Transfer of 137Cs and 40K from Agricultural Soils to Food Products in Terrestrial Environment of Tarapur, India

The ¹³⁷Cs and ⁴⁰K activities and transfer factors from soil to vegetables, grass, and milk from villages located around Tarapur Atomic Power Station (TAPS) were determined using high-resolution gamma spectrometry. A total of 32 soil, 21 vegetable, 23 dry paddy grass, and 23 milk samples were collected from 23 different agricultural farms from various villages around TAPS to determine transfer factors for natural environment. The mean concentration values for ¹³⁷Cs and ⁴⁰K in soil, grass, and milk were 2.39?±?0.86 Bq kg^?1, 0.31?±?0.23 Bq kg^?1, and 12.4?±?5.7 mBq L^?1 and 179?±?31 Bq kg^?1, 412?±?138 Bq kg^?1, and 37.6?±?9.3 Bq L^?1, respectively, for soil?Cgrass?Cmilk pathway. In the soil?Cvegetation pathway, the mean concentrations values for ¹³⁷Cs and ⁴⁰K were 2.15?±?1.04 Bq kg^?1, 16.5?±?7.5 mBq kg^?1, and 185?±?24, 89?±?50 Bq kg^?1, respectively. The evaluated mean transfer factors from soil?Cgrass, grass?Cmilk, and soil?Cvegetation for ¹³⁷Cs were 0.14, 0.0044, and 0.0073 and that of ⁴⁰K were 2.42, 0.0053, and 0.49, respectively. Only 15 out of total 44 milk and vegetable samples were detected positive for ¹³⁷Cs, indicating a very low level of bioavailability.     

Radionuclide levels at two sites in a water extraction area in the Netherlands after chernobyl

The coastal dune aquifer, providing drinking water for a large part of the population of the western Netherlands, is recharged by fainfall and artificial infiltration of Rhine water. Chernobyl fall-out has been detected in both water sources. At the Castricum lysimeter station the rainfall-derived water, draining from 2.25 m of unsaturated sandy soil, shows levels of Cs-137 around the detection limit of 20 to 40 mBq kg^?1. At this site, the soil itself retained some Chernobyl-derived Cs-137 in the top 10 cm, where a similar quantity of old Cs-137 has also been retained. Penetration of old Cs-137 is deeper (up to 70 cm) under oak vegetation than in the bare soil. In the infiltration channels, fed by Rhine water, the bottom mud contains only Chernobyl-derived Cs nuclides. Radioactivity from Cs-137 is about one tenth of that from natural radioactivity due to K-40. Cesium levels are apparently unrelated to adsorptive properties.     

Determination of Natural and Artificial Radionuclide Levels in Soils of Western and Southern Coastal Area of Turkey

Soil samples were collected from western and southern region of Turkey in 1995 from 17 sampling stations of different depths. Natural and artificial radionuclide activity levels of soil samples of the western and southern sea in Turkey were previously reported about nine years after the Chernobyl accident. The aim of the study was to collect data for following up of the earlier study and to present result for distributions of radionuclides in soil samples of the western and southern regions of Turkey. ²²⁶Ra is in the range 19–276 Bq kg^?1, 7–173 Bq kg^?1 for ²³⁸U, 8–244 Bq kg^?1 for ²³²Th, 86–1162 Bq kg^?1 (dry wt.) for ⁴⁰K and ¹³⁷Cs activity result varies between 1.8–82 Bq kg^?1 (dry wt.).     

Measurement of Radionuclides and Gamma-Ray Dose Rate in Soil and Transfer of Radionuclides from Soil to Vegetation, Vegetable of Some Northern Area of Pakistan Using ��-Ray Spectrometry

