Long-term retention of (137)Cs in three forest soil types with different soil properties

Strategic roadmap to assess forest vulnerability under air pollution and climate change

Although it is an integral part of global change, most of the research addressing the effects of climate change on forests have overlooked the role of environmental pollution. Similarly, most studies investigating the effects of air pollutants on forests have generally neglected the impacts of climate change. We review the current knowledge on combined air pollution and climate change effects on global forest ecosystems and identify several key research priorities as a roadmap for the future. Specifically, we recommend (1) the establishment of much denser array of monitoring sites, particularly in the South Hemisphere; (2) further integration of ground and satellite monitoring; (3) generation of flux-based standards and critical levels taking into account the sensitivity of dominant forest tree species; (4) long-term monitoring of N, S, P cycles and base cations deposition together at global scale; (5) intensification of experimental studies, addressing the combined effects of different abiotic factors on forests by assuring a better representation of taxonomic and functional diversity across the ~73,000 tree species on Earth; (6) more experimental focus on phenomics and genomics; (7) improved knowledge on key processes regulating the dynamics of radionuclides in forest systems; and (8) development of models integrating air pollution and climate change data from long-term monitoring programs.

Radiocaesium retention in bog meadows: an analysis based on soil properties

The vertical distribution of ¹³⁷Cs in peat bog soils in the remote period after the Chernobyl Nuclear Power Plant accident (ChNPP, 1986) was investigated. The study was conducted on bog meadows in the Bryansk region of Russia. Soil samples were taken at 4 locations: 2 sites on lowland bogs and 2 sites on transitional bogs. Fifteen years after the accident, analysis of soils showed that the peak of ¹³⁷Cs activity was still in the upper 10-cm layer. The highest percentage of the initial ¹³⁷Cs deposition (92%) has been observed in the top 10-cm layer in the drained transitional bog. The lowest part of the initial ¹³⁷Cs deposition (40%) has been found in 0-10-cm horizon in lowland bog with the deep peat layer. The findings revealed that elevated soil moisture promotes ¹³⁷Cs downward migration. It was shown that ammonium has a major impact on mobility of ¹³⁷Cs in bog soils. On average, the soil solution NH₄⁺ concentrations exceeded the K⁺ concentrations by about a factor 5. A significant linear relationship was found between the rates of ¹³⁷Cs removal from the top layers with the soil solution NH₄⁺ concentrations.

Deposition processes over complex topographies: Experimental data meets atmospheric modeling

The present paper describes the assessment of the atmospheric deposition processes in a basin valley through a multidisciplinary approach based on the data collected within an extensive physico-chemical characterization of the soils, combined with the local meteorology. Surface soil cores were collected on a NNW-SSE transect across the Terni basin (Central Italy), between the Monti Martani and the Monti Sabini chains (956 m a.s.l.), featuring the heavily polluted urban and industrial enclave of Terni on its bottom. Airborne radiotracers, namely ²¹⁰Pb and ¹³⁷Cs, have been used to highlight atmospheric deposition. We observed an increased deposition flux of ²¹⁰Pb and ¹³⁷Cs at sites located at the highest altitudes, and the associated concentration profiles in soil allowed to evaluate the role of atmospheric deposition. We also obtained a comprehensive dataset of stable anthropogenic pollutants of atmospheric origin that showed heterogeneity along the transect. The behavior has been explained by the local characteristic of the soil, by seeder-feeder processes promoted by the atmospheric circulation, and was reconciled with the concentration profile of radiotracers by factor analysis. Finally, the substantial impact of the local industrial activities on soil profiles and the role of the planetary boundary layer has been discussed and supported by simulations employing a Lagrangian dispersion model.

REFERENCE SURFACE FOR IN SITU GAMMA SPECTROMETRY

Chemical laboratories of the Fire Rescue Service of the Czech Republic are part of the radiation monitoring network and participate in the radiation situation monitoring in the Czech Republic. Measurements in situ are crucial for monitoring the radiation situation in emergencies associated with the deposition of radioactive substances on a large area. Those data can be used for estimating a possible dose obtained either by staying in a contaminated area or by consumption of food produced in the area. For correct setting of device parameters (e.g. efficiency calibration), standard samples should be measured regularly. Unlike in laboratory, verification in field conditions is difficult. Therefore, a search for suitable reference areas containing a higher amount of 137Cs homogeneously dispersed after the fall of a radioactive cloud passing through our territory following the Chernobyl accident was conducted. Small airports in the East Bohemia regions were identified as suitable candidates.

SELECTION OF SUITABLE SAMPLING TOOL FOR RELIABLE SOIL SAMPLING NOT ONLY AFTER RADIOLOGICAL ACCIDENT

The objective of this research was to develop a sampling protocol for contaminated soils after a large radiological accident. One of the criteria for good sampling method is reproducibility and accuracy of large number of samples collected in short time. Members of the chemical laboratories of the Fire Rescue Service of the Czech Republic (FRS CR), which are included in Radiation Monitoring Network, tested four tools in different soil types. More than 100 samples were collected. Root auger and square soil sampler seem to be the best for reliable soil sampling. Modifications of the root auger decreased of relative error of sampling to 7.5%. The root auger is recommended as a first-choice sampling tool based on: (1) ease, (2) operator safety, (3) collection of a representative sample (4) applicability to most soil types and (5) enabling collection of depth-discrete samples.

