Vertical distributions of (99)Tc and the (99)Tc/(137)Cs activity ratio in the coastal water off Aomori, Japan

Using a sector-field ICP-MS the vertical distributions of the ⁹⁹Tc concentration and ⁹⁹Tc/¹³⁷Cs activity ratio were measured in the coastal waters off Aomori Prefecture, Japan, where a spent-nuclear-fuel reprocessing plant has begun test operation. The ⁹⁹Tc concentrations in surface water ranged from 1.8 to 2.4 mBq/m³, no greater than the estimated background level. Relatively high ⁹⁹Tc/¹³⁷Cs activity ratios (10-12 × 10⁻⁴) would be caused by the inflow of the high-⁹⁹Tc/¹³⁷Cs water mass from the Japan Sea. There is no observable contamination from the reprocessing plant in the investigated area. The ⁹⁹Tc concentration and the ⁹⁹Tc/¹³⁷Cs activity ratio in water column showed gradual decreases with depth. Our results implied that ⁹⁹Tc behaves in a more conservative manner than ¹³⁷Cs in marine environments.     

Environmental fate and distribution of technetium-99 in a deciduous forest ecosystem

The aims of the present research are to describe the uptake of ⁹⁹Tc by trees intercepting contaminated groundwater from a radioactive waste storage site, to identify the major ⁹⁹Tc pools within the woodland ecosystem and to assess the relative mobility of ⁹⁹Tc in the existing element cycle. Technetium in the groundwater freely passed through a dialysis membrane with a molecular weight exclusion limit of approximately 3500 amu and ⁹⁹Tc in the groundwater chromatographed on Biogel P-2 in a manner similar to pertechnetate anion (TcO₄⁻). Reducing conditions and organic associations at the study site were probably responsible for the relatively large amount (83–92%) of the ⁹⁹Tc that was nonextractable from soil by 0·01 m CaCl₂. More than one-third of the ⁹⁹Tc was released from the soil by oxidizing reagents, indicating the presence of chemically reduced forms. The highest average ⁹⁹Tc concentrations in vegetation were found in herbaceous plants (18 530 pCi g⁻¹ dry wt). Although ⁹⁹Tc was progressively accumulated over the growing season in tree leaves, average concentrations in tree wood and twigs were equal to or greater than concentrations in leaves. Tree wood was the major above-ground pool for ⁹⁹Tc because of the high concentrations in wood as well as the large amount of wood relative to other biomass at the site. Technetium was not easily leached from the trees by rainfall and was not readily extractable from forest floor leaf litter by water. The relative importance of return pathways for ⁹⁹Tc to the forest floor was leaf fall>stemflow >throughfall, indicating that ⁹⁹Tc was conserved by the trees. Snails and millipedes from the leaf litter layer concentrated technetium 20- and 16-fold, respectively, above levels found in the soil. Pertechnetate was rendered less bioavailable after ingestion by a leaf litter macroinvertebrate (Porcellio sp.) common to the study site.     

Medical radioisotopes in the environment – following the pathway from patient to river sediment

Motivated by the detection of ¹³¹I in river sediment in routine long-term surveillance samples, a systematic short-term study of the wastewater treatment chain was planned and conducted. Inflow, effluent and primary sludge were collected on a daily basis during two weeks at a regional wastewater treatment plant. Samples were investigated by gamma spectroscopy. Four medically used isotopes could be identified (¹³¹I and ^99mTc regularly, ¹⁵³Sm and ¹²³I sporadically). The concentration levels coincide well with literature data for ¹³¹I, and with our own long-term data for ¹³¹I and ^99mTc for the same plant. Cosmogenic ⁷Be activity in primary sludge correlated well with rainfall intensity. Surface sediment was sampled at low tide at both shores of the river, up- and downstream of the plant. ¹³¹I was identified in all samples, with a sharp maximum (about 100 Bq kg⁻¹ d.m.) at the discharge point of the plant and lower levels elsewhere, decreasing monotonically in downstream direction. ⁷Be and ¹³⁷Cs showed the same behaviour, but no peak at the discharge point. Predictions from simple equilibrium models for the transport and sedimentation of ¹³¹I show good agreement with the experimental data and suggest that the wastewater treatment plant is the main source for this isotope.     

