Map of Havana Bay, with sampling station. 

Contexts in source publication

Context 1

... enclosed bay with a catchment area of about 68 km 2 . It is character- ized by a mean depth of 10 m, an area of 5.2 km 2 and a water mean residence time of 7-9 days [1]. The bay is an estuary with deltaic systems in the fluvial discharge zones of the Luyano and Martin Perez rivers, and the Tadeo, Matadero, Agua Dulce and San Nicolas streams (Fig. ...

Context 2

... February 2008, sediment cores were collected with an UWITEC corer avoiding dredged areas of the bay (Fig. 1). In order to optimize analytical time and resources, we chose the cores with the best likelihood to show good temporal record (section 1 of Supporting information). We sampled three sediment cores from the station B (23 • 08.107 ′′ N 82 • 20.043 ′′ ) at a water depth of 8 m ( Fig. 1): one core for radionuclides, metals and grain size ...

Context 3

... with an UWITEC corer avoiding dredged areas of the bay (Fig. 1). In order to optimize analytical time and resources, we chose the cores with the best likelihood to show good temporal record (section 1 of Supporting information). We sampled three sediment cores from the station B (23 • 08.107 ′′ N 82 • 20.043 ′′ ) at a water depth of 8 m ( Fig. 1): one core for radionuclides, metals and grain size analy- sis; one for organic pollutants (not reported here) and one was kept frozen for future analysis. The sediment core was vertically extruded and sliced into 1 cm sections. Each section was dried at 45 • C, sieved through a 1 cm sieve and homogenized. The mud con- tent in the ...

