitude higher than global fallout. For both radionuclides, the contribution from the Chernobyl accident is found to be minor. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the spatio-temporal variability of phytoplankton in aquaculture zones is necessary for the prevention and/or prediction of harmful algal bloom events. Synoptic cruises, time series analyses of physical and biological parameters, and 3D modeling were combined to investigate the variability of phytoplankton biomass in Alfacs Bay at basin scale. This microtidal estuary located in the NW Mediterranean is an important area of shellfish and finfish exploitation, which is regularly affected by toxic outbreaks. Observations showed the existence of a preferential phytoplankton accumulation area on the NE interior of the bay. This pattern can be observed throughout the year, and we show that it is directly linked to the physical forcing in the bay, in particular, the interplay between freshwater input and wind-induced turbulence. Both drivers affect the strength of the estuarine circulation, explaining nearly 75% of the variability in phytoplankton biomass. More cells are retained when stratification is weakened and the estuarine circulation reduced, while flushing rates are higher during times of increased stratification and stronger estuarine flow. This has been confirmed by using a 3D hydrodynamic model with Eulerian tracers. Nutrients, while important to support phytoplankton populations, have been found to play only a secondary role in explaining this variability at basin scale. [Copyright &y& Elsevier]

Abstract: This manuscript describes a protocol for the determination of U and Th isotopes via alpha spectrometry in NORM samples containing high concentrations of these radionuclides, up to kBqkg−1. This technique is based on extraction chromatography with UTEVA (Triskem Int.) resins and it has been tested using both NORM samples from a phosphate industry and reference materials. The results proved that this method is highly optimized in terms of accuracy and precision when dealing with NORM samples. Recycling of UTEVA columns was also checked using NORM samples and successful results were obtained for both U and Th isotopes, thus proving the feasibility of re-using these type of columns. [Copyright &y& Elsevier]

Abstract: Dicalcium phosphate (DCP) is used as a calcium supplement for food producing animals (i.e., cattle, poultry and pig). When DCP is produced via wet acid digestion of the phosphate rock and depending on the acid used in the industrial process, the final product can result in enhanced 210Pb and 210Po specific activities (∼2000Bq·kg− 1). Both 210Pb and 210Po are of great interest because their contribution to the dose received by ingestion is potentially large. The aims of this work are to examine the accumulation of 210Pb and 210Po in chicken tissues during the first 42days of life and to build a suitable single-compartment biokinetic model to understand the behavior of both radionuclides within the entire animal using the experimental results. Three commercial corn-soybean-based diets containing different amounts and sources of DCP were fed to broilers during a period of 42days. The results show that diets containing enhanced concentrations of 210Pb and 210Po lead to larger specific accumulation in broiler tissues compared to the blank diet. Radionuclides do not accumulate homogeneously within the animal body: 210Pb follows the calcium pathways to some extent and accumulates largely in bones, while 210Po accumulates to a large extent in liver and kidneys. However, the total amount of radionuclide accumulation in tissues is small compared to the amounts excreted in feces. The single-compartment non-linear biokinetic model proposed here for 210Pb and 210Po in the whole animal takes into account the size evolution and is self-consistent in that no fitting parameterization of intake and excretions rates is required. [ABSTRACT FROM AUTHOR]

Abstract: Common density/moisture gauges used in highway and construction industries are normally equipped with gamma and neutron sources, usually a 137Cs source of hundreds of MBq and an 241Am-Be source of the order of 1GBq, respectively. Operators of such devices are workers professionally exposed to ionizing radiation, subject to personal dosimetry. Gamma radiation personal doses received during operation, maintenance and transport are controlled by the officially authorised dosimetry centres using the appropriate dosemeters (typically TLD based dosemeters). Nevertheless, neutron personal dosimetry is generally not performed, as it is estimated that the neutron dose is small compared to the gamma dose. Ten units of the UAB PADC based neutron dosemeter have been distributed among workers involved in the transport and usage of the gauges of the Payma Cotas, S.A.U Company and have been collected after being exposed for two months. The neutron field outside a particular gauge has been characterised using the UAB active neutron spectrometer, based on Bonner spheres, and measurements with neutron and gamma monitors have been performed around the device itself and around its transport case. Results of this neutron field characterisation together with those of the neutron personal dosimetry, of the operators involved in the gauge transport and usage, are presented. [Copyright &y& Elsevier]