Availability of 99Tc in undisturbed soil cores

Models for safety assessment of radioactive waste repositories need accurate values of the soil-to-plant transfer of radionuclides. In oxidizing environments, (99)Tc is expected to occur as pertechnetate ((99)TcO(4)(-)). Due to its high mobility, leaching of this element in the field might be important, potentially affecting the reliability of estimated transfer parameters of (99)Tc as measured in closed experimental systems such as hydroponics or pot experiments. The aim of this experiment was to measure the leaching of (99)Tc in undisturbed irrigated soil cores under cultivation as well as plant uptake and to study the possible competition between the two transfer pathways. Undisturbed soil cores (50 x 50 cm) were sampled from a Rendzic Leptosol (R), a colluvial Fluvic Cambisol (F) and a Dystric Cambisol (D) using PVC tubes (three cores sampled per soil type). Each core was equipped with a leachate collector at the bottom, allowing the monitoring of (99)Tc leaching through the cores. Cores were placed in a greenhouse and maize (Zea mays L., cv. DEA, Pioneer) was sown. After 135 d, maize was harvested and radioactivity determined in both plant and water samples. Results showed that during the growing period, leaching of (99)Tc was limited, due to the high evapotranspiration rate of maize. After harvest, leaching of (99)Tc went on because of the absence of evapotranspiration. Effective uptake (EU) of (99)Tc in leaves and grains was calculated. EU reached 70% of the input in the leaves and was not significantly different among soils. These results confirmed those obtained from pot experiments, even though leaching was allowed to occur in close-to-reality hydraulical conditions. As a consequence, it was concluded that pot experiments are an adequate surrogate for more complex "close-to-reality" experimental systems for measuring transfer factors.     

Modelling the reworking effects of bioturbation on the incorporation of radionuclides into the sediment column: implications for the fate of particle-reactive radionuclides in Irish Sea sediments

A microcosm laboratory experiment was conducted to determine the impact of biological reworking by the ragworm Nereis diversicolor on the redistribution of particle-bound radionuclides deposited at the sediment-water interface. Over the course of the 40-day experiment, as much as 35% of a ¹³⁷Cs-labelled particulate tracer deposited on the sediment surface was redistributed to depths of up to 11 cm by the polychaete. Three different reworking models were employed to model the profiles and quantify the biodiffusion and biotransport coefficients: a gallery-diffuser model, a continuous sub-surface egestion model and a biodiffusion model. Although the biodiffusion coefficients obtained for each model were quite similar, the continuous sub-surface egestion model provided the best fit to the data. The average biodiffusion coefficient, at 1.8 ± 0.9 cm² y⁻¹, is in good agreement with the values quoted by other workers on the bioturbation effects of this polychaete species. The corresponding value for the biotransport coefficient was found to be 0.9 ± 0.4 cm y⁻¹. The effects of non-local mixing were incorporated in a model to describe the temporal evolution of measured ⁹⁹Tc and ⁶⁰Co radionuclide sediment profiles in the eastern Irish Sea, influenced by radioactive waste discharged from the Sellafield reprocessing plant. Reworking conditions in the sediment column were simulated by considering an upper mixed layer, an exponentially decreasing diffusion coefficient, and appropriate biotransport coefficients to account for non-local mixing. The diffusion coefficients calculated from the ⁹⁹Tc and ⁶⁰Co cores were in the range 2-14 cm² y⁻¹, which are consistent with the values found by other workers in the same marine area, while the biotransport coefficients were similar to those obtained for a variety of macrobenthic organisms in controlled laboratories and field studies.     