Context 4

... fast economical growth of Havana City. This one has become the most contaminated bay in the island [2]. In order to rehabilitate this marine ecosystem, several pollution-reduction measures have been implemented over the past decade. Reliable information about the input of pollutants to Havana Bay is however required for evaluating the impact of the environmental management practices. In the absence of long-term monitoring data, sedimentary records can provide retrospective information about the past inputs of pollutants into aquatic environments. Pollutants such as heavy metals often have a strong affinity for particle surfaces and, therefore, accumulate in the sediments. Hence, dated sediment profiles of major and trace elements can be used to obtain reliable information about the extent and history of pollution and sedimentary conditions [3–7]. The quantitative reconstruction of a contaminant input into an aquatic system requires a good sediment chronology. The most widely used method for dating recent marine and lacustrine sediments is based on the examination of 210 Pb profiles. The natural radionuclide 210 Pb ( T 1/2 = 22.23 yr) enters the aquatic environment mainly by atmospheric deposition; however it can be produced in situ, in the water column and the sediments, by decay of its precur- sor radionuclide 226 Ra ( T 1/2 = 1600 yr). The 210 Pb dating methods are based on the radioactive disequilibrium between the 210 Pb and 226 Ra [8,9]. 210 Pb has shown to be an ideal tracer for dating aquatic sediments deposited during the last 100–150 years, a period of time with significant environmental changes due to industrialization and population growth. 210 Pb dating should be always corroborated by an additional chronostratigraphic marker in the same sediment core [10,11]. Among the most commonly used time markers we find anthropogenic fallout radionuclides such as 137 Cs, 239,240 Pu or 241 Am [13]. The onset of anthropogenic radionuclides, originating from the atmospheric nuclear weapon tests (early 1950s) and their peak value in 1963 [12] have been widely used as time markers in numerous marine and lacustrine studies [13–15]. In this work we reconstructed the historical trends of pollutants entering the Havana Bay by analyzing their sediment concentration profiles. The chronology of the sediment core was based on the 210 Pb dating method. Due to the low levels of 137 Cs found in the sediments, the chronology was further validated with 239,240 Pu and 241 Am fallout radionuclides. Enrichment factors and fluxes of pollutants were used to describe the history of pollutions in this aquatic ecosystem. A full geochemical analysis was undertaken to look at possible impacts of changing catchment sources, diagenesis, and atmospheric contamination. The potential origin of the most important pollutants and the impact of the pollution-reduction measures taken to protect the Havana Bay ecosystem are also dis- cussed. Despite the large number of studies of pollution in coastal environments, only a few have been conducted in the Caribbean region. Hence, this study provides important information about pollution trends in a coastal ecosystem of this tropical region. Havana Bay (NW Cuba) is located aside Havana City, is a typical enclosed bay with a catchment area of about 68 km 2 . It is characterized by a mean depth of 10 m, an area of 5.2 km 2 and a water mean residence time of 7–9 days [1]. The bay is an estuary with deltaic systems in the fluvial discharge zones of the Luyano and Martin Perez rivers, and the Tadeo, Matadero, Agua Dulce and San Nicolas streams (Fig. 1). The population density, commercial and harbors activities in Havana City increased significantly since 1850. The city became a key transshipment point between Europe and America in the 19th century. Nowadays, the port of Havana receives about 50% of the ships arriving to the country. Agriculture and intensive forest exploitation in the bay catchment increased soil erosion and, therefore, sediment input to the Bay. Industrial activities began in the 1850s with the construction of oil refineries, electric power plants and gas production [2,16]. The area of Havana experienced a fast economical growth during the 20th century, with a high diversity of industries and commercial activities, and a large population growth that required massive urbanization (from 250,000 inhabitants in 1899 to 2.2 million inhabitants in 2001). The anarchic growth of many activities over the past 400 years has caused severe damages to the natural resources and facilities of the Havana Bay. The damages have been intensified by the lack of waste treatment facilities [2,17,18]. The bay receives contaminants from numerous sources such as an oil refinery, power stations, urban and industrial wastewaters, three shipyards, riverine and stream discharges, and atmospheric fallout [1]. In February 2008, sediment cores were collected with an UWITEC corer avoiding dredged areas of