Effect of sewage sludge derived compost or biochar amendment on the phytoaccumulation of potentially toxic elements and radionuclides by Chinese cabbage.

This study set out to evaluate the effect of using sewage sludge-derived compost (SSC) or biochar (SSB) as a soil amendment on the phytoaccumulation of potentially toxic elements, PTE (Cd, Cr, Cu, Ni, Pb, Zn) and natural radionuclides (238U and 232Th) by Chinese cabbage (Brassica rapa L. subsp. pekinensis (Lour.) Hanelt) in terra rossa and rendzina soils, which are the two common soil types in Croatia. The experiment consisted of a greenhouse pot trial using a three-factor design where soil type, sludge post-stabilisation procedure and amendment rate (12 and 120 mgP/L) were the main factors. At harvest, the concentrations of analytes in the substrate, leaves and roots were measured, from which the edible tissue uptake (ETU) and concentration ratios (CR) were determined. Also, the average daily dose (ADD) and hazard quotient (HQ) were determined to assess the health risk, as well as soil contamination factor (CF). The results showed that neither adding SSC nor SSB affected the soil loading at the rates applied, suggesting a low risk of soil contamination (CF ≤ 1). The ETU of Cd, Cu, and Zn were 0.0061, 1.23, and 0.91 mg/plant from compost-amended soil and 0.0046, 0.78 and 0.65 mg/plant for biochar-amended soil, respectively. This difference suggests that their ETU was higher in compost-amended soils than in soils treated with biochar. The CR data indicate that the bioavailability of Cu (CR of 5.30) is highest at an amendment rate of 12 mgP/L, while for Zn (CR of 0.69), the highest bioaccumulation was observed with an amendment rate of 120 mgP/L. Translocation of Cr, Ni, Pb and 238U to the leaves was limited. Overall, the HQ (<1) for Cd, Cu and Zn in the edible parts confirmed that consuming Chinese cabbage does not threaten human health. Similarly, the daily intake of 232Th remained below the limit (3 µg) set by ICRP, suggesting no radiological risk. Finally, although the amendment rate, which was 10-times the amount stipulated in Croatian regulation and the CR ranged from 0.007 to 5.30, the precautionary principle is advised, and the long-term impact of sewage sludge derived compost or biochar on different plant groups (incl. root vegetables) at the field-scale is recommended.

Comparison of decomposition techniques for solid samples with emphasis on actinide content determination.

Comparison of conventional acid digestion with mixtures of acids HNO3, HClO4, and HF and thermal fusion utilizing Li borate as a fusion agent was made for solid samples. In the study, various parameters such as amount of the sample taken for the analysis, as well as addition of tracers before and after dissolution procedures were investigated. The obtained results showed that dissolution without any residue was achieved only when the fusion method was used. Thus, no filtration was needed prior to the loading of the sample on the resin to perform radiochemical separation. Alpha-particle spectrometry and neutron activation analysis were used for determination of the actinides content in the investigated samples as well as in residues obtained after dissolution.

Investigation of key factors in preparation of alpha sources by electrodeposition.

The electrodeposition for alpha source preparation, using several electrolyte solution-cathode material combinations, is investigated and evaluated. The investigated factors focused on the electrodeposition time, the applied current, electrolyte volume and anode-cathode distances for the conventional electrodeposition cell (with no external stirring or cooling system). The conditions (temperature and the solution pH) during the electrodeposition process were also studied and discussed. The optimized parameters for each system are provided, and evaluated for the usage in determination of actinides (uranium, plutonium, americium and curium radioisotopes) in various samples.

RADIONUCLIDE AND MAJOR ELEMENT ANALYSIS OF THERMAL AND MINERAL WATERS IN CROATIA WITH A RELATED DOSE ASSESSMENT.

Major elements concentrations (Na, K, Ca, Mg) and the activity concentrations of 226,228Ra, 234,238U, 210Po, 210Pb, 40K and 137Cs in northern and eastern Croatian thermal and mineral waters, collected directly from springs (or wells), are presented herein with total effective doses assessed for those waters that are considered as drinking 'cures' and are available for consumption. The methods used for radionuclide determination included alpha-particle spectrometry, gas-proportional counting and gamma-ray spectrometry, while the major element composition was determined by ICP-MS. The activity concentrations of all of the radionuclides were found to be below the guidance levels set by the WHO and EC Directive, with the exception of one water sample that measured 0.26 Bq L-1 of 228Ra. The effective ingestion dose assessment for the consumption of the so-called water 'cures' during 1, 2 or 4 weeks' time period throughout 1 year was well below the recommended 0.1 mSv for drinking water.