Plant uptake of neptunium-237 and technetium-99 under field conditions

Plant uptake of ⁹⁹Tc freshly added to soils was compared with uptake of ⁹⁹Tc ‘aged’ in soil for more than a decade. A combination of alkaline soil and freshly added ⁹⁹Tc resulted in elevated uptake into radish foliage (plant/soil concentration ratios ranged from 37 to 46). Neptunium-237 was freshly added to all soils. Neptunium uptake via plant roots into foliage was strongly affected by soil pH. Neptunium uptake was greatest from acidic soils. The observed plant/soil concentration ratios for ²³⁷Np under field conditions were approximately 10⁻² from acidic soils (pH 5·6–5·7) and were comparable to field concentration ratios for ²³⁹Pu, that is 10⁻³, from a basic soil (pH 7·5).     

Influence of climatic conditions and soil type on 99TcO4- uptake by rye grass

Climatic changes over the long term will modify significantly the biosphere, with glaciation events probably taking place in the next 100 000 years. This is important to safety assessments of nuclear waste disposal facilities that contain high-level and long-lived waste.The soils will evolve toward new situations, and their properties will be consequently modified (e.g. an increase of soil organic matter may be expected in a cooler climate). These changes in soil properties would affect the mobility and the soil-to-plant transfer of radionuclides such as (99)Tc. This study aimed at simulating the cooling of climatic conditions for soils representative of a Jurassic limestone plateau, and the effect on transfer parameters of (99)TcO(4)(-) in the soil-plant systems was investigated. The cooler conditions were simulated by increasing elevation, a surrogate for climate change. Soils were sampled in similar geological background and topography at different elevations in the north east of France (Lorraine and Jura). Soil/solution distribution coefficients (K(d)) of (99)TcO(4)(-) were measured on soil samples in short-term batch experiments with 1:10 soil:solution ratio. Rye grass was grown on the soils spiked with (99)TcO(4)(-) at temperature regimes adapted to each soil. Also, two different temperature regimes (cold and temperate) were applied to one soil to test the effect of plant physiology and evapotranspiration on (99)TcO(4)(-) uptake. K(d) values did not show significant differences among soils in aerobic conditions, and were not significantly different from 0. During plant culture, reduction of (99)Tc was never totally achieved in soils, including in a peaty OM soil. Concentration ratios (CR) were calculated on a dry weight basis and ranged from 20 to 370. CR were always higher in high temperature regimes than in cold temperatures. They were also inversely correlated with soil organic matter (OM) content. A decrease of CR values from 5 to 10-fold was observed with increasing soil OM. Results suggested that the water holding capacity, in which (99)Tc is diluted, the nitrification potential of the soils and the evapotranspiration of plants (efficiency of uptake of soluble (99)TcO(4)(-)) were strongly involved in these differences.     

Determination of bioavailable rhenium fraction in agricultural soils

Rhenium (Re) mobility in agricultural soils was studied in order to obtain information relevant to (99)Tc mobility in soil-to-plant systems. Since water soluble Tc and Re are highly bioavailable, extraction of Re with water was carried out in addition to a total Re determination in the soils. The geometric means of total Re for paddy field, upland field and other soils were 0.34, 0.23, and 0.28 ng g(-1), respectively, while those of water soluble Re (<0.45 microm membrane filterable) were 0.053, 0.015 and 0.008 ng g(-1), respectively. There were no differences for total Re among soil uses; however, the water soluble Re/total Re ratio was significantly higher in paddy field soils (16%) than in other soil uses (6% for upland fields and 3% for other uses). Rhenium mobility and plant availability were higher in paddy fields than in other agricultural fields, and similar phenomena would be expected for (99)Tc.     

99Tc in the sub-arctic food chain Lichen-Reindeer-man

The deposition, migration and annual variations of ⁹⁹Tc fallout in carpets of lichen collected during the period 1956–1981 have been investigated. The transfer of ⁹⁹Tc to reindeer and man has also been studied. Technetium showed a shorter mean residence time than ¹³⁷Cs in the lichen carpet. The activity ratio ⁹⁹Tc/¹³⁷Cs was generally lower than the theoretical fission ratio of 1·43 × 10⁻⁴. The maximum concentration of ⁹⁹Tc in lichens occurred in 1967 (ca. 60 mBq kg⁻¹) but in 1975 higher values were found than would have been predicted from fallout. The average depth integrated concentration of ⁹⁹Tc at 62·3°N, 12·4° E in 1972 was 540 ± 100 mBq m⁻². The studies of reindeer tissues show that technetium has a short mean residence time in the muscle tissues (ca. 5 days) and is not accumulated like ¹³⁷Cs. The committed dose equivalent from ⁹⁹Tc to the local Lapp population engaged in reindeer breeding is negligible.     