the bay (Fig. 1). In order to optimize analytical time and resources, we chose the cores with the best likelihood to show good temporal record (section 1 of Supporting information). We sampled three sediment cores from the station B (23 ◦ 08.107 ′′ N 82 ◦ 20.043 ′′ ) at a water depth of 8 m (Fig. 1): one core for radionuclides, metals and grain size analysis; one for organic pollutants (not reported here) and one was kept frozen for future analysis. The sediment core was vertically extruded and sliced into 1 cm sections. Each section was dried at 45 ◦ C, sieved through a 1 cm sieve and homogenized. The mud content in the sediments showed a slight decreasing trend from 15 cm depth to the surface. The sediments also showed a strong change in color at about 15 cm depth. Grain size was determined by standard methods of sieving and pipetting analysis [19]. Content of organic matter for each section was estimated by the loss on ignition method (LOI: 450 ◦ C, for 8 h). The content of total carbon and nitrogen was measured by using a CHN analyzer (LECO TRUSPEC). Total carbon was measured as CO 2 with an infrared detector. N 2 was measured by using a thermal conductivity detector. Inorganic carbon was quantified by using an infrared detector (SSM-500, Shimadzu) after sample acidification with phosphoric acid and heating (200 ◦ C). Major and trace elements were measured by Wavelength Dispersion X-Ray Fluorescence Spectrometry (WDXRF) using a Panalytical system (AXIOS) with Rhodium tube. Total mercury concentrations were determined by using an Advanced Mercury Analyser (LECO AMA- 254, detection limit of 0.01 ng Hg). The chronology of the sediment cores was determined by the 210 Pb method (section 2.3 of Supporting information). Sediment samples were placed in sealed plastic containers and stored for at least three weeks in order to allow 226 Ra to reach equilibrium with its daughter nuclides. 226 Ra was then analysed by high-resolution gamma spectrometry, using a low-background intrinsic Ge coax- ial detector ORTEC model GX10022. 226 Ra was determined via the 352 keV emitted by its daughter nuclide 214 Pb in equilibrium. Supported 210 Pb sup was derived from the assumption of equilibrium with 226 Ra. The total 210 Pb activity was determined by high-resolution ␣ spectrometry of its decay product 210 Po, assumed to be at equilibrium. Aliquots (0.5 g) of dry sediment were spiked with 209 Po as a yield tracer and dissolved by adding a mixture of 1:1:0.5 HNO 3 + HCl + HF using an analytical microwave system [20]. 210 Po was electrodeposited onto silver discs [21,22] and counting was done in an integrated Camberra alpha spectrometer with ion implanted planar silicon detectors (active area of 450 mm 2 ; and 18 keV of nominal resolution). The 210 Pb in excess ( 210 Pb ex ) to the 210 Pb supported by 226 Ra ( 210 Pb sup ) was determined by subtracting the 210 Pb sup from the total activity of 210 Pb measured in each layer. 210 Pb ex was then introduced in the models in order to obtain the sedimentation rate (section 2.3 of Supporting information). Measurements of 137 Cs, 239,240 Pu and 241 Am were used to vali- date the 210 Pb dating models. 137 Cs was measured via its emission at 662 keV by high-resolution gamma spectrometry. The sediment samples were then crushed and ashed at 550 ◦ C for 48 h prior to the radiochemical analyses of 239,240 Pu and 241 Am. Composite samples were prepared by mixing layers. The method combines high-pressure microwave digestion for the dissolution of the sample and the highly selective extraction chromatographic resins TEVA and DGA (Triskem International, France) for the separa- tion and purification of Pu and Am [23]. The alpha sources were prepared by electrodeposition onto stainless steel discs [24]. High- resolution ␣ -spectrometry was performed on a ␣ -spectrometer with PIPS detectors (Alpha Analyst, Canberra Electronic). The sediments are predominantly fine and displayed small variations in grain size in the overall samples (Fig. 2a). The sediments consisted mainly of clay (<4 ␮ m, 58–85%), and silt and very fine sand (>4 ␮ m, 15–42%) sized particles. In the upper 5 cm, the per- cent of silt and very fine to coarse sand sized particles increased slightly (Fig. 2a). The sediments were mainly composed of carbonates (11–45%) and aluminosilicates (40–80%). The mineral composition of the sediments did not change significantly from the bottom of the core up to 20 cm depth (Fig. 2b). However, from 20 cm depth up to the surface large variations were observed with the amount of carbonates correlating negatively to the amount of alumino-silicates (Fig. 2b). The amount of carbonates showed a general trend to decrease towards the surface, but it increased rapidly in the top 4 cm (Fig. 2b). The content of inorganic carbon ( C inorg ) in the sediments was almost constant along the whole core; but the organic carbon ( C org ) showed a surface maximum and then decreased with depth depict- ing two zones of ...

