Baseline radionuclide and heavy metal concentrations in sediments of Sabaki River estuary (Kenya, Indian Ocean).

Baseline study of natural (7Be, 210Pb, 226Ra, 234Th, 228Ra, 40K) and anthropogenic (137Cs) radionuclides was carried out in two cores collected from Sabaki River estuary (Kenya, Indian Ocean). There was no exponential decrease of excess 210Pb down the cores, which did not allow dating and determination of heavy metal pollution history. The use of 137Cs as a time marker was not possible due to its low fallout rates in East Africa. The short-lived radioisotope 7Be, a tracer of river floods, confirmed 2018 flood in Sabaki River estuary. Heavy metal concentration in the two cores showed nonsystematic trends with depth. Only Pb concentration in Sabaki River estuary was higher than the background levels. Application of the "Environmental Risk from Ionising Contaminants Assessment and management" (ERICA) tool confirmed that the potential dose rates to biota from the sediment radioactivity concentrations are unlikely to pose appreciable ecological risks.

Environmental radioactivity analyses in Italy following the Fukushima Dai-ichi nuclear accident.

Following the Fukushima power plants accident on the 11th March 2011, the radioactivity monitoring programme at the Italian ENEA research centres was activated in order to detect the possible new input of radionuclides through atmospheric transport and precipitation. Measurements of (131)I and (134,137)Cs were carried out on atmospheric particulate, atmospheric deposition, seawater and mussels and sheep milk. In the daily samples of air particulate, (131)I was detectable between March 28 and April 12, with extremely low concentrations (<1 mBq m(-3); the detection limit for (131)I was ~0.2 mBq m(-3)) while Cs isotopes were always below the detection limit (<0.2 mBq m(-3)). The two main episodes of (131)I atmospheric deposition were registered in La Spezia research centre, around March 28 and April 15, reaching values of 17.8 ± 1.1 and 8.0 ± 2.5 Bq m(-2) respectively; maximum values of (134)Cs and (137)Cs were 0.11 ± 0.03 and 0.17 ± 0.02 Bq m(-2), respectively, detected in Brasimone research centre in April (reference date April 15). Mussels and seawater were collected in the Gulf of La Spezia: only mussels after the main (131)I deposition, on March 28, contained a measurable, although very small, amount of (131)I (0.18 ± 0.05 Bq kg(-1), detection limit (131)I = 0.03 Bq kg(-1) wet weight - soft parts). The (131)I was also detected in sheep milk in Rome (Casaccia research centre) until May 5, showing a maximum concentration of 4.9 ± 0.4 Bq L(-1). As for other European Countries for which data are available, activity levels remain of no concern for public health.

Sediment reworking rates in deep sediments of the Mediterranean Sea.

Different pelagic areas of the Mediterranean Sea have been investigated in order to quantify physical and biological mixing processes in deep sea sediments. Herein, results of eleven sediment cores sampled at different deep areas (> 2000 m) of the Western and Eastern Mediterranean Sea are presented. ²¹°Pb(xs) and ¹³7Cs vertical profiles, together with ¹4C dating, are used to identify the main processes characterising the different areas and, finally, controlling mixing depths (SML) and bioturbation coefficients (D(b)). Radionuclide vertical profiles and inventories indicate that bioturbation processes are the dominant processes responsible for sediment reworking in deep sea environments. Results show significant differences in sediment mixing depths and bioturbation coefficients among areas of the Mediterranean Sea characterised by different trophic regimes. In particular, in the Oran Rise area, where the Almeria-Oran Front induces frequent phytoplankton blooms, we calculate the highest values of sediment mixing layers (13 cm) and bioturbation coefficients (0.187 cm² yr⁻¹), and the highest values of ²¹°Pb(xs) and ¹³7Cs inventories. Intermediate values of SML and D(b) (~6 cm and ~0.040 cm² yr⁻¹, respectively) characterise the mesothrophic Algero-Balearic basin, while in the Southern Tyrrhenian Sea mixing parameters (SML of 3 cm and D(b) of 0.011 cm² yr⁻¹ are similar to those calculated for the oligotrophic Eastern Mediterranean (SML of 2 cm and D(b) of ~0.005 cm² yr⁻¹).