Cesium-137 contamination of oak (Quercus petrae Liebl.) from sub-mediterranean zone in South Bulgaria

This study focuses on the cesium-137 (¹³⁷Cs) contamination in grass and in different compartments of oak trees growing in ecosystems, located in the zone with sub-mediterranean climate in South Bulgaria, characterized with high summer temperatures, low precipitation and often periods of drought. In 2008, three experimental sites - PP1, PP2, PP3 - were sampled in oak ecosystems from Maleshevska Mountain at 900 m above sea level. Samples from grass species and oak tree leaves, branches with different diameter, wood disks and bark were analyzed for ¹³⁷Cs activity with γ-spectrometry. The soil-to-plant transfer factor (TF) values for ¹³⁷Cs were estimated differentiating different tree compartments. Our findings showed relatively high activity concentrations of ¹³⁷Cs in oak trees even 22 years after the Chernobyl accident. The grass under oak was less contaminated compared with the oak trees. The different organs of oak trees could be distinguished according to the ¹³⁷Cs contamination as follows: bark > branches (d < 1 cm) > leaves > branches (d > 3 cm) > wood. The relatively higher contamination of bark compared with the new-formed biomass suggested that a significant part of ¹³⁷Cs was accumulated as a result of direct adsorption at the time of the main contamination event. The TF values obtained and the presence of ¹³⁷Cs in the branches, leaves and in the wood formed after 1986 confirmed that 22 years after the contamination, the main mechanism of ¹³⁷Cs entrance in tree biomass was the root uptake.     

Spatial variability of fallout-90Sr in soil and vegetation of an alpine pasture

According to the soil-to-plant transfer concept generally used in dose assessment modeling, the plant uptake of a radionuclide should depend linearly on its concentration in the soil. In order to validate this concept for (90)Sr in a semi-natural ecosystem, plant and soil samples were taken at 100 plots of a 100 x 100 m(2) area within an alpine pasture near Berchtesgaden, Germany. At three plots, the vertical distribution of (90)Sr in the soil was determined in addition. A statistically significant correlation between the soil and plant concentration of (90)Sr was not detectable (Spearman correlation coefficient R=-0.116, p>0.05) within the range of the Sr-concentration covered (15-548 Bq kg(-1) dry soil and 17-253 Bq kg(-1) dry plant material). Thus, the prerequisite of the soil-to-plant transfer concept was not fulfilled for (90)Sr at this site. Organic carbon and total nitrogen were also determined in the soil samples. Both elements were highly correlated (R=0.912, p<0.001), their ratio being C/N=10.9+/-0.7. While C was positively correlated with the (90)Sr concentrations in the soil (R=0.342, p<0.001), negative correlations were observed for the plant concentrations (R=-0.286, p<0.01) and the concentration ratios (R=-0.444, p<0.001) of (90)Sr. These results are compared with those recently obtained for (137)Cs by Bunzl et al. (J Environ Radioactiv 48 (2000) 145).     