The analysis of gamma emitters natural radionuclides, i.e., ²²⁶Ra, ²³²Th, and ⁴⁰K, has been carried out in soil, vegetation, vegetable, and water samples collected from some Northern area of Pakistan, using gamma-ray spectrometry. The ??-ray spectrometry was carried out using high-purity Germanium detector coupled with a computer-based high-resolution multi-channel analyzer. The activity concentrations in soil ranges from 24.7 to 78.5 Bq?kg^?1, 21.7 to 75.3 Bq?kg^?1, and 298.5 to 570.8 Bq?kg^?1 for ²²⁶Ra, ²³²Th, and ⁴⁰K with the mean value of 42.1, 43.3, 9.5, and 418.3 Bq?kg^?1, respectively. In the present analysis, ⁴⁰K was the major radionuclide present in soil, vegetation, fruit, and vegetable samples. The concentration of ⁴⁰K in vegetation sample varied from 646.6 to 869.6 Bq?kg^?1 on dry weight basis. However, the concentration of ⁴⁰K in fruit and vegetable samples varied from 34.0 to 123.3 Bq?kg^?1 on fresh weight basis. In vegetation samples, along with ⁴⁰K, ²²⁶Ra, and ²³²Th were also present in small amount. The transfer factors of these radionuclides from soil to vegetation, fruit, and vegetable were also studied. The transfer factors were found in the order: ⁴⁰K?>?²³²Th????²²⁶Ra. The analysis of water samples showed activity concentrations values for all radionuclides below detection limit. The internal and external hazard indices were measured and found less than the safe limit of unity. The mean value of outdoor and indoor absorbed dose rate in air was found 64.61 and 77.54 nGy?h^?1, respectively. The activity concentrations of radionuclides found in all samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the general public.     

Recent sedimentation rates in Garaet El Ichkeul Lake, NW Tunisia, as affected by the construction of dams and a regulatory sluice

Purpose

Ichkeul National Park, NW Tunisia, is a UNESCO Biosphere Reserve. Garaet El Ichkeul Lake is known for its seasonal variability in water level and salinity. In recent decades, the waterbody has been affected by the construction of new hydraulic structures. To reduce the impacts of dams and to maintain the sustainability of the ecosystem, a sluice was built at the outlet of the lake, and it operated for the first time in 1996. This paper describes an investigation of recent sedimentation dynamics in Ichkeul Lake, determined by radiometric dating of sediment cores.

Materials and methods

A sediment core was collected with a UWITEC gravity corer at the deepest, central part of the lake in August 2009. Specific activities of unsupported lead-210 (²¹⁰Pb) and caesium-137 (¹³⁷Cs) were measured in the core, enabling calculation of recent sediment accumulation rates (SAR). Published radiometric data from nearby sediment cores, collected in 1997 and 1982, provide a comparison.

Results and discussion

The measured excess ²¹⁰Pb inventory was 5300?±?500?Bq?m^?2, leading to an estimation of constant flux of 165?±?16?Bq?m^?2?yr^?1, a value higher than the best estimate for local atmospheric fluxes (123?±?12?Bq?m^?2?yr^?1) and the flux estimated from the core collected in 1982 (48?Bq?m^?2?yr^?1). The ¹³⁷Cs inventory was 3550?±?120?Bq?m^?2, two times higher than the historical ¹³⁷Cs atmospheric deposition in the area. The ¹³⁷Cs profile displayed a distinct peak, but the ¹³⁷Cs depth-distribution did not follow the pattern expected from atmospheric deposition. Application of the constant rate of supply (CRS) model, with the reference point method, produced a chronology and SAR values comparable to those found in previous work. The whole ¹³⁷Cs profile was quantitatively reconstructed from the historical records of atmospheric deposition, using the system-time-averaged (STA) model.

Conclusions

The CRS and STA models provide consistent sediment accumulation results for the whole data set, considering the time resolution of the chronology (~6?years) and analytical uncertainties. Results from cores sampled in 1982, 1997 and 2009 reveal an increasing SAR trend, from ~0.25?g?cm^?2?yr^?1 in the early 1940s to ~0.67?g?cm^?2?yr^?1 at present. In the 13?years since installation of sluice gates at Tinja, SAR in the central Ichkeul Lake has not declined. Thus, if siltation continues at the present rate, shallowing of the lake will seriously affect the hydromorphology and ecology of this important lake.     