Abstract: A new Certified Reference Material (CRM) for radionuclides in sediment (IAEA-385) is described and the results of the certification process are presented. Eleven radionuclides (40K, 137Cs, 226Ra, 228Ra, 230Th, 232Th, 234U, 238U, 238Pu, 239+240Pu and 241Am) have been certified and information mass activities with 95% confidence intervals are given for seven other radionuclides (90Sr, 210Pb(210Po), 235U, 239Pu, 240Pu and 241Pu). Results for less frequently reported radionuclides (60Co, 99Tc, 134Cs, 155Eu, 224Ra and 239Np) and information on some activity and mass ratios are also reported. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in sediment samples, for the development and validation of analytical methods and for training purposes. [Copyright &y& Elsevier]

Abstract: Particle export from the upper waters of the oligotrophic ocean may play a crucial role in the global carbon cycle. Mesoscale eddies have been hypothesized to inject new nutrients into oligotrophic surface waters, thereby increasing new production and particle export in otherwise nutrient deficient regimes. The E-Flux Program was a large multidisciplinary project designed to investigate the physical, biological and biogeochemical characteristics of cold-core cyclonic eddies that form in the lee of the Hawaiian Islands. There, we investigated particle dynamics using 210Pb–210Po disequilibrium. Seawater samples for 210Pb and 210Po were collected both within (IN) and outside (OUT) of two cyclones, Noah and Opal, at different stages of their evolution as well as from the eddy generation region. Particulate carbon (PC), particulate nitrogen (PN) and biogenic silica (bSiO2) export fluxes were determined using water-column PC, PN, and bSiO2 inventories and the residence times of 210Po. PC and PN fluxes at 150m ranged from 1.58±0.10 to 1.71±0.16mmolCm−2 d−1 and 0.22±0.02 to 0.30±0.02mmolNm−2 d−1 within Cyclones Opal and Noah. PC and PN fluxes at OUT stations sampled during both cruises were of similar magnitudes, 1.69±0.16 to 1.67±0.16mmolCm−2 d−1 and 0.30±0.03 to 0.26±0.03mmolNm−2 d−1. The bSiO2 fluxes within Cyclone Opal were 0.157±0.010mmolSim−2 d−1 versus 0.025±0.002mmolSim−2 d−1 at OUT stations. These results of minimal PC and PN export, but significant eddy-induced bSiO2 fluxes, agree very well with other studies that used a variety of direct and indirect methods. Thus, our results suggest that using elemental inventories and residence times of 210Po is another independent and robust method for determining particle export and should be investigated more fully. [Copyright &y& Elsevier]

Abstract: In the frame of the EU-funded ADIOS project, the aim of this paper is to present the results of the total mass and the major constituent (organic matter, calcium carbonate, opal and lithogenics) fluxes obtained in the central part of the Algero–Balearic Basin (ABB). Two identical mooring lines, named A and B were equipped with three automated sediment traps and three current meters at 250 m, 1440 m and 2820 m of water depth, and another one, named C, was equipped with five sediment trap–current meter pairs at the corresponding depths of 250 m, 845 m, 1440 m, 2145 m and 2820 m. The samples were collected during an annual period, from April 2001 to May 2002 over sampling periods of 15–30 days. The presented particle fluxes data constitute the first one-year experimental study carried out in the open ABB, a region in which the continental inputs are expected to be minimums. This fact explains why the values of the mean annual fluxes were the lowest found in the whole Western Mediterranean Sea, ranging from 11.30 mg·m−2 day−1 (2145 m; station C) to 112.75 mg m−2 day−1 (250 m; station A). The temporal evolution of the particle fluxes in the upper waters shows the dominance of the atmospherically derived particles during summer and autumn, and a clear biological control during winter related to the primary productivity pathway. Along the whole water column, the calcium carbonate appears as the main relative contributor of the biogenic material (26%–30%), and the opal content presents the lowest values (6%–8%), suggesting that the study area is a carbonate-dominated ecosystem. Otherwise, even if the particles are derived from the atmosphere or internally produced by biological processes, it is clear that their transference from the upper to the deeper ocean is controlled by the stabilization of the water column and the distribution of the water masses in the Western Mediterranean Sea. In this context, the input of the Tyrrhenian Deep Water (TDW) into the AB7B at 800–1500 m of water depth strongly affects the distribution of the particle fluxes in the basin, being responsible of the minimum concentration zone at intermediate depths. Furthermore, current meter and flux data indicate a high influence of the Gulf of Lions water mass formation by spreading of dense cold water along the whole ABB, leading up to a maximum of particulate matter at depths higher than 2000 m. [Copyright &y& Elsevier]

