Certified reference material IAEA-418: 129I in Mediterranean Sea water

A certified reference material designed for the determination of 129I in seawater, IAEA-418 (Mediterranean Sea water) is described and the results of certification are presented. The median of 129I concentration with 95% confidence interval was chosen as the most reliable estimates of the true value. The median, given as the certified value, is 2.28 × 108 atom L−1 (95% confidence interval is (2.16–2.73) 108 atom L−1), or 3.19 × 10−7 Bq L−1 (95% confidence interval is (3.02–3.82) × 10−7 Bq L−1). The material is intended to be used for standardization procedures applied in accelerator mass spectrometric laboratories. It is available in 1 L units and may be ordered via IAEA web side (www.iaea.org).The IAEA is grateful for the support provided to its Marine Environment Laboratories by the Government of the Principality of Monaco. PPP acknowledges a support provided by the EU Research & Development Operational Program funded by the ERDF (project No. 26240220004).Peer reviewe

Disentangling the geologic, human and climate drivers influencing sediment deposition in volcanic lakes on the Azores Archipelago

IAL-IPA joint meeting "Lakes as Memories of the Landscape", Patagonia, Argentina, 27 November-01 December 2022The Azores Archipelago Western (AAWG) and Central (AACG) groups present a high diversity of tectono-volcanic settings, and, therefore, a wide range of lake-watershed system morphometries. This archipelago has suffered from anthropic impacts, mainly abrupt land-use changes, since medieval times (between 700 and 850 CE), and increasingly after the Portuguese arrival in the 15th century. In this complex geologic and human context, we used a multiproxy approach in sediment records from Lakes Caldeirão (Corvo Island), Funda (Flores Island), and Caveiro (Pico Island) to demonstrate a complex interlinking among several environmental drivers over the last millennia. Paleoenvironmental changes have been defined by a multivariate analysis of sedimentary facies, biogeochemical and mineralogical data. This analysis highlights that the most prominent sedimentary process in the AAWG lakes (Caldeirao and Funda) is hydrological grain size sorting, driven by runoff. Additionally, smooth catchment slopes of the low-gradient lake, Caldeirão, modulated this process by favouring rock grain size diminution through weathering, whereas the steep topographic-bathymetric profile of the high-gradient lake, Funda, do through water-level fluctuations. The frequent volcanic activity of the AACG and the small size of Caveiro lake catchment favoured the deposit of pyroclastic tephra through direct fallout in the lake, over the catchment-sourced inputs, reworked by climate and tectonic activity. The biogeochemical and mineral composition of the sedimentary records present extreme change rates at 1288+28-22-1388+41-32 CE, corresponding with the age of the most intense landscape transformation. Therefore, to obtain robust climate reconstructions from these Azorean lacustrine records, we present a detailed statistical approach to isolate the climate signal from volcano-tectonic, morphometric, and anthropic driversThis research was funded by the Spanish Ministry of Economy and Competitiveness research projects PaleoNAO (CGL2010-15767), RapidNAO (CGL2013-40608-R), PaleoModes (CGL2016-75281-C2), and NEOCLIM (PID2020-113798GB-C33), and through Portuguese Science Foundation (FCT) (DL57/2016/ICETA/EEC2018/25) and the DISCOVERAZORES (PTDC/CTA-AMB/28511/2017)N

Simultaneous determination of radium and uranium activities in natural water samples using liquid scintillation counting Analyst

