Spatial and temporal distribution of pollution indices in marine surface sediments-a chemometric approach.

Concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn, and Fe measured at forty locations in the Boka Kotorska Bay were used to monitor the spatial and temporal quality of sediment and to assess surface sediment contamination over the last 15 years. This ecological geochemistry assessment was made using two classes of pollution indices: single indices concerning the investigated elements (contamination factor (Cf)) and integrated indices concerning the locations (pollution load index (PLI), potential ecological risk index (RI), mean effects range median quotient (MERMQ), toxic risk index (TRI), contamination severity index (CSI)). The distribution of all indices was geostatistically mapped and several hotspots were identified. Based on the indices applied in the risk assessment, the mean contribution of individual metal species to the total risk was determined and presented in the following order: Cd > Hg > As > Pb > Ni > Cu > Cr > Zn. This study revealed that Cd and Hg were at the top of the risk list among the examined elements. The temporal distribution of Hg has shown a decreasing trend during the period 2005-2019, while the presence of Cd in the Bay environment is of major concern. The results revealed that the most polluted part of the investigated area was Tivat bay within the Boka Kotorska Bay. Multivariate statistical analysis of pollution indices resulted in multicollinearity, which enabled the use of a reduced number of indices with an acceptable risk estimation.

Human and environmental factors affecting the activity of 131I and 137Cs in urban wastewater: A case study.

The analysis of radionuclides content in the waste product of urban wastewater treatment (i.e. sewage sludges) is of great concern for both the safety of workers and in a re-use perspective of the final product. The study of the behavior and the partitioning of radionuclides into sewage sludge samples can be useful not only to determine engineering issues in removal efficiency of radioactive pollutants, but also to determine the factors affecting the content and trends of radionuclides (natural and artificial) in urban wastewater systems. In this study we determine people-related and environmental factors that affect the activity of 131I (nuclear medicine) and 137Cs (fallout) in urban wastewater in a large area of northern Italy. 624 sewage sludge samples coming from 17 wastewater treatment plants were collected between 2012 and 2017 and analyzed with high resolution gamma-spectrometry. In addition to 131I and 137Cs, also the following radionuclides were analyzed for the periodic monitoring: 7Be, 40K, 60Co, 67Ga, 111In, 125I, 134Cs, 192Ir, 201Tl. 131I is the most frequently detected artificial radionuclide in sewage sludge samples (56%), showing a large variability (mean activity ±â€¯standard deviation 93 ±â€¯184 Bq kg-1). The detection frequency of this radionuclide is significantly correlated to population density (R = 0.75, p-value<0.01) and its activity concentration is significantly correlated to wastewater treatment plant size, expressed in population equivalents (R = -0.56, p-value<0.05). The detection frequency of 131I in sewage sludge samples is modeled as a function of population density, sewer length, inflow rates and population equivalents, accounting for 83% of the variability of observations. Despite the frequency of detection, the activity of 131I was relevant for workers safety only in less than 0.5% of the cases. On the other hand, 137Cs is detected in 36% of samples and its activity shows high correlation with mean annual precipitation (R = 0.67, p-value<0.01) and the activity of natural radionuclides (R = 0.58 and 0.63, for 7Be and 40K, respectively, p-values <0.05). With a hybrid geostatistical model, we demonstrate that the spatial pattern of 137Cs activity in wastewater estimated from sewage sludge samples is consistent with soil contamination from Chernobyl fallout. Moreover, we hypothesize a possible horizontal transport of 137Cs in the study area highlighted by different trends of 137Cs activity concentration in sludges. The results of this study depict the sensitivity of sewage sludges to the persistent contamination of 137Cs, after 30 years from Chernobyl accident, and can be used as a database for future monitoring activities after any accident that includes the spreading of radioactive materials into the environment.

Radioactivity measurements and dosimetric evaluation in meat of wild birds.

The aim of this study was to determine the background activity concentration of natural radionuclides and 137Cesium (Cs) in meat of 14 migratory birds originating from central and northern Europe. This meat is largely consumed by the Italian population. 40K, 210Pb, and 137Cs were determined by gamma spectrometry and 210Po by alpha spectrometry. The mean 40K activity concentration detected was 490 ± 117 Bq/kgdw. In all the samples, 210Pb was below the limit of detection (LOD), and therefore it was not possible to calculate the ratio 210Po/210Pb. The 210Po activity concentration ranged between 0.11 ± 0.02 Bq/kgdw and 6.2 ± 0.93 Bq/kgdw with a mean value of 1.03 ± 1.75 Bq/kgdw. The 137Cs activity concentration was not detectable or near LOD except in two samples with 45 ± 0.7 Bq/kgdw (wood pigeon, from Italy) and 139.1 ± 1.9 Bq/kgdw (woodcock, from Sweden). The effective dose of 210Po ingested by consumption of wild birds meat accounts for only 0.01-0.6% of natural radiation exposure in Italy. These data indicate that the meat analyzed was safe.

Radiochemical Characterization of Algae Products Commercialized for Human Consumption.

Natural radionuclides and Cs were determined by alpha (U, U, Th,Po,Th, and Th) and gamma spectrometry (Cs, K, Ra, Pb, and Ra via Ac) in 14 dried seaweeds commercialized for human nutrition in Italy. The study was carried out in order to provide information on the concentrations of natural and artificial radionuclides. Cesium-137 (Cs) concentrations in all analyzed samples were always <2.0 Bq kg (dry weight), while the naturally occurring radionuclide concentrations were detectable in all the samples and significantly different in the analyzed seaweeds. Potassium-40 (K) showed a mean activity of 894 Bq kg with a range of 14.1-3,256 Bq kg. The mean of activity for Po was 5.1 Bq kg with a range of 1.5-13.6 Bq kg. The mean of activity for Pb was 8.9 Bq kg with a range of 2.9-25.7 Bq kg. The mean of U and Ra activity concentration was 4.7 and 8.4 Bq kg with a range of 0.1-27.7 and 3.2-24.6 Bq kg, respectively. The mean activity concentrations for Th, Th, and Ra were 0.69, 3.0, and 6.6 Bq kg with ranges of 0.05-3.39, 0.24-15.7, and 0.5-35.6 Bq kg, respectively. Radionuclide activity concentrations were within ranges reported in the scientific literature. The committed effective dose due to all the radionuclides analyzed, from ingestion of 1 kg y of seaweeds, accounts for 0.66% of the natural radiation exposure in Italy.

Use of natural radionuclides to determine the time range of the accidental melting of an orphan radioactive source in a steel recycling plant.

In the rare event that an orphan radioactive source is melted in an Electric Arc Furnace steel recycling plant, the radionuclides present are partitioned in the different products, by-products and waste. As a consequence of an unforeseen melting of a radiocesium source, cesium radioisotopes can be found in the dust, together with many natural radionuclides from the decay of radon and thoron, which are present in the atmosphere, picked up from the off-gas evacuation system and associated with the dust of the air filtration system ("baghouse"). In this work we verified that the activity concentration of ²¹²Pb in this dust is essentially constant in a specific factory so that it is possible to use it to date back to the time of the accidental melting of the orphan radioactive source. The main features of this method are described below, together with the application to a particular case in which this method was used for dating the moment in which the dust was contaminated with ¹³7Cs.