Transfer of Cd, Pb, Ra and U from Phosphogypsum Amended Soils to Tomato Plants

About 170 million tons of phosphogypsum (PG) are annually generated worldwide as a by-product of phosphoric acid factories. Agricultural uses of PG could become the main sink for this waste, which usually contains significant radionuclide (from the ²³⁸U-series) and toxic metals concentrations. To study PG effects on pollutant uptake by crops, a completely randomised greenhouse experiment was carried out growing Lycopersicum esculentum Mill L. on a reclaimed marsh soil amended with three PG rates (treatments), corresponding to zero (control without PG application), one, three and ten times the typical PG rates used in SW Spain (20 Mg ha^?1). The concentrations of Cd, Pb, U (by inductively coupled plasma mass spectroscopy) and ²²⁶Ra and ²¹⁰Po (by γ-spectrometry and α-counting, respectively) were determined in soil, vegetal tissue and draining water. Cadmium concentrations in fruit increased with PG rates, reaching 44?±?7 μg kg^?1 formula weight with ten PG rates (being 50 μg kg^?1 the maximum allowed concentration by EC 1881/2006 regulation). Cd transfer factors in non-edible parts were as high as 4.8?±?0.5 (dry weight (d.w.)), two orders of magnitude higher than values found for lead, lead, uranium and radium concentrations in fruit remained below the corresponding detection limits—0.5 and 0.25 mg kg^?1 and 0.6 mBq kg^?1, respectively (in a d.w. basis). ²³⁸U (up to 7 μg kg^?1 d.w.) and ²¹⁰Po (up to 0.74 Bq kg^?1 d.w.) could be measured in some fruit samples by α-spectrometry. Overall, the concentrations of these metals and radionuclides in the draining water accounted for less than 1% of the amount applied with PG.     

Inoculation of arbuscular mycorrhizal fungi can substantially reduce phosphate fertilizer application to Allium fistulosum L. and achieve marketable yield under field condition

The effects of inoculating arbuscular mycorrhizal (AM) fungi on the growth, phosphorus (P) uptake, and yield of Welsh onion (Allium fistulosum L.) were examined under the non-sterile field condition. Welsh onion was inoculated with the AM fungus, Glomus R-10, and grown in a glasshouse for 58?days. Non-inoculated plants were grown as control. Inoculated and non-inoculated seedlings were transplanted to a field with four available soil P levels (300, 600, 1,000, and 1,500?mg P₂O₅?kg^?1 soil) and grown for 109?days. AM fungus colonization, shoot P concentration, shoot dry weight, shoot length, and leaf sheath diameter were measured. Percentage AM fungus colonization of inoculated plants was 94% at transplant and ranged from 60% to 77% at harvest. Meanwhile, non-inoculated plants were colonized by indigenous AM fungi. Shoot length and leaf sheath diameter of inoculated plants were larger than those of non-inoculated plants grown in soil containing 300 and 600?mg P₂O₅?kg^?1 soil. Shoot P content of inoculated plants was higher than that of non-inoculated plants grown in soil containing 300 and 600?mg P₂O₅?kg^?1 soil. Yield (shoot dry weight) was higher for non-inoculated plants grown in soil containing 1,000 and 1,500?mg P₂O₅?kg^?1 soil than for those grown in soil containing 300 and 600?mg?P₂O₅ kg^?1 soil. Meanwhile, the yields of inoculated plants (200?g plant^?1) grown in soils containing the four P levels were not significantly different. Yield of inoculated plants grown in soil containing 300?mg P₂O₅ kg^?1 soil was similar to that of non-inoculated plants grown in soil containing 1,000?mg P₂O₅?kg^?1 soil. The cost of AM fungal inoculum for inoculated plants was US$ 2,285?ha^?1 and lower than the cost of superphosphate (US$ 5,659?ha^?1) added to soil containing 1,000?mg P₂O₅ kg^?1 soil for non-inoculated plants. These results indicate that the inoculation of AM fungi can achieve marketable yield of A. fistulosum under the field condition with reduced application of P fertilizer.     

Seasonal variations in natural 13C abundances in C3 and C4 plants collected in Thailand and the Philippines

Abstract

The natural ¹³C abundance (δ ¹³C) of plant leaves collected from fields in Thailand and the Philippines (Asian Monsoon tropics) was analyzed, and changes in the δ ¹³C values of C₃ and C₄ plants in wet and dry seasons were characterized. In Thailand, the δ ¹³C values of C₃ plants were ?29.2?±?1.04 (mean?±?standard deviation) ‰ in July and August (wet season) and ?28.6?±?1.05‰ in February and March (dry season): these values are not significantly different, whereas the values of C₄ plants were ?12.7?±?0.56‰ in the wet season and ?14.5?±?0.68‰ in the dry season (P?<?0.01, t-test). In the Philippines, where plants were collected only in October (late wet season), the δ ¹³C values of C₃ plants were ?29.5?±?1.28‰, whereas those of C₄ plants were ?12.6?±?1.11‰. These results suggest that under an Asian Monsoon climate, C₄ plants exhibit more negative δ ¹³C values in the dry season than in the wet season, whereas C₃ plants as a whole show no clear seasonal changes in δ ¹³C values.     