The determination of radium and/or uranium concentrations in natural waters is useful in a wide range of environmental studies. In this work, a low-background liquid scintillation system (Wallac, Quantulus 1220) was used to determine simultaneously 226 Ra and uranium (total) activities in natural water samples. Sample preparation involved filtration and 1 : 10 concentration by evaporation. Then, 8 ml of the sample were mixed with 12 ml of OptiPhase Hisafe 3 scintillation cocktail in low-diffusion vials. These were stored for 1 month before counting in order to ensure secular equilibrium between radium and its daughters. For a counting time of only 360 min, the detection limits achieved were 0.014 and 0.033 Bq l 21 for 226 Ra and uranium, respectively. In order to test the method, several Ebro river water samples were analysed by both liquid scintillation and a sensitive fluorimetric technique. Keywords: Environmental radioactivity; liquid scintillation counting; uranium; radium; natural water The determination of radium and uranium activities in natural waters is useful for a wide range of environmental studies such as the determination of radiological water quality, 1,2 geochemical studies, 3,4 uranium mining and ore processing, 5 and contamination by phosphate fertiliser industries. 6 Numerous methods are available for the determination of radium In the proposed method, secular equilibrium of 226 Ra and its daughters is required, which is attained by storing for 1 month after sample preparation. Radium activity was determined through 214 Po using an efficiency calibration curve, and uranium (total) activity was obtained from radium subtraction of the alpha spectrum. This method does not provide spectral information on uranium isotopes and, therefore, is mostly suitable for rough radiological surveys. A similar technique was proposed by Salonen 14 which was successfully validated with drinking water samples from Finland which showed high activity (total uranium: 0-1000 Bq l 21 ). However, important differences can be found with our work: samples are not evaporated to dryness, only one measurement is necessary, 214 Po is determined with better precision, a comparison of results is made with fluorimetry and validation samples showed lower activity ( < 1 Bq l 21 ). In order to test the proposed method, radium and uranium activities in Ebro River waters were determined. Uranium activities were compared with activities determined through uranium mass concentration using a fluorimetric method. Experimental Equipment A Quantulus 1220 low-level liquid scintillation system (Wallac, Turku, Finland) was used. It is equipped with a pulse-shape analysis (PSA) circuit which permits the discrimination of pulses produced by alpha and beta radiation by comparing the area of the pulse tail after 50 ns from the start with its total area. Pulse shape discrimination is accomplished using a softwareadjustable parameter (PSA parameter) which can vary between 1 and 256. Sample measurements were carried out in 20 ml polyethylene low-diffusion vials from Zinsser (Maidenhead, Berks., UK). Water samples were filtered through Whatman 542 slow depth filters (Whatman International, Maidstone, UK). Fluorimetric determination of uranium mass concentrations in water was carried out with a Scintrex (Concord, Canada) UA-3 uranium analyser. Reagents Sample counting was carried out using the scintillation cocktail OptiPhase Hisafe 3 (Wallac). Solutions containing 241 Am (alpha emitter) and 32 P (high-energy beta emitter) were used to calculate the interference value. Small amounts of CCl 4 (Merck, Darmstadt, Germany) were used to quench the solutions. Samples collected for uranium fluorimetric determination were acidified with a drop of 65% nitric acid (Merck). Fluorimetric determination needed Fluran (Scintrex), water Analyst, February 1998, Vol. 123 (399-403) 399 purified with a Milli-Q-system (Millipore Bedford, MA, USA) and uranyl nitrate (Merck). Optimisation of the alpha-beta separation The optimisation of the alpha-beta separation was achieved by measuring separately 241 Am and 32 P and determining the total interference between both spectra for different PSA parameters. where t a is the alpha interference, defined as the fraction of alpha particles observed in the beta spectrum when an alpha emitter ( 241 Am) is measured, and t b is the beta interference, defined as the fraction of beta particles observed in the alpha spectrum when a high-energy beta emitter ( 32 P) is measured. We considered that the optimum PSA parameter was found when the total interference was minimal. For a fixed PSA parameter, and for the range of SQP(E) studied (780-815), it was observed that an increase in SQP(E) caused the beta interference to increase and the alpha interference to decrease, and a decrease in SQP(E) caused the beta interference to decrease and the alpha interference to increase. On the other hand, a quadratic dependence between total interference and PSA parameter was also observed for the range studied, namely from 90 to 150. Finally, a complete description of the total interference was obtained through the function t = f [PSA,SQP(E)], as shown in 1. For the quenching usually observed when measuring environmental samples, which ranged from 785 to 795, the minimum of total interference occurred for a PSA parameter of 117. However, this value is not critical, as the total interference was almost independent of quenching and PSA in that region. 2. The minimum total interference for the experimental conditions described above, that is, 8 ml of sample and 12 ml of the OptiPhase Hisafe 3 scintillation cocktail in Zinsser lowdiffusion vials, was 3.76 ± 0.19%. 3. It is almost impossible to obtain exact uniformity of SQP(E) in environmental samples. However, if the PSA parameter value was correctly chosen, variations of ten SQP(E) parameter units caused a change in the total interference of only 1%. 4. For a PSA parameter of 117, the alpha interference and beta interference expressed in % were t a = (30 ± 11) 3 10 2 2 (7.4 ± 2.9) 3 SQP(E) + (46 ± 18) 3 10 24 3 SQP(E) 2 r 2 = 0.953 (2) t b = (26.1 ± 2.1) 3 10 2 2 (6.74 ± 0.54) 3 SQP(E) + (43.5 ± 3.4) 3 10 24 3 SQP(E) 2 r 2 = 0.996 (3) These expressions were used to calculate radium and uranium activities. Sample preparation Sample preparation for the simultaneous determination of 226 Ra and uranium (total) activities in water samples using liquid scintillation counting is summarised below. Each water sample was filtered through a Whatman 542 filter. A test was carried out with Ebro river surface waters and showed that total alpha counts after filtering through Whatman 542 filter (1.32 ± 0.06 cpm) was identical with that obtained after using a Millipore 0.22 mm membrane filter (1.35 ± 0.06 cpm). Therefore, as a Whatman 542 filter is cheaper and faster, it was used in this work, although this aspect should be tested for each specific environment studied. Regarding sample acidification, its use depends on the objective of the study. When considering radiological surveys, the particulate and colloidal fractions should not be considered as they are removed during water treatment procedures. Acidification after sample filtration would bring most metals associated with colloids into solution. Furthermore, the presence of acids strongly enhances quenching in liquid scintillation, which should be avoided when using this technique. Therefore, sample acidification is not performed in the proposed method. After filtration, 100 ml of sample were evaporated to a final volume of 10 ml on a hot-plate and allowed to cool for a few minutes. A sample volume of 8 ml was mixed with 12 ml o