Context 5

... Bay is one of the largest and most important estuaries in the Cuban Island. The economic, commercial and recreational values of the bay have been, however, threatened by pollution and the reduction of water depth due to infilling [1]. The environmental degradation of the bay ecosystem has been intensified in the past decades due to the fast economical growth of Havana City. This one has become the most contaminated bay in the island [2]. In order to rehabilitate this marine ecosystem, several pollution-reduction measures have been implemented over the past decade. Reliable information about the input of pollutants to Havana Bay is however required for evaluating the impact of the environmental management practices. In the absence of long-term monitoring data, sedimentary records can provide retrospective information about the past inputs of pollutants into aquatic environments. Pollutants such as heavy metals often have a strong affinity for particle surfaces and, therefore, accumulate in the sediments. Hence, dated sediment profiles of major and trace elements can be used to obtain reliable information about the extent and history of pollution and sedimentary conditions [3–7]. The quantitative reconstruction of a contaminant input into an aquatic system requires a good sediment chronology. The most widely used method for dating recent marine and lacustrine sediments is based on the examination of 210 Pb profiles. The natural radionuclide 210 Pb ( T 1/2 = 22.23 yr) enters the aquatic environment mainly by atmospheric deposition; however it can be produced in situ, in the water column and the sediments, by decay of its precur- sor radionuclide 226 Ra ( T 1/2 = 1600 yr). The 210 Pb dating methods are based on the radioactive disequilibrium between the 210 Pb and 226 Ra [8,9]. 210 Pb has shown to be an ideal tracer for dating aquatic sediments deposited during the last 100–150 years, a period of time with significant environmental changes due to industrialization and population growth. 210 Pb dating should be always corroborated by an additional chronostratigraphic marker in the same sediment core [10,11]. Among the most commonly used time markers we find anthropogenic fallout radionuclides such as 137 Cs, 239,240 Pu or 241 Am [13]. The onset of anthropogenic radionuclides, originating from the atmospheric nuclear weapon tests (early 1950s) and their peak value in 1963 [12] have been widely used as time markers in numerous marine and lacustrine studies [13–15]. In this work we reconstructed the historical trends of pollutants entering the Havana Bay by analyzing their sediment concentration profiles. The chronology of the sediment core was based on the 210 Pb dating method. Due to the low levels of 137 Cs found in the sediments, the chronology was further validated with 239,240 Pu and 241 Am fallout radionuclides. Enrichment factors and fluxes of pollutants were used to describe the history of pollutions in this aquatic ecosystem. A full geochemical analysis was undertaken to look at possible impacts of changing catchment sources, diagenesis, and atmospheric contamination. The potential origin of the most important pollutants and the impact of the pollution-reduction measures taken to protect the Havana Bay ecosystem are also dis- cussed. Despite the large number of studies of pollution in coastal environments, only a few have been conducted in the Caribbean region. Hence, this study provides important information about pollution trends in a coastal ecosystem of this tropical region. Havana Bay (NW Cuba) is located aside Havana City, is a typical enclosed bay with a catchment area of about 68 km 2 . It is characterized by a mean depth of 10 m, an area of 5.2 km 2 and a water mean residence time of 7–9 days [1]. The bay is an estuary with deltaic systems in the fluvial discharge zones of the Luyano and Martin Perez rivers, and the Tadeo, Matadero, Agua Dulce and San Nicolas streams (Fig. 1). The population density, commercial and harbors activities in Havana City increased significantly since 1850. The city became a key transshipment point between Europe and America in the 19th century. Nowadays, the port of Havana receives about 50% of the ships arriving to the country. Agriculture and intensive forest exploitation in the bay catchment increased soil erosion and, therefore, sediment input to the Bay. Industrial activities began in the 1850s with the construction of oil refineries, electric