Nitrous oxide emissions from a rainfed-cultivated black soil in Northeast China: effect of fertilization and maize crop

Nitrous oxide emission (N₂O) from applied fertilizer across the different agricultural landscapes especially those of rainfed area is extremely variable (both spatially and temporally), thus posing the greatest challenge to researchers, modelers, and policy makers to accurately predict N₂O emissions. Nitrous oxide emissions from a rainfed, maize-planted, black soil (Udic Mollisols) were monitored in the Harbin State Key Agroecological Experimental Station (Harbin, Heilongjiang Province, China). The four treatments were: a bare soil amended with no N (C0) or with 225?kg?N ha^?1 (CN), and maize (Zea mays L.)-planted soils fertilized with no N (P0) or with 225?kg?N ha^?1 (PN). Nitrous oxide emissions significantly (P?<?0.05) increased from 141?±?5?g N₂O-N?ha^?1 (C0) to 570?±?33?g N₂O-N?ha^?1 (CN) in unplanted soil, and from 209?±?29?g N₂O-N?ha^?1 (P0) to 884?±?45?g N₂O-N?ha^?1 (PN) in planted soil. Approximately 75?% of N₂O emissions were from fertilizer N applied and the emission factor (EF) of applied fertilizer N as N₂O in unplanted and planted soils was 0.19 and 0.30?%, respectively. The presence of maize crop significantly (P?<?0.05) increased the N₂O emission by 55?% in the N-fertilized soil but not in the N-unfertilized soil. There was a significant (P?<?0.05) interaction effect of fertilization?×?maize on N₂O emissions. Nitrous oxide fluxes were significantly affected by soil moisture and soil temperature (P?<?0.05), with the temperature sensitivity of 1.73–2.24, which together explained 62–76?% of seasonal variation in N₂O fluxes. Our results demonstrated that N₂O emissions from rainfed arable black soils in Northeast China primarily depended on the application of fertilizer N; however, the EF of fertilizer N as N₂O was low, probably due to low precipitation and soil moisture.     

Radiological maps for fallout 7Be in forest soil horizons in a mountainous area of Turkey

Due to the paucity of data on separate spatial distribution of cosmogenic ⁷Be radionuclide activities in forest soil layers, a spatial study was performed in Mount Ida (Kazdagi)/Edremit, Turkey. In this study, it was aimed to examine the ⁷Be spatial variability and depth distribution in the surface soil layers. The ⁷Be activity concentrations were determined by HPGe gamma spectrometry system and the distributions of ⁷Be activities in the O_L and O_F + O_H horizons throughout the region were mapped separately. Activity concentrations of ⁷Be in O_L horizons and O_F+O_H horizons varied as 35 ± 23–701 ± 40 Bq kg^?1 and 0.96 ± 0.63–197 ± 11 Bq kg^?1, respectively. ⁷Be inventories (0.20 ± 0.06–5.69 ± 0.75 kBq m^?2) in the study area were relatively higher when compared with the other regions of the world. ⁷Be inventories increased with altitude, slope and the thickness of the humus layer in some of the investigated area. Average ⁷Be activity level in deciduous forest stand type was significantly higher than that for coniferous and mixed stand types. Our limited data could not provide a latitudinal distribution pattern of ⁷Be soil inventory or precipitation dependence and further investigation is needed.     

Assessment of Radionuclides, Trace Metals and Radionuclide Transfer from Soil to Food of Jhangar Valley (Pakistan) Using Gamma-Ray Spectrometry

