The clay mineral
composition of four brown forest soil profiles (Luvisols) developed on
different parent rocks was studied in detail to determine the major clay
mineral alteration processes. In the studied profiles a siltstone bedrock
weathered to chlorite/vermiculite and vermiculite in a less developed, shallow
soil profile, while the major product of soil formation in a clayey,
well-developed deep soil is a typical soil montmorillonite with heterogeneous
charge distribution. The most possible pathway of clay alteration is illite
smectitization via charge reduction, and considerable degradation of smectite
in the soil formed on limestone. On the contrary, weathering of andesite parent
rock involves the formation of low charged smectite altering to high charged vermiculite
Two alternative approaches, a sequential extraction scheme and the calculation of the variation of the distribution coefficient of radiocaesum in different K–Ca–NH4 scenarios, were used to study the behaviour and fractionation of this radionuclide in a forest soil profile. The first approach was applied to samples originating from an experiment in which the original L (litter) layer was replaced by an L layer contaminated with a radioactive aerosol, allowing a downward migration of radiocaesium. The samples belonged to different stages after the contamination. The second approach was applied to samples contaminated with soluble radiocaseium. The results indicate that radiocaesium behaviour is quite similar in the Hand A layers, and that the mineral matter seems to govern the behaviour of radiocaesium in case of direct condensed deposition or when radiocaesium is released from structural components of the organic matter phase.
Authors:D Montecchio, O Francioso, P Carletti, D Pizzeghello, S Chersich, F Previtali, and S Nardi
acids (HAs) extracted from soils developed under two Norwegian spruce (Picea
abies, (L.) Karst) subalpine forests of northern Italy were characterized
using chemical, thermal (TG-DTA) and spectroscopic (DRIFT) analyses. The samples
were taken from five sites which differed in orientation (northern and southern
exposure) and vegetal cover at different old age: grassland, regeneration,
immature and mature stands. In general, the thermal patterns of HAs were similar
(three exothermic reactions appeared around at 300, 400 and 500C) in
both sites in grasslands and regeneration while a considerable modification
appeared in HA from stands of different age at northern and southern exposure
site. DRIFT spectroscopy confirmed the differences observed through TG-DTA
analysis. In particular the main structural changes were ascribed to modification
of carbonyl group and of CH stretching in aliphatic components in each HAs
from different sites.
The sorption of cadmium labeled with 109Cd in nitrate form, from aqueous solutions in different horizons of some arable and forest soils was studied under static (batch) conditions. Before sorption, a method of sequential soil treatment was applied, which consist in the consecutive removal of individual soil components by the use of appropriate reagents and procedures. Three sorption isotherms were tested. Kinetic studies showed that the sorption of cadmium is rather rapid and it can be well described by a Freundlich or a linear isotherm, whereas the closeness of Langmuir isotherm to the experimental results is lower. From the different sorption isotherms, it would also be possible to estimate the effect of individual components on the sorption of cadmium in soils. It was found that the untreated soils exhibit the highest sorption and the sorption decreases in the order of untreated > acetate treated > water treated > peroxide treated > dithionite treated soil. Sorption of cadmium increases with the depth of the studied soils disregarding their chemical treatment.
Authors:Ryoko Fujiyoshi, Yoshihiro Satake, and Takashi Sumiyoshi
Depth profiles potassium and its isotope ratio (40K/K) were investigated in several forest soils from different geological and climatic backgrounds. The ratio was found not
to be constant (0.0117%) but varied appreciably from 0.0085% to 0.0167% among different soils. Possible factors affecting
variability of 40K/K values were considered by a multivariate factor analysis which suggested that aqueous parameters like humidity and pH
might be a controlling factor in the surface soils. The amount (and probably chemical forms) of iron oxide may be another
one influencing 40K/K values in mineral components at deeper portions.
The distribution of Pu isotopes in three profiles of forest soil in Lublin region was determined. The retention half-time
and migration velocity of239,240Pu originated from global and Chernobyl fallouts was calculated. The average rate of migration of the global fallout plutonium
was 0.4 cm/year and that of the Chernobyl one 0.7 cm/year. Good correlation between Pu concentration and organic matter contents
was found only in the case of podzolic soil profile. In two profiles a good negative correlation between Pu activity and exchangeable
pH of the soil layer was determined.
Authors:Jiangfeng Guo, M. Atarashi-Andoh, and H. Amano
In Japan, about 70% of land area is covered by forest. Therefore, forest ecosystem plays a vital role in ultimate fate of radionuclides and carbon cycle in terrestrial environment. In this study, three undisturbed forest soil profiles were collected from Ibaraki Prefecture, Japan. The 137Cs data illustrate that maximum fallout deposition of 137Cs took place around 1964. 14C determination shows that 14C also has peak values in the top 10 cm of the soil profiles ascribed to the highest bomb 14C level in 1960's. The 13C data show that the turnover dynamics of soil organic carbon could be described very well by progressive enrichment values of d13C.
Preliminary picture of 137Cs radioactivity levels in forested areas in and around Izmir is illustrated. Both activity concentrations and activity depositions
of 137Cs in soil samples were determined. Their values varied from 8.29±0.27 to 445±3.16 Bq.kg−1 (d.w.) and 0.63±0.01 to 11.6±0.08 kBq.m–2 (d.w.), respectively. It was found that while activity deposition of 137Cs is normally distributed, activity concentration of 137Cs is log-normally distributed in forest soils and the activity deposition is less variable than the activity concentration.
Cesium-137 activities in soils increase with increasing elevation, annual average rainfall and soil organic matter.
The behavior of cadmium labeled with 109Cd in different depth horizons of arable and forest soils were studied under static (batch) conditions in three interconnected
processes, which consist of sorption, desorption and extraction. In the sorption, Cd2+ was applied in the aqueous calcium nitrate solution. Both untreated soils and peroxide treated soils were used in order to
remove organic matter from some of the soil samples used in parallel. The influence of the V/m ratio on the sorption coefficients was investigated in preliminary experiments with untreated soils. Contrary to the usually
short-term sorption, a long-term sorption of cadmium was investigated in untreated and treated soil horizons, which lasted
more than fortnight. Kinetic studies of sorption were carried out and cadmium concentration dependence in aqueous phase of
the second order kinetic constants was observed. For evaluation of sorption and desorption processes Freundlich isotherms
were used. It was found that the Freundlich adsorption intensity coefficient is more time dependent than the absorption capacity
coefficient, and the sorption itself consists of rapid and slow processes according to the soil constituents. Desorption and
extraction processes revealed the possibility of cadmium recovery from various soil horizons. Based on the obtained results
two- or three-stage theory of cadmium retention in soils was proposed. Some new insight into the role of organic matter in
the sorption/desorption process of cadmium is also presented.