power plants and gas production [2,16]. The area of Havana experienced a fast economical growth during the 20th century, with a high diversity of industries and commercial activities, and a large population growth that required massive urbanization (from 250,000 inhabitants in 1899 to 2.2 million inhabitants in 2001). The anarchic growth of many activities over the past 400 years has caused severe damages to the natural resources and facilities of the Havana Bay. The damages have been intensified by the lack of waste treatment facilities [2,17,18]. The bay receives contaminants from numerous sources such as an oil refinery, power stations, urban and industrial wastewaters, three shipyards, riverine and stream discharges, and atmospheric fallout [1]. In February 2008, sediment cores were collected with an UWITEC corer avoiding dredged areas of the bay (Fig. 1). In order to optimize analytical time and resources, we chose the cores with the best likelihood to show good temporal record (section 1 of Supporting information). We sampled three sediment cores from the station B (23 ◦ 08.107 ′′ N 82 ◦ 20.043 ′′ ) at a water depth of 8 m (Fig. 1): one core for radionuclides, metals and grain size analysis; one for organic pollutants (not reported here) and one was kept frozen for future analysis. The sediment core was vertically extruded and sliced into 1 cm sections. Each section was dried at 45 ◦ C, sieved through a 1 cm sieve and homogenized. The mud content in the sediments showed a slight decreasing trend from 15 cm depth to the surface. The sediments also showed a strong change in color at about 15 cm depth. Grain size was determined by standard methods of sieving and pipetting analysis [19]. Content of organic matter for each section was estimated by the loss on ignition method (LOI: 450 ◦ C, for 8 h). The content of total carbon and nitrogen was measured by using a CHN analyzer (LECO TRUSPEC). Total carbon was measured as CO 2 with an infrared detector. N 2 was measured by using a thermal conductivity detector. Inorganic carbon was quantified by using an infrared detector (SSM-500, Shimadzu) after sample acidification with phosphoric acid and heating (200 ◦ C). Major and trace elements were measured by Wavelength Dispersion X-Ray Fluorescence Spectrometry (WDXRF) using a Panalytical system (AXIOS) with Rhodium tube. Total mercury concentrations were determined by using an Advanced Mercury Analyser (LECO AMA- 254, detection limit of 0.01 ng Hg). The chronology of the sediment cores was determined by the 210 Pb method (section 2.3 of Supporting information). Sediment samples were placed in sealed plastic containers and stored for at least three weeks in order to allow 226 Ra to reach equilibrium with its daughter nuclides. 226 Ra was then analysed by high-resolution gamma spectrometry, using a low-background intrinsic Ge coax- ial detector ORTEC model GX10022. 226 Ra was determined via the 352 keV emitted by its daughter nuclide 214 Pb in equilibrium. Supported 210 Pb sup was derived from the assumption of equilibrium with 226 Ra. The total 210 Pb activity was determined by high-resolution ␣ spectrometry of its decay product 210 Po, assumed to be at equilibrium. Aliquots (0.5 g) of dry sediment were spiked with 209 Po as a yield tracer and dissolved by adding a mixture of 1:1:0.5 HNO 3 + HCl + HF using an analytical microwave system [20]. 210 Po was electrodeposited onto silver discs [21,22] and counting was done in an integrated Camberra alpha spectrometer with ion implanted planar silicon detectors (active area of 450 mm 2 ; and 18 keV of nominal resolution). The 210 Pb in excess ( 210 Pb ex ) to the 210 Pb supported by 226 Ra ( 210 Pb sup ) was determined by subtracting the 210 Pb sup from the total activity of 210 Pb measured in each layer. 210 Pb ex was then introduced in the models in order to obtain the sedimentation rate (section 2.3 of Supporting information). Measurements of 137 Cs, 239,240 Pu and 241 Am were used to vali- date the 210 Pb dating models. 137 Cs was measured via its emission at 662 keV by high-resolution gamma spectrometry. The sediment samples were then crushed and ashed at 550 ◦ C for 48 h prior to the radiochemical analyses of 239,240 Pu and 241 Am. Composite samples were prepared by mixing layers. The method combines high-pressure microwave digestion for the dissolution of the sample and the highly selective extraction chromatographic resins TEVA and DGA (Triskem ...