The gamma spectrometric analysis of soil and essential foodstuffs, e.g., wheat, millet, potato, lentils and cauliflower, which form the main component of the daily diet of the local public, was carried out using high purity germanium (HpGe) detector coupled with a computer based high-resolution multi-channel analyzer. The activity concentration in soil samples for ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 30.0 Bq kg^?1 to 81.2 Bq kg^?1, 31.4 Bq kg^?1 to 78.25 Bq kg^?1 and 308.8 Bq kg^?1 to 2177.6 Bq kg^?1, with mean values of 56.2, 58.5 and 851.9 Bq kg^?1, respectively. The average activity measured for ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples was found higher than the world average. The major radionuclide found in the food items studied was ⁴⁰K, while ²²⁶Ra, ²³²Th and ¹³⁷Cs were detected in very nominal amounts. The results clearly indicate that these radionuclides have no health hazard to human beings, as they are well below the annual limit of intake (ALI) for these radionuclides. The transfer factors of these radionuclides from soil to food were also studied. The mean transfer factors of ⁴⁰K, ²²⁶Ra, ²³²Th and ¹³⁷Cs from soil to food were estimated to be about 0.17, 0.07, 0.16 and 0.23, respectively. An artificial radionuclide, ¹³⁷Cs, was also present in detectable amount in all samples. The internal and external hazard indices were measured and had mean values of 0.70 and 0.55, respectively. Absorbed dose rates and effective dose have been determined in the present study. Concentration of trace metals, such as Cr, Pb, Ni and Zn, was also determined in the soil samples. The concentrations of radionuclides and trace metals found in these samples during the present study were nominal and do not pose any potential health hazard to the general public.     

Potential Remediation of 137Cs and90 Sr Contaminated Soil by Accumulation in Alamo Switchgrass

Cesium-137 (¹³⁷Cs) and Strontium-90 (⁹⁰Sr) are radionuclides characteristic of nuclear fallout from nuclear weapons testing and nuclear reactor accidents. Alamo switchgrass (Panicum virginatum L.) is a perennial C⁴ species native to central North America that produces exceptionally high biomass yields in short periods of time. In three separate experiments, Alamo switchgrass plants were tested for their ability to accumulate ¹³⁷ Cs and⁹⁰ Sr from a contaminated growth medium. Plants in experiment 1 were grown in 33 × 20 × 7 cm plastic pans containing 2.5 kg sand. Plants in experiments 2 and 3 were grown in 30 × 3 cm diameter test tubes containing 0.3 kg growth medium. After 3 months of plant growth, either 102 Bq ¹³⁷Cs or 73 Bq⁹⁰ Sr g^?1 soil were added to the growth medium. Plants in all three experiments were grown within a greenhouse that was maintained at 22 ± 2 °C with a photosynthetic active radiation of 400–700 µmol m^?2 s^?1 and a 14–16 h photoperiod. Above-ground plant biomass did not differ between plants that were not exposed to these radionuclides (controls) and those that were exposed to growth medium containing ¹³⁷Cs or⁹⁰ Sr over the course of the experiment. Plants accumulated 44 and 36% of the total amount of ⁹⁰Sr and¹³⁷ Cs added to growth medium after the first 5 harvests. After the first two harvests, the concentration of ¹³⁷Cs and⁹⁰ Sr in plant tissue and the amount of ¹³⁷Cs or⁹⁰ Sr removed from growth medium declined with each successive harvest. Duration of exposure correlated curvilinearly with accumulation of both ⁹⁰Sr and ¹³⁷Cs by plants (r² = 0.95 and 0.78, respectively). As concentration of both ¹³⁷Cs and ⁹⁰Sr in growth medium increased, plant accumulation of both radionuclides increased and correlated curvilinearly in seedlings (r² = 0.83 and 0.89 respectively).     

The 137Cs technique applied to steep Mediterranean slopes (Part I): the effects of lithology,slope morphology and land use

