Experimental determination of the vertical and horizontal distribution of 137Cs in the ground

doi:10.1016/0265-931X(95)00017-5

Journal of Environmental Radioactivity

Volume 27, Issue 2, 1995, Pages 141-160

https://doi.org/10.1016/0265-931X(95)00017-5 Get rights and content

Abstract

The activity of ¹³⁷Cs in soil was determined by gamma-spectroscopic measurements on several bore cores, sliced in 2–3 cm layers, taken at four places in Sweden. A method of taking the bore cores in a triangular pattern for the dual purpose of minimizing the number of samples as well as the analysis time was investigated and used to determine the vertical and horizontal behaviour of the distribution of ¹³⁷Cs in soil. It was found that cross contamination and compression of the soil during sampling was negligible. The depth distribution of ¹³⁷Cs activity, from fallout as well as that from Chernobyl, was found by fitting the experimental points to an exponential function, which was found not to be a simple function of depth. The method of sampling also made it possible to express the depth as linear depth in cm in spite of large variations in soil density. The activity at a given site was shown to be well approximated by a general sample composed of soil from the three bore cores, and the activity uncertainty obtained was about 17%.

References (16)

B. Bjurman et al.
Efficiency calibration of Ge spectrometers for measurements on environmental samples
Nucl. Instr. Meth.
(1987)
B. Erlandsson et al.
Relation between the air activity and the deposition of Chernobyl debris
Environ. Int.
(1988)
M. Korun et al.
In-situ measurements of the radioactive fallout deposit
Nucl. Instr. Meth.
(1991)
C. Murith et al.
Radioactivity measurements in the vicinity of swiss nuclear power plants
Nucl. Instr. Meth.
(1986)
R. Arntsing et al.
Field Gamma Ray Spectrometry and Soil Sample Measurements in Sweden Following the Chernobyl Accident
A Data Report. FOA Report D 20177-4.3
(1991)
H.L. Beck
Environmental gamma radiation from deposited fission products, 1960–1964
Health Phys.
(1966)
H.-J. Denk et al.
Measurements and Evaluation of a Multicompartment Model for estimating future activity profiles of radiocaesium in undisturbed soil of pasture-land in North Rhine-Westphalia
M. Felsmann et al.
Gamma-spectroscopic soil measurements: Spatial variation of concentrations of natural and artificial radionuclides and their correlation with external exposure

There are more references available in the full text version of this article.