Evaluation of several electrolyte mixture-cathode material combinations in electrodeposition of americium radioisotopes for alpha-spectrometric measurements.

Three different types of electrolytes, subsequently modified and adjusted, in combination with three cathode materials used as source backings were analysed for electrodeposition of americium isotopes for alpha-spectrometric measurements. The obtained results are discussed in terms of electrodeposition yield and source quality (source homogeneity and spectral resolution, FWHM). The optimal conditions for source preparation are provided.

Fast Decomposition Procedure of Solid Samples by Lithium Borates Fusion Employing Salicylic Acid.

A new fast decomposition procedure for solid samples was developed. In this study, we investigated decomposition of samples by lithium borates fusion in combination with salicylic acid. The method described shortens the time required for the sample to be digested and loaded to a resin to up to 2 h, and it was especially suitable for alpha spectrometry measurements in emergency situations. Additionally, the method results in high radiochemical recoveries and when compared to other digestion methods (classical digestion utilizing mineral acids, microwave digestion, and lithium borates fusion in combination with polyethylene glycol (PEG)) gives comparable activity concentration values. The method used was applied to various reference materials with inorganic and organic matrices as well as widely varying amounts of uranium radioisotopes content. The results obtained were compared with reference and literature values and show that the proposed method can be successfully implemented on various types of samples.

Accumulation of 210Po in coastal waters (Gulf of Trieste, northern Adriatic Sea).

The total activity of 210Po was determined by alpha-spectrometry in various samples (matrices) collected in the Gulf of Trieste (northern Adriatic Sea) where fresh water inflows, especially from the Isonzo River in the northern part, affect water quality. Observed 210Po levels were: 1) 0.56-3.75 mBq/L in the dissolved phase (<0.45 µm) in the seawater column and local rivers, 2) 0.35-3.11 mBq/L (400-2300 Bq/kg, dry weight, dw) in suspended particulate matter (SPM, 0.45-20 µm) in the seawater column and local rivers, 3) 40 (Isonzo River) -158 Bq/kg (in a surface sediment cores collected in a NS transect in the gulf and sectioned to the depth of 20 cm) and 4) 239 (autumn) - 415 to 1800 (spring) Bq/kg (dw) in meso(zoo)plankton (>200 µm). In seawater and tributaries, up to 80% (mean 49%) of total 210Po was found in particulate form. In sediments, slightly higher levels were encountered in the Isonzo prodelta and in the central (depocenter) part of the gulf. KD (L/kg) calculated between seawater and SPM, and seawater and sediment amounted to about 5 × 106 and 6 × 104, respectively. Lower autumn 210Po levels can be a consequence of biological dilution by higher mesozooplankton biomass in the autumn compared to spring. Plankton fractionation revealed in general the highest levels in the >200 µm mesoplankton fraction (239-1800 Bq/kg) followed by 50-200 µm (388-996 Bq/kg) and 20-50 µm (318-810 Bq/kg) microplankton fractions. Obtained data show higher 210Po levels in all matrices analyzed in the Gulf of Trieste compared to other Adriatic (central Adriatic) and western Mediterranean areas. The 210Po/210Pb ratios in water, plankton and sediments were mostly below or around 1, while this ratio was much higher at higher trophic levels (up to about 50), reflecting a preferential bioaccumulation of 210Po over 210Pb. 210Po accumulation between seawater and SPM and seawater and mesozooplankton amounted to 3.7 × 104 and 1.1 × 104, respectively, similar to other Adriatic areas. Comparison of the relative importance of pelagic and benthic bioaccumulation pathways, excluding the filter feeder bivalves, suggests greater accumulation in pelagic-feeding species.

On the 209Po half-life error and its confirmation: an answer to the critique.

Pommé et al. published a paper claiming that the 209Po half-life is 20 % higher than the erroneous value of 102 (5) a used for 50 years. Collé and Collé published a critique saying that 'this claim cannot withstand critical scrutiny'. In this work, counterarguments are presented to the critique. The experiment has been continued and a new intermediate half-life value of 122.7 (27) a was obtained. A brief review is made of the 209Po half-life value by Collé et al. and a recommended value of 122.9 (23) a is derived from both experiments.