Concentrations in the soil of anthropogenic and natural radionuclides have been investigated in order to assess the applicability of the ¹³⁷Cs technique in an area of typical Mediterranean steep slopes. This technique can be used to estimate net soil redistribution rates but its potential in areas with shallow and stony soils on hard rock lithology have not been evaluated so far. In this research, the validity of using this technique in stony shallow soils at very steep slopes is discussed together with the relations between radionuclide concentrations and other soil properties, lithology, slope morphology and land use in a Mediterranean environment. Both natural Potassium-40 (⁴⁰K), Uranium-238 (²³⁸U), Thorium-232 (²³²Th) and anthropogenic Caesium-137 (¹³⁷Cs) radionuclides have been determined in samples taken along slope transects on uncultivated serpentinite soils and cultivated gneiss soils. In addition to the radionuclide concentrations, parameters such as slope position, slope angle, aspect, soil depth, surface stone cover, moss, litter, vegetation cover, soil crust, stone content and bulk density have been quantified.All the natural radionuclides ⁴⁰K, ²³⁸U, ²³²Th show significantly higher concentrations in the gneiss than in the serpentinite soils, opposed to the ¹³⁷Cs concentration, which is found significantly higher in the serpentinite soils probably because of the difference in clay mineralogy. The exponential decreasing depth distribution of ¹³⁷Cs and its homogeneous spatial distribution emphasise the applicability of the ¹³⁷Cs technique in this ecosystem.Lithology determines the concentration of natural and anthropogenic radionuclides. Land use determines the relations between ¹³⁷Cs concentration/inventory and some soil characteristics. Higher ¹³⁷Cs concentration and inventory are associated with higher percentages of vegetation cover, higher percentage of stones in the soil and higher values of soil bulk density in cultivated gneiss soils. Slope morphology and land use influence the soil redistribution at slope scale. The gneiss slopes show a zonation of four to five areas of differential erosion/accumulation processes corresponding with more regular slopes and soil redistribution due to water erosion and to tillage translocation and erosion. The serpentinites, as an example of a more unstable slope type, show more erosion areas with less accumulation downslope and soil redistribution due to water erosion.     

Pilot-scale counter-current acid leaching process for Cu,Pb, Sb,and Zn from small-arms shooting range soil

Purpose

The main objective of this study was to evaluate the potential of a counter-current leaching process (CCLP) on 14 cycles with leachate treatment at the pilot scale for Pb, Cu, Sb, and Zn removal from the soil of a Canadian small-arms shooting range.

Materials and methods

The metal concentrations in the contaminated soil were 904?±?112 mg Cu kg^–1, 8,550?±?940 mg Pb kg^–1, 370?±?26 mg Sb kg^–1, and 169?±?14 mg Zn kg^–1. The CCLP includes three acid leaching steps (0.125 M H₂SO₄?+?4 M NaCl, pulp density (PD)?=?10 %, t?=?1 h, T?=?20 °C, total volume?=?20 L). The leachate treatment was performed using metal precipitation with a 5-M NaOH solution. The treated effluent was reused for the next metal leaching steps.

Results and discussion

The average metal removal yields were 80.9?±?2.3 % of Cu, 94.5?±?0.7 % of Pb, 51.1?±?4.8 % of Sb, and 43.9?±?3.9 % of Zn. Compared to a conventional leaching process, the CCLP allows a significant economy of water (24,500 L water per ton of soil), sulfuric acid (133 L H₂SO₄ t^–1), NaCl (6,310 kg NaCl t^–1), and NaOH (225 kg NaOH t^–1). This corresponds to 82 %, 65 %, 90 %, and 75 % of reduction, respectively. The Toxicity Characteristic Leaching Procedure test, which was applied on the remediated soil, demonstrated a large decrease of the lead availability (0.8 mg Pb L^–1) in comparison to the untreated soil (142 mg Pb L^–1). The estimated total cost of this soil remediation process is 267 US$ t^–1.

Conclusions

The CCLP process allows high removal yields for Pb and Cu and a significant reduction in water and chemical consumption. Further work should examine the extraction of Sb from small-arms shooting range.     

Effect of the application of polluted wheat (Triticum aestivum L. Thell.) straw during plowing on the transfer of radiocesium from the soil to komatsuna (Brassica rapa L. var. perviridis)

Radioactive substances were released into the environment after the nuclear accident at the Fukushima Daiichi Nuclear Power Station; this led to the contamination of the soil at Fukushima Prefecture. Mixing of organic matter with soil during plowing is known to influence radiocesium (¹³⁴Cs and ¹³⁷Cs) absorption by crops. However, the effect of mixing organic matter polluted by radioactive substances during plowing on radiocesium absorption by plants is not yet known. The aim of this study was to investigate the effect on the radiocesium absorption by komatsuna (Brassica rapa L. var. perviridis) cultivated in a 45-L container containing Andosol (14,300 Bq kg^?1) or Gray Lowland soil (33,500 Bq kg^?1) mixed with polluted wheat (Triticum aestivum L. Thell.) straw (2080 Bq kg^?1). The radiocesium concentration of the plants and the soil and the amount of exchangeable radiocesium in the soil were determined using a germanium semiconductor. The transfer of radiocesium from the soil to plants decreased by 53 and 27% in Andosol and Gray Lowland soil, respectively, after the application of 10 t ha^?1 polluted wheat straw. This reduction in the level of radiocesium transfer might be attributed to potassium contained in the wheat straw, which might compete with cesium during membrane transport and thereby block the transport of cesium from the soil solution to the roots and from the roots to the shoots. Alternatively, the applied wheat straw probably absorbed radiocesium and decreased the amount of exchangeable radiocesium in the soil. Our findings suggest that the mixing of polluted wheat straw with contaminated soil might influence the absorption of radiocesium content by agricultural products. Further studies are warranted to determine the long-term effects of the application of polluted wheat straw on the rate of radiocesium transfer to crops.     