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The smaller the movement coefficient (k) or the greater the value of the DRL, the deeper the radionuclides penetrate the soil profile. It is worthy to mention that similar equation for the time dependence of the depth distributions has been also applied as a simplification of the general convective diffusive equation for so-called “young” distributions (Isaksson and Erlandsson, 1995; Miller et al., 1990; Poiarkov et al., 1995). In general, the parameter of the exponential function (k) for all soil types was estimated by applying equation (2).
The time-dependent of the average migration, depths and migration rates of radiostrontium and radiocesium were experimentally determined in sandy soil in Kuwait. The study aimed to describe the behavior of these radionuclides in typical soil types in Kuwait. Custom-made large-diameter lysimeters (30 cm) were constructed to hold about 70 kg of undisturbed soil. The top surface soil was contaminated with known activity concentrations of ⁸⁵Sr and ¹³⁴Cs radionuclides. The topsoil was wetted with 1 L of water weekly using a rain simulator tool. Gamma scanning of the lysimeters in a step of 5 cm from three sides was performed at three measurement times by a high-resolution portable gamma spectrometry system. The vertical distribution pattern of ⁸⁵Sr and ¹³⁴Cs concentration exhibited an exponential trend. The average migration depth and migration rates were calculated, and 90% of the ⁸⁵Sr and ¹³⁴Cs were situated at 10.38 and 5.73 cm in the topsoil layer, respectively. The average vertical migration rate of ⁸⁵Sr varied from 2.2 to 4.4 cm y⁻¹, and ¹³⁴Cs was from 0.3 to 0.9 cm y⁻¹. It was demonstrated that the mobility of the ⁸⁵ Sr and ¹³⁴ Cs in the sandy soil could be attributed to the physicochemical properties of the radionuclide, in particular the distribution coefficient (Kd). The obtained results could be adopted by the regions of similar climatological conditions, especially, the gulf countries region when the radiological risk assessment of contaminated sites and dose estimation is required.
NORM contaminated area identification using radionuclides activity concentration pattern in a soil profile
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Many field studies indicate that 137Cs activity concentration vertical distribution consistently follows an exponential trend when the fraction of caesium activity below a given depth is plotted against the depth (Miller et al., 2009). However, other data also suggest that the downward transport of artificial radionuclides in the ground is often not well described by an exponential function of depth and variation of soil density with depth (Isaksson and Erlandsson, 1995) or more precisely, specific mineral composition of particular soil horizons should be accounted (Rigol et al., 1996). With no regards to details time series data have gathered since Chernobyl incident proved that the 137Cs activity concentration depth-distribution shows great similarities between the years, implying that the caesium, once deposited, has in a rather short time migrated through the top soil down to a certain depth and thereafter shows a slow migration (Isaksson et al., 2001).
According to the requirements set by European BSS the exposure of humans and biota to ionizing radiation originating from natural radionuclides but under anthropogenically changed conditions should be managed within the same regulatory framework as other practices. Such situation creates the strong needs to have a reliable method to distinguish whether the particular case of natural radioactivity occurrence has resulted from human activity or it is pure natural phenomenon. In case of current activity of particular NORM industry there are no doubts however, in case of a legacy site, such question becomes crucial. One of the first warnings that the evaluated case has resulted from human deliberate or accidental activity is the lack of secular equilibrium among radionuclides constituting natural decay series. On the other hand some radionuclides, deposited on the ground surface due to radioactive fallout (e.g. caesium or lead isotope ²¹⁰Pb), create in long term perspective a specific pattern that remains characteristic for un undisturbed soil. Hence, it can be assumed that every observed change in it proves a human activity. In order to check this 19 soil profiles taken at undisturbed area and around different NORM heaps were analyzed. The measured radionuclides concentrations were used to anatomize any alternation of natural state, assess radionuclides migration and even investigate the history of a site of concern in the time horizon, usually long enough to identify any human activity. Results procured an easy method of identification different NORM sites based on observed ratios of particular natural radionuclides.
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The value of p in Eq. (1) is often used as 1 in most studies. However, Isaksson and Erlandsson (1995) have indicated that the value of p can also be 0.75 for a lichen carpet, 2.00 in the case of purely diffusional transport, or even lower for active transport processes. As we dealt with the forest floor separately in the preceding sections, p was used as 1, and the empirical data were fitted using Eq. (1).
