This study refers to background activity concentrations of 238U, 226Ra, 232Th, 208Tl, 40K, and 137Cs in soil and plants of the Kaštela Bay, Croatia and related plant-soil concentration ratios (CR's). ...Fourteen different Mediterranean plant species growing in natural conditions have been included and were divided into three major plant groups (grasses and herbs, shrub, tree). Radionuclide activity concentrations were determined by means of high resolution gamma-ray spectrometry. Soil parameters (pH, electrical conductivity, and organic matter content) were also analysed. CR ranges were within one order of magnitude for 40K (10−2–10−1), 238U, and 226Ra (10−3–10−2), and two orders of magnitude for 232Th, 208Tl, and 137Cs (10−4–10−2). There was no statistical difference between the plant groups in radionuclide uptake. Overall statistical analyses indicated a moderate negative relationship between soil concentrations and CR values, and no relationship with soil parameters, except a negative one for 137Cs. Comparison with literature showed more agreement with studies that were done in the Mediterranean than with ICRP and IAEA databases. Our data not only describe the natural radioactivity of the Bay, but also create a dataset that could be relevant for further radioecological assessments of the Kaštela Bay.
•Background radioactivity in soil and 14 different Mediterranean plants was studied.•Concentration ratios of 238U, 226Ra, 232Th, 208Tl, 40K, and 137Cs are reported.•No statistical difference in CR values between plant groups was found.•There was a moderate negative correlation between soil activities and CR values.•No dependency was found between soil parameters and CR, except for 137Cs.
We report on the fine structure of the absorbed dose rate D which was measured and recorded on a daily basis at the Institute for Medical Research and Occupational Health in Zagreb, Croatia, ...throughout the period 1985–2011. After the Chernobyl accident, D increased steeply by a factor of 3.5, but this is the only prominent feature in the D versus time (t) curve. In the absence of accidental conditions, the D(t) is flat and amounts to 30–35 pGy/s. Despite the apparent plainness of D(t), its Fourier transform reveals several periodic modulations hidden in the noise. Some of the corresponding periods (6 and 12 months) can be related to seasonal atmospheric changes but this is not the case with the other periods identified (9.3, 13.7, 15.7, 20, 31, and 39 months). These are found to agree well with literature data on periodicities in solar activity, which implies that they are most probably linked to variations in the atmospheric production of 7Be by cosmic rays.
► Absorbed dose rate D was monitored on a daily basis over twenty-six years. ► D was constant (30–35 pGy/s) always except after the Chernobyl accident. ► D as a function of time comprises well defined periodicities. ► Non-seasonal periodicities in D agree with those in solar activity. ► Non-seasonal modulations of D are linked to production of 7Be by cosmic rays.
The contents of natural radionuclides (radium, uranium and potassium) were measured in the area of a phosphate fertilizer factory in central Croatia, as a part of extended and still ongoing ...monitoring program of radioactive contamination of human environment in Croatia that is performed by the Radiation Protection Unit of the Institute for Medical Research and Occupational Health in Zagreb. Activity concentrations in all analysed media (waste water, trickling water from piezometers, phosphogypsum deposit and final products) considerably fluctuated, especially in phosphogypsum and waste water. Mean
226Ra activity concentration in waste phosphogypsum was measured to be 483
±
190
Bq
kg
−1. Based on that value, it was estimated that 4
million
m
3 of phosphogypsum that have been deposited up to now contain about 4.3
×
10
12
Bq, i.e. about 200
g of
226Ra. However, effective dose for an adult that would be incurred by consumption of water from nearby wells was estimated to be 5.3
±
1.3
μSv. The results show that
226Ra activities cause effective doses, which are below the recommended maximum as the estimated annual
226Ra effective dose does not exceed 0.1
mSv as recommended by the World Health Organization.
Radioactive contamination originating from the coal fired powered plant and waste dumps located in a bay of the Adriatic which is sensitive to pollution was investigated. Radioactive levels were ...determined at 2 coal slag and ash piles, one an operating pile and the other an old pile, closed and covered by soil. Both piles are situated close to the seaside and as a result, slag and ash are accumulating in the littoral zone and in the case of the operating pile, are being filled up directly into the sea. Radioactivity measurements were made by gamma spectrometry in the field (in-situ) and in the laboratory. The results showed the presence of natural radionuclides of the uranium and thorium decay series and potassium-40. Absorbed dose rates at the old pile and outside the plant were up to 9 times lower than that determined for the operating pile. The mean value for all the investigated locations around the deposit site was 4 times lower than the mean value at the operating pile. Analysis of seawater samples collected close to the deposit site showed a mean radium-226 specific activity of 51.3 Bq per m3, which is an order of magnitude higher than that found in the Mediterranean sea or the open Adriatic. The mean absorbed dose rate around the plant is not thought to present a significant health risk for the inhabitants. It is recommended that particular attention be given to the sea and sea biota, because they come into direct contact with the deposited material, and could have a serious adverse effect on the marine ecosystem in the future.