Radioactivity of cigarettes and the importance of (210)Po and thorium isotopes for radiation dose assessment due to smoking.

Tobacco and tobacco smoke are very complex mixtures. In addition to various chemical and organic compounds they also contain natural radioactive elements (radionuclides). In this work, the natural radionuclide activity concentrations ((234)U, (238)U, (228)Th, (230)Th, (232)Th, (226)Ra, (210)Pb and (210)Po) of nine different cigarette samples available on the Slovenian market are reported. In addition to (210)Po, the transfer of thorium isotopes from a cigarette to a smoker's body and lungs have been determined for the first time. Cigarette smoke and exhaled air from smokers' lungs were collected from volunteer smokers (C-4 brand) to determinate what quantity of (210)Po and thorium isotopes is transferred from the tobacco to the smoker's lungs. Cigarette ash and smoked filters were also collected and analysed. Among the determined isotopes, (210)Pb and (210)Po showed the highest activity concentrations. During the smoking of one cigarette approximately 22% of (210)Po (and presumably its predecessor (210)Pb), 0.6% of (228)Th, 24% of (230)Th, and 31% of (232)Th are transferred from the cigarette and retained in the smoker's body. The estimated annual effective dose for smokers is 61 µSv/year from (210)Po; 9 µSv/year from (210)Pb; 6 µSv/year from (228)Th; 47 µSv/year from (230)Th, and 37 µSv/year from (232)Th. These results show the importance of thorium isotopes in contributing to the annual effective dose for smoking.

Natural radioactivity in tap waters from the private wells in the surroundings of the former Zirovski Vrh uranium mine and the age-dependent dose assessment.

Activity concentration of (238)U, (234)U, (226)Ra, (228)Ra, (210)Pb and (210)Po in tap water from selected springs and private wells in the area of the former uranium mine at Zirovski Vrh were determined. A total of 22 tap water samples were collected at consumer's houses. The results show that the activity concentrations of uranium in water samples are in range (0.17-372) and (0.22-362) mBq L(-1) for (238)U and (234)U, respectively. Radium activity concentrations are in range (0.14-16.7) and (0.9-11.7) mBq L(-1) for (226)Ra and (228)Ra, respectively. (210)Po activity concentration is in range (0.28-8.0) mBq L(-1) and can be regarded as the lowest amongst all analysed radionuclides. The range for (210)Pb is (0.5-24.6) mBq L(-1). Based on the results obtained for activity concentrations of six radionuclides, the committed effective dose for three different age groups of population were estimated. It was found that the committed effective dose was well below the recommended value of 100 µSv year(-1), ranging from 2.3 to 34.3 µSv year(-1) for adults, from 3.5 to 32.0 µSv year(-1) for children (7-12 years) and from 3.0 to 23.3 µSv year(-1) for infants.

Levels of major and trace elements, including rare earth elements, and ²³8U in Croatian tap waters.

Concentrations of 46 elements, including major, trace, and rare earth elements, and (238)U in Croatian tap waters were investigated. Selected sampling locations include tap waters from various hydrogeological regions, i.e., different types of aquifers, providing insight into the range of concentrations of studied elements and (238)U activity concentrations in Croatian tap waters. Obtained concentrations were compared with the Croatian maximum contaminant levels for trace elements in water intended for human consumption, as well as WHO and EPA drinking water standards. Concentrations in all analyzed tap waters were found in accordance with Croatian regulations, except tap water from Sibenik in which manganese in concentration above maximum permissible concentration (MPC) was measured. Furthermore, in tap water from Osijek, levels of arsenic exceeded the WHO guidelines and EPA regulations. In general, investigated tap waters were found to vary considerably in concentrations of studied elements, including (238)U activity concentrations. Causes of variability were further explored using statistical methods. Composition of studied tap waters was found to be predominately influenced by hydrogeological characteristics of the aquifer, at regional and local level, the existing redox conditions, and the household plumbing system. Rare earth element data, including abundances and fractionation patterns, complemented the characterization and facilitated the interpretation of factors affecting the composition of the analyzed tap waters.

Polonium-210 and selenium in tissues and tissue extracts of the mussel Mytilus galloprovincialis (Gulf of Trieste).

