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Scientific Activities

An integrated approach for the reconstruction of sediment contaminant history

 

SEDICON

PN-II-RU-TE-2014-4-1772 nr. 261/01.10.2015

           The proposed work plan and activities (As) envisage for a realistic and timely implementation of the project, and is given in compliance with the scientific objectives of the project.

A1: Expendable and equipment acquisition. All the necessary equipment and laboratory expendables (e.g. reagents, glassware, sample containers, tube cores) for the project implementation will be purchased in order to prepare the analytical laboratories for a large number of simultaneous radiometric, geochemical and physical measurements.

A2: Sediment core sampling and sediment samples handling. The sediment coring sites will be established precisely after the review of the cartographic material and field visits, so that to avoid sediments disturbed by regular storminess or human activities. Fieldwork campaign will be undertaken in two stages: July - August 2015 and May 2016, followed by frozen core cutting and sub-sampled every 1 or 2 cm. Sampling will be performed using specialized sediment core sampler which will enable the capture of up to 1.5 m long mud and sandy cores from up to 10 m depths. Four replicate sediment cores will be collected from each site, Snagov Lake and Balta Mică a Brăilei Natural Park, in order to obtain sufficient material for all proposed measurements to be done. Additionally, 4 replicate sediment cores will be extruded from Strachina Lake to distinguish between the contaminants originated from Danube river basin and the local pollutants. All cores are described and photographed, prior to preparation for analysis. In this stage samples will be also collected from the bottom layers of one sediment column for luminescence dating.

A3: Granulometry and organic carbon content. The water content and sediment porosity will be determined for each sediment sample in order to establish the mass sedimentation rate. Granulometry is then evaluated based on a combination of the hydrometer and the sieving methods, according to Romanian Standards (STAS 1913/5-85). First, 20-50 g of dry sediment will be weighed and sieved using the Retsch system. For the finest sediment (< 63μm), the particle size distribution will be obtained by measuring sedimentation time at different intervals. Organic C will be determined by loss-on-ignition (LOI) method, based on a modified method of Heiri et al. (2001).

A4: Radiometric dating.

A.4.1. Gamma-ray measurements. Cs-137, Pb-210 (only upper sediment layers, for checking the equilibrium status with Po-210) and Ra-226 activities in sediment will be determined by gamma spectrometry using HPGe Ortec detectors from host institution laboratories, calibrated in energy and efficiency (Iurian&Cosma, 2014b). Samples in aluminium containers will be sealed at least 3 weeks prior to counting, to allow equilibrium between Ra-226 and its short lived daughters. Quality assurance is regularly performed using IAEA reference materials (IAEA-375, IAEA-447) and through participation in worldwide proficiency tests (IAEA-TEL-2012-03) and intercomparisons.

A.4.2. Alpha spectrometry. The total Pb-210 activities are determined through the measurement of its daughter nuclide Po-210 by alpha spectrometry using Ortec detectors from the university laboratory. The radiochemical separation of Po-210 involves acid microwave digestion of 1.0 g sample and spontaneous deposition onto Stainless Steel discs. The chemical recovery is determined using Po-209 tracer. Quality assurance is performed using IAEA certified reference materials (IAEA-385) and through participation in worldwide proficiency tests (IAEA-TEL-2012-03).

A.4.3. Pb-210 and Cs-137 dating technique. The well-known radiometric dating model CRS which considers constant annual deposition rates of atmospheric Pb-210 (excess Pb-210) at a given location, while varying sedimentation rates, will be applied to obtain  recent chronologies (150 years) of sediment cores. Excess Pb-210 activities are determined by subtracting the Ra-226 activity (assumed to equal the supported Pb-210 activity) from the total Pb-210 content. The information given by Cs-137 will validate the sediment ages through an independent time marker.

A5: Hydrocarbons determination. PAHs and total hydrocarbons content in sediment are determined using the new GS-MS-PQ2010 at Environmental Health Centre accredited laboratory, and following EPA 8270D-2007 and internal validated methods. The high sensitivity of the instrumentation allows the simultaneous measurements of different compounds. The EPA method includes specific calibration and quality control steps (e.g. linearity criterion 20%).

A6: Metal concentrations analysis. Heavy metals analysis will be made using the AAS equipment from university laboratory and all elemental concentrations exceeding the detection limit will be reported. We will target heavy metals that are normally associated with industrial and mining activities (e.g. Pb, Cu, Zn, Cr, Cd) and lithogenic elements (e.g. Fe) that will allow enrichment factors for the anthropogenically-derived elements to be determined. Reproducibility, based upon replicate analysis, and reference materials measurements are also performed.

A7: Integrated approach. Possible sources of the PAHs emission into environment can be found through the use of indices, which are the ratio of concentrations of some PAHs in the sample (e.g. ratio between two- and three ring hydrocarbons and four- to six-ring hydrocarbon, reported to unit). The described state-of-art methods from A3, A4, A5, A6, A7 will be integrated with the historical hydrologic and land use data within SEDICON approach, as an original and novel tool for historical and contemporaneous pollution identification and quantification at local scale.

A8: Preparation of findings, reporting and publications. Intermediary and final project reports will be compiled, reflecting all steps performed, project results and main conclusions. Publications will be submitted to international peer-review journals and project results will be presented at target international conferences.