Lantana camara——an Ecological Bioindicator Plant for Decontamination of Pb-Impaired Soil Under Organic Waste-Supplemented Scenarios

Heavy metal extraction and processing from ores releases elements into the environment. Soil, being an "unfortunate" sink, has its bionomics impaired and affected by metal pollution. Metals sneak into the food chain and pose risk to humans and other edaphicdependent organisms. For decontamination, the use of an ecosystem-friendly approach involving plants is known as phytoremediation.In this study, different lead(Pb) concentrations(80, 40, 20, and 10 mg kg~(-1)) were used to contaminate a well-characterized soil,(un)supplemented with organic waste empty fruit bunch(EFB) or spent mushroom compost(SMC), with non-edible plant—Lantana camara. Lead removal by L. camara ranged from 45.51% to 88.03% for supplemented soil, and from 23.7% to 57.8% for unsupplemented soil(P 0.05). The EFB-supplemented and L. camara-remediated soil showed the highest counts of heavy metal-resistant bacteria(HMRB)(79.67 × 10~6–56.0 × 10~6 colony forming units(CFU) g~(-1) soil), followed by SMC-supplemented and L. camara-remediated soil(63.33 × 10~6–39.0 × 10~6 CFU g~(-1) soil). Aerial metal uptake ranged from 32.08 ± 0.8 to 5.03 ± 0.08 mg kg~(-1) dry weight, and the bioaccumulation factor ranged from 0.401 to 0.643(P 0.05). Half-lives(t_(1/2)) of Pb were 7.24–2.26 d in supplemented soil,18.39–11.83 d in unsupplemented soil, and 123.75–38.72 d in the soil without plants and organic waste. Freundlich isotherms showed that the intensity of metal absorption(n) ranged from 2.44 to 2.51 for supplemented soil, with regression coefficients of determination(R~2) between 0.901 2 and 0.984 0. The computed free-energy change(?G) for Pb absorption ranged from -5.01 to 0.49 kJ mol~(-1) K~(-1) for EFB-supplemented soil and -3.93 to 0.49 k J mol~(-1) K~(-1) for SMC-supplemented soil.     

华东地区粉煤灰农田模拟试验和放射性分析

对浙江、福建、山东、江西、安徽和江苏 6省部分大型热电厂粉煤灰的采样分析表明 :粉煤灰中主要放射性成分为2 38U、2 32 Th衰变系和4 0 K ,比活度范围分别为 75～2 84Bq kg、60～ 1 64Bq kg和 1 2 0～ 73 8Bq kg。粉煤灰农田施用模拟试验表明 :当施用量达到 52 5t hm2 时 ,土壤中天然放射性核素2 2 6 Ra和2 2 8Ra的比活度分别是对照的 1 88倍和 1 3 9倍 ;生产的食品 (稻谷、玉米籽和麦粒 )中 2种核素的比活度与对照没有明显差异 ,对作物的食用安全性影响不明显     

Distribution of <Superscript>137</Superscript>Cs in the particle-size fractions and in the profiles of alluvial soils on floodplains of the Iput and its tributary Buldynka Rivers (Bryansk oblast)