Context 6

... to Havana Bay is however required for evaluating the impact of the environmental management practices. In the absence of long-term monitoring data, sedimentary records can provide retrospective information about the past inputs of pollutants into aquatic environments. Pollutants such as heavy metals often have a strong affinity for particle surfaces and, therefore, accumulate in the sediments. Hence, dated sediment profiles of major and trace elements can be used to obtain reliable information about the extent and history of pollution and sedimentary conditions [3–7]. The quantitative reconstruction of a contaminant input into an aquatic system requires a good sediment chronology. The most widely used method for dating recent marine and lacustrine sediments is based on the examination of 210 Pb profiles. The natural radionuclide 210 Pb ( T 1/2 = 22.23 yr) enters the aquatic environment mainly by atmospheric deposition; however it can be produced in situ, in the water column and the sediments, by decay of its precur- sor radionuclide 226 Ra ( T 1/2 = 1600 yr). The 210 Pb dating methods are based on the radioactive disequilibrium between the 210 Pb and 226 Ra [8,9]. 210 Pb has shown to be an ideal tracer for dating aquatic sediments deposited during the last 100–150 years, a period of time with significant environmental changes due to industrialization and population growth. 210 Pb dating should be always corroborated by an additional chronostratigraphic marker in the same sediment core [10,11]. Among the most commonly used time markers we find anthropogenic fallout radionuclides such as 137 Cs, 239,240 Pu or 241 Am [13]. The onset of anthropogenic radionuclides, originating from the atmospheric nuclear weapon tests (early 1950s) and their peak value in 1963 [12] have been widely used as time markers in numerous marine and lacustrine studies [13–15]. In this work we reconstructed the historical trends of pollutants entering the Havana Bay by analyzing their sediment concentration profiles. The chronology of the sediment core was based on the 210 Pb dating method. Due to the low levels of 137 Cs found in the sediments, the chronology was further validated with 239,240 Pu and 241 Am fallout radionuclides. Enrichment factors and fluxes of pollutants were used to describe the history of pollutions in this aquatic ecosystem. A full geochemical analysis was undertaken to look at possible impacts of changing catchment sources, diagenesis, and atmospheric contamination. The potential origin of the most important pollutants and the impact of the pollution-reduction measures taken to protect the Havana Bay ecosystem are also dis- cussed. Despite the large number of studies of pollution in coastal environments, only a few have been conducted in the Caribbean region. Hence, this study provides important information about pollution trends in a coastal ecosystem of this tropical region. Havana Bay (NW Cuba) is located aside Havana City, is a typical enclosed bay with a catchment area of about 68 km 2 . It is characterized by a mean depth of 10 m, an area of 5.2 km 2 and a water mean residence time of 7–9 days [1]. The bay is an estuary with deltaic systems in the fluvial discharge zones of the Luyano and Martin Perez rivers, and the Tadeo, Matadero, Agua Dulce and San Nicolas streams (Fig. 1). The population density, commercial and harbors activities in Havana City increased significantly since 1850. The city became a key transshipment point between Europe and America in the 19th century. Nowadays, the port of Havana receives about 50% of the ships arriving to the country. Agriculture and intensive forest exploitation in the bay catchment increased soil erosion and, therefore, sediment input to the Bay. Industrial activities began in the 1850s with the construction of oil refineries, electric power plants and gas production [2,16]. The area of Havana experienced a fast economical growth during the 20th century, with a high diversity of industries and commercial activities, and a large population growth that required massive urbanization (from 250,000 inhabitants in 1899 to 2.2 million inhabitants in 2001). The anarchic growth of many activities over the past 400 years has caused severe damages to the natural resources and facilities of the Havana Bay. The damages have been intensified by the lack of waste treatment facilities [2,17,18]. The bay receives contaminants from numerous sources such as an oil refinery, power stations, urban and industrial wastewaters, three shipyards, riverine and stream discharges, and atmospheric fallout [1]. In February 2008, sediment cores were collected with an UWITEC corer avoiding dredged areas of the bay (Fig. 1). In order to optimize analytical time and resources, we chose the cores with the best likelihood to show good temporal record (section 1 of Supporting information). We sampled three sediment cores from the station B (23 ◦ 08.107 ′′ N 82 ◦ 20.043 ′′ ) at a water depth