Marine organisms such as mussels and fish take up polonium (Po) and selenium (Se), and distribute them into different cellular components and compartments. Due to its high radiotoxicity and possible biomagnification across the marine food chain Po-210 is potentially hazardous, while selenium is an essential trace element for humans and animals. The aim of this study was to investigate and compare the presence and extractability of the elements in the mussels Mytilus galloprovincialis collected in the Gulf of Trieste. The levels of Po-210 in the samples ranged from 220 to 400 Bq kg(-1) and of Se from 2.6 to 8.2 mg kg(-1), both on a dry matter basis. Using various extraction types and conditions in water, buffer or enzymatic media, the best extractability was obtained with enzymatic extraction (Protease XIV, 1h shaking at 40 °C) and the worst by water extraction (24 h shaking at 37 °C). 90% of Po-210 and 70% of Se was extractable in the first case versus less than 10% of Po-210 and less than 40% of Se in the second. Such evident differences in extractability between the investigated elements point to different metabolic pathways of the two elements. In enzymatic extracts Se speciation revealed three Se compounds (SeCys2, SeMet, one undefined), while Po-210 levels were too low to allow any conclusions about speciation.

Radiological characterization of tap waters in Croatia and the age dependent dose assessment.

Activity concentrations of (234)U, (238)U, (226)Ra, (228)Ra, (210)Po and (210)Pb in tap waters, originating from various geological regions of Croatia, were determined. Activity concentrations of measured radionuclides are in general decreasing in this order: (238)U≈(234)U>(228)Ra≈(210)Pb>(226)Ra≈(210)Po. Based on the radionuclide activity concentrations average total annual internal doses for infants, children and adults, as well as contribution of each particular radionuclide to total dose, were assessed and discussed. The highest doses were calculated for infants, which makes them the most critical group of population. All values for each population group were well below the recommended reference dose level (RDL) of 0.1mSv from one year's consumption of drinking water according to European Commission recommendations from 1998. Contribution of each particular radionuclide to total doses varied among different age groups but for each group the lowest contribution was found for (226)Ra and the highest for (228)Ra.

Seasonal and spatial variations of 210Po and 210Pb activity concentrations in Mytilus galloprovincialis from Croatian coast of the Adriatic Sea.

Results of 2 years monitoring of (210)Po and (210)Pb activity concentrations in soft tissue of the species Mytilus galloprovincialis from Croatian part of the Adriatic coast are presented. The samples were collected at thirteen coastal stations (some of which are also a part of the Mediterranean Mussel Watch Project) in spring and autumn of 2010 and 2011. The collected mussels were ranging between 4 cm and 6 cm in shell length. After sample pre-treatment lead and polonium were radiochemically separated on Sr resin. (210)Po was determined by alpha-particle spectrometry and (210)Pb was determined, via (210)Bi, by a low-level gas proportional counter. The results of (210)Po activity concentrations were found to vary between (104±11) and (1421±81) Bq kg(-1) dry weight while (210)Pb activity concentrations were much lower and in range (8.2±5.3)-(94.1±29.8) Bq kg(-1) dry weight. Higher (210)Po and (210)Pb activity concentrations were determined in spring period. The inter-site differences seen in their activity concentrations can be due to natural background levels of sites. The (210)Po/(210)Pb activity concentration ratios in all cases exceeded unity for all mussel samples and ranged between 4.0 and 47.9.

Recent measurements of 234U/238U isotope ratio in spring waters from the Hadzici area.

The Hadzici area has become interesting for investigation since depleted uranium ammunition had been employed in 1995 during the NATO air strike campaign in Bosnia and Herzegovina. The purpose of this study is to determine uranium concentration and (234)U/(238)U activity ratio in the spring waters of this area and to investigate their relationship, as well as spatial variations. The spring water samples were taken at 18 sites in total. For the determination of uranium radioisotopes, radiochemical separation procedure followed by alpha-particle spectrometry was applied. Uranium concentration in analyzed waters range from 0.15 to 1.12 µg/L. Spring waters from carbonate based sediments have a lower uranium concentration of between 0.15 and 0.43 µg/L, in comparison to waters sampled within sandstone-based sediments ranging from 0.53 to 1.12 µg/L. Dissolved uranium shows significant spatial variability and correlation with bedrock type confirmed by Principal Component Analysis and Hierarchical Cluster Analysis. The majority of the analyzed waters have a (234)U/(238)U activity ratio ranging from 1.02 to 1.90, of which half of the results range between 1.02 and 1.16. No apparent depleted uranium (DU) contamination was observed, as (234)U/(238)U activity ratio is dependent on geochemical conditions in the environment. Even though the tested spring waters demonstrate significant variability in uranium concentration, (234)U/(238)U activity ratio and (234)U excess, waters with similar uranium isotopic signatures are observable within the region. The guidelines on the spatial redistribution of dissolved uranium (corresponding to (238)U mass concentration), along with (234)U/(238)U activity ratios were provided by the Inverse Distance Weighting (IDW) method. Waters having similar isotopic signature have been delineated.