Heavy metals in particulate matter and sediments in the southern Barcelona sedimentation system (North-western Mediterranean)

19 pages, 9 figures, 5 tablesConcentrations of selected heavy metals (Cr, Cu, Ni, Pb and Zn) from surface sediments, suspended particulate matter and settling particles in the southern Barcelona continental margin were studied in order to evaluate the environmental impact of the anthropogenic metals discharged by the Llobregat River in this Mediterranean area. The temporal variation of heavy metals discharged by this river onto the continental shelf is clearly related to the river water flow. Part of the fine sediment and associated heavy metals transported by the Llobregat River during periods of low river flow accumulate on the river bed, and they are totally removed and discharged onto the Barcelona continental shelf during sporadic river water flow increases. Metals produce significant anomalies of chromium (X 2.5), copper (X 3.4) and zinc (X 3.7) in the surface sediments of the Llobregat prodelta and tend to be transported along the continental shelf following the mean flow. Metals associated with the finest suspended flocs transferred to the slope are controlled by the shelf-slope density front and are transported along slope by the general geostrophic current, instead of accumulating and becoming concentrated in the slope bottom sediments. Settling particulate matter collected in sediment traps on the Barcelona continental slope offshore of the shelf-slope front shows low heavy metal concentrations except in a few sediment trap samples that are significantly metal-enriched in chromium (X 4.5) and zinc (X 6.8). This enrichment is associated with very short and sporadic river flow increases and is only recorded inside the Foix submarine canyon, which acts as a preferential conduit for the shelf-slope sediment transferThis work received support from the projects AMB92-0251-CO2-01 and MAR96-1781-CO2-01 funded by the Comisión Interministerial de Ciencia y Tecnologı́a and the project MAS2-CT93-0053 funded by the EE

Transfer of matter and energy on European continental margins

Canals, Miquel ... et. al.-- Mediterranean Targeted Project (MTP) - EUROMARGE-NB Project, Contract MAS2-CT93-0053, Synthesis of Final Results.-- 38 pages, 21 figures, 4 tablesPeer Reviewe