This study deals with the description of the vertical distribution of radiocaesium (¹³⁷Cs and ¹³⁴Cs) in a representative coniferous forest soil, investigated 10 months after the Fukushima radioactive fallout. During soil sampling, the forest floor components (understory plants, litter (Ol-) and fermented layers (Of)) were collected and treated separately. The results indicate that radiocesium is concentrated in the forest floor, and high radiocesium transfer factor observed in the undergrowth plants (3.3). This made the forest floor an active exchanging interphase for radiocesium. The raw organic layer (Ol + Of) holds 52% (5.3 kBq m⁻²) of the Fukushima-derived and 25% (0.7 kBq m⁻²) of the pre-Fukushima ¹³⁷Cs at the time of the soil sampling. Including the pre-Fukushima ¹³⁷Cs, 99% of the total soil inventory was in the upper 10 cm, in which the organic matter (OM) content was greater than 10%, suggesting the subsequent distribution most likely depends on the OM turnover. However, the small fraction of the Fukushima-derived ¹³⁷Cs at a depth of 16 cm is most likely due to the infiltration of radiocesium-circumscribed rainwater during the fallout before that selective adsorption prevails and reduces the migration of soluble ¹³⁷Cs. The values of the depth distribution parameters revealed that the distribution of the Fukushima-derived ¹³⁷Cs was somewhat rapid.
Determination of dose rate from Chernobyl-derived radiocaesium in Estonian soil
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The deposition and vertical depth distribution of 134Cs and 137Cs in the natural undisturbed soil profiles down to 20–25 cm were studied at locations in the North Eastern Estonia, which were most strongly affected by the Chernobyl fallout in 1986. The total depositions were estimated based on summing the sampled and measured activities of 134Cs and 137Cs in all sections of soil profiles. The Chernobyl 137Cs deposition values varied considerably from site to site and the range was from 3.9 kBq m⁻² to 50.2 kBq m⁻², with the average of 22.8 kBq m⁻² for the region (reference data May 1, 1986). The ratio of total activities, A(134Cs)/A(137Cs), varied in the range from 0.47 to 0.55. Using a compartment model and the observed data on the 134Cs and 137Cs activity concentrations (Bq m⁻²) in four compartments, 0–1 cm, 1–5 cm, 5–15 cm and 15–30 cm, of soil collected in 1991–2003, the approximate residence half-times of radiocaesium in soil were determined. The latter increased from 3.7 y in the top-most compartment to 8.6 y and 36.4 y in the deeper compartments, respectively. The time dependence of the external gamma-dose rate at the height of 1 m above a flat ground area arising from the deposited and migrating radiocaesium was calculated using the modeled data on the 134Cs and 137Cs activity in soil compartments. Considering the total depositions of radiocaesium in soil from the Chernobyl 1986 accident, the 50 year effective doses caused by external gamma exposure varied in the range from 0.13 mSv to 1.74 mSv, with the mean of 0.79 mSv in the region.
Long-term investigation of anthropogenic and naturally occurring radionuclides at reference sites in western Sweden
2009, Journal of Environmental Radioactivity
Citation Excerpt :
To compare the in situ measurements with the analysis of soil samples, the activity determined from the in situ measurements was multiplied with the wet/dry weight ratio measured in the soil samples collected at the measurement site. Soil sampling was performed using a specially designed metal corer (Isaksson and Erlandsson, 1995) with an 80 mm diameter. At each site, the soil was sampled at the locations where the in situ measurements were performed.
In case of an accidental release of radioactive substances into the environment, it is important to quickly and reliably estimate the radiation dose received by people in the affected area, and to determine the extent of the contamination. Measurements of the extent of the release and the subsequent contamination can be facilitated if there are predetermined reference sampling sites with known background radiation and inventory of radionuclides. Since 1996, 34 reference sites for soil sampling, field gamma, and intensimeter measurements have been established in western Sweden. Time series data for dose rates and radioisotope inventory have been collected at these sites, allowing for the investigation of changes in these parameters over time. The mass activity densities for the uranium and thorium series elements varied approximately between 10 and 50 Bq/kg and between 10 and 40 Bq/kg, respectively. The mass activity density of ⁴⁰K was approximately in the range 300–800 Bq/kg. The radiation exposure due to ¹³⁷Cs was rather small in this area. The dose rates calculated from in situ measurement data showed that the contribution to the total dose rate was almost entirely due to naturally occurring radionuclides. The measured dose rate was about twice as high as the calculated rate, even after subtracting the contribution from cosmic radiation. This may be explained by the fact that intensimeters generally are calibrated to measure the quantity ambient dose equivalent, which should not underestimate the effective dose.

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Experimental determination of the vertical and horizontal distribution of 137Cs in the ground

Abstract

Nucl. Instr. Meth.

Environ. Int.

Nucl. Instr. Meth.

Nucl. Instr. Meth.

Field Gamma Ray Spectrometry and Soil Sample Measurements in Sweden Following the Chernobyl Accident

A Data Report. FOA Report D 20177-4.3

Environmental gamma radiation from deposited fission products, 1960–1964

Health Phys.

Measurements and Evaluation of a Multicompartment Model for estimating future activity profiles of radiocaesium in undisturbed soil of pasture-land in North Rhine-Westphalia

Gamma-spectroscopic soil measurements: Spatial variation of concentrations of natural and artificial radionuclides and their correlation with external exposure

Experimental determination of the vertical and horizontal distribution of ¹³⁷Cs in the ground