Natural radionuclides in bottled drinking waters produced in Croatia and their contribution to radiation dose.

Activity concentrations of (234)U, (238)U, (226)Ra, (228)Ra, (210)Po and (210)Pb in all Croatian bottled drinking natural spring and natural mineral water products, commercially available on the market, were determined. The samples originated from various geological regions of Croatia. Activity concentrations of measured radionuclides are in general decreasing in this order: (234)U>(238)U>(226)Ra>(228)Ra>(210)Pb>(210)Po and (226)Ra>(228)Ra>(234)U>(238)U>(210)Pb>(210)Po for natural spring and mineral waters, respectively. Based on the radionuclide activity concentrations average total annual effective ingestion doses for infants, children and adults, as well as contribution of each particular radionuclide to total dose, were assessed and discussed. The highest doses were calculated for children from 7 to 12 years of age, which makes them the most critical group of population. All values for each type of water, as well as for each population group, were well below the recommended reference dose level (RDL) of 0.1 mSv from one year's consumption of drinking water according to the European Commission recommendations from 1998. Contribution of each particular radionuclide to total doses varied among different water types and within each water type, as well as between different age groups, where the lowest contribution was found for uranium isotopes and the highest for (228)Ra.

(210)Po and (210)Pb activity concentrations in Mytilus galloprovincialis from Croatian Adriatic coast with the related dose assessment to the coastal population.

Activity concentrations of (210)Po and (210)Pb in the species Mytilus galloprovincialis from Croatian Adriatic coast were determined. The samples were collected in thirteen sampling places which are also a part of Croatian Mediterranean mussel watch project. The results of (210)Po and (210)Pb activity concentrations were found to vary between (22.1±2.5)-(207±21) Bq kg(-1) fresh weight and (2.8±1.4)-(9.3±0.7) Bq kg(-1) fresh weight, respectively. (210)Po/(210)Pb ratio ranged between 6.2 and 30.7. The highest measured activities were found in the enclosed basins of the Neretva channel, where the majority of Croatian mussel cultivation is taking place. The estimated consequent average total annual effective ingestion dose due to (210)Po and (210)Pb from mussel consumption in Croatian coastal region is 202±99 µSv with 96% contribution of (210)Po to the total effective dose.

Sequential determination of Pu and Am radioisotopes in environmental samples; a comparison of two separation procedures.

Two separation methods for the sequential determination of Am and Pu radionuclides are presented and the results obtained are compared. Analysis involves leaching the sample with concentrated nitric acid (HNO(3)), followed by radiochemical separation using extraction chromatographic resins (UTEVA, TRU) and anion exchange. Sources for alpha spectrometry were prepared by micro-precipitation on neodymium fluoride (NdF(3)). The chemical recoveries were determined using (242)Pu and (243)Am tracers. The methods were tested on reference materials and on two sediments. All the results were in good agreement with the reference values. The evaluation of uncertainty is also included.

Determination of 210Pb and 210Po in sediment and soil leachates and in biological materials using a Sr-resin column and evaluation of column reuse.

In this work we present a suitable way to release lead and polonium from sediments and other samples. Results obtained by hot-acid dissolution and cold leaching showed that while good recoveries of 210Pb were obtained in both the cases, 210Po recovery in hot dissolution was poor due to volatility of polonium, and might lead to erroneous results due to non-equilibration of added 208Po tracer and 210Po in the matrix. A Sr-resin column was used for separation of Pb and Po. We also studied the possibility of reusing columns used earlier. The most significant problem in reuse is the reduction in column capacity, resulting in a reduction to half of its initial capacity. Other natural radionuclides do not interfere in the determination of 210Pb and 210Po and we found no measurable contamination of the column on repeated usage.