of 8 m (Fig. 1): one core for radionuclides, metals and grain size analysis; one for organic pollutants (not reported here) and one was kept frozen for future analysis. The sediment core was vertically extruded and sliced into 1 cm sections. Each section was dried at 45 ◦ C, sieved through a 1 cm sieve and homogenized. The mud content in the sediments showed a slight decreasing trend from 15 cm depth to the surface. The sediments also showed a strong change in color at about 15 cm depth. Grain size was determined by standard methods of sieving and pipetting analysis [19]. Content of organic matter for each section was estimated by the loss on ignition method (LOI: 450 ◦ C, for 8 h). The content of total carbon and nitrogen was measured by using a CHN analyzer (LECO TRUSPEC). Total carbon was measured as CO 2 with an infrared detector. N 2 was measured by using a thermal conductivity detector. Inorganic carbon was quantified by using an infrared detector (SSM-500, Shimadzu) after sample acidification with phosphoric acid and heating (200 ◦ C). Major and trace elements were measured by Wavelength Dispersion X-Ray Fluorescence Spectrometry (WDXRF) using a Panalytical system (AXIOS) with Rhodium tube. Total mercury concentrations were determined by using an Advanced Mercury Analyser (LECO AMA- 254, detection limit of 0.01 ng Hg). The chronology of the sediment cores was determined by the 210 Pb method (section 2.3 of Supporting information). Sediment samples were placed in sealed plastic containers and stored for at least three weeks in order to allow 226 Ra to reach equilibrium with its daughter nuclides. 226 Ra was then analysed by high-resolution gamma spectrometry, using a low-background intrinsic Ge coax- ial detector ORTEC model GX10022. 226 Ra was determined via the 352 keV emitted by its daughter nuclide 214 Pb in equilibrium. Supported 210 Pb sup was derived from the assumption of equilibrium with 226 Ra. The total 210 Pb activity was determined by high-resolution ␣ spectrometry of its decay product 210 Po, assumed to be at equilibrium. Aliquots (0.5 g) of dry sediment were spiked with 209 Po as a yield tracer and dissolved by adding a mixture of 1:1:0.5 HNO 3 + HCl + HF using an analytical microwave system [20]. 210 Po was electrodeposited onto silver discs [21,22] and counting was done in an integrated Camberra alpha spectrometer with ion implanted planar silicon detectors (active area of 450 mm 2 ; and 18 keV of nominal resolution). The 210 Pb in excess ( 210 Pb ex ) to the 210 Pb supported by 226 Ra ( 210 Pb sup ) was determined by subtracting the 210 Pb sup from the total activity of 210 Pb measured in each layer. 210 Pb ex was then introduced in the models in order to obtain the sedimentation rate (section 2.3 of Supporting information). Measurements of 137 Cs, 239,240 Pu and 241 Am were used to vali- date the 210 Pb dating models. 137 Cs was measured via its emission at 662 keV by high-resolution gamma spectrometry. The sediment samples were then crushed and ashed at 550 ◦ C for 48 h prior to the radiochemical analyses of 239,240 Pu and 241 Am. Composite samples were prepared by mixing layers. The method combines high-pressure microwave digestion for the dissolution of the sample and the highly selective extraction chromatographic resins TEVA and DGA (Triskem International, France) for the separa- tion and purification of Pu and Am [23]. The alpha sources were prepared by electrodeposition onto stainless steel discs [24]. High- resolution ␣ -spectrometry was performed on a ␣ -spectrometer with PIPS detectors (Alpha Analyst, Canberra Electronic). The sediments are predominantly fine and displayed small variations in grain size in the overall samples (Fig. 2a). The sediments consisted mainly of clay (<4 ␮ m, 58–85%), and silt and very fine sand (>4 ␮ m, 15–42%) sized particles. In the upper 5 cm, the per- cent of silt and very fine to coarse sand sized particles increased slightly (Fig. 2a). The sediments were mainly composed of carbonates (11–45%) and aluminosilicates (40–80%). The mineral composition of the sediments did not change significantly from the bottom of the core up to 20 cm depth (Fig. 2b). However, from 20 cm depth up to the surface large variations were observed with the amount of carbonates correlating negatively to the amount of alumino-silicates (Fig. 2b). The amount of carbonates showed a general trend to decrease towards the surface, but it increased rapidly in the top 4 cm (Fig. 2b). The content of inorganic carbon ( C inorg ) in the sediments was almost constant along the whole core; but the organic carbon ( C org ) showed a surface maximum and then decreased with depth depict- ing two zones of rapid change (at 2–3 cm, and at 16–17 cm depth; Fig. 2c). The large percentage of C org in the top 2–3 cm may be related to a change in the sources of organic matter, more com- plex and less biodegradable, typical of industrial organic wastes. However, the increase of organic matter may ...