137Cs estimates of soil erosion rates in a small catchment on a channelized river floodplain in the lower reaches of Yangtze River, China

Channelization significantly affects soil erosion in river floodplains. The object of this study was to use ¹³⁷Cs as a tracer to determine the ¹³⁷Cs inventory and derived soil erosion rates under various land use types in a catchment on channelized river floodplain in the lower reaches of Yangtze River, China. Sampling was carried out to establish a¹³⁷Cs reference inventory in a 70-year old paddy field located on the shoulder-slope of a local hill. The mean reference inventory of ¹³⁷Cs was 1275 Bq m^-2, whereas the ¹³⁷Cs inventory within the catchment ranged from 284 to 1150 Bq m^-2 and the soil erosion rates from -33.3 to -2.4 t ha^-1 yr^-1, respectively. The dominated land use of paddy in cultivated soils contributed relative low soil erosion. Bamboo and castanea mollissima were preferential for local land uses in uncultivated soils in comparison with woodland and Pinnus massoniana. The rates of soil erosion rates in old tea garden were higher than that in new tea garden. Overall, severe soil erosion and no deposition in the entire catchment occurred in the entire catchment due to the human-induced channelization in the 1970s. Our results suggest that restricting farmland being returned to tea plantations, thereby maintaining the current land use types would reduce soil erosion in river floodplain in the future.

Effects of radiocesium fixation potentials on 137Cs retention in volcanic soil profiles of Fukushima forests

Radiocesium is well-known to be stabilized by clay minerals in soils, while volcanic soils could typically be poor in micaceous clays that fix ¹³⁷Cs effectively. We investigated ¹³⁷Cs fixation potentials [radiocesium interception potential (RIP)] and depth distribution of ¹³⁷Cs stocks in volcanic soils to analyze effects of clay content and mineralogy on soil retention and migration of ¹³⁷Cs after the Fukushima nuclear accident. Clay minerals of the volcanic soils were dominated by hydroxy-interlayered vermiculite (HIV) and short-range-order minerals, irrespective of bedrocks. The soil RIPs were positively correlated with mass of clay fraction among the HIV-dominated volcanic soils, but RIP per clay content in the HIV-dominated volcanic soils were lower than in the soils rich in illite or vermiculitic clays. The small RIPs in the organic horizons resulted in rapid ¹³⁷Cs migration from the organic horizons and their accumulation in the upper 0-5 cm mineral soil. Although RIPs of the studied volcanic soils fall within the lower class among major soil types, vertical ¹³⁷Cs migration in the mineral soil is small unless RIP is less than 300-400 mmol kg^-1 due to the low clay contents and shortage of illite or vermiculite.

Study of the radioactivity in environmental soil samples from Eastern Anatolia Region of Turkey

In this study, a detailed γ-ray spectrometer survey was performed to obtain the baseline data on natural and fallout radioactivity in soil samples (10–30 cm depth) collected from Iğdır which is a province in Eastern Anatolia Region of Turkey and located along the border with Armenia. Metsamor Nuclear Power Plant in Eastern Armenia is only about 20 km away from Iğdır province. The average activity concentrations of 226Ra, 232Th, 40K and 137Cs in the soil samples were found as 19.1±0.6 (range: 12.8–31.2 Bq kg−1), 21.9±0.6 (range: 11.6–36.8 Bq kg−1), 437.7±10.3 (range: 285.0–613.7 Bq kg−1) and 11.8±1.1 Bq kg−1, (range: 2.5–51.1 Bq kg−1), respectively. The radiological hazards caused by ionizing radiation emitted from these radionuclides on the population living in the region were assessed by estimating radiological parameters such as absorbed γ dose rate in outdoor and the corresponding annual effective dose rate from external exposure, annual effective dose rate from inhalation of radon and excess lifetime cancer risk. The results revealed that there is no significant radiological hazard for human population because the average values of radiological parameters are within the recommended limits.

Behaviour of 137Cs in forest humus detected across the territory of the Czech Republic

The activity concentration of ¹³⁷Cs in samples of coniferous forest humus collected across the territory of the Czech Republic in 1995 and 2005 was analysed, and it was found significantly correlated with the surface deposition caused by the Chernobyl accident. The effective (12.8 y) and environmental (22.3 y) half-lives of radiocaesium in humus were calculated and compared with those in spruce bark. The impact of important forest stand factors, that is, precipitation, content of organic matter, age of trees and pH, on the behaviour of ¹³⁷Cs in humus was studied. It was observed that humus samples with a higher proportion of organic matter, higher pH(H2O) and pH(CaCl2) contained higher amounts of ¹³⁷Cs. Conversely, with the age of trees, the activity concentration of ¹³⁷Cs in humus is decreasing. Higher precipitation and humus acidity decrease the reduction rate of the ¹³⁷Cs in humus. These stand factors increase bioavailability of ¹³⁷Cs in humus. The transfer and retention of available ¹³⁷Cs in biomass of organisms living in humus for a long time can satisfactorily explain the longer residence time of ¹³⁷Cs in humus affected by the studied factors.