• A new advective transport model is used to assess 224Ra/228Ra and 222Rn/226Ra ARs. • Alpha recoil supply and Ra retardation factor control ARs in groundwater. • ARs are used to estimate groundwater transit times in aquifers. • ARs are useful for evaluating discharge pathways and end-members of SGD. The naturally occurring Ra isotopes (223Ra; T 1/2 = 11.4 d, 224Ra; T 1/2 = 3.66 d, 226Ra; T 1/2 = 1,600 y, and 228Ra; T 1/2 = 5.7 y) and Rn (222Rn; T 1/2 = 3.82 d) have been widely applied as environmental tracers. The application of these radioactive tracers has mainly been restricted to the evaluation of oceanographic and land-ocean interaction processes, although in recent years their use has also been extended to the study of groundwater systems. In this context, the activity ratios of 224Ra/228Ra and 222Rn/226Ra can be instrumental in providing key information on groundwater transit times in aquifers and those processes governing groundwater discharge into the coastal sea (often referred to as Submarine Groundwater Discharge or SGD). This work evaluates the potential use of these activity ratios as proxies for investigating groundwater systems through an advective transport model that integrates the radionuclides involved in these activity ratios (224Ra, 228Ra, 226Ra, and 222Rn) and their immediate parents into a single formulation. The results provided by the transport model indicate that the main factors controlling the 224Ra/228Ra and 222Rn/226Ra activity ratios are the alpha recoil supply, the retardation factor of Ra, and the groundwater transit times. The advective transport model and the activity ratios are used to present novel applications that interrelate the disciplines of hydrogeology and coastal oceanography. The main applications include the determination of groundwater transit times and the assessment of pathways and end-members related to submarine groundwater discharge processes. These applications were tested in a Mediterranean coastal aquifer. [ABSTRACT FROM AUTHOR]

• A research site was built with 16 piezometers placed between 30 and 90 m from the shore. • New monitoring techniques were applied to improve coastal aquifers characterization. • CHERT allows a better definition of seawater intrusion than piezometers data. • The combination of these techniques allows a better spatial and temporal resolution. The characterization of saline water intrusion (SWI) and its hydrodynamics is a key issue to understand submarine groundwater discharge (SGD) and manage groundwater resources in coastal areas. To test and compare different methods of characterization and monitoring, a new experimental site has been constructed in a coastal alluvial aquifer north of Barcelona city (Catalonia, Spain). The site is located between 30 and 90 m from the seashore and comprises 16 shallow piezometers organized in nests of three with depths ranging between 15 and 25 m and 4 solitary piezometers. The objective of this paper is to combine different recently developed monitoring techniques to evaluate temporal variations in the aquifer hydrodynamics of the site at different spatial scales before and after the dry season of 2015. At the site scale, fibre optic distributed temperature sensing (FO-DTS), for the first time applied to study SWI, and cross-hole electrical resistivity tomography (CHERT) has been applied. At the meter/borehole scale, electrical conductivity of the formation has been applied not only in a repeated manner ("time lapse"), but also for the first time at relatively high frequency (1 sample every 10 min). CHERT has provided a better characterization of the seawater intrusion than electrical conductivity data obtained from piezometers. The combination of techniques has allowed improving the understanding of the system by: 1) characterizing the extent and shape of SWI; 2) differentiating two different dynamics in the aquifer; and 3) identifying preferential flow paths over different time and spatial intervals. Future challenges and the application of these techniques in other areas are also discussed. [ABSTRACT FROM AUTHOR]