Pits of sandy alluvial soils were studied in different parts of the floodplains of the Iput River and its tributary the Buldynka River near the settlement of Starye Bobovichi (Bryansk oblast). The ¹³⁷Cs content in the soil horizons varied from 0.01 to 31.2 Bq/g reaching the maximum in the initially polluted layers buried at depths of 6 to 40 cm. Radiocesium was found in all the particle-size fractions with its predominate concentration in the finest fractions. The specific ¹³⁷Cs activity in the fractions of <1, 1–5, 5–10, and >10 μm comprised 44.1 ± 11.5; 33.3 ± 7.6, 20.9 ± 4.9, and 2.4 ± 0.6 Bq/g of soil. However, the contribution of the coarse (>10 μm) fractions to the total radiocesium pool in the soils (19–60%, or 34 ± 2% on the average) was comparable with that of the clay fraction (16–71%, or 38 ± 3% on the average), because of the predominance of the sand-size fractions in the soils. The highest coefficient of variation with respect to the relative contribution of particular fractions to the total soil pool of ¹³⁷Cs was characteristic of the fraction of 5–10 μm; in the other fractions, it varied from 31 to 41%. The portion of ¹³⁷Cs bound with the finest fractions increased in the deeper layers. The total ¹³⁷Cs activity in the polluted horizons of the soils was mainly determined by its concentration in the clay fraction (Spearman’s coefficient of rank correlation (r) for the moderately polluted horizons comprised 0.926 at n = 14). It was experimentally proved that clay particles, upon the destruction of organic films on their surface, could readsorb the released radiocesium for a second time.     

CO2, CH4 and N2O fluxes of upland black spruce (Picea mariana) forest soils after forest fires of different intensity in interior Alaska

Abstract

Forest fires can change the greenhouse gase (GHG) flux of borea forest soils. We measured carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) fluxes with different burn histories in black spruce (Picea mariana) stands in interior Alaska. The control forest (CF) burned in 1920; partially burned (PB) in 1999; and severely burned (SB1 and SB2) in 2004. The thickness of the organic layer was 22 ± 6 cm at CF, 28 ± 10 cm at PB, 12 ± 6 cm at SB1 and 4 ± 2 cm at SB2. The mean soil temperature during CO₂ flux measurement was 8.9 ± 3.1, 6.4 ± 2.1, 5.9 ± 3.4 and 5.0 ± 2.4°C at SB2, SB1, PB and CF, respectively, and differed significantly among the sites (P < 0.01). The mean CO₂ flux was highest at PB (128 ± 85 mg CO₂-C m^?2 h^?1) and lowest at SB1 (47 ± 19 mg CO₂-C m^?2 h^?1) (P < 0.01), and within each site it was positively correlated with soil temperature (P < 0.01). The CO₂ flux at SB2 was lower than that at CF when the soil temperature was high. We attributed the low CO₂ flux at SB1 and SB2 to low root respiration and organic matter decomposition rates due to the 2004 fire. The CH₄ uptake rate was highest at SB1 [–91 ± 21 μg CH₄-C m^?2 h^?1] (P < 0.01) and positively correlated with soil temperature (P < 0.01) but not soil moisture. The CH₄ uptake rate increased with increasing soil temperature because methanotroph activity increased. The N₂O flux was highest [3.6 ± 4.7 μg N₂O-N m^?2 h^?1] at PB (P < 0.01). Our findings suggest that the soil temperature and moisture are important factors of GHG dynamics in forest soils with different fire history.     

Fluxes and production pathways of nitrous oxide in different types of tropical forest soils in Thailand

Nitrous oxide (N₂O) emissions from the soil surface of five different forest types in Thailand were measured using the closed chamber method. Soil samples were also taken to study the N₂O production pathways. The monthly average emissions (±SD, n?=?12) of N₂O from dry evergreen forest (DEF), hill evergreen forest (HEF), moist evergreen forest (MEF), mixed deciduous forest (MDF) and acacia reforestation (ARF) were 13.0?±?8.2, 5.7?±?7.1, 1.2?±?12.1, 7.3?±?8.5 and 16.7?±?9.2?µg N m^?2 h^?1, respectively. Large seasonal variations in fluxes were observed. Emission was relatively higher during the wet season than during the dry season, indicating that soil moisture and denitrification were probably the main controlling factors. Net N₂O uptake was also observed occasionally. Laboratory studies were conducted to further investigate the influence of moisture and the N₂O production pathways. Production rates at 30% water holding capacity (WHC) were 3.9?±?0.2, 0.5?±?0.06 and 0.87?±?0.01?ng N₂O-nitrogen (N) g-dw^?1day^?1 in DEF, HEF and MEF respectively. At 60% WHC, N₂O production rates in DEF, HEF and MEF soils increased by factors of 68, 9 and 502, respectively. Denitrification was found to be the main N₂O production pathway in these soils except in MEF.