Radioactivity concentrations of ~(40)K, ~(134)Cs, ~(137)Cs, ~(90)Sr, ~(241)Am, ~(238)Pu and ~(239+240)Pu radionuclides in Jordanian soil samples

摘要

In November 2000, surface and core soil samples were collected from different regions of Jordan. The samples were analyzed by direct gamma spectrometry and combined radiochemical separation procedure to quantify ~(40)K, ~(134)Cs, ~(137)Cs, ~(90)Sr, ~(241)Am, ~(238)Pu and ~(239+240)Pu radioactivity. Concentrations (Bq.kg~(-1) dry weight) have been observed to vary in the range 1.5-2.6 for ~(134)Cs, 2.8-11.4 for ~(90)Sr, and 0.13-0.48 for ~(241)Am, 0.016-0.062 for ~(238)Pu, 0.28-1.01 for ~(239+240)Pu and 155-543 for ~(40)K. The typical concentration of ~(137)Cs found in topsoils (0-2 cm) ranged in 7.5-576 Bq.kg~(-1), dry weight. These values were greater than those observed in samples taken at greater depths (up to 32 cm). Activity ratios of ~(134)Cs/~(137)Cs, ~(90)Sr/~(137)Cs, ~(239+240)Pu/~(137)Cs, ~(238)Pu/~(137)Cs, ~(241)Am/~(137)Cs, ~(239+240)Pu/~(238)Pu and ~(241)Am/~(238)Pu have mean values of 0.0049 (R = 1), 0.29 (R = 0.76), 0.41 (R = 0.90), 0.39 (R = 0.85), 0.41 (R = 0.88), 7.72 (R = 0.97) and 16.66 (R = 0.98), respectively. The underlying concentrations were correlated and relatively higher than those reported in neighboring countries. One moss sample, as a biomonitor indicator, was measured and evaluated along with the soil samples. Its data showed higher concentrations of all measured radionuclides due to accumulations over years. The depth distribution of the fission product ~(137)Cs and the total deposition (Bq.m~(-2)) were also studied in selected samples. Estimations of the annual effective dose equivalent due to ~(137)Cs-soil contamination showed values up to more than 200 μSv.