arXiv subjects

Z. Franic

Publications and source records attributed to Z. Franic.

4 recordsLinked to original sources

arXiv2007

Radiocaesium Activity Concentrations in Potatoes in Croatia after the Chernobyl Accident and Dose Assessment

Systematic investigations of 137Cs and 134Cs activity concentrations in potatoes (Solanum tuberosum) for the post-Chernobyl period (1986-2005) in the Republic of Croatia are summarized. The correlation between 137Cs activity concentrations in fallout and potatoes, has been found to be very good, the correlation coefficient being r2=0.88 with P(t) < 0.001 for 18 degrees of freedom. As the radiocaesium levels in potatoes decreased exponentially, the mean residence time of 137Cs in potatoes was estimated by fitting the measured activity concentrations to the exponential curve. The mean residence time was found to be 6.8 +/- 1.1 years, the standard deviation being estimated by the Monte Carlo simulations. The initial observed 134Cs:137Cs activity ratio in potatoes has been found to be quite variable, but slightly lesser than theoretically predicted value of 0.5, calculated by applying the known inventory of these radionuclides in the Chernobyl reactor to the equation for the differential radioactive decay. This can be explained by presence of the pre-Chernobyl 137Cs in soil that originated from nuclear fallout. The annual effective doses received by 134Cs and 137Cs intake due to consumption of potatoes estimated for an adult member of Croatian population were found to be very small, as the per caput dose for the entire 1986 - 2005 period was calculated to be about 2.9 mSv, 134Cs accounting approximately for 1/3 of the entire dose. Therefore, after the Chernobyl accident consumption of potatoes was not the critical pathway for human intake of radiocaesium from the environment in Croatia.

physics.med-ph↗

arXiv2007

Long-term investigations of radiocaesium activity concentrations in carps in north Croatia after the Chernobyl accident

Long-term investigations of radiocaesium activity concentrations in carps in the Republic of Croatia are presented. The radiocaesium levels in carps decreased exponentially and the effective ecological half-life of 137Cs in carps was estimated to be about 1 year for 1987-2002 period and 5 years for 1993-2005 period. The observed 134Cs:137Cs activity ratio in carps has been found to be similar to the ratio that has been observed in other environmental samples. Concentration factor for carps (wet weight) was roughly estimated to be 128 +/- 74 Lkg-1, which is in reasonable agreement with model prediction based on K+ concentrations in water. Estimated annual effective doses received by 134Cs and 137Cs intake due to consumption of carps for an adult member of Croatian population are small, per caput dose for the 1987 - 2005 estimated to be 0.5 +/- 0.2 microSv. Due to minor freshwater fish consumption in Croatia and low radiocaesium activity concentrations in carps, it can be concluded that carps consumption was not a critical pathway for the transfer of radiocaesium from fallout to humans after the Chernobyl accident.

physics.med-ph↗

arXiv2004

Estimation of the Adriatic sea water turnover time using fallout 90Sr as a radioactive tracer

Systematic, long term measurements, starting in 1963, of 90Sr activity concentrations in sea water have been performed at four locations (cities of Rovinj, Rijeka, Split and Dubrovnik) along the Croatian coast of the Adriatic sea. In addition, fallout samples were collected in the city of Zadar. 90Sr activity concentrations are in good correlation with the fallout activity, the coefficient of correlation being 0.72. After the nuclear moratorium on atmospheric nuclear bomb tests in 1960s, 90Sr activity concentrations in sea water exponentially dropped from 14.8 +/- 2.4 Bq/m3 in 1963 to 2.0 +/- 0.3 Bq/m3 in 2003. In the same period, the total annual 90Sr land surface deposit in Zadar fell by three orders of magnitude, from 713.3 Bq/m2 in 1963 to 0.4 Bq/m2 in 2003. Using strontium sea water and fallout data, a mathematical model was developed to describe the rate of change of 90Sr activity concentrations in the Adriatic sea water and estimate its mean residence time in the Adriatic. By fitting the experimental data to a theoretically predicted curve, the mean residence time of 90Sr in the Adriatic sea water was estimated to be approximately 3.4 +/- 0.4 years, standard deviation being calculated by Monte Carlo simulations. As in physical oceanography 90Sr can be used as effective radioactive tracer of water mass transport, this value also reflects the upper limit for turnover time of the Adriatic sea water. The turnover time of 3.4 years for the Adriatic sea water is in reasonable agreement with the value which was estimated, by studying water flows through the Strait of Otranto, to be on the order of 1 year.

physics.med-ph↗

arXiv2004

Radiostrontium activity concentrations in milk in the Republic of Croatia for 1961 - 2001 and dose assessment

Results of systematic measurements of Sr-90 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 Sr-90 deposited by fallout, being 1060 Bq/m2, was recorded in 1963, while the peak Sr-90 activity concentration in milk, 1.42 +/-0.17 Bq/L, was recorded in 1964. The values in year 2001 for fallout deposition and milk were 7.7 Bq/m2 and 0.07 +/- 0.03 Bq/L, respectively. The reactor accident at Chernobyl caused higher Sr-90 levels only in 1986. Sr-90 fallout activity affects milk activity, the coefficient of correlation between Sr-90 fallout activity and Sr-90 activity concentrations in milk being 0.80. The transfer coefficient from fallout deposition to milk was estimated to be 2.5 mBqy/L per Bq/m2. The dose incurred by milk consumption was estimated for the Croatian population, the annual collective effective dose in 2001 being approximately 2.0 man-Sv.

physics.med-ph↗