Inter-taxa differences in root uptake of 103/106Ru by plants

Ruthenium-106 is of potential radioecological importance but soil-to-plant Transfer Factors for it are available only for few plant species. A Residual Maximum Likelihood (REML) procedure was used to construct a database of relative (103/106)Ru concentrations in 114 species of flowering plants including 106 species from experiments and 12 species from the literature (with 4 species in both). An Analysis of Variance (ANOVA), coded using a recent phylogeny for flowering plants, was used to identify a significant phylogenetic effect on relative mean (103/106)Ru concentrations in flowering plants. There were differences of 2,465-fold in the concentration to which plant species took up (103/106)Ru. Thirty-nine percent of the variance in inter-species differences could be ascribed to the taxonomic level of Order or above. Plants in the Orders Geraniales and Asterales had notably high uptake of (103/106)Ru compared to other plant groups. Plants on the Commelinoid monocot clades, and especially the Poaceae, had notably low uptake of (103/106)Ru. These data demonstrate that plant species are not independent units for (103/106)Ru concentrations but are linked through phylogeny. It is concluded that models of soil-to-plant transfer of (103/106)Ru should assume that; neither soil variables alone affect transfer nor plant species are independent units, and taking account of plant phylogeny might aid predictions of soil-to-plant transfer of (103/106)Ru, especially for species for which Transfer Factors are not available.     

Risks associated with the transfer of toxic organo-metallic mercury from soils into the terrestrial feed chain

Although the transfer of organo-metallic mercury (OrgHg) in aquatic food webs has long been studied, it has only been recently recognized that there is also accumulation in terrestrial systems. There is still however little information about the exposure of grazing animals to OrgHg from soils and feed as well as on risks of exposure to animal and humans.In this study we collected 78 soil samples and 40 plant samples (Lolium perenne and Brassica juncea) from agricultural fields near a contaminated industrial area and evaluated the soil-to-plant transfer of Hg as well as subsequent trophic transfer. Inorganic Hg (IHg) concentrations ranged from 0.080 to 210 mg kg^− 1 d.w. in soils, from 0.010 to 84 mg kg^− 1 d.w. in roots and from 0.020 to 6.9 mg kg^− 1 d.w. in shoots. OrgHg concentrations in soils varied between 0.20 and 130 μg kg^− 1 d.w. representing on average 0.13% of the total Hg (THg). In root and shoot samples OrgHg comprised on average 0.58% (roots) and 0.66% (shoots) of THg. Average bioaccumulation factors (BAFs) for OrgHg in relation to soil concentrations were 3.3 (for roots) and 1.5 (for shoots).The daily intake (DI) of THg in 33 sampling sites exceeded the acceptable daily intake (ADI) of THg of both cows (ADI = 1.4 mg d^− 1) and sheep (ADI = 0.28 mg d^− 1), in view of food safety associated with THg in animal kidneys. Estimated DI of OrgHg for grazing animals were up to 220 μg d^− 1 (for cows) and up to 33 μg d^− 1 (for sheep).This study suggested that solely monitoring the levels of THg in soils and feed may not allow to adequately taking into account accumulation of OrgHg in feed crops and properly address risks associated with OrgHg exposure for animals and humans. Hence, the inclusion of limits for OrgHg in feed quality and food safety legislation is advised.     

Weather-dependent change of cesium,strontium, barium and tellurium contamination deposited as aerosols on various cultures

Various types of plants (wheat, bean, lettuce, radish and grass) were contaminated by dry deposition of radioactive aerosols (¹³⁷Cs, ⁸⁵Sr, ¹³³Ba and ^123mTe) in order to supplement the radioecological data necessary for operational post-accidental codes. A few days after deposition, rainfalls were applied to these cultures to evaluate the influence of some characteristics of the rain on the contamination of the culture over time. On the other hand, for wheat and bean, the influence of the humidity condition of the foliage at the contamination time was considered. For a given plant species at a given vegetative stage, the four radionuclides were intercepted in an identical way. The interception varied from 30% for bean (young sprout) to 80% for lettuce (near maturity). The global transfer factor values were dependent on both the radionuclides and the plant species; nevertheless, a higher value was obtained for cesium, regardless of the plant and the rainfall (from 0.006 m² kg_fresh⁻¹ for wheat-grains – contaminated at the shooting stage – or for bean-pods – contaminated at the pre-flowering stage – to 0.1 m² kg_fresh⁻¹ for a whole lettuce). The analysis of the results allowed us on the one hand, to extract parameter values of the foliar transfer directly usable in operational codes, in particular those relating to barium and tellurium, unknown until then, and on the other hand, to lay the foundations of a future, more mechanistic model, taking into account the foliar processes in a finer way.     