Long-term investigations of radiocaesium activity concentrations in beef in the Republic of Croatia are presented. The radiocaesium levels in beef decreased exponentially and the effective ecological ...half-life of 137Cs was estimated to be 0.57±0.06 years for 1986–1990 period and 5.21±0.27 years for the 1991–2005 period. For 1986–1990 period, the effective ecological half-life of 134Cs in was estimated to be about 0.69±0.05 while 134Cs activity concentrations after year 1990 were below the detection limit of the instruments.
The 134Cs:137Cs activity ratio in beef has been found to be similar to the ratio that has been observed in other foodstuffs and environmental samples.
Radioecological sensitivity for beef meat, i.e., the transfer coefficient from fallout to sample was estimated to be 1.15× 10−2Bqykg−1/(Bqm−2).
For an adult member of Croatian population annual effective doses received by 134Cs and 137Cs intake due to consumption of beef are small, as per caput effective dose for the overall 1986–2005 period was estimated to be 24.6μSv. Consequently, after the Chernobyl accident beef consumption was not a critical pathway for the transfer of radiocaesium from fallout to humans in Croatia.
Investigations in the post-Chernobyl period (1986-2009) of radiocaesium activity concentrations in Adriatic pilchards are presented. Compared with pre-Chernobyl period, the Chernobyl nuclear accident ...caused increase of (137)Cs activity concentrations in pilchards. By fitting the measured (137)Cs activity concentrations to the theoretical curve was estimated to be 1.5±0.4 y for 1986-90 and 5.8±0.4 y for 1991-2009 and the bimodal behaviour for the ecological half-life of (137)Cs in pilchards has been observed. Estimated annual effective doses received by (134)Cs and (137)Cs intake due to consumption for an adult member of Croatian population are small. Collective dose for the 1986-2009 period was 4.9+0.3 person-Sv. The observed (134)Cs/(137)Cs activity ratio in pilchards was similar to the ratio that has been found in other environmental samples. The concentration factor for pilchards was roughly estimated to be 93.7±39.2 l kg(-1), which is consistent with the values observed elsewhere.
Investigations on the distribution and fate of naturally occurring, nuclear-weapons-produced, and reactor-released radionuclides in the city of Zagreb, Coatia, have been conducted as part of the ...monitoring program for radioactive contamination of the human environment in Croatia since the early 1960s. This paper describes long-term investigations of man-made
137Cs and naturally occurring
7Be in the city of Zagreb after the Chernobyl accident. The Chernobyl nuclear accident caused a major increase in
137Cs activity concentrations only in 1986, which quickly decreased over the next few years to pre-Chernobyl values. The observed mean residence time for
137Cs in the air during the post-Chernobyl period from January 1987 to December 1990 was estimated to be 1.0 year. During this period, the observed mean residence time for
137Cs in fallout was estimated to be 0.9 years. The mean
7Be activity concentration in the air from 1987 to 2004 was (5.4
±
2.8)
×
10
−
3
Bq m
−
3
. The measured
7Be activity concentrations showed seasonal behavior with the highest usually measured in July.
Despite the constant presence of radioactive matter in the Zagreb air during the observational period, activity concentration values never exceeded legal limits. Consequently,
137Cs doses incurred by inhaling contaminated air after the Chernobyl accident were very small.
Natural radioactivity of Middle-Adriatic Sea islands and islets was measured. Gamma spectrometric measurements, both in situ and in laboratory, as well as radon measurements in the seawater were ...performed. Activity concentrations and the associated dose rates due to naturally occurring 232Th, 238U and 40K radioisotopes were determined. Dose rates calculated from in situ gamma spectrometry are in correlation with dose rates calculated from activity concentrations measured in collected samples of pebbles and rocks. In situ gamma ray spectrometry in the seawater has been performed, showing activity concentration of 220 and 240 Bq m−3 for 214Bi and 214Pb, respectively due to the presence of magmatic rocks in the seabed. The radium equivalent activity varied from 13 to 53 Bq kg−1. These values are lower than the limit values, indicating that the radiation hazard is not significant. The highest mean activity concentrations of naturally occurring radionuclides in rock samples collected were found on the islands of magmatic origin.
Results of systematic measurements of 90Sr activity concentrations in milk for the period 1961-2001 are summarized. An exponential decline of radioactivity followed the moratorium on atmospheric ...nuclear testing. The highest activity of 90Sr deposited by fallout, 1,060 Bq m(-2), was recorded in 1963, while the peak 90Sr activity concentration in milk, 1.42 +/- 0.17 Bq L(-1), was recorded in 1964. The values in year 2001 for fallout deposition and milk were 7.7 Bq m(-2) and 0.07 +/- 0.03 Bq L(-1), respectively. The reactor accident at Chernobyl caused higher 90Sr levels only in 1986. 90Sr fallout activity affects milk activity; the coefficient of correlation between 90Sr fallout activity and 90Sr activity concentrations in milk is 0.80. The transfer coefficient from fallout deposition to milk was estimated to be 2.5 x 10(-3) Bq y L(-1) per Bq m(-2). The dose incurred by milk consumption was estimated for the Croatian population, the annual collective effective dose in 2001 being approximately 2.0 person-Sv.
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