Soil availability,plant uptake and soil to plant transfer of 99Tc--a review

The fission yield of 99Tc from 239Pu and 235U is similar to that of 137Cs or 90Sr and it is therefore an important component of nuclear weapons fall-out, nuclear waste and releases from nuclear facilities. There is particular current interest in 99Tc transfer from soil to plants for: (a) environmental impact assessments for terrestrial nuclear waste repositories, and (b) assessments of the potential for phytoextraction of radionuclides from contaminated effluent and soil. Vascular plants have a high 99Tc uptake capacity, a strong tendency to transport it to shoot material and accumulate it in vegetative rather than reproductive structures. The mechanisms that control 99Tc entry to plants have not been identified and there has been little discussion of the potential for phytoextraction of 99Tc contaminated effluents or soil. Here we review soil availability, plant uptake mechanisms and soil to plant transfer of 99Tc in the light of recent advances in soil science, plant molecular biology and phytoextraction technologies. We conclude that 99Tc might not be highly available in the long term from up to 50% of soils worldwide, and that no single mechanism that might be easily targeted by recombinant DNA technologies controls 99Tc uptake by plants. Overall, we suggest that Tc might be less available in terrestrial ecosystems than is often assumed but that nevertheless the potential of phytoextraction as a decontamination strategy is probably greater for 99Tc than for any other nuclide of radioecological interest.     

Spatio-temporal variations in the technetium-99 content of fucus serratus in the english channel during 1982–1984

Spatio-temporal variations in the technetium-99 content of Fucus serratus samples from the French coast of the English Channel were studied between 1982 and 1984 using various sampling strategies. The lack of constancy in measurements from within the seaweed zone of the same station is revealed by a variation of 18% in the mean contents of samples collected from different sampling levels, a variation which reaches 41% if the extreme values of all results are taken into account. Regional variations over the Channel as a whole show an asymmetric diminution of the ⁹⁹Tc content of the seaweed on the two sides of the liquid effluent discharge outlet from the reprocessing plant at La Hague and this confirms a predominant drift of Channel waters towards the North Sea. Variations with time at three stations during 1983 and 1984 have revealed that there is a time-lag between fluctuations observed in the discharges and those in F. serratus. In addition, a periodic component observed at the Roscoff and Wimereux stations, where the ⁹⁹Tc content of the seaweed varies by a factor of 2–3 between winter and summer periods, could be correlated with seasonal changes both in the metabolic state of F. serratus and in the currents to the south-west of Cap de La Hague. ⁹⁹Tc, which here has no radiological impact on man, would thus appear to be a radioactive label for sea waters and one which is particularly sensitive to variations in environmental conditions.     

Plant/soil concentration ratios for paired field and garden crops, with emphasis on iodine and the role of soil adhesion

In the effort to predict the risks associated with contaminated soils, considerable reliance is placed on plant/soil concentration ratio (CR) values measured at sites other than the contaminated site. This inevitably results in the need to extrapolate among the many soil and plant types. There are few studies that compare CR among plant types that encompass both field and garden crops. Here, CRs for 40 elements were measured for 25 crops from farm and garden sites chosen so the grain crops were in close proximity to the gardens. Special emphasis was placed on iodine (I) because data for this element are sparse. For many elements, there were consistent trends among CRs for the various crop types, with leafy crops > root crops ≥ fruit crops ≈ seed crops. Exceptions included CR values for As, K, Se and Zn which were highest in the seed crops. The correlation of CRs from one plant type to another was evident only when there was a wide range in soil concentrations. In comparing CRs between crop types, it became apparent that the relationships differed for the rare earth elements (REE), which also had very low CR values. The CRs for root and leafy crops of REE converged to a minimum value. This was attributed to soil adhesion, despite the samples being washed, and the average soil adhesion for root crops was 500 mg soil kg⁻¹ dry plant and for leafy crops was 5 g kg⁻¹. Across elements, the log CR was negatively correlated with log Kd (the soil solid/liquid partition coefficient), as expected. Although, this correlation is expected, measures of correlation coefficients suitable for stochastic risk assessment are not frequently reported. The results suggest that r ≈ −0.7 would be appropriate for risk assessment.     

Polonium (210Po) and lead (210Pb) in marine organisms and their transfer in marine food chains

The determination of ²¹⁰Po and ²¹⁰Pb was performed in marine organisms from the seashore to abyssal depths, encompassing a plethora of species from the microscopic plankton to the sperm whale. Concentrations of those radionuclides ranged from low values of about 5 × 10⁻¹ Bq kg⁻¹ (wet wt.) in jellyfish, to very high values of about of 3 × 10⁴ Bq kg⁻¹ (wet wt.) in the gut walls of sardines, with a common pattern of ²¹⁰Po > ²¹⁰Pb.These radionuclides are primarily absorbed from water and concentrated by phyto- and microzooplankton, and then are transferred to the next trophic level along marine food chains. Investigation in epipelagic, mesopelagic, bathypelagic and abyssobenthic organisms revealed that ²¹⁰Po is transferred in the marine food webs with transfer factors ranging from 0.1 to 0.7, and numerically similar to those of the energy transfer in the marine food chains. As ²¹⁰Po preferentially binds to amino acids and proteins, its transfer in food chains likely traces protein transfer and, thus, ²¹⁰Po transfer factors are similar to ecotrophic coefficients. ²¹⁰Pb is transferred less efficiently in marine food chains and this contributes to increased ²¹⁰Po:²¹⁰Pb activity ratios in some trophic levels.     

Growth, yield and elements content of wheat (Triticum aestivum) grown in composted municipal solid wastes amended soil

A commercial formulation of composted municipal solid wastes (MSW) was used for amending soil at 0, 50, 100, 150, 200 and 250 kg ha⁻¹ in which wheat had been grown (field experiments) and element residues of amended soil and plant parts were enumerated. MSW amendment caused a significant improvement in soil quality. Growth (shoot length, leaf number, leaf area, tiller number, plant dry weight and chlorophyll contents of leaves) and yield (length of panicle, number of panicles per plant and grain yield per plant) of wheat increased gradually up to the MSW-amendment level of 200 kg ha⁻¹. Elements, Ni, Zn, Cu, Cd, Cr, and Pb accumulated in plants from MSW amended soil, but the degree of metal accumulation was the least in seeds in comparison to other plant parts (root, stem and leaf). Moreover, Ni, Zn, Cd and Pb, were in high concentration in all plant parts. It is recorded that the level of 200 kg ha⁻¹ MSW amendment caused better growth and yield of wheat, but progressive levels of metal accumulation in plant parts were recorded due to increase in amendment levels. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Transfer factors of Polonium from soil to parsley and mint

Transfer factors of ²¹⁰Po from soil to parsley and mint have been determined. Artificial polonium isotope (²⁰⁸Po) was used as a tracer to determine transfer factor of Po from soil to plant in pot experiments. Two plant growing systems were used for this study namely, an outdoor system and a sheltered system by a polyethylene tent. ²⁰⁸Po and ²¹⁰Po were determined in soil and different parts of the studied plants (stem and leaf), using alpha spectroscopy. The results have shown that there was a clear uptake of ²⁰⁸Po by roots to leaves and stems of both plants. Higher values of transfer factors using the ²¹⁰Po activity concentrations than the ²⁰⁸Po activity concentration were observed. Transfer factors of ²¹⁰Po from soil to parsley varied between 20 × 10⁻² and 50 × 10⁻² and 22 × 10⁻³ and 67 × 10⁻³ in mint, while ²⁰⁸Po transfer factors varied between 4 × 10⁻² and 12 × 10⁻² for parsley and 10 × 10⁻² and 22 × 10⁻² in mint. Transfer factors of Po were higher in those plants grown in the sheltered system than in the open system; about 75% of Po was transferred from atmosphere to parsley parts using the two systems. Ratios of transferred Po from soil to mint stem and leaf in the sheltered system were higher by 2 times from those in the open system.